# The objective lens and the optical sensor device with lens

The objective lens includes at least two lens elements. The lens elements have an Abbe number equal to 40 or more on the d-line. At least any one of the surfaces is made in the form of an aspherical surface and a numerical aperture of 0.7 or more. The device is an optical sensor includes the specified lens designed for information, in one point of the laser beam emitted from the light source to the surface of the optical recording medium. Provides the objective lens with a sufficiently large numerical aperture, allowing accurate enough to correct chromatic aberration, which can be easily made, and the receiving device of the optical sensor made with the possibility of satisfactory writing and reading of the information signal. 2 S. and 6 C.p. f-crystals, 109 ill., 16 table. The present invention relates to the objective lens and the optical sensor device, which has the objective lens and set to read and write information signal to and from an optical recording medium such as an optical disk, a magneto-optical disk or optical card.Still for storing data information dynamic, the such as optical disks, magneto-optical disks and optical cards, which can easily be manufactured, and the cost is reduced. In recent years, there is a great need to increase the density of information signals that can be recorded, and to increase the storage capacity that is necessary for rapid progress of the information society.An effective means to increase the density of information signals can be recorded on the optical recording medium mentioned type are selecting a lower wavelength laser beam, designed for reading the information signal, and the increase in NA {i.e., using the objective lens having a high NA (numerical aperture)} objective lens to ensure the convergence of the laser beams at a single point in the optical recording medium. The reason for this is that the minimum spot size of the beam, which is obtained by focusing the laser beam cannot be reduced to/NA (the wavelength of the laser beam) or less.To reduce the wavelength of the laser beam have been developed blue laser diode, blue laser with a transform in vtone objective lens for the so-called "digital video disk (DVD)" (digital optical disk, used for video) recording density higher than that of the so-called "compact disc (CD)" (digital optical disk used for the audio signal or computer data), with a value of NA, equal to 0.6 (for comparison, the value NA "compact disc (CD) is 0,45). The objective lens of the optical disk do in the form of a single aspherical lens (monolta aspherical lens), which is made of synthetic resin or glass.To avoid the influence of coma aberration resulting from tilting the digital video disk (DVD)" substrate "digital video disc (DVD) and is manufactured with a thickness of 0.6 mm, which is half the thickness of the substrate "CD" and the thickness of the magneto-optical disk.To further increase the recording density of information signals to be written, as compared with the recording density is realized with the help of digital video disc (DVD) require an objective lens with a NA value more than 0.6.However, for the manufacture of the objective lens with a NA value is not less than 0.7 should be satisfied different requirements.The lack of objective lens with high NA is chromatic aberration, which occurs randomly when izmeneniia environment). As known monolta the objective lens has an NA value not exceeding 0,6, in which chromatic aberration is formed slightly, the lens of the aforementioned type can be made of optical glass, the Abbe number of 50 or less, and which therefore has a relatively high dispersion and high refractive ability. As the cost of optical glass having a high scattering and the frequency can be reduced, the above optical glass may satisfy the requirements of mass production. So it is widely used above the material.However, the objective lens with high NA type that have a value of NA of 0.7 or higher, have a high chromatic aberration, if the above-mentioned objective lens is made of optical glass with a high scattering. In this case, there is a strong fussing on the surface of the optical disk on which is recorded a signal. Therefore, chromatic aberration must be eliminated by the use of glass with low dispersion.Since much of the optical glass of low dispersion has a low refractive index, the curvature of the surface is excessively large, if online lenses cannot easily be manufactured on the machine. This level of machining of aspheric surfaces is not possible to accurately manufacture the mold using a diamond tool, if angleformed between the contact surface is an aspherical surface and a plane perpendicular to the optical axis, is more than 50 degrees (it is known that good lenses are obtained when the angleapproximately 55 degrees or less).However, the objective lens having a short focal length and high NA, usually constructed so as to have the above-mentioned anglemore than 55 degrees. In this case, in the manufacture of the mold or lens is significantly reduced allowable dezentrale distance between the two sides of the lens. Thus, the efficiency of manufacture is greatly reduced.Therefore, you can consider using a doublet lens structure for distribution of curvature on four surfaces. However, even in the lens of the doublet, which try to maintain a sufficiently large working distance, has a surface with an extremely small radius of curvature. Moreover, in the manufacture of lenses will mind what about decreasing the efficiency of production. Reducing the aperture of the lens, i.e. the diameter of the objective lens is an important factor, because such a reduction reduces the size of the optical sensor and to obtain, thus, the economic benefit. Maintaining a sufficiently long working distance is an important factor for preventing contact between the objective lens and the optical disk, which rotates at high speed.Therefore, the doublet lens element of the lens must contain a lens with a small curvature of the surface, which can be produced without reducing the effectiveness.Although the objective lens can be done with a small curvature, and thus to increase the efficiency of manufacture of the lens, if the aperture of the objective lens increases, the weight of the part, including the objective lens, also increases. In this case, it is impossible to reduce the device size of the optical sensor. In addition, there should be improved actuator (mechanism of management by objective lens), which moves the objective lens followed by the optical drive. In this case, it is impossible to reduce the size and cost of the device is an optical sensor.If you are using a lens with a high NA, there is another problem, zakljuchaetsja signal from the optical disk due to coma aberration, which occurs randomly when the misalignment of the optical disc and increases proportionally to the cube of the NA.Given the above, the present invention is to obtain objective lens with a sufficiently large numerical aperture NA, which allows accurate enough to correct chromatic aberration, and which can be easily made.Another objective of the present invention is to develop a device of the optical sensor having the objective lens according to the present invention and placed with the possibility of satisfactory writing and reading an information signal in and from the optical recording medium.To accomplish the above objectives, the present invention has such a construction that the chromatic aberration of the lens-barrel, which has a high NA (numerical aperture), is eliminated by using the optical glass of low dispersion having an Abbe number of 40 or more, and suitable for the manufacture of two elements. To reduce the diameter of the aperture or to obtain a sufficiently large working distance, the first means is set so that the lens having a lower radius of curvature is made of optisage for the manufacture of lenses, with a higher radius of curvature. Thus, it is possible to get a higher radius of curvature and to avoid a decrease in the efficiency of manufacture. Since the optical glass used for production of lenses with a lower radius of curvature, has in this case a large scattering wavelength, this disadvantage is partly compensated for using the chromatic aberration correction. The second tool is placed so as to limit the diameter of the aperture is 4.5 mm or less in order to reduce the aperture size of the optical sensor device. When using aperture with a value of 4.5 mm or less, the preferred region for NA (numerical aperture), the diameter of the aperture and working distance is limited to prevent a large curvature. Thus, it is possible to prevent reduction in the efficiency of manufacture. The above lenses have a curved surface, the inclination (deviation) and the permissible decentrally that satisfy the ranges of values within which it is possible to make the lens. Thus obtained lens can have optimal power distribution refracted light for the two lens elements of the lens doublet. The power distribution of prelomlyayushchie, if the relation F

_{1}/F of the focal length F

_{1}lens element, located near the object (located near the light source) to the focal length F of the entire system of lens elements satisfy the following relations: 1,7<(F

/F)<a 2.5.According to the first aspect of the present invention is executed, the objective lens comprising two lens elements made of optical glass with an Abbe number of 40 or more on the d-line and with the structure of the doublet, in which at least any one of the surfaces is made in the form of an aspherical surface and a numerical aperture of 0.7 or more.The device is an optical sensor according to the present invention has such a construction, in which the Abbe number of the optical glass is made of two lens element at the d-line is 60 or more and numeric Aper is m, the refractive index of the optical glass is made of one of the lens elements, in which the angle formed between the tangential plane in the plane of the periphery of the lens element and the plane perpendicular to the optical axis, is greater than the corresponding angle in the other lens element is

_{1}and the refractive index of optical glass, which made the other lens element is n_{1}if this is true the following relationship: n_{1}>n_{2}.The objective lens according to the present invention has such a structure in which, provided that the diameter of the incident laser beam BW, the working distance WD, and numerical aperture NA, just following relations: if 1,0BW<4,5, 0,05WD and 0.7NA <0.8, then WD0/25676BW + 0,039189 if 0,8NA<0,9, WD0/14054BW-0,064865, and if 0,9NA, WD0,096429 BW-0,244640.The objective lens according to the present invention has such a structure that the relation F_{1}/F of the focal length F_{1}the lens element located on the side usamu value: 1,7<(F/F)<a 2.5.

Fig. 1 depicts a vertical cross-section showing the device of the optical sensor according to the present invention, made of optical glass having an Abbe number of 50 or less;

Fig.2 depicts a graph showing the distortion of the lens (Fig.1);

Fig. 3 depicts a graph showing astigmatism of the objective lens (Fig. 1);

Fig. 4 depicts a graph showing the spherical aberration of the objective lens (Fig.1);

Fig. 5 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees) of the lens (Fig.1);

Fig. 6 depicts a graph showing the lateral aberration (axis) of the lens (Fig.1);

Fig. 7 depicts a graph showing the MTF (modulation transfer function) of the lens (Fig.1);

Fig.8 depicts a graph showing the PSF of Linz lens according to the present invention, with a higher curvature;

Fig. 10 depicts a graph showing the distortion of the lens (Fig. 9);

Fig.11 depicts a graph showing astigmatism of the objective lens (Fig. 9);

Fig. 12 depicts a graph showing the spherical aberration of the objective lens (Fig.9);

Fig. 13 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees) of the lens (Fig.9);

Fig. 14 depicts a graph showing the lateral aberration (on the axis) of the lens (Fig.9);

Fig.15 depicts a vertical cross section showing the structure of the design, showing the upper limit of the objective lens according to the present invention;

Fig. 16 depicts a graph showing the distortion of the lens (Fig. 15);

Fig.17 depicts a graph showing astigmatism of the objective lens (Fig. 15);

Fig. 18 depicts a graph showing the spherical aberration of the objective lens (Fig.15);

Fig. 19 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees) of the lens (Fig.15);

Fig. 20 depicts a graph showing the lateral aberration (on the axis) of the lens (Fig.15);

Fig. 21 depicts a graph showing the jump fashion in a single-mode laser diode;

Fig. 22 depicts the

Fig. 23 depicts a graph showing the preferred field direction of the beam, the working distance and NA (if NA = 0,8);

Fig. 24 depicts a graph showing the preferred field direction of the beam, the working distance and NA (if NA = 0,9);

Fig. 25 depicts a graph showing the size distribution of dust on the optical disk;

Fig.26 depicts a histogram of the relations F

Fig. 27 depicts a graph showing the wave surface of the beam spot, with the misalignment of the DVD (digital video disc) is equal to 0.4 degrees;

Fig.28 depicts a graph showing the thickness of the substrate of the optical disk, which creates a wavefront aberration, similar aberrations (Fig. 27);

Fig.29 depicts a side view showing the main part of the optical sensor device according to the present invention;

Fig. 30 depicts a side view showing the main part of the structure of the first variant implementation of the objective lens according to the present invention;

Fig. 31 depicts a graph showing the distortion of the lens (Fig. 30);

Fig.32 depicts a graph showing the Asti is willow (Fig.30);

Fig. 34 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees) of the lens (Fig.30);

Fig. 35 depicts a graph showing the lateral aberration (on the axis) of the lens (Fig.30);

Fig. 36 depicts a graph showing the MTF (modulation transfer function) of the lens (Fig.30);

Fig. 37 depicts a graph showing the (modulation transfer function) of the lens (Fig.30);

Fig. 38 depicts a vertical cross section showing the structure of the second variant of realization of the objective lens according to the present invention;

Fig. 39 depicts a graph showing the distortion of the lens (Fig. 38);

Fig.40 depicts a graph showing astigmatism of the objective lens (Fig. 38);

Fig. 41 depicts a graph showing the spherical aberration of the objective lens (Fig.38);

Fig. 42 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees) of the lens (Fig.38);

Fig. 43 depicts a graph showing the lateral aberration (on the axis) of the lens (Fig.38);

Fig. 44 depicts a vertical cross section showing the structure of the third variant of the implementation of the objective lens according to the present invention;

Fig. 45 depicts Ginza lens (Fig. 44);

Fig. 47 depicts a graph showing the spherical aberration of the objective lens (Fig.44);

Fig. 48 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees) of the lens (Fig.44);

Fig. 49 depicts a graph showing the lateral aberration (on the axis) of the lens (Fig.44);

Fig. 50 depicts a vertical cross section showing the structure of a fourth variant of the implementation of the objective lens according to the present invention;

Fig. 51 depicts a graph showing the distortion of the lens (Fig. 50);

Fig.52 depicts a graph showing astigmatism of the objective lens (Fig. 50);

Fig. 53 depicts a graph showing the spherical aberration of the objective lens (Fig.50);

Fig. 54 depicts a graph showing the lateral aberration(angle of vision 0.5 degrees) of the lens (Fig.50);

Fig. 55 depicts a graph showing the lateral aberration (on the axis) of the lens (Fig.50);

Fig. 56 depicts a vertical cross section showing the structure of a fifth variant of the implementation of the objective lens according to the present invention;

Fig. 57 depicts a graph showing the distortion of the lens (Fig. 56);

Fig.58 depicts a graph showing the astigmatism lenses/> Fig. 60 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees) of the lens (Fig.56);

Fig. 61 depicts a graph showing the lateral aberration (on the axis) of the lens (Fig.56);

Fig. 62 depicts a vertical cross section showing the structure of a sixth variant of the implementation of the objective lens according to the present invention;

Fig. 63 depicts a graph showing the distortion of the lens (Fig. 62);

Fig.64 depicts a graph showing astigmatism of the objective lens (Fig. 62);

Fig. 65 depicts a graph showing the spherical aberration of the objective lens (Fig.62);

Fig. 66 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees) of the lens (Fig.62);

Fig. 67 depicts a graph showing the lateral aberration (on the axis) of the lens (Fig.62);

Fig. 68 depicts a vertical cross section showing the structure of a seventh variant of the implementation of the objective lens according to the present invention;

Fig. 69 depicts a graph showing the distortion of the lens (Fig. 68);

Fig.70 depicts a graph showing astigmatism of the objective lens (Fig. 68);

Fig. 71 depicts a graph showing the spherical aberration of the objective lens (Fig.68);

Fig. 73 depicts a graph showing the lateral aberration (on the axis) of the lens (Fig.68);

Fig. 74 depicts a vertical cross section showing the structure of an eighth variant of the implementation of the objective lens according to the present invention;

Fig. 75 depicts a graph showing the distortion of the lens (Fig. 74);

Fig.76 depicts a graph showing astigmatism of the objective lens (Fig. 74);

Fig. 77 depicts a graph showing the spherical aberration of the objective lens (Fig.74);

Fig. 78 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees) of the lens (Fig.74);

Fig. 79 depicts a graph showing the lateral aberration (on the axis) of the lens (Fig.74);

Fig. 80 depicts a vertical cross section showing the structure of a ninth variant of the implementation of the objective lens according to the present invention;

Fig. 81 depicts a graph showing the distortion of the lens (Fig. 80);

Fig.82 depicts a graph showing astigmatism of the objective lens (Fig. 80);

Fig. 83 depicts a graph showing the spherical aberration of the objective lens (Fig.80);

Fig. 84 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees) lens objetos. 86 depicts a vertical cross section showing the structure of the tenth variant embodiment of the invention according to the present invention;

Fig. 87 depicts a graph showing the distortion of the lens (Fig. 86);

Fig.88 depicts a graph showing astigmatism of the objective lens (Fig. 86);

Fig. 89 depicts a graph showing the spherical aberration of the objective lens (Fig.86);

Fig. 90 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees) of the lens (Fig.86);

Fig. 91 depicts a graph showing the lateral aberration (on the axis) of the lens (Fig.86);

Fig. 92 depicts a vertical cross section showing the structure of an eleventh variant of the implementation of the objective lens according to the present invention;

Fig. 93 depicts a graph showing the distortion of the lens (Fig. 92);

Fig.94 depicts a graph showing astigmatism of the objective lens (Fig. 92);

Fig. 95 depicts a graph showing the spherical aberration of the objective lens (Fig.92);

Fig. 96 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees) of the lens (Fig.92);

Fig. 97 depicts a graph showing the lateral aberration (on the axis) of the lens object is the implementation of the objective lens according to the present invention;

Fig. 99 depicts a graph showing the distortion of the lens (Fig. 98);

Fig. 100 depicts a graph showing astigmatism of the objective lens (Fig.98);

Fig. 101 depicts a graph showing the spherical aberration of the objective lens (Fig.98);

Fig. 102 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees) of the lens (Fig.98);

Fig.103 depicts a graph showing the lateral aberration (on the axis) of the lens (Fig.98);

Fig. 104 depicts a vertical cross section showing the structure of the thirteenth variant implementation of the objective lens according to the present invention;

Fig. 105 depicts a graph showing the distortion of the lens (Fig. 104);

Fig. 106 depicts a graph showing astigmatism of the objective lens (Fig.104);

Fig. 107 depicts a graph showing the spherical aberration of the objective lens (Fig.104);

Fig. 108 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees) of the lens (Fig.104); and

Fig.109 depicts a graph showing the lateral aberration (on the axis) of the lens (Fig.104).The following describes embodiments of the present invention with reference to the drawings in the following order.1. Schematic to the meet the Abbe number vd of at least 40 (vd40) on the d-line as optical glass two elements.3. Lens, satisfying the condition of n

if 1,0BW<4,5, 0,05WD and 0.7NA (numerical aperture) <0.8, then

WD0,25676 BW + 0,039189,

if 0,8NA0,9,

WD0,14054 BW-0,064865, and

if 0,9NA,

WD0,096429 BW-0,244640

4-1. The upper limit of the diameter of the beam

4-2. The lower limit of the working distance

4-3. The upper limit of the working distance

5. Lens, in which the ratio (FNA (numerical aperture)<0.8, then T0.32 mm, if 0,8NA<0,9, T0.20 mm, and if 0,9NA, T0,11 mm

According to another aspect of the present invention completed unit of the optical sensor according to the present invention containing the light source and the objective lens, designed for information, in one point of the laser beam emitted from the light source on the recording surface of the optical signal recording medium in which the lens has two lens elements made of optical glass with an Abbe number of 40 or more on the d-line and having the structure of the doublet, and at least every surface made in the form of an aspherical surface and a numerical aperture faced the Abbe d-line optical glass, made of two lens element is 60 or more and a numerical aperture of 0.8 or more.Other objectives, features and advantages of the invention will be apparent from the following detailed description of preferred embodiments, are described together with the attached drawings.The invention is illustrated by reference to the accompanying drawings, in which:Fig. 1 depicts a vertical cross-section showing the device of the optical sensor according to the present invention, made of optical glass having an Abbe number of 50 or less;

Fig.2 depicts a graph showing the distortion of the lens (Fig.1);

Fig. 3 depicts a graph showing astigmatism of the objective lens (Fig. 1);

Fig. 4 depicts a graph showing the spherical aberration of the objective lens (Fig.1);

Fig. 5 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees) of the lens (Fig.1);

Fig. 6 depicts a graph showing the lateral aberration (axis) of the lens (Fig.1);

Fig. 7 depicts a graph showing the MTF (modulation transfer function) of the lens (Fig.1);

Fig.8 depicts a graph showing the PSF of Linz lens according to the present invention, with a higher curvature;

Fig. 10 depicts a graph showing the distortion of the lens (Fig. 9);

Fig.11 depicts a graph showing astigmatism of the objective lens (Fig. 9);

Fig. 12 depicts a graph showing the spherical aberration of the objective lens (Fig.9);

Fig. 13 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees) of the lens (Fig.9);

Fig. 14 depicts a graph showing the lateral aberration (on the axis) of the lens (Fig.9);

Fig.15 depicts a vertical cross section showing the structure of the design, showing the upper limit of the objective lens according to the present invention;

Fig. 16 depicts a graph showing the distortion of the lens (Fig. 15);

Fig.17 depicts a graph showing astigmatism of the objective lens (Fig. 15);

Fig. 18 depicts a graph showing the spherical aberration of the objective lens (Fig.15);

Fig. 19 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees) of the lens (Fig.15);

Fig. 20 depicts a graph showing the lateral aberration (on the axis) of the lens (Fig.15);

Fig. 21 depicts a graph showing the jump fashion in a single-mode laser diode;

Fig. 22 depicts the

Fig. 23 depicts a graph showing the preferred field direction of the beam, the working distance and NA (if NA = 0,8);

Fig. 24 depicts a graph showing the preferred field direction of the beam, the working distance and NA (if NA = 0,9);

Fig. 25 depicts a graph showing the size distribution of dust on the optical disk;

Fig.26 depicts a histogram of the relations F

_{1}/F of the focal length in the sample design, in which access to the structure is big enough;Fig. 27 depicts a graph showing the wave surface of the beam spot, with the misalignment of the DVD (digital video disc) is equal to 0.4 degrees;

Fig.28 depicts a graph showing the thickness of the substrate of the optical disk, which creates a wavefront aberration, similar aberrations (Fig. 27);

Fig.29 depicts a side view showing the main part of the optical sensor device according to the present invention;

Fig. 30 depicts a side view showing the main part of the structure of the first variant implementation of the objective lens according to the present invention;

Fig. 31 depicts a graph showing the distortion of the lens (Fig. 30);

Fig.32 depicts a graph showing the Asti is willow (Fig.30);

Fig. 34 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees) of the lens (Fig.30);

Fig. 35 depicts a graph showing the lateral aberration (on the axis) of the lens (Fig.30);

Fig. 36 depicts a graph showing the MTF (modulation transfer function) of the lens (Fig.30);

Fig. 37 depicts a graph showing the (modulation transfer function) of the lens (Fig.30);

Fig. 38 depicts a vertical cross section showing the structure of the second variant of realization of the objective lens according to the present invention;

Fig. 39 depicts a graph showing the distortion of the lens (Fig. 38);

Fig.40 depicts a graph showing astigmatism of the objective lens (Fig. 38);

Fig. 41 depicts a graph showing the spherical aberration of the objective lens (Fig.38);

Fig. 42 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees) of the lens (Fig.38);

Fig. 43 depicts a graph showing the lateral aberration (on the axis) of the lens (Fig.38);

Fig. 44 depicts a vertical cross section showing the structure of the third variant of the implementation of the objective lens according to the present invention;

Fig. 45 depicts Ginza lens (Fig. 44);

Fig. 47 depicts a graph showing the spherical aberration of the objective lens (Fig.44);

Fig. 48 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees) of the lens (Fig.44);

Fig. 49 depicts a graph showing the lateral aberration (on the axis) of the lens (Fig.44);

Fig. 50 depicts a vertical cross section showing the structure of a fourth variant of the implementation of the objective lens according to the present invention;

Fig. 51 depicts a graph showing the distortion of the lens (Fig. 50);

Fig.52 depicts a graph showing astigmatism of the objective lens (Fig. 50);

Fig. 53 depicts a graph showing the spherical aberration of the objective lens (Fig.50);

Fig. 54 depicts a graph showing the lateral aberration(angle of vision 0.5 degrees) of the lens (Fig.50);

Fig. 55 depicts a graph showing the lateral aberration (on the axis) of the lens (Fig.50);

Fig. 56 depicts a vertical cross section showing the structure of a fifth variant of the implementation of the objective lens according to the present invention;

Fig. 57 depicts a graph showing the distortion of the lens (Fig. 56);

Fig.58 depicts a graph showing the astigmatism lenses/> Fig. 60 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees) of the lens (Fig.56);

Fig. 61 depicts a graph showing the lateral aberration (on the axis) of the lens (Fig.56);

Fig. 62 depicts a vertical cross section showing the structure of a sixth variant of the implementation of the objective lens according to the present invention;

Fig. 63 depicts a graph showing the distortion of the lens (Fig. 62);

Fig.64 depicts a graph showing astigmatism of the objective lens (Fig. 62);

Fig. 65 depicts a graph showing the spherical aberration of the objective lens (Fig.62);

Fig. 66 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees) of the lens (Fig.62);

Fig. 67 depicts a graph showing the lateral aberration (on the axis) of the lens (Fig.62);

Fig. 68 depicts a vertical cross section showing the structure of a seventh variant of the implementation of the objective lens according to the present invention;

Fig. 69 depicts a graph showing the distortion of the lens (Fig. 68);

Fig.70 depicts a graph showing astigmatism of the objective lens (Fig. 68);

Fig. 71 depicts a graph showing the spherical aberration of the objective lens (Fig.68);

Fig. 73 depicts a graph showing the lateral aberration (on the axis) of the lens (Fig.68);

Fig. 74 depicts a vertical cross section showing the structure of an eighth variant of the implementation of the objective lens according to the present invention;

Fig. 75 depicts a graph showing the distortion of the lens (Fig. 74);

Fig.76 depicts a graph showing astigmatism of the objective lens (Fig. 74);

Fig. 77 depicts a graph showing the spherical aberration of the objective lens (Fig.74);

Fig. 78 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees) of the lens (Fig.74);

Fig. 79 depicts a graph showing the lateral aberration (on the axis) of the lens (Fig.74);

Fig. 80 depicts a vertical cross section showing the structure of a ninth variant of the implementation of the objective lens according to the present invention;

Fig. 81 depicts a graph showing the distortion of the lens (Fig. 80);

Fig.82 depicts a graph showing astigmatism of the objective lens (Fig. 80);

Fig. 83 depicts a graph showing the spherical aberration of the objective lens (Fig.80);

Fig. 84 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees) lens objetos. 86 depicts a vertical cross section showing the structure of the tenth variant embodiment of the invention according to the present invention;

Fig. 87 depicts a graph showing the distortion of the lens (Fig. 86);

Fig.88 depicts a graph showing astigmatism of the objective lens (Fig. 86);

Fig. 89 depicts a graph showing the spherical aberration of the objective lens (Fig.86);

Fig. 90 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees) of the lens (Fig.86);

Fig. 91 depicts a graph showing the lateral aberration (on the axis) of the lens (Fig.86);

Fig. 92 depicts a vertical cross section showing the structure of an eleventh variant of the implementation of the objective lens according to the present invention;

Fig. 93 depicts a graph showing the distortion of the lens (Fig. 92);

Fig.94 depicts a graph showing astigmatism of the objective lens (Fig. 92);

Fig. 95 depicts a graph showing the spherical aberration of the objective lens (Fig.92);

Fig. 96 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees) of the lens (Fig.92);

Fig. 97 depicts a graph showing the lateral aberration (on the axis) of the lens object is the implementation of the objective lens according to the present invention;

Fig. 99 depicts a graph showing the distortion of the lens (Fig. 98);

Fig. 100 depicts a graph showing astigmatism of the objective lens (Fig.98);

Fig. 101 depicts a graph showing the spherical aberration of the objective lens (Fig.98);

Fig. 102 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees) of the lens (Fig.98);

Fig.103 depicts a graph showing the lateral aberration (on the axis) of the lens (Fig.98);

Fig. 104 depicts a vertical cross section showing the structure of the thirteenth variant implementation of the objective lens according to the present invention;

Fig. 105 depicts a graph showing the distortion of the lens (Fig. 104);

Fig. 106 depicts a graph showing astigmatism of the objective lens (Fig.104);

Fig. 107 depicts a graph showing the spherical aberration of the objective lens (Fig.104);

Fig. 108 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees) of the lens (Fig.104); and

Fig.109 depicts a graph showing the lateral aberration (on the axis) of the lens (Fig.104).The following describes embodiments of the present invention with reference to the drawings in the following order.1. Schematic to the meet the Abbe number vd of at least 40 (vd40) on the d-line as optical glass two elements.3. Lens, satisfying the condition of n

_{1}>n_{2}assuming that n_{1}the refractive index of the lens with a lower radius of curvature and n_{2}the refractive index of the lens with a higher radius of curvature.4. The lens diameter of the beam BW and working distance WD has the following limitations:if 1,0BW<4,5, 0,05WD and 0.7NA (numerical aperture) <0.8, then

WD0,25676 BW + 0,039189,

if 0,8NA0,9,

WD0,14054 BW-0,064865, and

if 0,9NA,

WD0,096429 BW-0,244640

4-1. The upper limit of the diameter of the beam

4-2. The lower limit of the working distance

4-3. The upper limit of the working distance

5. Lens, in which the ratio (F

_{1}/F) focal length F_{1}the lens near the object (located near the light source), and the focal length F of the entire system satisfies the condition of 1.7<(F/F)<a 2.5.

1. Schematic design of the lens

The objective lens according to the present invention is a doublet lens (two elements in two groups), with at least each side, made on a spherical surface, as shown in Fig.1 and table 1, the objective lens according to the present invention has a high NA (numerical aperture) objective lens with an NA equal to 0.7 or more. That is, the objective lens according to the present invention includes the first lens 3 located near the object (light source) and a second lens 4 located next to the image (optical recording medium). Parallel flat plate 5 corresponding to the transparency of the optical recording medium, is performed for the objective lens according to the present invention in position next to the image.The objective lens according to the present invention is a so-called lens with infinite the certain distance. The light beam which emerges from a point of the object is formed into a parallel beam, and then, passing through the aperture (STO) 2 so that the laser beam incident angle on the first surface of S

if 1,0BW<4,5, 0,05WD and 0.7NA (numerical aperture)<0.8, then

WD0,25676 BW + 0,039189,

if 0,8NA<0,9,

WD0,14054 BW-0,064865, and

if 0,9NA,

WD0,096429 BW-0,244640.In the doublet lens is designed for an optical recording medium such as an optical disk, it is required to have a lower aperture (short focal length) in order to reduce the size and cost of the device is an optical sensor. Since the objective lens according to the present invention consists of two lens elements, reducing the aperture size is an important fact. The reason for this is that compared to a single-element lens, the weight of the above-mentioned lenses, uvelichenie is standing WD undesirable reduced. In practice, sometimes you cannot perform the required reduction, because to prevent contact between the objective lens and dust located on the surface of the optical recording medium, it is necessary to ensure the working distance at least equal to 50 μm. If there is a satisfactory long working distance, it significantly increases the quality of the correction of spherical aberration. In this case, the coefficient of asphericity increases and the radius of curvature of the surface decreases rapidly. This reduces the efficiency of manufacture.The limit of the aperture has different values depending on the values of NA and working distance. This is because the amount of correction of spherical aberration changes depending on the NA of the lens.From the point of view of designing and manufacturing lenses, you can easily produce a lens having improved characteristics in the case where the aperture is large.So below, with reference to Fig.22-24, describes many of the values of the diameter of the beam, the working distance (WD) and NA, suitable for the manufacture of lenses of the doublet.4-1. The upper limit of the diameter of the beam

The upper limit of the diameter of the beam is determined by the point A, the second sensor, the weight of the lens and frame for the lenses (lens holder) increase. In this case, actuator performing focusing with the servo should have a higher performance, disadvantageous from an economic point of view.For example, the objective lens (Fig.15), having an effective beam diameter of 4.5 mm and containing two lens element, has a great weight to about 250 mg. Weight of the lens, adapted for CD (compact disk) or DVD (digital video disc) is

about 200 mg, including the body of the lens. Because of the ratio type f=k/2m (where m is the mass, k is the elastic constant and f is the resonant frequency) satisfies the occasion of the work of the two-axis actuator, the value of f increases inversely proportional to the weight of the lens, preferable to control the servo, so the value of f is chosen outside the resonant frequency of the servo focus. If you prefer the full weight of the lens, including weight housing lens, 500 mg or less, the lens having a weight of 500 mg or less, including weight housing lens, not easy to construct, because the lens is heavier than the lens, which has an effective diameter of 4.5 mm (Fig. 15) and a weight of 250 mg. In this case, a two-axis actuators. Therefore, it is preferable that the effective diameter of the doublet was 4.5 mm or less.In Fig. 15 and table 3 presents design data of the lens. In Fig.16 depicts a graph showing the distortion of the above-mentioned objective lens, Fig.17 shows the astigmatism of the same objective lens, and Fig.18 shows the spherical aberration of the same objective lens. In Fig. 19 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees), and Fig.20 depicts a graph showing the lateral aberration (on the axis).4-2. The lower limit of the working distance

In Fig. 22-24 point is depicted In the lower limit of the working distance WD. Since the amount of correction of spherical aberration can be reduced in proportion to the working distance, it is possible to easily manufacture the lens. From the point of view of practical use, it is necessary to maintain a certain working distance to avoid a collision between the objective lens and the optical recording medium, for example, an optical disk, which rotates at high speed, when the focus adjustment, or contact between the dust on the surface of the optical recording medium and the objective lens, when nachinaet environment, which is contained in the environment space, usually 50 μm or less (Fig.25). Therefore, the working distance should be 50 μm or more.4-3. The upper limit of the working distance

The magnitude of the spherical aberration that can be corrected using lenses of the doublet within a certain value NA and beam diameter depends on the working distance. In the present invention proposed the construction of various lenses taking into account the curvature (angleis 55 degrees or more) allowable misalignment10 μm or more) and the allowable angle of vision (1 degree or more). Examples of the upper limit of the working distance that implement the above valid region, shown by points 1-9 in Fig.22-24. If the working distance exceeds the above upper limit, the spherical aberration is greatly increased and, thus, significantly reduces the radius of curvature of the lens. So, if it turns out such a structure, in which the working distance is not included in the area shown by diagonal lines in Fig.22-24, the lens cannot be made easily or use with an optical recording medium. Preferred about the de:

if 1,0BW<4,5, 0,05WD and 0.7NA<0.8, then WD0,25676 BW + 0,039189 (see Fig.22),

if 0,8NA<0,9, WD0,14054 BW-0,064865 (see Fig.23),

if 0,9NA, WD0,096429 BW-0,244640 (see Fig.24).Valid dezentrale (10 μm or more) is a value that is determined by the accuracy of manufacturing, for example, during injection molding using a mold. Permissible angle of vision (1 degree or more) is set to a value, which is determined by the accuracy of the inclination of the lens barrel about the optical axis.Objective lens (Fig. 22-24) satisfying the above conditions will be described as follows: the objective lens corresponding to point 2 (Fig. 22), will be described in the eighth embodiment, the objective lens corresponding to point 3 (Fig. 22), will be described in the ninth embodiment, and the objective lens corresponding to point 9 (Fig.24) will be described in the tenth embodiment.5. Lens, for which the ratio (F T0.32 mm,

if 0,8NA<0,9,

T0.20 mm, and

if 0,9NA,

T0,11 mm

1. Schematic design of the lens

The objective lens according to the present invention is a doublet lens (two elements in two groups), with at least each side, made on a spherical surface, as shown in Fig.1 and table 1, the objective lens according to the present invention has a high NA (numerical aperture) objective lens with an NA equal to 0.7 or more. That is, the objective lens according to the present invention includes the first lens 3 located near the object (light source) and a second lens 4 located next to the image (optical recording medium). Parallel flat plate 5 corresponding to the transparency of the optical recording medium, is performed for the objective lens according to the present invention in position next to the image.The objective lens according to the present invention is a so-called lens with infinite the certain distance. The light beam which emerges from a point of the object is formed into a parallel beam, and then, passing through the aperture (STO) 2 so that the laser beam incident angle on the first surface of S

_{1}(the surface of the fall of the first lens 3). The laser beam then emerges from the second surface S_{2}(the radiating surface of the first lens 3), and then falls on the third surface S_{3}(the surface of the fall of the second lens 4). The laser beam then exits from the fourth surface S_{4}(the radiating surface of the second lens 4 and then falls on the fifth surface S_{5}(the surface of incidence of the parallel flat plate 5). The laser beam then forms an image at the point in the image (img) on the sixth surface S_{6}(the radiating surface of the parallel flat plate 5).In Fig.2 depicts a graph showing the distortion of the objective lens according to the present invention, Fig.3 depicts a graph showing astigmatism of the same objective lens, Fig.4 depicts a graph showing the spherical aberration of the same objective lens. In Fig.5 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees), and Fig. 6 depicts a graph showing the lateral aberration (Eney 40 (vd40) on the d-line as optical glass two elements.Since the objective lens according to the present invention responds to the change in wavelength of a semiconductor laser which is the light source, because the objective lens according to the present invention has a high NA, it is necessary to perform the correction of chromatic aberration. Chromatic aberration is an aberration that occurs due to the fact that the refractive index of optical glass varies with wavelength of light. The position and size of the image become different depending on the wavelength.As a well-known objective lens with low NA, designed for use in optical disks, such as the well known CD(compact disk) or a laser printer that does not create a large chromatic aberration, it is widely used optical glass (Abbe number less than 40). The reason for this is that the above optical glass can be easily made and thus to issue mass production.However, the lens system has a higher capacity of refracted light that is proportional to NA, and thus, there is a random Obamamania wavelength. In addition, chromatic aberration occurs largely in systems having a large focal length.On the other hand, in semiconductor lasers found skipping fashion (Fig. 21), depending on the temperature change of the laser diode, and thus rapidly changing the output wavelength. If chromatic aberration occurs in the objective lens, the defocusing occurring randomly at the jump mod, can't follow and to move beyond the two-axis actuator used to move the objective lens.Accordingly, the lens must be made of optical glass with low dispersion to prevent chromatic abberly. The objective lens (Fig.1 and table 1), performed as described above, includes the first and second lenses 3 and 4, each of which has an Abbe number vd, equal to 40.5, and the refractive index of 1.73. When the magnitude of the holes is limited by the diaphragm 2, fussing, associated with a change in wavelength of a semiconductor laser of 0.5 nm is 0,478 μm in NA, is equal to 0.8.In Fig. 7 depicts the MTF (modulation transfer function) in the direction of the optical axis in the case when the spatial frequency of the SOS is to them NA, adapted for an optical disc, which serves as an optical recording medium, creates focus more 0,496 μm, which is half of the focal depth 0,992 nm when the wavelength of the semiconductor laser is changed to P-P10 nm (5 nm), the spot from the beam incident on the surface of the recording signal from an optical disc, it is impossible to completely stop down any. When the wavelength is changed to P-P10 nm (5 nm), the lens is made of optical glass (Fig.1) with the Abbe number vd, equal to 40.5, creates a defocusing value (0.475) μm, which is essentially valid fussing. Therefore, the present invention is made so that the lower limit of correct Abbe number vd of optical glass, which made the lens was 40 to prevent chromatic abberly. Preferably, the upper limit of the Abbe number vd was of great importance to prevent chromatic abberly. Therefore, to effectively prevent chromatic abberly the present invention is made so that the range of values for the Abbe number vd of optical glass, intended for the manufacture of a lens having NA of 0.7 or more, 40 or more is certain of optical glass having a large Abbe number (vd = 61,3). In this case, chromatic aberration can be prevented even if the increased focal length or NA.3. Lens, satisfying the condition of n_{1}>n_{2}assuming that the refractive index of the lens with a higher curvature equal to n_{1}and the refractive index of the lens having a lower curvature, is n_{2}.Even if chromatic aberacia prevented by using the above optical glass of low dispersion, there are the following problems: the curvature of the lens is significantly increased in the manufacture of lenses, if you use optical glass of low dispersion having a low refractive index, because it requires a large value of refractive index for optical glass, from which is made the objective lens having a high NA. In this case, to increase the refractive index and securing the lower curvature of the optical glass must be replaced.However, in this case, the reduced scattering of the available optical glass. Therefore, the two lenses should be made of optical glass having an Abbe number of 40 or more. If lean manufacturing is PS with high curvature is used for optical glass, having a lower Abbe value (but not less than 40), you can prevent more significant distortion chromatic abberly.The state in which the curvature of the lens is too high for its production, is a condition in which the angleformed between the tangent (tangent plane) of the lens surface at the position at which it falls laser beam, which has the largest height among the incident laser beams, and the normal (plane perpendicular to the optical axis) to the optical axis exceeds 55 degrees (65 degrees in the case shown in Fig.9) on the surface (plane S3 in the case shown in Fig.9) having the highest curvature (Fig.9). In this case, it is impossible to fabricate the mold for manufacturing the above-mentioned lenses. Estimated value of the lens (Fig.9) are presented in table 2.In Fig.10 depicts a graph showing the distortion of the above-mentioned objective lens, Fig.11 shows the astigmatism of the same objective lens, and Fig. 12 shows spherical aberration of the same objective lens. In Fig. 13 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees), and Fig. 14 depicts a graph p is apaseo, where it is possible to make a lens with a satisfactory prevent chromatic aberration to improve the efficiency of manufacturing lenses.The objective lens is made as described above will be described in the second embodiment.4. Lens having a beam diameter of BW and the working distance WD is limited by the following relations:if 1,0BW<4,5, 0,05WD and 0.7NA (numerical aperture)<0.8, then

WD0,25676 BW + 0,039189,

if 0,8NA<0,9,

WD0,14054 BW-0,064865, and

if 0,9NA,

WD0,096429 BW-0,244640.In the doublet lens is designed for an optical recording medium such as an optical disk, it is required to have a lower aperture (short focal length) in order to reduce the size and cost of the device is an optical sensor. Since the objective lens according to the present invention consists of two lens elements, reducing the aperture size is an important fact. The reason for this is that compared to a single-element lens, the weight of the above-mentioned lenses, uvelichenie is standing WD undesirable reduced. In practice, sometimes you cannot perform the required reduction, because to prevent contact between the objective lens and dust located on the surface of the optical recording medium, it is necessary to ensure the working distance at least equal to 50 μm. If there is a satisfactory long working distance, it significantly increases the quality of the correction of spherical aberration. In this case, the coefficient of asphericity increases and the radius of curvature of the surface decreases rapidly. This reduces the efficiency of manufacture.The limit of the aperture has different values depending on the values of NA and working distance. This is because the amount of correction of spherical aberration changes depending on the NA of the lens.From the point of view of designing and manufacturing lenses, you can easily produce a lens having improved characteristics in the case where the aperture is large.So below, with reference to Fig.22-24, describes many of the values of the diameter of the beam, the working distance (WD) and NA, suitable for the manufacture of lenses of the doublet.4-1. The upper limit of the diameter of the beam

The upper limit of the diameter of the beam is determined by the point A, the second sensor, the weight of the lens and frame for the lenses (lens holder) increase. In this case, actuator performing focusing with the servo should have a higher performance, disadvantageous from an economic point of view.For example, the objective lens (Fig.15), having an effective beam diameter of 4.5 mm and containing two lens element, has a great weight to about 250 mg. Weight of the lens, adapted for CD (compact disk) or DVD (digital video disc) is

about 200 mg, including the body of the lens. Because of the ratio type f=k/2m (where m is the mass, k is the elastic constant and f is the resonant frequency) satisfies the occasion of the work of the two-axis actuator, the value of f increases inversely proportional to the weight of the lens, preferable to control the servo, so the value of f is chosen outside the resonant frequency of the servo focus. If you prefer the full weight of the lens, including weight housing lens, 500 mg or less, the lens having a weight of 500 mg or less, including weight housing lens, not easy to construct, because the lens is heavier than the lens, which has an effective diameter of 4.5 mm (Fig. 15) and a weight of 250 mg. In this case, a two-axis actuators. Therefore, it is preferable that the effective diameter of the doublet was 4.5 mm or less.In Fig. 15 and table 3 presents design data of the lens. In Fig.16 depicts a graph showing the distortion of the above-mentioned objective lens, Fig.17 shows the astigmatism of the same objective lens, and Fig.18 shows the spherical aberration of the same objective lens. In Fig. 19 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees), and Fig.20 depicts a graph showing the lateral aberration (on the axis).4-2. The lower limit of the working distance

In Fig. 22-24 point is depicted In the lower limit of the working distance WD. Since the amount of correction of spherical aberration can be reduced in proportion to the working distance, it is possible to easily manufacture the lens. From the point of view of practical use, it is necessary to maintain a certain working distance to avoid a collision between the objective lens and the optical recording medium, for example, an optical disk, which rotates at high speed, when the focus adjustment, or contact between the dust on the surface of the optical recording medium and the objective lens, when nachinaet environment, which is contained in the environment space, usually 50 μm or less (Fig.25). Therefore, the working distance should be 50 μm or more.4-3. The upper limit of the working distance

The magnitude of the spherical aberration that can be corrected using lenses of the doublet within a certain value NA and beam diameter depends on the working distance. In the present invention proposed the construction of various lenses taking into account the curvature (angleis 55 degrees or more) allowable misalignment10 μm or more) and the allowable angle of vision (1 degree or more). Examples of the upper limit of the working distance that implement the above valid region, shown by points 1-9 in Fig.22-24. If the working distance exceeds the above upper limit, the spherical aberration is greatly increased and, thus, significantly reduces the radius of curvature of the lens. So, if it turns out such a structure, in which the working distance is not included in the area shown by diagonal lines in Fig.22-24, the lens cannot be made easily or use with an optical recording medium. Preferred about the de:

if 1,0BW<4,5, 0,05WD and 0.7NA<0.8, then WD0,25676 BW + 0,039189 (see Fig.22),

if 0,8NA<0,9, WD0,14054 BW-0,064865 (see Fig.23),

if 0,9NA, WD0,096429 BW-0,244640 (see Fig.24).Valid dezentrale (10 μm or more) is a value that is determined by the accuracy of manufacturing, for example, during injection molding using a mold. Permissible angle of vision (1 degree or more) is set to a value, which is determined by the accuracy of the inclination of the lens barrel about the optical axis.Objective lens (Fig. 22-24) satisfying the above conditions will be described as follows: the objective lens corresponding to point 2 (Fig. 22), will be described in the eighth embodiment, the objective lens corresponding to point 3 (Fig. 22), will be described in the ninth embodiment, and the objective lens corresponding to point 9 (Fig.24) will be described in the tenth embodiment.5. Lens, for which the ratio (F

_{1}/F) focal length F_{1}lenses are arranged is 7<(F/F)<a 2.5.1/F) focal length F_{1}the first lens (a lens that is near the object) 3 to the focal length F of the entire system satisfies the following field values

1,7<(F/F)<a 2.5,The above reflects the fact that the optimal power distribution is performed when the power of the first lens (the lens that is near the object) 3 is about 1/2 the power of the entire system.If (F _{1}/F)1,7, the focal length F_{1}the first lens (a lens that is near the object) 3 is short, i.e. the capacity is large. In this case, the radius of curvature, the maximum dezentrale and allowable slope for the first lens (lens located next to the second lens (lenses, located next to the object) 3 increases and power decreases. However, the power of the second lens (lens near the image) 4 increases. In this case, the radius of curvature, the maximum dezentrale and allowable tilt is performed accurately.As soon as taken into consideration a tolerance, resulting in the manufacture of lenses, the above region is sometimes extended in accordance with the NA, the effective beam diameter and working distance. In the result of calculation and research of various lenses and tolerance that occurs during the manufacturing process, was obtained from the histogram that corresponds to the lens, which has a large allowable deviation in the manufacture (Fig. 26). That is, the power distribution can be performed in an optimal way and the allowable tolerance in the manufacture can be increased considerably, if1,7<(F/F)<a 2.5.6. The lens is adjusted to match the thickness T of the transparent substrate of the optical recording medium, in the following form:if 0,7NA (numerical aperture)<0.8, then Tif 0,9NA, T<0,11 mmOptical recording medium such as an optical disk for use in the device of the optical sensor, which uses the objective lens according to the present invention has a transparent substrate (substrate disk) having a thickness of 0.1 mm, which is considerably less than 1.2 mm, which has a known CD (compact disk), and 0.6 mm, which has a DVD (digital video disc). The reason for this is that the tolerance for distortion, equivalent or superior tolerance for distortion, implemented by means of known construction by reducing coma aberration that occurs randomly when the skew of the optical recording medium. Because the amount of coma aberration, which randomly occurs when the warp drive, increases in proportion to the cube of the NA, small warp drive quickly distorts the RF when the signal is read by using the objective lens with high NA.W_{31}= (T(n^{2}-1)n^{2}sincoss)/(2(n^{2}-sin^{2}s)(^{5/2)}= (T(n^{2}-1)NA^{3}s)/(2n^{3}), where n is the refractive index of the transparent substrate, T is the thickness of the transparent who race increases in proportion to the thickness T of the transparent substrate. Therefore, reducing the thickness T of the transparent substrate is an effective means to eliminate skew. The objective lens (NA = 0,6), adapted for DVD (digital video disc) (containing the substrate disk with a thickness of 0.6 mm), creates a wavefront aberration of about 0,043 rms (RMS value) on the surface of the image (Fig.27), when there is distortion (radial distortion) with a skew angles= 0.4 degrees. When there is distortion (radial distortion)s=0.4 degrees, then NA is increased and exceeds 0.6, the wavefront aberration on the surface of the image is 0,043 rms (RMS value) due to the receipt of the thickness of the transparent substrate of about 0.32 mm in the case where NA is 0.7, about 0.20 mm in the case where NA is equal to from 0.8 to 0.9, and about 0,11 mm in the case where NA is equal to 0.9 (Fig.28). If the thickness of the transparent substrate is smaller than the above value, the aberration of the wave front, in addition, can be reduced.7. The structure of the device of the optical sensorThe device is an optical sensor according to the present invention may be a device designed for playback of the optical disk 12 (Fig. 29). The optical disc device and poluprovodnikov laser (not shown), which is the light source is a parallel light beam with a wavelength of 635 nm, passes through the polarizing beam-splitter (PBS) 7 and the plate 8/4 (1/4 wavelength), to obtain a beam with circular polarization. The laser beam with circular polarization passes through the objective lens and the substrate 5 of the disk in order to converge at one point on the signal recording surface of the optical disk 12. The substrate 5 of the disk is a thin substrate with a thickness of 0.1 mm Above the objective lens is a lens formed by two composite aspherical lenses 3 and 4 with NA of 0.7 to 0.95.The above-mentioned optical disk 12 is a single layer or multi-layer disc, which is made by joining the glass plates with a thickness of 1.2 mm, to increase the strength of the substrate 5 disk having a thickness of 0.1 mmThe laser beam reflected from the signal recording surface, is returned back to the original optical path and then passes through the plate 8/4. Thus, the laser beam becomes linearly-polarized laser beam is rotated by 90 degrees relative to the initial linear-Polaris focusing lens (collecting lens) 13, and a complex lens 14, to be detected as an electrical signal using a photodetector (PD) 15.Compound lens 14 has a surface of incidence, is performed on the surface of the cylinder (cylindrical surface), and the emissivity of the surface, made in vygnuto. Compound lens 14 has astigmatism, which allows the error signal to the focus be detected from the incident laser beam by using the so-called method of astigmatism. The photodetector 15 is a photodiode having six elements that are set to output electrical signals, perform focus adjustment using the method of astigmatism and adjust the tracking with the help of the so-called method three beams.8. ModificationThe objective lens according to the present invention is not limited to the lens, the so-called infinite system with a point of the lens (the light source). The objective lens can be made in the form of lenses of a finite system, which is made so that the point of the object (light source) is positioned at a finite distance.Embodiments of theThe following describes embodiments of the objective lens according to the present invention. In the above variant of the waves, at 635 nm, and 1,5769 when the wavelength is 680 nm).The first version of the implementationThe objective lens according to the present variant implementation has a structure in which the lenses 3 and 4 are made of optical glass with low dispersion (BACD5) having an Abbe number vd, equal 61,3 on the d-line, and the refractive index 1,589.In Fig. 30 shows the optical path. In Fig.31 depicts a graph showing the distortion of the above-mentioned objective lens, Fig.32 shows the astigmatism of the same objective lens, and Fig.33 shows the spherical aberration of the same objective lens. In Fig.34 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees), and Fig.35 depicts a graph showing the lateral aberration (on the axis).When NA get 0,8 using constraints holes using aperture 2, fussing about the change in wavelength of a semiconductor laser by +5 nm is 0,331 μm. In Fig.36 depicts the MTF (modulation transfer function) in the case when the spatial frequency in the direction of the optical axis near the point of the image is 80/mm, and in Fig.37 depicts PSF (function of the intensity at image point). As follows from Fig. 36, the maximum thy great 4. The lens according to this variant implementation allows to satisfactorily prevent chromatic aberration even if the increased focal length, or even if increasing NA.The second variant implementationThe objective lens according to the present variant implementation has a structure in which the lenses 3 and 4 are made of optical glass (FCD1) Abbe number vd, equal to 81.6 on the d-line, and optical glass (BACD5) having an Abbe number vd, equal to 61.3.In Fig. 38 depicts the optical path. In Fig.39 depicts a graph showing the distortion of the above-mentioned objective lens, Fig.40 shows the astigmatism of the same objective lens, and Fig.41 shows the spherical aberration of the same objective lens. In Fig.42 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees), and Fig.43 depicts a graph showing the lateral aberration (on the axis). The analysis conditions are shown in table 5. The objective lens according to the present variant implementation is designed in such a way that an optical glass having a high refractive index, is used to manufacture the second lens (lens near the image plane) 4 compared with optical is considerable chromatic aberration and the curvature radius of the second lens (lenses, located near the image plane) 4 is chosen large to easily perform the processing of the lens on the machine.A third option exerciseThe objective lens according to the present variant implementation has a structure in which the lenses 3 and 4 are made of optical glass (FCD1) having an Abbe number vd, equal to 81.6, and optical glass (BACD5) having an Abbe number vd, equal to 61.3.In Fig.44 shows the optical path. In Fig.45 depicts a graph showing the distortion of the above-mentioned objective lens, Fig.46 shows the astigmatism of the same objective lens, and Fig.47 shows the spherical aberration of the same objective lens. In Fig.48 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees), and Fig.49 depicts a graph showing the lateral aberration (on the axis). The analysis conditions are shown in table 6. The objective lens according to the present variant implementation satisfies the above conditions such as 1,7<(F/F)<a 2.5. Therefore, the calculation under this option implementation allows optimal distribution of power and to increase the allowable deviation in the manufacture of lenses 3 and 4.The fourth option exerciseLens, objeccao glass (FCD1), having the Abbe number vd, equal to 81.6 on the d-line, and optical glass (BACD5) having an Abbe number vd, equal to 61.3.In Fig. 50 depicts the optical path. In Fig.51 depicts a graph showing the distortion of the above-mentioned objective lens, Fig.52 shows the astigmatism of the same objective lens, and Fig.53 shows the spherical aberration of the same objective lens. In Fig.54 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees), and Fig.55 depicts a graph showing the lateral aberration (on the axis). The analysis conditions are shown in table 7.The fifth option exerciseThe objective lens according to the present variant implementation has a structure in which the lenses 3 and 4 are made of optical glass (694,532) having an Abbe number vd, equal 53,2 on the d-line.In Fig.56 depicts the optical path. In Fig.57 depicts a graph showing the distortion of the above-mentioned objective lens, Fig.58 shows the astigmatism of the same objective lens, and Fig.59 shows the spherical aberration of the same objective lens. In Fig.60 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees), and Fig.61 depicts a graph showing the lateral aberration (on the axis). Condition predestine has the structure in which the lenses 3 and 4 are made of optical glass (FCD1) having an Abbe number vd, equal to 81.6 on the d-line.In Fig.62 depicts the optical path. In Fig.63 depicts a graph showing the distortion of the above-mentioned objective lens, Fig.64 shows the astigmatism of the same objective lens, and Fig.65 shows the spherical aberration of the same objective lens. In Fig.66 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees), and Fig.67 depicts a graph showing the lateral aberration (on the axis). The analysis conditions are shown in table 9.The seventh option exerciseThe objective lens according to the present variant implementation has a structure in which the lenses 3 and 4 are made of optical glass (FCD1) having an Abbe number vd, equal to 81.6 on the d-line.In Fig.68 depicts the optical path. In Fig.69 depicts a graph showing the distortion of the above-mentioned objective lens, Fig.70 shows the astigmatism of the same objective lens, and Fig.71 shows the spherical aberration of the same objective lens. In Fig.72 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees), and Fig.73 depicts a graph showing the lateral aberration (on the axis). Condition depict what hope has the structure in which the lenses 3 and 4 are made of optical glass (FCD1) having an Abbe number vd, equal to 81.6 on the d-line, and optical glass (BACD5) having an Abbe number vd, equal to 61.3.In Fig.74 depicts the optical path. In Fig.75 showsa graph showing the distortion of the above-mentioned objective lens, Fig.76 shows the astigmatism of the same objective lens, and Fig.77 shows the spherical aberration of the same objective lens. In Fig.78 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees), and Fig.79 depicts a graph showing the lateral aberration (on the axis). The analysis conditions are shown in table 11. The objective lens according to the present variant implementation is an objective lens satisfying the ranges of the diameter of the beam, the working distance (WD) and NA (Fig. 22 and 24), while the objective lens according to the present variant of the implementation corresponds to the point 2 (Fig.22).The ninth option exerciseThe objective lens according to the present variant implementation has a structure in which the lenses 3 and 4 are made of optical glass (FCD1) having an Abbe number vd, equal to 81.6 on the d-line, and optical glass (BACD5) having an Abbe number vd, equal to 61.3.In Fig.80 depicts zobrazen astigmatism of the same objective lens, and Fig.83 shows the spherical aberration of the same objective lens. In Fig.84 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees), and Fig.85 depicts a graph showing the lateral aberration (on the axis). The analysis conditions are shown in table 12. The objective lens according to the present variant implementation is an objective lens satisfying the ranges of the diameter of the beam, the working distance (WD) and NA (Fig.22 and 24), while the objective lens according to the present variant of the implementation corresponds to the point 3 (Fig.22).The tenth version of the implementationThe objective lens according to the present variant implementation has a structure in which the lenses 3 and 4 are made of optical glass (FCD1) having an Abbe number vd, equal to 81.6 on the d-line, and optical glass (BACD5) having an Abbe number vd, equal to 61.3.In Fig. 86 depicts the optical path. In Fig.87 depicts a graph showing the distortion of the above-mentioned objective lens, Fig.88 shows the astigmatism of the same objective lens, and Fig.89 shows the spherical aberration of the same objective lens. In Fig.90 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees), and Fig.91 depicts a graph showing the lateral aberration (on the axis). The analysis conditions are shown in table todayshow regions of values of the diameter of the beam, working distance (WD) and NA (Fig.22 and 24), while the objective lens according to the present variant of the implementation corresponds to the point 9 shown in Fig.24.The eleventh version of the implementationThe objective lens according to the present variant implementation has a structure in which the lenses 3 and 4 are made of optical glass (FCD1) having an Abbe number vd, equal to 81.6 on the d-line, and optical glass (VC) having an Abbe number vd, equal 64,1.In Fig.92 depicts the optical path. In Fig.93 depicts a graph showing the distortion of the above-mentioned objective lens, Fig.94 shows the astigmatism of the same objective lens, and Fig.95 shows the spherical aberration of the same objective lens. In Fig.96 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees), and Fig.97 depicts a graph showing the lateral aberration (on the axis). The analysis conditions are shown in table 14.Twelfth variant implementationThe objective lens according to the present variant implementation has a structure in which the lenses 3 and 4 are made of optical glass (FCD1) having an Abbe number vd, equal to 81.6 on the d-line, and optical glass (VC) having an Abbe number vd, equal 64,1.In Fig.98 shows optioncostestimated the same objective lens, and Fig.101 shows the spherical aberration of the same objective lens. In Fig.102 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees), and Fig.103 depicts a graph showing the lateral aberration (on the axis). The analysis conditions are shown in table 15.Thirteenth variant implementationThe objective lens according to the present variant implementation has a structure in which the lenses 3 and 4 are made of optical glass (FCD1) having an Abbe number vd, equal 81,3 on the d-line, and optical glass (BACD5) having an Abbe number vd, equal to 61.3.In Fig. 104 depicts the optical path. In Fig.105 depicts a graph showing the distortion of the above-mentioned objective lens, Fig.106 shows the astigmatism of the same objective lens, and Fig.107 shows the spherical aberration of the same objective lens. In Fig.108 depicts a graph showing the lateral aberration (angle of vision 0.5 degrees), and Fig.109 depicts a graph showing the lateral aberration (on the axis). The analysis conditions are shown in table 16.As described above, the present invention is made so that the objective lens having a numerical aperture (NA), 0.7, made through the lens of the doublet, which includes an aspherical surface, and the device is an optical sensor contains the above-mentioned lens volume is ü from a practical point of view.The objective lens according to the present invention is made of optical glass having an Abbe number of 40 or more, in order to prevent chromatic aberration even with increasing NA. If the light source used semiconductor laser, it is possible to increase the allowable deviation for the variation of the wavelength of a semiconductor laser, and thus it is possible to increase the productivity of manufacturing.Since the objective lens according to the present variant of the implementation are made so that the refractive index of the lens having a lower radius of curvature increases, the radius of curvature may be higher and the lens can be easily made.Since the objective lens according to the present invention is made so that the diameter of the beam, NA and working distance is limited, the device size of the optical sensor can be reduced, the focal length can be reduced and you can easily make a lens with a high NA. Since the objective lens according to the present invention has small dimensions, it is possible to reduce the size of the two-axis actuator for moving the objective lens.Since the objective lens according to the present invention has the correct focustm, each lens element can be easily made and can easily improve their work, thus resulting in the satisfactory performance of manufacturing.Using the present invention can easily manufacture the objective lens, which allows you to satisfactorily correct chromatic aberration in a sufficiently large numerical aperture (NA), and to reduce its weight.The device is an optical sensor according to the present invention having the above-mentioned objective lens and adapted for optical recording medium which includes a transparent substrate whose thickness is defined, adapted to the coma-aberration. In the result, it is possible to easily manufacture the optical recording medium.Although the invention is described in its preferred form with a certain degree of specificity, it should be understood that the present description of the preferred form can be changed in the details of construction, combination and arrangement of parts without disturbing the nature and scope of the invention presented here.

Claims

1. The objective lens having at least two lens elements made of optical STA, in which at least any one of the surfaces is made in the form of an aspherical surface and a numerical aperture of 0.7 or more.2. The objective lens under item 1, characterized in that the Abbe number at d-line optical glass is made of two lens element is 60 or more, and numerical aperture leaves of 0.8 or more.3. The objective lens under item 1, characterized in that the refractive index of the optical glass is made of one of the lens elements, in which the angle formed between the tangential plane at the periphery of the lens element and the plane perpendicular to the optical axis, is greater than the corresponding angle in the other lens element is n_{1}and the refractive index of optical glass, which made the other lens element is n_{2}satisfies the following relations:n_{1}>n_{2}.4. The objective lens under item 1, characterized in that the diameter of the incident laser beam BW, the working distance WD, and a numerical aperture NA satisfying the following relationships:if 1,0BW<4,5, 0,05WD and 0.7NA<0.8, then WD0,25676 BW + 0,039189;if 0,7NA (numerical aperture)<0.8, then T0.32 mm,if 0,8NA<0,9, T0.20 mm, andif 0,9NA, T0,11 mm

7. The device is an optical sensor including a light source and the objective lens, designed for information, in one point of the laser beam emitted from the light source to the surface of the signal recording optical recording medium, characterized in that Ebbe, equal to 40 or more at d-line, and having a structure of a doublet, with at least each surface is made in the form of an aspherical surface and a numerical aperture of 0.7 or more.8. The device is an optical sensor under item 7, characterized in that the Abbe number at d-line optical glass is made of two lens element is 60 or more, and a numerical aperture of 0.8 or more.

**Same patents:**

FIELD: optics.

SUBSTANCE: device has positive component including biconvex lens and negative lens in form of meniscus, on the side of object, and negative component, in form of meniscus, on the side of image. Onto one of optical surfaces of positive component lenses a hologram optical element is applied having optical force 0.01-0.1 of total objective force, while characteristic equation of hologram optical element is V_{H}=A_{1}y^{2}+A_{3}y^{6}+A_{3}y^{6}, where A_{1}, A_{2}, A_{3 }- coefficients; y - height on surface of hologram optical element. Coefficient A_{1} is proportional to optical force of hologram optical element, and coefficients A_{2} and A_{3}, respectively, are proportional to spherical aberration of positive and negative objective components. Negative component on the side of image is directed to it by convex portion. Negative lens of positive component is placed between biconvex lens and object and is directed to object by convex portion. Objective is also equipped with additional component in form of biconvex lens, placed between negative and positive components.

EFFECT: higher efficiency, higher image quality.

5 cl, 2 dwg

FIELD: optical engineering.

SUBSTANCE: objective has positive component disposed at the side of object. Positive component has two lenses one of which has to be biconvex. Objective also has negative component disposed at the side of object and made in form of meniscus. Biconvex lens of positive component has focal power being equal to 0,3-05 total focal power of objective. The other lens of objective is made in form of positive meniscus turned with its convexity to object. The lens has focal power being equal to 0,15-0,25 of total focal power of objective. The lens is disposed between object and biconvex lens at distance being equal to 0,15-0,25 of focal length of objective. Hologram optical element is applied onto one optical surface of the lens of positive component; focal power of the element equals to 0,01-0,1 focal power of objective. Negative component is turned with its convexity to image and it has focal power of 0,15-03 focal power of objective. Objective is provided with additional component in form of asymmetric biconvex lens with focal power of o5-0,8 focal power of objective; the lens is disposed between negative and positive components at distance of 0,3-0,6 focal length of o objective from negative component and turned to object with the side having smaller radius of curvature.

EFFECT: improved correction of aberrations; improved quality of image; widened field of view of objective.

2 cl, 2 dwg

FIELD: optics.

SUBSTANCE: objective contains, in direction from screen plane towards modulator plane, first and second groups of lens elements, flat-parallel plate, prism, flat-parallel plate and aperture diaphragm, situated near the first lens element of the second group. The first group of lens elements has negative optic force and consists of five single lenses - first lens in form of negative meniscus, both surfaces of which are made aspheric, second lens in form of negative meniscus, third biconcave lens, at least one surface of which is made aspheric, fourth biconcave lens and fifth biconvex lens. Second group of lens elements has position optical force and contains five single lenses, first one of which is a position meniscus, second one - negative meniscus, third one - biconvex lens, fourth one - positive meniscus, at least one surface of which is made aspheric, fifth one - positive meniscus, facing the modulator with its convex part.

EFFECT: increased relatively aperture of wide-angle projection objective, decreased value of remaining television distortion.

5 dwg

FIELD: physics.

SUBSTANCE: lens can be used in CCD receivers, for example in robot computer vision systems through direct mounting on the manipulator. The objective lens has four components. The fourth component is glued from a converging lens and a negative meniscus whose concave side faces the object. The second and third components are positive biaspherical separate lenses. The fourth component is a negative separate biaspherical meniscus whose concave side faces the image. Coefficients of each aspherical surface are determined using the equation: where: z is the arrow of the surface parallel the z axis; c is surface curvature; k is the conical constant of the surface; h is the current coordinate; A, B, C are coefficients of deformation of the 4^{th}, 6^{th} and 8^{th} order, respectively.

EFFECT: design of a compact lens with high information content through minimisation of barrel distortion with simultaneous maintenance of high image quality.

3 cl, 3 dwg

FIELD: medicine.

SUBSTANCE: invention relates to medical equipment, in particular to field of biometric identification of individuals. Afocal system of skin pattern scanning contains multi-element source of irradiation 9, optic system, which includes sensor optic element 1 with angle of complete internal reflection, two positive lens component 2,4, which form afocal dually telecentric optic system, forming optic bundle, determining optic image of skin print, satisfying condition of angular connection of object planes and image and multi-element photoreceiver 6. Source of irradiation 9 and multi-element photoreceiver 6 are connected with controller 13. First lens component consists of plano-convex lens 2, facing with convexity image space, second component consists of plano-convex lens 4, facing with convexity image space.

EFFECT: system application will make it possible to obtain high-quality finger prints with small distortions and high resolution in accordance with modern requirements as to the quality of dactyloscopic information, as well as reduce device dimensions.

7 cl, 6 dwg

FIELD: optics.

SUBSTANCE: helmet-mounted wide-angle collimating optical system comprises display projector, including liquid crystal display, lens projection system consisting of three components, two-mirror component and splitting collimating concave mirror, connecting image from outer space and from liquid crystal display. Projection lens system made with telecentric stroke of main beams in space of liquid crystal display. At that, first component comprises biconvex lens and positive meniscus, second component is made of positive and negative meniscus and negative hyperbolic biconcave lens. Third component is made from positive meniscus and biconvex lens.

EFFECT: technical result consists in simplifying design of protective glass helmet-mounted system, providing telecentric main beams in space of liquid crystal display, increase brightness due to illuminate liquid crystal display reflected polarised beams, normal to display surface, and provision of high quality on entire field of entrance to pupil diameter of not less than 14 mm.

2 cl, 3 dwg

FIELD: physics.

SUBSTANCE: objective has series-arranged along optical axis first and second aspherical negative menisci and aspherical biconvex lens. First meniscus has first aspherical concave surface, facing object plane, and second convex spherical surface. Second meniscus has first aspherical convex surface, facing object plane, and second aspherical concave surface. And biconvex lens has first aspherical and second spherical surfaces. All lenses are made of different types of glass. Dispersion coefficient ν_{(C)} of first and second lenses is 25<ν_{C}<35, which is 2÷2.5 times less than dispersion coefficient of material of third lens. Ratios are met: f'_{1}=-(1.3÷1.5)f', f'_{2}=-(29.6÷30.0)f', f'_{3}=(0.5÷0.55)f', where f', f'_{1, }f'_{2}, f'_{3 }are focal distance of objective, first, second and third lenses. Light diameter D_{L1} of first objective lens and total length of objective L_{tot} are in ratio 0.85<L_{tot}/D_{L1}<0.9.

EFFECT: increased level of aberration correction under condition of invariance of main objective parameters.

1 cl, 1 tbl, 1 dwg

FIELD: physics.

SUBSTANCE: lens comprises 3 menisci. The first and the third menisci - positive, made of germanium. The second meniscus - negative, made of zinc selenide. All menisci face the image plane with their concave surfaces. The second surface of the first meniscus is an aspherical surface of the second order with a conic constant in the range of 0,2÷0,5. The second meniscus is moveable along the optical axis. The relations are performed:ϕ_{1}:ϕ_{2}:ϕ_{3}=(0,70÷0,90):-(0,10÷0,60):(1,0÷1,80), where ϕ_{1}:ϕ_{2}:ϕ_{3} - the relative optical powers of, respectively, the first, the second and the third menisci; D2/f'=0,3÷0,7; D4/f'=0,2÷0,6, where D2 - the air gap between the first and the second menisci; f'- the focal length of the lens, D4 - the air gap between the second and the third menisci.

EFFECT: increasing the image quality in normal climatic conditions and ensuring the lens operation in the temperature range from minus 40 to 50 degrees without compromising the image quality.

3 dwg, 2 tbl

FIELD: physics.

SUBSTANCE: lens can be used in thermal imagers with matrix photosensitive cells sensitive to the spectral range from 8 to 12 mcm. The lens contains three meniscuses. The first and third meniscuses-positive face concave surfaces to the plane of the image and made of germanium. The concave surfaces of the meniscuses are conical: the conic constant of the first meniscus is from 1 to 2.4, and the third meniscus is from (-1.9) to (-5.9). The second negative meniscus is concave surface to the plane of the image and made of material with a refractive index from 2.2 to 2.8. Operating the equations: ϕ_{1}=(0,71÷0,8)ϕ, ϕ_{2}=-(0,46÷1,17)ϕ, ϕ_{3}=(1,63÷2,16)ϕ, where ϕ_{1}, ϕ_{2}, ϕ_{3} - relative optical force of the first, second, third meniscuses; ϕ -the optical power of the lens; D2/L=0,21÷0,41; D4/L=0,15÷0,36 where D2, D4 - Air gaps between first and second and the second and third meniscuses; L is the length of the lens.

EFFECT: improvement of image quality and reduced length of the lens.

4 cl, 11 dwg