# Optical system for correcting the shape of a rectangular laser beam

(57) Abstract:

The optical system includes sequentially located along the rays two positive spherical lens. Lenses installed with a slope in opposite directions relative to the axis of the laser beam in the plane of greatest angular divergence of the beam. The distance s from the output window of the laser to the first lens, the focal length f of the lens and the angle of the axes of the lenses relative to the beam axis of the laser are determined from the ratios. Reduces distortion aberration of the laser beam. 4 Il. The invention relates to optical systems for correcting the shape of a rectangular laser beam and can be used to correct the shape of the beam gap junction CO_{2}or CO laser.Known optical system for correcting the shape of the laser beam containing prisms and cylindrical lens [1, 2]. The disadvantage of these systems is the high cost of manufacture of prisms and cylindrical lenses.Known optical system for correcting the shape of a rectangular laser beam containing spherical mirrors [3]. The disadvantage of this system is the complexity of the design due to the turning axis of the laser beam in the y is the optical system, containing decentered spherical lens [4]. The disadvantage of this system is the lowest quality-adjusted laser beam due to the aberration of distortion.The aim of the present invention is to reduce distortion aberration corrected laser beam.This objective is achieved in that the optical system for correcting the shape of a rectangular laser beam containing sequentially located along the rays two positive spherical lens, the lenses are tilted in opposite directions relative to the axis of the laser beam in the plane of greatest angular divergence of the laser beam, the distance s from the output window to the first lens, the focal length of the lens f and the angle of the axes of the lenses relative to the beam axis of the laser are determined from the following relations:

< / BR>

< / BR>

< / BR>

where z

_{x}, z

_{y}- confocal parameter of the laser beam in planes smallest and largest angular divergence, respectively;

k

_{1}= (z

_{x}s

_{y}- z

_{y}s

_{x})/(z

_{x}- z

_{y};

k

_{2}= (z

_{x}s

_{y}

^{2}- z

_{y}s

_{x}

^{2})/(z

_{x}- z

_{y});

k

_{3}= (s

_{x}+ s)/(z

_{n is the refractive index of the lens material.In Fig. 1 shows an optical system for correction of astigmatic shape of the laser beam, the slit in the plane X smallest angular divergence of the beam; Fig. 2 - the same in the plane Y greatest angular divergence of the beam; Fig. 3 and 4 is a variant of the optical system for correcting the astigmatic shape of the laser beam with the reduced dimensions, sections in the plane of X and Y, respectively.The optical system contains placed on the beam axis slotted waveguide laser two identical spherical lens mounted tilt in opposite directions relative to the axis of the laser beam in the Y plane, perpendicular to the plane of the walls of the waveguide.The optical system works in the following way. In the plane X, parallel to the plane of the walls of the waveguide, the beam slotted laser is characterized by small angular divergence and a large distance from the output window of the laser to the waist of the beam. In the plane Y perpendicular to the plane of the walls of the waveguide, on the contrary, the beam is characterized by a large angular divergence and a small distance from the output window of the laser to the waist of the beam [5, 6]. Accordingly, confocal rebrushed a laser beam so that that the output beam confocal parameter and the position of the banners are the same as in plane X and plane y Total confocal parameter of the output beam is equal to the confocal parameter of the laser beam in the Y plane, and the total distance from the second lens to the focal waist of the output beam is equal to the distance from the first lens to the focal waist of the laser beam in the plane Y. Under these conditions in the Y plane of the first lens on the laser beam is opposite to the second lens, therefore, the aberration of distortion caused by decenterable lenses are mutually compensated. In the plane X such aberration distortion-free.Thus astigmatic beam slotted laser is converted by the optical system in a symmetric beam, free from distortion aberration. The converted beam can be focused by a spherical lens and used for various applications.In Fig. 1 and 2 shows:O is the center of exit window of the laser;ABOUTxABOUTycenters constrictions of the laser beam in planes X and Y, respectively;ABOUT3center banners skorrektirovannogo beam;ABOUT1O2centers of the first and second lenses, respectively;AxA1A2A3Let us introduce the notation:OxO = sx; OyO = sy; OO1= s; A1B1= a1, A2B2= and2;zx, zy- confocal parameter of the laser beam in planes X and Y, respectively;Zx, Zy- confocal settings skorrigirovanna beam in planes X and Y, respectively.Let us assume that the thickness of the lenses and the distance between the lenses is much less than the distance from the lens to the focal waist of the laser beam. Then the above conditions, the lack of distortion aberration can be set by the following relations:a1=a2; Zx=zy; Zy=zy. (1)Considering the passage of the laser beam through the lens in the paraxial approximation [7], the relation (1) can be represented as follows:zx+ (sx+ s)2/zx= zy+ (sy+ s)/zy; (2)fx2= zx2+ (sx+ s - fx)2zy/zx; (3)fy2= zy2+ (sy+ s - fy)2; (4)where fxand fy- equivalent focal length of the optical system in the planes X and Y, respectively.Equivalent focal length optical system:< / BR>where is the angle of the axes of the lenses relative to the beam axis of the laser;f is the focal length of the lens;n is the refractive index of the lens material.From (4) - (7), after transformations we get the following relations:< / BR>< / BR>< / BR>k1= (zxsy- zysx)/(zx- zy); (9)k2= (zxsy2- zysx2/(zx- zy); (10)k3= (sx+ s)/(zx- zy); (11)< / BR>fy= zy2/(sy+ s) + sy+ s. (13)For slotted laser characteristic value of the confocal parameters zx, zyand distances sx, syfrom the output window of the laser to the constrictions of the beam in planes X and Y lie within zx= 2000 - 8000 mm, zy= 200-800 mm, sx= 400 - 1200 mm, sy= 15 - 60 mm From the relations (8) - (13) we can obtain that the corresponding values of the distance s from the output window of the laser to the first lens, the focal length f of the lens and the angle of the axes of the lenses relative to the axis of the laser beam lies in the range: s = 600 - 1500 mm; f = 2000 - 5000 mm; = 35 - 45o.For example, direct measurements of beam parameters developed gap junction CO2laser obtained the following values: sx=elemid zinc with refractive index n = 2.4. From relations (8) - (13) are determined by the design parameters of the optical system for correcting the shape of the laser beam: s = 1040 mm; f = 3140 mm; = 41o30'.With a large width of the laser beam ratio (8)-(13) lead to a large value of the distance from the output window of the laser to the first lens and, hence, to a large longitudinal dimension of the optical system. The longitudinal dimension can be reduced considerably, if directly behind the exit window of the laser of the optical system for correcting the shape of the beam to install a telescopic system consisting of two spherical lenses. Telescopic system proportionally reduces the cross-sectional sizes and increases the angular divergence of the laser beam, that is, the action of the telescopic system is equivalent to zoom along the beam axis of the laser. In accordance with this reduced longitudinal dimension of the optical system for correcting the shape of the laser beam.In Fig. 3 and 4 additionally shows:O'x, 'ycenters banners beam telescopic system in the planes X and Y, respectively;P1P2centers of the first and second telescopic lens system, respectively.Enter dopolnitelnyefunktsii first and second telescopic lens system, respectively;z'xz'y- confocal beam parameters after a telescopic system in the planes X and Y, respectively.Considering the passage of the laser beam through a telescopic system in the paraxial approximation [7], you can get:z'x= (f2/f1)2zx; (14)z'y= (f2/f1)2zy; (15)s'x= (f2/f1)2(sx+ p - f1) + 2 f2+ p; (16)s'y= (f2/f1)2(sy+ p - f1) + 2 f2+ p. (17)The design parameters of the optical system for correcting the shape of the beam transmitted through the telescope system are determined by the relations (8) - (13), if they make the substitution zx, zy, sx, syfor z'xz'ys'xs'yrespectively.For example, a laser beam is above parameters, and the distance from the exit window of the laser to the first telescopic lens system and the focal length of the first and second telescopic lens system, respectively, p = 10 mm; f1= 100 mm; f2= - 50 mm as a material for the manufacture of lenses used zinc selenide. From relations (6)-(17) are defined constructive parikmaherskiy the slotted beam laser is converted by the optical system in a symmetric beam, free from aberration distortion. The converted beam can be focused by a spherical lens and used for various applications.List of used sources1. A. S. USSR N 1624392, MKI5G 02 In 27/30, publ. 30.01.91, bull. N 4.2. Patent EP N 0100242, MKI5G 02 B 13/00, H 01 S 3/00, publ. 29.01.89.3. U.S. patent N 5206763, MKI5G 02 In 5/10, G 01 17/06, publ. 27.04.93.4. Computational optics. Reference under the General editorship of Professor M. M. Rusinov. L., "engineering", 1984, page 304.5. U.S. patent N 5283797, MKI5H 01 S 5/04, publ. 01.02.94.6. A. D. Colley, F. Villfreal, H. J. Baker, D. R. Hall. Hgh brightness slab waveguide carbon monooxide laser. Appl. Phys. Lett. 64 (22), May 1994.7. I. I. Pakhomov, A. B. Tsibulya. The calculation of the optical systems of laser devices. M., "Radio communication, 1986. Optical system for correcting the shape of astigmatic laser beam containing sequentially located along the rays two positive spherical lens, wherein the lenses are tilted in opposite directions relative to the axis of the laser beam in the plane of greatest angular divergence of the beam, the distance s from the output window of the laser to the first lens, the focal length f of the lens and the angle of the UB>x, zy- confocal parameter of the laser beam in planes smallest and largest angular divergence, respectively;k1= (zxsy- zysx)/(zx- zy);k2= (zxsy2- zysx2)/(zx- zy);k3= (sx+ s)/(zx- zy);< / BR>fy= zy2/(sy+ s) + sy+ s;sx, sy- the distance from the exit window of the laser to the constrictions of the laser beam in planes smallest and largest angular divergence, respectively;n is the refractive index of the lens material. }

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