Polarising prism

FIELD: physics.

SUBSTANCE: prism is composed of three Iceland spar crystals glued together, the optical axes of which are parallel to the input face of the prism and to each other. The refraction index of the glue is less than the refraction index for an ordinary ray. The crystals are cut at an angle which provides total internal reflection of an ordinary ray from the gluing line. The middle crystal is rhomb-shaped in the principal cross-section. The angle between the faces of the crystals, which provides total internal reflection of an ordinary ray, is greater than where nk is the refraction index of the glue used to glue the crystals; no is the refraction index for an ordinary ray in Iceland spar; and less than where ne is the refraction index of an extraordinary ray in the crystal. Side crystals have a symmetric shape relative the centre of the cross-section of the middle crystal, and the output face is perpendicular to the reflected ordinary ray.

EFFECT: high accuracy of linking the direction of the polarisation plane with the normal to the optical surface of the polariser.

4 cl, 4 dwg

 

The invention relates to the optical instrument and can be used in the design of opto-mechanical devices for measuring angles between the normals of the mirrors located at different levels in height.

Mirrors can be installed at various sites, which spreads in a given plane relative to each other must be measured.

For determining the relative spreads of the two devices can be used various types of polarimeters based on the fact that the radiation that has passed through one polarizing device is extinguished another polarizing device to zero intensity when the optical axis of these devices are located at a 90°angle.

As polarizers and analyzers in these devices have different polarizing prism: Nicolas, Frank-Ritter, Glan-Thompson, Wollaston, Rochon, Starman[1, 2, 3, 4, 5].

The closest technical solution of the present invention is a polarizing prism Nicolas [6].

The prism is made of Iceland spar. Two crystal of Iceland spar glued canadian balsam with refractive index n=1,549 having an intermediate value between the refractive index of the crystal for ordinary noand extraordinary rays ne.

For ordinary luchakansky balm is an optically less dense medium, and for extraordinary - more dense. Therefore, the ordinary beam can overcome a layer of balm only when the angle of incidence on the plane of the section is less than the critical angle of total internal reflection. In this case, the ordinary rays are eliminated due to the total reflection.

The extraordinary ray passes through the layer of Canada balsam, as it reflected excluded.

Prism Nicolas is a great polarizer, but does not exactly map the polarization plane of the normal to the mirror.

The main task, which is aimed invention is to improve the accuracy of the binding direction of the polarization plane and the normal to the optical surface of the polarizer.

To solve this problem is proposed polarizing prism, which, like the prototype, made from several crystals of Iceland spar, cut at an angle, providing total internal reflection of the ordinary ray from the line gluing and pasted, the index of refraction less than the index of refraction for the ordinary ray.

Unlike the prototype prism glued together from three crystals of Iceland spar, the optical axis of which is parallel to the entrance face of the prism, while the average crystal in the main section has a diamond shape, the opposite face of which is about parallel to each other, and the angle between the faces of the crystal, providing total internal reflection of the ordinary beam, more than,

where nkis the refractive index of the adhesive that bonded crystals;

naboutis the refractive index of the ordinary ray in Icelandic spar and less,

where nethe refractive index of the extraordinary ray in Icelandic spar, lateral crystals have a symmetrical shape relative to a center point of the cross section of the Central crystal.

To work in two opposite directions, the polarization prism is equipped with the axis of rotation of the prism 180° around its center.

The side of the middle of the crystal, perpendicular to the optical axis, polished and deposited mirror coating.

Polarizing prism supplemented wedge set before the face of the average crystal with a mirror coating.

The essence of the invention lies in the fact that the polarization prism is made of three crystals of Iceland spar and has a symmetrical design that allows you to swivel it 180° to work with two opposite directions. In addition, we offer prism face perpendicular to the optical axis of the crystal, polished and deposited mirror coating.

The design of the proposed polarization the second prism allows you to skip the extraordinary optical beam and reflects the ordinary when falling beam from two opposite sides.

Prism is installed on the exact axis and can be rotated 180°, with the axis of rotation parallel to the optical axis of the crystal prism.

Thus, the combination of the above features allows you to solve the problem.

The essence of the proposed utility model is illustrated in the drawings, in which figure 1 presents the design and course of the rays of the prism; figure 2 shows the polarization prism mounted on an axis; figure 3 shows a machine on which you are aligning prism; figure 4 shows a machine on which you are aligning prism analyzer.

The proposed polarization prism glued together from three crystals 1, 2 and 3 of Iceland spar, the optical axis 4 which are parallel to the entrance face of the prism, while the average crystal 2 in the main section has a diamond shape, opposite sides of which are parallel with each other, the angle α between the faces of the crystal, providing total internal reflection of the ordinary beam, more than,

where nkis the refractive index of the adhesive that bonded crystals;

naboutis the refractive index of the ordinary ray in Icelandic spar and less,

where nethe refractive index of the extraordinary ray in Icelandic spar, lateral crystals 1 and 3 are symmetric shape about the relative center point of the cross section of the Central crystal 2.

The side of the middle of the crystal 2, perpendicular to the optical axis 4 of the prism, polished and deposited mirror coating 5.

To compensate for aperpendicular mirror cover 5 to the optical axis of the crystal before it installed the wedge 6.

Prism is installed in a frame that can be rotated with the shaft 7 at an angle of 180°. For placing the optical axis of the crystal parallel to the axis of rotation is provided by a gasket 8.

Thus, a polarizing prism glued together from three crystals 1, 2 and 3, made of Iceland spar. The optical axis of all three prisms are parallel. Prisms glued together with adhesive, and having a refractive index less than the index for the ordinary ray n0=1,658.

For example, glue UV 215 with a refractive index of nk=1,425. The angle α is selected from a ratio of nk/ ne≥sinα≥nk/ naboutwhere nethe refractive index of the extraordinary beam ne=1,486.

Glue UV 215 1,425/1,486≥sinα≥1,425/1,658

0,956≥sinα≥0,859 here

73°30≥α≥59°15'.

Thus, the falling of the light beam dividing face of the prism at an angle from 89° 15' 79° 30' ordinary rays will be totally reflected by a dividing face of the prism, and an exceptional pass through it.

For prisms should be made a condition to the axis of rotation of the prism is parallel to the crystal axis, i.e. parallel to the polarization.

This is done with the setup shown in figure 3.

The illuminator 9 illuminates the prism polarizer 10, fixed on the shaft 7 through the gasket 8. The optical axis of the analyzer 11 is expanded by 90° relative to the axis of the prism polarizer 10, and the radiation from the illuminator 9 does not pass through the system, and a signal from the photodetector 12 is equal to 0.

The alignment is carried out as follows:

In the position shown in figure 4, the reversal of the analyzer 11 around the light beam get 0 signal from the photodetector 12. Then deploy the prism polarizer 10 180° so that the beam was incident on the prism, is marked with the letter "P". Turning the prism 10, the processing of strip 8 and the analyzer 11, and achieve again 0 signal from the photodetector 12.

The signal from the photodetector 12 will remain zero during rotation of the prism 10 at 180° only when the axis of rotation is parallel to the optical axis of the prism.

Next turn wedge 6 ensure that the normal to the mirror surface 5 of the prism is parallel to the axis of rotation 7 of the prism. Since the optical axis of the prism parallel to the axis of its rotation, while the normal to the mirror surface 5 of the prism with the given angle beam wedge 6 will be parallel to the axis of the prism.

Aligning prism analyzer is performed on the installation, shown in figure 4.

The illuminator 9 light field is isator 13. The light beam passes through the polarizer 13, enters the prism analyzer 10 and passing it on the photodetector 12.

The optical axis of the polarizer and analyzer are rotated by 90°. In this position, the radiation of the light source does not pass through the system and the signal from the sensor 12 will be zero.

Then deploy the prism 10 analyzer 180° so that the light beam falls on the average crystal 2 with the other hand. Turning the prism 10, the processing of strip 8 and the polarizer 13, achieve again zero signal from the photodetector 12.

The signal from the photodetector 12 will remain zero during rotation of the prism 10 at 180° only when the axis of rotation is parallel to the optical axis of the prism.

We are now aligned so prisms of the optical axis of the crystals are parallel to the axis of rotation, but the mirror surface on the lateral surfaces of the prisms may not be perpendicular to the axis of rotation. Since these surfaces are then used to bind to the underlying mirrors of interest, before the mirror surfaces installed wedges 6 (Fig 3 and 4), the reversal of which ensure the continuation of the normal to the mirror surface is not deviated in the horizontal plane during rotation of the prism 180°.

Polarizing prisms proposed design can be applied directly in the device is Oh, define the mutual reversal of interest as polarizer and analyzer and to generate the reference instruments of the analyzer and polarizer, in which the plane of polarization aligned with the geometric surface of the prism.

Sources of information

1. Russian Federation patent No. 2060519, IPC: G02 5/30, 27/28, 1996

2. Russian Federation patent No. 2062494, IPC: G02 5/30, 1996

3. A.A. Chichlowski. Applied physical optics. Fizmatgiz, Moscow, 1961 (Polarimeter).

4. Nphmeleva, V.I. Kolganova, T.M. Loseva. Physical optics. Moscow, Mashinostroenie, 1991, s.226.

5. Al bulls. Optics. Moscow, Higher school, 1986, p.á192.

6. Russian Federation patent No. 2080629, IPC: G02 5/30, 1997 - the prototype.

1. Polarizing prism made of a few crystals of Iceland spar with parallel axes and cut at an angle, providing total internal reflection of the ordinary ray from the line gluing and pasted, the index of refraction less than the index of refraction for the ordinary ray, characterized in that the prism is glued together from three crystals, the optical axis of which is parallel to the entrance face of the prism, while the average crystal in the main section has a diamond shape, the opposite faces of which are parallel to each other, and the angle between the faces of the crystal, providing a full DNAs is Rennie reflection ordinary beam, more than,
where nkis the refractive index of the adhesive that bonded crystals;
naboutis the refractive index of the ordinary ray in Icelandic spar;
and less,
where nethe refractive index of the extraordinary ray in the crystal;
lateral crystals have a symmetrical shape relative to a center point of the cross section of the middle of the crystal, and exit face perpendicular to the reflected ordinary beam.

2. Polarizing prism according to claim 1, characterized in that two opposite directions it is equipped with the axis of rotation of the prism 180° around its center.

3. Polarizing prism according to claim 1, characterized in that the side of the middle of the crystal, perpendicular to the optical axis, polished, and deposited mirror coating.

4. Polarizing prism according to claim 3, characterized in that it contains wedge set before the face of the average crystal with a mirror coating.



 

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