An interferometer for controlling of the form of prominent, concave spherical and flat surfaces of large-sized optical components

FIELD: measuring instruments.

SUBSTANCE: the interferometer for controlling of the form of prominent, concave spherical and flat surfaces of large-sized optical components has a source of monochromatic radiation, a collimator and an objective, one after another located a beam divider, a flat mirror and an aplanatic meniscus with a reference surface and also an observation branch located behind the beam divider in beam return and a working branch consisting out of a spherical mirror with a compensator which form a focusing system. Depending of the form of a controlled surface focusing of the working branch of the interferometer is executed at replacing the compensator and the basic block of the interferometer which has an illuminating branch. A beam divider, a flat mirror, an aplanatic meniscus and an observation branch relative to a fully stabilized spherical mirror along an optical axis on such a distance at which the beams reflected from the spherical mirror fall on the controlled surface transversely to its surface.

EFFECT: expansion of nomenclature of controlled surfaces, decreasing large-sized dimensions of the interferometer.

2 cl, 3 dwg

 

The invention relates to measuring equipment, namely, interferometry, and can be used to control the shape of the large concave, convex, spherical and flat surfaces.

Known interferometer to control the surface shape of the convex spherical surfaces of lenses of large diameter (USSR Author's certificate No. 448347, .G 01 9/02, 1972)containing a laser light source, consistently placed on the telescopic system, a beam splitter, a lens, a compensator, a reference spherical mirror, the Registrar of the interference pattern.

The disadvantage of the interferometer is relatively large dimensions of the reference mirror surface, and controls only the convex spherical surfaces bounded range.

Closest to the invention to the technical essence is the interferometer to measure the shape of a spherical lens surfaces (USSR Author's certificate No. 1068699, CL G 01 In 9/02, 1984), containing consistently located the source of monochromatic light, a quarter-wave phase plate, telescopic system, the lens and the lens, forming a lighting branch, the compensator and the reference spherical mirror, forming a working branch and Supervisory system.

The disadvantage of the interferometer is its complexity,the necessity of application in each case of special control compensator and replacement of optical components in the working branch of the interferometer, the inability to control the flat optical surfaces.

The problem to which the invention is directed, is expanding the range of controlled surfaces as spherical convex and concave and flat surfaces, reducing the overall dimensions of the interferometer.

The technical result, which is achieved by solving this problem is to increase the performance of control and precision.

This technical result is achieved due to the tunable focus system working branch of the interferometer, which entered as the focusing system of the large spherical mirror and lens compensator. Interferometer to measure the shape of convex, concave, spherical and flat surfaces of large optical components includes lighting branch consisting of a monochromatic light source, a collimator lens, sequentially arranged a beam splitter, a flat mirror and atlanticheski meniscus with the reference surface, and Supervisory branch, located behind the beam splitter in reverse the course of the rays, and the working branch, consisting of a spherical mirror with a compensator, which form the focusing system. To change the focus of the working branch of the interferometer must be mutual is the third movement of the compensator and the base unit of the interferometer, consisting of lighting branch, beam splitter, flat mirrors, Atlanticheskogo meniscus and Supervisory branch, a relatively fixed spherical mirror along the optical axis at such distances at which the rays reflected from the spherical mirror, drop on controlled items are perpendicular to their surfaces regardless of the shape of the test surface.

The drawing shows the optical scheme of the interferometer for inspection of large optical components concave (1A), convex (1B) spherical and flat (1B) surfaces.

The interferometer consists of lighting branch 1, comprising a monochromatic light source, a telescopic system and lens, sequentially arranged a beam splitter 2, a plane mirror 3, atlanticheski meniscus 4 with the reference surface, the focusing system working branch of the interferometer, consisting of a compensator 5 and (6) and large mirror 7, a controlled surface 8 and the Supervisory branch 9.

The interferometer works as follows.

Rays of light generated by the lighting branch 1, pass through a beam splitter 2, a plane mirror 3, fall on the reference surface Atlanticheskogo meniscus 4, addressed to the working branch of the interferometer, is partially reflected from the reference surface and create the coupon wavefront comparison. Another part of the beams passes through the reference surface, the compensator 5 and (6), large mirror 7 and falls along the normal to the test surface 8, is reflected from the test surface, forming a work wavefront comparison. Then the radiation passes the working branch of the interferometer in the opposite direction and interferes with the reference wave front. A beam splitter 2 deflects the light rays reflected from the reference surface 4 and the surface 8, the Supervisory branch 9. To expand the range of testing parts in a working branch of the interferometer as the focusing system introduced large spherical mirror 7 and the lens compensator 5 and (6). This allows you to control how the spherical convex and concave, or flat surface to use reference and auxiliary optical elements are much smaller length diameter than the controlled surface and to limit the length of the subject line which is connected with the coherence length of the laser and the requirement for vibration protection scheme of the interferometer.

In the above schemes restructuring of the focus working branch is carried out by means of relative displacement of the base unit and expansion joint along the optical axis fixed spherical mirror. The estimated distance between the baseline is the first block, the expansion joint and a spherical mirror shown in the drawing. The value of the spherical aberration of the wave front generated by large mirrors will be significant. To compensate for the spherical aberration of the mirror designed two lens compensator. When calculating the expansion joints used method for compensating aberrations of the normals of the surfaces (Pureav DT Methods of aspheric optical surfaces. M: Mechanical Engineering, 1976).

In this case, all rays fall on a controlled surface perpendicular to its surface. The expansion joint with a spherical mirror provide such course of rays, where the real wave front rather precisely with the allowable error is converted back into a spherical or planar wave front.

Design designed lens compensators is quite simple. For control of the concave and convex surfaces of the lens designed compensator consists of two concatenated element 5. For control of flat surfaces is used above the compensator with an additional two-glued element 6. The manufacture of a spherical mirror does not cause significant difficulties.

Computational experiments showed that the proposed scheme of the interferometer allow you to control:

convex spherical p is the surface radius of curvature of from 1500 mm up to 4400 mm (with a relative aperture A=1:8 And=1:16), maximum residual aberration working branch of the interferometer λ/48;

the concave spherical surface of radius 11000 mm up to 17000 mm (with a relative aperture A=1:11 and A=1:44), maximum residual aberration working branch of the interferometer λ/74;

a flat surface with a diameter from 250 mm to 1000 mm, maximum residual aberration working branch of the interferometer λ/124;

1. Interferometer to measure the shape of convex, concave, spherical and flat surfaces of large optical components containing consistently located the source of monochromatic light, telescopic system and the lens, forming a lighting branch, as well as a beam splitter, a reference surface, the compensator controlled surface and Supervisory branch, which is installed behind the beam splitter in reverse the course of the rays, characterized in that the interferometer is further introduced flat mirror, changing the direction of the optical axis and installed after the beam splitter, atlanticheski meniscus with a reference surface facing the compensator, designed to move large fixed stationary spherical mirror, consistently for which you are controlled item, while lighting a branch, a beam splitter, a flat mirror, the submarine is nationsi meniscus with the reference surface and the Supervisory branch form the base unit, made with the possibility of relative displacement him and compensator along the optical axis, a relatively large spherical mirror at such distances at which the rays reflected from the large spherical mirror fall on the controlled surface perpendicularly.

2. The interferometer according to claim 1, characterized in that the control flat surface it introduced the second expansion set for the first compensator at this distance, at which the rays reflected from the spherical mirror, falling perpendicularly on controlled flat surface.



 

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