RU1788459C - Method and device for holographic interferometry - Google Patents

Abstract

SUMMARY OF THE INVENTION: the device comprises a sequentially installed light source, a condenser system, a reference hologram, a beam splitter, an optical filtering system including a wrapping system, a spatial frequency filter and a flat mirror, the plane of which is optically coupled to the reference and object holograms, and the normal to the mirror surface coincides with the optical axis of the device, a receiving part including an object hologram, lenses, a filtering diagram and a recorder, an optical receiving part cally bonded to the optical filter system using a beamsplitter. 2 s.p. f-ly, 1 ill. with C

Description

The invention relates to the use of holography in measurement technology.

A method of holographic interferometry is known, based on the registration of a reference (without an object) and object holograms and subsequent restoration of the + n-th diffraction orders. This method is widely used for reconstructing a non-aberration wavefront or for rewriting holograms. To implement the methods, a wavefront study apparatus is used, comprising an illumination part including a light source, a condenser system and a reference hologram, an optical filtering system including a reversing system and a spatial frequency filter, a receiving part.

including an object hologram, lenses, a filtering aperture and a recorder, the reference hologram and object optically coupled.

The disadvantages of the known technical solutions are that the beams reconstructed from the reference hologram in complex conjugate diffraction orders pass the wrapping system in different ways. If there are aberrations of the elements of the wrapping system, then when the interference pattern is obtained, the latter are distorted by aberrations, which reduces the accuracy of measurements.

An object of the invention is to increase speed.

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The drawing shows an optical diagram of a device for implementing the method of holographic interferometry.

The device comprises a lighting part, including a light source 1, a lens system 2,3 with an aperture 4, representing a condenser system, and a reference hologram 5, an optical filtering system, including a reversing system (lenses b, 7) with a magnification of 1x and a spatial frequency filter 8 with two holes, as well as a flat mirror 9, the plane of which is optically connected by lenses 6.7 with a hologram 5, and the normal to the surface of the mirror coincides with the optical axis of the device. The receiving part of the device is brought out from the optical axis using a beam splitter 10 and contains an object hologram 11, lenses 12, 13 and a diagram 14 for separating the diffracted wave and optical coupling of the recorder 15 with the holograms 5, 11.

The method of holographic interferometry is implemented in the device as follows. Using light 1 and a condenser system 2, 4, 3, a collimated beam of light is formed and the reference hologram 5 is illuminated. The amplitude transmission of the reference hologram has the form

 + cos (27tv0x), (1) where 10 is the carrier frequency of the bands; p0 — phase change caused by aberrations of the hologram registration system. In the + n-th diffraction orders, complex conjugate waves with complex amplitudes are restored

 (nx + n)

 (-2 Jtv0 nx - n p0) (2) Waves with amplitudes A0 and are distinguished by an optical filtering system. We denote by tr Y- and V- V-4 the phase changes of the wave caused by aberrations when they pass through the wrapping system, i.e. lenses 6 and 7 (see drawing). In the plane of mirror 9, the complex wave amplitudes have the form

AI (2 1 0 nx + n po + V-., + VV i

А Л (-2jri 0 nx-n - + т /; + /;) (3) Since mirror 9 is optically conjugated with holograms 5 and 11, and the normal to the reflecting surface coincides with the optical axis of the device, it is reflected from the mirror 9, wave A i, will pass the wrapping system exactly along the path passed by wave A 1 Accordingly, the wave will be reflected from the mirror 9 and will pass the wrapping system exactly along the path passed by wave AL At

5 10 15 0

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In this case, the phase distortions caused by the aberrations of the wrapping system will acquire the same values for the waves, and in the plane of the object hologram 11 the complex wave amplitudes will be described by the expressions

A2 -. (+ V; 1 + V + V-5 + Y

(-2jrv0 nx- r (p0 + $ s + V-S + V- 0

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The amplitude transmission of an object hologram has the form:

G0; 1 + C0s (2jri 0 + p0 + Co) (5)

where EO is the phase distortion caused by the passage of the wave through the studied object. When a hologram with amplitude transmittance r0 is illuminated by waves with complex amplitudes described by expressions (4), waves with complex amplitudes are restored normal to the object hologram in + n-th orders

In ex p i (nk0-I /, h + V-2 + V3 + / 1) 1 V. - (-nЈ0 + / Я + / - 4 + V-5 + V-i) 1 (6) Waves (6) are extracted by the optical system 12, 13 and diaphragm 14, and their interference with the intensity distribution is observed in the plane of the recorder

I 1 + cos (2n EO) (7) As can be seen from expression (7), in the resulting interference pattern, aberrations of the wrapping system are completely excluded.

In order to implement the method of accumulating sensitivity when rewriting holograms, a photographic plate is installed instead of hologram 11, and a secondary hologram, for example, a reference hologram, is recorded during interference of waves with complex amplitudes A2 and A2 (see expression (4)). The amplitude transmission of the secondary hologram has the form

T2 --- 1 + jiv0 nx t- 2n +. (9) As can be seen from expressions (8), (9), aberrations of the wrapping system are completely excluded. The elimination of aberrations of the wrapping system reduces the amount of residual aberrations in the final interference patterns and thereby contributes to the goal - improving measurement accuracy.

Claims (2)

SUMMARY OF THE INVENTION 1. A method of topographic interferometry, which comprises recording the reference and object holograms, reconstructing complex conjugate waves in the + n diffraction order from the reference hologram by filtering and passing them through the reversing system, compensating for the aberration of phase distortions introduced by the reversing system , by double passage of diffracted beams through this system along one path, and directions of complex conjugate waves to the object hologram, distinguishing - so that, in order to increase the speed, when the diffracted beams pass through the wrapping system again, the diffracted beam is directed in the + n order of diffraction along the path of the beam diffracted in-order and the beam diffracted in-order are guided along the path of a beam diffracted in a + n order. 2. A device for recording holographic interferograms, comprising a series-connected lighting part, including a light source, a condenser system and a reference hologram, an optical filtering system, including a wrapping system and a spatial frequency filter, a receiving part, including an object hologram, lenses, a filtering diagram and a registrar moreover, the reference and object holograms are optically conjugated, which is related to the fact that, in order to increase the speed, the optical system At the output of the wrapping system, a flat mirror is introduced, the plane of which is optically coupled to the reference and object holograms, and the normal to the mirror surface coincides with the optical axis of the device, a beam splitter is installed behind the reference hologram, which optically connects the optical filtering system and the receiving part.