SU1500965A1 - Method of generating fringe pattern - Google Patents

Abstract

This invention relates to optical instrumentation, in particular, to holographic interferometry. The purpose of the invention is to improve the quality of the interference pattern by increasing the degree of compensation for aberrations. For this purpose, the reference and object holograms are recorded, the reference hologram is illuminated with one beam of light, and the object hologram is recorded with two beams of light diffracted on the reference hologram. The carrier frequencies for registering the reference and object holograms are different and illuminate the combined reference and object holograms by a light beam. Restored N - th (where N = 1, 2, 3 ...) and the zero diffraction order are returned to the object hologram, while changing the angle between the N - th and zero diffraction orders. Then the object hologram is shifted relative to the reference so as to compensate for the shift of the reflected wave front, and an interference pattern is obtained with full compensation of aberrations in the reverse course of the rays on the object hologram. 2 Il.

Description

This invention relates to optical instrumentation, in particular, to holographic interferometry.

The purpose of the invention is to increase the quality of the interference pattern by increasing the degree of compensation for the aberrations of the recording system,

H FIG. 1 shows the reference hologram 1, the object hologram 2 and the spherical reflectors 3 and 4; in fig. 2 is an optical diagram of an apparatus for carrying out the proposed method;

FIG. 1 and FIG. 2 accept the following notation: 1 and 2 - support and

object holograms, respectively; 3 and 4 - spherical reflectors; 5 and 6 are negative and positive lenses, respectively; 7 - beam splitter; 8 - pinpoint diaphragm; 9-11 - lenses; 12 - screen.

The essence of the method is as follows.

A reference hologram is recorded in a holographic interferometer with smooth starts with a holographic angle d (the angle between the propagation directions of the object and reference waves) and an object hologram with an angle of holographic representation. In that

with

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ate

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In this case, the carrier frequencies on the hologram will be different and equal, respectively, in sin, sin, v, where

0

IP - with

radiation wavelength of the light source illuminating the interferometer. Combine the reference 1 and object 2 holograms (Fig. 1). Then the reference hologram is illuminated along a normal with a beam of light of the same wavelength A. In this case, on the reference hologram in the nth order of diffraction, a wave propagates at an angle of n c /, with recording system aberrations equal to pcSp. Since the holograms are aligned, a diffraction will also be observed on the object hologram. But on an object hologram in the 5th order of diffraction, a wave of diffraction is angled. In the zero order of diffraction, the wave propagates along the normal. This wave does not contain registration aberrations. With the help of the reflector 3, the wave diffracted on the reference hologram in the 5th order is returned, and the object hologram is illuminated by it. In the fifth order of diffraction, a wave is restored on the object hologram, free from register aberrations. and with phase changes caused by the object increased by n times. In order to diffracted in the 5th order on the object hologram, the wave propagates along the normal to the hologram, it is necessary, by tilting the reflector 3, to direct the regenerating wave to the object hologram at an angle to the normal (Fig. 1). In this case, a shift occurs between the corresponding points O and O of the restoring wave front and the object hologram 2. This shift is compensated by the shift of the hologram 2 relative to the hologram 1 until the corresponding points of the restoring wave front and the object hologram1-1y do not match (Figure 1) . In this case, the object holograph | - the wavefront will be restored with full compensation of the registration system aberrations. With the help of the reflector 4, the zero order of diffraction on the object hologram 2 is returned along the normal and the reverse path with the normal to the holograms B receive interference with full compensation of the aberrations of the recording system. Tune the end bands get tilted

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five

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five

about 5

five

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reflector A. If in the prototype method full compensation of the aberrations of the registration system occurred only when tuned to an infinitely-wide band, and when tuned to the final strips, it was necessary to unfold (, the holograms and thereby disrupt the correspondence between the points of the wave fronts reconstructed from the reference and object holograms, in the proposed method, at any setting, the matching is always performed and thus the aberrations of the recording system are fully compensated.

The method is carried out using a device whose optical scheme is shown in FIG. 2, as follows ..

In a holographic interferometer with smooth beams, a reference hologram and an object hologram are recorded with different frequencies (for example, the holograms are then combined and mounted into a device (Fig. 2) containing an illumination system (lenses 5 and 6), a pinhole 8, lenses 9 and 10, hologram combining unit 1 and 2, two spherical reflectors (mirrors) 3 and 4, the foci of which are located in the rear focal plane of the lens 10, a beam splitter 7, a lens 11 and a screen 12, optically matched by a lens 11 with a plane of the node combining a blob - 1 and 2. The interference pattern with an increase in the sensitivity coefficient of the measurements is obtained as follows: Illuminate the device with a laser beam of light.With the help of an illumination system, the beam is expanded to the required dimensions, resulting in a reference hologram illuminated, using a lens 10 near the rear focal plane, diffraction patterns are separated light on the reference hologram. Using spherical reflectors 3 and 4, return the nth and zero order of diffraction from the reference hologram to the object hologram. The reflector 3 changes the angle between the returned nth and zero orders of the diffraction of the action so that the nth order diffracted on the object hologram passes through the hole of the pinhole 8. The resulting shift between the corresponding points of the wave front Returned to the object hologram

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Claims (1)

SUMMARY OF THE INVENTION A method for producing an interference pattern, which consists in recording the reference and object holograms, illuminating the reference hologram with one beam of light, and object-with two beams of light diffracted on the reference hologram, characterized in that, in order to improve the quality of the interference the patterns carrying the frequencies of the reference and object 10 holograms are performed differently; the reconstructed nth and zero diffraction orders are returned to the object hologram; the angle between ⁿ ~ ^m and zero diffraction orders is changed to The e15 magnitude, proportional to the difference in the carrier frequencies, is shifted by the object hologram relative to the reference one, the interference pattern is obtained in the reverse ray path on the object hologram.