SU520507A1 - The device of interference measurement of the projection of the vector of movement of the surface of a diffuse-reflective object - Google Patents

Description

(54) DEVICE FOR INT-ERFEREP-SIZE PROJECTION MEASUREMENT

VECTORS OF DISPLACEMENT OF SURFACES (X; TI DIFFUSIVE; - DANGERING

The OBJECT of one of them is positioned and mechanically combined with another negative, which leads to inaccuracies due to inaccurate combination. The closest technical solution proposed is an interference measurement device for the projection of the surface displacement vector of a diffuse reflecting object, containing a coherent radiation source, a single-channel object lighting system and a two-channel information recording system, each channel of which contains a diaphragm, focusing element 41, radiation receiver { WITH. The introduction of a two-channel information recording system makes it possible to obtain intensity holograms with a carrier spatial frequency and, when reconstructing, separate orders of diffracted wave fields are separated. As a result, the dependence of the contrast of the interference pattern on the reconstructed image on the contrast ratio of the emulsion disappears, which increases the measurement accuracy. The disadvantage of the described device is low sensitivity. The purpose of the invention is to enhance the sensibility of the device. This goal is achieved due to the fact that an optical element is inserted into one of the illumination channels of the object, providing rotation of the polarization plane of the illuminating radiation, an ana / shzator is inserted into the channel of the information recording system, and one of the channels of the information recording system An optical element is introduced that ensures the rotation of the polarization plane of the detached radiation. The drawing shows the principal diagram of the proposed device. The source of coherent radiation and the two-channel illumination system of the object under study 1 in directions 2 and 3 are not shown. The information recording system consists of two channels located in the direction. Ai x 4 and 5. Each channel I contains aperture 6 and 7 in an opaque screen 8, the focusing element 9 representing the optical system (lens or lens) and the radiation receiver 10, which is a quadratic detector, for example, a fsgoplate plate . An optical element 11 is introduced into one of the channels to illuminate1, which provides for the rotation of the plane of the polar and radiated radiation {for example, semi-; wave plate). An analyzer 12 and 13 is inserted into each data frame of the information recording system, and the sttictic element 14 is inserted into one of these channels, which ensures that the polarization plane of the reflected radiation is real. In the process of operation, the deukhkanal system of shading an object under investigation provides ollimated reflux by direction T n 3. Since both of the providing beams are irradiated from the same coherent source, they are located in the same plane, as shown in FIG. 1 by the arrows crossing the directions 2 and 3. After passing the illuminating radiation through the optical element 11, the polarization plane of the illuminating radiation in one of the channels changes to orthogonal, which is shown by a dot in the drawing. Due to the diffuse scattering of the illuminating radiation, in each of the directions 4 and 5, two beams simultaneously propagate with mutually orthogonal polarizations. Analyzers 12 and 13 transmit the radiation of one direction of polarization, so that only one beam spreads out of the channels from the channels, the polarizations of these beams are mutually orthogonal. The optical element 14 rotates the plane of polarization of one of the beams so that it becomes orthogonal with respect to its original position and parallel with the beam in the other channel, resulting in the beams in different channels becoming coherent and polarized and form an interference pattern in the plane of the recorder. Using the method of two exposures and applying a deforming load to the object, interference image is obtained on the reconstructed image HHH, {this represents the isolines of the projection of the displacement vector surface of the diffuse-reflecting object in the direction perpendicular {symmetrical to the bisector between the directions 2 and 3. Let's compare the proposed device with the analogue and the prototype in terms of sensitivity and accuracy characteristics. The analogue uses two-channel illumination of the object under study and a single-channel information recording system, which is located symmetrically to the optical axis, and elements 11–14 are also absent. The interferogram on the reconstructed image is described by an equation; D | r 2sm | - N.Ai (1) - f decL - projection of the displacement vector on the direction perpendicular to the optical axis: - the angle between the optical axis and; directions of illumination of object N

| rd number of interchip band,; A-D: SHNa waves.

With a sensitivity determined by the detection of the formation of a single interference band, one can measure

Vasinji

4G

C2)

when illuminated tangentially to the surface (maximum theoretical sensitivity): 5iriji l, 4fx 2-

In holographic interferometry with illumination normal to the surface and observation tangentially to it (the theoretical maximum sensitivity is idf.. Thus, the analog sensitivity exceeds the sensitivity of 1 olographic interferometer, but the measurement accuracy is unsatisfactory.

In the prototype, a single-channel object lighting system and a two-channel information recording system are used (one of the illuminating beams and elements are missing). The interferogram on the reconstructed image is described by the equation:

 , (3)

where "/. The angle between the optical axis and directions 4 and 5. The effective diameter of the optical system limits the angle e, and hence the sensitivity of the device. It is known that quality objects have a diameter to focus ratio of not more than 1: 1.5, which when photographing

on a scale of 1: 1 gives

SlncC - | - and with M «1, LIH ZL.

Thus, although the accuracy of the prototype is higher, the sensitivity is worse than that of the analog and the holographic interferometer.

; Note that the mechanical combination of one device of a two-channel system {illumination of an object and a two-channel system of recording information does not lead to an increase in sensitivity. Indeed, if the object was illuminated by two channels & lam radiation, coherent and also polarized (elements 11-14, then would be absent), as a result of diffuse scattering on the object's height of the illuminating beams along each of the channels 4 and S two bunches. In the Aalisi Process, a hologram would be intense; they would be formed by the interference of four beams. When recording by the double exposure method with an application to the object under study between the exposure of the deforming load of the image restored

in the zero order of the diffraction pattern, the total 1interference pattern would be divided by the interference of four pairs of beams. As a detailed calculation of such an interference shows, as a result, a low-contrast interference pattern described by equation (3) would be observed on a strong interfering background.

Introducing optical elements 11–14 from four reflected beams separate two that passed through channels 2–4 and 3–5 (or through channels 2–5 and 3–4, if the analyzers 12 and 13 are interchanged), which provides a high contrast interference fringes on the reconstructed image. The interferogram is described by the expression;

Arx (sm i: sinj) "(,) (C)

where the + or - sign corresponds to the interference pattern formed by the beams, par spaces through channels 2-4 and 3-5, or 2-5 and 3-4. The maximum sensitivity in this transfer (at 51Pv (1 Sinjb l) corresponds to 7 interference fringes, which exceeds the sensitivity of the Holographic interferometers, the analog and the prototype.

There are two possible variants of the device, leading to the achievement of the goal,

but with some drawbacks compared with that described.

In the first variant, two channels used to record information are obtained by dividing not by the wave front, as described by the JHOM device, but by dividing by amplitude using a diffraction grating placed in the image plane of an object previously built on one channel by an auxiliary optical system. The interferogram in the reconstructed image is described by equation (1). Compared with the proposed device, in this embodiment, the intensity of the light, falling on a quadratic detector, will decrease by 1 / D times, where D is the diffraction efficiency of the lattice except for togs), as can be seen from a comparison of equations (1) and (4) ), neskopyso sensitivity decreases,

In the second version of the device, both dp lighting and recording channels use two channels, optical elements 11-14 are absent, instead, the time of each of the exposures is divided into two equal intervals, between KOTOpbiNoi and the corresponding optical elements change the phase of one of the illuminating beams, and one of the beams used for dl. , on-l. The intensity hologram turns out to be recorded with the addition of a constant background, which leads to a decrease in its efficiency and is swayed well by the arksyuti of the recovered image.

Claims (3)

1. R. Collier et al. Optical holography. M., World, 1973, 2.Leendertt. 3.A., 1. of PHys.E (Scl - nstinim) 1970, 3, 214-218). 3. Vlasov N. G., Smirnova S., N. Pressuksy Yu, P., Zh. T.F. 1973, №5. 11О41106 (prototype).