SU706694A1 - Photoelectronic automatic collimator - Google Patents

Description

(54) PHOTO-ELECTRIC AUTO-COLLIMATOR

I

The invention relates to a measurement technique and can be used for angular measurements in optical manufacturing, precision engineering, geodesy, and the like.

Known photoelectric autoclimators containing modulators of various types 1.

The disadvantage of these devices is their limited use for measurements in dynamics, since the period of the modulation frequency must be much shorter than the duration of the impulse at the output of the photodetector, which is determined by the speed of rotation of the object.

The closest in technical essence and the achieved effect to the invention is a photoelectric autocollimator, containing. An optically coupled light source, objects, a beam splitter, a photoreceiver, and two identical masks located in the focal planes of the lens, one between the light source and the beam splitter, and the other between the beam splitter and the photoreceiver 2.

A disadvantage of the known device lies in the low measurement accuracy, since

as the size of the gap in the mask decreases, the light signal becomes difficult to distinguish against the background of the noise.

The purpose of the invention is to increase the accuracy of measurements.

This goal is achieved by the fact that the masks are executed as a set of elements whose transparency regions form a pseudo-plague sequence.

FIG. I depicts a schematic diagram of the proposed autocamp; in fig. 2 is a graph of the nature of the distribution of areas of transparency over the area of masks; in fig. 3 - view of the autocorrelation functions for the masors of the proposed configuration and slot masks.

five

The device contains a source of light 1, matching optics — capacitors 2 and 3, amplitude masks 4 and 5, lens 6, a beam splitter 7, a photographic terminal 8. The element of the pseudo-optic sequence in masks 4 and 5 is a square hole with a side r (see Fig. 2).

Claims (2)

The device works as follows. The light flux from the source, passing through the condenser 2, illuminates the mask 4 located in the focal plane of lens 6, and after the beam splitter 7 with a parallel beam falling onto the reflecting surface 9 of the object being monitored. Reflected from surface 9, the light beam returns to lens 6 and falls onto the second mask 5, reproducing the image of mask 4 on its surface. After passing through mask 5, the condenser 3 collects light on the sensitive area (cathode) of the photodetector 8. If surface 9 is tilted at an angle a to the main optical axis of the auto-locator, the image of mask 4 is offset from mask 5 by the amount a Ftg2a, where F is the focal length of the lens, the resultant field of the light wave at the cathode of the photodetector 8 can be found in de the product of transmittance of each mask 4, 5 on the field of the original light wave E E, t, (x-a, y) t, (x., y) r (1) where EO is the amplitude of the light wave; r is the surface reflection coefficient 9; t, (xa, y) is the transmittance of mask 4; t (1 y) is the transmittance of the mask 5. Expression (1) forms the basis for you, the number of the autocorrelation function, whose values at the characteristic points corresponding to the mutual shift of the masks 4 and 5 by the value of the np, are KUfn, o) - (I) and in the absence of spatial shift R (0,0) "0.5. 44 The view of ab-10 correl 1 of the 1st function is shown in FIG. 3. Curve B. Curve C is also shown to compare the autocorrelation function for masks on which there is one slot each. As can be seen from curve B, the autocorrelation function of the proposed device is characterized by a sharp drop in its value when masks are shifted 4 and 5 from the original position The peak of the autocorrelation function corresponds to an equivalent slot width equal to the sum of all portions of the transparency of the pseudo-noise sequence, and the peak width corresponds to the width of one element. Thus, the signal-to-noise ratio and, accordingly, the accuracy of the autocollimator can be increased by a number of times proportional to the number of elements of the pseudo-noise sequence. Formula of the Invention A photoelectric autocollimator containing an optically coupled light source, lens, beam splitter, photodetector, and two identical masks located in the focal planes of the lens, one between that, in order to improve the measurement accuracy, the masks are implemented as a set of elements, the transparency areas of which form a pseudoilum sequence. Sources of information taken into account in the examination 1. Yu. M. Golubovsky. Photoelectric autocollimators, OMP, No. 5, 1970. 2. Gukaylr M. Ya. Autocollimation. M., Mashgiz, 1963 ,. with. 81 (prototype). fea-. , - -P1 -t -WI -8f -61 - "t -21 o gt 4" t et l wi whit t ) F «g5