SU1504496A1 - Linear displacement dtransducer - Google Patents

Abstract

The invention relates to a measurement technique and can be used to measure the movement of objects in two coordinates. The purpose of the invention is to increase the sensitivity of the sensor by increasing the magnitude of the useful signal. A radiation source through a capacitor 2 illuminates with a parallel beam an area 6 of the transmissive diffraction grating. The zone of the transmissive grating and the reflective two-dimensional diffraction grating associated with the object to be controlled are made with a periodic structure in the form of square elements arranged in a checkerboard pattern with diagonals equal to the period of the structure and directed parallel to the coordinates of the controlled movements. As a result of diffraction on the elements 14 of the lattice zone 6, a set of diffraction orders is formed, which, reflecting the diffraction on the elements 14 of the reflective lattice, fall into groups of 4 and 5 strokes of the transparent transmitting lattice 3 arranged in a crosswise manner. perpendicular to the strokes of another group and directed along the coordinates of the controlled displacements. With the help of the collecting lenses 9-12, the radiation diffracted on the lines of groups 4 and 5 of the transmissive grating is focused on the photosensitive areas of the photodetectors. By rotating the optical wedge 7 in two mutually perpendicular planes, a phase shift equal to ϕ / 2 is achieved, the signals at the outputs of the photoreceivers of each pair are set in the directions of the measured displacements, then the changes in the signals from the photoreceivers are judged . 3 il.

Description

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on elements 14 of the reflective lattice, groups of 4 and 5 strokes of the transparent transmission lattice 3 are located crosswise. The strokes in each of groups A and 5 are oriented perpendicular to the strokes of the other group and are directed along the coordinates of the controlled movements. With the help of collecting lenses 9-12, the radiation diffracted on the strokes of groups A and 5 of the transmitting grid

The invention relates to a measurement technique and can be used to measure the movement of objects in two coordinates.

The purpose of the invention is to increase the sensitivity of the sensor by increasing the magnitude of the useful signal.

FIG. Figure 1 shows the optical layout of the linear displacement sensor; in fig. 2 shows section A-A in FIG. one; in fig. 3 - structure of two-dimensional diffraction gratings: a) a prototype, b) the proposed device

The linear displacement sensor contains a radiation source 1 and a successively located along the radiation path a condenser 2, mounted with a fixed transmissive diffraction grating 3, filled with two crosswise arranged groups of 4.5 strokes, the strokes in the group are oriented perpendicular to the strokes of the other group, and the intersection zone 6 of the strokes is optically associated with the condenser 2, the optical wedge 7, installed so that its main section is an angle of 45 with strokes of the grating 3, a reflective two-dimensional diffraction grating 8, intended for communication with a controlled object, collecting lenses 9-12 and photolresectors 13, located on one side of the array 3 with a radiation source 1 and a condenser 2 and optically associated with crosswise arranged groups of 4 and 5 strokes.

The reflecting diffraction grating 8 and the zone 6 of the transmissive diffraction grating 3 are made with a periodic structure in the form of square square staggered blocks.

focuses on photosensitive photodetector sites. By reversing the optical wedge 7 in two mutually perpendicular planes, a phase shift equal to T / 2 is achieved, the signals at the outputs of the photoreceivers of each pair are set in the directions of the measured displacements, then, by the changes in the signals from the photoreceivers, displacement 3 Il.

elements with diagonals equal to the period of the structure and oriented parallel to the stroke-groups 4 and 5 of the lattice 3.

The sensor works as follows with

1 radiation source located

in the focal plane of the condenser 2, illuminates by a parallel beam the zone 6 of the transmissive grid 3. The lines of groups 4 and 5 are oriented perpendicular to the corresponding directions

measured displacements. As a result of diffraction of light on the elements 14 of the structure of zone 6 of the transmissive diffraction grating 3, a set of diffraction orders is formed, which,

reflecting and diffraction on the elements 14 of the structure of the diffraction grating 8 fall into groups 4 and 5 of the strokes of the transparent grid 3. With collecting lenses 9-12, the radiation that has passed through and diffracted on the lines of groups 4 and 5 of the grid 3 is focused on the photosensitive areas of the photodetectors 13.

By turning the optical wedge

7, in two mutually perpendicular planes, a phase shift of 2 is obtained, the signals at the outputs of the photodetectors 13 of each pair are set in the directions of measurement of

From FIG. 2 that the luminous flux falling on one of the photodetectors 13 consists of the sum of two light fluxes formed in

the result of three interactions of radiation from light source I with diffraction gratings.

So, the first light flux after the first diffraction on the structure of zone 6 of the transparent grating 3 goes in the direction of the zero diffraction order, after the second diffraction on the structure of the reflective grating 8 goes in the direction of the first diffraction order, after the third diffraction on the structure of groups A and 5 of the transparent grating 3 goes in the direction of the first order of diffraction.

The second light flux after the first diffraction on the structure of zone 6 of the transparent grating 3 goes in the direction of the first diffraction order, after the second diffraction in the direction minus the first diffraction order after the third diffraction in the direction of the bullet diffraction order.

Based on the known relations describing the interaction of light radiation with a periodic structure, in accordance with Fraunhofer diffraction, it was found that the ratio of the amplitudes of the change in intensity of light fluxes falling on the photodetectors 13 for this device and the prototype is different from A: 1.

Thus, the implementation of transmissive and reflective structures of two-dimensional diffraction gratings of square elements arranged in a staggered order, turned at an angle A5 relative to the direction of the measured displacements, makes it possible to increase the value of the useful optical signal to the photodetectors by more than 4 times, which increases the threshold value

light sensitivity of the linear displacement sensor.

Claims (1)

Invention Formula A linear displacement sensor containing a radiation source and a successively arranged along the radiation condenser, a fixed transmissive diffraction grating made with two groups of strokes arranged crosswise, the strokes in the group are oriented perpendicular to the strokes of the other group, the optical wedge installed so that its main section is em angle 45 with the strokes of the transmission diffraction grating, a reflective two-dimensional diffraction grating intended for communication with a controlled object, collecting lenses and photodetectors located on one side of the transmissive diffraction grating, with a radiation source and a capacitor and optically associated with crosswise-arranged groups of strokes. characterized in that. thirty 35 In order to increase the sensitivity of the sensor, the reflective diffraction grating and part of the transmissive diffraction grating, optically connected to the condenser, are made with a periodic structure in the form of square elements arranged in a staggered pattern equal to the structure period and parallel to the 4Q strokes that start up diffraction grating.  - K- f ( . 2 fie.Z