SU1733920A1 - Scanning interferometer - Google Patents

Abstract

The invention relates to a measurement technique and can be used in an apparatus for recording and reading an image with a scanning laser beam. The purpose of the invention is to improve the accuracy of recording the angle of rotation of an object by increasing the signal-to-noise ratio. The laser beam 1 is focused by the first component 2 of the collimator and is divided into two divergent coherent beams using the diffraction grating 3. The beams are collimated by the second component 4 of the collimator and focused by the objective 5 through the deflector 6 on the surface of the concave diffraction grating 7. Reflected K diffraction order from each beam is directed in one direction to the photodetector 8. A change in the angular position of the deflector 6 leads to a change in the signal at the output of the photodetector 8. 1 sludge.

Description

The invention relates to a measurement technique and can be used in a device for recording and reading images by a scanning laser beam.

A scanning interferometer is known, comprising a sequentially optically coupled laser, a system for forming coherent, spatially separated beams, a deflector, a Michelson interferometer, part of which are angular reflectors mounted on the deflector mirror, and a photodetector unit.

A disadvantage of the known interferometer is the nonlinearity of its scale.

Closest to the proposed technical entity is a scanning interferometer containing a sequentially optically coupled laser, a beam shaper, consisting of a translucent and a deaf mirror, an objective lens, a deflector, a diffraction grating, and a photodetector.

A disadvantage of the known device is comparatively low accuracy, limited by the effect of the diffraction grating defects formed both in the process of its manufacture and during operation, and by the signal-to-noise ratio on the photodetector.

The aim of the invention is to increase the accuracy of recording the angle of rotation of the object by reducing the effect of the defects of the diffraction grating and increasing the signal-to-noise ratio at the photodetector.

This goal is achieved by the fact that a scanning interferometer containing successively installed laser, lens, deflector, designed to communicate with an object, a concave diffraction grating and a photodetector, is equipped with a collie 1

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a matrix installed between the laser and the lens, and a diffraction grating installed between the components of the collimator in a plane optically conjugated with a concave diffraction grating.

The drawing shows a scanning interferometer.

The interferometer contains a series 1 optically coupled laser 1, the first component 2 of the collimator, the diffraction grating 3, the second component 4 of the collimator, the lens 5, the deflector 6, the concave diffraction grating 7 and the photodetector 8, the center of the concave diffraction grating 7 coinciding with the center of oscillation of the deflector 6, and the diffraction grating 3 and the concave diffraction grating 7 are located in the optically conjugate planes, which are the front focal plane of the second component 4 of the collimator and the rear focal plane o Lens 5.

The output of the photodetector 8 is the output of the interferometer.

The device works as follows.

The first component 2 of the collimator focuses the laser radiation 1 at a distance of 6i to the diffraction grating 3, which divides it into two beams. At the same time, at the output of the second collimator component 4, two coherent light beams are formed, the axes of which are parallel to the optical axis. Lens 5 and deflector 6 direct these beams to a concave diffraction grating 7, where they form two fully overlapping light spots with a diameter d. On a concave diffraction grating 7, the light beams diffract in this way, the maximum diffraction of one beam and the kth diffraction maximum of the other beam coincide in the direction of propagation. These maxima are directed by the deflector 6 and lens 5 to the photodetector 8, where they interfere with each other. When moving the light beams along the concave diffraction grating 7 caused by the oscillations of the mirror of the deflector 6, the position of the light spot on the photodetector 8 remains unchanged, and the intensity of the light flux falling on the photodetector 8 causes the corresponding changes in the signal at the output of the latter. The counting of pulses at the output of the interferometer makes it possible to determine the position

light spots on the concave diffraction grating 7 and thereby the spatial position of the deflector mirror 6.

In the proposed device, unlike the prototype, the centers of the diffracting beams on the concave diffraction grating 7 coincide and the interfering beams propagate in one direction regardless of the distance between the surface of this grating and the diffracting beam diffraction beams dz This allows the diameter of the light spots to be increased by a concave diffraction the grating 7, without reducing the width of the interference band on the photodetector 8. Large size

the spot on the concave diffraction grating 7 reduces the effect of its defects on the output waveform, and the large width of the interference band, which in the proposed device can occupy the entire

the area of the photodetector makes it useful to use most of the laser radiation energy and thereby increase the signal-to-noise ratio.

Claims (1)

Invention Formula A scanning interferometer containing a successive laser, an objective lens, a baffle intended for communication with an object, a concave diffraction grating and photodetectors, which are provided with the aim of improving the accuracy of recording the angle of rotation of the object the collimator installed between the laser and the lens and the diffraction grating installed between the components of the collimator in the plane optically conjugated with a concave diffraction grating.