RU2455668C2 - Video autocollimator - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: video autocollimator has a lens, an autocollating mirror, a beam-splitting unit, an illuminator, a reading device, as well as a test mark and a photodetector, lying in focal planes of the lens. An image of the test mark reflected by the beam-splitting unit is directed by the lens onto the autocollimating mirror, reflected therefrom and then projected by the same lens through the beam-splitting unit onto the photodetector. The photodetector has a CCD array with a standard video signal generating device. The reading device is in form of a computer with a video processor and an application program for calculating the angular position of the autocollimating mirror. The test mark is in form of a circular window whose diameter is calculated using the formula

where ρ" is the conversion of radians to angular seconds, M is the effective size of the CCD array in mm, K is the number of video frames processed in the measurement, f' is the focal distance of the lens in mm, N is the number of discrete units selected on coordinate axes of the video frame, Δφ is the permissible error in angular seconds.

EFFECT: easier manufacturer and operation.

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Description

The invention relates to the field of technical physics and, in particular, for measuring the angular position of an autocollimation mirror.

Known optical autocollimators based on the visual measurement principle / 1 /. These, in particular, include the widely used AKU-1, AKU-0.5, and AKU-2.5 autocollimators, respectively, with a resolution of 1, 0.5, and 0.25 arc seconds. They contain an illuminated cross-hair test mark mounted in the focal plane of the lens. The image of the test mark with the lens in parallel beams of light is sent to the autocollimation mirror, reflected from it, returned to the lens and projected through a beam splitting unit onto a special scale, also installed in the focal plane of the lens. The scale, as a rule, is made in the form of a grid of threads. An image of a test mark is projected onto it, which is examined using an eyepiece. Measurements are performed by determining the position of the image of the test mark (crosshair) relative to the scale, which is proportional to the desired angular position of the autocollimation mirror.

The main disadvantage of optical autocollimators is the visual measurement principle without the possibility of automation.

Also known are photoelectric autocollimators based on an automated measurement principle / 2 /. They also use test marks in the form of slits, the images of which are projected onto two photodetectors through two measurement channels, which makes it possible to determine the angular positions of the autocollimation mirror in two mutually perpendicular planes (vertical and horizontal). The signals of the photodetectors are controlled by two servo mechanisms that work out the positions of the images of the test marks on the photodetectors so that they take a certain “zero” position. The measurement results are output codes of two displacement sensors associated with servomechanisms. For phase separation of measurement channels, the autocollimator is equipped with an electromechanical light modulator.

The disadvantage of the photoelectric autocollimator is the complex optical and kinematic schemes.

The closest to the claimed invention in terms of features (prototype) is an AF-1C type photoelectric autocollimator equipped with two measurement channels, as a result of which it contains a test mark in the form of two crosshairs, a light modulator, two photodetectors, two servomechanisms and two code position sensors. Based on the signals of the photodetectors, the servomechanisms work out the “zero” position of the images of the test mark in the directions of the coordinate axes, and the output codes of the displacement sensors proportional to the angular positions of the autocollimation mirror in the directions of these axes (in horizontal and vertical planes) are used.

The prototype has inherent disadvantages associated with complex optical and electromechanical components.

The problem solved by the present invention is to eliminate these drawbacks by simplifying the optical assembly, eliminating the electromechanical assembly containing light modulators and servomechanisms, and simplifying the test mark.

To solve this problem, in the proposed video autocollimator containing an autocollimation mirror, a lens, a beam splitter, an illuminator, a reading device, as well as a test mark and a photodetector installed in the focal planes of the lens so that the image of the test mark reflected by the beam splitter, the lens is directed to an autocollimation mirror is reflected from it by the same lens and is projected onto a photodetector through a beam splitter, characterized in that the photodetector contains a CCD from devices om the formation of a standard video signal, the reading device is made in the form of a computer with a video processor and an application program for calculating the angular position of the autocollimation mirror, and the test mark is made in the form of a round window, the diameter of which is calculated by the formula:

,

,

where ρ ″ is the conversion factor of radians in arc seconds;

M is the effective size of the CCD in mm;

K is the number of video frames processed in the measurement;

f ′ is the focal length of the lens in mm;

N is the number of samples allocated along the coordinate axes of the video frame;

Δφ is the permissible error in angular seconds.

The invention is illustrated in Fig. 1, which shows a device for generating a standard video signal 1 with a CCD matrix 2, a illuminator 3 in the form of a semiconductor LED, a test mark 4 in the form of a round window, a beam splitter 5, a lens 6, a computer 7 with a video processor 8 and an applied program, as well as an autocollimation mirror 9.

Video autocollimator works as follows.

The image of the test mark 4, reflected by the beam splitting unit 5, by the lens 6 in parallel rays of light is directed to the auto-collimation mirror 9, is reflected from it by the same lens 6 through the beam splitter 5 is projected onto the CCD matrix 2, on the basis of the signals of which the device 1 is formed Aircraft standard video signal containing the image of the test mark.

When changing the angular position of the autocollimation mirror 9 relative to the optical axis of the video autocollimator, the coordinates of the image center of the test mark in the video frame change, which serves as the basis for the measurements.

The measurements are performed under the control of the applied computer program, and the video signal is converted from analog to digital by the video processor 8, the coordinates of the contour points of the round image of the test mark in the video frame are determined, based on these coordinates, the coordinates of the center of the image of the test mark in the video frame are calculated and based on the latter coordinates - the desired angular position of the autocollimation mirror 9 relative to the optical axis of the video autocollimator.

The proposed video collimator in comparison with the prototype contains a simpler optical unit and a test mark. As a photodetector, it uses a modular camera with a CCD matrix, which generates a standard video signal with the image of a test mark. Mentioned modular cameras are produced on an industrial basis and in bulk, which ensures their high reliability and low cost. Working with a standard video signal allows you to transmit it on standard television channels, including satellite, at any distance. Typical devices can be used as a video processor - controllers, frame grabbers and video blasters, also produced on an industrial basis and in bulk.

The round window of the test mark in comparison with a window of any other shape has the advantage that when scanning television lines of a round image in a video frame, the coordinates of its center do not change when the image is rotated.

With an increase in the diameter of the round window of the test mark, the error of the video autocollimator decreases, but the range of angular measurements decreases, which is why the diameter calculated by the above formula is optimal.

For example, for M = 4.8 mm, f = 200 mm, N = 767, K = 16, and Δφ = 0.1 ang. sec we get D≈0.8 mm.

Information sources

1. Spiridonov A.I., Kulagin Yu.N., Kryukov G.S. Directory - a catalog of geodetic instruments. M .: Nedra, 1984, p.202.

2. Afanasyev V.A., Zhilkin A.M., Usov V.S. Autocollimation devices. M .: Nedra, 1982, p. 103.

Claims (1)

A video autocollimator containing a lens, an autocollimation mirror, a beam splitter, an illuminator, a reading device, as well as a test mark and a photodetector installed in the focal planes of the lens so that the image of the test mark reflected by the beam splitter, the lens is directed to the autocollimation mirror, is reflected from it and with the same lens through a beam splitting unit it is projected onto a photodetector, characterized in that the photodetector contains a CCD with a device for generating a standard video signal la, reading device is designed as a computer with a video processor and the application program for calculating the angular position of the autocollimation mirror, and a test mark is formed as a round window of a diameter calculated as follows:

where ρ '' is the conversion factor of radians in arc seconds;
M is the effective size of the CCD matrix, mm;
K is the number of video frames processed in the measurement;
f 'is the focal length of the lens, mm;
N is the number of samples allocated along the coordinate axes of the video frame;
Δφ is the permissible error in angular seconds.