SU1290172A1 - Velocity meter - Google Patents

Abstract

This invention relates to an optical meter for the speed of movement of an extended optically inhomogeneous object. The purpose of the invention is to reduce the speed measurement error. The optical axes of the photodetectors (Φ) are parallel to each other, perpendicular to the surface of object 12 and spaced in the direction of motion over distances that are multiple to the spatial period of the raster photodetector 2. Objectives 1 form, in the plane of the raster photodetector 2, images of different sections of the extended object 12. At the outputs of the differential Amplifiers 3 appear signals with the same for S (L with tffuef

Description

129

all Φ with a frequency proportional to the speed of movement of the object 12 and the phase. The output signals Φ are fed to the inputs of the multichannel phase correction unit 4. If the frequency of the tracking filter 5 is equal to the frequency of the signals with Φ, the outputs of the phase detectors 7 are in terms of the voltage, the polarity of which depends on the phase mismatch of each Φ relative to the signal of the following filter 5. Comparators 8 in the invention relate to the measurement technique and can be used in transportation, in aerial photography and in rolling mills for contactless measurement of the speed of movement of an extended optically inhomogeneous object.

The purpose of the invention is to reduce the speed measurement error.

Fig. 1 shows a functional diagram of the speed meter in Fig. 2, a vector diagram of one of the possible implementations of the signal at the output of the multichannel phase correction unit.

The speed meter contains at least two photodetectors with parallel optical axes, each of which consists of a lens 1, a differential raster photo detector 2 and a differential amplifier 3, a multichannel phase correction unit 4, a tracking filter 5, which is a frequency controlled oscillator with phase locked loop and frequency meter 6. The multichannel phase correction block 4 contains identical channels, each of which includes a phase detector 7, a comparator 8, an electronic switch 9 and two resistors 10 as well as a differential amplifier 11, common to all channels. The number of channels of the multichannel phase correction unit 4 is equal to the number of photodetectors.

The optical axes of the photodetectors are parallel to each other, perpendicular to the surface of the object 12 and spaced apart in the direction of motion by

depending on the polarity of the output signals of the phase detector 7, control signals are generated that bring the electronic switch 9 to the appropriate position. The output of the resulting signal of the differential amplifier 11 is fed to the input of the tracking filter 5, which automatically adjusts to the frequency of the signal. 2 Il.

the multiples of the spatial period of the raster photodetector 2. Differential raster photodetector 2 installed in the image plane of the lens 1, its outputs are connected to the inputs of the differential amplifier 3, the output of which is connected to the signal input of the corresponding electronic switch

a body Y, the control input of which is connected to the output of the same differential amplifier 3 through a series-connected phase detector 7 and a comparator 8, and the normally closed and normally open directions of the electronic switches 9 of all channels are connected through AND-10 the inputs of the differential amplifier 11, the output of which is connected to the input of the tracking filter 5, the output of which, in turn, is connected to the input of the reference voltage of the phase detector 7 in each channel and the input frequency counter a 6.

The speed meter works as follows.

The lenses 1 form in the plane of the raster photodetectors 2 images of different parts of the extended object 12.

As the object 12 moves, the outputs of the differential amplifiers 3 produce sinusoidal signals with the same frequency for all photodetectors, which is proportional to the velocity V of the object 12, and the phase if varies randomly from the photodetector to the photodetector. Would

all photodetector signals

12

served at the multi-channel inputs. block 4 phase correction. If the frequency of the tracking filter 5 is equal to the frequency of the signals from the photodetectors, then the outputs of the phase detectors 7 have a voltage U, the polarity of which depends on the phase mismatch of the signals of each photodetector relative to the signal of the next filter 5, i.e.

and X with S 4.

Comparators 8, depending on the polarity of the output signals of the phase detectors 7, produce control signals that convert the electronic switches 9 to the appropriate positions. In this case, it is indicated that the input And of the differential amplifier 1 through the resistors of 10 isolations are only signals from those channels in which phase mismatches lie in

interval, 2 input NOT signals from all other channels.

The output of the resulting signal of the differential amplifier 1 1 is fed to the input of the tracking filter 5, which automatically adjusts to the frequency of the signal.

The output signal of the tracking filter 5 is used as a reference voltage for the phase detectors 7 and is fed to the input of the frequency meter 6, scaled in units of speed.

Figure 2 (for comparison) shows a vector diagram of signals formed by the intersection of the plane of the optical raster and randomly located optical inhomogeneities.

From the vector diagram (Fig. 2). It is evident that with an arbitrary increase in the size of the field of view of the optical system, i.e. with an arbitrary increase in the number n of photodetectors, in the proposed speed meter, the amplitude A of the resulting signal increases in proportion to n, i.e.

l 2p. BUT,,

where a. - the amplitude of the signal at the photodetector output.

5 o

15 0

five

0

Q

five

0

724

In known devices, with an increase in the field of view in the direction of motion, it is necessary to reduce the measurement error, i.e. with an increase in the number of optical inhomogeneities that simultaneously fall in the field of view, the amplitude of the resulting signal tends to zero (point O tends to point O).

Claims (1)

Invention Formula A speed meter containing a photodetector including a lens, in the plane of the image of which a differential raster photo detector is located, connected by its outputs to the inputs of a differential amplifier, as well as the next filter in the form of a phase locked loop and frequency counter. , characterized in that, in order to reduce the error, n similar photodetectors with optical axes parallel to the optical axis of the first photodetector are inserted into it and spaced in a direction orthogonal to the axis for a distance multiple to the spatial period of the differential raster detector, a multi-channel correction unit including a differential amplifier and n + 1 identical channels in the form of a phase detector, comparator, two isolation resistors and an electronic switch, a signal the input of which is connected to the output of the corresponding photodetector, and the control input is output from the same photodetector via a series-connected phase detector and comparator, normally The closed and normally open directions of the electronic switches of all channels through the isolating resistors are respectively connected to the I and NON inputs of a differential amplifier, the output of which is connected to the input of a follower filter connected by an output to the input voltage of the phase detector in each of the channels and the frequency meter input . ABOUT , TK Editor A.Revin Compiled by Y.Vlasov Tehred L. Serdyukova CorrectionE.Sirohman Order 7893/39 Circulation 798 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, st. Project, 4 / AI - / Ail (puff. 2