RU1810753C - Recirculating light range finder - Google Patents

Abstract

Usage: measuring technique. The inventive recirculating range finder contains 1 trigger unit (1), 1 radiation source (2), 2 radiation receivers (3, 7), 2 delay lines (4, 11), 1 computing unit (5), 1 spectral selector ( 6), 2 pulse shaper (8, 9), 1 trigger (10), 1 AND element (12), 1 OR element (13), 1 current source (14). 1-13-4-2, 6-3-8-10-5-1, 6-7-9-10-13, 8-11-12-1, 9-12-5-10. 2 ill.

Description

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The invention relates to rangefinder devices and can be used in geodesy, construction, and installation of large engineering structures.

The purpose of the invention is to increase the accuracy of distance measurement.

In FIG. 1 shows a functional diagram of a device; in FIG. 2 are timing diagrams illustrating its operation.

The device contains a serially connected trigger unit 1, OR element 13, a first delay line 4, a radiation source 2, the second input of which is connected to a constant current source 14, and a spectral selector 6, the outputs of which are optically coupled to radiation receivers 3.7 connected through pulse shapers 8, 9 to the S- and R-inputs of trigger 10, the output of which is connected to the input of the OR element 13, element And 12, the second delay line 11, the computing unit 5, the counting inputs of which are connected by the output of the trigger 10, and the information - with exit lementa and 12.

For a better understanding of the invention, I will first take into account the operation of radiation source 2. A semiconductor laser is used as the radiation source in the inventive device. The current source 14 sets a constant current through the laser diode, the value of which slightly exceeds the threshold value at which the generation of laser radiation begins. If then pulses with a duration of 50-100 ns are applied to a constant bias, then during the action of an electric pulse, the laser begins to shine in a different spectral region, i.e. in the absence of a pulse, the laser emits at a single wavelength A2, and when a pulse is applied, it emits at a wavelength AI where Ar At (during the action of the pulse, the emission spectrum shifts to the short-wavelength region).

In FIG. 26 shows laser radiation at a wavelength; FIG. 2c - at the wavelength Ki. The difference Aa -Ai can reach a value of 50-100 A.

Let us proceed to the description of the operation of the claimed device at the initial time by the external trigger signal, the trigger unit 1 generates a pulse (Fig. 2a), which, through the OR element 13 and delay line 4, enters the radiation source 2. The current source 14 sets the laser operation mode DC so that it continuously generates a laser-kpe radiation. At the moment of the trigger pulse, trigger 10 is also reset to zero

0

5

0

5

0

5

0

5

C-input, and the computing unit returns to its original state. The optical radiation of the laser 2 reflected from the object falls on the spectral selector 6, in which the radiation is spatially divided into two beams, in one of them the radiation with a wavelength of AI is concentrated (Fig. 26) and hits the radiation receiver 3, in the other with a wavelength of Aa (Fig. 2c) and hits the radiation receiver 7.

The spectral resolution of these systems is such that it is possible to isolate the components of the emission spectrum located at the intermode distances, i.e. 5-10 A. After registering optical pulses under a positive voltage drop at the outputs of radiation receivers 3, 7 (from log. O to log. 1), pulse shapers 8, 9 generate pulses (Fig. 2d, e, respectively), which in S - trigger 10 is switched to the R inputs, so that a pulse is generated at its output (Fig. 2g), the duration of which is equal to the difference between the times of arrival of optical pulses from the distance with different radiation wavelengths AI and A 2. Electric pulse from the output of trigger 10 then through the element OR 13 and the delay line 4 enters the bl ok 2 and the optical pulse at the AI wavelength is again sent to the distance. Consequently, a recirculation process will be established in the system, the period of which will be determined by the delay of radiation at a distance and a constant electric delay, determined by the duration of the delay in line 4.

Thus, during the action of an electric pulse, an optical pulse is sent to the distance at a wavelength, after the end of the electric impulse, radiation with a wavelength of AH is sent to the distance. Since the speed of propagation of optical radiation in air depends on the wavelength, with AA AA, there will be more delay at the radiation distance with wavelength AI than with A2.

The difference in optical delay is:

0

5

D1

()(1)

SS

where L is the measured distance;

C is the speed of light in vacuum;

u, pa are the refractive indices of air at wavelengths AI, A2.

Consequently, the front of an optical pulse with a wavelength of A2 will come from a distance earlier than the decay of a pulse with a wavelength of AI by A g (Fig. 26, c), and the pulse duration at the output of trigger 10 each recirculation period will be

decrease by At (Fig. 2g). At the initial time, the trigger unit 1 generates a pulse of duration T + 1z, where 1s is the delay time of line 11. Each recirculation period, the pulse duration at the output of trigger 10 decreases by At, and when it becomes equal to 1z at the inputs of element And 12, the pulses coincide (Figs. 2e, e) and at its output a pulse (Figs. 2h) hits the trigger unit 1, from which the initial pulse duration will be applied to the radiation source 2. The signal from the output of the element And 12 is also fed to the information input of block 5, where the calculation of the value of At by the following formula

At

N

(2)

where N is the number of recirculation periods from the moment of start up to the moment of occurrence of a pulse at the output of element And 12.

When starting from the output of element 12, block 1 generates a pulse of duration T and, in recirculation mode, it is summed in element OR 13 with a pulse of duration ta from the output of trigger 10, and thus the triggering pulse is T + tz. With an external start-up, at the initial moment of time, block 1 generates a pulse T + T3 and, therefore, the trigger pulse at the input of radiation source 2 always remains the same.

I will take a look at the algorithm of the computing unit 5.

It determines the optical delay time and, therefore, the distance to the object from the value of the recirculation frequency, and the average speed of radiation propagation along the observation line, which is taken into account when calculating the range result, is found from the difference in optical delays at different wavelengths. This happens as follows. The fair ratio is:

ni Amp. n0 5b () where no, ni are the refractive indices of air for the wavelength Ah at standard temperature (the value is taken from the reference book) and under the measurement conditions, respectively;

And By, Asch are the refractive index differences at the wavelengths of A2, AI at standard temperature and under measurement conditions, respectively.

Taking into account (3), the range is calculated by the formula:

where torn is the delay time at the radiation distance with wavelength AI.

In this formula, the quantities n0, nn0. C are known and taken from the reference book, t0m is determined by the recirculation frequency, the value of Ani is found from formulas (1), (2) after small mathematical transformations

10

For,, -.

i -torn

(5)

Since in formula (5) the value of At with a relative error is better than 10 -10 is practically difficult to determine, the value of ni should be taken with the same

error, i.e. no need to consider temperature dependence.

Therefore, the computing unit 5 contains two counters, one of which measures the recirculation frequency, and the second — the number of recirculation periods before the pulse appears at the output of the And 12 element, as well as a microprocessor-based computational circuit that mathematically processes the obtained information using

formulas (2), (4), (5).

Thus, thanks to the use of the original mode of operation of the radiation source and the introduction into the device of the blocks of the spectral selector, the second

receivers of radiation, two pulse shapers, a trigger, and others, it is possible to obtain information on the propagation velocity simultaneously with the distance measurement device in the inventive device

Claims (1)

radiation along the observation line and take its value into account when calculating the distance from the magnitude of the optical delay, which increases the accuracy of measuring distances. The claims A recirculating light-range finder comprising a trigger unit, a radiation source, a first radiation receiver, a first delay line and a computing unit, characterized in that, for the purpose of To increase accuracy, it is equipped with a spectral selector installed in front of the first radiation receiver, a second radiation receiver optically coupled to the spectral selector, first and second pulse shapers, the inputs of which are connected respectively to the outputs of the first and second radiation receivers, and a constant current source connected with a radiation source, a second delay line, elements OR, AND and a D-trigger, the D-input of which is connected to a common bus, S- and R-inputs, respectively, with the outputs of the first and second form irovateley pulses, P-input - to the input the reset of the computing unit and the external trigger input of the trigger unit, and the output of the D-trigger is connected to the counting inputs of the computing unit and the input of the OR element, the second input of which is connected to the output of the trigger unit, and the output through the first delay line to the radiation source, the output of the first pulse shaper through the second delay line is connected to the first input of the And element, the second input of which is connected to the second pulse shaper, and the output is connected to the input of the trigger unit and the information input of the computing unit. L. FIG. 2