SU1714549A1 - Method for determining optical characteristics and device - Google Patents

Abstract

The invention relates to atmospheric photometry and allows one to improve the measurement accuracy of optical characteristics, as well as to simplify the apparatus implementation of the device. The control unit 1 starts single-oscillators 4 and 5 pulses from which the strobe amplifier 10 and photodetectors 8 are controlled. In memory unit 12, the value of the backlight signal is recorded, which is preliminarily detected with a peak detector 11. In the subtraction unit 13, the backscattered electromagnetic signal the pulse emitted to the atmosphere by the block 3 is compensated for by the background. The backscatter signal is differentiated in block 14 and normalized in division block 15. The atmospheric attenuation values are obtained by processing the signal in block 16. 2 s., 1 Cp. File, 2 ill. (Ls

Description

The invention relates to atmospheric photometry and can be used to measure the optical parameters of the atmosphere, and can also be used to control the level of aerosol pollution of natural and artificial origin.

The purpose of the invention is to improve the accuracy of measurements of the optical characteristics of the atmosphere and simplify the hardware implementation of the device.

The method for determining the optical characteristics of the atmosphere is implemented according to the following algorithm. Under external ambient light exposure conditions, a signal is received at the sensitive receiver area.

R; (R) P (R) + Cl),

where P (R) is the luminous flux due to the useful lidar signal from the range R; Photovoltaic radiation flux.

For an atmosphere with a constant indicatrix of dispersion, according to the lidar equation

P (R) A ba (R) T2 (R) R, where a is the volume scattering coefficient; b - indicatrix scattered backwards (lidar

R

attitude); T (/ R) exp (J a (R) d R) - about lO.

atmospheric opulence; A is a hardware constant.

When using an optical compensator of the square of the distance, taking into account the effect of the background radiation, the signal at the input of the photodetector will be: S (R) m P (R) R + a -F where m, a are the proportionality coefficients. The signal at the output of the photodetector is Uo (R) (R) R + a F, where K is the conversion coefficient of the photodetector: (F) ko, k (F) is the background factor, taking into account the effect of background illumination. The presence in a number of cases of a strong dependence of the conversion coefficient on the background intensity leads to significant errors in determining the optical parameters of the atmosphere from the measurement results of S (R) or P t (R). In order to attenuate the photodetector overload under the influence of an intense background, the use of biofeedings is used, moreover, in its possibilities in its first stages (for example, in a photomultiplier), to avoid overloading and saturation of the next ones. With a sufficiently large gating ratio, it is possible to significantly reduce the background effect. Therefore, the background factor of the gated receiver Kc (F) is significantly less than K (F), and kc (F) k (F} / Q, where Q is the duty ratio, can be considered. Then the signal at the output of the gated receiver U (R) koM F) Uo (R). Further, the background light is compensated for by subtracting from the useful signal (backscatter signal) the previously measured and stored background level. The signal at the output of the subtraction unit has the form U (R) k kc (F) a (R) T (R), where k-i is the proportionality coefficient, which includes k, m. Differentiating U by R, dividing by Ui, we have an equation for determining the scattering coefficient G (R) U1. As a result of this processing of received signals, it is possible to eliminate the effect on the measurement result of both the additive and multiplicative components of the measurement error due to the background. Solving the equation for a has the form a (R) 4 exp (/ G (R) d R) / o // exp (/ G (R) dR) dR oo Figure 1 shows the functional diagram of the device for determining the optical characteristics of the atmosphere ; figure 2 - timing diagrams of signals at various points of the device. The device contains a control unit 1, the input of which is connected to the clock pulse generator 2, and the outputs with emitter 3, single vibrators 4 and 5, with the outputs of single vibrators connected to the inputs of the logic element OR 6, the output of which is connected to the input of the control signal 7, output which is connected to the photodetector 8, which is optically coupled to the square-distance compensation device 9. The units 4-7 shown in Fig. 1 form a sensitivity adjustment unit and are one of the variants of its construction. The output of the photodetector 8 is connected with serially connected amplified amplifier 10, a peak detector 11 and a memory unit 12, the control input of the gated amplifier 10 connected to the output of a single vibrator 4, and the reset input of a peak detector 11 with the output of a single vibrator 5. Blocks 10-12, together with subtraction unit 13 in FIG. 1, one of the options for constructing a background compensation unit is shown. The photodetector 8 is also connected to the input of the differentiation unit 14 and one input of the unit 13, the other input of which is connected to the output of the memory unit 12. The outputs of the differentiation unit 14 and subtraction 13 are connected to the inputs of the division unit 15 whose output is connected to the input of the analog processing unit 16, the output which is connected to the recorder 17, the other input of which is connected to the output of the electronic counter 18, which is connected to the outputs of the clock pulse generator 2, the one-oscillator 5 and the photodetector of the reference channel 19, optically connected with teacher 3. In Figure 2, the following is indicated: a) a pulse at the output of a single vibrator 4 b) a pulse at the output of the radiator 3, c) a pulse at the output of a single vibrator 5, d) a signal at the output of an OR gate, e) a signal at the output of a photodetector 8, e (i) a signal at the output of the subtractor (13); h) a signal at the output of the electronic counter 18. A device for determining the optical characteristics of the atmosphere works as follows. The clock pulses from the clock pulse generator 2 are synchronized to the control unit 1, setting the operation modes of the device blocks in time. First, a one-shot 4 is started with a pulse from block 1, the gated amplifier 10 is unlocked with a short pulse from the output of which, through the logic element OR 6, the driver of the control signal 7 is opened by the photodetector 8, which is locked for this moment. At this point in time, the start of the emitter 3 is not yet happening, but at the output of the photodetector 8 and, further, the gate amplifier 10, there is a pulse in amplitude, the amplitude of which is proportional to the intensity of the background illumination. Using the peak detector 11 and the memory unit 12, the background level is fixed and fed to the first input of the subtracting unit 13. After that, the control unit 1 receives the command to start the emitter 3 and the one-oscillator 5. The single-oscillator 5 generates a strobe pulse whose width corresponds to the selected length zoned route. This pulse through the logical element OR, and the driver 7 unlocks the photodetector 8 for the required time, so that the signal of the radiator 3 scattered by the medium being converted at the output of the receiver 8 into an electrical signal that goes to the second input of the subtraction unit 13. In block 13, the subtraction background. The falling edge of the gate of unit 5 resets the peak detector 11 and the electronic counter 18.

In differentiation unit 14, the time derivative of the signal is calculated. The result obtained is normalized in division unit 15 to the difference signal from unit 13. The output signal of the output unit is fed to the analogue processing unit 16, which includes integrators 20 and 22, exponential functional converter 21 And the division unit 23, and then to the recorder 17.

A part of the energy of the radiator 3 is diverted to the photodetector of the reference channel 19, the signal from whose output starts the counter 18. The output of the counter 18 is connected to the recorder 17 to assign the measured values of the scattering coefficient to the distance scale.

Claims (3)

Claim 1. The method of determining the optical characteristics of the atmosphere, which consists in directing electromagnetic radiation to the area of the atmosphere under investigation at different background radiation, converts the scattered back radiation into an electrical signal, determines the time dependence of this signal The original optical characteristic, distinguished by that of the UTR, in order to increase the measurement accuracy when exposed to background illumination, is pre-converted with a selection in time of the background radiation into this electrical signal the background light, the electric signal of the background light are subtracted from the electric signal of the backscattered radiation, and the optical characteristics are calculated from the time derivative of the electric signal of the received backscattered radiation and the result of the subtraction. 2. A device for determining the optical characteristics of the atmosphere, containing a control unit connected to the emitter, an electronic counter, and a series-connected optical range compensator and photodetector, differing in that, in order to improve the measurement accuracy when exposed to background illumination and simplify the device, the photodetector is made gated additionally introduced a photodetector sensitivity adjustment unit, a background compensation unit, a differentiation unit, a division unit, an analog processing unit, a second photodetector, a clock generator and a recorder, the output of the gated photodetector connected to the inputs of the differentiation unit and the background compensation unit, the output of which is connected to the input of the division unit, the second input of which is connected to the output of the diff, recovery unit, the output of the division unit through the analog processing unit is connected to the recorder, the input of the connection control unit en with the output of the clock generator, and its output - with the input of the photodetector sensitivity adjustment unit, the outputs of which are connected to the control input of the gated photodetector, the compensation unit, as well as the reset input of the electronic counter, the emitter is optically connected to the second photodetector, the output of which is connected to the trigger input of the electronic counter, the clock input of which is connected to clock output and output electronic meter connected to the registrar. 3. The device according to claim 2, characterized in that the analog processing unit consists of a series-connected integrator, an exponential converter, a second integrator, and a dividing unit, with the second input of the dividing unit connected to the output of the exponential converter.