SU1733979A1 - Method of determination of natural underlaying surface - Google Patents

Abstract

Use: reflective spectrometry natural underlying surfaces. The essence of the invention: the reflection coefficient of the studied surface is determined by active sounding by two radiators in the wavelength range of 0.6-0.7 and 0.9-1.0 µm, in which the reflective properties of the surface are judged by the ratio of their contrasts with the reference level. 3 il.

Description

This invention relates to the reflective spectrometry of natural underlying surfaces and can be used in instruments designed to recognize coatings by reflection coefficient.

There is a known method for determining the state of the road surface by the magnitude of the reflected IR radiation. The wavelength of the infrared radiation of the source is chosen so that the reflection from the snow is less than from the dry road surface. The receiver generates signals that characterize the reflected light energy. The comparator compares the output signals of the receiver with the reference signals corresponding to the systematic conditions of the road surfaces. The evaluation unit conducts the determination of the compliance of the state of the studied road surface with one of the systematized states of the road surface.

The disadvantage of this method is the difficulty of determining the state of the road surface.

The closest to the proposed is a two-spectral method for monitoring the state of the road surface. The method involves the use of two light sources of the visible and IR portions of the spectrum directed to the road section. The receiving part of the device consists of three channels. Two receivers are designed to receive surface scattered visible and infrared rays, and a third to receive specularly reflected visible rays. The logic solver circuit receives the output signals of the detectors and controls the condition of the road according to their level relative to the threshold value corresponding to the formation of ice on its surface.

The disadvantage of this method is the use of three channels of reception of the reflected radiation, since the method includes, in addition to analyzing in two spectral regions, the study of the reflection indicatrix in order to detect its specular component that occurs when ice is formed on the road surface.

SP

WITH

vj WITH CO

yu yu

The aim of the invention is to simplify the determination of the reflective properties of the surface.

Fig. 1 shows a block diagram of a device for determining the reflective properties of a surface; in fig. 2 is a spectral characteristic of the reflection coefficient of various natural underlying surfaces; Fig. 3 shows the dependence of the photodetector output signal on the distance to the surface under study.

A device for implementing the method contains emitters 1 and 2 with a radiation wavelength within the spectral ranges of 0.6-0.7 and 0.9-1.0 μm, respectively, which generate light beams directed to the surface under study 3. Photodetector 4 is connected to the input of the comparison circuit 5, to the other input of which of the subkeys is a block 6 of the reference level. The output of the comparison circuit 5 is connected to the input of the surface view identification circuit 7.

The method is carried out as follows.

To implement the method, it is necessary to set up the measuring device under laboratory conditions, which includes the following operations.

Two emitters with radiation wavelength are installed in the previously indicated spectral ranges and a photodetector on the same baseline or at least a basoz plane. The reference surface is placed with a reflection coefficient, 45 at a fixed distance I perpendicular to the optical axis of the transceiver. The emitters are brought to a single power level and propagation angle. Adjust the receiving radiation system to a fixed distance I by adjusting the optical elements, which ensures the maximum photoresponse of the receiver in both spectral channels.

Ifd (AI) and Ifd (A2) voltages corresponding to the reflection coefficient from the reference surface are recorded, and the values of the reference level are calculated.

Then, using a tuned measuring device, the surface type is determined in the following order.

The measuring device is set at a distance I from the surface under study so that the optical axis of the device is abnormal to it. Consistently measuring the photo-light at two wavelengths, then (the brightness contrast KL for the given surface is counted and compared with the reference level KLO.

The KL value and the ratio with KLO determine the type of surface under study.

The method is based on statistical data on the spectral reflectance of a number of natural surfaces shown in FIG. 2

FIG. 2 denotes: snow curve with ice crust; 9 - coarse snow curve; 10 - the curve of the water surface of the lake, 11 - the curve of the soil after the melting snow; 12 - silage corn curve; 13 - curve of high green corn; 14 - yellow corn curve; 15 - Sudanese curve; 16 - black soil curve; 17 - curve of erase cereals.

An analysis of these data in the spectral range of 0.5-1.0 µm showed that, by the magnitude of the reflection coefficient and the nature of the spectral dependence, the natural surfaces are divided into two groups.

In one group, which includes most soils, pavements and vegetation, monotonous or abrupt increases in the reflection coefficient with increasing wavelength are observed. The total range of variation of the reflection coefficient for them is 5-35%. In the other group consisting of snow cover, the reflection coefficient decreases within 80-55%. The detected features of the spectral dependence of the reflection coefficient are used to select natural surfaces.

In accordance with the spectral method, surface recognition is carried out by the magnitude and sign of the average surface contrast of the surface in two spectral ranges of the AECC, DA2), which is defined as

KL (AAi, DA2) U, - (AAi) - Lni (YES :), (1)

where Lni is the average surface brightness of the i-th group;

DAH, DAA - spectral ranges.

Considering that most natural surfaces are diffuse Lamber reflectors, their brightness, when actively probed by the flux of the spectral range, is expressed as

Ui (YES) p YES-Ed / l:.(2)

where p YES is the surface reflection coefficient;

FOOD is the illumination of the surface created by the radiator with the brightness L0A and determined by the range I.

One of the conditions for spectral analysis is the equality of the power of the energy flow under study at different wavelengths. In this case, this means that

E d /, E const. (3

Taking into account the expression (3), we get

(YES) рд Е / С1рДА, (4)

where

Consequently, the brightness of a surface in a certain spectral range is determined by its reflection coefficient corresponding to a given spectral range. This means that the surface contrast in two spectral ranges is determined by the difference of their corresponding spectral reflection coefficients, t. &Amp;

Ki (YА1, Л; .2) Ci (рДЯ-РДА2)

where / edC / L / b are the surface reflection coefficients for the spectral ranges of L / and LL, respectively.

It is established that the maximum values of the contrast intensity correspond to two spectral ranges of 0.6-0.7 and 0.9-1.0 µm. This is due to the choice of working spectral ranges for the proposed method.

When choosing the spectral ranges of measurement, the spectral regions with the largest difference of the spectral reflection coefficient were considered.

The main selection criterion is to obtain the maximum value of the brightness contrast, the value of which serves as a defining characteristic of the appearance of the surface. The values of the brightness contrast at wavelengths of 0.6-0.9 µm and 0.7-1.0 µm are investigated. corresponding to the proposed spectral ranges, and in combinations of 0, 9 μm, 0.6–0.8 μm, and 0.8–1.0 μm, including one wavelength outside the selected spectral ranges.

A comparison of the quantitative values of the brightness contrast achieved in various combinations of wavelengths over the spectrum shows the advantages of the selected pair of spectral ranges, providing compared to a pair of wavelengths 0.5-0.9 μm for most, and compared with pairs 0.6-0 , 8 µm and 0,8-1,0 µm for all considered types of surface maximum brightness contrast.

Statistical data on the spectral reflection coefficient of the species

No surfaces in the infrared region of the spectrum were found at I 1 μm. The qualitative write-off in the literature of the spectral dependence of the reflection coefficient of natural surfaces in the longer wavelength region indicates the absence of regularities characteristic for the spectral region of 0.5-1.0 µm, which excludes the use of the method.

10, the method is illustrated by the graphical dependencies shown in FIG. 3 and representing the functions of the output signal of the photodetector of the device from the distance to the surface under investigation. Curves 18 and 19 were obtained by probing a reflective surface with a stream with a wavelength in the range of 0.6–0.7 μm. curves 20 and 21 are in the range of 0.9-1.0 microns. Wherein

20, the reflection from the surface with a high reflection coefficient is shown by dependences 18 and 20, curves 21 and 19 characterize the reflection from the surface with a small reflection coefficient.

The basic energy equation of the measuring system is

Fvh TS L / .A2 AvhL2 h

where Fvh - the light flux at the input of the photodetector:

gc medium transmission coefficient;

A2, Avh - the area of the visible part of the reflecting surface and the entrance pupil of the photodetector.

Suppose that the optical characteristics of the transceiver system and the external environment are constant, and the range does not change, i.e.

25

thirty

35

TC A2ABh / l COnst C2,

that

Bx s2sh

As known

IFD Zs21DA. (b, 1

where UFD is the amplitude of the output voltage of the photodiode,

S - integrated sensitivity (photodiode.

Given (4), equation (6) is written as

If SciC2PAA, it follows that the amplitude of the output voltage of the photodiode at a certain wavelength of the emitted flux can be calibrated & spectral reflectance units.

It's obvious that

.R

Substituting (7) into (5), we obtain KL (AAi, DA2) -gig (ifd (AAi) -ifd (AA2)).

The last relation shows that the reflectivity of the reflection surface in two spectral ranges, which determines its appearance, in this measuring system is equivalent to the difference in amplitudes of the photoresponse photoresponse of the photodiode, and the degree of reflectivity of the surface indicates the sign of the difference in voltage amplitudes.

The form of dependences 18–21 illustrates the principle of surface selection by reflective properties. At a fixed range, in a static measuring system at a surface with a high reflection coefficient, the amplitude of the reflected radiation in the range of 0.6-0.7 µm prevails over the amplitude of the reflected flux in the range of 0.9-1.0 µm. which, in turn, exceeds the reference level corresponding to the reference surface. For surfaces with a low reflection coefficient, reversing the relation. This means that the surface. and, depending on its reflective properties, there corresponds a certain correlation of the amplitude of the photoresponse in various spectral ranges

relative to each other and the reference level, which allows recognition of surfaces by the magnitude of this ratio and its sign.

When the surface range changes depending on the reflectivity, a certain sequence of the appearance of pulses of reflected radiation of different spectral composition corresponds. Approaching a highly reflective surface corresponds to the distance and temporal advance of a red pulse (0.6-0.7 μm) in the spectral range compared with an IR pulse (0.9-1.0 μm). The reverse pulse sequence is observed when approaching the low reflecting surfaces.

Claims (1)

The method of determining the type of natural underlying surface, including irradiation in two spectral ranges and measurement of the parameter reflected from the surface of radiation under investigation using photodetectors, followed by comparison with a reference level, characterized in that, for the sake of simplicity, the surface under study is irradiated in the ranges wavelengths of 0.6-0.7 v. 0.9-1.0 µm, and the surface contrast is measured in the indicated spectral ranges. / 7777/7 //// fae i i o /, / o thirty in 70 60 50 40 3020 ten / i.mv 40ff 50D 600 700 800 900 WOO Jw FIG. 2 / „ fia 3 tm-to-c X IN h j . 15 12 U U-1 ISO 1, cm