RU2329475C1 - Device for taking measurements of light scattering characteristics of optoelectronic instruments - Google Patents

Abstract

FIELD: optics.

SUBSTANCE: invention refers to measurement of light scattering characteristics of optoelectronic instruments (OEI) and can be used in techniques of experimental measuring of a reflection indicatrix, direction finding characteristic and effective scattering area of OEI under laboratory conditions. The device contains a source of emission (a laser), a forming system, two beam splitters, an inspected and standard retro-reflectors, a receiving collimator, two transparent mat screens, two projecting systems, two matrices of a CCD (charge coupled device), connected to a microprocessor, and a monitor. The standard retro-reflector is assembled near an entrance pupil of the inspected retro-reflector in the emission beam. The first mat transparent screen, the first projecting system and the first matrix of the CCD are arranged in series on the way of emission of the beam going out of the receiving collimator. The second mat transparent screen, the second projecting system and the second matrix of the CCD are arranged in series on the way of emission of the beam reflected from a flat parallel plate.

EFFECT: invention upgrades accuracy of OEI light scattering characteristics measurement due to reduction of systematic errors caused by dependence of a current value of standard reflectors EPR (electron paramagnetic resonance) on a distance of their location.

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Description

The invention relates to the field of measuring the light scattering characteristics of optoelectronic devices (OED) and can be used in the technique of experimental measurement of the reflection indicatrix, direction-finding characteristic and effective dispersion area of the OED in laboratory conditions.

It is known that for a comparative assessment of the retroreflective ability of various EIAs, the main retroreflective characteristics are used. These include [LASER-INFORM. Newsletter of the Laser Association No. 4 (259) February, 2003, N.V. Baryshnikov, Ph.D., V.E. Karasik, Doctor of Technical Sciences, Professor, MSTU named after N.E.Bauman Moscow, May 7, 2003]:

- effective scattering area (EPR) - σ;

- reflection indicatrix;

- direction finding characteristic.

The set of EPR in all directions relative to the optical axis of the retroreflector is its spatial reflection indicatrix.

The direction-finding characteristic of the EIA - σ (j) is the dependence of the EPR on the angle of the bearing j - the angle between the axis of the optical EIA system and the direction to the illumination source.

Moreover, it is known that, as a rule, laser beams are used during location processes and measuring the light scattering characteristics of EEDs [A.V. Pavlov. Radiation characteristics and calculation methods. M .: MO USSR, 1979, 148 pp.], And the distances between the source and the EIA, and the receiver and the OEP may not coincide [RU patent No. 2252571, 2003]

A device is known for determining the effective scattering area of an OEP (see, for example, patent RU No. 2284486, class G01J 1/10, 2006), including a backlight laser and a light splitter located along the probe radiation, between which are sequentially installed along the probe laser radiation, a collimator and a lens, with a focal length f equal to twice the distance between the light splitter and the holder of the investigated OED, between the light splitter and the photodetector along the branch of the light splitter reflected from the OED medium radiation Twa.

The disadvantage of this device is the large systematic error in measuring the EPR values due to the implementation of the method of location in a converging beam using this device.

Let us evaluate the systematic measurement error that occurs when using the device described above. According to [Yu.L. Koziratsky, V.D. Popelo, Methods for the experimental study of the reflection characteristics of optoelectronic devices, Scientific and methodological materials, 5 Central Research Institute of the Ministry of Defense of the Russian Federation, 1998, 186 p. (p. 120)]:

the distance between the entrance pupil of the OEP and the lens is L = 0.5f;

the diaphragm is installed in the plane of analysis of the radiation reflected from the EED, which is also removed from the entrance pupil of the EED by a distance also equal to L = 0.5f.

Moreover, the radius of the aperture rd depends on the modeled route Lm and is determined using the following expression:

,

,

where: ro is the radius of the entrance pupil of the receiving channel of the real sample of the laser locator.

It is known that the power ratio of the radiation received behind the diaphragm passing through the holes with the same values of their radii is proportional to the ratio of the power density in the plane of these holes. In turn, the power density in a converging beam depends on the distance of the analysis plane relative to its constriction (the focus point), and the ratio of power densities is equal to the ratio of the squares of the radii of the beams in the analysis plane, which depend on the distance of the analysis plane from the constriction.

Let us determine the removal of the waist of the converging beam reflected from the EIA.

Consider the course of the rays passing in the forward direction during the location of optoelectronic devices (OED) in a converging beam, which is shown in FIG. 2.

Figure 2 shows the following notation: L is the radius of curvature of the wave front in the plane of the entrance pupil of the OED (range of location of the OED in a converging beam); f is the value of the paraxial focus of the OED lens; x1 is the distance between the rear main plane of the OED lens and the point of intersection of the convergent beam focused by it with the axis; z1 is the distance between the paraxial focus of the lens and the point of intersection of the convergent beam focused by it with the optical axis; z2 is the distance between the paraxial focus of the lens and the point of intersection of the directions of the rays of the beam incident on the entrance pupil with the optical axis.

The distance between the rear main plane of the OED lens and the point of intersection of the convergent beam x1 focused by it can be determined using the Gauss equation [Applied Optics / A. Dubovik et al .; Textbook for high schools, M., Nedra, 1982, 621 p. (pg. 40-41)]:

.

.

From figure 2 it follows that the distance between the paraxial focus of the lens and the point of intersection of the directions of the rays incident on the entrance pupil of the beam with the axis z2 is equal to:

.

.

Substituting (3) in (2) after simple transformations and abbreviations, we obtain:

.

.

From (4) it can be seen that the value of x1 is less than the value of the paraxial focus of the OED lens.

Figure 3 shows the progress of the rays passing in the forward and reverse directions during the location of optoelectronic devices (OED) in a converging beam.

In Fig. 3, the following notation is used: OD — reflective flat surface located in the paraxial focal plane of the lens perpendicular to its optical axis; x2 is the distance between the front main plane of the lens and the point of intersection of the rays of the reflected converging beam of radiation; z3 is the distance between the reflecting surface and the intersection point of the continuation of the reflected OP rays.

From figure 2 and 3 and geometric considerations follows:

;

;

since the angles of incidence and reflection of the rays relative to the OD are equal, then the distances between the paraxial focus of the lens and the point of intersection of the convergent beam focused by it with the optical axis z1 and between the reflecting surface and the point of intersection of the continuation of the reflected OP rays z3 are equal;

the beam of rays reflected from the optical beam can be replaced by an equivalent homocentric beam, the radiation point of which is located on the optical axis and is removed from the optical beam by a distance z3.

In view of the above, the distance between the front main plane of the OED lens and the point of intersection of the convergent beam x2, which is focused on it and reflected from the OP, as an equivalent homocentric beam can be determined using the Gauss equation [Applied Optics / A. Dubovik et al .; Textbook for high schools, M., Nedra, 1982, 621 p. (pg. 40-41)]:

.

.

Subsequently substituting (6) in (5) and (4) and making successive transformations and reductions, we obtain:

.

.

From the above reasoning and expression (7), it follows that the systematic measurement error that occurs when using the device described above is caused by the installation of the diaphragm in the claimed device (offset of the analysis plane) relative to the waist plane of the converging beam reflected from the OEP by a distance equal to 2f.

From figure 2 and expression (7) it follows that the value of the radius of the beam in a plane remote from the front main plane of the lens by a distance L can be determined using the following expression:

,

,

where r _OEP is the radius of the entrance pupil of the located OEP.

Assuming that the beam radius in the plane remote from the OED by a distance equal to 2f + L is equal to the radius of the diaphragm, taking into account (7) and (8), we can obtain the following expression, which allows us to obtain the ratio of the powers of the signals K recorded after the diaphragm located from the lens at a distance of 2f + L and L, respectively:

.

.

Let Lm = 3 km, r _OEP = ro = 3 cm, L = 1 m, and f = 10 cm.

The calculations performed using expression (9) showed that in this case K = 9 · 10 ⁶ . That is, the measurement of the EPR in a converging beam in the considered case leads to an underestimation of the true value of the EPR by almost seven orders of magnitude.

The foregoing shows that the use of the device according to patent RU 2284486 C1 no to class G01J 1/10 leads to systematic errors in measuring the EPR values of the EIA by several orders of magnitude.

A device is known for determining the effective scattering area of an OEP (see, for example, Meisels E.N., Torganov V.A., Measuring the scattering characteristics of radar targets. - M .: Soviet Radio, 1972, p. 41), including a backlight laser, holder of the investigated EIA, installed along the probe laser radiation, a photodetector installed along the laser radiation reflected from the EIA, and a detector of the output signal of the photodetector, the input of which is connected to the output of the photodetector.

The disadvantages of this device are the presence of a systematic measurement error associated with the short length of the measuring path (limited length of the laboratory room), as well as the inability to measure the reflection indications of the EIA with this device.

It is well known that the most common and simplest way of measuring the EPR values of an OES is a direct measurement method based on recording the voltage at the output of the meter’s receiving channel U ₀ proportional to the level of the radiation signal reflected from the OES in the plane of its reception. Measurements are carried out using pre-calibrated using ES equipment. The equation of direct measurements has the following form:

σ = g _e U ₀ ,

where g _e - the price of the division of the scale of the measuring device.

The most common calibration method is to calibrate the measuring equipment with a reference reflector placed at the same range as the OED under study. Given the linearity of the operating characteristics of the measuring path of the equipment, the value of g _e is defined as:

,

,

where σ _E - ESR ES (ES), U _e - the magnitude of the signal proportional to the level of radiation reflected from the ES in the plane of its reception.

As a rule, during calibration, spherical convex mirrors with known values of the radius of curvature R _s and reflection coefficient p _{s of the} mirror surface are used as ES. In this case, the values of R _s vary within units - tens of meters, and the values of p _{s are} from 0.8 to 0.95. In [A.V. Pavlov. Radiation characteristics and calculation methods. M .: MO USSR, 1979, 148 pp.] It is shown that the EPR value of such an ES can be calculated using the following expression:

It follows from expression (10) that the EPR of a spherical convex mirror depends only on the parameters characterizing this mirror.

However, the results of experimental studies have shown that expression (10) for calculating the EPR of a spherical convex mirror as an ES during calibration of measuring equipment on paths of limited length (especially in laboratory conditions) is not fair, which leads to an error in the calibration of the EPR meter and, therefore, to systematic EPR measurement errors of real EIA samples.

This fact was discovered by comparing the results of ES measurements with the known EPR values and is explained by the fact that the EPR values of the reference reflectors depend on the conditions of their location, which when deriving expression (10) in [A.V. Pavlov. Radiation characteristics and calculation methods. M.: USSR Ministry of Defense, 1979, 148 pp.] Were not taken into account. Under the conditions of location in this case we mean the parameters characterizing:

the distance between the ES and the probe radiation source;

the distance between the ES and the entrance pupil of the receiving channel of the measuring equipment.

It is known that the diverging beam corresponds to the condition of exposure to an ES laser without a collimator at its output.

In the future, we will assume that in this case the radiation source is point and diverging.

The derivation of expression (10) for a point source is given, for example, in [A.V. Pavlov. Radiation characteristics and calculation methods. M.: USSR Ministry of Defense, 1979, 148 pp.], Where it was shown that if the radiation strength of the probe radiation source (ZI) (target irradiator) I is _known , then the magnitude of the radiant flux that will reach the entrance pupil of the meter’s receiving channel after reflection from an object of a spherical shape with a mirror surface will be determined by the following expression:

.

.

where: S _p - the area of the reflecting circular area on the surface of the ES, from which the reflected radiation will fall into the entrance pupil of the receiving channel of the meter; L is the location range; τ _with - transmittance of probe radiation along a path of length L.

.

.

where: r is the radius of the site on the surface of the ES, from which the reflected radiation will fall into the entrance pupil of the receiving device;

D is the diameter of the entrance pupil of the lens of the receiving channel of the meter.

In the derivation of expressions (10), (11) and (12), the following was assumed:

- the source of ZI is a point;

- the center of the point source of ZI coincides with the center of the entrance pupil of the lens of the receiving channel of the locator;

- the distances from the center of the ES to the source and from the center of the ES to the center of the entrance pupil of the receiving channel lens are equal;

- the optical axis of the ZI beam and the optical path of the receiving channel coincide and pass through the center of the ES;

- the diameter of the beam reflected from the ES radiation is less than the diameter of the entrance pupil of the receiving channel (PC);

- the transverse dimensions of the spot formed by the radiation reflected from the ES on the photosensitive surface of the receiver are less than the transverse dimensions of this surface;

- the radius of curvature of the ES is significantly less than the range of the location.

However, as preliminary estimates showed, the last condition on the routes of a location of limited length (especially in laboratory conditions) is practically not fulfilled.

To assess the effect of the relationship between the radius of curvature of the ES and the range of the location on the ESR value of ES, we consider the processes of radiation of the ES and reflection from it of the radiation of a point source of ZI (Figure 4).

Figure 4 indicates: α1 is the angle between the optical axis of the receiving channel (PC) and the direction of propagation of the beam from the source of the radiation source, which, after reflection from the ES, hits the edge of the entrance pupil of the PC lens (hereinafter the extreme beam); α2 is the angle between the direction of propagation of the extreme beam after reflection from the ES and the optical axis of the PC; β1 is the angle between the normal to the ES at the reflection point of the extreme beam and the optical axis of the PC; β2 is the angle between the normal to the ES at the reflection point of the extreme ray and the ray incident at this point; L1 is the distance between the source and the ES point located on the optical axis of the PC; L2 is the distance between the ES point located on the optical axis of the PC and the plane of the entrance pupil of the PC lens.

Let, as in [A.V. Pavlov. Radiation characteristics and calculation methods. M .: MO USSR, 1979, 148 pp.] The point source of the ZI is located on the optical axis of the PC, and the optical axis of the beam coincides with the optical axis of the PC. In this case, as follows from figure 3, the angle α2 is equal to:

.

.

Expression (13) differs from the expression for angle α2 obtained in [A.V. Pavlov. Radiation characteristics and calculation methods. M .: Ministry of Defense of the USSR, 1979, 148 pp.], By the presence in the numerator of a deductible equal to 2r. At the same time, from figure 3 it follows that:

α2 = β1 + β2 and β2 = β1 + α1

.where from:

.

Since L1 is much larger than r, then α1 = r / L1, whence:

.

.

Substituting (15) into (13) and assuming that since the radius of curvature of a spherical convex mirror is much larger than the radius of the area on the surface of the ES from which the reflected radiation will fall into the entrance pupil of the receiving device r, then β1 = r / R _З. In this case, we obtain that for L1 ≠ L2, the radius r will be equal to:

.

.

преобразуется к следующему виду:At

converted to the following form:

.

.

The areas of the reflecting circular area on the surface of the ES, from which the reflected radiation will fall into the entrance pupil of the receiving device, for different conditions of location of the ES, the point source will be respectively equal to:

.

.

It is known that the signal level taken from the photodetector of the PC locator is directly proportional to the irradiation of its entrance pupil, which directly depends on the ESR of the ES. Since only the part of the ZI that is reflected from the circular area on the surface of the ES with radius r falls into the entrance pupil of the PC lens, the irradiation ratio in the plane of this lens calculated using expressions (18) H (L1 ≠ L2) or (19) H ( L1 = L2 = L), the irradiance calculated using the known expression (12) H ₃ will be respectively equal to:

,

,

.

.

Table 1 shows the PSV ES ratios calculated using expressions (20) and (21) for various ranging distances and values of the radius of curvature of the reflecting surface of the ES.

Table 1 PSV ES relationships for various location ranges and values of the radius of curvature of the ES reflecting surface when it is irradiated with a point source. L1, m 10 (lab. Conv.) twenty fifty one hundred 200 500 750 1000 1500 K1, R ₃ = 5 m L2 = 0.5L1 0.327 0.529 0.756 0.865 0.929 0.971 0.98 0.985 0.99 K1, R ₃ = 10 m L2 = 0.5L1 0.16 0.327 0.592 0.756 0.865 0.943 0.961 0.971 0.98 K1, R ₃ = 15 m L2 = 0.5L1 0,095 0.221 0.476 0.666 0.808 0.916 0.943 0.956 0.971 K2, R ₃ = 5 m 0.44 0.64 0.826 0.907 0.952 0.98 0.987 0.99 0,993 K2, R ₃ = 10 m 0.25 0.444 0.694 0.826 0.907 0.961 0.974 0.98 0.987 K2, R ₃ = 15 m 0.16 0.327 0.592 0.756 0.865 0.943 0.961 0.971 0.98

From table 1 and expressions (20) and (21) it follows that:

the current PSV value of ES at location ranges comparable with the radius of curvature of the reflecting surface will be several times smaller than the value of PSV calculated using the well-known expression (10), which will lead to a similar overestimation of the ESR values of the OES when measuring equipment calibrated using such ES;

only at a range L location that exceeds the radius of curvature of the ES R _{3 by} more than two orders of magnitude, the ratios of the measured PSV values K1 and K2 become approximately equal to unity.

Since in the known device for determining the effective scattering area of the OED [Mayzels EN, Torganov VA Measuring the dispersion characteristics of radar targets. - M .: Sovetskoye Radio, 1972, p.41] there are no elements for moving the photodetector relative to the optical axis of the probe radiation beam reflected from the OED and registering the values of the angles between the direction to the receiver relative to the center of the entrance pupil of the OED and the optical axis of the OEP, then the reflection indicatrix of the OES with this device not allowed.

Thus, the use of the known device for determining the effective scattering area of the EIA [Mayzels EN, Torganov VA Measuring the dispersion characteristics of radar targets. - M .: Sovetskoye Radio, 1972, p.41] does not take into account the dependence of the EPR values of the reference spherical reflectors on the range, which leads to the underestimation of the measured EPR values of the EIA up to six times, and also does not provide the possibility of measuring the reflection indicatrix of the EIA with this device.

The closest in technical essence and the achieved result is a device for measuring the retroreflectivity of optoelectronic devices [Russia, Patent No. 2202814 in class G02В 23/12, 2003], which includes a radiation source and a forming optical system sequentially installed along its radiation path installed with the possibility of replacing optoelectronic or optical devices and a reference retroreflector, a first beam splitter, a receiving collimator, a second beam splitter, in which a projection system and a CCD matrix, the installation plane of which is optically coupled to the focal plane of the receiving collimator, and in the other shoulder is a condenser lens and a radiation receiver, the output of which is coupled to the input of a digital voltmeter, the outputs of the matrix and digital voltmeter are connected to the input of the microprocessor, the output of which is connected to monitor, while the microprocessor is configured to control the measuring solid averaging angle Ω _ISM in accordance with the value of the measured retroreflectivity and Woodland _et angle Ω averaging corresponding indicatrix of reflection from the reference svetovozvrvschatelya and R index value calculating retroreflection _{communication} inspected reflector averaged in a solid angle Ω _edited by the expression

where Ub ^{max is the} voltage of the signal taken from the radiation receiver when registering radiation reflected from the inspected retroreflector, and calculated by the microprocessor in the body averaging Ω _ISM ;

U _et ^max - voltage of the signal taken from the radiation receiver when registering radiation reflected from the ES, and calculated by the microprocessor in the solid averaging angle Ω _et ;

Ф _St. (Ω _ISM ) - the stream incident on the CCD matrix when registering radiation reflected from the inspected reflector, and calculated by the microprocessor in the solid averaging angle Ω _ISM ;

Ф _SV (Ω _et ) is the flux incident on the CCD matrix during registration of radiation reflected from the inspected retroreflector and calculated by the microprocessor in the solid averaging angle Ω _et ;

R _et - indicator retroreflective ES.

It is known that the retroreflectivity index (PSV) of optoelectronic devices R (p) is related to their EPR σ (p) by the following dependence [V.R. Muratov, Yu.A. Filimonov, A.F. Shirankov On terminology related to retroreflective reflection, Optical-mechanical industry, 1980, No. 3]:

.

.

From the expression (22) it follows that the device for measuring the retroreflectivity of optoelectronic devices according to the patent 2202814 in the class G02В 23/12 simultaneously allows measuring the EPR of the EIA.

It should be noted that the CCD matrix included in the prototype device, as follows from the claims, is intended for recording the reflection indicatrix of the EIA. In this case, the reflection indicatrix is registered only for the conditions of location in the far zone, corresponding to the infinite distance of the analysis plane from the located OED.

The disadvantage of the prototype device is the presence of systematic errors in the measurement of the EPR and the reflection indicators of the EIA, due to:

- the inability to take into account the dependence of the current value of the reference EPR reflectors on the range of their location;

- the inability to reproduce the spatial characteristics of the probe radiation in the plane of the entrance pupil of the located OEP corresponding to a given location range by the forming optical system of the device;

- the inability to control the spatial characteristics of the probe radiation in the plane of the entrance pupil of the located OEP corresponding to a given range of location;

- measuring the EPR values at an indefinite distance from the OEP to the receiver, and the reflection indicatrix only in the far zone, corresponding to the infinite distance of the analysis plane from the located OEP;

- the inability to determine the sign of curvature of the wave front of the reflection indicatrix of the EIA;

- uncontrolled operation of automatic gain control (AGC) systems in the electronic path of the CCD.

These causes of systematic errors due to the principles of construction, methods of technical implementation and installation of the main elements in the optical path of the prototype device.

In order to confirm the presence of the above reasons for the occurrence of systematic errors, we first carry out a detailed analysis of the physical processes that occur when the OEDs are irradiated with laser beams and the OEDs are rereflected in the opposite direction.

The physics of the process of irradiating an EIA with a laser beam is as follows.

It is known that when an OED is irradiated with beams with different values of the sign and radius of curvature, the constriction of the beam focused by the lens will shift relative to the paraxial focus of the lens. Wherein:

the absolute value of the displacement of the waist relative to the paraxial focus of the lens will be inversely proportional to the radius of curvature of the wave front;

when the OED is irradiated with a diverging beam, the constriction relative to the paraxial focus will shift toward the distance from the lens;

when the OED is irradiated with a converging beam, the constriction relative to the paraxial focus will shift toward approaching the lens;

as the shift of the point of intersection of the rays passing through the lens with the optical with its axis relative to the reflective surface of the optical element located in the focal plane of the lens increases, the EPR value of the EED will decrease.

It follows from the above that, in addition to the aberration characteristics of the OED lens, the shape of the OED reflection indicatrix and its maximum value will depend on the sign and radius of curvature of the radiation beam in the plane of the entrance pupil of the OED.

At the same time, it is known that in the course of the EIA location process, as a rule, diverging laser beams are used [A.V. Pavlov. Radiation characteristics and calculation methods. Moscow: USSR Ministry of Defense, 1979, 148 pp.].

In this case, it is necessary to take into account the position according to which a real laser beam is a wave different from both a spherical and a plane wave. So, the main difference between a laser beam and spherical and planar beams is that at a given energy level it is bounded by a single-band rotation hyperboloid, the axis of which coincides with the cavity axis [I.I. Pakhomov, A.B. Tsibulya. Calculation of optical systems of laser devices. M .: Radio and communications, 1986, 151 S.].

In the general case, the envelope of a laser beam in a plane passing through its center can be described using the following expression [I. I. Pakhomov, A. B. Tsibulya. Calculation of optical systems of laser devices. M .: Radio and communication, 1986, 151 pp.]:

Where:

a is the radius of the beam in the constriction (minimum cross section) of the beam;

b is the confocal resonator parameter equal to the value of X, at which the value of the asymptote of the hyperbola is equal to a;

X is the distance from the plane of analysis to the constriction.

The physical meaning of the parameters a and b is clearly visible in Figure 5.

In [I.I. Pakhomov, A.B. Tsibulya. Calculation of optical systems of laser devices. M .: Radio and communication, 1986, 151 pp.] It is also shown that the conditions for the conversion of a laser beam by a lens differ from the conditions for the conversion of a spherical beam, because:

- the planes of constrictions of the initial and lens-formed beams are not mutually conjugate, that is, the constellation formed is not the image of the original;

- the parameters of the hyperbola a and b describing the beam transformed by the lens, as well as the position of its constriction, depend on the parameters of the initial hyperbola, the distance from the constriction of the initial beam to the lens, and the focal length of the lens.

In addition to the above, the following fact should be noted. Since the envelope of the hyperbola beam is formed by a multitude of individual rays propagating in it, one can find the parameters of the individual extreme ray that are tangent to the hyperbole at the point of contact with the lens surface. Due to the fact that the thickness of the lens is small compared to the radii of curvature of its surfaces, the lens can be considered thin. Then the equation of the tangent (of the desired ray) will take the following form [I.I. Pakhomov, A.B. Tsibulya. Calculation of optical systems of laser devices. M .: Radio and communication, 1986, 151 pp.]:

where: a and b are the parameters of the hyperbola;

X is the current coordinate value on the beam axis;

X _P - removal of the lens from the constriction.

From expression (24) it is easy to obtain a formula for estimating the coordinate value of the point of intersection of the tangent with the X axis relative to the waist plane:

The meaning of the ΔX value is clearly visible in Fig.6.

It follows from expression (25) that the intersection point of the extreme tangents in the beam with the X axis depends only on the parameter b of the hyperbola and the distance from the lens to the constriction. This, in turn, indicates that a spherical front, whose radius R is determined by the following expression, falls on the lens remote at a distance X _P from the constriction

Taking into account (26) and simple geometric considerations, we can obtain an expression that allows an accurate estimate of the angular divergence of the laser beam incident on the lens (OED lens), which is distant X _P from the waist of the probe beam

or

At the same time in [I.I. Pakhomov, A.B. Tsibulya. Calculation of optical systems of laser devices. M .: Radio and communications, 1986, 151 pp.] It was shown that the basic requirement for the spatial similarity of the exposure conditions of the entrance pupil of the located OEP on real and simulated paths is the equality of the angles of arrival of the rays incident on the pupil in both of these cases.

Since expressions (27a) and (27b) are valid for angles of arrival in both cases, the similarity condition can be ensured only if the following equality holds:

where: R _OEP - radius of the entrance pupil of the OEP;

X _{P r} and X _{P m} - the distance from the entrance pupil of the OEP to the constriction in real and simulated conditions, respectively;

ΔX _p and ΔX _m - the distance from the point of intersection of the tangents to the waist plane in real and simulated conditions.

For the subsequent analysis, taking into account (25), we reduce expression (28) to the following form

An analysis of expressions (28) and (29) shows the following:

- to assess and comply with the similarity conditions for irradiation of the entrance pupil under simulated conditions under real conditions, initial information on the parameters of hyperbolas enveloping the real and simulated beams, as well as the distance between the constrictions of these beams and the entrance pupils of the real and simulated OEP, is necessary;

- in the general case, similarity conditions can be provided with the help of only one collimator that implements the given parameters of the hyperbola and the distance to the constriction.

It should be noted that in almost all of the above expressions, the parameters of the hyperbola enveloping the initial laser beam are included as initial data. However, as a rule, they are absent in the passport data for the laser.

At the same time, they can be quite simply found experimentally. Since laser beams have a relatively small divergence (of the order of a dozen angular minutes), the radius of the spot at the laser output, which, as a rule, is given in the laser passport, can be taken as the waist size value. This approximation becomes completely valid for gas lasers, in which the constriction coincides with the output mirror. For other types of lasers, it is generally accepted that the constriction is in the middle of the cavity. The parameter b of the _{SRI of the} beam can be calculated using the expression obtained from (23):

Where:

a _u is the radius of the ISI beam waist;

y (L) is the radius of the spot on the screen, remote at a distance L from the laser.

Practice shows that for calculating the b of the _{IPR of} real lasers, the length of the measuring path can not exceed 10 ÷ 15 m. It should be noted that in almost all of the above expressions, the parameters of the hyperbola enveloping the original laser beam are included as initial data. However, as a rule, they are absent in the passport data for the laser.

At the same time, they can be quite simply found experimentally. Since laser beams have a relatively small divergence (of the order of a dozen angular minutes), the radius of the spot at the laser output, which, as a rule, is given in the laser passport, can be taken as the waist size value. This approximation becomes completely valid for gas lasers, in which the constriction coincides with the output mirror. For other types of lasers, it is generally accepted that the constriction is in the middle of the cavity. The parameter b of the _{SRI of the} beam can be calculated using the expression obtained from (23):

Where:

a _u is the radius of the ISI beam waist;

y (L) is the radius of the spot on the screen, remote at a distance L from the laser.

Practice shows that for calculating b _{IPR of} real lasers, the length of the measuring path can not exceed 10 ÷ 15 m.

At the same time, it follows from the laws of geometric optics that when the OED is removed from the laser radiation source, the angular divergence of the beam passing through the entrance pupil of the OED will decrease, which in turn will lead to a decrease in the distance between the paraxial focus of the OED lens and the waist plane with the focus beam.

As an example, a numerical assessment was made of the distance dependence of the angles of arrival of tangents to the envelope of a beam of a hyperbole in the plane of the entrance pupil of the EED. In the calculations, the following initial data were used:

- the radius of the waist of the laser beam a is 2 mm;

- the beam hyperbola parameter b, which determines its angular divergence, is 2000 mm;

- the distance between the input collimator lens and the constriction is 100 mm;

- the focal lengths of the input and output collimator lenses are respectively 20 and 200 mm, the collimator magnification factor is 10;

- the divergence of the beam at the output of the collimator is equal to one angular minute.

Using the expressions given in [II Pakhomov, A.B. Tsibulya. Calculation of optical systems of laser devices. M .: Radio and communication, 1986, 151 pp.] For the above source data, the beam parameters were calculated at the collimator output and in the plane of the entrance pupil of the OED for various distances between the pupil and the locator. The calculations showed that the beam emerging from the collimator of the locator is characterized by the following parameters:

- the diameter of the beam at the output of the collimator is 19.95 mm;

- an angular divergence of one minute is achieved at a distance of 0.55 mm from the input lens of the collimator to the output;

- parameter b (see Fig.6) is equal to 5.276 · 10 ³ mm;

- the distance between the constriction and the output lens is 7.234 · 10 ⁴ mm (beam diverging).

Figure 7 shows a graphical dependence of these angles on the location range. In Fig. 7, the X-axis shows the values of the angular divergence of the laser beam passing through the entrance pupil of the OED, expressed in radians, and the X-axis represents the distance between the OEP and the waist of the laser beam, expressed in centimeters. From the dependence shown in Fig. 7, it can be seen that the angles of arrival of the beams tangent to the hyperbolas in the entrance pupil of the EED with a diameter of 50 mm at ranges of 3 km and 30 m are respectively 8.132 · 10 ^-6 and 2.443 · 10 ^-4 rad. These values correspond to 1.8 arc seconds and 8.4 arc minutes. That is, when the location range changes from 30 m to 3 km, the angle of arrival changes by almost three hundred times.

This fact shows that in the course of measuring the characteristics of the reflection of the EIA (EPR and indicatrix) in the laboratory, it is necessary to reproduce the irradiation conditions of the entrance pupil of the OEP corresponding to the real (given) range of the location.

The physics of the process of reflection of an EIA of a laser beam is as follows.

In the description of the invention according to patent No. 2202814 according to class G02B 23/12, it is stated that "By its definition, PSV, and therefore EPR, is the internal characteristics of an EIA, independent of the conditions of illumination and reception of reflected radiation." However, in the same description, the following is stated: “The illumination radiation passes through the lens in the forward direction, is focused by it, for example, in the plane of the radiation receiver, is reflected from it, and then passes through the lens, but in the reverse direction. As a result, after passing the exit pupil of the OEP, a retro-reflected radiation indicatrix forms, the angular size of which does not exceed several mrad., And the shape is determined by the design of the optical system and its aberration characteristics. "

At the same time, it is known that the optical path of the OED during the passage of laser beams in the forward and reverse directions can be replaced by an equivalent collimator consisting of two lenses (lenses). In this case, the foci of both lenses of the equivalent collimator are equal to the focal length of the OED lens, and the distance between them is equal to twice the focal length f _of the OED lenses plus (minus) twice the amount of focus shift relative to the reflecting surface located near the focal plane.

From this position it follows that the main design parameter of the optical system, which determines the PSV value and the shape of the reflection indicatrix, is the position of the reflecting surface of the optical element located near the focal plane of the OED lens relative to the paraxial focus of this lens. Wherein:

the absolute value of the angular size of the reflection indicatrix is directly proportional to the displacement of the reflecting surface relative to the paraxial focus of the lens, and the EPR value is inversely proportional to the square of this displacement;

if the intersection point of the rays passing through the lens with its optical axis and the reflecting surface of the optical element located in the focal plane of the lens coincides, the EPR value of the EED will be maximum;

when the reflective surface is displaced relative to the paraxial focus of the lens closer to the lens, the reflection indicatrix will diverge;

when the reflective surface is removed relative to the paraxial focus of the lens from the lens, the reflection indicatrix will converge.

In the latter case, the reflection indicatrix of such an OEP will first be a converging beam, and then, with increasing range, a diverging beam. In this case, the sign of curvature of the wavefront of the beam of such an indicatrix and its cross section, and hence its maximum value, will depend on the distance between the entrance pupil of the OED and the plane of analysis (reception) of the radiation reflected from the OED, i.e. from the conditions of admission.

From the above it follows that in addition to the aberration characteristics of the OED lens, the shape of the OED reflection indicatrix and its maximum value will also depend on the direction and magnitude of the displacement of the reflecting surface relative to the paraxial focus of the lens.

It is also known that:

the direction and magnitude of the displacement of the reflecting surface relative to the paraxial focus of the lens can change during the operation of the EIA for its intended purpose;

modern television systems and night vision devices have optical focusing devices as part of the optical path, depending on the current value of the observation range;

when focusing on the image sharpness of an object located at a final distance value, the reflecting surface is shifted away from the entrance pupil of the OED lens by the magnitude of AX toward the distance from the lens [Applied Optics / Dubovik A.S. et al .; Textbook for universities. M .: Nedra, 1982, 621 p. (pg. 40-41)].

The values of ΔX calculated as an example, depending on the focusing range L _f for three types of lenses are shown in Fig. 8, where different lines correspond to lenses with different focal lengths f:

From Fig. 8 it follows that with increasing distance between the target and the OED, the ΔX value decreases. It should be borne in mind that, as shown in Fig. 8, with increasing distance, the angular divergence of the beam in the plane of the entrance pupil of the OED will also decrease. This in turn will result in:

shifting the waist of the focused beam closer to the paraxial focus of the lens;

changing the distance between the constriction and the reflective surface;

a change in the angular divergence of the reflection index of the EIA and its maximum value.

As an example, Fig. 9 shows the dependence of the EPR of an ideal OED (an OED lens with a focus of 150 mm does not have aberrations) on the distance between the waist of the laser beam and the plane of the entrance pupil of the OED when focusing the OED to a distance of 2.1 km.

The graphical dependence shown in Fig. 9 shows that the EPR of the EED, depending on the location range, can vary by orders of magnitude relative to its maximum value. Moreover, from the foregoing, it follows that if the EIA is focused on a different range, then the maximum will shift in accordance with this range.

Thus, in the general case, in addition to the composition and characteristics of the elements of its optical path, the characteristics of reflected OEP radiation (its EPR and indicatrix) in the plane of their analysis are significantly affected by:

type and parameters of the sounding radiation source (ISI);

spatial conditions of the optical location (the distance between the exit pupil of the IIS and the entrance pupil of the OEP, the distance between the entrance pupils of the OEP and the receiving channel);

spatial conditions of the EIA functioning process for its direct functional purpose (its focusing range).

From the above, the following main conclusions follow:

in the course of measuring the characteristics of the EIA reflection (EPR and indicatrix) in the laboratory, it is necessary to reproduce the irradiation conditions of the entrance pupil of the OEP corresponding to the real (specified) range of the location;

in the course of measuring the characteristics of the reflection of the EIA (EPR and indicatrix) in the laboratory, it is necessary to reproduce the range of reception of radiation reflected from the EIA, corresponding to the real (given) range of the location;

during calibration of the measuring path of the device, it is necessary to take into account the dependence of the current EPR value of the reference reflectors on the distance of their location.

Given the above features of the location of the EIA in real conditions, we determine the causes of systematic errors due to the principles of construction, methods of technical implementation and installation of the main elements in the optical path of the prototype device, as well as ways to eliminate them in the inventive device.

1.1. The inability to take into account the dependence of the current EPR value of the reference reflectors on the distance of their location in the prototype device.

The dependence of the current value of the EPR reference reflectors on the range of their location was shown above when analyzing a known device for determining the effective area of OEP scattering (see, for example, Mayzels EN, Torganov VA. Measurement of the scattering characteristics of radar targets. - M .: Soviet Radio, 1972, p. 41). However, according to the formula for the invention for a prototype device, this dependence is not taken into account in it.

1.2 The inability to reproduce the spatial characteristics of the probe radiation in the plane of the entrance pupil of the located OEP corresponding to a given location range by the forming optical system in the prototype device.

The absence in the prototype device of the means for adjusting the angular divergence of the laser beam in the plane of the entrance pupil of the EED leads to an uncertainty in the distance at which the EPR and the reflection indicatrix of the EIA are measured, and therefore to the systematic errors of their measurement.

1.3. The inability to control the spatial characteristics of the probe radiation in the plane of the entrance pupil of the located OEP corresponding to a given location range in the prototype device.

Taking into account the main provisions of the claims, the absence in the prototype device of the means for controlling the angular divergence of the laser beam in the plane of the entrance pupil of the OED makes it impossible to determine the distance between the locator and the OED, at which the EPR and the reflection indicatrix of the OED are measured, and hence the systematic errors of their measurement .

1.4. The measurement of the EPR values of the OEP in the prototype device at an indefinite distance from the OEP to the receiver, and the reflection indicatrix only in the far zone, corresponding to the infinite distance of the analysis plane from the located OEP.

It is known that the receiving collimator of the prototype device located between the first and second beam splitter scales the spatial (and therefore energy characteristics) of the radiation reflected from the OEP [I.I. Pakhomov, A.B. Tsibulya. Calculation of optical systems of laser devices: M .: Radio and communication, 1986, 151 S.].

At the same time, it is known that the optical path of the OED during the passage of laser beams in the forward and reverse directions can be replaced by an equivalent collimator consisting of two lenses (lenses).

This fact allows us to draw the following conclusions:

a laser beam is formed at the exit of the EIA, the envelope of which is also a hyperbole;

at the output of the prem collimator, a beam will also be formed, the envelope of which will be a hyperboloid of revolution.

We will determine the scale factors that determine the length of the path simulated by the receiving collimator, taking into account the following facts:

the envelope of the beam transmitted through the receiving collimator is a hyperboloid;

the receiving collimator scales the parameters of the beam emerging from it both vertically and horizontally;

the vertical scale (Y axis) is equal to the ratio of the beam waist at the output of the collimator to the size of the beam waist at the exit of the OED;

the horizontal scale (X axis) is equal to the ratio of the removal of the beam waist at the exit of the collimator from its eyepiece to the value of the removal of the beam waist from the entrance pupil of the OEP.

Let a beam enter the collimator input, the hyperbola envelope of which has the parameters a _u and b _u , the beam constriction is removed from the collimator input lens by a distance X _u . A beam is formed at the output of the collimator, the envelope of which is also a hyperbola with parameters a _m and b _m , while the constriction of the beam formed by the receiving collimator is removed from the collimator output lens by a distance of X _m .

In relation to this case, the parameters a _m and X _m can be calculated using the expressions given in [II Pakhomov, A.B. Tsibulya. Calculation of optical systems of laser devices. M .: Radio and communications, 1986, 151 S.].

So the parameter a ₁ at the output of the first along the rays of the lens (collimator lens) is equal to:

Since the removal of the waist of the formed OED beam from the entrance pupil of the receiving lens is much larger than the focal length of this lens with sufficient accuracy for subsequent estimates, we can assume that the waist of the beam transformed by the lens of the receiving collimator coincides with the focus of its lens. In this case, the size of the beam waist at the output of the receiving collimator will be equal to:

Since, as a rule, X _and and in _{and are} approximately equal, expression (33) can be represented with a sufficient degree of accuracy in the following form:

. Этот коэффициент означает, что для соблюдения пространственного, а главное, энергетического подобия условий регистрации отраженного от ОЭП излучения диаметр входного зрачка объектива (согласно формуле изобретения по патенту №2202814 конденсорной линзы) канала измерения значения ЭПР на выходе приемного коллиматора должен быть в К_Y раз меньше, чем диаметр входного зрачка объектива канала измерения значения ЭПР в натурных условиях.It follows from expression (32) that the receiving collimator reduces the scale of the beam emerging from it along the Y axis with respect to the initial beam with a coefficient equal to

. This coefficient means that in order to comply with the spatial and, most importantly, the energy similarity of the registration conditions for radiation reflected from the EED, the diameter of the entrance pupil of the lens (according to the claims of patent No. 2202814 of the condenser lens) of the channel for measuring the EPR value at the output of the receiving collimator should be K _Y times smaller than the diameter of the entrance pupil of the lens of the channel measuring the value of the EPR value in natural conditions.

The value of removing the beam waist at the output of the collimator from its eyepiece X _m , taking into account similar considerations, will be determined by the following expression:

. Этот коэффициент означает, что для соблюдения пространственного и энергетического подобия условий регистрации отраженного от ОЭП излучения, удаление входного зрачка объектива канала измерения значения ЭПР на выходе приемного коллиматора от его окуляра должно быть в К_X раз меньше, чем удаление входного зрачка объектива канала измерения значения ЭПР от ОЭП в натурных (заданных) условиях локации.It follows from expression (33) that the receiving collimator reduces the scale of the beam emerging from it along the X axis with respect to the initial beam with a coefficient equal to

. This coefficient means that in order to comply with the spatial and energy similarity of the conditions for recording radiation reflected from the EED, the removal of the input pupil of the channel of the measurement channel of the EPR value at the output of the receiving collimator from its eyepiece should be K _X times smaller than the removal of the input pupil of the lens of the channel of measurement of the EPR value from OEP in full-scale (set) location conditions.

Since the distance between the eyepiece of the receiving collimator and the condenser lens is not specified in the claims of the patent No. 2202814, and the scale coefficients of conversion of the beam reflected from the OED along the Y axis and the X axis are not determined, then judge the distance between the entrance pupil of the OEP modeled by the receiving collimator and the receiver is not provided possible.

It was previously shown that the CCD matrix included in the prototype device is designed to register the reflection indicatrix of the EIA. In this case, the reflection indicatrix is registered only for the conditions of location in the far zone, corresponding to the infinite distance of the analysis plane from the located OED.

This fact is due to the fact that since the installation plane of the CCD matrix is optically conjugated to the focal plane of the projection system, the spatial distribution of the radiation intensity in this plane corresponds to the reflection indicatrix at an infinite range of the OED location, since the projection system performs the Fourier transform of the spatial and energy characteristics of the incident on it radiation beam [M. Russo, J.P. Mathieu, Problems in optics. M .: Mir, 1976, 414 pp., P. 388], valid only for the far zone.

Thus, the measurement of the EPR values of the OEP in the prototype device is carried out at an indefinite distance from the OEP to the receiver, and the reflection indicatrix is only in the far zone, corresponding to the infinite distance of the analysis plane from the located OEP. This fact leads to the presence of systematic errors in the measurement of the EPR and the indicatrix of the reflection of the EIA, due to unlawfulness:

comparing the results of measurements of the EPR values of the reflection indicatrix obtained with a receiver for one (unknown) location range and obtained with a CCD matrix for an infinite location range;

regulation of the measuring solid angle of averaging Ω _meas in accordance with the value of the measured retroreflectivity and the solid angle of averaging Ω _et , corresponding to the indicatrix of reflection from the reference reflector.

Thus, the presence of such irregularities leads to systematic errors in measuring the EPR and indicatrixes of reflection of the EIA using the prototype device.

1.5. The inability to determine the sign of curvature of the wave front of the reflection indicatrix of the EIA in the prototype device.

As shown earlier, the prototype device in addition to measuring the EPR allows you to register the reflection indicatrix of the EIA using a CCD matrix. However, since the installation plane of the CCD matrix is optically conjugated with the focal plane of the projection system, it is impossible to unambiguously determine the sign of the curvature of the wave front forming the reflection indicatrix of the OED. This is due to the fact that a spot is formed in the plane of the CCD array, the dimensions of which do not depend on the sign of curvature of the wave front of the diverging (positive radius of curvature) or converging (negative radius of curvature) laser beam.

The geometric meaning of this position is illustrated in FIG. 10. Figure 10 shows that:

at certain (for example, equal) angles of incidence of the extreme rays of diverging and converging bunches of laser radiation in the focal plane, radiation spots of the same diameter are formed;

information on the sign of curvature of the wave front by the diameter of the spot in the focal plane cannot be obtained.

Thus, the prototype device does not allow to determine the sign of curvature of the wave front of the measured reflection indicatrix.

1.6. The presence of systematic errors in the measurement of the amplitude characteristics of the OED reflection indicatrix due to the uncontrolled mode of operation of AGC systems in the electronic path of the CCD in the prototype device.

It is known that the electronic path of existing CCD-based matrices includes an AGC system [Pavlov NI, Prilipko A.Ya., Starchenko AN, Method and apparatus for obtaining maps of brightness coefficients. / Optical Journal, Volume 68, No. 6, 20001, p. 68]. In this case, the main purpose of the AGC is to smoothly adjust the accumulation time and control the "electronic shutter", which, in turn, provide a smooth adjustment of the level of the video signal at the output of the matrix. In the automatic mode of operation of the camera, the AGC loop “brings” the indicator of the generated image to the reference value. Usually it is set so that the average signal amplitude in the frame is at the level of 20 ... 30% of the maximum. It is known that the AGC of modern CCD-based cameras provide a smooth adjustment of the video signal level at the matrix output when the illumination level changes by two orders of magnitude. It should be noted that only in specialized cameras, in addition to automatic mode, manual or software control of the AGC parameters of the matrix based on the CCD is implemented [Pavlov N.I., Prilipko A.Ya., Starchenko A.N. Method and apparatus for obtaining maps of brightness coefficients. / Optical Journal, Volume 68, No. 6, 20001, p. 68].

At the same time, the type of CCD matrix is not indicated in the formula for the invention according to patent No. 2202814 from the point of view of implementing automatic, manual or software control mode of AGC parameters of the matrix based on CCD.

In turn, when using existing standard arrays based on the CCD of the CCD system, the AGC system will lead to the following.

As noted earlier, the goal of measuring the amplitude characteristics of the radiation reflected from an OEP is to further determine, based on the data obtained, the values of the effective scattering area of these OES. In this case, the EPR value can be determined by the value of the signal U ₀ reflected from the EIA, measured using a preliminary calibrated instrument using ES equipment.

It was previously shown that the most common calibration method is calibration using a reference reflector located at the same range as the investigated EIA. Given the linearity of the operating characteristics of the measuring device, the value of g _e is defined as

where σ _et - ESR ES (ES), U _et - the magnitude of the signal reflected from the MA.

From the expression (34) it follows that to measure the current values of the EPR of the EIA, it is necessary to calibrate the means for measuring the level of the received signal. In this case, the means of converting optical radiation into an electrical signal is a CCD matrix with an analog output. The signal from the matrix output is fed to the PC video adapter board and converted into an image on the monitor screen. The display mode of operation is, as a rule, monochrome, black and white, at which 256 gradations of brightness are displayed. Digitization of the image occurs with the current step of sampling the gradation of brightness. From the foregoing, the following requirements for the procedure and conditions for calibrating the measuring instrument and measuring the level of the signal received from the OED using the CCD matrix follow:

the matrix should work in linear mode;

the dynamic range of the electrical signal at the output of the matrix should be correlated with the dynamic range of the PC display, the operating point of the video adapter should be in the middle of the linear portion of the operating characteristic;

characteristics of the electric signal at the output of the matrix (average value and dispersion) when measuring ES should not differ significantly from the corresponding characteristics of the signal when measuring OEP.

However, it is known that the current EPR values of the investigated OEPs can significantly differ from the EPRs of the reference reflectors, and the levels of signals received from them can fluctuate depending on the simulated conditions of the optical location over a wide (previously unknown) range. In this case, the presence in the electron path of the existing matrices of CCD AGC systems will lead to digitization of the image with a different (depending on the maximum value of the irradiation on the matrix surface) step of sampling the brightness gradations. Or in other words, it will lead to systematic errors in the measurement of the amplitude characteristics of the OED reflection indicatrix due to the uncontrolled mode of operation of AGC systems in the electronic path of the CCD.

Thus, the presence in the electronic path of a device for measuring existing standard matrices based on the CCD of AGC systems will lead to systematic errors in measuring the amplitude characteristics of the reflection indicatrix of the OED due to the uncontrolled operation of AGC systems in the electronic path of the CCD. Moreover, as mentioned above, due to the uncontrolled operation of AGC systems in the electronic path of the CCD matrix, the measured EPR value can differ from the true value by two orders of magnitude.

The technical result of the claimed device for measuring the light scattering characteristics of optoelectronic devices is to increase the accuracy of the device by eliminating systematic errors due to the inability to:

- reproduction and control of the spatial characteristics of the probe radiation in the plane of the entrance pupil of the located OEP corresponding to a given location range by the forming optical system of the device;

- reproducing a predetermined range between the OEP and the receiver when measuring the EPR value and the reflection indicatrix of the OEP;

- taking into account the dependence of the current value of the EPR reference reflectors on the range of their location;

- determining the sign of curvature of the wavefront of the radiation reflected from the EIA;

- elimination of systematic errors in the measurement of the amplitude characteristics of the OED reflection indicatrix due to the uncontrolled mode of operation of AGC systems in the electronic path of the CCD.

The technical result is achieved due to the fact that in a known device for measuring the retroreflectivity of optoelectronic devices, containing a radiation source and sequentially installed in the course of its radiation forming an optical system, an inspected and reference retroreflectors, two beam splitters, a receiving collimator, the first projection system and the first the CCD matrix, while the output of the first CCD matrix is connected to the input of the microprocessor, the output of which is connected to the monitor, in addition between the receiving count the first transparent matte screen introduced from the eyepiece and the first projection system is installed from the eyepiece of the receiving collimator by a distance equal to the value of the modeled distance between the locator and the inspected light reflector divided by the square of the magnification of the receiving collimator multiplied by the root of the two, and the matte surface of the first transparent matte screen is optically coupled by the first projection system to the surface of the first CCD, while the forming optical system is made and three sequentially arranged along the radiation beam propagation collimators, a second beam splitter, a measuring collimator, a plane-parallel plate, a second opaque transparent screen, a second projection system and a second CCD, the forming collimators facing the radiation source with eyepieces, the optical axes of the forming collimators coincide with the optical axis the beam passing through them, the distances between the first and second, as well as the second and third forming collimators are equal to the sum e of the paraxial focuses of the lens of the previous collimator and the eyepiece of the next, the second beam splitter is installed in the optical gap between the second and third along the laser beam propagation by forming collimators at an angle to the optical axis of the radiation beam passing through it, the measuring collimator is located in the shoulder of the second beam splitter, which reflects incident on radiation beam facing the second beam splitter by the lens and its optical axis is aligned with the optical axis of the incident beam on the way A plane-parallel glass plate is installed at the angle of propagation of the beam emerging from the measuring collimator at an angle to the optical axis of the beam passing through it, a second opaque transparent screen, a second projection system and a second CCD matrix are sequentially installed on the path of the beam reflected from the plane-parallel glass plate, the second opaque transparent screen is installed perpendicular the optical axis of the incident beam, the center of the second matte transparent screen is aligned with the optical axis the beam incident on it, the optical axes of the second projection system and the second CCD matrix are perpendicular to the plane of the second matte transparent screen and aligned with its center, the matte surface of the second matte transparent screen by the second projection system is optically coupled to the surface of the second CCD matrix, with the reference reflector mounted next to inspected by a retroreflector in the probe beam, the output of the second matrix is connected to the input of the microprocessor, configured to calculate ESR reflector values inspected by the expression:

σ _b = g _et (L) U ₀ ,

,Where:

,

,

,

,

,

,

,

L is the value of the simulated distance between the locator and the inspected retroreflector;

R _s - the radius of curvature of the reflective surface of the ES;

ρ _z - reflection coefficient of the reflecting surface of the ES;

U ₀ is the magnitude of the signal proportional to the level of radiation reflected from the inspected retroreflector in the plane of its reception.

It was shown above that in the general case, the characteristics of the reflected OEP are substantially affected by the spatial conditions of the optical location, namely, the distance between the exit pupil of the IIS and the entrance pupil of the OEP. Moreover, depending on the simulated range of the OED location, the values of the angles of arrival of beams tangent to the hyperbolas of the beams in the entrance pupil of the OED should change by about two orders of magnitude.

It is known that, as a rule, collimators are used to transform the spatial characteristics of laser beams (cross-section and angular divergence). In this case, the basic requirements for such a collimator follow from the following geometric considerations:

the collimator should form a laser beam whose diameter is larger than the diameter of the entrance pupil of the investigated EIA;

the collimator should form a laser beam with an angular divergence, adjustable within a few tens of arc seconds.

The first condition is realized by selecting the diameters and focal lengths of the lens collimator. So the size of the diameter of the output lens should exceed the size of the diameter of the entrance pupil of the investigated OEP, and the value of the collimator magnification factor Gk (the ratio of the focus of the lens f _about the focus of the eyepiece f _ok ) should be selected based on the following ratio:

where Dob is the diameter of the collimator lens; d _IPI - the diameter of the laser beam at the output of the source of the damaging radiation.

So at Dob = 20 cm and d _un = 0.25 cm, the value of Gk should be at least 80.

However, it is known that the exact adjustment of the angular divergence of the laser beam within a few tens of arc seconds by changing the distance between the eyepiece and the collimator lens with a large magnification factor presents great technical difficulties, since in this case the movements of the eyepiece relative to the lens will amount to tenths-hundredths of a millimeter.

Moreover, the traditional methods for controlling the divergence of the laser spot [GOST 26086-84 Lasers. The methods for measuring the beam diameter and the energy divergence of laser radiation will lead to significant measurement errors, since the measured values of the angular divergence are within a few tens of arc seconds.

A known method and device for controlling the radius of curvature of the wavefront, providing the required accuracy of measuring the angular divergence of collimated laser beams [N. G. Kiselev, Control of the wavefront of the laser beam. Optical-mechanical industry, 1983, No. 4, pp. 13-14], which are based on the use of a shear interferometer. However, the installation procedures each time to measure the elements of the interferometer in the optical path of the stand, to align it, to control the radius of curvature of the wavefront and to calculate the angular divergence of the laser beam from this value using this device are quite laborious. Moreover, the accuracy of measuring the value of the radius of curvature of the wave front will be commensurate with the magnitude of the change in this radius due to a change in the angular divergence by units of seconds.

In order to simplify the procedures and improve the accuracy of reproduction and control of the spatial characteristics of the generated irradiating OEP beam in a known device for measuring the EPR (PSV) of optoelectronic devices containing a forming system (FS), it is proposed to perform this system in the form of three spatial-forming characteristics of the probe radiation in the plane of the collocated OEP of collimators (hereinafter simply forming collimators), a beam splitter, a measuring collimator, plane-parallel teklyannoy plate, transparent frosted screen, a projection system and a CCD matrix.

Moreover, in the forming system:

three forming collimators are located along the propagation of the radiation beam, are turned by eyepieces to the source of laser radiation and their optical axes coincide with the optical axis of the beam passing through them;

the distances between the first and second, as well as the second and third forming collimators are equal to the sum of the paraxial foci of the lens of the previous collimator and the eyepiece of the subsequent one;

a beam splitter is installed in the optical gap between the second and third along the propagation of the laser beam by forming collimators at an angle to the optical axis of the laser beam passing through it;

a measuring collimator is installed in the beam splitter arm, which reflects the laser beam incident on it, faces the beam splitter with the lens and its optical axis is aligned with the optical axis of the laser beam incident on it;

a plane-parallel plate is mounted on the propagation path of the laser beam emerging from the measuring collimator at an angle to the optical axis of the beam;

a transparent matte screen is mounted on the shoulder of a plane-parallel plate, which reflects the incident laser beam perpendicular to this beam, and the center of the screen is aligned with the optical axis of the incident beam;

the projection system and the CCD are sequentially installed in the path of propagation of the beam passing through the transparent matte screen;

the optical axis of the projection system and the CCD-based matrix are aligned with the optical axis of the beam passing through the transparent matte screen;

the matte surface of the screen by the projection system is optically coupled to the surface of the CCD.

The division of the FS into three forming collimators arranged in series on a single optical axis and a separate measuring collimator is proposed based on the following considerations.

The first forming collimator performs preliminary expansion of the beam of the probe radiation source (ZI) and forms a beam at the output with the smallest possible divergence. The second forming collimator is designed to smoothly change the angular divergence of the ZI beam passing through it. Since a smooth change in the angular divergence in the case under consideration is achieved by smoothly changing the distance between his eyepiece and lens, the value of its magnification factor should be small (of the order of 1-2). The third forming collimator along the beam carries out the final expansion of the ZI beam to the required dimensions and forms an almost parallel beam. In this case, the total coefficient of increase in the system of three forming collimators should be equal to Gk, the requirements for the value of which are defined above (see (37)).

The numerical values of the magnification factors of the first and third forming collimators are selected based on the following provisions.

It was previously indicated that during the experiments, the task arises of controlling the exposure conditions of the entrance pupil of the investigated EIA (the divergence of the ZI beam irradiating the entrance pupil), the solution of which by traditional methods leads to large errors and labor costs. In order to improve the accuracy of measuring the angular divergence of the beam irradiating the entrance pupil of the OED beam, a method is proposed, the essence of which is as follows.

A first beam splitter is installed in the optical gap between the second and third forming collimators at an angle to the beam axis, the transverse dimensions of which exceed the diameter of the beam passing through them. On the axis of the beam reflected by the first beam splitter, a measuring collimator is installed with a lens to it, at the output of which a meter for the angular divergence of the ZI beam is installed. Let the magnification factor of the third forming collimator be equal to Г3, and the measuring Ги. From simple geometric considerations it follows that:

since when the divergence of the beam at the input of the third forming and measuring collimators is N times the beam divergence at the output of the third forming collimator changes N / G3 times, and at the output of the measuring collimator N · Gy times, the accuracy of measuring the angular divergence due to the use of the measuring collimator increases G3 × Gu times;

in order to increase the accuracy of measuring angular divergence due to the use of a measuring collimator, the values of the magnification factors G3 and Gi should be selected as high as possible.

In this case, the value of the increase factor Gi is limited only by the presence of good quality lenses with the largest and minimum focal lengths. The prototyping of the optical path of the beam forming system (TFP) ZI showed that the rational (technically feasible) values of the magnification factors of the forming and measuring collimators are as follows: Г3 = 10 and Ги = 20. In this case, when the angular divergence at the input of the third forming and measuring collimators changes by 10 arc seconds, the angular divergence at the output of the third forming collimator increases by 1 arc second, and at the output of the measuring collimator by 200 arc seconds (by almost three and a half minutes). This fact allows us to conclude that the use of the proposed scheme makes it possible to increase the accuracy of measuring the angular divergence of the beam at the output by a factor of 3 × Gy. From the expression (35) it follows that when the magnification factor of the second collimator is 2, the magnification factor of the first collimator should be at least 4.

When determining the distances between the forming collimators, the following provisions were taken into account, according to which [I.I. Pakhomov, A.B. Tsibulya, Calculation of optical systems of laser devices. M .: Radio and communication, 1986, 151 pp.]:

when combining the front focus of the lens with the constriction plane, the constriction of its converted beam is located in the rear focal plane of this lens;

when combining the front focus of the lens with the constriction plane, a beam is formed with a minimum angular divergence;

when the distance between the output lens of the first collimator and the input lens of the second collimator is equal to the sum of their focal lengths and each one is set to a minimum of divergence, a beam with a minimum divergence is also formed at the output of the second collimator.

It is proposed to solve the problem of measuring the angular divergence of the beam at the output of the measuring collimator using an appropriate meter, consisting of a plane-parallel glass plate located downstream of the measuring collimator and reflecting part of the incident beam onto the surface of the first matte transparent screen, the first projection system, and the first matrix onto Based CCD. Wherein:

a plane-parallel plate is mounted on the propagation path of the laser beam emerging from the measuring collimator at an angle to the optical axis of the beam;

a transparent matte screen is mounted on the shoulder of a plane-parallel plate, which reflects the incident laser beam perpendicular to this beam, and the center of the screen is aligned with the optical axis of the incident beam;

the projection system and the CCD are sequentially installed in the path of propagation of the beam passing through the transparent matte screen;

the optical axis of the projection system and the CCD-based matrix are aligned with the optical axis of the beam passing through the transparent matte screen;

the matte surface of the screen by the projection system is optically coupled to the surface of the CCD.

As shown in [N.G. Kiselev, Control of the wavefront of a laser beam. Optical-mechanical industry, 1983, No. 4, pp. 13-14], due to the interference of beams reflected from the flat surfaces of a plane-parallel glass plate on the matte surface of the first screen, an interference pattern in the form of stripes will be formed. In this case, the distance between the bands Δh will definitely depend on the following parameters:

the radius of curvature of the wave front (angular divergence) of the beam R incident on the plate;

the thickness of the plane-parallel glass plate H;

angle between the normal to the surface of a plane-parallel glass plate and the optical axis of the incident beam α.

According to [N.G. Kiselev, Control of the wavefront of a laser beam. Optical-mechanical industry, 1983, No. 4, pp. 13-14], stated above and geometric considerations, it follows that the calculation of the angular divergence at the output of the third collimator (in the plane of the entrance pupil of the inspected OEP) can be carried out using the following expression:

Where:

d _OEP - diameter of the entrance pupil of the inspected OEP (retroreflector);

To ₃ and To _and - the magnification factors of the third forming and measuring collimators;

N is the refractive index of the glass of a plane-parallel glass plate;

λ is the wavelength of the probe radiation;

Δt is the distance between interference fringes;

R is the radius of curvature of the wavefront at the output of the measuring collimator.

The calculation of the angular divergence at the output of the third forming collimator (in the plane of the entrance pupil of the inspected OEP) can be carried out using the appropriate program embedded in the microprocessor, to the input of which a CCD camera is connected, which constructs an image of the interference pattern on a transparent matte screen of the forming system.

It is obvious that the more matrix elements fall on the distance between the Δt bands, the higher will be the accuracy of measuring the angular divergence of the beam. This implies the need, first, for the formation of bands with the largest possible sizes on the screen, and, secondly, for choosing the focal length of the first projection system at which the image of the bands on the surface of the CCD will be quite large.

Increasing the distance between the strips Δt on the screen can be achieved by the following known measures:

reducing the thickness of the plane-parallel glass plate;

decreasing the angle between the normal to the surface of a plane-parallel glass plate and the optical axis of the incident beam;

two measures listed above.

Thus, the implementation of the forming system as a part of three forming collimators, a beam splitter, a measuring collimator, a plane-parallel glass plate, a transparent matte screen, a projection system, and a CCD matrix will improve the accuracy of measuring the light scattering characteristics of OEDs in G3 × Gy times by eliminating systematic errors associated with reproduction and control of the spatial characteristics of the probe radiation in the plane of the entrance pupil of the located OEP corresponding to a given yes nosti locations forming the optical system of the device.

. Этот факт означает, что для соблюдения пространственного, а главное, энергетического подобия условий регистрации отраженного от ОЭП излучения диаметр входного зрачка объектива (согласно формуле изобретения по патенту №2202814 - конденсорной линзы) канала измерения значения ЭПР на выходе приемного коллиматора должен быть в К_Y раз меньше, чем диаметр входного зрачка объектива канала измерения значения ЭПР в натурных условиях.In turn, in Section 1.3 of this description, it was shown that the receiving collimator reduces the scale of the beam emerging from it along the Y axis with respect to the initial beam with a coefficient equal to

. This fact means that in order to comply with the spatial, and most importantly, the energy similarity of the registration conditions of the radiation reflected from the OED, the diameter of the entrance pupil of the lens (according to the claims of patent No. 2202814 - a condenser lens) of the channel for measuring the EPR value at the output of the receiving collimator must be K _Y times smaller than the diameter of the entrance pupil of the objective of the channel measuring the EPR value in natural conditions.

. Этот означает, что для соблюдения пространственного и энергетического подобия условий регистрации отраженного от ОЭП излучения, удаление входного зрачка объектива канала измерения значения ЭПР на выходе приемного коллиматора от его окуляра должно быть в К_Х раз меньше, чем удаление входного зрачка объектива канала измерения значения ЭПР от ОЭП в натурных (заданных) условиях локации. Эти положения автоматически относятся и к значению расстояния между окуляром приемного коллиматора и плоскостью анализа индикатрисы отражения исследуемого ОЭП в лабораторных условиях.In addition, in paragraph 1.3 it is shown that the receiving collimator reduces the scale of the beam emerging from it along the X axis with respect to the initial beam with a coefficient equal to

. This means that in order to comply with the spatial and energy similarity of the conditions for recording radiation reflected from the EED, the removal of the entrance pupil of the channel of the measurement channel of the EPR value from the output of the receiving collimator from its eyepiece should be K _X times smaller than the removal of the entrance pupil of the lens of the channel of measurement of the EPR value from OEP in full-scale (given) location conditions. These provisions automatically apply to the value of the distance between the eyepiece of the receiving collimator and the plane of analysis of the reflection indicatrix of the investigated EIA in laboratory conditions.

Thus, only the fulfillment of the above conditions will provide an increase in the accuracy of measuring the light scattering characteristics of the EIA due to the elimination of systematic measurement errors associated with the reproduction of a given range between the inspected EIA and the receiver.

In the claimed invention, the inspected EIA and the reference retroreflector are irradiated with a practically collimated beam. Consider the effect of the relationship between the radius of curvature of the ES and the range of the location on the value of the PSV of the ES when it is irradiated with a collimated beam. It is known that when the source is removed from the irradiated object at a distance tending to infinity, the radiation front will fall almost flat (as in a collimated beam). It follows from expression (18) that as L1 → ∞ it reduces to the following form:

where L in the case under consideration is equal to the value of the simulated range between the OEP and the receiving channel of the locator.

From the expression (38) it follows that the current value of ESR ES at a distance L should be calculated by the formula:

where the value of σ _{et is} calculated using expression (10).

In this case, the microprocessor must calculate the EPR value of the investigated EIA (retroreflector) σ _sv in accordance with the following expression:

,Where

,

where U _et - the magnitude of the signal proportional to the level of radiation reflected from the ES in the plane of its reception.

In paragraph 1.5, it was shown that since the installation plane of the CCD matrix in the prototype device is optically conjugated with the focal plane of the projection system, the sign of curvature of the wave front forming the reflection indicatrix of the EIA cannot be unambiguously determined.

It is proposed to solve the problem of determining the sign of curvature of the wavefront of the radiation reflected from the OED using an appropriate meter, consisting of a beam of a first opaque transparent screen, a first projection system, and a first CCD matrix coming out of the receiving collimator. In this case, the first opaque transparent screen is installed perpendicular to the optical axis of the receiving collimator, and the center of the first matte transparent screen is aligned with the optical axis of the beam coming out of the receiving collimator, the optical axes of the first projection system and the first CCD are aligned with the optical axis of the beam coming out of the receiving collimator, and the matte the surface of the first opaque transparent screen using the first projection system is optically coupled to the surface of the first CCD.

The use of the first matte transparent screen eliminates the ambiguity in the sign of the radius of curvature of the beam emerging from the receiving collimator. So, from physical considerations, it follows that at the same divergence angles of the beam, the diameter of the spot from the converging beam will be less than the diameter of the diverging one. In this case, the linear dimensions of the spot on the first matte transparent screen will be proportional to the angular divergence of the beam at the output of the receiving collimator. When the matte surface of the first screen by the projection system is optically coupled to the surface of the CCD, a clear image of the spot is formed on the matrix surface on the first matte transparent screen.

From the laws of geometric optics it follows that:

the linear dimensions of the spot on the first matte transparent screen (matrix) will be proportional to the angular divergence of the beam at the output of the receiving collimator;

the distribution of the radiation intensity in the spot on the first matte transparent screen and on the surface of the first CCD will be proportional to the distribution of the intensity of the reflection indicatrix in the analysis plane that is remote from the OED at a given distance;

the angular divergence of the reflection indicatrix in the plane of analysis will be proportional to the angular divergence of the reflection indicatrix at the OEP output.

The latter fact allows the measurement of the angular divergence of the reflection indicatrix using a CCD matrix.

In order to calibrate the meter of angular divergence of the reflection indicatrix at fixed values of the magnification factor of the receiving collimator, the distance between the eyepiece of the receiving collimator and the first matte transparent screen, the focus of the first projection system, its distance from the first matte transparent screen and the conditions for normalizing the spot, the angular divergence of the reflection indicatrix is determined, attributable to one element of the CCD camera matrix. To do this, a flat mirror is installed in place of the OED under study, the diameter of the formed spot is measured on the first matte transparent screen d ₁ with the initial divergence of the beam irradiating the mirror. The divergence of the beam irradiating the mirror doubles. The diameter of the new spot d _{2 is} measured. The value of half the increment of the spot diameter is calculated by increasing the beam divergence Δd = (d ₁ -d ₂ ) R. The increment of the beam divergence Δα is known. The unit price of a linear quantity on the first matte transparent screen in units of the angular divergence of the reflection indicatrix is calculated by the formula

.

.

The current value of the divergence of the reflection indicatrix is determined directly from the current values of the spot image size on the first matte transparent screen by conducting appropriate processing of the measurement results of this size using a microprocessor connected to the output of the CCD camera.

Thus, the introduction to the prototype device of the first matte transparent screen located between the receiving collimator and the first projection system allows us to eliminate the systematic error associated with the sign of the curvature of the radiation beam of the OEC reflection indicatrix.

In Section 1.6, it was shown that the current EPR values of the inspected EIAs can significantly differ from the EPRs of reference retroreflectors, and the levels of signals received from them can vary depending on the simulated conditions of the optical location over a wide (not previously known) range. In this case, the presence in the electron path of the existing matrices of CCD AGC systems will lead to digitization of the image with different (depending on the maximum value of the irradiation on the matrix surface) discretization of the gradation of brightness, and therefore to systematic errors in measuring the amplitude characteristics of the reflection characteristic of the OED.

It is obvious that this drawback can be eliminated only in the case when the image is digitized by the EIA reflection indicator and reference reflectors with the same current step of sampling the brightness gradations. To ensure this condition in the proposed device, the measurement of the amplitude characteristics of the reflection indicatrix of the EIA is proposed to be performed simultaneously with the measurement of the amplitude characteristics of the reflection indicatrix of the ES. To achieve this condition, in the process of measuring the reflection indicatrix of the investigated OED, a reference retroreflector is installed next to the entrance pupil of this OED in the probe beam.

In this case, the reference reflector should preferably be a flat round mirror or a mirror spherical reflector with a large radius of curvature of its reflecting surface. This requirement is due to the following reasons.

It is known that the indicatrix of reflection of reference specular spherical reflectors with a small value of the radius of curvature is relatively wide. In this case, the spot from the beam of radiation reflected from the ES emitted from the measuring collimator will be comparable with the size of the screen and will be superimposed on the spot from the beam of radiation reflected from the OED that has left the measuring collimator, which will lead to errors in the measurement of the EPR value of the EED.

At the same time, the spot from the reflected beam emerging from the measuring collimator from a flat mirror or ES with a large radius of curvature will not overlap the spot from the reflected beam coming out of the measuring collimator from the OED radiation and will be close to it because:

the reflection indicatrix of flat reference mirror reflectors or ES with a large radius of curvature is relatively narrow and the spot from the beam of radiation reflected from the flat mirror emerging from the measuring collimator will be relatively small;

By changing the angular position of a flat mirror or ES with a large radius of curvature, you can adjust the position of the spot from the mirror on the screen relative to the spot from the EIA.

Figure 11 shows the images of the reflection indicatrixes of a night vision device of type 1PN57 and ES with the radius of curvature of its surface equal to 15 m obtained using the layout of the proposed device. The reflection indicatrix 1PN57 has the shape of a hollow cone with a central lobe inside, and the reflection reflection indicatrix has the shape of a cone with an almost uniform intensity distribution over the cross section. The intensity distribution on the screen was recorded using a camera based on a CCD matrix and fed into the ADC (frame grabber) as an analog signal. Then the image in digital format was read, processed and displayed on a computer monitor using the LIR-300PC program from Spiricon.

The EPR value of a flat circular specular reflector σ _pk can be determined using the following expression [A. G. Saibel, Basics of radar. M .: Gosenergoizdat, 1961, 384 p., P. 42]:

where: ρ _z - reflection coefficient of the mirror surface;

S is the area of the mirror;

λ is the wavelength of the probe radiation.

So at a mirror diameter of 1 cm, ρ _s = 0.9 and λ = 1 μm, σ _{pk is} approximately equal to 7 × 10 ⁴ m ² . Considering the fact that the EPR of real SES samples is about an order of magnitude or more smaller than the indicated value, a flat glass plate with one side opaque or a dense neutral light filter can be used as a reference. In this case, the plate should be installed with the flat side to the radiation incident on it. In this case, reflection will occur only from one surface, the reflection coefficient of which is approximately 0.05. Calculations show that the EPR of such a retroreflector will decrease to a value of about 4 × 10 ³ m ² . If necessary, a further reduction in the EPR can be achieved by installing a neutral filter with a known transmittance in front of the reflector.

Thus, the installation of a reference retroreflector next to the EIA being studied when measuring the EPR and reflection indicatrix will provide an increase in the accuracy of measuring the EPR of the EEP by about an order or more by eliminating systematic measurement errors caused by digitizing the image with different (depending on the maximum value of irradiation on the surface matrices) by a step of discretization of gradations of brightness.

Since in this case the measurement of the energy and spatial characteristics of the reflection indicatrix can be carried out only using a CCD matrix, the need to include a condenser lens, a receiver, and a digital voltmeter in the optical path of the test bench is no longer necessary.

Thus, the claimed device has the properties consisting in the possibility of measuring the light scattering characteristics of the EIA with the practical complete elimination of systematic errors associated with:

the dependence of the current value of the reference EPR reflectors on the range of their location;

reproducing the spatial characteristics of the probe radiation in the plane of the entrance pupil of the located OEP corresponding to a given range of location;

control of spatial characteristics of the probe radiation in the plane of the entrance pupil of the located OEP corresponding to a given location range;

determination of the sign of curvature of the wave front of the reflection indicatrix of the EIA;

uncontrolled mode of operation of AGC systems in the electronic path of the CCD.

The inventive device has properties that do not match the properties shown by the distinguishing features in the known solutions and are not equal to the sum of these properties. The inventive device provides a positive effect, which consists in increasing the accuracy of measuring the light scattering characteristics of the OED by eliminating systematic errors associated with the reproduction and control of a given range of location, measuring the sign of curvature of the wavefront reflected from the OEP, not controlled by the operating mode of the AGC systems in the electronic path of the CCD and the dependence of the current value of the EPR of the reference reflectors on the range of their location.

Figure 1 presents the structural diagram of the proposed device.

Figure 2 shows the progress of the rays passing in the forward direction during the location of the OED in a converging beam.

Figure 3 shows the progress of the rays passing in the forward and reverse directions during the location of the EIA in a converging beam.

Figure 4 shows the course of the rays in the process of irradiation of the ES and reflection from it of the radiation of a point source of ZI.

Figure 5 shows an image of a hyperbola explaining the physical meaning of parameters a and b.

Figure 6 shows an image of a hyperbola explaining the physical meaning of the parameter ΔX.

Figure 7 shows a graphical dependence of the angle of arrival of tangents to the hyperbolas of the beams in the entrance pupil of the OEP from the range of its location.

Figure 8 shows the calculated dependences of the displacement of the image analysis plane relative to the paraxial focus of the OED lens on the focusing distance for three types of lenses.

Figure 9 shows the path of the rays when focusing beams with different radii of curvature of the wave front.

Figure 10 shows the image of the reflection indicatrix of the night vision device type 1PN57 and ES with a radius of curvature of the reflector equal to 15 m, obtained using the layout of the proposed device.

Figure 11 shows the appearance of the system for the formation of probe radiation of the layout of the proposed device.

On Fig, 13 shows the appearance of the receiving collimator, the second matte screen, the projection system and the CCD.

The proposed device contains (see Figure 1): a radiation source (laser) 1, the forming system 2, the first beam splitter 3.1, the inspected 4 and the reference 5 retroreflectors, a receiving collimator 6, the first transparent matte screen 7.1, the first projection system 8.1, the first matrix CCD 9.1, microprocessor 10 and monitor 11. In this case, the forming system is made of three forming collimators 12.1, 12.2 and 12.3, a second beam splitter 3.2, a measuring collimator 13, a plane-parallel glass plate 14, a second transparent frosted screen 7.2, and a second projection translational systems 8.2 and 9.2 second CCD.

The first beam splitter 3.1 is installed between the third forming collimator 12.3 and the inspected 4 and reference 5 retroreflectors. The reference reflector 5 is installed next to the entrance pupil of the inspected reflector 4 in the radiation beam. The receiving collimator 6 is installed in the shoulder of the first beam splitter 3.1, which reflects the incident beams of radiation reflected from the inspected reflector 4 and the reference reflector 5, facing the first beam splitter 3.1 with a lens and its optical axis is aligned with the optical axis of the incident beam. The first frosted transparent screen 7.1, the first projection system 8.1 and the first CCD 9.1 matrix are sequentially mounted on the propagation path of the radiation beam emerging from the receiving collimator 6, the first frosted transparent screen 7.1 is installed perpendicular to the optical axis of the receiving collimator 6. The center of the first screen 7.1, the optical axes of the first projection systems 8.1 and the first CCD 9.1 matrix are aligned with the optical axis of the beam emerging from the receiving collimator 6. The matte surface of the first screen 7.1 is removed from the eyepiece of the receiving collimator 6 by a distance equal to the value of the simulated distance between the locator and the inspected retroreflector, divided by the square of the magnification factor of the receiving collimator 6, multiplied by the root of two. The first projection system 8.1 matte surface of the first screen 7.1 is optically paired with the surface of the first matrix on the CCD 8.1.

The forming collimators 12.1, 12.2 and 12.3 of the forming system 2 are turned by the eyepieces to the radiation source 1. The optical axes of the collimators 12.1, 12.2 and 12.3 coincide with the optical axis of the beam passing through them, the distances between the first 12.1 and second 12.2, as well as the second 12.2 and third 12.3 forming collimators are equal to the sum of the paraxial focuses of the lens of the previous forming collimator and the eyepiece of the subsequent one. The second beam splitter 3.2 is installed in the optical gap between the second 12.2 and third 12.3 along the laser beam propagation by the forming collimators at an angle to the optical axis of the beam passing through it, the measuring collimator 13 is located in the shoulder of the second beam splitter 3.2, which reflects the incident beam on it, facing the second a beam splitter 3.2 with the lens and its optical axis aligned with the optical axis of the incident beam. A plane-parallel plate 14 is mounted on the propagation path of the beam emerging from the measuring collimator 13 at an angle α to the optical axis of the beam passing through it. The second opaque transparent screen 7.2, the second projection system 8.2 and the second CCD 9.2 matrix are sequentially mounted on the propagation path of the beam reflected from the plane-parallel plate 14. The second opaque transparent screen 7.2 is mounted perpendicular to the optical axis of the incident beam, the center of the second opaque transparent screen 7.2 is aligned with the optical axis of the incident beam. The optical axes of the second projection system 8.2 and the second CCD 9.2 matrix are perpendicular to the plane of the second opaque transparent screen 7.2 and aligned with its center. The matte surface of the second opaque transparent screen 7.2 of the second projection system 8.2 is optically coupled to the surface of the second CCD matrix 9.2.

The outputs of the first 9.2 and second matrix 9.2 are connected to the input of the microprocessor 10, configured to calculate the EPR value of the inspected retroreflector by the expression:

σ _b = g _et (L) U ₀ ,

,Where:

,

,

,

,

,

,

,

where L is the value of the simulated distance between the locator and the inspected retroreflector;

R ₃ is the radius of curvature of the reflective surface of the ES;

ρ ₃ - reflection coefficient of the reflecting surface of the ES;

U ₀ is the magnitude of the signal proportional to the level of radiation reflected from the inspected retroreflector in the plane of its reception.

The output of the microprocessor 10 is connected to the input of the monitor 11.

A device for measuring the light scattering characteristics of an OEP works as follows.

The radiation of the laser 1 is directed to the input of the first forming collimator 12.1 of the forming system 2. The forming collimator 12.1 increases the diameter of the input beam by a factor of K1 and reduces its divergence also by approximately K1. The radiation from the output of the first shaping collimator 12.1 goes to the input of the second shaping collimator 12.2 of shaping system 2. The second shaping collimator 12.2 increases the diameter of the input beam by a factor of K2 and decreases its divergence by about a factor of K2 as well. The radiation from the output of the second shaping collimator 12.2 hits the input of the third shaping collimator 12.3 of the shaping system 2. The third shaping collimator 12.3 increases the diameter of the input beam by a factor of K3 and decreases its divergence also by about K3 times. Thus, a beam is formed at the output of the third forming collimator 12.3, the diameter of which is K1 × K2 × K3 times the diameter of the original laser beam, and its divergence is approximately K1 × K2 × K3 less than the divergence of the original laser beam. Alignment of the first forming collimator 12.1 to the minimum of the angular divergence of the beam at its output, as well as combining the paraxial focuses of the eyepieces of each subsequent forming collimator with the lens of each previous one, ensures the alignment of the forming system 2 to the minimum of the beam divergence at its output, which means that the conditions for reproducing the maximum range locations.

By changing the position of the lens of the forming collimator 12.2 relative to its eyepiece, you can change the value of the parameter K2, which will lead to a change in the divergence of the beam at the output of the forming system 2 as a whole. Changing the beam divergence at the output of the forming system 2 makes it possible to reproduce the irradiation conditions of the entrance pupil of the investigated EIA corresponding to a given location range.

Part of the radiation reflected by the second beam splitter 3.2 falls on the lens of the measuring collimator 13. The radiation transmitted through this collimator decreases in diameter by a factor of Ki, and its divergence increases by a factor of Ki. The radiation emerging from the eyepiece of the measuring collimator 13 is incident on a plane-parallel glass plate 14. The radiation reflected from the front and rear surfaces of the plane-parallel glass plate 14 is incident on a second matte screen 7.2 and forms an interference pattern in the form of stripes on it. The width of the strips and the distance between them on the second opaque transparent screen 7.2 for fixed values of the angle between the normal to the plane of the plate and the axis of the incident beam, the thickness of the plane-parallel glass plate and its refractive index depend on the radius of curvature of the wave front of the incident beam (its angular divergence ) The second projection system 8.2 builds an image of the stripes on the second matte transparent screen 7.2 on the surface of the second CCD 9.2 matrix. In turn, since the angular divergence of the beam at the output of the measuring collimator 13 is Ki × K3 times greater than at the output of the third forming collimator 12.3 (forming system 2), this allows us to increase the accuracy of measuring the angular divergence of the beam at the output of the third by Ki × K3 forming collimator 12.3 (forming system 2).

Formed by the forming system 2 (forming collimator 12.3), the radiation beam is directed towards the first beam splitter 3.1, inspected 4 and the reference retroreflectors 5.

Inspected 4 and reference retroreflectors 5 reflect the radiation incident on them in the opposite direction (to the surface of the first beam splitter 3.1). The radiation incident on the first beam splitter 3.1 and reflected by the inspected 4 and reference retroreflectors 5 is reflected by the first beam splitter 3.1 in the direction of the lens of the receiving collimator 6. The diameter of the radiation beam transmitted through the receiving collimator 6 decreases by a factor of _Y , and its divergence increases by a factor of _Y.

The radiation emerging from the eyepiece of the receiving collimator 6 falls on the first transparent matte screen 7.1, the first projection system 8.1 builds an image of this spot on the surface of the first CCD of the CCD 9.1. The linear dimensions of the spot on the first transparent matte screen 7.1 and on the surface of the first CCD 8.1 matrix, as well as the intensity distribution over the cross section of the spot will be proportional to the diameter of the radiation beam passing through the receiving collimator 6, its divergence and the intensity distribution over the beam cross section at the output of the receiving collimator 6 (indicatrix reflection of the EIA). Moreover, since the matte surface of the first screen 7.1 is removed from the eyepiece of the receiving collimator 6 by a distance equal to the simulated distance between the locator and the inspected retroreflector, divided by the square of the magnification factor of the receiving collimator 6, multiplied by the root of two, the linear dimensions of the spot on the first transparent matte screen 7.1 and on the surface of the first CCD 9.1 matrix, as well as the intensity distribution over the spot cross section will be proportional to the divergence and intensity distribution over the cross section reflected from the inspected EIA and EC of the beam on the real range.

The signals from the output of the CCD matrices 9.1 and 9.2 are fed to the input of the microprocessor 10, the output of which is connected to the monitor 11, while the microprocessor 10 calculates the EPR value σ _sv or the reflectance index R _{sv of the} inspected retroreflector (OEP) in accordance with expression (44).

The proposed technical solution is technically feasible, since for its implementation typical optical and radio components and devices can be used, namely:

collimators based on telephoto lenses and short-focus eyepieces;

plane-parallel glass plates;

frosted transparent screens (plane-parallel glass plates, in which one side is frosted);

television matrices based on charge-coupled devices (CCD);

video capture cards for interfacing television matrices with a microprocessor.

By the applicant’s efforts, a ball was developed and made a model of the proposed device, which successfully passed an experimental test, which confirmed the technical feasibility of the proposed technical solution.

The appearance of the elements of the optical path of the layout is shown in Fig.12 and Fig.13.

This device allows to increase the accuracy of measuring the light scattering characteristics of the EIA by reducing systematic errors associated with the dependence of the current value of the EPR reference reflectors on the range of their location up to 5 times associated with the reproduction of the spatial characteristics of the probe radiation in the plane of the entrance pupil of the located OEP corresponding to an unknown range of the location of the forming the optical system of the device, as well as the inability to control the spatial characteristics of the probing about the radiation in the plane of the entrance pupil of the located OED more than an order of magnitude associated with measuring the reflection indicatrix only in the far zone, corresponding to the infinite distance of the analysis plane from the located OEP, the impossibility of determining the sign of curvature of the wavefront of the OEC reflection indicatrix, as well as the uncontrolled mode of operation of the systems AGC in the electronic path of the CCD matrix is more than an order of magnitude.

Claims (1)

A device for measuring light scattering characteristics, containing a radiation source and forming an optical system, inspected and reference retroreflectors, two beam splitters, a receiving collimator, a first projection system and a first CCD matrix, the first CCD matrix connected to the microprocessor input, the output which is connected to a monitor, characterized in that in addition between the receiving collimator and the first projection system introduced the first transparent matte the th screen installed from the eyepiece of the receiving collimator by a distance equal to the value of the simulated distance between the locator and the inspected retroreflector, divided by the square of the magnification of the receiving collimator, multiplied by the root of two, and the matte surface of the first transparent matte screen of the first projection system is optically coupled to the surface of the first CCD arrays, while the forming optical system is made of three sequentially located along the propagation beam forming collimators, a second beam splitter, a measuring collimator, a plane parallel plate, a second opaque transparent screen, a second projection system and a second CCD matrix, the forming collimators facing the radiation source with eyepieces, the distances between the first and second, as well as the second and third forming collimators are equal to the sum paraxial focuses of the lens of the previous collimator and the eyepiece of the next, the second beam splitter is installed in the optical gap between the second and third along the laser beam propagating by forming collimators at an angle to the optical axis of the radiation beam passing through it, the measuring collimator is located in the shoulder of the second beam splitter, which reflects the incident radiation beam and faces the second beam splitter, along the propagation path of the beam emerging from the measuring collimator at an angle to the optical an axis of a beam passing through it has a plane-parallel glass plate mounted on the propagation path reflected from the plane-parallel plate the second matte transparent screen, the second projection system and the second CCD matrix, the second matte transparent screen is mounted perpendicular to the optical axis of the incident beam, the matte surface of the second matte transparent screen is optically paired with the surface of the second CCD matrix, and the reference reflector installed next to the inspected retroreflector in the probe beam, the output of the second matrix is connected to the input of the microprocessor, configured to calculate the EPR value of the inspected retroreflector by expression

,

, Where

L is the value of the simulated distance between the locator and the inspected retroreflector; R ₃ is the radius of curvature of the reflective surface of the ES; ρ ₃ - reflection coefficient of the reflecting surface of the ES; U ₀ is the magnitude of the signal proportional to the level of radiation reflected from the inspected retroreflector in the plane of its reception; U _em - the magnitude of the signal proportional to the level of radiation reflected from the reference reflector in the plane of its reception.

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