Method for one-positional measurement of laser emission source coordinates and device for realization of said method

FIELD: quantum electronics, possible use for engineering of precision systems, systems for precise targeting of narrow laser rays, trajectory measurements, counting and displaying information, and also for engineering of systems for precise determination of direction to sources of optical emission of space-based equipment, in particular, for tuning of antennas of large radio-telescopes and for communications engineering.

SUBSTANCE: in known method for one-positional measurement of angular coordinates of laser emission source, based on use of scanning optical systems and determination of angular coordinate of laser emission source on basis of angular position of scanning system at the moment when maximum value of useful signal is achieved, scanning of vicinity in selected observation sector is performed due to alternation of heterodyne signal phase front position, and angular coordinate of laser emission source is determined on basis of its angular position at the moment when maximum value of useful signal is achieved. Device for realization of method consists of photo-detector mounted on rotary platform with forming optics and of semi-transparent, held, mounted at an angle of 45° to optical axis, plate, block for processing signal at output of photo-detector, heterodyne, and also of serially connected block for forming parameters of phase front of heterodyne signal and block for controlling phase front of heterodyne signal, while second output of block for forming parameters of phase front of heterodyne signal is connected to second output of signal processing block, second input of block for controlling phase front of heterodyne is connected to output of heterodyne, and output - to second input of photo-detector.

EFFECT: decreased space observation time and increased precision of measurements of laser emission source coordinates.

2 cl, 5 dwg

The invention relates to the field of quantum electronics and can be used in precision systems for accurate targeting a narrow laser beams, the system trajectory measurements, systems, accounts and information display, as well as in systems accurately determine the direction to the source of optical radiation and space technology, in particular when aligning the antennas of large radio telescopes, and in communications technology.

The known method single-station measurements of the angular coordinates of the laser light source (analog), based on the use of line of photosensitive elements (see, for example, Vorob'ev V.I. Optical location for radio engineers. - M.: Radio and communication, 1983, p.108, 170). The determination of the direction to the source of laser radiation is carried out on the coordinate corresponding to the receiver element, which is formed by the spot of the laser radiation. The method can be implemented, for example, using a device containing forming optics in the focal plane where the silicon multielement code sensor and processing unit of the electric signals from the photodetector (see, for example, Opto-mechanical devices, No. 2, 1983, p.45).

The main disadvantages are the counterpart large measurement error of the direction to the source of laser radiation and low UB is Yan noise immunity. In addition, to determine the spatial direction to the source of laser radiation required two similar devices placed in the elevation and azimuth planes.

There is also known a method, based on the total differential processing of the electrical signals at the output of multi-channel detectors of optical radiation. The method can be implemented using a device determining the angular coordinates of the source of laser radiation, containing one four-quadrant photodetector located in the focal plane forming optics with a round aperture, and the block sum-dierence processing of electrical signals. The direction of arrival of the laser radiation is determined by the position of the diffraction spots on the four-quadrant receiver (see, for example, Vorob'ev V.I. Optical location for radio engineers. - M.: Radio and communication, 1983, str).

The disadvantages of this method are the large errors in determining the coordinates of the source of laser radiation and low efficiency in conditions of natural and intentional interference.

The closest in technical essence (prototype) to the claimed invention is a method constitutive dimension of the coordinates of the laser light source based on the application of scanning optical systems and determining the angular coordinates of the source is the infrared laser beam on the angular position of the scanning system at the time of achievement of the useful signal, formed as the result of beating oscillations of the laser light source and the local oscillator, the maximum values. The method can be implemented using a device containing a mounted on a rotating platform photodetector with forming optics, fixed at an angle of 45° to the optical axis of the translucent plate, the lo and signal processing (see, for example, galiardi P.M., Carp W. Optical communication. - M.: Communication, 1978, str).

The main disadvantage of this method is the low rate of change of the spatial position of the laser receiving channel, resulting in increased search time.

The technical result, which is aimed by the invention, is to reduce the time of the review space and a significant increase of the accuracy of measurement of the coordinates of the laser light source.

The technical result is achieved by the fact that in the known method single-station measurements of the angular coordinates of the laser light source based on the application of scanning optical systems and determining the angular coordinates of the source of laser radiation on the angular position of the scanning system at the time of achievement of the desired signal maximum scan field of view in a given sector review carried out due to changed the I position of the phase front of the lo signal, and the angular coordinate of the source of laser radiation is determined by the angular position of the phase front of the lo signal at the time of achievement of the desired signal maximum value.

The disadvantage of this device that implements this method is the use of it slow and energy-intensive blocks mechanical precision of the positions of the laser receiving channel, resulting in increased weight and size, and complexity of service.

The technical result is achieved in that in a device containing a mounted on a rotating platform photodetector with forming optics, fixed at an angle of 45° to the optical axis of the translucent plate, the lo and signal processing, inputs connected in series forming unit parameters of the phase front of the local oscillator and the control unit of the phase front of the local oscillator, and the second output block parameters forming the phase front of the local oscillator is connected to the second input of the processing unit of the signal, the second input of the control unit of the phase front of the local oscillator is connected to the output of the local oscillator, and the output to the second input of the photodetector.

1 schematically shows the mutual position of the phase front reference wave local oscillator and the phase front of the signal in the wave from the source of laser radiation, where k_Withis the wave vector of the signal wave, k_Gis the wave vector heterodyne wave, θ - the angle between the wave vectors of the signal and heterodyne wave, α - the angle of inclination of the plane of the average of the phase front of the signal wave to the axis X. the Reference wave of the local oscillator and the signal wave of the laser light source are received at the photodetector with linear sizes l_x, l_yon the x-axis and y, respectively, and generate a signal at its output.

The invention consists in that the optical axis of the laser receiving channel while viewing the field of view remains stationary. View of the specified sector review carried out by changing the position of the phase front of the local oscillator in space.

If the angular misalignment between the direction of arrival of the radiation and the optical axis of the receiving channel is large, then the variance of the phase fronts of the field of the local oscillator and the field received radiation will also be large. This leads to the fact that the receiver output optical radiation formed a very small signal. The moment of reaching the maximum signal value indicates that there is no mismatch between the phase fronts of the received radiation and the radiation of the local oscillator and is defined as the sampled angle values of the spatial position of the wave, etc) the RA heterodyne wave relative to the optical axis of the receiving channel, which detect the angular coordinates of the source of the received laser radiation.

In the General case, the signal and heterodyne wave can be represented in the form:

where,- unit complex polarization vectors of the fields of signal and local oscillator, respectively;

,actual amplitude;

ϕ_Withthat ϕ_G- phase signal and heterodyne waves;

ω_Withthat ω_G- frequency signal and heterodyne waves.

Then the expression for the total current at the output of the photodetector can be written in the form:

where i_G(t), i_With(t) - components of the photocurrent signal and lo.

Useful (signal) component of the photocurrent is represented as follows:

wherespectral sensitivity of the photodetector;

- conversion;

M - coefficient of internal amplification;

h=6,626·10^-34J/Hz is the Planck constant;

e=1,602·10^-19CL - the charge of the electron;

η - efficiency of the optical system;

ν - frequency radiation;

ε₀=8,854·10^-12F/m - system is Skye constant;

μ₀=1,257·10^-6GN/m is the magnetic constant;

ε - dielectric environment.

From the expression (3) implies that the amplitude changes of the photocurrent i_SG(t) depends essentially on the phase multiplier Δϕ(x,y,t), worksand coherence amplitudes of the signal and heterodyne wave. Now we introduce the coefficient of concordance χ(t)defined by the equation:

then the expression for the component of the photocurrent (3) will have the form:

where P_Cand P_Gthe radiation power signal and the local oscillator;

I_C, I_G- the radiation intensity signal and lo.

The coefficient is a complex value and the module it takes the value 0≤|χ|≤1. If |χ|=0 the oscillating part of the photocurrent is missing, and if |χ|=1 wave fully coordinated and the amplitude of the oscillating part of the photocurrent takes the maximum value.

To assess the impact phase of the negotiation process photomachine assume that the waves are fully coordinated amplitude and polarization, then for homogeneous waves are:

Let the average of the phase front is perpendicular to the z-axis, and the average front rings is through the waves at an angle to the axis z, as shown in figure 1.

Then you can write ϕ_G(x, y)=ϕ_Gthat ϕ_With(x, y)=k_Cxx+k_Cyy, where k_Cx, k_Cyprojection of the wave vector of the signal wave on the x-axis and y, respectively. From figure 1 it follows that k_Cx(t)=k_Csinθ(t)cosα(t), k_Cy(t)=k_Csinθ(t)sinα(t), where the dependence of the angles θ and α from time characterizes the phase adjustment wave lo.

The coefficient of agreement with assumptions, the result will be:

As component of the photocurrent:

Figure 2 presents the dependence of i_SGin the case of l_x=l_y=l, k_cx=k_cy=k.

From dependence can be seen that with increasing argumentfunctionquickly fades that can very accurately determine the time of coincidence of the wave fronts (the direction to the source of laser radiation).

The signal can be represented in the form of intensity samples:

where e=1,602·10^-19CL - the charge of the electron.

Put l_x=l_y=l, k_Cx(t)=k_Cy(t)=ksinθ(t) and type designation

Then the expression (9) can be written in the de:

where

The maximum likelihood estimate is the value ofthat delivers the maximum of the logarithm of the functionality of the likelihood, then this value must satisfy the equation of the type:

where ξ(Z) - signal at the output of the photodetector.

The function sin x can be decomposed into an infinite product, namely:

Hence, the equality (10) can be written in the form:

then

Take into account thatwherethen

and (11) we write in the form:

Thus Z must satisfy the condition Z≠πk, k=1, 2,....

To calculate the integral in the expression (16) we replace the integrand function of the formits linear approximation, as shown in figure 3.

Receiving equations direct data:,

i.e. y₂=y₁+2A

where,

the equality (16) we write in the form:

Given symmetrically is th can write:

Then get:

Where

Asthen the expression for estimating angle θ will be

Thus, the essence of a reasonable algorithm to estimate the direction to the source of optical radiation consists of determining the angular position of the phase front of the wave of the local oscillator, in which the magnitude of the output signal takes its maximum value. The procedure of determining the angular position of the phase front of the local oscillator is to generate weighted values ofparameter Z as a product of the current value of the parameter Z on the magnitude of the signal from the output of the receiver of optical radiation ξ(Z), which is a function of this parameter, and then the energy averaging of the work on the interval [0, Z] we obtain the expression (20). The specific value of the angleis defined as arcsin.

Block diagram of the processing unit of the signal at the output of the photodetector (2) in accordance with expression (21) will have the form shown in figure 4.

Signal ξ(Z) from the output of the photodetector is fed through a tube directly to the appropriate multi-the Torah, carrying out the integration according to the expression (21). To the second input of the multiplier receives the AC signal Z varying from 0 to Z₀after amplifier with gain equal to. The signals from the outputs of both integrators after division one another by the formula (21) is fed to the input element that computes the function arcsin. The output of this element, get the value of. Considering the fact that the wave vector field of the local oscillator coincides with the optical axis of the receiver, thenthere is nothing like the estimation of the angular position of the phase front of the wave of the local oscillator, wherein the output signal of the photodetector takes its maximum value.

If θ(t) changes from -θ_mto θ_mthen. If the scale counts, which is associated with the measurement of the angular position of the phase front of the field lo lock so that at t=0, Z=0 and at t=t_K(where t_K- the period of change of angular position of the phase front of the local oscillator (lo) Z=Z₀moreover , the maximum value of the signal will be enclosed in the interval [0, Z₀] or on the time axis [0, t_K]equivalent timewhich takes the maximum value of the output signal p is of jemnice optical radiation.

Figure 5 shows the structural diagram of the one-item measuring coordinates of a laser light source that implements the proposed method. The device is installed on a rotating platform of a sensor (1) forming optics and fixed at an angle of 45° to the optical axis of the translucent plate, the block processing of the output signal of the photodetector (2), lo (5)and connected in series forming unit parameters of the phase front of the signal of the local oscillator (3) and controls the phase front of the signal of the local oscillator (4), and the second output block parameters forming the phase front of the signal of the local oscillator (3) is connected with the second input of the signal processing (2), the second input of the control unit of the phase front of the signal lo (4) is connected to the output of the local oscillator (5)and the output to the second input of the photodetector (1).

On the photodetector (1) do two waves: a signal from a source of laser radiation and the reference wave from the local oscillator. The phase of the reference wave front generated by the control unit of the phase front of the signal of the local oscillator (4) taking into account the required parameters defined by the forming unit parameters of the phase front of the signal of the local oscillator (3). Sector view is set by Electromechanical means using a rotating platform, and scans inside the sector is carried out by changing the position of the phase front of the signal of the local oscillator unit (4).

The moment of reaching the maximum signal value is determined by the processing unit of the signal at the output of the photodetector (2) as the sampled angle values of the spatial position of the wave vector of the heterodyne wave relative to the optical axis of the receiving channel, which determine the angular coordinates of the source of the received laser radiation.

In the proposed device the accuracy of estimation of the direction to the source of optical radiation is determined by the uniformity of the phase fronts or absence of such phase fluctuations of the received radiation, which is impossible to reproduce the phase front of the signal lo.

The claimed invention meets the requirement of "novelty" under the current law, as the analysis of the prior art and the identification of sources containing information about the equivalents of the claimed invention, has allowed to establish that the applicant is not detected similar, characterized by signs, identical to all the essential features of the claimed invention, and the definition from the list of identified unique prototype, as the most similar set of features analogue, has identified a set of essential towards perceived by the applicant to the technical result of the distinctive features in the claimed object.

To ensure the key compliance of the claimed invention to the requirement of inventive step, the applicant conducted an additional search of the known solutions the results indicate that the claimed invention is not necessary for the expert in the obvious way from the prior art because the prior art has identified effects provided the essential features of the claimed invention transformations to achieve a technical result.

Therefore, the claimed invention meets the requirement of "inventive step" by applicable law.

Give examples that prove the possibility of practical realization of the proposed method. As the control unit of the phase front of the signal lo can be used in electro-optic modulators with low values of deviation in the large scale changes in the magnitude of control voltage (see, for example, Optical journal, volume 66, No. 7, 1999, p.3), or opto-mechanical deflectors on the laser output of the local oscillator (see, for example, Rebrin J.K. Control optical beam in space. - M.: Owls. radio, 1977, str). As the processing unit of the phase front of the local oscillator can be used sawtooth generator that generates the control voltage from 0 towith a period of t_Kcorresponding to the period of change of angular position of the phase front lo.

The inventive method and device provide with the reduction time of the review space and a significant increase in the accuracy of measurement of the coordinates of the source of laser radiation. So, studies show that measurement error in the angular coordinates of the source of laser radiation at a wavelength of λ=1.06 µm is not more than 10^-4glad, and the review space is reduced by three times in comparison with known methods.

1. The way constitutive dimension of the coordinates of the laser light source based on the application of scanning optical systems and determining the angular coordinates of the source of laser radiation on the angular position of the scanning system at the time achieve a useful signal formed in the beating oscillations of the laser light source and lo, a maximum value, wherein the scan field of view in a given sector review carried out by changing the position of the phase front of the lo signal, and the angular coordinate of the source of laser radiation is determined by the angular position of the phase front of the lo signal in time achieve a useful signal of the maximum value.

2. The device constitutive dimension of the coordinates of the source of laser radiation, containing mounted on a rotating platform photodetector with forming optics, fixed at an angle of 45° to the optical axis of the translucent plate, the lo processing unit of the signal in the course of the photodetector, characterized in that additionally connected in series forming unit parameters of the phase front of the local oscillator and the control unit of the phase front of the local oscillator, and the second output block parameters forming the phase front of the local oscillator is connected to the second input of the processing unit of the signal, the second input of the control unit of the phase front of the local oscillator is connected to the output of the local oscillator, and the output to the second input of the photodetector.