CN106918845A - Long-distance laser semi-active azimuth measurement device based on polarization detection - Google Patents

Abstract

A long-distance laser semi-active azimuth measuring device based on polarization detection relates to the technical field of long-distance target azimuth detection. The invention aims to solve the problem that when the existing laser azimuth measuring device is used for detecting the azimuth of a long-distance target, an input signal is submerged by system noise to influence the detection capability of the laser azimuth measuring device. According to the long-distance laser semi-active azimuth measuring device based on polarization detection, a first 1/4 wave plate, a second 1/4 wave plate and a four-quadrant polarizing plate are sequentially arranged in front of an optical lens group of a traditional laser semi-active azimuth measuring device, the four-quadrant polarizing plate is adjacent to the optical lens group, and the second 1/4 wave plate only covers the first quadrant of the four-quadrant polarizing plate and the first quadrant of an APD detector. The invention is suitable for detecting the direction of a long-distance target.

Description

Long-distance laser semi-active azimuth measurement device based on polarization detection

technical field

The invention belongs to the technical field of long-distance target orientation detection.

Background technique

The current laser semi-active azimuth measurement device adopts the direct detection mode, that is, the system input is the energy of the scattered laser echo of the target, and the output is the deviation angle value of the target. When the laser azimuth measuring device detects the azimuth of a long-distance target, the scattered laser echo signal of the target is extremely weak and will be submerged by the system noise. At this time, the system noise, especially the sunlight background radiation noise, seriously affects the detection capability of the laser azimuth measuring device.

Contents of the invention

The present invention is to solve the problem that the input signal will be submerged by system noise and affect the detection capability of the laser azimuth measuring device when the existing laser azimuth measuring device detects the long-distance target azimuth, and now provides a long-distance laser semi-active based on polarization detection Azimuth measuring device.

A long-distance laser semi-active orientation measurement device based on polarization detection, including a traditional laser semi-active orientation measurement device, which includes an optical lens group 4, an APD detector 5 (avalanche photodetector) and a servo system ;

The first 1/4 wave plate 1, the second 1/4 wave plate 2 and the four-quadrant polarizer 3 are arranged in sequence before the optical lens group 4, and the four-quadrant polarizer 3 is adjacent to the optical lens group 4,

The second 1/4 wave plate 2 only covers the first quadrant of the four-quadrant polarizer 3 and the first quadrant of the APD detector 5 .

The polarization directions of the four quadrants of the four-quadrant polarizer 3 are independent of each other.

Let the polarization direction of the signal light be α, the polarization direction of the background radiation light be β, the distance between the remote laser semi-active azimuth measuring device and the detection target be R, and the polarization directions of the four-quadrant polarizer 3 be θ ₁ , θ ₂ , θ ₃ and θ ₄ ,

Then the signal light intensity I _s-APD received on the photosensitive surface of the APD detector 5 and the background radiation light intensity I _b-APD are respectively:

Among them, I _s is the signal light intensity incident on the No. 1 1/4 wave plate 1, I _b is the background radiation light intensity incident on the No. 1 1/4 wave plate 1, n=1,2,3,4 .

The intensity I _b of the background radiation incident to the No. 1 1/4 wave plate 1 is:

I _b =I _p +Io

Among them, I _p is the light intensity of the polarized part of the background radiation light, and I _o is the light intensity of the non-polarized part of the background radiation light.

The long-distance laser semi-active azimuth measuring device based on polarization detection described in the present invention has a simple structure by adding a 1/4 wave plate and a four-quadrant polarizer to the traditional laser azimuth measuring device, and can also increase the working distance of the azimuth measuring device , effectively suppress the background radiation noise, especially the sunlight background radiation noise, significantly improve the signal-to-noise ratio of the system, and improve the long-distance detection capability of the laser azimuth measuring device. The invention is suitable for long-distance target azimuth detection.

Description of drawings

FIG. 1 is a schematic structural diagram of a long-distance laser semi-active azimuth measurement device based on polarization detection according to the present invention.

detailed description

Since the polarization direction of the background radiation light in different places is different, before the target detection, the polarization direction of the background radiation light can be determined in advance, and then the signal light with the appropriate polarization direction can be selected for target detection, which can effectively suppress the background radiation light and improve System signal-to-noise ratio and long-range target detection capability. Based on the above principles, the present invention is described in detail using the following embodiments.

Specific Embodiment 1: This embodiment is described in detail with reference to FIG. 1. The long-distance laser semi-active azimuth measurement device based on polarization detection described in this embodiment includes a traditional laser semi-active azimuth measurement device. The traditional laser semi-active azimuth measurement The device comprises an optical lens group 4, an APD detector 5 (avalanche photodetector) and a servo system;

Before the optical lens group 4 of the traditional laser semi-active azimuth measuring device, the first 1/4 wave plate 1, the second 1/4 wave plate 2 and the four-quadrant polarizer 3 are sequentially arranged, and the four-quadrant polarizer 3 and the optical lens group 4 adjacent,

The second 1/4 wave plate 2 only covers the first quadrant of the four-quadrant polarizer 3 and the first quadrant of the APD detector 5 .

In this embodiment, the first 1/4 wave plate 1 is used to change the polarization characteristics of the incident light; the second 1/4 wave plate 2 is used to eliminate the singularity of the system measurement matrix; the four-quadrant polarizer 3 is used to reduce the background The light intensity of the radiated light; the second 1/4 wave plate 2 and the four-quadrant polarizer 3 together form the polarization detection structure of the laser orientation measurement device; the optical lens group 4 is used to converge the incident light onto the ADP photosensitive surface; the APD detector 5 is used to convert the incident light energy into four electrical signals.

In practical application, the signal light and the background radiation are transmitted to the photosensitive surface of the APD detector 5 through the first 1/4 wave plate 1, the second 1/4 wave plate 2, the four-quadrant polarizer 3 and the optical lens group 4 Above, the APD detector 5 sends electrical signals to the servo system. The long-distance laser semi-active azimuth measurement device based on polarization detection described in this embodiment has a simple structure, and only needs to add wave plates and polarizers to the traditional laser azimuth measurement device, which can effectively improve the system signal-to-noise ratio and increase the azimuth measurement. The operating distance of the device.

Specific embodiment 2: This embodiment is a further description of the long-distance laser semi-active orientation measurement device based on polarization detection described in specific embodiment 1. In this embodiment, the polarization directions of the four quadrants of the four-quadrant polarizer 3 Independent.

Specific embodiment three: This embodiment is a further description of the long-distance laser semi-active azimuth measurement device based on polarization detection described in specific embodiment one. In this embodiment,

Let the polarization direction of the signal light be α, the polarization direction of the background radiation light be β, the distance between the remote laser semi-active azimuth measuring device and the detection target be R, and the polarization directions of the four-quadrant polarizer 3 be θ ₁ , θ ₂ , θ ₃ and θ ₄ ,

Then the signal light intensity I _s-APD received on the photosensitive surface of the APD detector 5 and the background radiation light intensity I _b-APD are respectively:

Among them, I _s is the signal light intensity incident on the No. 1 1/4 wave plate 1, I _b is the background radiation light intensity incident on the No. 1 1/4 wave plate 1, n=1,2,3,4 .

According to the system structure of the long-distance laser semi-active azimuth measuring device system (namely: the first 1/4 wave plate 1, the second 1/4 wave plate 2, the four-quadrant polarizer 3, the optical lens group 4 and the APD detector 5) ) The minimum value of the condition number of the measurement matrix determines the polarization direction of the four-quadrant polarizer 3 (ie: the values of θ ₁ , θ ₂ , θ ₃ and θ ₄ ), and then according to the background radiation incident to the long-distance laser semi-active orientation measuring device The polarization direction of the light β ^* , select the signal light with a suitable polarization direction α ^* , that can be obtained:

I _b-APD <I _b (1)

The formula (1) shows that the background light is suppressed, and the formula (2) shows that the signal-to-noise ratio of the long-distance laser semi-active azimuth measurement device is improved, that is, the background radiation received by the laser azimuth measurement device is effectively suppressed, and the azimuth measurement is improved. The signal-to-noise ratio of the device improves the target detection capability of the laser azimuth measuring device.

Embodiment 4: This embodiment is a further description of the long-distance laser semi-active azimuth measurement device based on polarization detection described in Embodiment 3. The background radiation light intensity I _b is:

I _b =I _p +I _o

Among them, I _p is the light intensity of the polarized part of the background radiation light, and I _o is the light intensity of the non-polarized part of the background radiation light.

The background radiant light is partially polarized light, and the light intensity of the background radiant light can be expressed as the sum of the polarized light intensity and the non-polarized light intensity (ie the remaining light intensity), and the polarized light intensity is half of the total background light intensity.

Claims (4)

1. A long-distance laser semi-active orientation measurement device based on polarization detection, including a traditional laser semi-active orientation measurement device, which includes an optical lens group (4), an APD detector (5) and a servo system , characterized in that, Before the optical lens group (4), there are sequentially provided with No. 1 1/4 wave plate (1), No. 1/4 wave plate (2) and four-quadrant polarizer (3), and the four-quadrant polarizer (3) and optical lens groups (4) adjacent, The second 1/4 wave plate (2) only covers the first quadrant of the four-quadrant polarizer (3) and the first quadrant of the APD detector (5). 2. The remote laser semi-active azimuth measuring device based on polarization detection according to claim 1, characterized in that the polarization directions of the four quadrants of the four-quadrant polarizer (3) are independent of each other. 3. The remote laser semi-active azimuth measuring device based on polarization detection according to claim 1, characterized in that, Let the signal light polarization direction be α, the background radiation light polarization direction be β, and the polarization directions of the four-quadrant polarizer (3) be θ ₁ , θ ₂ , θ ₃ and θ ₄ respectively, Then the signal light intensity I _s-APD received on the photosensitive surface of the APD detector (5) and the background radiation light intensity I _b-APD are respectively: ${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; P</span>}\mathrm{<span\; class="notranslate">\; D.</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 4</span>}}{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; cos</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; )</span>$ ${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; P</span>}\mathrm{<span\; class="notranslate">\; D.</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; \&lsqb;</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 8</span>}}\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 4</span>}}{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; cos</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&rsqb;</span>$ Among them, I _s is the signal light intensity incident to No. 1 1/4 wave plate (1), I _b is the background radiation light intensity incident to No. 1 1/4 wave plate (1), n=1,2 ,3,4. 4. The remote laser semi-active azimuth measuring device based on polarization detection according to claim 3, characterized in that, The background radiation light intensity I _b incident to No. 1 1/4 wave plate (1) is: I _b =I _p +I _o Among them, I _p is the light intensity of the polarized part of the background radiation light, and I _o is the light intensity of the non-polarized part of the background radiation light.