CN101846528A - Detection method for capture capability of photoelectric tracking equipment to target with low contrast - Google Patents

Abstract

The invention relates to a detection method for the capture capability of photoelectric tracking equipment to a target with low contrast. The method comprises the following steps of: mounting a target on a focal plane of a collimation objective between a target integrating sphere and a background integrating sphere; adjusting the light flux of an external light source entering the background integrating sphere until a radiance value measured by a spectrum radiance meter reaches set background brightness; adjusting the light flux of the external light source entering the target integrating sphere until a radiance value measured by a spectrum radiance meter reaches set target brightness; and aligning an optical system of the photoelectric tracking equipment to be detected with the collimation objective and continuously changing target and background contrast until a target with the minimum contrast can be captured by the photoelectric tracking equipment. By the invention, the radiance of the target integrating sphere can be continuously changed to obtain different kinds of target and background contrast. The invention provides an optical measurable accurate reference for detecting the capture capability of the photoelectric tracking equipment to a target with low contrast.

Description

Test method of photoelectric tracking equipment's ability to capture low-contrast targets

technical field

The invention relates to a detection method of an optical instrument, in particular to a detection method of the ability of a photoelectric tracking measurement device to capture a low-contrast target.

Background technique

Photoelectric tracking and measuring equipment is used to realize automatic tracking and position measurement of a certain moving target (such as a target flying in the sky and a target traveling on the ground). The instrument performance such as the tracking distance and the stability of the tracking process that the photoelectric tracking measurement equipment can achieve is related to the contrast of the tracked target. When the target contrast is very low, the photoelectric tracking measurement equipment will not be able to detect the existence of the target, or can detect the target However, the ability to capture is reduced, which affects the stability of tracking. Therefore, the ability of photoelectric tracking measurement equipment to capture and recognize low-contrast targets is an important indicator of the overall equipment (hereinafter referred to as the target contrast index), which directly affects the tracking performance and tracking distance of photoelectric tracking measurement equipment. Generally, the target contrast index of the TV system for photoelectric tracking and measuring equipment is required to be better than 3%.

The purpose of researching and testing the target contrast index is to investigate the ability of the TV system to detect and capture weak target signals. The factors that affect the target contrast include the imaging quality of the optical lens, the transmittance, the stray light coefficient, the signal-to-noise ratio of the system, and the image processing algorithm. The verification method currently used in the laboratory is to use an analog electrical signal with a known signal-to-noise ratio to directly test whether the image processor can capture the signal. This verification does not include the contrast ratio of the optical system, TV sensor and circuit noise signal to the target. The impact of the TV system cannot truly reflect the overall performance of the TV system. In addition, this method cannot test the TV system of digital signals.

There are reports in the literature that a portable adjustable contrast target source is used to test the minimum resolvable contrast of an optical lens. It uses two overlapping integrating spheres. The test target (the target is a spatial frequency plate) is placed between the two integrating spheres, and an illumination source passes through it. The way of light splitting is two integrating spheres, and the brightness and target contrast of the two integrating spheres can be changed by adjusting the voltage of the power supply and the attenuation film.

This device is used to test the minimum resolvable contrast of a small visual optical lens. The illumination brightness of the two integrating spheres is very low, and the maximum brightness can only reach 200cd/m ² . When testing photoelectric equipment, it is necessary to simulate the maximum brightness of the sky (about 8000cd/m ² ), so the principle of this device cannot meet our needs.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for checking the ability of the photoelectric tracking device to capture the low-contrast target, which can continuously adjust the radiance of the background and the target, so as to accurately detect the capturing ability of the photoelectric tracking device.

In order to solve the above-mentioned technical problems, the photoelectric tracking device of the present invention comprises the following steps to the inspection method of low-contrast target capture ability:

Install the target between the target integrating sphere and the background integrating sphere, and make it on the focal plane of the collimating objective lens;

Turn on the built-in light source and external light source on the background integrating sphere;

Adjust the diaphragm on the background integrating sphere to control the luminous flux of the external light source entering the background integrating sphere, so that the radiance value of the background integrating sphere changes continuously until the radiance value measured by the spectroradiometer reaches the set background luminance N ₀ ;

Turn on the external light source on the target integrating sphere to illuminate the target;

Adjust the diaphragm on the target integrating sphere to control the luminous flux entering the target integrating sphere, so that the radiance value changes continuously until the radiance value measured by the spectral radiance meter reaches the set target brightness N ₁ ;

Calculate the contrast C of the target and the background:

$\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="N"\; filenames="HSA00000078273900011.png"\; state="\{\{state\}\}">N</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}$

Align the optical system of the photoelectric tracking device under inspection with the collimating objective lens, image the target, check the capture state of the target with known contrast by the photoelectric tracking device, repeatedly adjust the aperture of the diaphragm on the target integrating sphere, and continuously change the distance between the target and the target. The contrast of the background until the photoelectric tracking device can capture the target with the minimum contrast; at this time, the contrast value between the target and the background is the actual test value of the photoelectric tracking device's ability to capture and recognize low-contrast targets.

The invention controls the luminous flux of an external light source entering the background integrating sphere by adjusting the aperture of the diaphragm, continuously changes the radiance of the background integrating sphere, and can simulate the brightness of the sky background at any time, and controls the external light flux by adjusting the aperture of the diaphragm. Set the luminous flux of the light source into the target integrating sphere, and continuously change the radiance of the target integrating sphere, so as to obtain different contrasts between the target and the background, realize the continuous change of the contrast, and provide optical evidence for testing the ability of photoelectric tracking equipment to capture low-contrast targets. Accurate benchmarks for metrics.

The built-in light source and the external light source on the background integrating sphere, and the external light source on the target integrating sphere are all powered by a precisely controlled power supply to ensure the stability of the spectral radiance of the two integrating spheres.

The external light source adopts a halogen lamp, and the halogen lamp is located at the focus of the parabolic mirror.

Since halogen lamps are double-sided cosine radiators, the light beam on the side of the filament facing the integrating sphere is directly incident into the integrating sphere without being concentrated by the parabolic mirror, and the scattered light entering the integrating sphere can be controlled by controlling the distance between the parabolic mirror and the integrating sphere The cone angle, so that the light cannot be directly incident on the receiver.

Description of drawings

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 is a schematic diagram of the device structure for implementing the inspection method of the photoelectric tracking device of the present invention for the ability to capture a low-contrast target.

Detailed ways

As shown in FIG. 1 , the device for realizing the method for testing the ability of the photoelectric tracking device to capture a low-contrast target includes a background integrating sphere 1 , a target integrating sphere 2 , a target 3 and a collimating objective lens 4 . The target 3 and the collimating objective lens 4 are fixedly mounted on the background integrating sphere 1; the background integrating sphere 1 is also equipped with a spectral radiance meter 14, 10 built-in light sources 15, 4 external light sources 11 and 4 apertures 12. A spectral radiance meter 24 , an external light source 21 and an aperture 22 are installed on the target integrating sphere 2 . The target 3 is between the target integrating sphere and the background integrating sphere, and is located on the focal plane of the collimating objective lens 4 .

Both the built-in light source 15 and the external light sources 11 and 21 are powered by a precisely controlled power supply.

The external light sources 11 and 21 are halogen lamps, the external light source 11 is located at the focus of the parabolic mirror 13 corresponding to its position, and the external light source 21 is located at the focus of the parabolic mirror 23 corresponding to its position.

The background integrating sphere uses ten built-in light sources and four external light sources. During use, the stability of the current and voltage of all light sources is maintained. Turn on the built-in light source 15 and the external light source 11 on the background integrating sphere 1, and the external light source 11 emits The light enters the background integrating sphere 1 through the aperture 12; adjust the aperture to control the luminous flux of the external light source. When the luminous flux adjustment amount is equivalent to the luminous flux of a built-in light source, turn off a built-in light source, and then re-adjust the aperture of the aperture to make the background The radiance of the integrating sphere can change continuously without any step until the radiance value measured by the spectral radiometer reaches the set background brightness N ₀ , so that the background integrating sphere can simulate the brightness of the sky background at any time.

Turn on the external light source on the target integrating sphere to illuminate the target;

Adjust the diaphragm on the target integrating sphere to control the luminous flux entering the target integrating sphere, so that the radiance value changes continuously until the radiance value measured by the spectral radiance meter reaches the set target brightness N ₁ ;

Calculate the contrast C of the target and the background:

$\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="N"\; filenames="HSA00000078273900011.png"\; state="\{\{state\}\}">N</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}$

Align the optical system of the photoelectric tracking device under inspection with the collimating objective lens, image the target, check the capture state of the target with known contrast by the photoelectric tracking device, repeatedly adjust the aperture of the diaphragm on the target integrating sphere, and continuously change the distance between the target and the target. The contrast of the background until the photoelectric tracking device can capture the target with the minimum contrast; at this time, the contrast value between the target and the background is the actual test value of the photoelectric tracking device's ability to capture and recognize low-contrast targets.

The brightness change of the background should meet the change range from early morning to dusk during the day, and the maximum brightness should reach the brightness of the sky when the sun’s altitude angle is 70° on the day of the summer solstice. The change range of target contrast should mainly meet the requirements of low-contrast testing. 0-20% target contrast is the most commonly used range. The change range of target brightness and the maximum brightness that can be achieved are close to the background. The target should be an infinite target, which can meet The test of the optical system within the clear aperture of 250mm.

There are two ways to illuminate the background integrating sphere: the built-in light source and the external light source.

The target integrating sphere is illuminated by an external light source.

In the way of using external light source lighting, it is necessary to consider how to use the luminous flux of the light source. By placing the external light source on the focal point of the parabolic mirror, the divergent light beam emitted by the light source becomes a parallel light beam and irradiates the inner wall of the integrating sphere, and the luminous flux entering the integrating sphere is controlled by adjusting the aperture of the diaphragm, so that the luminous flux of the lighting source can be obtained Fully utilized, at the same time heat dissipation of the light source and adjustment of the radiance of the integrating sphere are easy to realize. However, compared with the built-in light source, the manufacturing cost of this external light source is high. To achieve the same spectral radiance of the integrating sphere, it is necessary to increase the number of illumination light sources and also increase the number of control power sources. The background integrating sphere uses ten built-in light sources and four external light sources to maintain the stability of the current and voltage of all light sources during use, and adjust the diaphragm to control the luminous flux of the external light source. When the luminous flux adjustment is equivalent to the luminous flux of a built-in light source , turn off a built-in light source, and then re-adjust the aperture of the diaphragm, so that the radiance of the integrating sphere can change continuously without steps, so as to obtain the target of any contrast.

For the integrating sphere, we need no direct light in the detector plane and the imaging field of view, because according to the principle of the integrating sphere, only the brightness of the diffuse reflection light in the integrating sphere is uniform, and only the entire Only the brightness measured when the light is diffusely reflected can represent the brightness in the imaging field of view. Any direct light incident on any side will cause a large deviation between the measured result and the actual value, thereby bringing errors to the contrast measurement. For external light sources, since halogen lamps are double-sided cosine radiators, the light beam on the side of the filament facing the integrating sphere is directly incident into the integrating sphere without being concentrated by the parabolic mirror. This part of the light should be minimized as much as possible. By controlling the parabolic mirror The distance from the integrating sphere controls the cone angle of the scattered light entering the integrating sphere so that the light does not strike the receiver directly.

To ensure the stability of the spectral radiance of the two integrating spheres, it is first required to use a stable light source. We choose a halogen lamp as the lighting source, and use a precision 0.3‰ constant current and voltage stabilized power supply to power the lighting source. Experiments have proved this measure It can ensure the stability of the spectral radiance of the two integrating spheres to reach 1‰; secondly, to ensure the consistency and repeatability of the measurement results of the two spectral radiance meters, the stability accuracy of the selected spectral amplitude luminance meter is better than 5‰, which can Meet the measurement requirements of 1% stable accuracy of contrast.

The present invention is not limited to the above embodiments, the number of external light sources on the target integrating sphere, built-in light sources and external light sources on the background integrating sphere can be selected according to the requirements of light source power and spectral radiance required by the integrating sphere.

Claims (3)

1. A photoelectric tracking device is characterized in that comprising the following steps to the inspection method of low-contrast target acquisition ability: Install the target between the target integrating sphere and the background integrating sphere, and make it on the focal plane of the collimating objective lens; Turn on the built-in light source and external light source on the background integrating sphere; Adjust the diaphragm on the background integrating sphere to control the luminous flux of the external light source entering the background integrating sphere, so that the radiance value of the background integrating sphere changes continuously until the radiance value measured by the spectroradiometer reaches the set background luminance N ₀ ; Turn on the external light source on the target integrating sphere to illuminate the target; Adjust the diaphragm on the target integrating sphere to control the luminous flux entering the target integrating sphere, so that the radiance value changes continuously until the radiance value measured by the spectral radiance meter reaches the set target brightness N ₁ ; Calculate the contrast C of the target and the background: $\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}$ Align the optical system of the photoelectric tracking device under inspection with the collimating objective lens, image the target, check the capture state of the target with known contrast by the photoelectric tracking device, repeatedly adjust the aperture of the diaphragm on the target integrating sphere, and continuously change the distance between the target and the target. The contrast of the background until the photoelectric tracking device can capture the target with the minimum contrast; at this time, the contrast value between the target and the background is the actual test value of the photoelectric tracking device's ability to capture and recognize low-contrast targets. 2. The photoelectric tracking device according to claim 1 is characterized in that the built-in light source and the external light source on the background integrating sphere and the external light source on the target integrating sphere all adopt precision Control power supply. 3. The method for testing the ability of the photoelectric tracking device to capture low-contrast targets according to claim 2, wherein the external light source is a halogen lamp, and the halogen lamp is located at the focus of the parabolic mirror.

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