CN115144158A - Device and method for testing optical feedback characteristic of image tube of low-light-level image intensifier - Google Patents
Device and method for testing optical feedback characteristic of image tube of low-light-level image intensifier Download PDFInfo
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- CN115144158A CN115144158A CN202210644131.8A CN202210644131A CN115144158A CN 115144158 A CN115144158 A CN 115144158A CN 202210644131 A CN202210644131 A CN 202210644131A CN 115144158 A CN115144158 A CN 115144158A
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Abstract
The invention discloses a device and a method for testing the light feedback characteristic of a low-light-level image intensifier image tube. The method comprises the steps that the MCP voltage with optical feedback of an image tube is obtained according to the change condition of the image tube contrast along with the MCP voltage by testing the modulation degree of a certain fixed spatial frequency line under the MCP voltage corresponding to the image tube, if the brightness gain corresponding to the voltage is higher than the required brightness gain, the image tube has no risk of optical feedback, and otherwise, the image tube has the risk of optical feedback; therefore, whether the risk of optical feedback exists after the image tube and the high-voltage power supply are packaged into the image intensifier or not is judged. The invention realizes the accurate test of the light feedback characteristic of the low-light level image tube, can avoid the downward circulation of the image tube with the light feedback, and ensures the imaging quality of the low-light level image intensifier.
Description
Technical Field
The invention belongs to the technical field of low-light-level image intensifiers, and discloses a device and a method for testing the optical feedback characteristic of a low-light-level image intensifier image tube.
Background
The low-light-level image intensifier is the core of the low-light-level night vision device, and the performance of the low-light-level image intensifier determines the quality of the low-light-level night vision device. In the process of manufacturing the image intensifier, the glimmer image tube and the special high-voltage power supply are manufactured and tested respectively, the qualified glimmer image tube and the special high-voltage power supply are integrated and packaged together, and are bonded, sealed and fixed in a plastic shell by utilizing silicon rubber to form the complete image intensifier. After the image intensifier is integrated and packaged, the brightness gain of the image intensifier can meet the technical index requirement by adjusting the MCP working voltage of the special high-voltage power supply.
The structure of a conventional proximity micro image tube (hereinafter referred to as an image tube) is schematically shown in fig. 2, and the main components of the image tube for realizing image enhancement include a cathode input window 81, a photocathode 82, a microchannel plate 83 (hereinafter referred to as an MCP), a phosphor screen aluminum film 84, a phosphor screen powder layer 85, and an optical fiber output window 86. When the weak light image is incident on the image intensifier, the weak light image reaches the photocathode 82 through the cathode input window 81 and excites photoelectrons, the photoelectrons are multiplied by the microchannel plate 83, then bombard the phosphor screen powder layer 85 to emit light, and finally are output through the anode optical fiber output window 86, so that the weak light image is intensified.
The light feedback of the image tube means that electrons emitted by a photocathode of the image tube are multiplied by MCP and then pass through a fluorescent screen aluminum film to excite a fluorescent powder layer to emit light, the light emitted by the fluorescent powder layer passes through the fluorescent screen aluminum film and the MCP and then returns to the photocathode, so that non-imaging photoelectrons are emitted by the photocathode, the photoelectrons are multiplied by the MCP to further excite the fluorescent powder layer to emit light, the light emitted by the fluorescent powder returns to the cathode through the aluminum film and the MCP, the cycle is repeated, the output brightness is increased once, and finally, stable output brightness is formed, namely the light feedback of the image tube. The existence of the optical feedback phenomenon can cause the image contrast of the image tube to be reduced, so that the imaging quality of the image intensifier is seriously deteriorated, and therefore, the condition that the optical feedback occurs in the image intensifier is avoided in use.
The optical feedback of the image tube is mainly related to the brightness gain, the brightness gain of the image intensifier is mainly determined by the MCP electronic gain of the image tube, the MCP electronic gain of the image tube is determined by the MCP working voltage, the MCP voltage and the electronic gain of the image tube are in exponential multiple relation, a typical MCP voltage and electronic gain curve diagram is shown in fig. 3, the higher the MCP voltage is, the higher the electronic gain of the MCP is, the higher the brightness gain of the image tube is, and the more the image tube is easy to generate the optical feedback. Therefore, if a certain type of image intensifier requires higher brightness gain, the MCP working voltage of the image tube must be higher, and the risk of optical feedback is higher; however, there is no clear way to test whether an image intensifier tube has optical feedback at its corresponding brightness gain. If the brightness gain corresponding to the image tube can be tested before the image tube and the special high-voltage power supply are integrated and packaged, the image tube with the optical feedback can be prevented from flowing downwards.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a device and a method for testing the light feedback characteristic of a low-light-level image intensifier image tube.
The technical scheme for realizing the invention is as follows:
the device for testing the light feedback characteristic of the image tube of the low-light-level image intensifier comprises a light source, a neutral filter box, an adjustable aperture diaphragm, an integrating sphere, an illuminometer, a contrast testing target plate, a conjugate projection lens assembly, an image tube, an industrial camera, an image tube high-voltage power supply, a computer and a testing camera box. The light source, the neutral filter box, the adjustable aperture diaphragm, the integrating sphere, the contrast test target plate, the conjugate projection lens assembly, the image tube and the industrial camera are sequentially arranged along the light advancing direction in a coaxial mode; the contrast test target plate, the conjugate projection lens assembly, the image tube and the industrial camera are all arranged in the test camera bellows.
The light output from the integrating sphere is controlled to be 2-4 multiplied by 10 after being measured by the illuminometer -3 lx range. The contrast test target plate comprises 6 gray scale test values of 15lp/mm with the length of 2 mm.
The working principle of the device of the invention is as follows:
the light emitted by the light source enters the integrating sphere after being attenuated by the neutral filter box and the adjustable aperture diaphragm, uniform diffused light is output through the integrating sphere, after the light output from the integrating sphere irradiates the contrast test target plate, the image of the target plate is projected to the cathode surface of the image tube through the conjugate projection lens and finally output through the anode output window, and the image is collected by the industrial camera and the modulation degree of the image is calculated; the image tube is powered by the image tube high-voltage power supply, and the MCP voltage value of the image tube is adjusted by adjusting the MCP output voltage of the image tube high-voltage power supply; the illuminometer realizes real-time detection of the illuminance output by the integrating sphere and can adjust the illuminance output by the integrating sphere by adjusting the adjustable aperture diaphragm. The modulation degree test values of the image tube under different MCP voltages can be obtained by adjusting the MCP voltage value of the image tube high-voltage power supply, the MCP voltage when the image tube contrast decreases along with the increase of the MCP voltage is the optical feedback voltage of the image tube, and if the brightness gain of the image tube under the MCP voltage is higher than the gain requirement of the image intensifier, the image tube can meet the tube selection requirement; if the luminance gain of the picture tube at the MCP voltage is lower than the luminance gain value of the image intensifier, the picture tube cannot be used for the type of image intensifier.
A method of testing the optical feedback characteristics of a low-light image intensifier tube, comprising: by applying an input illuminance of 2 to 4 x 10 -3 Under lx condition, projecting a 15lp/mm resolution target plate to an image tube photocathode through a 1X conjugate optical lens, acquiring a target plate image output from an anode optical fiber output window after a target plate line is imaged by an image tube through a CCD camera, and finally calculating the modulation degree of the target plate line by adopting image analysis processing software, wherein the gray test value of the target plate line is calculated according to the following formula to obtain the corresponding modulation value T of the line;
in the formula: i is max Average of the maximum values of the gray values measured for the lines of the target plate, I min The average of the minimum gray value values is tested for the target plate lines.
The contrast of the image tube under different MCP working voltages can be obtained by adjusting the MCP working voltage, the contrast does not change along with the change of the MCP voltage in the normal working interval of the image tube, when the MCP of the image tube is adjusted to the voltage at which optical feedback occurs, the contrast is reduced, and the MCP voltage at the moment can be judged as the optical feedback voltage of the image tube.
The invention has the beneficial effects that:
the invention realizes the accurate test of the optical feedback characteristic of the glimmer photo tube, can accurately judge the MCP voltage when the glimmer photo tube has optical feedback through the test of the contrast of the corresponding resolution target plate under different MCP voltages, and uses the MCP voltage at the moment as the optical feedback voltage of the glimmer photo tube, thereby judging whether the glimmer photo tube can meet the requirement of the corresponding image intensifier. Firstly, the invention can accurately judge whether the corresponding brightness gain of the glimmer image tube has optical feedback before the glimmer image tube and the special high-voltage power supply are integrated and packaged, and can avoid the downward circulation of the image tube with the optical feedback. And secondly, the light feedback voltage of the glimmer image tube can be used as the tube selection basis of the image intensifier with different gain requirements, so that the glimmer image tube with light feedback is prevented from being selected, and the imaging quality of the glimmer image intensifier is ensured.
Drawings
FIG. 1: the schematic diagram of the optical feedback characteristic testing device of the image tube in the low-light level image intensifier is shown in fig. 1: 1-light source, 2-neutral filter box, 3-adjustable aperture diaphragm, 4-integrating sphere, 5-illuminometer, 6-contrast test target plate, 7-conjugate projection lens component, 8-image tube, 9-industrial camera, 10-image tube high-voltage power supply, 11-computer and 12-test camera box.
FIG. 2: the image tube is schematically composed, and in fig. 2: 81-cathode input window, 82-photocathode, 83-microchannel plate, 84-fluorescent screen aluminum film, 85-fluorescent screen powder layer and 86-optical fiber output window.
FIG. 3: typical MCP voltage and electron gain curve diagram
FIG. 4 is a schematic view of: schematic diagram of contrast test target plate.
FIG. 5: and the contrast target plate line gray scale test result is shown schematically.
Detailed Description
The device for testing the light feedback characteristic of the image tube in the image intensifier is shown in figure 1, light emitted by a light source 1 enters an integrating sphere 4 after being attenuated by a neutral filter box 2 and an adjustable aperture diaphragm 3, uniform diffused light is output through the integrating sphere, a target plate image is projected to the cathode surface of an image tube 8 through a conjugate projection lens 7 after the target plate image irradiates a contrast testing target plate 6 through the integrating sphere and is finally output through an anode output window, and the light is collected by an industrial camera 9 and the modulation degree of the light is calculated; the image tube 8 is supplied with power by the image tube high-voltage power supply 10, the modulation degree test values of the image tube under different MCP voltages can be obtained by adjusting the MCP voltage value of the image tube high-voltage power supply 10, the MCP voltage when the image tube contrast decreases along with the increase of the MCP voltage is the optical feedback voltage of the image tube, and if the brightness gain of the image tube under the MCP voltage is higher than the gain requirement of the image intensifier, the image tube can meet the tube selection requirement; if the luminance gain of the picture tube at the MCP voltage is lower than the luminance gain value of the image intensifier, the picture tube cannot be used for the type of image intensifier.
The method for testing the optical feedback characteristic of the low-light-level image intensifier tube comprises the following steps:
(1) The light emitted by the light source 1 enters the integrating sphere 4 after being attenuated by the neutral filter box 2 and the adjustable aperture diaphragm 3, and the adjustable aperture diaphragm 3 is adjusted to ensure that the illumination range measured by the illuminometer 5 for the uniform diffused light output by the integrating sphere is 2-4 multiplied by 10 -3 lx。
(2) The contrast test target plate 6 was 6 high contrast target plates of 15lp/mm in length of 2 mm.
(3) In order to measure the contrast of the image tube under different MCP voltages, the image tube high voltage power supply 10 supplies power to the image tube 8, and the brightness gain of the image tube can be adjusted by adjusting the MCP voltage value of the image tube high voltage power supply 10.
(4) The target plate 6 is focused on the input surface of the image tube 8 through the conjugate lens 7, and the target plate image output after the target plate 6 is projected to the image tube 8 through the conjugate lens 7 is in the best clear state by adjusting the focal length of the industrial camera 9.
(5) An image of an output target plate image of the image tube 8, which is acquired by the industrial camera 9, is subjected to image acquisition and analysis calculation through software of the computer 11, a test schematic diagram corresponding to the target plate image is shown in fig. 4, a gray level test value of a target plate line is shown in fig. 5, and a gray level value obtained through testing is calculated according to a modulation degree calculation formula (1) to obtain a corresponding modulation degree value T;
in the formula: i is max Average of 15% maximum values selected for the test gray values between 6 target plate lines with 15lp/mm resolution, I min The average of the 18% minimum values selected for the line test gray values of the 6 target panels.
(6) In order to measure the contrast of the photo tube 8 under different MCP voltages, the brightness gain of the photo tube 8 is adjusted by adjusting the MCP voltage value of the photo tube high-voltage power supply 10 to obtain the modulation values of the photo tube 8 under different voltages, the image contrast of the photo tube is kept unchanged in the normal operating range of the photo tube when the MCP voltage is adjusted from low to high, the image contrast of the photo tube is reduced when the MCP voltage is increased to the optical feedback voltage, and the optical feedback voltage of the photo tube can be determined by the MCP voltage at the time.
Claims (5)
1. The utility model provides a device for testing the light feedback characteristic of shimmer image intensifier picture tube which characterized in that:
the device comprises a light source (1), a neutral filter box (2), an adjustable aperture diaphragm (3), an integrating sphere (4), an illuminometer (5), a contrast test target plate (6), a conjugate projection lens assembly (7), an image tube (8), an industrial camera (9), an image tube high-voltage power supply (10), a computer (11) and a test camera box (12);
the light source (1), the neutral filter box (2), the adjustable aperture diaphragm (3), the integrating sphere (4), the contrast test target plate (6), the conjugate projection lens assembly (7), the image tube (8) and the industrial camera (9) are sequentially arranged along the light advancing direction in a coaxial mode;
the contrast test target plate (6), the conjugate projection lens assembly (7), the image tube (8) and the industrial camera (9) are all arranged in a test camera bellows (12);
the light emitted by the light source (1) enters the integrating sphere (4) after being attenuated by the neutral filter box (2) and the adjustable aperture diaphragm (3), and is diffused by the integrating sphere (4);
the light output from the integrating sphere (4) irradiates a contrast test target plate (6), and an image of the contrast test target plate (6) is projected to the cathode surface of an image tube (8) through a conjugate projection lens and is finally output through an anode output window;
the industrial camera (9) is used for collecting images of the target plate, and the computer (11) is connected with the industrial camera (9) and used for receiving the images of the target plate collected by the industrial camera (9) and calculating the modulation degree of the lines of the target plate.
2. The apparatus for testing optical feedback characteristics of a low-light level image intensifier tube as set forth in claim 1, wherein:
the image tube high-voltage power supply (10) adjusts the MCP voltage value of the image tube (8) by adjusting the MCP output voltage and obtains modulation degree test values of the image tube under different MCP voltages.
3. The apparatus for testing optical feedback characteristics of a low-light level image intensifier tube as set forth in claim 1 or 2, wherein:
the light output from the integrating sphere (4) is controlled to be 2-4 multiplied by 10 after being measured by the illuminometer (5) -3 lx range.
4. The apparatus for testing optical feedback characteristics of a low-light level image intensifier tube as set forth in claim 3, wherein:
the contrast test target plate (6) comprises 6 gray scale test values of 15lp/mm with the length of 2 mm.
5. A method for testing the optical feedback characteristics of a low-light level image intensifier tube, which comprises the following steps, according to any one of claims 1 to 4, and is characterized in that the device for testing the optical feedback characteristics of the low-light level image intensifier tube is adopted:
the method comprises the following steps that (1) light emitted by a light source (1) enters an integrating sphere (4) after being attenuated by a neutral filter box (2) and an adjustable aperture diaphragm (3), and the adjustable aperture diaphragm (3) is adjusted to enable the uniform diffused light to be output through the integrating sphere (4);
(2) Adjusting the brightness gain of the image tube (8) by adjusting the MCP voltage value of the image tube high-voltage power supply (10);
(3) Focusing the target plate on the input surface of the image tube (8) through the conjugate lens, and outputting a target plate image to be in a clear state after the target plate is projected to the image tube (8) through the conjugate lens by adjusting the focal length of the industrial camera (9);
(4) The image of the output target plate image of the image tube (8) is collected by an industrial camera (9), the image is collected and analyzed and calculated by software of a computer (11), and the gray value obtained by testing is calculated according to a modulation degree calculation formula (1) to obtain a corresponding modulation degree value T;
in the formula: i is max 6 target plate lines with resolution of 15lp/mmAverage of 15% maximum values of the test gray values between bars, I min The average value of 18% minimum values selected from the line test gray values of the 6 target plates;
(5) The contrast of the image tube (8) under different MCP voltages is measured, the brightness gain of the image tube (8) is adjusted by adjusting the MCP voltage value of the image tube high-voltage power supply (10) to obtain the modulation values of the image tube (8) under different voltages, the image contrast of the image tube (8) is kept unchanged when the MCP voltage is adjusted from low to high in the normal working range of the image tube, the image contrast of the image tube is reduced when the MCP voltage is increased to the optical feedback voltage of the image tube, and the optical feedback voltage of the image tube (8) can be judged by the MCP voltage at the moment.
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| CN202210644131.8A CN115144158A (en) | 2022-06-08 | 2022-06-08 | Device and method for testing optical feedback characteristic of image tube of low-light-level image intensifier |
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