Device and method for detecting imaging defects of micro-channel plate

Abstract

The invention relates to a device and a method for detecting imaging defects of a microchannel plate, and the device comprises an imaging detection unit which comprises a microchannel plate fixing clamp, a fluorescent screen, a control mechanism and a camera shooting mechanism; the emission source unit comprises an electron source and an emission source power supply which are connected with each other; two ends of the vacuum unit are respectively connected with the imaging detection unit and the emission source unit; the vacuum unit comprises a vacuum chamber and a vacuum pump set arranged outside the vacuum chamber. According to the invention, scratches and dust on the fluorescent screen can be effectively distinguished from defects on imaging of the micro-channel plate, the imaging defects of the micro-channel plate can be accurately judged, and the method can be used for imaging tests of all types of micro-channel plates.

Description

Technical Field

[0001] The invention belongs to the technical field of microchannel plates, and in particular relates to a device and method for detecting imaging defects of microchannel plates. Background Art

[0002] Microchannel Plate (MPP) is a special optical fiber device with the advantages of small size, light weight, high resolution, high gain, low noise and low voltage. It uses the secondary electron emission characteristics to multiply the electrons that collide with the inner wall (channel) of the microchannel at high speed, and achieve an increase of more than 10,000 times the electron flow. The MCP has become the core component of the low-light image intensifier due to its excellent electron multiplication function. The various performances of the MCP determine the performance of the low-light night vision device.

[0003] Imaging is one of the important indicators for testing the performance of microchannel plates. The principle of microchannel plate imaging mainly involves photoelectric conversion, electron multiplication and light emission processes. The electron source emits electrons, which hit the input surface of the microchannel plate and stimulate several secondary electrons into the vacuum. The secondary electrons hit the inner wall of the microchannel plate many times to achieve electron multiplication, and then are accelerated by the anode high voltage to stimulate the fluorescent screen to emit light, which is converted into an optical image with enhanced brightness. The human eye obtains the information of the fluorescent screen imaging, analyzes the optical image, and judges some defects of the microchannel plate in imaging. Obvious bright spots or dark spots on the fluorescent screen are defects, and microchannel plates with defects are recorded as unqualified.

[0004] The existing testing method is to install each microchannel plate on a test fixture welded with a fluorescent screen for imaging testing, select a workstation and set an electron source under it, rotate different workstations to the tested location during testing, and the electron source emits electrons corresponding to different microchannel plates and fluorescent screens. The human eye identifies problems on the fluorescent screen to determine defects in the imaging of the microchannel plate.

[0005] However, this testing method has many problems: (1) Each microchannel plate must be installed with a fluorescent screen when testing, and the installation process is cumbersome and can easily cause damage to the microchannel plate. (2) The fluorescent screen is easily damaged during the installation process, such as phosphor falling off and scratches on the fluorescent screen, which seriously reduces the service life of the fluorescent screen and increases production costs. (3) The damage to each fluorescent screen is different and difficult to count. These defects will appear together during imaging, and it is impossible to effectively and quickly distinguish whether the defect belongs to the fluorescent screen or the microchannel plate, which seriously reduces work efficiency. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a device and method for detecting microchannel plate imaging defects, and the technical problem to be solved is to accurately and quickly determine the microchannel plate imaging defects.

[0007] The purpose of the present invention and the technical problem to be solved are achieved by adopting the following technical solutions. A device for detecting microchannel plate imaging defects proposed by the present invention comprises:

[0008] An imaging detection unit, which includes a microchannel plate fixing fixture, a fluorescent screen, a control mechanism and a camera mechanism;

[0009] an emission source unit including an electron source and an emission source power supply connected to each other; and

[0010] The vacuum unit has two ends connected to the imaging detection unit and the emission source unit respectively; the vacuum unit includes a vacuum chamber and a vacuum pump group arranged outside the vacuum chamber.

[0011] Preferably, in the aforementioned device for detecting imaging defects of a microchannel plate, the microchannel plate fixing fixture is arranged inside the vacuum unit.

[0012] Preferably, in the aforementioned device for detecting imaging defects of a microchannel plate, the fluorescent screen is fixed inside the vacuum chamber by a clamp.

[0013] Preferably, in the aforementioned device for detecting imaging defects of a microchannel plate, fluorescent powder is coated below the fluorescent screen.

[0014] Preferably, in the aforementioned device for detecting imaging defects of a microchannel plate, the control mechanism is disposed outside the vacuum chamber.

[0015] Preferably, in the aforementioned device for detecting imaging defects of a microchannel plate, the camera mechanism is placed above the vacuum chamber; and the camera mechanism is directly opposite to the top of the fluorescent screen.

[0016] Preferably, in the aforementioned microchannel plate imaging defect detection device, the camera mechanism includes an optical observation lens, a charge-coupled device and a display terminal; the optical observation lens is arranged above the vacuum chamber and opposite to the fluorescent screen; a charge-coupled device is inserted into the optical observation lens, and the charge-coupled device is connected to the display terminal.

[0017] Preferably, in the aforementioned device for detecting imaging defects of a microchannel plate, the display terminal is a computer, a mobile phone or a tablet.

[0018] Preferably, in the aforementioned microchannel plate imaging defect detection device, the vacuum chamber is a hollow cylindrical structure, a vacuum cover is installed on the top, an inner ring structure, an outer ring structure interconnected with the inner ring structure, and a tray for carrying the test station are arranged inside; a robotic arm is provided on the vacuum cover.

[0019] Preferably, in the aforementioned device for detecting imaging defects of a microchannel plate, a stepper motor is provided inside the inner ring structure; and the stepper motor is connected to a tray.

[0020] Preferably, in the aforementioned microchannel plate imaging defect detection device, a plurality of test stations are evenly distributed on the outer edge of the tray, and a majority of the test stations are connected to the outer ring structure; a fluorescent screen fixture is welded above one of the plurality of test stations, a fluorescent screen is fixed on the fluorescent screen fixture, and microchannel plate fixing fixtures are installed on the remaining test stations, and the microchannel plate fixing fixtures are clamped with the microchannel plate to be tested; the outlet of the electron source is directly opposite to the electron source, the microchannel plate to be tested, the fluorescent screen and the camera mechanism.

[0021] Preferably, in the aforementioned microchannel plate imaging defect detection device, most of the test stations are connected to the outer ring structure through a polytetrafluoroethylene block, three electrode probes are inserted into the polytetrafluoroethylene block, and both ends of each of the electrode probes are respectively connected to the control unit and the microchannel plate fixing fixture; each test station is padded with a ring made of polytetrafluoroethylene.

[0022] Preferably, in the aforementioned device for detecting imaging defects of a microchannel plate, the vacuum pump group includes a mechanical pump and a molecular pump, and the mechanical pump and the molecular pump are connected in parallel to the vacuum chamber.

[0023] The purpose of the present invention and the solution to the technical problem can also be achieved by adopting the following technical solutions. A method for detecting microchannel plate imaging defects proposed by the present invention comprises the following steps:

[0024] (1) The fluorescent screen, the standard microchannel plate, and the microchannel plate to be tested are respectively placed in corresponding test stations in the vacuum chamber;

[0025] (2) Start the vacuum pump group to evacuate the air until the pressure is lower than 4.9E-3Pa and then start measuring;

[0026] (3) Turn on the display terminal, control unit, and electronic source, and observe the fluorescent screen on the computer to obtain the best contrast;

[0027] (4) After the electron source is preheated, the measurement begins. At this time, the standard microchannel plate is first imaged at the measured station, and the fluorescent screen is observed. The display terminal takes a picture of the fluorescent screen at this time as a standard comparison photo;

[0028] (5) The microchannel plate to be tested is rotated to the testing station in sequence by a stepper motor, and the electrons emitted by the electron source are multiplied by the microchannel plate and then bombarded onto the phosphor, causing the phosphor screen to emit light, and the display terminal captures the image at this time;

[0029] (6) After the image to be tested and the standard microchannel plate image are processed by image recognition, black dots, bright dots, dark spots, and white spots are automatically extracted;

[0030] (7) After the test is completed, turn off all voltages of the electron source and the control mechanism, fill the vacuum chamber with nitrogen, and when the air pressure becomes atmospheric pressure, open the vacuum cover and take out the microchannel plate to be tested.

[0031] Preferably, in the aforementioned method for detecting imaging defects of a microchannel plate, in step (1), the fluorescent screen is a fluorescent screen with no scratches on the surface, fine and smooth phosphor particles on the bottom, uniform and without scratches, and uniform imaging without white spots and black spots; the standard microchannel plate is a microchannel plate with no black spots, bright spots, white spots or black spots on the imaging.

[0032] Preferably, in the aforementioned method for detecting defects in microchannel plate imaging, step (6) specifically includes: performing grayscale normalization processing on the fluorescent screen imaging photograph of the microchannel plate to be tested and the fluorescent screen photograph of the standard microchannel plate, using contrast-limited histogram equalization combined with a halo detection method of threshold segmentation to remove original defects on the screen, and realizing automatic extraction of four types of defects on the microchannel plate imaging: black spots, bright spots, black spots, and white spots.

[0033] By means of the above technical solution, the device and method for detecting microchannel plate imaging defects proposed by the present invention have at least the following beneficial effects:

[0034] The present invention can effectively distinguish scratches and dust on the fluorescent screen from defects on the imaging of the microchannel plate, accurately judge the defects of the imaging of the microchannel plate, and can be used for imaging tests of all models of microchannel plates. The cumulative detection results of 25,892 microchannel plate imaging defects in 5 months show that there are 13,486 black spots recognized by human eyes, and 12,852 black spots recognized by machines, with a recognition accuracy of 12,852 / 13,846, equal to 95.3%. After the same calculation, the recognition accuracy of bright spots can reach 94.5%, the recognition accuracy of black spots can reach 91.4%, and the recognition accuracy of white spots can reach 80%. Combined with human eye observation, the work efficiency and the accuracy of microchannel plate imaging defect detection can be greatly improved, effectively avoiding the problem of scrapping of low-light image intensifiers due to inaccurate judgment of microchannel plate imaging defects, and saving production costs to the greatest extent, reducing the problems of fluorescent screen scratches caused by repeated carding. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural schematic diagram of a device for detecting imaging defects of a microchannel plate according to the present invention;

[0036] Figure 2 A top view of a test station in a device for detecting imaging defects of a microchannel plate according to the present invention;

[0037] Figure 3A An imaging test diagram of a standard microchannel plate of the present invention;

[0038] Figure 3B A test diagram for testing a microchannel plate of the present invention;

[0039] Figure 3C The image defect map of the microchannel plate under test is displayed after the image processing of the present invention. DETAILED DESCRIPTION

[0040] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description of the specific implementation, features and effects of the microchannel plate imaging defect detection device and method proposed by the present invention in combination with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "embodiment" does not necessarily refer to the same embodiment. In addition, specific features or characteristics in one or more embodiments may be combined in any suitable form.

[0041] It should be noted that all directional indications in the present invention (such as up, down, left, right, etc.) are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly. The connection can be a direct connection or an indirect connection.

[0042] like Figure 1-Figure 2 As shown, some embodiments of the present invention provide a device for detecting imaging defects of a microchannel plate (MCP):

[0043] The imaging detection unit comprises a microchannel plate fixing fixture, a fluorescent screen 3, a control mechanism 8 and a camera mechanism 2; the microchannel plate fixing fixture is used to fix the microchannel plate inside the vacuum unit.

[0044] An emission source unit, which includes an electron source 7 and an emission source power supply connected to each other by wires; the electron source may be a tantalum wire, which provides input electrons for the microchannel plate;

[0045] The vacuum unit has two ends respectively connected to the imaging detection unit 2 and the emission source unit to provide a vacuum environment for the imaging of the microchannel plate; the vacuum unit includes a vacuum chamber 1 and a vacuum pump group 6 arranged outside the vacuum chamber 1, and this arrangement is to extract the gas in the vacuum chamber 1.

[0046] In some embodiments of the present invention, the microchannel plate test fixture is arranged inside the vacuum unit. The fluorescent screen 3 is fixed inside the vacuum chamber 1 by the fixture. The microchannel plate must be in a vacuum state when working, otherwise the residual gas molecules will collide with the multiplied electrons to generate positive ions, which are the main source of noise, thereby affecting the working stability of the microchannel plate.

[0047] In some embodiments of the present invention, phosphor 4 is coated below the phosphor screen 3, and the secondary electrons increase in energy after being multiplied by the microchannel plate, which excites the phosphor to emit light of a specific color to form an image on the phosphor screen.

[0048] In some embodiments of the present invention, the control mechanism is arranged outside the vacuum chamber 1; specifically, the control mechanism mainly controls the voltage of the microchannel plate in the vacuum chamber during the test process, including the anode voltage, the cathode voltage, and the microchannel plate pressure, and reads the current value passing through the microchannel plate. The adjustable voltage range of the microchannel plate is 0 to 1000V.

[0049] In some embodiments of the present invention, the camera mechanism 2 is placed above the vacuum chamber 1. The camera mechanism 2 is directly opposite to the top of the fluorescent screen 3, and is used to take pictures when the fluorescent screen is lit to record the microchannel plate test image.

[0050] In some embodiments of the present invention, the camera mechanism 2 includes an optical observation lens, a charge-coupled device and a display terminal; the optical observation lens is arranged above the vacuum chamber 1 and opposite to the fluorescent screen; a charge-coupled device is inserted into the optical observation lens, and the charge-coupled device is connected to an external display terminal, so the camera mechanism 2 cannot be placed in the vacuum chamber 1. The optical observation lens is used to observe the lit fluorescent screen, and the display terminal records the photo (i.e., the microchannel plate test image).

[0051] In some embodiments of the present invention, the vacuum chamber 1 is a hollow cylindrical structure, with a vacuum cover installed on the top, and an inner ring structure 15, an outer ring structure 12 interconnected with the inner ring structure 15, and a tray 9 for carrying a test station are arranged inside the vacuum cover; a mechanical arm 14 is arranged on the vacuum cover, and the vacuum cover can be opened or closed by the switch of the mechanical arm 14. A stepper motor 13 is arranged inside the inner ring structure to enable back and forth rotation between different stations; the inner ring structure 15 is used to connect and fix the stepper motor 13, and the outer ring structure 12 is used to connect the test station 11 with the microchannel plate fixing fixture. The stepper motor 13 drives the tray 9 to rotate, thereby rotating the test station.

[0052] In a specific implementation, the cross-sectional diameter of the vacuum chamber 1 may be 700 mm, the height may be 150 mm, and the volume may be about 60 L, and is used to provide a vacuum environment for microchannel plate testing.

[0053] In some embodiments of the present invention, the inner ring structure 15, the outer ring structure 12, and the tray 9 are made of stainless steel because stainless steel has high strength, good welding performance, and excellent mechanical properties.

[0054] In some embodiments of the present invention, a plurality of test stations 11 are evenly distributed on the outer edge of the tray 9, and most of the test stations 11 are connected to the outer ring structure 12 through a polytetrafluoroethylene block 18. Three electrode probes 17 (output electrode, input electrode, anode) are inserted into the polytetrafluoroethylene block 18, and both ends of each electrode probe 17 are respectively connected to the control unit and the microchannel plate fixing fixture for applying voltage to the microchannel plate.

[0055] Furthermore, each test station is padded with a circular ring 16 of suitable size made of polytetrafluoroethylene material (with an insulating function), a fluorescent screen fixture 10 is welded above one of the majority of the test stations 11, and a fluorescent screen 3 is fixed on the fluorescent screen fixture 10, and the remaining test stations 11 are installed with microchannel plate fixing fixtures, and the microchannel plate fixing fixtures are clamped with the microchannel plate 5 to be tested.

[0056] Specifically, the circular rings 16 of the remaining test stations 11 are provided with microchannel plate fixing fixtures.

[0057] The stepper motor 13 is connected to the tray 9 and drives the tray 9 to rotate. The emission port of the electron source 7 is aligned with the electron source 7 , the microchannel plate 5 to be tested, the fluorescent screen 3 and the camera mechanism 2 .

[0058] In some embodiments of the present invention, the vacuum pump group 6 includes a mechanical pump and a molecular pump, which are connected in parallel to the vacuum chamber. The molecular pump takes a long time to start, and the gas is in a molecular flow state, so a front pump is required. Therefore, the mechanical pump first compresses and discharges the gas, pumps the atmospheric pressure to below 10Pa, and then connects the molecular pump. On the basis of the vacuum pump, the vacuum degree is further increased to a negative value, and the vacuum chamber 1 is used to provide a vacuum environment. The vacuum degree required for the microchannel plate to work is ≤4.9E-3Pa.

[0059] In some embodiments of the present invention, the display terminal is a computer, a mobile phone or a tablet, which is easy for human eyes to observe and record.

[0060] In addition, in order to more accurately and quickly determine the microchannel plate imaging defects, some embodiments of the present invention also provide a method for detecting microchannel plate imaging defects, comprising the following steps:

[0061] (1) Select a fluorescent screen with good conditions (no scratches on the surface, fine and smooth phosphor particles on the bottom, uniform and without scratches), select a microchannel plate with no black spots, bright spots, white spots or black spots on the image as a standard microchannel plate, and install the fluorescent screen, the standard microchannel plate and the microchannel plate to be tested into the corresponding test stations in the vacuum chamber respectively.

[0062] (2) Turn on the vacuum pump control power supply, start the vacuum pump group 6 to evacuate the air, and start measuring when the air pressure is lower than 4.9E-3Pa.

[0063] The vacuum pump needs a motor to provide driving force. When the motor starts, current is input through the starter controller and a rotating electric field is generated inside. This rotating electric field converts electrical energy into motion energy through the motor's electronic coil and drives the rotor to rotate. The impeller on the rotor is responsible for the vacuum pump's extraction.

[0064] (3) Turn on the display terminal, the electron source, the control mechanism, apply voltage, including anode voltage, cathode voltage, and microchannel plate voltage, and light up the fluorescent screen. Adjust the exposure time, gain, and focal length of the optical lens to make the fluorescent screen photo appear clearest on the computer, take a test photo at this time, and observe the fluorescent screen on the computer.

[0065] (4) After the electron source is preheated for more than ten minutes (the electron source is a tantalum wire, and the ten-minute preheating allows the tantalum wire to be fully lit and the light emitted to be more uniform), the measurement begins. At this time, the standard microchannel plate is first imaged at the measured station, and the fluorescent screen is observed. The display terminal takes a picture of the fluorescent screen at this time as a standard comparison photo.

[0066] (5) The microchannel plate to be tested is rotated to the testing station in sequence by a stepper motor, the electron source emits electrons to make the fluorescent screen glow, and the display terminal captures the image at this time.

[0067] (6) After the image to be tested and the standard microchannel plate test image are processed by image recognition, the extraction of black spots, bright spots, black spots and white spots is automatically realized; specifically, the fluorescent screen imaging photo of the microchannel plate to be tested and the fluorescent screen photo of the standard microchannel plate are grayscale normalized, and the original defects on the screen are removed by using contrast-limited histogram equalization combined with the halo detection method of threshold segmentation, so as to realize the automatic extraction of four kinds of defects black spots, bright spots, black spots and white spots on the microchannel plate imaging; black spots: all black dot-shaped ones with clear contours; bright spots: all white dot-shaped ones with clear contour boundaries; black spots: have a large area, arbitrary shape and have gradient color characteristics, often appearing as patches or black smoke shapes; white spots: have a large area, are generally long strips, often appearing as tree forks or smoke shapes, without clear boundaries, and the color gradually fades from the center to the surroundings and blends into the background. The processing by image recognition specifically includes: collecting test photos of different microchannel plates in BMP format, converting the image files into grayscale images after unifying the paths by calling the cvCvtColor function, and performing histogram equalization on the obtained grayscale images; performing Gaussian filtering to eliminate the influence of noise, performing Laplace operation on the Gaussian filtered image, and performing threshold processing after obtaining the second-order derivative of the image, extracting edge pixels, and then combining with the conventional halo detection method and using the hash algorithm to remove duplicates, so as to extract black spots and bright spots on the test image; at the same time, using the shape, size, and dtype functions, obtaining ROI area extraction and enhancement through the pixel matrix, combining with edge detection, and identifying black spots and white spots on the image.

[0068] (7) After the test, turn off the electron source and other power sources, and fill the vacuum chamber with high-purity nitrogen (98.5% or more) 15 to 30 minutes later, waiting for the electron source to be completely extinguished to avoid oxidation. The filling amount is the volume of the vacuum chamber, for example, it can be about 60L, and it can be filled in 1 minute, the rate is 60L / min, to avoid oxidation of the electron source that is not completely extinguished, shortening the service life. When it becomes atmospheric pressure, use the robot arm to open the vacuum cover of the vacuum chamber and take out the microchannel plate to be tested.

[0069] In the above technical scheme, the present invention sets a three-layer structure at different heights in a vacuum chamber, the bottom layer is an electron source, the middle layer is a microchannel plate test fixture, and the highest layer is a welding fluorescent screen fixture above a selected workstation. Only one fluorescent screen is used throughout the test, and a test picture of a standard microchannel plate is taken in advance as a blank control. The rotating workstations are tested corresponding to different microchannel plates, and a photo of the fluorescent screen is taken with a camera mechanism when the fluorescent screen is lit, which is a microchannel plate imaging test picture. After the microchannel plate imaging test picture and the blank control picture are grayscale normalized, the extraction of black spots, bright spots, black spots, and white spots is realized by using a halo detection method with limited contrast histogram equalization combined with threshold segmentation. This method can effectively distinguish scratches and dust on the fluorescent screen from black spots on the microchannel plate, thereby realizing the automatic extraction of black spots, bright spots, black spots, and white spots.

[0070] Contrast-limited histogram equalization is an improvement on traditional histogram equalization. By redistributing the grayscale of the image, the grayscale range of the image is wider. On the basis of enhancing the contrast of the image, the grayscale distribution is further restricted. Usually a threshold is set. When the number of pixels of a certain grayscale exceeds this threshold, it is restricted to better control the degree of image enhancement, reduce over-enhancement, reduce the sensitivity to noise, and make the image smoother. Threshold segmentation is a segmentation method based on the grayscale value of pixels. According to the set threshold, the pixels in the image are divided into two categories, one is the pixels above the threshold, and the other is the pixels below the threshold. In halo detection, the halo area can be separated from other areas. Then, the filtering method is used to smooth the halo area, remove the original defects on the screen, and automatically identify the defects on the microchannel plate imaging.

[0071] The method can effectively distinguish scratches and dust on the fluorescent screen from defects on the microchannel plate imaging, accurately judge the defects on the microchannel plate imaging, improve work efficiency, and effectively avoid the problem of scrapping the low-light image intensifier due to inaccurate judgment of the microchannel plate imaging defects. It also saves production costs to the greatest extent and reduces problems such as fluorescent screen scratches caused by repeated card installation.

[0072] The present invention will be further described below in conjunction with specific embodiments, but this should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by technicians in this field based on the above-mentioned contents of the present invention still fall within the scope of protection of the present invention.

[0073] Embodiment 1:

[0074] Taking a microchannel plate with an outer diameter of 25 mm as an example, the method for detecting microchannel plate imaging defects includes the following steps:

[0075] (1) Place the microchannel plate to be tested into the microchannel plate fixture and put it into the test station. Select a microchannel plate that has been tested and has no defects as the standard microchannel plate. Select a fluorescent screen with no scratches on the surface and fine and smooth phosphor particles on the bottom, evenly distributed without scratches. Install them on their respective fixtures and put them into the vacuum chamber (before placing the fluorescent screen and microchannel plate into the fixture, blow them clean with a nitrogen gun to prevent dust from entering and causing the fluorescent screen to ignite and penetrate the microchannel plate);

[0076] (2) Start evacuating the air until the vacuum gauge shows that the air pressure is 4.9E-3Pa. (Voltage can be applied to the microchannel plate only under high vacuum conditions to avoid discharge in the channel holes). Install the optical observation lens on the observation window (considering the size of the image on the fluorescent screen, choose a 15x microscope eyepiece to observe the output image) and the charge-coupled device and connect them to the computer.

[0077] (3) Turn on the computer, control unit, and electron source, and take a photo when the photo on the fluorescent screen is clearest when observed by human eyes on the computer; set the anode voltage to 4500 V, the microchannel plate voltage to 850 V, and the cathode voltage to -160 V;

[0078] (4) Start measuring after the electron source has been preheated for ten minutes. Rotate the test station to the standard microchannel plate, observe the fluorescent screen with an optical observation lens, adjust the exposure time and gain so that the image on the fluorescent screen is clearest for human eyes to observe. The computer captures the fluorescent screen image at this time as a standard comparison photo (the exposure time is generally set to 1500ms and the gain is 200%). During image detection, in order to clearly see the lit fluorescent screen, it is necessary to be in a darker environment. Therefore, when taking photos, increase the exposure time and increase the amount of light to make the picture clearer and more natural. Increasing the gain can increase the sensitivity of the lens to light, but it will also amplify the noise signal. Therefore, set the gain to the minimum when taking photos. According to tests, the exposure time is generally set to 1500ms and the gain is set to 200% when the fluorescent screen is clearest and most suitable for human eye observation.

[0079] (5) The stepper motor rotates the test station to each microchannel plate to be tested, and the electron source is continuously lit to emit electrons to make the fluorescent screen glow. The exposure time is 1500ms and the gain is 200%. The computer records the fluorescent screen image at this time;

[0080] (6) The fluorescent screen imaging photos of the microchannel plate to be tested and the fluorescent screen photos of the standard microchannel plate are grayscale normalized, and the original defects on the screen are removed by contrast-limited histogram equalization combined with the halo detection method of threshold segmentation, so as to realize the automatic extraction of four kinds of defects black spots, bright spots, black spots and white spots on the microchannel plate imaging; it specifically includes: collecting test photos of different MCPs in Bmp format, converting the image files into grayscale images after unifying the path of the image files and calling the cvCvtColor function, and performing histogram equalization on the obtained grayscale images. Then, Gaussian filtering is performed to eliminate the influence of noise, and the image after Gaussian filtering is subjected to Laplace operation to obtain the second-order derivative of the image and then threshold processing is performed to extract edge pixels, and then combined with the conventional halo detection method, the hash algorithm is used to remove duplicates, so that the black spots and bright spots on the test image can be extracted. At the same time, the shape, size, and dtype functions are used to obtain ROI area extraction and enhancement through the pixel matrix, and the black spots and white spots on the image are identified by combining edge detection.

[0081] (7) After the test, turn off the electron source and constant current source. After 15 minutes, fill the vacuum chamber with industrial nitrogen (purity of 98.5%) to an atmospheric pressure of 1 atm, then open the vacuum cover and take out the microchannel plate to be tested. The amount of industrial nitrogen filled is the volume of the vacuum chamber, about 60 L, which can be filled in 1 minute at a rate of 60 L / min.

[0082] Figure 3A is an imaging test diagram of the standard microchannel plate of the present invention, Figure 3B The test image of the test microchannel plate of the present invention is obtained by unifying the paths of the two images and processing them through the image recognition system. Figure 3C , Figure 3C That is to test the imaging defects on the microchannel plate, a black dot and a black spot.

[0083] The test method can be applied to imaging defect testing of microchannel plates of any specifications and any plate types, and only requires configuration of test fixtures and fluorescent screens of the same specifications.

[0084] After the test steps of Example 1, Table 1 summarizes the total test data of imaging defects (black spots, bright spots, dark spots, white spots) for all microchannel plates (a total of 25,892 plates) within five months.

[0085] Table 1

[0086] Black spot / piece Highlights Black spots / stripes White spots / strips Human Eye Recognition 13486 9873 453 679 Image Recognition 12852 9329 414 543 Recognition accuracy 95.3％ 94.5％ 91.4％ 80.0％

[0087] Among them, accuracy rate = number of images recognized by the image recognition system / number of images recognized by the human eye.

[0088] From the data in Table 1, it can be seen that the recognition accuracy of black spots can reach 95.3%, the recognition accuracy of bright spots can reach 94.5%, the recognition accuracy of black spots can reach 91.4%, and the recognition accuracy of white spots can reach 80%. This shows that the detection device for microchannel plate imaging defects of the present invention can more accurately determine microchannel plate imaging defects.

[0089] In the specification of the present invention, a lot of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some embodiments, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this specification.

[0090] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0091] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

[0092] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A device for detecting microchannel plate imaging defects, characterized in that: include: An imaging detection unit, which includes a microchannel plate fixing fixture, a fluorescent screen, a control mechanism and a camera mechanism; an emission source unit including an electron source and an emission source power supply connected to each other; and The vacuum unit has two ends connected to the imaging detection unit and the emission source unit respectively; the vacuum unit includes a vacuum chamber and a vacuum pump group arranged outside the vacuum chamber.

2. The device for detecting microchannel plate imaging defects as claimed in claim 1, characterized in that: The microchannel plate fixing fixture is arranged inside the vacuum unit.

3. The device for detecting microchannel plate imaging defects as claimed in claim 1, characterized in that: The fluorescent screen is fixed inside the vacuum chamber by a clamp; the bottom of the fluorescent screen is coated with fluorescent powder.

4. The device for detecting microchannel plate imaging defects as claimed in claim 1, characterized in that: The control mechanism is arranged outside the vacuum chamber.

5. The device for detecting microchannel plate imaging defects as claimed in claim 1, characterized in that: The camera mechanism is placed above the vacuum chamber; and the camera mechanism is directly opposite to the top of the fluorescent screen.

6. The device for detecting microchannel plate imaging defects as claimed in claim 1, characterized in that: The camera mechanism includes an optical observation lens, a charge coupled device and a display terminal; the optical observation lens is arranged above the vacuum chamber and opposite to the fluorescent screen; a charge coupled device is inserted into the optical observation lens, and the charge coupled device is connected to the display terminal; the display terminal is a mobile phone, a computer or a tablet.

7. The device for detecting microchannel plate imaging defects as claimed in claim 1, characterized in that: The vacuum chamber is a hollow cylindrical structure with a vacuum cover installed on the top, an inner ring structure, an outer ring structure interconnected with the inner ring structure and a tray for carrying the test station are arranged inside the vacuum cover; a robotic arm is arranged on the vacuum cover; a stepper motor is arranged inside the inner ring structure; the stepper motor is connected to the tray; a plurality of test stations are evenly distributed on the outer edge of the tray, and most of the test stations are connected to the outer ring structure; a fluorescent screen fixture is welded above one of the plurality of test stations, and a fluorescent screen is fixed on the fluorescent screen fixture, and microchannel plate fixing fixtures are installed on the remaining test stations, and the microchannel plate fixing fixture is clamped with a microchannel plate to be tested; the electron source outlet is directly opposite to the electron source, the microchannel plate to be tested, the fluorescent screen and the camera mechanism.

8. The device for detecting microchannel plate imaging defects as claimed in claim 7, characterized in that: Most of the test stations are connected to the outer ring structure through a polytetrafluoroethylene block, and three electrode probes are inserted into the polytetrafluoroethylene block. The two ends of each electrode probe are respectively connected to the control unit and the microchannel plate fixture; each test station is padded with a polytetrafluoroethylene ring; the vacuum pump group includes a mechanical pump and a molecular pump, and the mechanical pump and the molecular pump are connected to the vacuum chamber in parallel.

9. A method for detecting microchannel plate imaging defects, characterized in that: The following steps are involved: (1) The fluorescent screen, the standard microchannel plate, and the microchannel plate to be tested are respectively placed in corresponding test stations in the vacuum chamber; (2) Start the vacuum pump group to evacuate the air until the pressure is lower than 4.9E-3Pa and then start measuring; (3) Turn on the display terminal, control unit, and electronic source, and observe the fluorescent screen on the computer to obtain the best contrast; (4) After the electron source is preheated, the measurement begins. At this time, the standard microchannel plate is first imaged at the measured station, and the fluorescent screen is observed. The display terminal takes a picture of the fluorescent screen at this time as a standard comparison photo; (5) The microchannel plate to be tested is rotated to the testing station in sequence by a stepper motor, and the electrons emitted by the electron source are multiplied by the microchannel plate and then bombarded onto the phosphor, causing the phosphor screen to emit light, and the display terminal captures the image at this time; (6) After the image to be tested and the standard microchannel plate image are processed by image recognition, black dots, bright dots, dark spots, and white spots are automatically extracted; (7) After the test is completed, turn off all voltages of the electron source and the control mechanism, fill the vacuum chamber with nitrogen, and when the air pressure becomes atmospheric pressure, open the vacuum cover and take out the microchannel plate to be tested.

10. The method for detecting microchannel plate imaging defects according to claim 9, characterized in that: In step (1), the fluorescent screen has no scratches on the surface, the fluorescent powder particles on the bottom are fine and smooth, uniform and without scratches, and the imaging is uniform without white spots and black spots; the standard microchannel plate is a microchannel plate with no black spots, bright spots, white spots and black spots in the imaging; step (6) specifically includes: grayscale normalization processing of the fluorescent screen imaging photo of the microchannel plate to be tested and the fluorescent screen photo of the standard microchannel plate, using contrast-limited histogram equalization combined with a halo detection method combined with threshold segmentation to remove the original defects on the screen, and realizing automatic extraction of four kinds of defects black spots, bright spots, black spots and white spots in the microchannel plate imaging.

Images