Device and method for testing stability of streak tube laser radar detector along with time

Abstract

The invention discloses a device for testing the stability of a streak tube laser radar detector along with time, and the device comprises a pulse signal trigger, an upper computer, a laser collimation device, and a laser signal streak tube imaging device. The laser signal streak tube imaging device is composed of a streak tube detector and a CCD camera. According to the invention, after the collimated laser beam passes through the streak tube detector, the CCD camera is utilized to store the obtained laser spot image into the upper computer, and a large amount of image data is stored through long-time operation of the device. And analyzing the offset condition of the mass center position of the light spot image along with the working time of the testing device through a processing method such as mass center extraction so as to achieve the purpose of testing the stability of the streak tube detector along with the time. The system can accurately collimate light beams, realizes mode switching, ensures normal work of each device of the system, and effectively tests the stability of the streak tube detector.

Description

Technical Field

[0001] The invention belongs to the field of real-time image processing and relates to a device and method for testing the stability of a streak tube detector in a streak tube imaging laser radar. Background Art

[0002] LiDAR (LiDAR) is widely used in both military and civilian applications due to its high precision and 24 / 7 operation. However, traditional LiDAR has limitations, such as unclear target imaging and improved anti-interference capabilities. Against this backdrop, streak tube imaging LiDAR (STIL) has emerged. A streak tube detector is a vacuum photoelectric imaging device based on the external photoelectric effect and microchannel plate low-light-level imaging. It can shape and focus high-speed electrons, significantly improving image quality and enhancing LiDAR detection performance.

[0003] In streak tube imaging LiDAR systems, the stability of the streak tube detector is crucial. Streak tube imaging LiDARs are typically used to measure parameters such as target distance and velocity. The stability of the streak tube detector is closely related to measurement accuracy. When the streak tube detector is stable, the characteristics of the laser beam (such as wavelength and intensity) remain stable, allowing for more accurate measurement using the information returned by the laser signal after interacting with the target. If the streak tube detector is unstable, parameters such as the propagation direction and intensity distribution of the laser beam will change. For example, even slight vibrations of the streak tube detector can cause the optical axis of the laser beam to shift, resulting in a blurred image on the imaging plane. This is similar to the blurring of a photograph when the camera is shaken. This can severely affect the quality of the LiDAR image of the target, making subsequent tasks such as target identification, classification, and measurement inaccurate. Summary of the Invention

[0004] Given the importance of streak tube detector stability to measurement accuracy in streak tube imaging lidar, the present invention provides a device and method for testing the temporal stability of streak tube lidar detectors. This method tests the streak tube's stability by processing image data of laser signals passing through the streak tube. After a collimated laser beam passes through the streak tube detector, the captured laser spot image is stored in a host computer using a CCD camera. The device operates over a long period of time to store large amounts of image data. Subsequently, centroid extraction and other processing methods are used to analyze the deviation of the spot image's centroid position over time during the test device's operation, thereby testing the temporal stability of the streak tube detector. This method accurately collimates the beam and implements mode switching, ensuring the proper operation of all system components and effectively testing the streak tube detector's stability.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A device for testing the temporal stability of a streak tube laser radar detector includes a pulse signal trigger, a host computer, a laser collimation device, and a laser signal streak tube imaging device, wherein:

[0007] The laser collimation device is composed of a laser and a collimation system. The laser beam generated by the laser is processed by the collimation system to form a high-quality, high-collimation parallel laser beam;

[0008] The collimation system is an "aperture-collimation lens group-aperture" collimation structure consisting of a first aperture, a collimating lens group, and a second aperture. The laser beam generated by the trigger pulse of the laser first passes through the first aperture to remove stray light at the edge; then passes through the collimating lens group to collimate the divergent laser beam into a parallel beam; and then passes through the second aperture to optimize the light intensity distribution of the beam. The second aperture should be close to the streak tube detector to reduce the divergence of the beam and minimize the impact of changes in the intensity distribution of the laser spot.

[0009] The laser signal streak tube imaging device is composed of a streak tube detector and a CCD camera. The streak tube detector images the laser pulse into a streak image and switches the working mode through a scanning circuit. The CCD camera receives the streak image transmitted by the streak tube detector and transmits the collected image data to the host computer.

[0010] The pulse signal trigger is used to provide trigger pulses, and provides trigger pulses to the laser, streak tube scanning circuit, and CCD camera through different channels;

[0011] The host computer is used to manipulate the pulse signal trigger to control the frequency and delay of the trigger pulses output by different channels, receive the laser signal image data collected by the CCD camera and perform centroid extraction processing on the image data, and obtain the offset of the laser beam as the test device works over time by analyzing the offset of the centroid position in the image on the X-axis and Y-axis as the test device works over time, thereby testing the stability of the streak tube detector over time.

[0012] A method for testing the temporal stability of a streak tube laser radar detector comprises the following steps:

[0013] Step 1: Generate laser pulses: The upper computer controls the pulse signal trigger to input a trigger pulse to the laser in the laser alignment system to generate laser pulses;

[0014] Step 2: Use the collimation system to collimate the laser pulse: Use the collimation system in the laser collimation device to collimate the laser beam output from the laser to ensure that it has good directionality and parallelism before entering the streak tube detector;

[0015] Step 3: Timing control of the streak tube detector scanning circuit and CCD camera: Use the host computer to manipulate the pulse signal trigger to input trigger pulses to the streak tube detector scanning circuit and CCD camera respectively, and accurately set the trigger pulse frequencies input to the laser, streak tube detector scanning circuit and CCD camera to match each other. At the same time, different trigger pulse delays are set according to imaging requirements;

[0016] Step 4: Acquisition of laser pulse fringe image: The trigger pulse provided by the pulse signal trigger enables the laser collimation device and the laser signal streak tube imaging device to work normally. The collimated laser beam passes through the laser signal streak tube imaging device and is output as a two-dimensional fringe image. The light spots in the fringe image correspond one-to-one to the laser pulse information.

[0017] Step 5. Laser pulse streak image processing: The laser pulse streak image captured by the CCD camera is transmitted to the host computer for centroid extraction processing. The stability of the streak tube detector over time is judged based on the offset of the center of mass position of the light spot with the working time of the test device. The stability of the streak tube detector under different working modes is tested by designing a scanning circuit. The working mode switching method of the streak tube detector includes: adding a scanning circuit at both ends of the deflection electrode of the streak tube detector, designing a switch at one end of the scanning circuit and grounding the other end. When the switch is connected to the positive pole of the power supply, a deflection voltage exists between the deflection electrodes, and the streak tube detector switches to the dynamic mode; when the switch is connected to the ground wire, the voltage between the deflection electrodes is zero, and it switches to the static mode.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] 1. The present invention controls the laser, streak tube detector scanning circuit, and CCD camera respectively through different channels of the pulse generator, ensuring that the laser generated by the trigger pulse passes through each device of the system and the device can work normally; 2. The present invention can accurately collimate the laser beam into a uniform, focused, parallel beam through the "aperture-collimating lens group-aperture" system;

[0020] 3. The present invention realizes the simple switching of the working mode of the streak tube detector by designing the scanning circuit of the streak tube detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the device module for testing the stability of the streak tube detector for streak tube imaging lidar;

[0022] Figure 2 Schematic diagram of the device for controlling the operating mode of the streak tube detector of the streak tube imaging lidar. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further described below with reference to the accompanying drawings, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention that does not depart from the spirit and scope of the technical solution of the present invention should be included in the scope of protection of the present invention.

[0024] Specific embodiment 1: This embodiment provides a device for testing the stability of a streak tube laser radar detector over time, such as Figure 1 As shown, the test device includes a pulse signal trigger, a host computer, a laser collimation device and a laser signal streak tube imaging device, wherein:

[0025] The pulse signal trigger, controlled by a host computer, has multiple channels, which can be individually controlled by the host computer to control the frequency and delay of the trigger pulses in each channel. The trigger pulses generated by the different channels of the pulse signal generator are used to trigger the laser, the streak tube detector scanning circuit, and the CCD camera. Frequency matching of trigger pulses with different delays allows the streak tube detector to image at the optimal moment, and also controls the camera's exposure time to fully capture the laser pulse image information while avoiding over- or under-exposure. This also reduces laser interference with the camera.

[0026] The host computer uses a computer to control the pulse signal trigger, receive the image captured by the CCD camera, and perform processing and analysis such as centroid extraction on the image to obtain the centroid position of the image. By analyzing the offset of the centroid position in the image on the X-axis and Y-axis as the test device works over time, the offset of the laser beam as the test device works over time is obtained, thereby achieving the purpose of testing the stability of the streak tube detector.

[0027] The laser collimation device comprises a laser, an aperture, and a collimating lens assembly. The "aperture-collimating lens assembly-aperture" collimation structure removes stray light from the laser beam output by the laser and collimates the laser beam into a uniform, focused, parallel laser beam. The specific process for achieving the collimation effect is as follows: the laser generates laser light through a trigger pulse. The laser pulse first passes through the aperture, removing stray light at the edges and reducing unnecessary interference light, thus making the laser more pure. The collimating lens assembly then collimates the diverging laser beam into a parallel beam with virtually no change in propagation direction. Finally, the laser passes through a second aperture, which optimizes the beam's intensity distribution, ensuring a more uniform intensity across the cross-section of the laser beam entering the streak tube detector. Furthermore, the second aperture is closer to the streak tube detector, shortening the beam's propagation distance before entering the streak tube detector. This reduces the beam's divergence and enables more precise control of the beam's shape and size before entering the streak tube detector, reducing the interference of variations in the laser spot intensity distribution on the imaging effect.

[0028] The laser signal streak tube imaging device primarily consists of a streak tube detector and a CCD camera. Collimated laser light converges onto the streak tube detector's photocathode, generating photoelectrons that convert the optical signal into an electronic signal. The photoelectrons are accelerated and focused by a grid to form a beam. Deflection electrodes deflect the electron beam in time and space before it is emitted onto a fluorescent screen for imaging. The streak tube detector's fluorescent screen image is enhanced by a microchannel plate and coupled to the CCD camera's sensor array via an optical fiber taper. The CCD camera sensor then transmits the captured image data to a host computer.

[0029] The process of streak tube detector switching operating mode through scanning circuit is shown in Figure 2 The operation mode switching method needs to be described in combination with the process of streak tube imaging to streak image. The imaging process of the laser signal on the streak tube detector includes:

[0030] B1: When the laser light signal enters the streak tube detector, it is first received by the streak tube detector's photocathode. Induced by the light signal, the photocathode generates photoelectrons, completing the process of converting the light signal into an electronic signal.

[0031] B2: Photoelectrons emitted from the photocathode are focused and accelerated by the streak tube detector's grid, forming a photoelectron beam. The streak tube detector uses a control mechanism to focus and accelerate the photoelectrons into a beam.

[0032] B3: The photoelectron beam output by the focusing electrode is scanned and deflected by the streak tube detector's deflection electrodes. The deflection electric field controls the position of the photoelectrons as they exit the field, resulting in a linear spatial deflection with time of incidence. After exiting the field, the photoelectrons are directed toward the streak tube detector's phosphor screen, forming an image. This image is enhanced by the microchannel plate, and the CCD camera receives the enhanced image data and transmits it to the host computer for processing. Therefore, this section is a key area for controlling the deflection of the photoelectron beam, with the scanning circuit connected to both ends of the streak tube detector's deflection electrodes.

[0033] Interface A1 is the connection point where the streak tube detector provides voltage to the deflection electrodes. When the scanning circuit switch is connected to interface A1, voltage exists between the two deflection electrodes, and the streak tube detector is in dynamic operating mode. Interface A2 is the connection point that connects the streak tube detector to the ground wire. When the scanning circuit switch is connected to interface A2, the voltage between the two deflection electrodes is zero, and the streak tube detector is in static operating mode. Therefore, the operating mode of the streak tube detector can be changed by changing the interface to which the scanning circuit switch is connected.

[0034] The multiple trigger pulses in the present invention have frequency matching and different delays; according to the position of each device, the delay of the CCD camera is set to be greater than the delay of the laser, and the delay of the streak tube scanning circuit is slightly greater than the delay of the CCD camera.

[0035] Specific embodiment 2: This embodiment provides a method for testing the temporal stability of a streak tube lidar detector. The method uses a trigger pulse output by a pulse signal trigger to control the time delay of the laser, streak tube detector, and CCD camera; utilizes a collimating lens group as the laser collimation system; and passes the laser through an "aperture-collimating lens group-aperture" structure before entering the streak tube detector to collimate the laser into a high-quality, highly collimated parallel laser beam. Switches are designed in the scanning circuits at both ends of the streak tube detector to switch the streak tube detector's operating mode. The specific steps are as follows:

[0036] Step 1: Generate laser pulses: The upper computer controls the pulse signal trigger to input a trigger pulse to the laser to generate laser pulses;

[0037] Step 2: Use a laser collimation device to collimate the laser pulse: Before the laser pulse output by the laser enters the streak tube detector, the laser needs to be collimated. Therefore, a "diaphragm-collimating lens group-diaphragm" structure is designed and placed between the laser and the streak tube detector. The diaphragm that the laser passes through for the first time can remove the stray light and uneven light intensity distribution at the edge; the collimating lens group collimates the divergent laser signal into a parallel laser signal; the diaphragm that the laser passes through for the second time further optimizes the uniformity of the beam and reduces the impact caused by changes in the intensity distribution of the laser spot. Adjust the position of the lens group and the diaphragm so that the laser is accurately collimated before entering the streak tube detector, generating a high-quality, highly collimated parallel laser beam.

[0038] Step 3: Timing control of the streak tube detector scanning circuit and CCD camera: Use the host computer to manipulate other channels of the pulse signal trigger to input trigger pulses to the streak tube detector scanning circuit and CCD camera, respectively. The trigger pulse frequencies input to the laser, streak detector scanning circuit, and CCD camera are set to match, with different delays. Because the laser pulses output by the laser first pass through the streak detector before entering the CCD camera during the implementation of the present invention, the delay time of the trigger pulse input to the CCD camera is set to be longer than the delay time of the trigger pulse input to the laser, and the delay time of the trigger pulse input to the streak tube detector scanning circuit is set to be slightly longer than the delay time of the trigger pulse input to the CCD camera, to ensure that the CCD camera can relatively completely receive the image data transmitted by the streak tube detector.

[0039] Step 4: Image Data Acquisition and Processing: The streak image generated by the laser pulse passing through the streak tube detector is captured by a CCD camera, which then transmits the captured image data to a host computer. The host computer processes the captured image data using methods such as centroid extraction. The laser beam deflects over time during the test device's operation, thereby testing the streak tube's stability over time.

[0040] In the present invention, the streak tube detector has two working modes: a dynamic working mode and a static working mode. These two working modes can be switched by whether there is a voltage between the deflection electrodes controlled by the scanning circuit at both ends of the streak tube detector. In the dynamic mode, the streak tube detector can quickly respond to and scan the light signal, so the stability of the streak tube detector in different working modes is very important. The present invention adds a switch at one end of the scanning circuit and the other end is grounded. When the switch is connected to the positive pole of the power supply, there is a voltage between the deflection electrodes, and the operating mode of the streak tube detector can be switched from static to dynamic. Similarly, when the switch is connected to the ground wire at the other end of the scanning circuit, the voltage between the deflection electrodes is zero, and the operating mode of the streak tube detector can be switched from dynamic to static, thereby realizing the switching of the working mode of the streak tube detector.

Claims

1. A device for testing the temporal stability of a streak tube laser radar detector, characterized in that The device includes a pulse signal trigger, a host computer, a laser collimation device and a laser signal streak tube imaging device, wherein: The laser collimation device is composed of a laser and a collimation system. The laser beam generated by the laser is processed by the collimation system to form a high-quality, high-collimation parallel laser beam; The laser signal streak tube imaging device is composed of a streak tube detector and a CCD camera. The streak tube detector images the laser pulse into a streak image and switches the working mode through a scanning circuit. The CCD camera receives the streak image transmitted by the streak tube detector and transmits the collected image data to the host computer. The pulse signal trigger is used to provide trigger pulses, and provides trigger pulses to the laser, streak tube scanning circuit, and CCD camera through different channels; The host computer is used to manipulate the pulse signal trigger to control the frequency and delay of the trigger pulses output by different channels, receive the laser signal image data collected by the CCD camera and perform centroid extraction processing on the image data, and obtain the offset of the laser beam as the test device works over time by analyzing the offset of the centroid position in the image on the X-axis and Y-axis as the test device works over time, thereby testing the stability of the streak tube detector over time.

2. The device for testing the temporal stability of a streak tube laser radar detector according to claim 1, characterized in that The collimation system is an "aperture-collimation lens group-aperture" collimation structure consisting of a first aperture, a collimating lens group, and a second aperture. The laser beam generated by the trigger pulse of the laser first passes through the first aperture to remove stray light at the edge; then the divergent laser beam is collimated into a parallel beam by the collimating lens group; and then passes through the second aperture to optimize the light intensity distribution of the beam.

3. The device for testing the temporal stability of a streak tube laser radar detector according to claim 2, characterized in that The second aperture is close to the streak tube detector.

4. The device for testing the temporal stability of a streak tube laser radar detector according to claim 1, characterized in that The time delay of the CCD camera is greater than the time delay of the laser, and the time delay of the streak tube scanning circuit is greater than the time delay of the CCD camera.

5. A method for testing the temporal stability of a streak tube laser radar detector using the device according to any one of claims 1 to 4, characterized in that The method comprises the following steps: Step 1: Generate laser pulses: The upper computer controls the pulse signal trigger to input a trigger pulse to the laser in the laser alignment system to generate laser pulses; Step 2: Use the collimation system to collimate the laser pulse: Use the collimation system in the laser collimation device to collimate the laser beam output from the laser to ensure that it has good directionality and parallelism before entering the streak tube detector; Step 3: Timing control of the streak tube detector scanning circuit and CCD camera: Use the host computer to manipulate the pulse signal trigger to input trigger pulses to the streak tube detector scanning circuit and CCD camera respectively, and accurately set the trigger pulse frequencies input to the laser, streak tube detector scanning circuit and CCD camera to match each other. At the same time, different trigger pulse delays are set according to imaging requirements; Step 4: Acquisition of laser pulse fringe image: The trigger pulse provided by the pulse signal trigger enables the laser collimation device and the laser signal streak tube imaging device to work normally. The collimated laser beam passes through the laser signal streak tube imaging device and is output as a two-dimensional fringe image. The light spots in the fringe image correspond one-to-one to the laser pulse information. Step 5. Laser pulse streak image processing: The laser pulse streak image captured by the CCD camera is transmitted to the host computer for centroid extraction processing. The stability of the streak tube detector over time is judged based on the offset of the center of mass position of the light spot as the test device works over time. The stability of the streak tube detector under different working modes is tested through the design of the scanning circuit.

6. The method for testing the temporal stability of a streak tube laser radar detector according to claim 5, characterized in that In step five, the method for switching the working mode of the streak tube detector includes: adding a scanning circuit at both ends of the deflection electrodes of the streak tube detector, designing a switch at one end of the scanning circuit and grounding the other end; when the switch is connected to the positive pole of the power supply, a deflection voltage exists between the deflection electrodes, and the streak tube detector switches to the dynamic mode; when the switch is connected to the ground wire, the voltage between the deflection electrodes is zero, and it switches to the static mode.

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