Multi-camera synchronization measurement method and device based on nanosecond LED water light

Abstract

The present invention relates to a multi-camera synchronization measurement device based on nanosecond LED running lights, comprising a timing logic unit, a running light module, a digital display array and a computer. The running light module comprises a plurality of LED lamp beads and a digital display array. The timing logic unit outputs a control signal to the running light module in parallel through a plurality of IO ports. Each LED lamp bead has a nanosecond rise response time. If the response time of the LED lamp bead is less than T nanoseconds, the next adjacent lamp bead can be illuminated within a time interval of T nanoseconds, and the previous illuminated lamp bead keeps the luminous state. The numerical value displayed by the digital display array indicates the number of times all the LED lamp beads in the running light module have been illuminated. The computer is used for analyzing and comparing the images taken by a plurality of high-speed cameras to realize the synchronization measurement between the high-speed cameras to be tested.

Description

Technical Field

[0001] The present invention belongs to the field of precision measurement technology and optical engineering, and in particular to a method and device for measuring the synchronization of multiple cameras of a nanosecond-level LED running water lamp. Background Art

[0002] In recent years, with the continuous improvement of hardware computing power, computer vision technology has also developed by leaps and bounds. Computer vision technology has been widely used in various industrial fields, improving production efficiency and reducing labor input costs. Among them, many application scenarios have been gradually replaced by automated and intelligent industrial camera detection from the original manual detection, and are developing towards high-speed, high-precision, and large-viewing-angle detection. This requires multiple cameras to work together according to certain rules and collect images synchronously. When the target to be measured is a high-speed object, the camera needs to have a high frame rate, and the synchronization of multiple high-frame-rate cameras will affect the final detection accuracy. At present, in low-speed scenarios, when the camera obtains the same trigger signal, it will be assumed that the camera simultaneously collects images at the same time, ignoring the differences in the intermediate hardware response characteristics and the time error caused by different conversion methods of the trigger signal. Therefore, in the multi-camera high-speed acquisition scenario, especially when different types of trigger signals or different types of cameras are used, the synchronization verification work between multiple cameras is of great practical significance.

[0003] The commonly used method for verifying the synchronization of area array cameras is relatively simple and effective. It usually involves placing a millisecond timer in the common field of view of multiple cameras, and then allowing the cameras to receive synchronized trigger signals. The synchronization measurement of the area array cameras can be completed by directly observing the time difference of the timers in the images captured by different cameras.

[0004] However, the above method of placing a timer in the common field of view of multiple cameras will be affected by the refresh rate of the timer display device, and the refresh rate of a conventional display device is only about 100, so this method can only be used to verify the synchronization of multiple cameras at low speeds, and it is difficult to guarantee that the theoretically accurate image can be obtained during high-speed acquisition. At present, there is no universal measurement method and corresponding device for verifying the synchronization between area array high-speed cameras. Summary of the invention

[0005] The purpose of the present invention is to provide a multi-camera synchronization measurement device and measurement method that can realize accurate measurement of synchronization of multi-camera acquisition. The present invention realizes nanosecond-level LED water light based on sequential logic circuit, compares and analyzes the nanosecond-level timestamps obtained by different cameras to be tested, and realizes the image acquisition synchronization test between multiple cameras, which can eliminate the influence of insufficient refresh rate of conventional digital display devices on synchronization measurement and improve measurement accuracy and range. The technical solution adopted is:

[0006] A multi-camera synchronization measurement device based on nanosecond LED running lights, comprising a timing logic unit, a running light module and a computer, wherein the timing logic unit is connected to the running light module, the running light module comprises a plurality of LED lamp beads and a digital display array, the timing logic unit outputs a control signal in parallel to the running light module through a plurality of IO ports, the control signal drives each LED lamp bead in the running light module, each LED lamp bead has a nanosecond rise response time, assuming that the response time of the LED lamp bead is less than T nanoseconds, and it emits light within T nanoseconds of the arrival of an electrical signal, the timing logic unit generates nanosecond precise timing through timing logic control, and can realize the light emission of the next adjacent lamp bead within a time interval of T nanoseconds, and the previously emitted lamp bead keeps the light emission state;

[0007] The value displayed by the digital display array indicates the number of times all LED lamp beads in the water lamp module have been lit;

[0008] The images captured by the high-speed camera include the LED lamp beads and digital display array in the water light module;

[0009] The computer is used to analyze and compare the images taken by multiple high-speed cameras, convert the number of luminous LED lamp beads in the flowing light module and the numerical value of the digital display array in the images taken by different high-speed cameras into corresponding time difference values, so as to obtain the nanometer time difference of the actual collection moments of different high-speed cameras, compare and analyze the luminous conditions of the LED lamp beads in the flowing light module obtained by the high-speed camera to be tested and the numerical value of the digital display array, and realize the synchronization measurement between the high-speed cameras to be tested.

[0010] Furthermore, the timing logic unit changes the crystal oscillator clock signal by clock division, and then controls the logic circuit by the divided clock signal.

[0011] Select the working state of the running light module. The timing logic control method of the running light module is:

[0012] a. Set the crystal oscillator clock signal of the timing logic unit; divide the crystal oscillator clock signal by the counter register;

[0013] b. The running light state selection register stores decimal serial numbers representing different lighting conditions of the running light module. The output register of the running light state selection register provides a selection signal for the lighting state of the running light module to control the on and off state of the LED lamp beads in the running light module. The running light state register is a fixed signal mode that has been set. The multiple different binary values ​​in the running light state register represent different lighting states of the running light module. The adjacent latter working state always lights up one more LED lamp bead than the previous working state. The time interval between two adjacent working states is the time represented by the clock after the crystal oscillator clock signal is divided. The time represented by a single clock signal after the division is T nanoseconds. In each cycle of the running light module, the lights that have been lit in the previous sequence of the running light LED lamp bead sequence are kept from being extinguished. The last running light state signal in the running light state register represents the state in which all the running light LEDs are lit.

[0014] c. The system reset signal is valid when it is 0, that is, it is valid when it is at a low level; the reset signal input terminal of the register is valid when it is , that is, it is valid when it is at a high level; the system reset signal is connected to the reset signal input terminals of the counter register and the running light state selection register to control the reset operation of the counter register and the running light state selection register; when the system reset signal acts on the counter register, the system reset signal is inverted and the lower two bits of the counter register output signal pass through the AND gate, and then the AND gate output signal passes through the OR gate and is output to the reset signal input terminal of the counter register; when the system reset signal acts on the running light state selection register, the system reset signal is directly connected to the reset signal input terminal of the running light state selection register When the system reset signal is valid, the reset zero state of the running light state selection register is maintained. At this time, the running light state selection register will not receive the result of the adder at the input end of the state selection register, which is equivalent to the adder at the input end of the state selection register failing, waiting for the failure of the system reset signal; when the system reset signal fails, the adder at the input end of the state selection register starts to work, and outputs the signal to the output register of the running light state selection register. The output signal is the final LED state selection signal. The LED state selection signal selects and outputs the state signal of the running light module in the running light state register through the multiplexer, and is displayed on the luminous state of the running light module;

[0015] The present invention also provides a multi-camera synchronization measurement method implemented by the above device, comprising the following steps:

[0016] (1) Place the water light module in the common field of view of multiple high-speed cameras, and adjust the focus of the high-speed cameras to make the water light module clearly imaged in the field of view;

[0017] (2) The synchronous trigger signal of the nanosecond synchronous trigger is transmitted to the high-speed camera through the trigger signal transmission line. Under the control of the synchronous trigger signal, multiple high-speed cameras synchronously shoot the LED water light module of the synchronous test device, and the images shot by each high-speed camera are transmitted to the computer;

[0018] (3) The computer analyzes and compares the images taken by multiple high-speed cameras, converts the number of LED lamp beads in the water light module and the numerical value of the digital display array in the images taken by different high-speed cameras into the corresponding time difference, and then obtains the nanometer time difference of the actual acquisition time of different high-speed cameras. The light emission of the LED lamp beads in the water light module taken by the high-speed camera to be tested and the numerical value of the digital display array are compared and analyzed to achieve synchronization measurement between the high-speed cameras to be tested.

[0019] Furthermore, in step (3), the method for obtaining the nanometer-level time difference of the actual acquisition moments of different high-speed cameras is as follows:

[0020] a. After the positions of the high-speed camera and the running light module are fixed, before lighting the running light module, trigger the high-speed camera to take a picture of the non-luminous running light module as a reference image. This allows the running light module to work normally. The nanosecond synchronization trigger transmits the synchronization trigger signal to the external trigger signal receiving end of multiple high-speed cameras, so that each high-speed camera that receives the external trigger signal can shoot synchronously. Obtain the luminous state of the LED lamp beads and the value of the digital display array in the running light module images obtained by synchronous acquisition of different high-speed cameras, and compare them with the reference image of the running light module that was not energized before, and obtain the number of LED lamp beads that emit light and the value of the digital display array in the corresponding acquired image.

[0021] b. Calculate the nanosecond timestamp of the high-speed camera acquisition moment. The nanosecond timestamp refers to the cumulative result of the time interval between the LED lamp beads lighting up. n is the total number of LED lamp beads in the running light module. If the difference in the number of LED lamp beads lit up in the running light module acquired by different high-speed cameras is N, and the digital difference of the digital display array is k, then the synchronous acquisition time difference of different high-speed cameras is accumulated from 0 nanoseconds to T*k*n+T*(N+1) nanoseconds; as the value of the digital display array increases, the corresponding time measurement interval also increases.

[0022] The beneficial effects of the present invention are as follows:

[0023] (1) The present invention provides a nanosecond-level LED water light multi-camera synchronization measurement device based on a sequential logic circuit, which has flexible layout and is suitable for precise measurement of camera acquisition synchronization under different fields of view and angles, and has a wide range of application scenarios;

[0024] (2) The present invention provides a nanosecond-level LED water light multi-camera synchronization measurement method based on a sequential logic circuit, which compares and analyzes the nanosecond-level timestamps obtained by different cameras to be tested, realizes the image acquisition synchronization measurement between multiple cameras, and is suitable for accurate measurement of acquisition synchronization between various high-speed cameras;

[0025] (3) The present invention provides a method for measuring the synchronization of multiple cameras using a flowing light, thereby eliminating the influence of insufficient refresh rate of ordinary digital display devices on synchronization measurement and improving measurement accuracy and range. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the multi-camera synchronous testing principle of the flowing water lamp of the present invention.

[0027] Figure 2 This is a schematic diagram of the FPGA timing logic control principle of the running water lamp of the present invention.

[0028] Figure 1 In the middle: 1 is the power supply; 2 is the timing logic unit; 3 is the running light module; 4 is the high-speed camera; 5 is the nanosecond synchronization trigger; 6 is the network switch; 7 is the PC storage unit.

[0029] Figure 2 In it: 8 is the system reset signal; 9 is the crystal oscillator clock signal; 10 is the counter register; 11 is the output signal of the counter register; 12 is the adder at the input end of the counter register; 13 is the AND gate; 14 is the OR gate; 15 is the reset signal end of the counter register; 16 is the output signal of the AND gate; 17 is the adder at the input end of the state selection register; 18 is the running light state selection register; 19 is the output register of the running light state selection register; 20 is the running light state register; 21 is the multiplexer. DETAILED DESCRIPTION

[0030] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. The best embodiment consists of the following parts:

[0031] The first part provides a nanosecond level LED water lamp multi-camera synchronization measurement device based on sequential logic circuit;

[0032] The nanosecond-level LED running light multi-camera synchronization measurement device based on sequential logic circuit of the present invention comprises a power supply 1, a sequential logic unit 2, and a running light module 3. The sequential logic unit of this embodiment is implemented by using an FPGA development board. The timing logic unit 2 is connected to the running light module 3, and the power supply 1 supplies power to the timing logic unit 2 through the power transmission line. The running light module 3 includes a plurality of LED lamp beads and a digital display array. The timing logic unit 2 outputs the control signal in parallel to the running light module 3 through a plurality of IO ports. The control signal drives each LED lamp bead of the running light module 3. Each LED lamp bead has a rise response time of less than 30 nanoseconds and emits light within 30 nanoseconds of the arrival of the electrical signal. The timing logic unit generates nanosecond-level precise timing through timing logic control, and can realize the illumination of the next adjacent lamp bead within a time interval of 30 nanoseconds. The previously illuminated lamp bead remains in the illuminating state, avoiding the influence of the long extinguishing response time of the LED lamp bead on the illumination of the entire running light. The value displayed by the digital display array indicates the number of times all the LED lamp beads in the running light module have been lit, and the synchronization test of the LED running light module over a longer time range can be realized.

[0033] The second part provides a multi-camera synchronization measurement method for the measurement device structure of the first part;

[0034] like Figure 1 , Schematic diagram of synchronous measurement of multiple cameras of a running light. The power supply 1, the timing logic unit 2 and the running light module 3 form a synchronous test device. The entire synchronous test device is placed in the common field of view of multiple high-speed cameras 4, and the focus of the high-speed camera 4 is adjusted to make it clearly imaged in the field of view. The synchronous trigger signal of the nanosecond synchronous trigger 5 is transmitted to the high-speed camera 4. Under the control of the multi-channel synchronous trigger signal, the multiple high-speed cameras 4 synchronously shoot the LED running light module 3 of the synchronous test device, and at the same time transmit the captured image to the network switch 6 through the 10 Gigabit network cable, and then the network switch 6 transmits it to the PC storage unit 7 through the 10 Gigabit network cable. The captured images of the multiple high-speed cameras 4 in the PC storage unit 7 are analyzed and compared, and the number of LED lamp beads in the running light module 3 captured by different high-speed cameras 4 is converted into the corresponding time difference value, so that the nanometer time difference of the actual acquisition time of different high-speed cameras 4 can be obtained, and the luminous conditions of the LED lamp beads in the running light module 3 captured by the high-speed camera 4 to be tested are compared and analyzed to achieve the synchronization measurement between the high-speed cameras 4 to be tested.

[0035] The multi-camera synchronization measurement includes the synchronous shooting and acquisition of nanosecond-level LED water lights and the calculation of camera acquisition timestamps, which is implemented in the following steps:

[0036] a. After the positions of the high-speed camera 4 and the running light module 3 are fixed, before lighting the running light module 3, first trigger the high-speed camera 4 to take a picture of the non-luminous running light module 3 as a reference image. Then turn on the power of the synchronous test device to make the running light module 3 work normally. The nanosecond synchronous trigger 5 transmits the synchronous trigger signal to the external trigger signal receiving end of multiple high-speed cameras 4 through the trigger signal transmission line, so that each high-speed camera 4 that receives the external trigger signal performs synchronous shooting. Obtain the luminous state of the LED lamp beads and the value of the digital display array in the images of the running light module 3 synchronously collected by different high-speed cameras 4, and compare them with the reference image of the running light module 3 that is not energized before, to obtain the number of LED lamp beads that emit light and the value of the digital display array corresponding to the collected image.

[0037] b. Calculate the timestamp of the time collected by the high-speed camera 4. The nanosecond timestamp is the cumulative result of the time interval of the LED lamp beads lighting up. It is a problem of different time intervals represented by different numbers of emitting LED lamp beads. n is the total number of LED lamp beads in the water lamp module 3. If the difference in the number of emitting LED lamp beads displayed in the water lamp module 3 collected by different high-speed cameras 4 is N, and the digital difference of the digital display array is k, the nanosecond timestamp of the synchronization delay time is accumulated from 0 nanoseconds to 30*k*(n+1)+30*(N+1) nanoseconds. In addition, as the value of the digital display array increases, the corresponding time measurement interval is also increasing.

[0038] The third part provides a timing logic control method for the water lamp module in the first part;

[0039] The timing logic unit changes the crystal oscillator clock signal through clock frequency division, and then controls the logic circuit to select the working state of the running light module through the divided clock signal, such as Figure 2 , the schematic diagram of the timing logic control of the water lamp. The timing logic control method is implemented in the following steps:

[0040] a. Set the crystal oscillator clock signal 9 of the sequential logic unit 2 to 100 MHz. The crystal oscillator clock signal 9 is divided into three frequencies by the counter register 10. The counter register 10 is composed of two binary numbers timer_cnt[0] and timer_cnt[1]. Only when timer_cnt[0]=0 and timer_cnt[1]=1, the output signal 16 through the AND gate 13 is high level 1. In other cases, the output signal 16 through the AND gate 13 is low level 0. Due to the addition operation of the adder 12, the initial value of the counter register 10 is 01, and when the value is 10, the counter register 10 is reset to zero and returns to the 00 state, that is, the counter register 10 maintains the cycle value of 01->10->00->01->10..., and repeats this process to complete the three-frequency operation of the counter register 10 on the crystal oscillator clock signal 9.

[0041] b. The running light state selection register 18 stores decimal serial numbers representing different lighting conditions of the running light module 3. The output register 19 of the running light state selection register provides a selection signal for the lighting state of the running light module 3 to control the on and off state of the LED lamp beads in the running light module 3. The running light state register 20 is a fixed signal mode that has been set. The multi-bit different binary values ​​in the running light state register 20 represent different lighting states of the running light module 3. The adjacent latter working state always lights up one more LED lamp bead than the previous working state. The time interval between two adjacent working states is the time represented by the clock after the crystal oscillator clock signal 9 is divided by frequency, that is, when the crystal oscillator clock signal 9 is 100M, the time represented by the single clock signal after the division is 30 nanoseconds when the counter register 10 divides the frequency by three. In order to eliminate the influence of the response time of LED lamp bead turning off, in each cycle of the running light module 3, the lights that have been lit in the previous sequence of the running light LED lamp bead sequence are kept from being turned off, that is, the last running light state signal in the running light state register 20 represents the state that all the running light LEDs are lit.

[0042] c. The system reset signal 8 is valid when it is 0, that is, it is valid when it is at a low level. The reset signal input end of the register is valid when it is 1, that is, it is valid when it is at a high level. The system reset signal 8 is connected to the reset signal input end of the counter register 10 and the running light state selection register 18 to control the reset operation of the counter register 10 and the running light state selection register 18. When the system reset signal 8 acts on the counter register 10, the system reset signal 8 is inverted and the lower two bits of the output signal of the counter register 10 are output to the reset signal input end of the counter register 10 through the AND gate output signal 16 after the AND gate 13 through the OR gate 14; when the system reset signal 8 acts on the running light state selection register 18, the system reset signal 8 is directly connected to the reset signal input port of the running light state selection register 18. When the system reset signal 8 is valid, the reset zero state of the running light state selection register 18 is maintained. At this time, the running light state selection register 18 will not receive the result of the adder 17 at the input end of the state selection register, which is equivalent to the adder 17 at the input end of the state selection register failing, waiting for the failure of the system reset signal 8. When the system reset signal 8 fails, the adder 21 at the input end of the state selection register starts working and outputs the signal to the output register of the running light state selection register. The output signal is the final LED state selection signal. The LED state selection signal selects and outputs the state signal of the running light module 3 in the running light state register 20 through the multiplexer 21, thereby changing the working state of the running light module 3.

Claims

1. A multi-camera synchronization measurement device based on nanosecond LED running lights, comprising a timing logic unit, a running light module and a computer, wherein the timing logic unit is connected to the running light module, the running light module comprises a plurality of LED lamp beads and a digital display array, the timing logic unit outputs control signals in parallel to the running light module through a plurality of IO ports, the control signal drives each LED lamp bead in the running light module, each LED lamp bead has a nanosecond rise response time, assuming that the response time of the LED lamp bead is less than T nanoseconds, and the LED lamp bead emits light within T nanoseconds of the arrival of the electrical signal, the timing logic unit generates nanosecond precise timing through timing logic control, and can realize the light emission of the next adjacent lamp bead within the time interval of T nanoseconds, and the previously emitted lamp bead keeps the light emission state; The value displayed by the digital display array indicates the number of times all LED lamp beads in the water lamp module have been lit; The images captured by the high-speed camera include the LED lamp beads and digital display array in the water light module; The computer is used to analyze and compare the images taken by multiple high-speed cameras, convert the number of LED lamp beads in the water light module in the images taken by different high-speed cameras and the value of the digital display array into the corresponding time difference, so as to obtain the nanometer time difference of the actual acquisition time of different high-speed cameras, compare and analyze the light emission of the LED lamp beads in the water light module taken by the high-speed camera to be tested and the value of the digital display array, and realize the synchronization measurement between the high-speed cameras to be tested; in, The timing logic unit changes the crystal oscillator clock signal by clock division, and then controls the logic circuit to select the working state of the running light module through the divided clock signal. The timing logic control method of the running light module is: a. Set the crystal oscillator clock signal of the timing logic unit; divide the crystal oscillator clock signal by the counter register; b. The running light state selection register stores decimal serial numbers representing different lighting conditions of the running light module. The output register of the running light state selection register provides a selection signal for the lighting state of the running light module to control the on and off state of the LED lamp beads in the running light module. The running light state register is a fixed signal mode that has been set. The multiple different binary values ​​in the running light state register represent different lighting states of the running light module. The adjacent latter working state always lights up one more LED lamp bead than the previous working state. The time interval between two adjacent working states is the time represented by the clock after the crystal oscillator clock signal is divided. The time represented by a single clock signal after the division is T nanoseconds. In each cycle of the running light module, the lights that have been lit in the previous sequence of the running light LED lamp bead sequence are kept from being extinguished. The last running light state signal in the running light state register represents the state in which all the running light LEDs are lit. c. The system reset signal is valid when it is 0, that is, it is valid when it is at a low level; the reset signal input terminal of the register is valid when it is , that is, it is valid when it is at a high level; the system reset signal is connected to the reset signal input terminals of the counter register and the running light state selection register to control the reset operation of the counter register and the running light state selection register; when the system reset signal acts on the counter register, the system reset signal is inverted and the lower two bits of the counter register output signal pass through the AND gate, and then the AND gate output signal passes through the OR gate and is output to the reset signal input terminal of the counter register; when the system reset signal acts on the running light state selection register, the system reset signal is directly connected to the reset signal input terminal of the running light state selection register The LED state selection register is connected to the LED port. When the system reset signal is valid, the reset zero state of the running light state selection register is maintained. At this time, the running light state selection register will not receive the result of the adder at the input end of the state selection register, which is equivalent to the adder at the input end of the state selection register failing, waiting for the failure of the system reset signal; when the system reset signal fails, the adder at the input end of the state selection register starts to work and outputs the signal to the output register of the running light state selection register. The output signal is the final LED state selection signal. The LED state selection signal selects and outputs the state signal of the running light module in the running light state register through the multiplexer, and is displayed on the luminous state of the running light module.

2. A method for measuring the synchronization of multiple cameras implemented by the device of claim 1, comprising the following steps: (1) Place the water light module in the common field of view of multiple high-speed cameras and adjust the focus of the high-speed cameras to make the water light module clearly imaged in the field of view; (2) The synchronous trigger signal of the nanosecond synchronous trigger is transmitted to the high-speed camera through the trigger signal transmission line. Under the control of the synchronous trigger signal, multiple high-speed cameras synchronously shoot the LED water light module of the synchronous test device, and the images shot by each high-speed camera are transmitted to the computer; (3) The computer analyzes and compares the images taken by multiple high-speed cameras, and converts the number of LED lamp beads in the water light module and the numerical value of the digital display array in the images taken by different high-speed cameras into the corresponding time difference value, so as to obtain the nanometer time difference of the actual acquisition moment of different high-speed cameras. The light emission of the LED lamp beads in the water light module taken by the high-speed camera to be tested and the numerical value of the digital display array are compared and analyzed to achieve the synchronization measurement between the high-speed cameras to be tested.

3. The multi-camera synchronization measurement method according to claim 2, characterized in that: In step (3), the method for obtaining the nanometer time difference of the actual acquisition time of different high-speed cameras is as follows: a. After the positions of the high-speed camera and the running light module are fixed, before lighting the running light module, the high-speed camera is first triggered to take a picture of the non-luminous running light module as a reference image; the running light module is made to work normally; the nanosecond synchronization trigger transmits the synchronization trigger signal to the external trigger signal receiving end of multiple high-speed cameras, so that each high-speed camera receiving the external trigger signal performs synchronous shooting; the light-emitting state of the LED lamp beads and the value of the digital display array in the running light module images synchronously acquired by different high-speed cameras are obtained, and compared with the reference image of the running light module not energized before, and the number of LED lamp beads emitting and the value of the digital display array corresponding to the acquired image are obtained; b. Calculate the nanosecond timestamp of the high-speed camera acquisition moment. The nanosecond timestamp refers to the cumulative result of the time interval between the LED lamp beads lighting up. n is the total number of LED lamp beads in the running light module. If the difference in the number of LED lamp beads lit up in the running light module acquired by different high-speed cameras is N, and the digital difference of the digital display array is k, then the synchronous acquisition time difference of different high-speed cameras is accumulated from 0 nanoseconds to T*k*n +T*(N+1) nanoseconds; as the value of the digital display array increases, the corresponding time measurement interval also increases.

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