System and method for realizing streak camera image flat field correction under working scanning speed based on pulse time-varying light source

Abstract

The invention discloses a streak camera image flat field correction system and method based on a pulse time-varying light source under a working scanning speed, and solves the problems of inaccurate response uniformity and high realization difficulty of an image flat field corrected by an existing method. The device specifically comprises a signal source, a pulse time-varying light source, a monitoring photoelectric detector, an oscilloscope and a series of attenuation slices with different transmittances, an A output channel of the signal source is connected with the pulse time-varying light source, a B output channel of the signal source is connected with the streak camera, and a C output channel of the signal source is connected with a first input end of the oscilloscope; the emergent end of the pulse time-varying light source corresponds to the incident end of the streak camera; the detection end of the monitoring photoelectric detector corresponds to the pulse light emitted by the pulse time-varying light source, and the output end of the monitoring photoelectric detector is connected with the second input end of the oscilloscope; a series of attenuation slices with different transmittances are used for being arranged at the emergent end of the pulse time-varying light source in a switching mode so as to attenuate the intensity of emergent pulse light of the pulse time-varying light source to different degrees.

Description

Technical Field

[0001] The present invention relates to a flat field correction system and method for streak camera images, and more particularly to a flat field correction system and method for streak camera images at the working sweep speed based on a pulse time-varying light source. Background Art

[0002] A streak camera is an ultrafast optoelectronic recording device, which consists of a slit, a relay lens, a streak tube, an image intensifier, and a digital camera. The slit is thin and long, and only the light within the slit region can enter the streak camera. The relay lens images the slit on the photocathode of the streak tube. When the streak camera is working, the light incident on the photocathode of the streak tube through the slit is converted into photoelectrons. The photoelectrons are distributed in a long strip shape, consistent with the shape of the slit. Under the action of the electron optical system of the streak tube, the photoelectrons are accelerated and imaged on the fluorescent screen at the rear end of the streak tube. During the signal incidence process, the photoelectrons pass through the deflection plates in the streak tube, and a voltage varying with time is applied to the deflection plates to deflect the photoelectrons passing through at different times to different positions on the fluorescent screen. The signal intensity at different positions represents the signal intensity at different times. The photoelectrons are converted into visible light by the fluorescent screen and recorded by the digital camera. Since the electron deflection speed can be very fast, the streak camera is an instrument with high time resolution. The fastest time resolution of the streak camera in the world can reach 200 femtoseconds.

[0003] The output data of the streak camera is a digital image, that is, a two-dimensional array. One dimension represents the time dimension, and the other dimension represents the space dimension. The value of each element in the array is the gray value of the pixel at the corresponding position, indicating the actual gray value output by the streak camera at the corresponding moment in the time dimension and the corresponding position in the space dimension of the pixel. The gray values output by each pixel of the streak camera are easily affected by various factors, resulting in uneven flat field response, which is mainly related to the uneven response of the devices on the signal formation link of the streak camera, such as uneven photocathode response, uneven fluorescent screen response of the streak tube, uneven image intensifier response, and uneven digital camera response, etc. In order to obtain more accurate recorded data, flat field correction of the streak camera images is required.

[0004] The calibration method for spatial response uniformity reported in the literature (Michael R. Charest, Jr., Peter Torres III, Christopher T. Silbernagel, Daniel H. Ralanter, A self - calibrating multichannel streak camera for inertial confinement fusion applications, Review of Scientific Instruments, 2002, 73(7), 2606 / 10) is to set the streak camera at an extremely slow scanning speed (1 second / screen), use a spatially uniform constant - current light source as the input, and use the image recorded by the streak camera as the calibration benchmark for spatial response uniformity. However, when the streak camera actually works, the scanning speed is much faster (nanoseconds / screen - microseconds / screen), and the scanning non - linearity will also cause non - uniform flat - field response. Therefore, the slow - scan - speed situation cannot represent the spatial response non - uniformity when the streak camera is actually working, and long - time light irradiation will also damage the device. Summary of the Invention

[0005] In order to solve the technical problems that the flat - field response uniformity of the calibrated image by the existing method is inaccurate, the implementation difficulty is large, and the device is damaged by long - time light irradiation during slow - scan calibration, the present invention provides a system and method for flat - field calibration of a streak - camera image at the working scan speed based on a pulsed time - varying light source.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A system for flat - field calibration of a streak - camera image at the working scan speed based on a pulsed time - varying light source, characterized in that it includes a signal source, a pulsed time - varying light source, a monitoring photodetector, an oscilloscope, and a series of attenuation sheets with different transmittances;

[0008] The A output channel of the signal source is connected to the pulsed time - varying light source, its B output channel is connected to the streak camera, and its C output channel is connected to the first input terminal of the oscilloscope; the streak camera is used to obtain the target image to be calibrated;

[0009] The output end of the pulsed time - varying light source corresponds to the input end of the streak camera, and is used to emit spatially uniform pulsed light to the streak camera, and its light - emitting duration is longer than the scan range of the streak camera;

[0010] The detection end of the monitoring photodetector corresponds to the pulsed light emitted by the pulsed time - varying light source, and its output end is connected to the second input terminal of the oscilloscope;

[0011] The series of attenuation filters with different transmittances are used to be respectively arranged at the output end of the pulsed time-varying light source in a switching manner to attenuate the intensity of the pulsed light emitted therefrom to different degrees.

[0012] Further, the oscilloscope is a digital oscilloscope.

[0013] Further, the relative delay adjustment accuracy between the A output channel, B output channel, and C output channel of the signal source is on the order of nanoseconds.

[0014] A method for flat-field correction of streak camera images at the working sweep speed based on a pulsed time-varying light source, using the above-mentioned system for flat-field correction of streak camera images at the working sweep speed based on a pulsed time-varying light source, is characterized in that it includes the following steps:

[0015] Step 1: Set an attenuation filter at the output end of the pulsed time-varying light source, start the streak camera, and make the incident end of the streak camera face the output end of the pulsed light source;

[0016] Step 2: Send a light source trigger signal to the pulsed time-varying light source through the signal source, and send a first external trigger signal and a second external trigger signal with the same start time and the same pulse width to the streak camera and the oscilloscope respectively;

[0017] Step 3: When the pulsed time-varying light source receives the light source trigger signal, it emits pulsed light, and the pulsed light reaches the streak camera after being attenuated by the attenuation filter;

[0018] Step 4: The streak camera scans the attenuated pulsed light based on the first external trigger signal to obtain a corresponding optical pulse image;

[0019] At the same time, monitor the attenuated pulsed light by the photodetector, convert it into an electrical signal and send it to the oscilloscope, so that the oscilloscope obtains a first time-voltage waveform diagram;

[0020] At the same time, when the oscilloscope receives the second external trigger signal, it obtains a second time-voltage waveform diagram, and the start time of the second time-voltage waveform diagram is the start time of the streak camera for scanning;

[0021] Step 5: Taking the start time as the starting point, on the first time-voltage waveform diagram, frame out an excerpt time-voltage waveform diagram within the duration corresponding to the sweep range of the streak camera;

[0022] Step 6: Switch the attenuation filter, and repeat steps 2 - 5 each time switching, so as to obtain a plurality of excerpt time-voltage waveform diagrams and a plurality of optical pulse images;

[0023] Step 7: Select an optical pulse image corresponding to an attenuation sheet with any transmittance of M from the multiple optical pulse images obtained in Step 6, calculate the average gray value of any column of pixels on this optical pulse image as the ideal gray value of this column of pixels; then calculate the ratio K of this ideal gray value to the voltage value at the corresponding moment in the corresponding excerpt time-voltage waveform diagram of this column of pixels, multiply all the voltage values in the excerpt time-voltage waveform by K, and then read the voltage value at the corresponding moment of each column of pixels on the optical pulse image from the excerpt time-voltage waveform after being multiplied by K as the ideal gray value Q of each pixel in each column of pixels on the optical pulse image scanned by the streak camera when the transmittance of the attenuation sheet is M m ;

[0024] Step 8: Calculate the ideal gray value Q of each pixel in each column of pixels on the optical pulse image scanned by the streak camera corresponding to attenuation sheets with other transmittances n :

[0025] Q n =Q m ×N / M;

[0026] In the formula, N represents the transmittance of other attenuation sheets;

[0027] Step 9: Obtain the actual gray value of each pixel in each optical pulse image

[0028] Step 10: For each pixel of the image that the streak camera can obtain, plot corresponding coordinate points with the actual gray values corresponding to a series of attenuation sheets with different transmittances as the abscissa and the corresponding ideal gray values as the ordinate, and fit all the coordinate points into the correction curve of the streak camera to obtain the same number of correction curves as the number of pixels in each optical pulse image

[0029] Step 11: Obtain the to-be-corrected target image through the streak camera, obtain the actual gray value of each pixel on the to-be-corrected target image, obtain the ideal gray value corresponding to each pixel on each of the curves obtained in Step 10, and correct the actual gray value of the corresponding pixel in the to-be-corrected target image with the obtained ideal gray values to complete the flat-field correction of the image

[0030] Advantages of the present invention:

[0031] 1. The flat-field correction system and method of the streak camera based on a pulsed time-varying light source provided by the present invention has the sweep speed of the streak camera during flat-field correction being the actual working sweep speed, and the result is more accurate than that obtained by performing flat-field correction on the streak camera during the slow sweep process

[0032] 2. The light source used for flat-field correction of the streak camera at the working sweep speed in the present invention is a pulsed time-varying light source. Developing a pulsed non-time-varying light source suitable for flat-field correction of the streak camera is extremely difficult and is the main factor restricting flat-field correction of the streak camera at the working sweep speed. However, the use of a pulsed time-varying light source in the present invention greatly reduces the development difficulty.

[0033] 3. In the present invention, a monitoring photodetector is used to provide the form of the input optical pulse of the streak camera changing with time, thereby finally realizing flat-field correction. The method is simple and reliable.

[0034] 4. The present invention breaks through the light source factor restricting flat-field correction of the streak camera at the working sweep speed and greatly reduces the difficulty of flat-field correction of the streak camera at the working sweep speed.

[0035] 5. The present invention realizes flat-field correction of the streak camera at the working sweep speed. Each time a light pulse image is acquired, the irradiation time of the streak camera is about several microseconds to 1 microsecond. The light irradiation time of the photosensitive devices (photocathode, fluorescent screen, etc.) in the streak camera is one hundred-thousandth to one-millionth of that in the case of slow scanning (~second-level time length), greatly reducing the risk of damage to the photosensitive devices in the streak camera.

[0036] 6. When performing flat-field correction in the present invention, the output gray value of each pixel on the light pulse image of the streak camera is associated with the actual input light pulse intensity at the corresponding moment of the pixel. Since the size of the output signal of each pixel before correction is related to both the output non-uniformity and scanning non-linearity of the streak camera, after correction, both the output non-uniformity and scanning non-linearity of the streak camera are corrected, providing another method for scanning non-linearity correction of the streak camera. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a schematic structural diagram of an embodiment of a system for realizing flat-field correction of a streak camera image at the working sweep speed based on a pulsed time-varying light source according to the present invention;

[0038] Figure 2 is a schematic diagram of the relative position relationship between the trigger pulse and the light intensity curve of the streak camera in the embodiment of the present invention; among them, (a) is a schematic diagram of the relative time relationship between the second external trigger signal (square wave pulse) and the first time-voltage waveform; (b) is a schematic diagram of the time axis and space axis on the light pulse image acquired by the streak camera;

[0039] Figure 3 is a schematic diagram of the waveform of the intensity of the pulsed time-varying light source changing with time and the recording area of the streak camera in the embodiment of the present invention;

[0040] Figure 4 is a relationship curve diagram between the transmittance of the attenuation sheet and the signal size of the light pulse image of the streak camera in the embodiment of the present invention;

[0041] Figure 5 It is a schematic diagram of the correspondence between the actual signal (abscissa: actual gray level) and the ideal signal (ordinate: true light intensity) of a certain pixel in the embodiment of the present invention;

[0042] Figure 6 It is a graph of the measured and corrected LED emission curve of the streak camera in the embodiment of the present invention. Among them, (a) is the original image of the LED emission recorded by the streak camera and the change of the gray level of a certain row of pixels by column (the horizontal axis is the column ordinal number, and the vertical axis is the gray level of this row), and (b) is the image after correction by the streak camera and the change of the gray level of this row of pixels by column (the horizontal axis is the column ordinal number, and the vertical axis is the gray level of this row).

[0043] Reference numerals in the attached drawings: 1 - signal source, 2 - pulsed time-varying light source, 3 - monitoring photodetector, 4 - oscilloscope, 5 - streak camera. Specific embodiments

[0044] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0045] A streak camera image flat-field correction system based on a pulsed time-varying light source to achieve the working sweep speed provided by the embodiment of the present invention, as Figure 1 shown, includes a signal source 1, a pulsed time-varying light source 2, a monitoring photodetector 3, an oscilloscope 4, and a series of attenuation sheets with different transmittances; the oscilloscope 4 uses a digital oscilloscope.

[0046] The A output channel of the signal source 1 is connected to the pulsed time-varying light source 2, its B output channel is connected to the streak camera 5, and its C output channel is connected to the first input terminal of the oscilloscope 4; the streak camera 5 is used to acquire the target image to be corrected; the relative delay adjustment accuracy between the A output channel, B output channel, and C output channel of the signal source 1 is in the nanosecond range. The output end of the pulsed time-varying light source 2 corresponds to the input end of the streak camera 5, and is used to emit spatially uniform pulsed light to the streak camera 5, and its emission duration is greater than the sweep range of the streak camera 5; the detection end of the monitoring photodetector 3 corresponds to the pulsed light of the pulsed time-varying light source 2, and its output end is connected to the second input terminal of the oscilloscope 4; a series of attenuation sheets with different transmittances are used to be respectively arranged at the output end of the pulsed time-varying light source 2 in a switching manner to attenuate the intensity of the pulsed light emitted by it to different degrees.

[0047] Its correction method includes the following steps:

[0048] Step 1. In this embodiment, six kinds of attenuation sheets with transmittances of 10%, 20%, 30%, 40%, 50%, and 75% respectively are adopted. Together with the transmittance of 100% when no attenuation sheet is added, a total of seven different transmittances can be generated. Take one of the attenuation sheets (the transmittance is 100% when no attenuation sheet is added) and set it at the output end of the pulsed time-varying light source. The pulsed time-varying light source is a pulsed xenon lamp. The output is homogenized through an integrating sphere and a ground glass, and is expanded after a certain distance. The light intensity at the incident end of the streak camera 5 can be regarded as spatially uniform. Start the streak camera 5 so that the incident end of the streak camera 5 is opposite to the output end of the pulsed light source. The optical pulse half-width of the pulsed xenon lamp is 3 microseconds, and the sweep range of the streak camera 5 is 350 nanoseconds.

[0049] Step 2. The signal source channel A sends a light source trigger signal to the pulsed time-varying light source, and the signal source channels B and C send the first external trigger signal and the second external trigger signal with the same starting time and the same pulse width to the streak camera and the oscilloscope respectively. The monitoring photodetector detects the optical pulse, converts it into an electrical signal, and then sends it to the oscilloscope to be recorded and displayed. The relative time relationship between the second external trigger signal (square wave pulse) and the electrical signal converted by the monitoring photodetector on the oscilloscope is as Figure 2 shown in (a). The starting time of the second external trigger signal is the same as that of the first trigger signal for triggering the streak camera. Therefore, from Figure 2 (a), the interval during which the streak camera records the optical signal can be calculated. This interval is from t0 to t1, and the recording time length is L. At this time, on the optical pulse image output by the streak camera, the first column corresponds to the time t0, the last column corresponds to the time t1, and the recording length is L, as Figure 2 shown in (b). By adjusting the relative delay between the signal source channels A and B, the streak camera 5 records the signal near the peak value of the optical pulse intensity, as Figure 3 shown, and there is no pixel saturation in the optical pulse image output by the streak camera to be measured.

[0050] Step 3. When the pulsed time-varying light source, that is, the pulsed xenon lamp, receives the light source trigger signal, it emits pulsed light. The pulsed light reaches the streak camera after being attenuated by the attenuation sheet.

[0051] Step 4. The streak camera 5 scans the pulsed light attenuated (not attenuated when no attenuation sheet is added) based on the first external trigger signal to obtain the corresponding optical pulse image.

[0052] At the same time, the monitoring photodetector detects the pulsed light attenuated (not attenuated when no attenuation sheet is added) and converts it into an electrical signal and sends it to the oscilloscope, so that the oscilloscope obtains the first time-voltage waveform diagram.

[0053] Meanwhile, when the oscilloscope receives the second external trigger signal, a second time-voltage waveform diagram is obtained, and the starting time of the second time-voltage waveform diagram represents the starting moment of the streak camera for scanning;

[0054] Step 5: Starting from the starting moment, on the first time-voltage waveform diagram, select the excerpt time-voltage waveform diagram within the duration corresponding to the sweep range of the streak camera, as Figure 3 shown;

[0055] Step 6: Switch the attenuation sheet, and each time it is switched, repeat Steps 2 - 5 to obtain multiple excerpt time-voltage waveform diagrams and multiple optical pulse images; in this example, the transmittance of the attenuation sheet changes from 10% to 75%, and the transmittances are arranged at approximately equal intervals, and 6 kinds of transmittances can be generated, which are 10%, 20%, 30%, 40%, 50%, and 75% respectively. Adding the transmittance of 100% when no attenuation sheet is used, there are a total of 7 different transmittances. At different transmittances, the actual gray value of a certain pixel on the optical pulse image is as Figure 4 shown.

[0056] Step 7: Select the optical pulse image corresponding to the attenuation sheet with any transmittance of M from the multiple optical pulse images obtained in Step 6, calculate the average gray value of the pixels in any column on this optical pulse image as the ideal gray value of this column of pixels; then calculate the ratio K of this ideal gray value to the voltage value at the corresponding moment of this column of pixels in the corresponding excerpt time-voltage waveform diagram, multiply all the voltage values in the excerpt time-voltage waveform by K, and then read the voltage value at the corresponding moment of each column of pixels on the optical pulse image from the excerpt time-voltage waveform after being multiplied by K as the ideal gray value Q of each pixel in each column of pixels on the optical pulse image scanned by the streak camera when the transmittance of the attenuation sheet is M m . Taking a specific method at a certain transmittance as an example as follows:

[0057] Select the optical pulse image corresponding to the transmittance of 100%, denoted as S100. The optical pulse image consists of R rows and C columns of pixels, corresponding to the light intensity change of the pulsed time-varying light source within the time period from t0 to t1. Refer to Figure 2 (b), the first column corresponds to the moment t0, the second column corresponds to the moment t0+(t1 - t0) / (C - 1), the third column corresponds to the moment t0 + 2·(t1 - t0) / (C - 1), the mth column corresponds to the moment t0+(m - 1)·(t1 - t0) / (C - 1), and until the Cth column corresponds to the moment t0+(C - 1)·(t1 - t0) / (C - 1)=t1. Calculate the average gray value of the pixels in the last column of this optical pulse image, denoted as C100t1, as the ideal gray value of this column of pixels; the excerpt time-voltage waveform is denoted as V(t), t0≤t<t1, and the voltage value at the corresponding moment of the last column is V(t1), then the ratio K is calculated by the following formula:

[0058] K = C100t1 / V(t1)

[0059] Multiply all voltage values of the selected time - voltage waveform V(t) (t0 ≤ t < t1) by K, denoted as KV(t). The calculation method of KV(t) is as follows:

[0060] KV(t) = V(t)·K = V(t)·C100t1 / V(t1)

[0061] The ideal gray value Q of the pixels in the c - th (1 ≤ c ≤ C) column m is calculated by the following formula:

[0062] Q m = KV(t) = V(t0 + (c - 1)·(t1 - t0) / (C - 1))·C100t1 / V(t1)

[0063] Step 8: When calculating the streak camera for other attenuation filters with different transmittances, calculate the ideal gray value Q of each pixel in each column of pixels on the scanned optical pulse image n :

[0064] Q n = Q m × N / M;

[0065] In the formula, N represents the transmittance of other attenuation filters;

[0066] Step 9: Obtain the actual gray value of each pixel in each optical pulse image; in this example, the obtained optical pulse images are marked as S10, S20, S30, S40, S50, S75, S100, all composed of R rows and C columns of pixels, corresponding to the optical pulse images at transmittances of 10%, 20%, 30%, 40%, 50%, 75%, and 100% respectively. S10(r, c) is the actual gray value of the pixel at the r - th row and c - th column on the optical pulse image with a transmittance of 10%.

[0067] Step 10: For each pixel of the images that the streak camera can obtain, use the actual gray values corresponding to a series of attenuation filters with different transmittances as the abscissa and the corresponding ideal gray values as the ordinate to plot the corresponding coordinate points, and fit all the coordinate points into the calibration curve of the streak camera, obtaining the same number of calibration curves as the number of pixels in each optical pulse image; for example, to obtain the gray values of the pixel at the r - th row and c - th column at different transmittances, the abscissa is the sequence:

[0068] [S10(r, c) S20(r, c) S30(r, c) S40(r, c) S60(r, c) S75(r, c) S100(r, c)]

[0069] The ordinate is the sequence:

[0070] [Q 10 (c)Q 20 (c)Q 30 (c)Q 40 (c)Q 60 (c)Q 75 (c)Q 100 (c)]

[0071] Fit two sequences to obtain the calibration curve of the pixel in the r-th row and c-th column, as Figure 5 shown.

[0072] Use the above method to obtain the calibration curve of each pixel.

[0073] Step 11: Obtain the target image to be calibrated through a streak camera, obtain the actual gray value of each pixel on the target image to be calibrated, and obtain the ideal gray value corresponding to each pixel on each curve obtained in Step 10, and use the obtained ideal gray values to calibrate the actual gray values of the corresponding pixels in the target image to be calibrated, and complete the flat-field calibration of the image.

[0074] In this embodiment, the light emission of the LED under the excitation of a 100-ns square-wave voltage is used as the actual input. The original image of the LED light emission recorded by the streak camera is as Figure 6 shown in the upper part of (a) in. It can be clearly observed that the non-uniformity of the image along the time axis. Extract the gray value of a certain row of pixels changing by column and draw a curve, as Figure 6 shown in the lower part of (a) in. It can be observed that there are small fluctuations superimposed on the LED light emission waveform. This is the influence of the image non-uniformity on the signal recorded by the streak camera. According to the calibration curve of each pixel obtained in Step 11, perform image calibration on the streak camera to obtain the ideal gray value of each pixel on the streak camera image. The calibrated image is as Figure 6 shown in the upper part of (b) in. Continue to draw the gray value of this row of pixels changing by column, and it can be seen that the small fluctuations superimposed on the LED light emission waveform are greatly suppressed, and the image calibration of the streak camera has an obvious effect.

[0075] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claimed rights.

Claims

1. A fringe camera image flat-field correction system based on a pulsed time-varying light source to achieve flat-field correction at the working sweep speed, characterized in that: It includes a signal source (1), a pulsed time-varying light source (2), a monitoring photodetector (3), an oscilloscope (4), and a series of attenuation sheets with different transmittances; The A output channel of the signal source (1) is connected to the pulsed time-varying light source (2), its B output channel is connected to the streak camera (5), and its C output channel is connected to the first input terminal of the oscilloscope (4); the streak camera (5) is used to obtain the target image to be corrected; The output end of the pulsed time-varying light source (2) corresponds to the input end of the streak camera (5), and is used to emit spatially uniform pulsed light to the streak camera (5), and its emission duration is greater than the sweep range of the streak camera (5); The detection end of the monitoring photodetector (3) corresponds to the pulsed light emitted by the pulsed time-varying light source (2), and its output end is connected to the second input terminal of the oscilloscope (4); The series of attenuation sheets with different transmittances are used to be respectively arranged at the output end of the pulsed time-varying light source (2) by means of switching, so as to attenuate the intensity of the pulsed light emitted by it to different degrees.

2. The flat-field correction system for streak camera images at the working sweep speed based on a pulsed time-varying light source according to claim 1, wherein: The oscilloscope (4) uses a digital oscilloscope.

3. The flat-field correction system for streak camera images at the working sweep speed based on a pulsed time-varying light source according to claim 1 or 2, characterized in that: The relative delay adjustment accuracy between the A output channel, B output channel and C output channel of the signal source (1) is of the order of nanoseconds.

4. A method for flat-field correction of streak camera images at the working sweep speed based on a pulsed time-varying light source, which uses the system for flat-field correction of streak camera images at the working sweep speed based on a pulsed time-varying light source according to any one of claims 1-3, characterized in that, It includes the following steps: Step 1: Set an attenuation sheet at the output end of the pulsed time-varying light source (2), start the streak camera (5), and make the input end of the streak camera (5) face the output end of the pulsed light source (2); Step 2: Send a light source trigger signal to the pulsed time-varying light source (2) through the signal source (1), and send a first external trigger signal and a second external trigger signal with the same start time and the same pulse width to the streak camera (5) and the oscilloscope (4) respectively; Step 3: When the pulsed time-varying light source (2) receives the light source trigger signal, it emits pulsed light, and the pulsed light reaches the streak camera (5) after being attenuated by the attenuation sheet; Step 4: The streak camera (5) scans the attenuated pulsed light based on the first external trigger signal to obtain the corresponding optical pulse image; At the same time, the monitoring photodetector (3) detects the attenuated pulsed light and converts it into an electrical signal and sends it to the oscilloscope (4), so that the oscilloscope (4) obtains a first time-voltage waveform diagram; At the same time, when the oscilloscope (4) receives the second external trigger signal, it obtains a second time-voltage waveform diagram, and the start time of the second time-voltage waveform diagram is the start time of the streak camera (5) for scanning; Step 5: Taking the start time as the starting point, on the first time-voltage waveform diagram, frame out the excerpt time-voltage waveform diagram within the duration corresponding to the sweep range of the streak camera (5); Step 6: Switch the attenuation sheet, and repeat steps 2 to 5 each time it is switched, so as to obtain multiple excerpt time-voltage waveform diagrams and multiple optical pulse images; Step 7: Select, from the multiple optical pulse images obtained in Step 6, the optical pulse image corresponding to any attenuation sheet with a transmittance of M, and calculate the average gray value of any column of pixels on this optical pulse image as the ideal gray value of this column of pixels; then calculate the ratio K of this ideal gray value to the voltage value at the corresponding moment in the corresponding excerpt time-voltage waveform diagram of this column of pixels, multiply all the voltage values in the excerpt time-voltage waveform by K, and then read the voltage value at the corresponding moment of each column of pixels on the optical pulse image from the excerpt time-voltage waveform after being multiplied by K as the ideal gray value Q of each pixel in each column of pixels on the optical pulse image scanned by the streak camera (5) when the transmittance of the attenuation sheet is M m ; Step 8: Calculate the ideal gray value Q of each pixel in each column of pixels on the scanned optical pulse image of the streak camera (5) corresponding to the attenuation sheet with other transmittances n :[[]]END]] Q n = Q m × N / M; In the formula, N represents the transmittance of other attenuation sheets; Step 9: Obtain the actual gray value of each pixel in each optical pulse image; Step 10: For each pixel of the image that can be acquired by the streak camera (5), plot corresponding coordinate points with the actual gray values corresponding to a series of attenuation filters with different transmittances as the abscissa and the corresponding ideal gray values as the ordinate, and fit all the coordinate points into the correction curve of the streak camera (5) to obtain the same number of correction curves as the number of pixels in each optical pulse image; Step 11: Acquire the target image to be corrected through the streak camera (5), obtain the actual gray value of each pixel on the target image to be corrected. On each curve obtained in Step 10, obtain the ideal gray value corresponding to each pixel, and correct the actual gray value of the corresponding pixel in the target image to be corrected with the obtained ideal gray values to complete the flat-field correction of the image.

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