A time stretched scanning framing monostatic imaging method and system

Abstract

This invention relates to the field of imaging system technology, providing a time-stretched scanning framing single-line-of-view imaging method and system, comprising: a photocathode for converting incident light signals into electron beams and transmitting ramp-stretching pulses; an anode grid, which, together with the photocathode, forms an accelerating electric field; a long magnetic lens for focusing the time-stretched electron beam; a deflection scanning system consisting of two sets of orthogonally arranged deflection plate electrodes, each set including two parallel and opposing plate electrodes, for applying a two-dimensional deflection electric field to the time-stretched electron beam, thereby spatially separating electron beams incident at different times; a gated microchannel plate detector for gating, multiplying, and imaging the deflected and separated electron beam; and a high-voltage pulse generator for generating cathode ramp-stretching pulses and microchannel plate gated selection pulses. This invention can better achieve high spatiotemporal resolution single-shot multi-frame single-line-of-view imaging.

Description

Technical Field

[0001] This invention relates to the field of imaging system technology, and more specifically, to a time-stretched scanning framing single-line-of-view imaging method and system. Background Technology

[0002] Ultrafast diagnostic technology is mainly applied in basic frontier science, large-scale scientific projects, and strategic high technologies, such as in laser inertial confinement fusion (ICF) research, to detect X-ray radiation processes in the 1–2 ns range. X-ray framing imaging cameras can obtain two-dimensional spatial information and one-dimensional temporal information (better than sub-nanosecond) of ICF plasma X-ray radiation, making them an important two-dimensional ultrafast diagnostic device.

[0003] Currently, practical X-ray framing cameras use pinhole imaging arrays to split X-ray beams. Different frames on the microchannel plate (MCP) imaging surface correspond to different pinholes, providing image information of the target object. The number of pinholes in the pinhole array increases with the required number of frames, leading to significant differences in imaging angles between different pinhole views, which negatively impacts diagnostic accuracy. To address this, a time-stretched scanning framing single-line-of-view imaging system is proposed, combining electron beam time-stretching, deflection scanning, and MCP traveling-wave gating imaging techniques. This system utilizes a time-varying electric field between cathode gratings to create a velocity difference among electrons within the electron beam cluster. The electron pulse time is gradually stretched by propagating through the drift region. Dynamic deflection plate electrodes and gated MCP detectors are placed in the subsequent path of the electron beam to construct a precise time-gating system, thereby improving the camera's imaging quality and diagnostic accuracy.

[0004] The time-stretched scanning framing single-line-of-view imaging technique was proposed in response to the urgent needs of ICF research. It can improve imaging quality and diagnostic accuracy, and enable X-ray framing imaging cameras to meet engineering and precision requirements, thus addressing the needs of ICF research and possessing significant scientific and application value. Summary of the Invention

[0005] The present invention provides a time-stretched scanning framing single-line imaging method and system, which can overcome some or all of the defects of the prior art.

[0006] A time-stretched scanning framing single-line-of-view imaging system according to the present invention comprises:

[0007] A photocathode is used to convert incident light signals into an electron beam and transmit ramp-broadening pulses. The photocathode is loaded with a negative DC bias voltage and superimposed with ramp-broadening pulses to generate a velocity difference within the electron beam cluster.

[0008] The anode grid is grounded and together with the photocathode, it forms an accelerating electric field.

[0009] A long magnetic lens generates a uniform magnetic field that acts on the photocathode surface to the MCP imaging surface, which is used to focus the time-stretched electron beam.

[0010] The deflection scanning system is located at the rear end of the uniform magnetic field generated by the long magnetic lens. It consists of two sets of orthogonally arranged deflection plate electrodes. Each set of deflection plates includes two parallel and opposite plate electrodes, which are used to apply a two-dimensional deflection electric field to the time-stretched electron beam, so that the electron beams incident at different times are spatially separated.

[0011] A gated microchannel plate detector, located after the deflection scanning system, includes a microchannel plate with microstrip lines deposited on it, a fluorescent screen, and a CCD, and is used to select, multiply, and image the electron beam after deflection and separation.

[0012] A high-voltage pulse generator is connected to a photocathode and a gated microchannel plate detector, respectively, to generate cathode ramp broadening pulses and microchannel plate gated selection pulses;

[0013] The deflection scanning system controls the scanning voltage amplitude and timing delay applied to each set of deflection plate electrodes to deflect electron beams carrying different time information emitted from the same spatial position of the photocathode to multiple predetermined spatial positions on the imaging surface of the gated microchannel plate detector without distortion. This enables the acquisition of multiple images on the microchannel plate imaging surface under a single-view incident condition of the object under test. The gated microchannel plate detector sequentially selects and multiplies electron beams arriving at different spatial positions through gate pulses transmitted along the microstrip line, and finally obtains multi-frame images by CCD recording.

[0014] Preferably, the deflection scanning system includes two sets of mutually perpendicular deflectors. The first set of deflectors consists of two horizontally arranged parallel plate electrodes, which are used to generate a vertical deflection electric field. The second set of deflectors consists of two vertically arranged parallel plate electrodes, which are used to generate a horizontal deflection electric field. The four deflection plates have the same geometric dimensions, with a plate width of 40 mm, a plate length of 20 mm, and a plate spacing of 42 mm.

[0015] Preferably, the distance Δz between the deflection scanning system and the imaging surface of the gated microchannel plate detector is 180 mm; when a -3 kV DC bias voltage is applied to the cathode and a broadened pulse with a slope of 5 V / ps is superimposed, the amplitude of the scanning voltage applied to the deflection plate ranges from 900 V to 1000 V.

[0016] Preferably, the deflection plates are in a uniform electric field, and the electrons move in a parabola in the uniform electric field. After exiting the deflection system, the electrons continue to deflect and drift to the microchannel plate imaging surface at a constant speed. This allows two-dimensional images carrying different time information at the same spatial location to be deflected without distortion to nine different spatial locations on the gated microchannel plate detector imaging surface, so that nine images can be obtained on the microchannel plate imaging surface after the object under test enters the system from a single perspective.

[0017] Preferably, the gated microchannel plate detector has a temporal resolution of 70 ps. The deflection scanning system maintains a constant deflection voltage within each 70 ps time period and changes the deflection voltage sequentially in time order, so that the electron beam is deflected to nine different positions in the horizontal and vertical directions on the imaging surface to achieve nine-segment imaging.

[0018] Preferably, in the gated microchannel plate detector, the input surface of the microchannel plate is deposited with three parallel microstrip lines, each with a width of 12 mm and a spacing of 3 mm between adjacent microstrip lines. The microstrip lines are composed of a 400 nm copper layer and a 200 nm gold layer, with Cu deposited on the substrate. The output surface of the microchannel plate is deposited with copper and gold layers of the same thickness as the input surface.

[0019] Preferably, the microchannel plate has an outer diameter of 60 mm, a thickness of 0.5 mm, a channel diameter of 12 μm, a channel spacing of 14 μm, and a channel bevel angle of 6°; the distance between the microchannel plate and the fluorescent screen is 0.5 mm, and the CCD is set close to the fluorescent screen.

[0020] Preferably, on the imaging surface of the gated microchannel plate detector, the center-to-center distance between two adjacent images in the horizontal direction is 14 mm, the center-to-center distance between two adjacent images in the vertical direction is 15 mm, and the diameter of each image is 12 mm; the deflection scanning system deflects the electron beam by 14 mm in the horizontal direction and 15 mm in the vertical direction to match the position of the microstrip line and the transmission speed of the gated pulse.

[0021] Preferably, the transmission speed of the gated pulse on the microstrip line is 2×10⁻⁶. 8 At m / s, the gated pulses are transmitted sequentially along the microstrip line, selecting electron beam images that arrive at different positions on the imaging surface. The selected electron beams are multiplied by the microchannel plate and then bombard the fluorescent screen to form a visible light image, while the unselected electron beams are absorbed by the microchannel plate.

[0022] This invention provides a time-stretched scanning framing single-line-of-view imaging method, which employs the aforementioned time-stretched scanning framing single-line-of-view imaging system.

[0023] The beneficial effects of this invention are as follows:

[0024] This invention combines electron beam time-stretching technology, deflection scanning technology, and MCP traveling-wave gated framing imaging technology to solve the multi-view imaging problem caused by the reliance on pinhole imaging arrays in traditional traveling-wave gated framing cameras. By spatially separating electron beams carrying different time information through a deflection scanning system, multi-frame imaging under single-view incidence conditions of the object under test is achieved, eliminating image distortion caused by differences in viewpoint and errors caused by physical process reconstruction, significantly improving imaging quality and diagnostic accuracy.

[0025] This invention proposes a deflection scanning system consisting of two sets of orthogonal deflection plates, which, in conjunction with a gated MCP detector for vapor-deposited microstrip lines, forms a precise time-gated system. By precisely controlling the amplitude and delay of the deflection voltage, the electron beam is deflected to different positions on the MCP imaging surface at different time intervals. Combined with sequential gating by traveling wave gating pulses, a high time resolution better than 10 ps is achieved (up to 6 ps under a -3 kV bias voltage and a 5 V / ps broadened pulse), meeting the diagnostic requirements of high-precision physics experiments such as ICF for radiation processes of ~100 ps.

[0026] This invention uses a long magnetic lens to focus the electron beam, combined with a high spatial resolution MCP detector (channel diameter 12 μm, spacing 14 μm). Under optimized excitation ampere-turns (greater than 28000 AT), the total spatial resolution of the system is better than 20 lp / mm, which can clearly distinguish the tiny structure of the target under test and meet the requirements of precision diagnosis.

[0027] The deflection scanning system employs a uniform electric field design, with the electron beam moving in a parabolic motion between the deflection plates. After exiting, it drifts at a constant speed to the MCP imaging surface, ensuring that the image is distortion-free during the deflection process, maintaining the integrity of the original spatial information, and improving image quality and data reliability.

[0028] This invention uses electron beam time-stretching technology to stretch a picosecond signal to the nanosecond level, enabling high temporal resolution imaging to be achieved using a gated MCP detector with lower temporal resolution (e.g., 70 ps). This reduces the stringent requirements of the system on the gated pulse width and improves the system's integration and engineering feasibility. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of a time-stretched scanning framing single-line-of-view imaging system in one embodiment;

[0030] Figure 2 This is the voltage timing diagram of the deflection system when a -3 kV cathode bias voltage is superimposed with a 5 V / ps widened pulse in the embodiment;

[0031] Figure 3This is a schematic diagram illustrating the relationship between system time resolution, cathode bias voltage, and pulse broadening slope in the embodiment.

[0032] Figure 4 This is a schematic diagram illustrating the relationship between the spatial resolution of the long magnetic lens and the excitation ampere-turns in the embodiment. Detailed Implementation

[0033] To further understand the content of this invention, a detailed description of the invention will be provided in conjunction with the accompanying drawings and embodiments. It should be understood that the embodiments are merely illustrative and not limiting of the invention.

[0034] Example

[0035] like Figure 1 As shown, this embodiment provides a time-stretched scanning framing single-line-of-view imaging system, which includes:

[0036] The photocathode 110 is used to convert the incident light signal into an electron beam and transmit a ramp-broadening pulse. The photocathode is loaded with a negative DC bias voltage and superimposed with a ramp-broadening pulse to generate a velocity difference within the electron beam cluster.

[0037] The anode grid 120 is grounded and together with the photocathode forms an accelerating electric field.

[0038] The long magnetic lens 130 generates a uniform magnetic field that acts on the photocathode surface to the MCP imaging surface, which is used to focus the time-stretched electron beam.

[0039] The deflection scanning system 140 is located at the rear end of the uniform magnetic field generated by the long magnetic lens. It consists of two sets of orthogonally arranged deflection plate electrodes. Each set of deflection plates includes two parallel and opposite plate electrodes, which are used to apply a two-dimensional deflection electric field to the time-stretched electron beam so that the electron beams incident at different times are spatially separated.

[0040] A gated microchannel plate detector 150, located after the deflection scanning system, includes a microchannel plate MCP 151 with microstrip lines deposited on it, a fluorescent screen 152, and a CCD 153, used to select, multiply, and image the electron beam after deflection and separation.

[0041] The high-voltage pulse generator 160 is connected to the photocathode and the gated microchannel plate detector, respectively, and is used to generate cathode ramp broadening pulses and microchannel plate gated selection pulses.

[0042] The deflection scanning system adjusts the scanning voltage amplitude and timing delay applied to each set of deflection plate electrodes to deflect electron beams carrying different time information emitted from the same spatial position of the photocathode to multiple predetermined spatial positions on the imaging surface of the gated microchannel plate detector without distortion, thereby enabling the acquisition of multiple images on the microchannel plate imaging surface under a single-view incident condition of the object under test. The gated microchannel plate detector sequentially selects and multiplies electron beams arriving at different spatial positions through gate pulses transmitted along the microstrip line 180, and finally obtains multi-frame images by CCD recording.

[0043] The working principle is as follows: The light signal from the target object is irradiated onto the photocathode, and the light signal is converted into an electrical signal carrying the same information through the photoelectric effect; a negative DC bias voltage is applied to the photocathode and a ramp-widened pulse is superimposed (transmitted through the cathode microstrip line); the anode grid is grounded; the photoelectron pulse 170 is synchronized with the rising edge of the ramp-widened pulse, so that the electrons at the front of the photoelectron pulse beam emitted from the cathode and subjected to the accelerating electric field gain more energy than the electrons at the back, thus making the electrons at the front move faster than the electrons at the back; after transmission through the drift region from the anode to the MCP, the time width of the electron beam is widened, achieving time amplification; the widened electron beam is focused by a long magnetic lens into the dynamic deflection system at the rear of the drift region, adjusting the voltage amplitude and delay of each deflection electrode, thus achieving time amplification. Electron beams incident on the deflection system at different time intervals are separated under the scanning deflection electric field, transforming from a temporal distribution to a spatial distribution. The deflected and separated electron beams strike the microstrip transmission line at the MCP input surface, simultaneously applying a narrow-width gated pulse to this microstrip line. The pulses propagate sequentially along the microstrip line, with only a segment of the microstrip having voltage within a given time interval. The electron image in this segment is then selected and amplified by the MCP, bombarding the fluorescent screen to form a visible light image. If the electron beam is not synchronously gated by the pulse, the electron image is absorbed by the MCP, resulting in no image output. After a certain transmission time, the gated pulse reaches another electron image region, at which point the image is output. In this way, these electron images are sequentially selected one by one, and the output image is recorded by a CCD, achieving multi-frame imaging. Because the electron beam is amplified temporally, even using a gated MCP detector with lower temporal resolution can achieve a high temporal resolution for the camera system.

[0044] The deflection scanning system is a key component of the camera's multi-frame imaging capability. Located at the rear of the image converter tube, it is 180 mm away from the MCP imaging plane. It consists of two sets of mutually perpendicular deflectors, each set comprising two parallel plate electrodes. These four deflection plates are identical in size: a width D of 40 mm, a length L (along the optical axis) of 20 mm, negligible thickness, and a spacing d of 42 mm between them. The electron beam, focused by a long magnetic lens, enters the deflection system. A time-varying scanning voltage is applied to the deflection plates (V1 and V3 are applied to the horizontal deflection plates, controlling the electric field in the vertical direction; V2 and V4 are applied to the vertical deflection plates, controlling the electric field in the horizontal direction). When a -3 kV DC bias voltage is applied to the cathode and a 5V / ps broadened pulse is superimposed, the amplitude adjustment range of the voltage required by the deflection plate is 900 V~1000 V. Because the energy of the electron beam emitted from the cathode varies at different times, the required deflection voltage varies, but the amplitude difference is not significant. The voltage timing of the deflection system at this time is as follows: Figure 2 As shown, a time-varying deflection electric field is formed between the deflection plates, simultaneously controlling the horizontal and vertical deflection of the electron beam within the deflection system. Considering the time resolution of the gated MCP detector is 70 ps, ​​the voltage on the deflection plates remains constant within each 70 ps time interval. The area between the deflection plates can be considered a uniform electric field, and the trajectory of the electrons in the uniform electric field is a parabola. After exiting the deflection system, the electrons continue to deflect at a uniform speed and drift to the MCP imaging surface (without the deflection system, the electron beam emitted from the center of the photocathode would be imaged at the center of the MCP). This allows two-dimensional images carrying different time information at the same spatial location to be deflected without distortion to nine different spatial positions on the imaging surface of the gated microchannel plate MCP detector, enabling the acquisition of nine images on the MCP imaging surface after the object under test enters the system from a single perspective. The delay circuit 190 (connected to the deflection scanning system is the scanning circuit 200, which is also connected to the delay circuit 190, which receives the trigger signal) delays the signal until the previous 70 ps ends. At this point, the deflection plate voltage changes, and the next 70 ps begins. During this time, the direction of the deflection force on the electron beam changes, and the electron beam is imaged in another image. Along the microstrip line propagation direction on the MCP input surface, the deflection plate voltage is sequentially changed from F0 to F8 for scanning. Combined with MCP traveling wave gating, this achieves... Figure 1 The image shown is a nine-frame image. Strict control of the voltage amplitude and delay applied to the two sets of deflectors is required to ensure accurate time synchronization and high-quality image output.

[0045] The gated MCP detector is the core module of the camera. Its temporal resolution is determined by the ratio of its temporal resolution to the electron beam time-spanning factor. It consists of microstrip lines deposited on the MCP, the MCP itself, a fluorescent screen fabricated on an optical fiber panel, and a CCD. The MCP is a high-spatial-resolution, high-gain electron multiplier device, a thin glass sheet composed of numerous microchannels. Each via acts as an independent electron multiplier, amplifying the electron signal. Cu and Au are deposited at the input and output ports of each microchannel. The electron signal is input to the inner wall surface of the channel, generating primary electrons. When a large voltage is applied between the two end faces of the MCP through electrodes, an electric field is generated within each microchannel. This electric field accelerates the primary electrons, causing them to propagate forward along the channel and collide with the inner wall to generate new secondary electrons. These secondary electrons are then accelerated and collide with the channel wall, repeating this process until they are emitted from the channel output port, thus achieving electron multiplication. Electrons are accelerated by the electric field between the MCP output surface and the fluorescent screen. The high-speed electrons bombard the phosphor, emitting light and achieving electro-optic spatial and intensity conversion, producing a visible light image output. When there is no voltage or the voltage is too low to generate gain between the two ends of the MCP, the signal input to the MCP will be absorbed, and no image will be output. At a certain moment, the MCP detector samples and multiplies the time-stretched electron beam imaging a certain area of ​​the MCP using a gated pulse, and transmits it in a traveling wave manner on the microstrip line. At another moment, it samples and multiplies the electron beam of another area, thereby obtaining multiple images at different times.

[0046] The system is designed with an MCP outer diameter of 60 mm, a thickness of 0.5 mm, a channel diameter of 12 μm, a channel spacing of 14 μm, and a chamfer angle of 6°. Three microstrip lines (composed of 400 nm Cu and 200 nm Au, with Cu deposited on the substrate) are deposited on the MCP input surface. The entire MCP output surface is deposited with Cu and Au of the same thickness as the input surface. The MCP is 0.5 mm away from the phosphor screen, and the CCD is placed flush with the phosphor screen. Considering that the propagation speed of the gated pulses on the microstrip lines is approximately 2 × 10⁻⁶, the system is designed to handle such cases. 8 The speed is m / s. The horizontal spacing between two adjacent images on the MCP imaging plane is 14 mm, and the vertical spacing between two adjacent images is 15 mm (that is, the deflection distance of the electron beam in the horizontal direction is required to be 14 mm and the deflection distance in the vertical direction is required to be 15 mm). The diameter of each image is 12 mm. This can meet the requirements of MCP time resolution and image spacing and form a precise time gating system with the deflection system.

[0047] This embodiment provides a time-stretched scanning framing single-line-of-view imaging method, which employs the aforementioned time-stretched scanning framing single-line-of-view imaging system.

[0048] Time resolution characteristics

[0049] To verify the practicality of the designed imaging system, its temporal resolution characteristics were theoretically simulated. The system's temporal resolution refers to the smallest resolvable time interval, typically expressed as the full width at half maximum (FWHM) of the gain-time curve, and is on the order of picoseconds. The temporal resolution mainly depends on the cathode bias voltage, the broadened pulse slope, and the drift length. The cathode diameter was set to 60 mm, the electron emission source diameter to 12 mm, a 12 mm wide microstrip line was deposited on the cathode surface, the cathode-grid spacing was 1 mm, and the drift region (from the anode to the MCP) length was 500 mm. The cathode broadened pulse slope was varied to 3 V / ps, 5 V / ps, 7 V / ps, and 10 V / ps, and the cathode DC bias voltage was adjusted to -2.0 kV, -2.5 kV, -3.0 kV, -3.5 kV, and -4.0 kV. The simulation results are as follows: Figure 3 As shown.

[0050] Analysis shows that when the cathode bias voltage remains constant, the time resolution improves with increasing pulse broadening slope because the time broadening factor increases with the pulse broadening slope. If the cathode bias voltage is -3.0 kV, the time resolution is better than 6 ps when the pulse broadening slope is 5 V / ps, and it improves to better than 3 ps when the pulse broadening slope increases to 10 V / ps. When the cathode bias voltage decreases, the electron transport speed in the drift region slows down, the time broadening factor increases, and therefore the system's time resolution improves. However, the improvement in time resolution is not unlimited; it is limited by transit time dispersion. Therefore, the cathode bias voltage needs to be matched with the pulse broadening slope to obtain the optimal time resolution of the system.

[0051] Spatial resolution characteristics

[0052] Spatial resolution is another key performance indicator of a frame-shift camera, referring to its ability to resolve the smallest details of a target, generally expressed as the number of line pairs resolved per millimeter, or lp / mm (or μm). The spatial resolution capability of the long magnetic lens and the gated microchannel plate detector determines the spatial resolution performance of the entire camera system. The spatial resolution characteristics of the image converter tube were simulated with an object-to-image ratio of 1:1. The long magnetic lens used was made of a 1320-turn solenoid coil, generating a uniformly distributed magnetic field that constrained the lateral drift of the electron beam and focused it at the end of the drift region, resulting in a planar imaging plane. By changing only the excitation ampere-turns of the long magnetic lens to 5200 AT, 12130 AT, 19918 AT, 27284 AT, and 34650 AT, the simulation results are as follows: Figure 4 As shown, this analysis shows that the larger the excitation ampere-turns of the long magnetic lens, the stronger the on-axis magnetic field, which in turn strengthens the lateral focusing effect on the electron beam and thus the higher the spatial resolution.

[0053] The system's total spatial resolution

[0054] in For the spatial resolution of the long magnetic lens, The spatial resolution of the gated MCP detector is 25 lp / mm in this case. Here, 1 represents the spatial imaging magnification of the long magnetic lens. When the lens excitation ampere-turns are greater than 28000 AT, the spatial resolution of the system can be calculated to be better than 20 lp / mm using the above formula.

[0055] This embodiment combines electron beam time stretching technology, scanning technology, and MCP traveling wave gating framing imaging technology to achieve time stretching scanning framing single-line-of-view imaging. This solves the non-single-line-of-view imaging problem caused by the traditional traveling wave gating framing mechanism and improves the imaging quality and detection accuracy of the camera.

[0056] This embodiment proposes for the first time that a deflection scanning system consisting of two sets of mutually perpendicular deflection plates is paired with a gated MCP detector of vapor-deposited microstrip lines to form a precise time-gated system, thereby achieving high spatiotemporal resolution single-shot multi-frame single-line imaging without the need for a pinhole imaging array.

[0057] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the figures shown are only one embodiment of the present invention; the actual structure is not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. A time stretched scanning framing monostatic imaging system characterized by: include: A photocathode is used to convert incident light signals into an electron beam and transmit ramp-broadening pulses. The photocathode is loaded with a negative DC bias voltage and superimposed with ramp-broadening pulses to generate a velocity difference within the electron beam cluster. The anode grid is grounded and together with the photocathode, it forms an accelerating electric field. A long magnetic lens generates a uniform magnetic field that acts on the photocathode surface to the MCP imaging surface, which is used to focus the time-stretched electron beam. The deflection scanning system is located at the rear end of the uniform magnetic field generated by the long magnetic lens. It consists of two sets of orthogonally arranged deflection plate electrodes. Each set of deflection plates includes two parallel and opposite plate electrodes, which are used to apply a two-dimensional deflection electric field to the time-stretched electron beam, so that the electron beams incident at different times are spatially separated. A gated microchannel plate detector, located after the deflection scanning system, includes a microchannel plate with microstrip lines deposited on it, a fluorescent screen, and a CCD, and is used to select, multiply, and image the electron beam after deflection and separation. A high-voltage pulse generator is connected to a photocathode and a gated microchannel plate detector, respectively, to generate cathode ramp broadening pulses and microchannel plate gated selection pulses; The deflection scanning system controls the scanning voltage amplitude and timing delay applied to each set of deflection plate electrodes to deflect electron beams carrying different time information emitted from the same spatial position of the photocathode to multiple predetermined spatial positions on the imaging surface of the gated microchannel plate detector without distortion. This enables the acquisition of multiple images on the microchannel plate imaging surface under a single-view incident condition of the object under test. The gated microchannel plate detector sequentially selects and multiplies electron beams arriving at different spatial positions through gate pulses transmitted along the microstrip line, and finally obtains multi-frame images by CCD recording.

2. A temporally stretched scanning framing monostatic imaging system according to claim 1, characterized in that: The deflection scanning system includes two sets of mutually perpendicular deflectors. The first set of deflectors consists of two horizontally arranged parallel plate electrodes, which are used to generate a vertical deflection electric field. The second set of deflectors consists of two vertically arranged parallel plate electrodes, which are used to generate a horizontal deflection electric field. The four deflection plates have the same geometric dimensions: a plate width of 40 mm, a plate length of 20 mm, and a plate spacing of 42 mm.

3. A time stretched scanning framing monostatic imaging system according to claim 2, wherein: The distance Δz between the deflection scanning system and the imaging surface of the gated microchannel plate detector is 180 mm; when a -3 kV DC bias voltage is applied to the cathode and a broadened pulse with a slope of 5 V / ps is superimposed, the amplitude of the scanning voltage applied to the deflection plate ranges from 900V to 1000V.

4. A time stretched scanning framing monostatic imaging system according to claim 3, wherein: The deflection plates are in a uniform electric field. The electrons move in a parabola in the uniform electric field. After exiting the deflection system, the electrons continue to deflect and drift to the microchannel plate imaging surface at a constant speed. This allows two-dimensional images carrying different time information at the same spatial location to be deflected without distortion to nine different spatial locations on the gated microchannel plate detector imaging surface. This enables the test object to be incident on the system from a single perspective and obtain nine images on the microchannel plate imaging surface.

5. A temporally stretched scanning framing monostatic imaging system according to claim 4, wherein: The gated microchannel plate detector has a temporal resolution of 70 ps. The deflection scanning system keeps the deflection voltage constant during each 70 ps time period and changes the deflection voltage sequentially in time order, so that the electron beam is deflected to 9 different positions in the horizontal and vertical directions on the imaging surface to achieve nine-segment imaging.

6. The time-stretched scanning framing single-line-of-view imaging system according to claim 5, characterized in that: In the gated microchannel plate detector, three parallel microstrip lines are deposited on the input surface of the microchannel plate. Each microstrip line is 12 mm wide and the spacing between adjacent microstrip lines is 3 mm. The microstrip lines are composed of a 400 nm copper layer and a 200 nm gold layer, and Cu is deposited on the substrate. The output surface of the microchannel board is coated with copper and gold layers of the same thickness as the input surface by vapor deposition.

7. A time stretched scanning framing monostatic imaging system according to claim 6, wherein: The microchannel plate has an outer diameter of 60 mm, a thickness of 0.5 mm, a channel diameter of 12 μm, a channel spacing of 14 μm, and a channel bevel angle of 6°; the distance between the microchannel plate and the fluorescent screen is 0.5 mm, and the CCD is set close to the fluorescent screen.

8. A temporally stretched scanning framing monostatic imaging system according to claim 7, wherein: On the imaging surface of the gated microchannel plate detector, the center-to-center distance between two adjacent images in the horizontal direction is 14 mm, and the center-to-center distance between two adjacent images in the vertical direction is 15 mm. The diameter of each image is 12 mm. The deflection scanning system deflects the electron beam by 14 mm in the horizontal direction and 15 mm in the vertical direction to match the position of the microstrip line and the transmission speed of the gated pulse.

9. A temporally stretched scanning framing monostatic imaging system according to claim 8, wherein: The transmission speed of the gated pulse on the microstrip line is 2×10⁻⁶. 8 At m / s, the gated pulses are transmitted sequentially along the microstrip line, selecting electron beam images that arrive at different positions on the imaging surface. The selected electron beams are multiplied by the microchannel plate and then bombard the fluorescent screen to form a visible light image, while the unselected electron beams are absorbed by the microchannel plate.

10. A time stretched scanning framing monostatic imaging method, characterized by: It employs a time-stretched scanning framing single-line imaging system as described in any one of claims 1-9.

Images