Strong magnetic confinement high-speed gating image intensifier and imaging method thereof

Abstract

The invention relates to an intensifier and an imaging method thereof, in particular to a strong magnetic confinement high-speed gating image intensifier and an imaging method thereof, and aims to solve the problem that the shortest exposure time is in an ns order due to the fact that an existing image intensifier is affected by large coupling capacitance between a photocathode and an MCP. The image intensifier comprises an image intensifier body, wherein the image intensifier body comprises an input window, a photoelectric cathode, a micro-channel plate, a fluorescent screen and an output window which are sequentially arranged in the light path propagation direction; the input window comprises an input surface and an output surface; the photoelectric cathode is plated on the output surface of the input window; the micro-channel plate comprises an input surface and an output surface; a gated voltage U is arranged between the photoelectric cathode and the input surface of the micro-channel plate; an electrified solenoid is arranged outside the image intensifier body, and the central axis of the image intensifier body coincides with the central axis of the electrified solenoid; and the distance between the photoelectric cathode and the input surface of the micro-channel plate is greater than or equal to 0.3 mm.

Description

Technical Field

[0001] The present invention relates to an intensifier and an imaging method thereof, and particularly to a strongly magnetically constrained high-speed gated image intensifier and an imaging method thereof. Background Art

[0002] The high-resolution spatio-temporal information obtained through ultrafast image diagnostic techniques is of great value for analyzing high-energy density physical reaction processes such as laser-matter interaction, inertial confinement fusion, and wire electrical explosion. For the time resolution and spatial resolution requirements of different research objectives, common techniques include rotating mirror framing cameras, traveling wave gated framing cameras, image intensifier gated framing cameras, streak cameras, and all-optical solid-state ultrafast imaging techniques. Among them, the image intensifier gated framing camera has a large frame size, high time resolution, high two-dimensional spatial resolution, and wide spectral response, and is widely used in the field of visible light ultrafast diagnosis.

[0003] Chinese patents CN118197883A and CN118136487A both disclose image intensifiers. A common image intensifier includes a vacuum-sealed cavity, and a photocathode, a microchannel plate, and an output phosphor screen that are sequentially arranged in the vacuum-sealed cavity along the optical path propagation direction; the part of the vacuum-sealed cavity close to the photocathode is an input window for photoelectrons to pass through and reach the photocathode; the input window includes an input surface and an output surface for transmitting optical signals; the photocathode is plated on the output surface of the input window; and the microchannel plate is provided with a plurality of through holes.

[0004] Among them, the microchannel plate is a device that can continuously multiply the number of electrons. A microchannel plate is usually composed of millions of glass capillary channels arranged at a certain inclination angle. The inner wall of each channel has good electrical conductivity and secondary electron emission performance, and the two end faces of the channel are plated with input and output electrodes. When a voltage is applied between the two electrodes, a uniform electric field is established along the axis in the channel. The electrons entering the channel are continuously impacted on the inner wall of the channel under the action of this electric field, generating secondary electrons and realizing continuous multiplication of the number. Due to high gain, fast response, and excellent anti-magnetic field performance, the microchannel plate is widely used in weak photoelectric detection and imaging devices such as photomultiplier tubes and image intensifiers.

[0005] The working principle of the image intensifier is that the photocathode converts the optical image into photoelectrons, which are bombarded on the microchannel plate under the action of the vacuum electric field to generate electron multiplication. The multiplied electrons are converted into photons again on the phosphor screen. This process can achieve a brightness gain of 10 3 ~10 6 times, and this process is widely used in visual night equipment. During the high-speed gating process, a high-voltage electric field for instantaneous gating is realized inside the image intensifier. The photoelectrons within this time reach the phosphor screen to form a switch for the imaging optical path, and the switching speed can reach the ns (nanosecond) level.

[0006] The exposure time of a gated framing camera with an image intensifier is determined by the image intensifier. The working principle of the gated framing camera is as follows: the photocathode of the image intensifier converts the visible light image into photoelectrons, which are bombarded on the microchannel plate (MCP, Microchannel Plate) under the action of a vacuum high-voltage electric field to generate multiplied photoelectrons. The multiplied photoelectrons are converted into photons again on the phosphor screen. By applying a gated pulse voltage between the photocathode and the MCP of the image intensifier, a high-speed switch of the optical path is realized. The common sizes of image intensifiers are Φ18mm, Φ25mm, and Φ40mm. In order to maintain high spatial resolution in proximity focusing, the distance between the photocathode and the MCP is generally 0.1mm, and there will be a large coupling capacitance (Φ18mm~22pF) between the photocathode and the MCP. This capacitance will slow down the formation of the gated high-voltage electric field, so its limit exposure time is generally in the ns order of magnitude.

[0007] Existing image intensifiers are difficult to diagnose ultrafast physical processes in the order of hundreds of picoseconds (such as inertial confinement fusion, pulsed plasma diagnosis). Summary of the Invention

[0008] The purpose of the present invention is to solve the problem that the existing image intensifier is affected by the large coupling capacitance between the photocathode and the MCP, resulting in the shortest exposure time in the ns order of magnitude and being difficult to diagnose ultrafast physical processes in the order of hundreds of picoseconds, and to provide a strongly magnetically confined high-speed gated image intensifier and its imaging method.

[0009] To achieve the above purpose, the technical solution provided by the present invention is:

[0010] A strongly magnetically confined high-speed gated image intensifier includes an image intensifier body. The image intensifier body includes an input window, a photocathode, a microchannel plate, a phosphor screen, and an output window arranged in sequence along the optical path propagation direction; the input window includes an input surface and an output surface for transmitting optical signals; the photocathode is plated on the output surface of the input window; the microchannel plate includes an input surface and an output surface, on which there are a plurality of through holes, and both the input surface and the output surface are plated with conductive metal films, and an electron filter film is also plated on the input surface; an optional voltage U is set between the photocathode and the input surface of the microchannel plate; the phosphor screen is arranged on the input surface of the output window, and there are intervals between the microchannel plate and the phosphor screen, and between the photocathode and the microchannel plate respectively; the special feature is that:

[0011] The distance between the photocathode and the input surface of the microchannel plate is greater than or equal to 0.3mm to 1.5mm.

[0012] An energized solenoid is arranged outside the image intensifier body.

[0013] Furthermore, the image intensifier body is arranged in the middle of the energized solenoid, and the central axis of the image intensifier body along the optical path propagation direction coincides with the central axis of the energized solenoid.

[0014] Furthermore, the magnetic induction intensity of the magnetic field generated by the energized solenoid at any point between the photocathode and the input surface of the microchannel plate of the magnitude

[0015] Furthermore, the gating amplitude of the voltage U is 5V, and the gating pulse width is less than or equal to 800ps.

[0016] Furthermore, the distance between the output surface of the microchannel plate and the fluorescent screen is 0.5mm - 0.6mm.

[0017] Furthermore, the microchannel plate is a glass plate, and the diameter of each through hole on it is 6μm - 10μm.

[0018] Furthermore, the phosphor of the fluorescent screen is of type P20, P22, P43, P46 or P47, and the photocathode is of type S20 or S25.

[0019] Furthermore, the material of the electron filter membrane is Al2O3.

[0020] Furthermore, the distance between the output surface of the microchannel plate and the fluorescent screen is 0.5mm; the distance between the photocathode and the input surface of the microchannel plate is 0.3mm; the diameter of each through hole on the microchannel plate is 6μm.

[0021] Meanwhile, the present invention also provides an imaging method for the above-mentioned high-speed gated image intensifier with strong magnetic confinement, which is characterized in that it includes the following steps:

[0022] Step 1: Install the intensifier body in the inner hole of the energized solenoid to form a high-speed gated image intensifier with strong magnetic confinement;

[0023] Step 2: Set the voltage U to 5V to enable the high-speed gated image intensifier with strong magnetic confinement to start imaging;

[0024] Step 3: Set the current of the energized solenoid to generate a magnetic field;

[0025] Step 4: The camera starts to expose and records the imaging result of the fluorescent screen in the image intensifier body.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] 1. The present invention proposes a strong magnetic confinement and wide-spacing collaborative regulation strategy. By increasing the spacing between the photocathode and the input surface of the microchannel plate, the coupling capacitance is reduced to break through the time limit of the traditional proximity structure. At the same time, strong magnetic confinement of the radial dispersion of photoelectrons is introduced to achieve the collaborative optimization of high spatial resolution and picosecond-level time resolution.

[0028] 2. For the high-speed gated image intensifier with strong magnetic confinement provided by the present invention, the distance between the photocathode and the input surface of the microchannel plate is changed from the existing 0.1 - 0.2 mm to greater than or equal to 0.3 mm, which can reduce the coupling capacitance between the photocathode and the microchannel plate and achieve a picosecond-level exposure time for the image intensifier.

[0029] 3. For the high-speed gated image intensifier with strong magnetic confinement provided by the present invention, an energized solenoid is arranged outside the image intensifier body. The strong magnetic field generated by the energized solenoid is used to confine photoelectrons, achieving high spatial resolution of the image intensifier body and high-speed gated imaging of the image intensifier. Without significantly reducing the imaging quality while ensuring a picosecond-level exposure time for the image intensifier.

[0030] 4. For the high-speed gated image intensifier with strong magnetic confinement provided by the present invention, an electron filtering film is deposited on the input surface of the microchannel plate, which can filter a large number of low-energy photoelectrons while allowing a large number of high-energy photoelectrons to pass through; conductive metal films are deposited on both the input surface and the output surface of the microchannel plate for realizing the multiplication of photoelectrons.

[0031] 5. The imaging method of the high-speed gated image intensifier with strong magnetic confinement provided by the present invention can achieve a picosecond-level exposure time and high-resolution imaging, and is applicable to various scenarios requiring high-speed photography. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a schematic structural diagram of an embodiment of the high-speed gated image intensifier with strong magnetic confinement of the present invention (the energized solenoid is not shown);

[0033] Figure 2 is a time-gating characteristic curve diagram of an embodiment of the high-speed gated image intensifier with strong magnetic confinement of the present invention;

[0034] Figure 3 is a photo taken by a camera after imaging through an existing image intensifier;

[0035] Figure 4 is a photo taken by a camera after imaging through an embodiment of the high-speed gated image intensifier with strong magnetic confinement of the present invention;

[0036] DESCRIPTION OF THE REFERENCE NUMERALS:

[0037] 11 - input window, 12 - output window, 13 - photocathode, 2 - microchannel plate, 3 - electron filtering film, 4 - fluorescent screen. Detailed Embodiments

[0038] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0039] As Figure 1 shown, a high-speed gated image intensifier with strong magnetic confinement includes an image intensifier body, an input window 11, a photocathode 13, a microchannel plate 2, a fluorescent screen 4, and an output window 12 arranged in sequence along the optical path propagation direction; the input window 11 includes an input surface and an output surface for transmitting optical signals; the photocathode 13 is plated on the output surface of the input window 11; the microchannel plate 2 includes an input surface and an output surface, on which there are a plurality of through holes, each through hole having a diameter of 6 μm, and both its input surface and output surface are plated with conductive metal films, and an electron filtering film 3 is also plated on the input surface; an optional voltage U is set between the photocathode 13 and the input surface of the microchannel plate 2, where the gating amplitude of the voltage U is 5 V. The fluorescent screen 4 is arranged on the input surface of the output window 12, and intervals are respectively arranged between the microchannel plate 2 and the fluorescent screen 4, and between the photocathode 13 and the microchannel plate 2.

[0040] To meet the requirements of different output wavelengths, luminous efficiencies, and afterglow times, the phosphor of the fluorescent screen 4 can be of type P20, P22, P43, P46, or P47; meanwhile, the photocathode 13 can be of type S20 or S25. The electron filtering film 3 is used to filter low-energy photoelectrons and transmit high-energy photoelectrons, and its material is Al2O3.

[0041] In this embodiment, the distance between the output surface of the microchannel plate 2 and the fluorescent screen 4 is 0.5 mm.

[0042] The distance between the photocathode 13 and the input surface of the microchannel plate 2 is 0.3 mm, which reduces the coupling capacitance and enables the loading of a gating voltage at the picosecond (ps) level for the image intensifier. Refer to Figure 2 to shorten the shortest exposure time to 830 ps.

[0043] An energized solenoid is arranged outside the image intensifier body, and the image intensifier body is arranged in the middle of the energized solenoid. The central axis of the image intensifier body coincides with the central axis of the energized solenoid. The magnetic induction intensity of the magnetic field generated by the energized solenoid at any point between the photocathode 13 and the input surface of the microchannel plate 2 This is to use the strong magnetic field generated by the energized solenoid to confine photoelectrons, achieve high spatial resolution, and finally realize high-speed gated imaging at the picosecond level for the image intensifier.

[0044] In this embodiment, in order to test the imaging effect of the high-speed gated image intensifier with strong magnetic confinement, the following experimental equipment was built: a light source, a collimator, a first relay lens, a high-speed gated image intensifier with strong magnetic confinement, a second relay lens, and a camera were sequentially arranged along the optical path propagation direction. The first relay lens and the second relay lens were both used to assist imaging. A filter, a ground glass, and a resolution card were also arranged in the collimator. The collimator was used to image the resolution card on the photocathode of the image intensifier body. After the image intensifier body was imaged, the image of the fluorescent screen was recorded by the camera through the second relay lens. The experimental results are shown in Figure 3 . Under the same imaging conditions, a current of 100 A was applied to the energized solenoid to make the magnetic induction intensity of the magnetic field generated by the energized solenoid such that the spatial resolution of the imaging was improved from the originally indistinguishable 4 lp / mm (line pairs per millimeter) to the distinguishable 8 lp / mm (line pairs per millimeter). The results are shown in Figure 4 .

[0045] Meanwhile, this embodiment also provides an imaging method for the above high-speed gated image intensifier with strong magnetic confinement, including the following steps:

[0046] Step 1: Install the image intensifier body at a preset position of the energized solenoid to form a high-speed gated image intensifier with strong magnetic confinement;

[0047] Step 2: Set the selectable voltage U set between the photocathode 13 and the input surface of the microchannel plate 2 to 5 V;

[0048] Step 3: Set the current of the energized solenoid to make the magnetic induction intensity of the magnetic field generated at any point between the photocathode 13 and the input surface of the microchannel plate 2 such that the high-speed gated image intensifier with strong magnetic confinement starts to image;

[0049] Step 4: The camera starts to expose and records the imaging result of the fluorescent screen of the image intensifier body.

Claims

1. A high-speed gated image intensifier with strong magnetic confinement, comprising an image intensifier body, wherein the image intensifier body includes an input window (11), a photocathode (13), a microchannel plate (2), a fluorescent screen (4) and an output window (12) arranged in sequence along the optical path propagation direction; the input window (11) includes an input surface and an output surface for transmitting optical signals; the photocathode (13) is plated on the output surface of the input window (11); the microchannel plate (2) includes an input surface and an output surface, on which a plurality of through holes are provided, and both the input surface and the output surface are plated with conductive metal films, and an electron filtering film (3) is also plated on the input surface; an optional voltage U is provided between the photocathode (13) and the input surface of the microchannel plate (2); the fluorescent screen (4) is arranged on the input surface of the output window (12), and there are intervals respectively between the microchannel plate (2) and the fluorescent screen (4), and between the photocathode (13) and the microchannel plate (2); It is characterized in that: The distance between the photocathode (13) and the input surface of the microchannel plate (2) is greater than or equal to 0.3 mm to 1.5 mm; An energized solenoid is arranged outside the image intensifier body.

2. The high-speed gated image intensifier with strong magnetic confinement according to claim 1, characterized in that: The image intensifier body is arranged in the middle of the energized solenoid, and the central axis of the image intensifier body along the optical path propagation direction coincides with the central axis of the energized solenoid.

3. The high-speed gated image intensifier with strong magnetic confinement according to claim 2, characterized in that: The magnetic induction intensity of the magnetic field generated by the energized solenoid at any point between the photocathode (13) and the input surface of the microchannel plate (2) of magnitude 4. The high-speed gated image intensifier with strong magnetic confinement according to claim 3, characterized in that: The gating amplitude of the voltage U is 5 V, and the gating pulse width is less than or equal to 800 ps.

5. The high-speed gated image intensifier with strong magnetic confinement according to claim 4, characterized in that: The distance between the output surface of the microchannel plate (2) and the fluorescent screen (4) is 0.5 mm to 0.6 mm.

6. The high-speed gated image intensifier with strong magnetic confinement according to claim 5, characterized in that: The microchannel plate (2) is a glass plate, and the diameter of each through hole on it is 6 μm to 10 μm.

7. The high-speed gated image intensifier with strong magnetic confinement according to claim 6, characterized in that: The phosphor of the fluorescent screen (4) is of type P20, P22, P43, P46 or P47, and the photocathode (13) is of type S20 or S25.

8. The high-speed gated image intensifier with strong magnetic confinement according to claim 7, characterized in that: The material of the electron filtering film (3) is Al2O3.

9. The high-speed gated image intensifier with strong magnetic confinement according to claim 8, characterized in that: The distance between the output surface of the microchannel plate (2) and the fluorescent screen (4) is 0.5 mm; the distance between the photocathode (13) and the input surface of the microchannel plate (2) is 0.3 mm; the diameter of each through hole on the microchannel plate (2) is 6 μm.

10. An imaging method for the high-speed gated image intensifier with strong magnetic confinement according to any one of claims 1 to 9, characterized in that, Including the following steps: Step 1: Install the intensifier body in the inner hole of the energized solenoid to form a strongly magnetically constrained high-speed gated image intensifier; Step 2: Set the voltage U to 5V to enable the strongly magnetically constrained high-speed gated image intensifier to start imaging; Step 3: Set the current of the energized solenoid to generate a magnetic field in the energized solenoid; Step 4: The camera starts to expose and records the imaging result of the fluorescent screen in the intensifier body.

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