An ultrafast high-resolution parallel readout single-photon detector and detection method

Abstract

The present invention relates to an ultrafast high-resolution parallel readout single-photon detector and a detection method, so as to solve the problem that the existing position-sensitive anode detector has low spatial resolution and cannot process overlapping events. The detector comprises a tube shell, an input window with a photocathode, a microchannel plate assembly, a semiconductor anode assembly and an image processing unit. The semiconductor anode assembly comprises a pixel charge collection electrode, a pixel charge readout electronic device, an insulating substrate and a lead electrode; the pixel charge readout electronic device comprises a plurality of pixel charge readout units arranged in an array, the pixel charge collection electrode comprises a plurality of image-sensitive units arranged in an array, and the image-sensitive unit is a pixelated single chip; each image-sensitive unit is connected to a corresponding pixel charge readout unit through a bump solder ball, each pixel charge readout unit is connected to one end of a corresponding lead electrode, and the other end of the lead electrode passes through the insulating substrate and is connected to the image processing unit.

Description

Technical Field

[0001] The present invention relates to the field of low-light level detection and imaging, and in particular to an ultrafast high-resolution parallel readout single-photon detector and a detection method. Background Art

[0002] In recent years, weak signal detection and imaging technology under low illumination conditions has become a hot topic of research in countries around the world due to its wide application background. Instruments and equipment related to weak signal detection and imaging technology have also become indispensable research tools and means in cutting-edge science and cutting-edge fields. The position-sensitive anode detector based on microchannel plate (MCP) is one of them.

[0003] The position-sensitive anode detector based on microchannel plate (MCP) converts weak light signals into electrical signals for amplification, and reads out through the position-sensitive anode with two-dimensional position resolution. The number of detected photons reflects the intensity of the target signal, and the spatial resolution of the position-sensitive anode determines the resolution of the image. According to the different decoding methods, the position-sensitive anode can be divided into impedance anode, charge-segmentation anode, delay line anode and cross anode. The impedance anode is affected by thermal charge noise, the charge-segmentation anode is limited by the number of anode divisions, and the delay line anode is severely crosstalked between electrodes, which limits the spatial resolution of the detector. In addition, the above-mentioned position-sensitive anode devices can only process one event at a time and cannot record events that occur at the same time.

[0004] The Chinese patent application number 201320307734.5 discloses a cross-position sensitive anode and detection system suitable for a microchannel plate detector, wherein the receiving anode is composed of upper and lower orthogonal rectangular cross conductive strips, each rectangular conductive strip independently outputs a charge signal, and the signal of each discrete electrode strip must be led out through a lead through an insulating substrate. As the detection area increases, the number of leads will become huge, and the corresponding readout circuit will also become large and complex. Therefore, the number of readout channels is limited, and only a small number of simultaneous events can be detected, which reduces the spatial resolution of the detector. In addition, overlapping events during charge collection and signal processing time cannot be decoded, resulting in a decrease in the detector count rate. Summary of the invention

[0005] In order to solve the problem that the existing position-sensitive anode detector has low spatial resolution and cannot process overlapping events, the present invention now provides an ultrafast high-resolution parallel readout single-photon detector and a detection method.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] An ultrafast high-resolution parallel readout single-photon detector comprises a tube shell, an input window, a microchannel plate assembly, a semiconductor anode assembly and an image processing unit; the input window and the semiconductor anode assembly are respectively arranged at the openings at both ends of the tube shell to form a vacuum sealed cavity; a photocathode is arranged on the inner side of the input window; the microchannel plate assembly is arranged in the vacuum sealed cavity; the special features thereof are:

[0008] The semiconductor anode assembly includes a pixel charge collection electrode, a pixel charge readout electronics, an insulating substrate, and a lead electrode;

[0009] The insulating base is sealed and connected to the tube shell;

[0010] The pixel charge readout electronic device is arranged inside the insulating substrate and includes a plurality of pixel charge readout units arranged in an array;

[0011] The pixel charge collection electrode is arranged inside the pixel charge readout electronic device, and includes a plurality of image sensitive units arranged in an array; the image sensitive unit is a pixelated single chip;

[0012] Each image sensitive unit is connected to a corresponding pixel charge readout unit through a bump solder ball; each pixel charge readout unit is connected to one end of a corresponding lead electrode, and the other end of the lead electrode passes through an insulating substrate and is connected to an image processing unit.

[0013] Further, the pixel charge readout unit includes an analog circuit and a digital circuit connected in sequence;

[0014] The analog circuit includes a charge-sensitive amplifier circuit and a comparator; the charge-sensitive amplifier circuit is used to integrate the charge collected by the image-sensitive unit to obtain the charge amount; the comparator is used to compare the charge amount with the threshold value to obtain a voltage pulse exceeding the threshold value, and the width of the voltage pulse is proportional to the collected charge amount;

[0015] The digital circuit includes a synchronous control logic circuit, a counter, a high-precision clock and a pixel readout circuit; the synchronous control logic circuit generates a trigger signal according to the voltage pulse of the comparator, and when the trigger signal is valid, the counter counts the voltage pulse time information output by the comparator according to the high-precision clock; the pixel readout circuit is used to read the counting result and output it to the image processing unit.

[0016] Further, the image processing unit includes at least one interface board, a digital processing board and a PC computer;

[0017] The input end of the interface board is connected to the lead electrode, and is used to convert the digital signal output by the pixel charge readout unit into a low-voltage differential signal, and transmit it to the digital processing board;

[0018] The digital processing board is used to reconfigure the low voltage differential signal and transmit it to a PC computer through an Ethernet interface for imaging.

[0019] Further, the pixelated monolithic chip is a silicon, gallium arsenide or cadmium telluride monolithic chip;

[0020] The pixel charge collection electrode includes N*N image sensitive units;

[0021] The material of the bump solder balls is solder.

[0022] Further, the tube shell shell comprises an indium sealing ring, a first ceramic ring, an MCP input electrode ring, a second ceramic ring, an MCP output electrode ring, a third ceramic ring and an anode sealing ring which are coaxially connected in sequence;

[0023] The indium sealing ring is provided with an indium sealing groove, and the input window is fixed in the indium sealing groove;

[0024] The microchannel plate assembly is installed between the MCP input electrode ring and the MCP output electrode ring, and an MCP pressure ring is provided between the input surface of the microchannel plate assembly and the MCP input electrode ring;

[0025] The insulating base is fixedly connected to the anode sealing ring through the anode positioning sealing ring.

[0026] Further, the distance between the cathode surface of the photocathode and the input surface of the microchannel plate assembly is 0.1-0.2 mm;

[0027] The microchannel plate assembly includes a single microchannel plate, two microchannel plates cascaded in a "V" shape, or three microchannel plates cascaded in a "Z" shape.

[0028] Furthermore, the input window is made of optical fiber panel, quartz, magnesium fluoride or K9 glass;

[0029] The photocathode is a S20 cathode, a S25 cathode, a CsTe cathode or a metal cathode.

[0030] An ultrafast high-resolution parallel readout single-photon detection method is special in that it includes the following steps:

[0031] 1) After the incident photon enters the input window of the ultrafast high-resolution parallel readout single-photon detector, it is converted into electrons by the photocathode;

[0032] 2) The electrons are accelerated into the microchannel plate assembly under the action of the external electric field formed by the photocathode and the semiconductor anode assembly; the microchannel plate assembly multiplies the electrons to form high-energy electrons;

[0033] 3) Under the constraint of an external electric field, high-energy electrons bombard the pixel charge collection electrode to generate electron-hole pairs. The electrons or holes are collected by the adjacent pixel charge collection electrode and bonded to the pixel charge readout electronic device through the bump solder ball;

[0034] 4) Each pixel charge readout unit of the pixel charge readout electronics counts the photons of the pixel charge;

[0035] 5) The counting results are transmitted to the image processing unit outside the vacuum through the lead electrodes for processing and imaging.

[0036] Furthermore, the step 4) is specifically implemented according to the following steps:

[0037] 4.1) The charge sensitive amplifier circuit of each pixel charge readout unit integrates the charge collected by the corresponding image sensitive unit to obtain the charge amount;

[0038] 4.2) Compare the charge amount with the threshold value of the comparator to obtain a voltage pulse that exceeds the threshold value and has a width proportional to the charge amount;

[0039] 4.3) When the trigger signal of the synchronous control logic circuit is valid, the counter counts the voltage pulse time information output by the comparator according to the high-precision clock;

[0040] 4.4) The pixel readout circuit reads the counting result and outputs it to the image processing unit.

[0041] Furthermore, the step 5) is specifically implemented according to the following steps:

[0042] 5.1) The counting results are transmitted to the interface board through the lead electrodes. The interface board converts the received digital signals into low voltage differential signals and transmits them to the digital processing board;

[0043] 5.2) The digital processing board reconfigures the low voltage differential signal and transmits it to the PC computer through the Ethernet interface for imaging.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] (1) The ultrafast high-resolution parallel readout single-photon detector provided by the present invention, through the combined design of the pixel charge collection electrode and the pixel charge readout electronic device in the semiconductor anode assembly, each image sensitive unit and the corresponding pixel charge readout unit form an independent counter, which can reach a GHz rate in the event counting mode and has a higher counting capacity. The detector can detect multiple events occurring simultaneously, directly encode and read out in parallel through the pixel charge readout electronic device, and can detect 10 at a time. 4 The above events.

[0046] (2) The noise level of the charge-sensitive amplifier circuit in the pixel charge readout unit is relatively low (typically 75e-rms), about 10 4 The output charge value of each electron is sufficient for low-noise detection of a single particle, which is 10-1000 times lower than the output noise of WSA anode and delay-line anode detectors. The low-noise pixel charge readout unit greatly reduces the gain of the microchannel plate required for incident particles. The reduction in gain significantly increases the local counting ability of the detector and is also conducive to extending the service life of the microchannel plate assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 1 is a schematic diagram of the structure of an embodiment of an ultrafast high-resolution parallel readout single-photon detector of the present invention (the image processing unit is not shown);

[0048] In the figure, 1-tube shell, 11-indium sealing ring, 12-first ceramic ring, 13-MCP input electrode ring, 14-second ceramic ring, 15-MCP output electrode ring, 16-third ceramic ring, 17-anode sealing ring, 18-anode positioning sealing ring, 2-input window, 3-photocathode, 4-microchannel plate assembly, 5-semiconductor anode assembly, 51-pixel charge collection electrode, 52-bump solder ball 53-pixel charge readout electronic device, 54-insulating substrate, 55-lead electrode.

[0049] Figure 2 It is a schematic diagram of the principle of using the ultrafast high-resolution parallel readout single-photon detector of the present invention for detection. DETAILED DESCRIPTION

[0050] In order to make the purpose, advantages and features of the present invention more clear, an ultrafast high-resolution parallel readout single-photon detector and a detection method proposed by the present invention are further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0051] like Figure 1 As shown in FIG. 1 , the ultrafast high-resolution parallel readout single-photon detector proposed in the present invention comprises a tube shell 1, an input window 2, a microchannel plate assembly 4, a semiconductor anode assembly 5 and an image processing unit. The input window 2 and the semiconductor anode assembly 5 are respectively arranged at the openings at both ends of the tube shell 1 to form a vacuum sealed cavity. The vacuum degree of the vacuum sealed cavity is 10 -6 The input window 2 is provided with a photocathode 3 inside, and a microchannel plate assembly 4 is provided in the vacuum sealed cavity and is located between the photocathode 3 and the semiconductor anode assembly 5 .

[0052] Specifically, the tube shell 1 includes an indium sealing ring 11, a first ceramic ring 12, an MCP input electrode ring 13, a second ceramic ring 14, an MCP output electrode ring 15, a third ceramic ring 16 and an anode sealing ring 17 which are coaxially connected in sequence.

[0053] An indium sealing groove is provided on the indium sealing ring 11, and the input window 2 is sealed and fixed in the indium sealing groove. The material of the input window 2 is an optical fiber panel, quartz, magnesium fluoride or K9 glass. The photocathode 3 is an S20 cathode, an S25 cathode, a CsTe cathode or a metal cathode, which can be selected according to the wavelength of the detector. The insulating substrate 54 of the photocathode 3 is made of 95% Al2O3 ceramic.

[0054] The microchannel plate assembly 4 is installed between the MCP input electrode ring 13 and the MCP output electrode ring 15, and an MCP pressure ring is provided between the input surface of the microchannel plate assembly 4 and the MCP input electrode ring 13. The distance between the cathode surface of the photocathode 3 and the input surface of the microchannel plate assembly 4 is 0.1-0.2 mm. The microchannel plate assembly 4 includes a single microchannel plate, two microchannel plates cascaded in a "V" shape, or three microchannel plates cascaded in a "Z" shape. The use of multiple cascaded microchannel plates is mainly used to improve the gain of the detector.

[0055] The semiconductor anode assembly 5 includes a pixel charge collection electrode 51 , a pixel charge readout electronics 53 , an insulating substrate 54 and a lead electrode 55 .

[0056] The insulating substrate 54 is made of 95% Al2O3 ceramic and is fixed by welding with the anode sealing ring 17 through the anode positioning sealing ring 18. The pixel charge readout electronic device 53 is arranged on the inner side of the insulating substrate 54, including N*N pixel charge readout units arranged in an array. The pixel charge collection electrode 51 is arranged on the inner side of the pixel charge readout electronic device 53, including N*N image sensitive units arranged in an array, and the image sensitive unit is a micron-level pixelated monolithic chip (silicon, gallium arsenide or cadmium telluride monolithic chip). Each image sensitive unit is connected to the corresponding pixel charge readout unit through a bump-bond ball 52 (bump-bonds ball), that is, bonded together through a solder material. Each pixel charge readout unit is connected to one end of the corresponding lead electrode 55, and the other end of the lead electrode 55 passes through the insulating substrate 54 and is connected to the image processing unit. Each image sensitive unit and the corresponding pixel charge readout unit form an independent counter, which can measure the object to be measured, count the photon energy or calculate the detected quantum time.

[0057] The distance between the output surface of the microchannel plate assembly 4 and the pixel charge collection electrode 51 of the semiconductor anode assembly 5 and the electric field therebetween determine the charge distribution between several pixels. At the output surface of the microchannel plate assembly 4, the charge is usually located in the range of about 6-30 microns, and event encoding can be performed with an accuracy of 1-2 pixels.

[0058] The pixel charge readout unit is an electronic chip that integrates analog circuits and digital circuits. The analog circuit includes a charge-sensitive amplifier circuit and a comparator. The charge-sensitive amplifier circuit is used to integrate the charge collected by the image-sensitive unit to obtain the charge amount. The comparator is used to compare the charge amount with the threshold value to obtain a voltage pulse that exceeds the threshold value. The width of the voltage pulse is proportional to the collected charge amount. The digital circuit includes a synchronous control logic circuit, a counter, a high-precision clock and a pixel readout circuit. The synchronous control logic circuit generates a trigger signal based on the voltage pulse of the comparator. When the trigger signal is valid, the counter counts the voltage pulse time information output by the comparator according to the high-precision clock. The pixel readout circuit is used to read the counting result and output it to the image processing unit.

[0059] The image processing unit includes at least one interface board, a digital processing board and a PC computer.

[0060] The interface board uses a field programmable gate array board, whose input end is connected to the lead electrode 55, and is used to convert the CMOS digital signal output by the pixel charge readout unit into a low voltage differential signal (LVDS) and transmit it to the digital processing board (FPGA board) through a coaxial cable. The digital processing board is used to reconfigure the low voltage differential signal and transmit it to a PC computer through a Gb Ethernet interface for imaging.

[0061] The above-mentioned ultrafast high-resolution parallel readout single-photon detector is used for low-light detection and imaging. The principle is as follows Figure 2 As shown, the specific steps include:

[0062] 1) After the incident photon enters the input window 2 of the detector, it is converted into electrons by the photocathode 3;

[0063] 2) The electrons are accelerated into the microchannel plate assembly 4 under the action of the external electric field formed by the photocathode 3 and the semiconductor anode assembly 5; the microchannel plate multiplies the electrons to form high-energy electrons;

[0064] 3) Under the constraint of the external electric field, high-energy electrons bombard the upper pixel charge collection electrode 51 to generate electron-hole pairs. The electrons or holes are collected by the adjacent pixel charge collection electrode 51 and bonded to the lower pixel charge readout electronic device 53 through the bump solder ball 52;

[0065] 4) Each pixel charge readout unit of the pixel charge readout electronics 53 counts the photons of the pixel charge and reads the entire image at a KHZ / frame rate;

[0066] 4.1) The charge sensitive amplifier circuit of each pixel charge readout unit integrates the charge collected by the corresponding image sensitive unit to obtain the charge amount;

[0067] 4.2) Compare the charge amount with the threshold value of the comparator to obtain a voltage pulse that exceeds the threshold value and has a width proportional to the charge amount;

[0068] 4.3) When the trigger signal of the synchronous control logic circuit is valid, the counter counts the voltage pulse time information output by the comparator according to the high-precision clock;

[0069] 4.4) The pixel readout circuit reads the counting result and outputs it to the image processing unit;

[0070] 5) The counting result is transmitted to the image processing unit outside the vacuum through the lead electrode 55 for processing and imaging;

[0071] 5.1) The counting result is transmitted to the interface board through the lead electrode 55, and the interface board converts the received digital signal into a low voltage differential signal and transmits it to the digital processing board;

[0072] 5.2) The digital processing board reconfigures the low voltage differential signal and transmits it to the PC computer through the Ethernet interface for imaging.

[0073] Higher MCP gain causes charge to spread over several pixels, which improves detection efficiency as more low-gain events appear above the readout threshold, thereby increasing the detector count rate. However, higher MCP gain results in a larger electron cloud area hitting the pixel charge collection electrode 51, which reduces the spatial resolution of the detector. Therefore, the MCP gain and semiconductor anode readout threshold (comparator threshold) levels should be adjusted between high count rate and high spatial resolution operating modes. At the same time, the duration acquisition frame needs to be adjusted for a given input event rate to prevent event overlap within a single frame.

Claims

1. An ultrafast high-resolution parallel readout single-photon detector, comprising a tube shell housing (1), an input window (2), a microchannel plate assembly (4), a semiconductor anode assembly (5) and an image processing unit; the input window (2) and the semiconductor anode assembly (5) are respectively arranged at the two end openings of the tube shell housing (1) to form a vacuum sealed cavity; a photocathode (3) is arranged on the inner side of the input window (2); the microchannel plate assembly (4) is arranged in the vacuum sealed cavity; characterized in that: The semiconductor anode assembly (5) comprises a pixel charge collection electrode (51), a pixel charge readout electronic device (53), an insulating substrate (54) and a lead electrode (55); The insulating base (54) is sealed and connected to the tube shell housing (1); The pixel charge readout electronic device (53) is arranged inside the insulating substrate (54) and includes a plurality of pixel charge readout units arranged in an array; The pixel charge collection electrode (51) is arranged inside the pixel charge readout electronic device (53), and comprises a plurality of image sensitive units arranged in an array; the image sensitive unit is a pixelated single chip; Each image sensitive unit is connected to a corresponding pixel charge readout unit via a bump solder ball (52); each pixel charge readout unit is connected to one end of a corresponding lead electrode (55), and the other end of the lead electrode (55) passes through an insulating substrate (54) and is connected to an image processing unit.

2. The ultrafast high-resolution parallel readout single-photon detector according to claim 1, characterized in that: The pixel charge readout unit includes an analog circuit and a digital circuit connected in sequence; The analog circuit includes a charge-sensitive amplifier circuit and a comparator; the charge-sensitive amplifier circuit is used to integrate the charge collected by the image-sensitive unit to obtain the charge amount; the comparator is used to compare the charge amount with the threshold value to obtain a voltage pulse exceeding the threshold value, and the width of the voltage pulse is proportional to the collected charge amount; The digital circuit includes a synchronous control logic circuit, a counter, a high-precision clock and a pixel readout circuit; the synchronous control logic circuit generates a trigger signal according to the voltage pulse of the comparator, and when the trigger signal is valid, the counter counts the voltage pulse time information output by the comparator according to the high-precision clock; The pixel readout circuit is used to read the counting result and output it to the image processing unit.

3. The ultrafast high-resolution parallel readout single-photon detector according to claim 2, characterized in that: The image processing unit includes at least one interface board, a digital processing board and a PC computer; The input end of the interface board is connected to the lead electrode (55) and is used to convert the digital signal output by the pixel charge readout unit into a low-voltage differential signal and transmit it to the digital processing board; The digital processing board is used to reconfigure the low voltage differential signal and transmit it to a PC computer through an Ethernet interface for imaging.

4. The ultrafast high-resolution parallel readout single-photon detector according to any one of claims 1 to 3, characterized in that: The pixelated monolithic chip is a silicon, gallium arsenide or cadmium telluride monolithic chip; The pixel charge collection electrode (51) comprises N*N image sensitive units; The material of the bump solder ball (52) is solder.

5. The ultrafast high-resolution parallel readout single-photon detector according to claim 4, characterized in that: The tube shell (1) comprises an indium sealing ring (11), a first ceramic ring (12), an MCP input electrode ring (13), a second ceramic ring (14), an MCP output electrode ring (15), a third ceramic ring (16) and an anode sealing ring (17) which are coaxially connected in sequence; The indium sealing ring (11) is provided with an indium sealing groove, and the input window (2) is fixed in the indium sealing groove; The microchannel plate assembly (4) is installed between the MCP input electrode ring (13) and the MCP output electrode ring (15), and an MCP pressure ring is provided between the input surface of the microchannel plate assembly (4) and the MCP input electrode ring (13); The insulating base (54) is fixedly connected to the anode sealing ring (17) via the anode positioning sealing ring (18).

6. The ultrafast high-resolution parallel readout single-photon detector according to claim 5, characterized in that: The distance between the cathode surface of the photocathode (3) and the input surface of the microchannel plate assembly (4) is 0.1-0.2 mm; The microchannel plate assembly (4) comprises a single microchannel plate, two microchannel plates cascaded in a "V" shape, or three microchannel plates cascaded in a "Z" shape.

7. The ultrafast high-resolution parallel readout single-photon detector according to claim 6, characterized in that: The input window (2) is made of optical fiber panel, quartz, magnesium fluoride or K9 glass; The photocathode (3) is a S20 cathode, a S25 cathode, a CsTe cathode or a metal cathode.

8. An ultrafast high-resolution parallel readout single-photon detection method, characterized in that: The following steps are involved: 1) After an incident photon enters the input window (2) of the ultrafast high-resolution parallel readout single-photon detector according to any one of claims 1 to 7, it is converted into an electron through the photocathode (3); 2) The electrons are accelerated into the microchannel plate assembly (4) under the action of the external electric field formed by the photocathode (3) and the semiconductor anode assembly (5); the microchannel plate assembly (4) multiplies the electrons to form high-energy electrons; 3) Under the constraint of an external electric field, high-energy electrons bombard the pixel charge collection electrode (51) to generate electron-hole pairs, and the electrons or holes are collected by the adjacent pixel charge collection electrode (51) and bonded to the pixel charge readout electronic device (53) through the bump solder ball (52); 4) each pixel charge readout unit of the pixel charge readout electronic device (53) performs photon counting on the pixel charge; 5) The counting result is transmitted to the image processing unit outside the vacuum through the lead electrode (55) for processing and imaging.

9. The ultrafast high-resolution parallel readout single-photon detection method according to claim 8, characterized in that: The step 4) is specifically implemented according to the following steps: 4.1) The charge sensitive amplifier circuit of each pixel charge readout unit integrates the charge collected by the corresponding image sensitive unit to obtain the charge amount; 4.2) Compare the charge amount with the threshold value of the comparator to obtain a voltage pulse that exceeds the threshold value and has a width proportional to the charge amount; 4.3) When the trigger signal of the synchronous control logic circuit is valid, the counter counts the voltage pulse time information output by the comparator according to the high-precision clock; 4.4) The pixel readout circuit reads the counting result and outputs it to the image processing unit.

10. The ultrafast high-resolution parallel readout single-photon detection method according to claim 9, characterized in that: The step 5) is specifically implemented according to the following steps: 5.1) The counting result is transmitted to the interface board through the lead electrode (55), and the interface board converts the received digital signal into a low voltage differential signal and transmits it to the digital processing board; 5.2) The digital processing board reconfigures the low voltage differential signal and transmits it to the PC computer through the Ethernet interface for imaging.

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