Pixelated probe

Abstract

This application discloses a pixel detector. Each pixel unit includes a local discrimination module that acquires a center pixel signal and compares it with a set local threshold for the center pixel to obtain a local discrimination signal for the center pixel; a global discrimination module that acquires a global discrimination signal for the center pixel; an arbitration module that determines whether the center pixel needs to be counted based on the above signals; and a counting module that increments the count by one when it needs to be counted, based on the result of the arbitration module. According to the technical solution provided by the embodiments of this application, by designing the pixel interconnection logic as a five-pixel interconnection, the counting judgment of the center pixel only needs to be performed through the other four pixels surrounding the center pixel, providing a simpler and more efficient implementation scheme.

Description

Technical Field

[0001] This invention generally relates to the field of detectors, and more particularly to pixel detectors. Background Technology

[0002] A detector is a signal acquisition system composed of a dedicated sensor array and its circuitry. As a device for acquiring information about new particles generated by particle reactions, it has wide applications in high-energy physics. Pixel detectors, in particular, play a crucial role in high-energy physics experimental detection systems due to their high integration and high positional resolution. Furthermore, pixel detectors can achieve high count rates and good energy resolution, thus finding wide applications in radiation detection and imaging fields beyond high-energy physics.

[0003] The so-called photon counting method is based on traditional nuclear electronics detection methods. It first integrates and amplifies the incident signal, then converts it into digital pulses using a threshold discrimination method, and finally accumulates these pulses using a counter to obtain the energy of the incident signal. Photon counting pixel detectors can not only greatly improve frame refresh rates but also achieve "zero-noise" imaging, thus gaining widespread application in various fields.

[0004] However, as the size of pixel detectors decreases to a certain extent, the energy resolution degrades due to charge sharing effects. During energy detection, the diameter of the positive and negative charge clusters generated in the sensor continuously increases as they drift towards the collector. This causes the charge spot on the collector plane to simultaneously hit several pixels instead of just one. In this case, the sum of the charges received by each pixel is the actual energy of the charge cluster. In photon counting detectors, the same charge spot distributed across different pixels may result in over-counting due to most charges exceeding the threshold, or under-counting due to the charges being relatively dispersed and below the threshold. Both situations reduce the detector's energy resolution, thus affecting its detection efficiency.

[0005] Existing technologies cannot handle low voltage conditions, resulting in significant application limitations. Furthermore, the interconnection between pixels is quite complex, requiring interconnection between seven pixels, which is cumbersome and redundant in practice. Summary of the Invention

[0006] In view of the above-mentioned defects or deficiencies in the prior art, it is desirable to provide a pixel detector.

[0007] In a first aspect, a pixel detector is provided, comprising multiple pixel units arranged in an array, wherein any three adjacent rows and three columns of pixel units constitute a module, and each pixel unit comprises: a local discrimination module, used to acquire a center pixel signal, compare the acquired center pixel signal with a set center pixel local threshold, and obtain a local discrimination signal of the center pixel;

[0008] The global discrimination module is used to acquire the center pixel signal and the signals of three adjacent pixels at one corner of the center pixel, and use them as the first pixel signal, the second pixel signal and the third pixel signal in sequence. The center pixel signal, the first pixel signal, the second pixel signal and the third pixel signal are superimposed and compared with the set total energy threshold of the center pixel to obtain the global discrimination signal of the center pixel.

[0009] The arbitration module is used to acquire the local discrimination signal of the center pixel, the local discrimination signal of the first pixel, the local discrimination signal of the second pixel, and the local discrimination signal of the third pixel, acquire the maximum value signal and the global discrimination signal of the fourth pixel, wherein the fourth pixel and the second pixel are located at opposite ends of the center pixel, and determine whether the center pixel needs to be counted based on the above signals;

[0010] The counting module is used to increment the count by one when a count is required, based on the result of the arbitration unit.

[0011] According to the technical solution provided in the embodiments of this application, by designing the pixel interconnection logic as a five-pixel interconnection, the counting and judgment of the center pixel only needs to be done through the other four pixels around the center pixel, which provides a simpler and more efficient implementation solution. Attached Figure Description

[0012] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0013] Figure 1 This is a schematic diagram of the pixel detector structure in this embodiment;

[0014] Figure 2 This is an extended schematic diagram of the pixel detector structure in this embodiment;

[0015] Figure 3 This is a schematic diagram of the arbitration module structure in this embodiment;

[0016] Figure 4 This is a schematic diagram of the pixel arrangement in this embodiment. Detailed Implementation

[0017] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0019] Please refer to Figure 1 This embodiment provides a pixel detector, including multiple pixel units arranged in an array. Any three adjacent rows and three columns of pixel units form a module. Each pixel unit includes: a local discrimination module 10, used to acquire a center pixel signal, compare the acquired center pixel signal with a set center pixel local threshold, and obtain a local discrimination signal of the center pixel.

[0020] The global discrimination module 20 is used to acquire the center pixel signal and the signals of three adjacent pixels at one corner of the center pixel, and use them as the first pixel signal, the second pixel signal and the third pixel signal in sequence. The center pixel signal, the first pixel signal, the second pixel signal and the third pixel signal are superimposed and compared with the set total energy threshold of the center pixel to obtain the global discrimination signal of the center pixel.

[0021] Arbitration module 30 is used to acquire the local discrimination signal of the center pixel, the local discrimination signal of the first pixel, the local discrimination signal of the second pixel, the local discrimination signal of the third pixel, the maximum value signal of the fourth pixel, and the global discrimination signal. The fourth pixel and the second pixel are located at opposite ends of the center pixel. Based on the above signals, it is determined whether the center pixel needs to be counted.

[0022] The counting module 40 is used to increment the count by one when a count is required, based on the result of the arbitration unit.

[0023] The pixel detector provided in this embodiment has multiple pixel units arranged in an array. When it is necessary to determine the counting information in a specific pixel unit, a module is formed by arranging pixels in a 3x3 grid around that pixel unit. The signals from each pixel unit within this module are used for judgment and calculation. Furthermore, by designing the pixel interconnection logic to interconnect five pixels, the counting judgment of the central pixel only requires the use of the other four pixels surrounding the central pixel, providing a simpler and more efficient implementation scheme. In this embodiment, the pixel detector consists of modules within each pixel. The aforementioned central pixel refers to the pixel currently requiring counting. The other pixels, such as the first pixel, second pixel, etc., refer to a subset of the eight pixels surrounding the central pixel. A specific pixel distribution diagram is shown below. Figure 4 As shown, the pixel that needs to be counted is the center pixel. The eight pixels surrounding the center pixel can be distinguished by the first pixel and the second pixel. Furthermore, they can be distinguished by their positional relationship with the center pixel, and are divided into east pixel, south pixel, west pixel, north pixel, southeast pixel, southwest pixel, northeast pixel, and northwest pixel. When the counting operation is performed, after the direction is determined, the counting operation of other pixels is also in the same direction as in this embodiment.

[0024] Each pixel that needs to be counted is a center pixel. Therefore, the signal of the center pixel is first acquired. The center pixel input signal undergoes two levels of processing: local discrimination and global discrimination. Finally, the two digital signals are combined with the digital signals of other adjacent pixels in the punching module to perform logical operations, thereby determining whether the group of pixels needs to perform an accumulation counting operation and the specific pixel position where the counting action needs to be performed.

[0025] The process begins by summing the center pixel signal with signals from three other pixels: the first, second, and third pixel signals. These three pixels are three adjacent pixels located at a corner of the center pixel. For example, the first pixel signal could be the north pixel signal, the second the northwest pixel signal, and the third the west pixel signal; or the first pixel signal could be the east pixel signal, the second the southeast pixel signal, and the third the south pixel signal, etc. The summed signal is then compared to the total energy threshold of the center pixel to obtain its global discrimination signal. Specifically, if the summed signal exceeds the threshold (i.e., greater than the total energy threshold of the center pixel), then a counting operation is required for this group of pixels, and the output global discrimination signal can be a high-level signal; otherwise, the output global discrimination signal is not high. The signal is a low-level signal. This global discrimination branch can reduce the over-counting problem of photon-counting detectors. It also includes comparing the center pixel signal with a local threshold to obtain the local discrimination signal. Specifically, if the center pixel signal exceeds the threshold (i.e., it is greater than the local threshold of the center pixel), the output local discrimination signal can be a high-level signal; otherwise, the output local discrimination signal is a low-level signal. Next, the global discrimination signal and the local discrimination signal are combined with the local discrimination signals of the first to third pixels, the global discrimination signal of the fourth pixel, and the maximum value signal in the arbitration module to perform certain logical operations. The fourth pixel is the pixel opposite to the second pixel. According to the above example, in the first case, the fourth pixel is the southeast pixel, and in the second case, the fourth pixel is the northwest pixel. Through the above logical operations, the position of the pixel that needs to be counted in the group of pixels is determined. This process can reduce the under-counting problem of photon-counting pixel detectors.

[0026] The global discrimination signal and maximum value signal of the aforementioned fourth pixel, such as the southeast pixel, come from the module in that pixel, specifically from the arbitration module inside that pixel unit, which will be explained in detail below.

[0027] The central pixel signal, first pixel signal, second pixel signal, and third pixel signal obtained by the global discrimination module are all amplified signals. Before the global discrimination module and the local discrimination module perform calculations, there is a signal amplification process. Therefore, the signals used here are all amplified signals, which will be explained in detail below.

[0028] When the size of pixel detectors is reduced to a certain extent, the current mainstream single pixel area size is 55um*55um, the charge sharing effect will gradually become obvious. This effect will have a more serious adverse effect on low energy signals, that is, when the input signal is small, greatly reducing its energy resolution and detection efficiency. For example, in a silicon pixel detector, when an 8keV photon signal is input, for ease of understanding, we will only discuss the case of energy equalization. Due to the charge sharing effect, it is possible that each of the four pixels receives 2keV of energy. In this case, the minimum energy resolution of the front-end circuit within the pixel unit must reach 2keV. This is equivalent to increasing the energy resolution requirement to four times. However, the 554e-electromagnetic charge, i.e., the smallest voltage signal, after the 2keV energy signal is converted, places almost an unrealistic requirement on the subsequent discrimination circuit. The circuit cannot recognize such a small voltage signal. Therefore, these small voltage signals will be submerged in noise lines and cannot produce the output signal of the digitization result. The low energy signal being submerged in noise signals directly results in the 8keV low energy signal being undetectable, which leads to the undercount phenomenon of photon counting detectors and thus reduces their detection efficiency.

[0029] Furthermore, the local discrimination module 10 includes a first voltage-to-current conversion unit 11, a first amplification unit 12, and a first comparison unit 13 connected in sequence;

[0030] The first voltage-to-current conversion unit 11 is used to convert the center pixel signal from a voltage signal into a current signal;

[0031] The first amplification unit 12 is used to amplify the converted current signal into a voltage signal;

[0032] The first comparison unit 13 is used to compare the amplified voltage signal with the set local threshold of the center pixel to obtain a local discrimination signal.

[0033] Due to the aforementioned issues of undercounting and difficulty in calculating small signals, this embodiment specifically incorporates a first voltage-to-current conversion unit within the local discrimination module. This unit converts the center pixel signal into a current signal, which is then amplified by a first amplification unit. In this way, the small voltage signal, whose energy was weakened by the charge-sharing effect, can be converted into a large voltage signal that can be distinguished by the local discrimination circuit. This facilitates further signal processing in subsequent circuit modules to obtain the local discrimination signal. The local discrimination module in this embodiment solves the problem of small signal input and enables the identification and manipulation of small voltage signals.

[0034] Furthermore, the global discrimination module 20 includes: a second voltage-to-current conversion unit 21, used to convert the center pixel signal from a voltage signal into a current signal;

[0035] The third current conversion unit 22 is used to acquire the first pixel signal, the second pixel signal and the third pixel signal, and convert the above signals from voltage signals to current signals;

[0036] The current superposition unit 23 is used to superimpose the converted center pixel signal, the first pixel signal, the second pixel signal, and the third pixel signal;

[0037] The second amplification unit 24 is used to amplify the superimposed current signal into a voltage signal;

[0038] The second comparison unit 25 is used to compare the amplified voltage signal with the set total energy threshold to obtain a global discrimination signal.

[0039] Due to the aforementioned issues of undercounting and difficulty in calculating small signals, this embodiment specifically incorporates a second voltage-to-current conversion unit and a third voltage-to-current conversion unit within the global discrimination module. These units convert the center pixel signal, the first pixel signal, the second pixel signal, and the third pixel signal into current signals for superposition. Directly superimposing the current signals is relatively simple. The signals are then amplified by a second amplification unit. This transforms the small voltage signal, weakened by the charge-sharing effect, into a large voltage signal that can be distinguished by the global discrimination module. This facilitates subsequent signal calculations in the circuit modules to obtain the global discrimination signal for the center pixel. Furthermore, the global discrimination module in this embodiment, besides addressing small input signals, employs a method of directly summing the current signals, greatly simplifying circuit design and implementation. This avoids further conversion between current and voltage signals and the use of integrating capacitors, reducing the complexity and redundancy of the overall circuit design for each pixel unit.

[0040] Furthermore, the arbitration module 30 includes a maximum value unit 31, used to acquire local discrimination signals of the center pixel, the first pixel, the second pixel, and the third pixel, and compare them to obtain the maximum value signal.

[0041] The first arithmetic unit 32 is used to acquire the maximum value signal and the global discrimination signal of the center pixel, perform a calculation, and obtain a first calculation result;

[0042] The second operation unit 33 is used to obtain the maximum value signal of the fourth pixel and the global discrimination signal of the fourth pixel and perform operations to obtain a second operation result;

[0043] The third arithmetic unit 34 is used to obtain the first arithmetic result and the second arithmetic result, perform a calculation to obtain a counting signal, and transmit the counting signal to the counting module.

[0044] In this embodiment, the arbitration module performs certain logical operations on the local discrimination signal and global discrimination signal of the center pixel and the signals of the other three pixels to determine the position of the pixel that needs to be counted in the group of pixels; the other three pixels mentioned above are the first to third pixels mentioned above.

[0045] like Figure 3 As shown, specifically, the arbitration module includes a maximum value unit. The local discrimination signal of the center pixel and the local discrimination signals of the three pixels adjacent to the center pixel are logically processed in the maximum value unit. If the local discrimination signal of the center pixel is the maximum value, the maximum value unit outputs a high-level signal; otherwise, if the local discrimination signal of the center pixel is not the maximum value, the maximum value unit outputs a low-level signal.

[0046] Subsequently, two processing units perform calculations. The first processing unit calculates the maximum value signal and the global discrimination signal of the center pixel. The second processing unit calculates the maximum value signal of the fourth pixel and the global discrimination signal of the fourth pixel. A third processing unit then performs a third calculation on the results of the two processing units to obtain the final counting signal. If the center pixel requires accumulation, the third processing unit generates a high-level signal, which is output to the counting module, and the counting module counts. Otherwise, the third processing unit generates a low-level signal, which is output to the calculation module, and the counting module does not count. In this embodiment, the second processing unit performs the calculation of the fourth pixel's maximum value signal and the global discrimination signal. This process eliminates some special scenarios. For example, if the center pixel is the outermost pixel, such as the top-left pixel, the signals of the north, west, and northwest pixels directly opposite the center pixel are all 0. Therefore, the results of the previous calculations and comparisons are also 0. In this case, the data of the fourth pixel (i.e., the southeast pixel) is needed so that the arbitration module can accurately determine the current status of the center pixel.

[0047] Furthermore, the maximum value unit 31 is specifically used to generate a high-level signal when the local discrimination signal of the center pixel is at its maximum value.

[0048] Otherwise, a low-level signal will be generated.

[0049] This embodiment details the calculation method of the maximum value unit, which is determined by the signals of four pixels. The implementation method is simple and easy to implement.

[0050] Furthermore, the maximum value unit 31 is also used to send the maximum value signal to the second pixel.

[0051] like Figure 2In this embodiment, each pixel is equipped with the aforementioned calculation module, and the pixels are interconnected for signal interaction. Therefore, the maximum value unit also sends the maximum value signal of the current center pixel to the second pixel so that the second pixel can use this maximum value signal for calculation and judgment. For example, when the second pixel is the northwest pixel, the maximum value signal of the center pixel is sent to the northwest pixel, making the northwest pixel the center pixel. In this case, the current center pixel becomes the southeast pixel of the northwest pixel. Therefore, when the northwest pixel is the center pixel, the arbitration module needs to use the maximum value signal of the southeast pixel for calculation. The above process illustrates the signal interconnection between the pixels.

[0052] Furthermore, the first arithmetic unit, the second arithmetic unit, and the third arithmetic unit are NAND gates.

[0053] In this embodiment, a NAND gate is used as the logic gate for the above-mentioned operation unit. Other logic gates can also be used, which can be selected according to the actual situation, such as NOR gate, XNOR gate, etc.

[0054] Furthermore, it also includes a charge amplification module for acquiring and amplifying the center pixel signal, and transmitting the amplified center pixel signal to the local discrimination module and the global discrimination module.

[0055] In this embodiment, a first-stage amplification is performed before the signal from the central pixel is transmitted to the local and global discrimination modules. This allows the small voltage signal, weakened by the charge-sharing effect, to be converted into a large voltage signal by the respective currents of the local or global discrimination modules, facilitating subsequent signal calculations in the circuit modules. Furthermore, when the current pixel unit interacts with surrounding pixel units, the signal transmitted is also amplified by the first stage of this charge amplification module, facilitating signal recognition and calculation within both the current and surrounding pixel units. Specifically, as shown... Figure 1 As shown, the center pixel signal sent by the local discrimination module is the center pixel signal amplified by the charge amplification module. The first pixel signal, the second pixel signal, and the third pixel signal obtained by the third voltage-current conversion unit in the global discrimination module are all signals amplified by the charge amplification module of each pixel unit.

[0056] Furthermore, the local discrimination module is also used to: send the magnified center pixel signal and the local discrimination signal of the center pixel to the fourth pixel, the fifth pixel and the sixth pixel, wherein the fifth pixel and the sixth pixel are pixels that are adjacent to both the center pixel and the fourth pixel.

[0057] like Figure 2As shown, in order to realize the communication connection between each pixel, the local discrimination module sends the local discrimination signal of the current center pixel to the fourth, fifth and sixth pixels, so that when the fourth, fifth and sixth pixels are used as the center pixel for calculation, the signal value of the current center pixel needs to be used. The fifth and sixth pixels are adjacent to the center pixel and the fourth pixel, respectively. Therefore, the fourth to sixth pixels and the first to third pixels are located at two opposite corners of the center pixel.

[0058] Furthermore, the global discrimination module is also used to send the global discrimination signal of the center pixel to the second pixel.

[0059] like Figure 2 As shown, in this embodiment, the global discrimination module also sends the global discrimination signal of the center pixel to the second pixel. For example, when the second pixel is the northwest pixel, the global discrimination signal of the center pixel is sent to the northwest pixel, so that when the northwest pixel is the center pixel, the current center pixel becomes the southeast pixel of the aforementioned northwest pixel. Therefore, when the aforementioned northwest pixel is the center pixel, the arbitration module needs to use the global discrimination signal of the southeast pixel for calculation. The above process illustrates the signal interconnection between each pixel.

[0060] This embodiment uses a simple approach to solve the charge sharing effect. The overall implementation of this scheme is simple, requiring only the signals of the center pixel and the four surrounding pixels. It can also solve the extreme case of small signal input, enabling counting even with small signal input.

[0061] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A pixel detector, comprising an array of multiple pixel units, wherein any three adjacent rows and three columns of pixel units constitute a module, characterized in that, Each pixel unit includes: a local discrimination module, used to acquire a center pixel signal, compare the acquired center pixel signal with a set center pixel local threshold, and obtain a local discrimination signal for the center pixel; The global discrimination module is used to acquire the center pixel signal and the signals of three adjacent pixels at one corner of the center pixel, and use them as the first pixel signal, the second pixel signal and the third pixel signal in sequence. The center pixel signal, the first pixel signal, the second pixel signal and the third pixel signal are converted from voltage signals to current signals, superimposed and compared with the set total energy threshold of the center pixel to obtain the global discrimination signal of the center pixel. The arbitration module is used to acquire the local discrimination signal of the center pixel, the local discrimination signal of the first pixel, the local discrimination signal of the second pixel, and the local discrimination signal of the third pixel, acquire the maximum value signal and the global discrimination signal of the fourth pixel, wherein the fourth pixel and the second pixel are located at opposite ends of the center pixel, and determine whether the center pixel needs to be counted based on the above signals; The counting module is used to increment the count by one when a count is required, based on the result of the arbitration unit. The local discrimination module includes a first voltage-to-current conversion unit, a first amplification unit, and a first comparison unit connected in sequence. The first voltage-to-current conversion unit is used to convert the center pixel signal from a voltage signal into a current signal; The first amplification unit is used to amplify the converted current signal into a voltage signal; The first comparison unit is used to compare the amplified voltage signal with a set local threshold of the center pixel to obtain a local discrimination signal.

2. The pixel detector according to claim 1, characterized in that, The global discrimination module includes: a second voltage-to-current conversion unit, used to convert the center pixel signal from a voltage signal to a current signal; The third current conversion unit is used to acquire the first pixel signal, the second pixel signal and the third pixel signal, and convert the above signals from voltage signals to current signals; The current superposition unit is used to superimpose the converted center pixel signal, the first pixel signal, the second pixel signal, and the third pixel signal; The second amplification unit is used to amplify the superimposed current signal into a voltage signal; The second comparison unit is used to compare the amplified voltage signal with the set total energy threshold to obtain a global discrimination signal.

3. The pixel detector according to claim 1, characterized in that, The arbitration module includes a maximum value unit, used to acquire local discrimination signals of the center pixel, the first pixel, the second pixel, and the third pixel, and compare them to obtain the maximum value signal. The first processing unit is used to perform calculations on the maximum value signal and the global discrimination signal of the center pixel to obtain a first calculation result; The second processing unit is used to obtain the maximum value signal of the fourth pixel and the global discrimination signal of the fourth pixel, perform calculations, and obtain a second processing result. The third arithmetic unit is used to obtain the first arithmetic result and the second arithmetic result, perform a calculation to obtain a counting signal, and transmit the counting signal to the counting module.

4. The pixel detector according to claim 3, characterized in that, The maximum value unit is specifically used to generate a high-level signal when the local discrimination signal of the center pixel is at its maximum value. Otherwise, a low-level signal will be generated.

5. The pixel detector according to claim 3, characterized in that, The maximum value unit is also used to send the maximum value signal to the second pixel.

6. The pixel detector according to claim 3, characterized in that, The first arithmetic unit, the second arithmetic unit, and the third arithmetic unit are NAND gates.

7. The pixel detector according to any one of claims 1-6, characterized in that, It also includes a charge amplification module, which is used to acquire and amplify the center pixel signal, and transmit the amplified center pixel signal to the local discrimination module and the global discrimination module.

8. The pixel detector according to claim 7, characterized in that, The local discrimination module is further configured to: send the amplified center pixel signal and the local discrimination signal of the center pixel to the fourth pixel, the fifth pixel and the sixth pixel, wherein the fifth pixel and the sixth pixel are pixels that are adjacent to both the center pixel and the fourth pixel.

9. The pixel detector according to claim 7, characterized in that, The global discrimination module is also used to send the global discrimination signal of the center pixel to the second pixel.

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