X-ray precise position sensor and method based on combined reading electrode and gating weight reading algorithm

Abstract

The invention discloses an X-ray precise position sensor and method based on a combined reading electrode and a gating weight reading algorithm. Comprising an energy conversion layer, one side surface of which is provided with a plurality of bias electrodes, the opposite side surface of which is provided with a plurality of detector pixel units and detector readout electrodes, and the detector pixel units are correspondingly aligned with the bias electrodes; the detector pixel units are arranged according to a rectangular array, four corners of each detector pixel unit are respectively provided with a detector read-out electrode, and the four detector read-out electrodes are electrically connected with the detector pixel units; each detector pixel unit comprises four charge collecting electrodes which are arranged according to a 2 * 2 rectangular array, and the four charge collecting electrodes are electrically connected with the four detector reading electrodes in a one-to-one correspondence mode. According to the invention, under the condition that the electrode manufacturing process is not reduced, the position detection precision can be improved through the combination of the reading electrode and the gating weight reading algorithm, and the detection precision of the detector is improved under the same cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of X-ray position detection sensors, and in particular to a precision position sensor based on a specific electrode distribution mode and a gated weight readout algorithm. BACKGROUND

[0002] In the field of X-ray imaging technology, detector performance continues to improve, but in the pursuit of higher spatial resolution, traditional detector structures face many technical challenges. The following is a background technical analysis of traditional X-ray detectors under the trend of micro-pixelization.

[0003] Currently, many X-ray detectors use a parallel plate electrode structure, that is, a large-area uniform bias electrode and a charge collection electrode are placed parallel to each other and one-to-one. Under this structure, the pixel size directly determines the physical limit of imaging resolution. When the process advances to reduce the pixel size to about 200 microns or less, the following significant problems will arise: 1. Electric field instability: The reduction of pixel size will exacerbate the edge effect of the electric field, leading to uneven distribution of the electric field. In the study of, it is also observed that in a similar pixel array detector, there may be a relatively high potential area inside the material, causing the electric field distribution to be distorted. This distortion will interfere with the directional drift of signal charges, introducing measurement errors.

[0004] 2. Increased noise: Micro-pixels significantly reduce the amount of initial signal charge collected by each cell, degrading the signal-to-noise ratio (SNR). At the same time, the study of points out that in X-ray imaging, quantum noise is one of the key factors limiting the performance of the detector, especially under micro-pixels. To handle weak signals, the readout circuit needs higher gain, which at the same time amplifies the noise of the circuit itself 3. Increased signal crosstalk: The reduction of pixel pitch will enhance the electromagnetic coupling between adjacent pixels, leading to charge sharing and signal crosstalk. In the study of high-resolution X-ray detectors, it was found that the lateral scattering of fluorescence and crosstalk would seriously affect the imaging quality. Although this study suppressed this phenomenon through pixelated conversion screens and other structures, it precisely illustrates the serious crosstalk challenge faced by traditional structures under micro-pixels.

[0005] 4. Increased complexity and cost of readout electronics: The increase in the number of pixels directly leads to an increase in the number of readout channels. Each channel requires an independent signal processing link (such as an amplifier, an analog-to-digital converter), significantly increasing system power consumption, wiring complexity, and cost. At the same time, the design of the synchronization control and data acquisition system driving a large number of channels also becomes more complex.

[0006] The above problems are interrelated and form a bottleneck restricting the performance improvement of the detector. For example, a more complex electrode structure or driving mode may be needed to stabilize the electric field, which in turn increases the process difficulty and cost. Therefore, in the traditional one-to-one electrode structure framework, further reducing the pixel size can nominally improve the theoretical resolution, but due to the above disadvantages, the overall imaging performance (such as signal-to-noise ratio under low illumination, image uniformity) and economy of the detector will be significantly reduced.

[0007] In summary, there is an urgent need for a new type of detector electrode structure and readout method that can fundamentally improve the charge collection efficiency under micro-pixels, suppress crosstalk, and balance the complexity of readout electronics. SUMMARY

[0008] In view of the deficiencies of the prior art, the present application proposes an X-ray precision position sensor and method based on joint readout electrodes and gated weight readout algorithm. The purpose of the present application is to provide a joint readout electrode design that distributes the charge signal of a single pixel to multiple readout channels without significantly increasing the complexity and cost of the detector process. Then, a special signal processing algorithm is used to reconstruct and analyze the distributed signal, thereby breaking through the precision bottleneck of traditional single electrode readout at the root, and significantly improving the overall measurement accuracy and resolution of the X-ray detector.

[0009] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: I. An X-ray precision position sensor based on joint readout electrodes and gated weight readout algorithm The X-ray precision position sensor comprises: an energy conversion layer; a plurality of bias poles arranged on a first side surface of the energy conversion layer; a plurality of detector pixel units and a plurality of detector readout electrodes arranged on a second side surface opposite to the first side of the energy conversion layer; the number of detector pixel units is the same as that of bias poles and they are arranged in one-to-one correspondence; The detector pixel units are arranged in a rectangular array, and a detector gap is formed between adjacent detector pixel units. A detector readout electrode is arranged at the intersection of the detector gap, so that each detector pixel unit has one detector readout electrode at each corner, and the four detector readout electrodes are electrically connected to the detector pixel unit. The detector pixel unit comprises four charge collection electrodes arranged in a 2x2 rectangular array, and the four charge collection electrodes are electrically connected to the four detector readout electrodes in one-to-one correspondence.

[0010] In each detector pixel unit, the charge collection signals of the four charge collection electrodes are collected by the respective corresponding detector readout electrodes.

[0011] For any four detector pixel units arranged in a 2×2 rectangular array, a detector readout electrode is arranged at the geometric center of the four detector pixel units. The detector readout electrode is electrically connected to the four detector pixel units and to the charge collection electrode closest to itself in each detector pixel unit. Each detector readout electrode reads the total charge collection signal of the four charge collection electrodes.

[0012] The detector readout electrode is electrically connected to the charge collection electrode via a conductive lead.

[0013] The position sensor also includes a data processing unit, which is electrically and / or communicatively connected to the readout electrode of each detector. The data processing unit includes a position calculation module. The position calculation module uses a weighted calculation method to obtain the charge collection signal weight of each charge collection electrode based on the charge collection signals of the four charge collection electrodes in the hit detector pixel unit. Combined with the position vector of the center of the detector pixel unit pointing to the center of each charge collection electrode, the position vector of the center of the detector pixel unit pointing to the X-ray hit point is obtained.

[0014] In the position calculation module, the charge collection signal weight is obtained using any of the following formulas: Formula a: Formula b: In the formula, This represents the charge collection signal weight of the i-th charge collection electrode in the detector pixel unit; This represents the charge collection signal of the i-th charge collection electrode in the detector pixel unit.

[0015] The data processing unit includes a hit identification module; the hit identification module processes the time-domain readout signals of each detector readout electrode using a coupled time window method to identify X-ray hit events and the hit detector pixel units.

[0016] II. A position sensing method using the above-mentioned X-ray precision position sensor The position sensing method includes the following steps: By using the coupled time window method and combining it with a preset gate time, the time-domain readout signals of each detector readout electrode, i.e., the analog waveform signals, are processed to identify X-ray hit events and the hit detector pixel units. For each detector pixel unit that is hit, the readout signal of each detector readout electrode electrically connected to the detector pixel unit within the same gate time is used as the charge collection signal of the charge collection electrode electrically connected to the detector readout electrode. Based on the charge collection signals from the four charge collection electrodes, the charge collection signal weights of each electrode are obtained. Then, the X-ray impact location is determined using the following formula: In the formula, This represents the position vector from the center of the detector pixel unit to the point where the X-ray hits. This represents the position vector from which the center of the detector pixel unit points to the center of the i-th charge collection electrode. This represents the charge collection signal weight of the i-th charge collection electrode in the detector pixel unit; the charge collection signal weight refers to the weight of the charge collection signal of the charge collection electrode in the charge collection signals of the four charge collection electrodes.

[0017] The charge collection signal weights can be obtained using any of the following formulas: Formula a: Formula b: In the formula, This represents the charge collection signal weight of the i-th charge collection electrode in the detector pixel unit; This represents the charge collection signal of the i-th charge collection electrode in the detector pixel unit.

[0018] The charge signals of the four charge collection electrodes in each detector pixel unit are received by the four detector readout electrodes respectively. If there is a set of arrival times with a maximum time difference less than the gate time in the time domain readout signals of the four detector readout electrodes, it is determined that the detector pixel unit has been hit by an X-ray, and the detector pixel unit is regarded as the hit detector pixel unit for subsequent positioning calculation.

[0019] The beneficial effects of this invention are: It can greatly improve the spatial resolution limit of the detector without changing the pixel size; It can increase spatial resolution without reducing the signal-to-noise ratio; Because the size of the equivalent electrode was not reduced, the electric field stability was not increased; While increasing spatial resolution, the number of readout electronics channels is not increased, thus reducing costs; Multi-channel coincidence readout helps reduce the spurious event rate. Attached Figure Description

[0020] Figure 1 This is a cross-sectional view of a pixel unit in a traditional detector.

[0021] Figure 2 This is a pixel unit distribution diagram of a traditional detector.

[0022] Figure 3 This is a cross-sectional view of the detector pixel unit of the present invention.

[0023] Figure 4 This is a pixel unit distribution diagram of the detector of the present invention.

[0024] Figure 5 This is a schematic diagram of single-pixel readout of the present invention.

[0025] In the figure: 1. Bias electrode, 2. Energy conversion layer, 3. Charge collection electrode, 4. Traditional detector pixel unit, 5. Traditional detector pixel unit gap, 6. Detector pixel unit, 7. Detector gap, 8. Detector readout electrode, 9. Charge collection electrode. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] First, such as Figure 1 and Figure 2 As shown, a conventional X-ray detector applies a bias voltage between the bias electrode 1 and the charge collection electrode 3. When an X-ray strikes the energy conversion layer 2 (typically a semiconductor material), there is a probability of generating electron-hole pairs within the energy conversion layer 2. These electron-hole pairs are collected by the corresponding charge collection electrode 3 under the bias voltage. The ratio of collected charge to generated charge is generally greater than 1, depending on the magnitude of the bias voltage. In imaging, each conventional detector pixel unit 4 consists of a corresponding set of bias electrodes 1 and charge collection electrodes 3. The quality of each pixel is determined by the performance of the corresponding bias electrodes 1 and charge collection electrodes 3. Pixel signal readout occurs directly between the corresponding bias electrodes 1 and charge collection electrodes 3. There are no other materials or structures in the pixel unit gaps 5 of a conventional detector.

[0028] This invention provides an X-ray precision position sensor based on a joint readout electrode and a gated weighted readout algorithm. In this invention, adjacent electrodes between the charge collecting electrode and the bias electrode are jointly read out, with each bias electrode forming a collecting electric field with its neighboring collecting electrode. The charge in the region corresponding to each bias electrode is collected by the adjacent collecting electrodes, and the X-ray impact position is calculated using a gated weighted readout algorithm.

[0029] Compared to traditional X-ray detectors, in this invention, a single detector pixel unit 6 consists of a bias electrode 1 and four separate charge collection electrodes 9. The charge generated by each detector pixel unit 6 is collected by the corresponding four charge collection electrodes 9. Signal magnitude calculation... , , , The four adjacent charge collection electrodes 9 are read out uniformly by the detector readout electrodes 8 placed in the detector gap 7. This achieves further subdivision of pixels without changing the number of readout electrons. This invention doubles the physical upper limit of linear resolution and quadruples the physical upper limit of planar resolution.

[0030] like Figure 3 and Figure 4 As shown, the X-ray precision position sensor provided by this invention includes: Energy conversion layer 2; Several bias electrodes 1 are arranged on the first side surface of the energy conversion layer 2; A number of detector pixel units 6 and a number of detector readout electrodes 8 are arranged on the second side surface of the energy conversion layer 2 opposite to the first side; the number of detector pixel units 6 is the same as that of bias electrodes 1 and they are arranged in a one-to-one correspondence.

[0031] The detector pixel units 6 are evenly arranged in a rectangular array, and a detector gap 7 is formed between adjacent detector pixel units 6. A detector readout electrode 8 is arranged at the intersection of the detector gap 7, so that a detector readout electrode 8 is arranged at each of the four corners of each detector pixel unit 6, and all four detector readout electrodes 8 are electrically connected to the detector pixel unit 6.

[0032] The detector pixel unit 6 includes four charge collection electrodes 9 evenly arranged in a 2×2 rectangular array. Each of the four charge collection electrodes 9 corresponds one-to-one with a detector readout electrode 8, and each charge collection electrode 9 is electrically connected to its corresponding detector readout electrode 8. In each detector pixel unit 6, the charge collection signals of the four charge collection electrodes 9 are collected by their respective detector readout electrodes 8.

[0033] For any four detector pixel units 6 arranged in a 2×2 rectangular array, a detector readout electrode 8 is arranged at the geometric center of the four detector pixel units 6. The detector readout electrode 8 is electrically connected to the four detector pixel units 6 and to the charge collection electrode 9 closest to itself in each detector pixel unit 6.

[0034] Each detector readout electrode 8 reads the total charge collection signal from the four charge collection electrodes 9. In practice, the probability of four adjacent pixel units 6 connected to a detector readout electrode 8 being hit simultaneously within the same gating time is extremely low. Therefore, any valid signal on each detector readout electrode 8 can be regarded as the charge signal generated by the event of a detector pixel unit 6 being hit.

[0035] Optionally, the detector readout electrode 8 is electrically connected to the charge collection electrode 9 via a conductive lead.

[0036] Furthermore, the position sensor also includes a data processing unit, which is electrically and / or communicatively connected to each detector readout electrode 8.

[0037] Specifically, the data processing unit includes a location calculation module.

[0038] The position calculation module uses a weighted calculation method to obtain the charge collection signal weight of each charge collection electrode 9 based on the charge collection signals of the four charge collection electrodes 9 in the hit detector pixel unit 6. Combined with the position vector of the geometric center of the detector pixel unit 6 pointing to the center of each charge collection electrode 9, the position vector of the geometric center of the detector pixel unit 6 pointing to the X-ray hit point is obtained.

[0039] In the position calculation module, the charge collection signal weights are obtained using any of the following formulas: Formula a: Formula b: In the formula, This represents the charge collection signal weight of the i-th charge collection electrode 9 in the detector pixel unit 6; This represents the charge collection signal of the i-th charge collection electrode 9 in the detector pixel unit 6.

[0040] Specifically, the data processing unit includes a hit identification module; the hit identification module processes the time-domain readout signals of each detector readout electrode 8 using a coupled time window method to identify X-ray hit events and the hit detector pixel units 6.

[0041] The present invention also provides a position sensing method using the above-mentioned X-ray precision position sensor.

[0042] like Figure 5 As shown, in the position sensing method provided by this invention, the same gate time will be used. The charge collection signal generated by the detector pixel unit 6 is calculated. , , , Among them, the gating time The length will be determined by the pixel size and the X-ray time rate. Let the position vectors pointing from the pixel center O to the center of each charge collector 9 be respectively: , , , The signal position given by the weighting algorithm is: Among them, weighting factors It is the weight of the charge signal read from the different charge collection electrodes 9 of the detector pixel unit 6.

[0043] To address varying levels of implementation difficulty, this invention proposes several different weight calculation methods: Method 1: Method 2: Both of these methods can significantly improve spatial resolution.

[0044] The position sensing method provided by this invention includes the following steps: By using the coupled time window method and combining the preset gate time, the time domain readout signal of each detector readout electrode 8 is processed, i.e., the analog waveform signal, to identify the X-ray hit event and the hit detector pixel unit 6. For each hit detector pixel unit 6, the readout signal of each detector readout electrode 8 electrically connected to the detector pixel unit 6 within the same gate time is used as the charge collection signal of the charge collection electrode 9 electrically connected to the detector readout electrode 8. Based on the charge collection signals from the four charge collection electrodes 9, the charge collection signal weights of each charge collection electrode 9 are obtained, and then the X-ray impact location is determined using the following formula: In the formula, This represents the position vector pointing from the geometric center of detector pixel unit 6 to the point of X-ray impact. This represents the position vector pointing from the geometric center of detector pixel unit 6 to the center of the i-th charge collection electrode 9. This represents the charge collection signal weight of the i-th charge collection electrode 9 in the detector pixel unit 6; the charge collection signal weight refers to the weight of the charge collection signal of the charge collection electrode 9 in the charge collection signals of the four charge collection electrodes 9.

[0045] The charge collection signal weights can be obtained using any of the following formulas: Formula a: Formula b: In the formula, This represents the charge collection signal weight of the i-th charge collection electrode 9 in the detector pixel unit 6; This represents the charge collection signal of the i-th charge collection electrode 9 in the detector pixel unit 6.

[0046] The charge signals of the four charge collection electrodes 9 in each detector pixel unit 6 are received by the four detector readout electrodes 8 respectively. If there is a set of arrival times in the time domain readout signals of the four detector readout electrodes 8 with a maximum time difference less than the gate time, it is determined that the detector pixel unit 6 has been hit by an X-ray, and the detector pixel unit 6 is regarded as the hit detector pixel unit 6 for subsequent positioning calculation.

[0047] The above specific embodiments are used to explain and illustrate the present invention, but not to limit the present invention. Any modifications and changes made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. An X-ray precision position sensor based on a joint readout electrode and a gated weighted readout algorithm, characterized in that, include: Energy conversion layer (2); Several bias electrodes (1) are arranged on the first side surface of the energy conversion layer (2); A number of detector pixel units (6) and detector readout electrodes (8) are arranged on the second side surface of the energy conversion layer (2) opposite to the first side; the number of detector pixel units (6) is the same as that of the bias electrode (1) and they are arranged in a one-to-one correspondence. The detector pixel units (6) are arranged in a rectangular array at intervals, and a detector gap (7) is formed between adjacent detector pixel units (6). A detector readout electrode (8) is arranged at the intersection of the detector gap (7). A detector readout electrode (8) is arranged at each of the four corners of each detector pixel unit (6). All four detector readout electrodes (8) are electrically connected to the detector pixel unit (6). The detector pixel unit (6) includes four charge collection electrodes (9) arranged in a 2×2 rectangular array, and the four charge collection electrodes (9) are electrically connected to the four detector readout electrodes (8) respectively.

2. The X-ray precision position sensor based on joint readout electrodes and gated weighted readout algorithm according to claim 1, characterized in that: In each detector pixel unit (6), the charge collection signals of the four charge collection electrodes (9) are collected by their respective detector readout electrodes (8).

3. The X-ray precision position sensor based on joint readout electrodes and gated weighted readout algorithm according to claim 2, characterized in that: For any four detector pixel units (6) arranged in a 2×2 rectangular array, a detector readout electrode (8) is arranged at the geometric center of the four detector pixel units (6). The detector readout electrode (8) is electrically connected to the four detector pixel units (6) and to the charge collection electrode (9) closest to itself in each detector pixel unit (6). Each detector readout electrode (8) reads the total charge collection signal of the four charge collection electrodes (9).

4. The X-ray precision position sensor based on joint readout electrodes and gated weighted readout algorithm according to claim 1, characterized in that: The detector readout electrode (8) is electrically connected to the charge collection electrode (9) via a conductive lead.

5. The X-ray precision position sensor based on joint readout electrodes and gated weighted readout algorithm according to claim 1, characterized in that: The position sensor also includes a data processing unit, which is electrically and / or communicatively connected to each detector readout electrode (8); The data processing unit includes a position calculation module. The position calculation module uses a weighted calculation method to obtain the charge collection signal weight of each charge collection electrode (9) based on the charge collection signals of the four charge collection electrodes (9) in the hit detector pixel unit (6). Combined with the position vector of the center of the detector pixel unit (6) pointing to the center of each charge collection electrode (9), the position vector of the center of the detector pixel unit (6) pointing to the X-ray hit point is obtained.

6. The X-ray precision position sensor based on joint readout electrodes and gated weighted readout algorithm according to claim 5, characterized in that: In the position calculation module, the charge collection signal weight is obtained using any of the following formulas: Formula a: Formula b: In the formula, This represents the charge collection signal weight of the i-th charge collection electrode (9) in the detector pixel unit (6); This represents the charge collection signal of the i-th charge collection electrode (9) in the detector pixel unit (6).

7. The X-ray precision position sensor based on joint readout electrodes and gated weighted readout algorithm according to claim 5, characterized in that: The data processing unit includes a hit identification module; the hit identification module processes the time-domain readout signals of each detector readout electrode (8) using a coupled time window method to identify X-ray hit events and the hit detector pixel units (6).

8. A position sensing method using an X-ray precision position sensor as described in any one of claims 1 to 7, characterized in that, Includes the following steps: By using the coupled time window method and combining the preset gate time, the time domain readout signals of each detector readout electrode (8) are processed to identify the X-ray hit event and the hit detector pixel unit (6). For each detector pixel unit (6) that is hit, the readout signal of each detector readout electrode (8) electrically connected to the detector pixel unit (6) within the same gate time is used as the charge collection signal of the charge collection electrode (9) electrically connected to the detector readout electrode (8). Based on the charge collection signals from the four charge collection electrodes (9), the charge collection signal weights of each charge collection electrode (9) are obtained, and the X-ray impact location is determined using the following formula: In the formula, This represents the position vector of the center of the detector pixel unit (6) pointing to the point where the X-ray hits. This represents the position vector of the center of the detector pixel unit (6) pointing towards the center of the i-th charge collection electrode (9). This represents the charge collection signal weight of the i-th charge collection electrode (9) in the detector pixel unit (6); the charge collection signal weight refers to the weight of the charge collection signal of the charge collection electrode (9) in the charge collection signals of the four charge collection electrodes (9).

9. The position sensing method according to claim 8, characterized in that: The charge collection signal weights can be obtained using any of the following formulas: Formula a: Formula b: In the formula, This represents the charge collection signal weight of the i-th charge collection electrode (9) in the detector pixel unit (6); This represents the charge collection signal of the i-th charge collection electrode (9) in the detector pixel unit (6).

10. The position sensing method according to claim 8, characterized in that: The charge signals of the four charge collection electrodes (9) in each detector pixel unit (6) are received by the four detector readout electrodes (8). If there is a set of arrival times with a maximum time difference less than the gate time in the time domain readout signals of the four detector readout electrodes (8), it is determined that the detector pixel unit (6) has been hit by an X-ray, and the detector pixel unit (6) is used as the hit detector pixel unit (6) for subsequent positioning calculation.

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