Automatic correction method for pixel parameters of pixel type X-ray detection chip
Through the automatic correction method of pixel parameters of the pixel-type X-ray detection chip, the detector performance problems caused by the difference in performance parameters between pixels are solved, and more efficient energy spectrum detection and better imaging quality are achieved.
Patent Information
- Application Number
- CN202411467566.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-21
- Publication Date
- 2025-02-11
AI Technical Summary
In pixel-type X-ray detection chips, due to the differences in performance parameters between pixels, the detector imaging quality, lower energy spectrum loss, and reduced energy resolution are caused by the current microelectronics design and process level, and the performance parameters between pixels are limited. The difference cannot be completely eliminated.
Provide a method for automatic correction of pixel parameters of pixel-type X-ray detection chips. By configuring the automatic scanning and correction of performance parameters between pixels, it realizes automatic scanning and correction of performance parameters differences between pixels by configuring the automatic scanning and testing function and interface. This method includes static baseline scanning and adjustment, dynamic response simulation testing and correction, and improves the overall performance indicators of the detection chip by automatically correcting pixel parameters.
Through the automatic correction method of pixel parameters, the energy spectrum detection lower limit loss and energy resolution broadening caused by baseline deviation between pixels and dynamic response differences are effectively reduced, and the imaging quality and overall performance indicators of the detector are improved.
Smart Images
Figure CN119421064A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of X-ray detection, and in particular to an automatic correction method for pixel parameters of a pixel-type X-ray detection chip. Background Art
[0002] Pixel-type X-ray detection chips are generally composed of several pixel-type sensors and corresponding pixel-type readout circuits. The pixel-type sensors convert incident X-ray photons into charge pulse signals, which are input into corresponding pixel-type readout circuits. The pixel-type readout circuits collect and amplify the charge pulse signals and output information such as the energy, position, and time of the incident X-ray photons.
[0003] Pixel-type X-ray detection chips are widely used in aerospace, medical, industrial and other fields, such as space X-ray pulsar detection navigation and timing, biological tissue color CT, material properties and damage detection, etc. The demand trends in various fields are: smaller pixel size, larger pixel array area, and lower energy spectrum detection limit. Smaller pixel size increases the difference in parameters such as leakage current and junction capacitance between pixels. At the same time, due to the smaller layout size of the readout circuit, the circuit structure is simpler and the parameter mismatch of circuit components is more obvious; larger pixel array area generally requires at least tens of thousands of pixels; lower energy spectrum detection limit requires lower parasitic capacitance between the sensor and the readout circuit, and also requires the layout size of the readout circuit input device to be reduced, and the parameter mismatch increases.
[0004] In summary, the demand for pixel-type X-ray detection chips has brought about the problem of performance parameter differences between pixels. The performance differences between pixels will lead to poor imaging quality, loss of the lower limit of the energy spectrum, reduced energy resolution and other problems that seriously reduce the overall performance indicators of the detector. Limited by the current level of microelectronics design and process, the performance parameter differences between pixels cannot be completely eliminated. Summary of the invention
[0005] In view of the problem that performance parameter differences exist between pixels of a pixel-type X-ray detection chip, the present invention provides a method for automatically correcting pixel parameters of a pixel-type X-ray detection chip, which realizes automatic scanning and correction of performance parameter differences between pixels and improves the overall performance index and application value of the detection chip.
[0006] To achieve the above object, the present invention provides a method for automatically correcting pixel parameters of a pixel-type X-ray detection chip, wherein the detection chip includes a plurality of pixels, each pixel includes a pixel-type sensor and a pixel-type readout circuit, and the method includes:
[0007] (1) Configure the function and interface for automatic scanning test of pixel performance parameters on the detection chip
[0008] After X-ray photons hit the pixel-type sensor, they can output the hitting time pulse, hitting pixel address, and hitting energy data;
[0009] Single pixels can be configured to be disabled or enabled through software;
[0010] The output signal of the front-stage amplifier in the pixel-type readout circuit enters the rear-stage comparator, and the global threshold of the rear-stage comparator is adjustable;
[0011] The output signal of the pre-amplifier enters the post-comparator, and the threshold crossing mark signal can be output immediately after the signal amplitude exceeds the threshold;
[0012] A comparator threshold fine-tuning DAC is set in the pixel-type readout circuit, which can fine-tune the single-pixel threshold based on the global threshold;
[0013] The preamplifier in the pixel type readout circuit is provided with an equivalent charge input test module and an equivalent charge input port, which converts the voltage step signal from the outside of the detection chip into an equivalent charge pulse signal and inputs it into the preamplifier;
[0014] (2) Static baseline scanning and adjustment
[0015] Static baseline scanning: When there is no X-ray input, the detection chip sets all pixels to the disabled state, and then sets the pixels to the working state one by one, adjusts the global threshold from bottom to top and from top to bottom, records the threshold when the over-threshold mark signal appears, and obtains the upper and lower limits of the preamplifier output baseline of all pixels. The average of the upper and lower limits of each pixel is the baseline value of the pixel. The upper limit value of each pixel minus the lower limit value is the peak-to-peak value of the noise output by each pixel amplifier. The peak-to-peak value of the noise can be marked as a bad pixel;
[0016] Threshold fine-tuning within a pixel: Statistical analysis is performed on the baseline values of all pixels to obtain the static baseline statistical distribution. The center value of the static baseline statistical distribution is used as a reference to automatically configure the comparator threshold fine-tuning DAC inside each pixel. The configuration value is the difference between the static baseline value of each pixel and the center value of the statistical distribution. Because the fine-tuning DAC may also have a step error, after the configuration is completed, the static baseline scan needs to be performed again to obtain a more concentrated static baseline value distribution after threshold fine-tuning. This process can be repeated to obtain the best adjustment effect;
[0017] (3) Dynamic response simulation test and correction
[0018] Dynamic response simulation test: After the static baseline values of all pixels are concentrated, a global threshold is set near the static baseline value, and no noise over-threshold triggering occurs. All pixels are set to the working state, and a voltage step signal is applied to the equivalent charge input port. After the test capacitor is connected in series inside the equivalent charge input test module, a charge quantity signal is formed. The charge quantity signal is input to the preamplifier of the pixel readout circuit, and the voltage amplitude output by each pixel under this input charge quantity state is recorded. Different input voltage step amplitudes are set and the output voltage amplitude is recorded. The input-output relationship of all pixels is fitted to obtain the analog input-output linearity response function library of all pixels, and the dynamic response output saturation value array of all pixels is recorded at the same time;
[0019] X-ray source calibration test correction: The analog input-output linear response function of all pixels is corrected through a real X-ray source calibration test. Three to four energy points are selected within the detection range, and at least two X-ray monochromatic sources are used to irradiate the detection chip. The monochromatic source energy and the output voltage amplitude of all pixels are recorded, and the analog input-output linear response function is corrected to obtain the final pixel parameter correction function library.
[0020] (4) Automatic correction of pixel parameters
[0021] The data of static baseline scanning and adjustment, dynamic response testing and correction are integrated to obtain a complete parameter correction array for all pixels of a single detection chip, including: baseline value, baseline correction value, pixel parameter correction function, dynamic response output saturation value, and bad pixel flag. The complete parameter correction array is bound to the corresponding detection chip. After the detection chip is powered on, it can automatically perform baseline correction and bad pixel shielding. The raw data obtained by the detection chip is automatically output after passing through the pixel parameter correction function.
[0022] After adopting the above technical solution, the present invention has at least the following beneficial effects:
[0023] (1) The static baseline deviation characteristics and dynamic response characteristics of all pixels in the detection chip can be efficiently obtained.
[0024] (2) Effectively reduce the loss of the lower limit of energy spectrum detection caused by baseline deviation between pixels.
[0025] (3) Effectively reduce the energy resolution broadening caused by the dynamic response difference between pixels.
[0026] (4) Effectively reduce imaging non-uniformity caused by baseline deviation and dynamic response differences between pixels. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.
[0028] Figure 1 Modify the functional block diagram for automatic scanning of chip functions and parameters;
[0029] Figure 2 This is an example diagram of the static baseline statistical distribution before correction;
[0030] Figure 3 This is an example diagram of the statistical distribution of the corrected static baseline. DETAILED DESCRIPTION
[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0032] The present disclosure provides a method for automatically correcting pixel parameters of a pixel-type X-ray detection chip. The detection chip includes a plurality of pixels, each of which includes a pixel-type sensor and a pixel-type readout circuit. The method includes:
[0033] (1) Configure the function and interface for automatic scanning test of pixel performance parameters on the detection chip
[0034] After X-ray photons hit the pixel-type sensor, they can output the hitting time pulse, hitting pixel address, and hitting energy data;
[0035] Single pixels can be configured to be disabled or enabled through software;
[0036] The output signal of the front-stage amplifier in the pixel-type readout circuit enters the rear-stage comparator, and the global threshold of the rear-stage comparator is adjustable;
[0037] The output signal of the pre-amplifier enters the post-comparator, and the threshold crossing mark signal can be output immediately after the signal amplitude exceeds the threshold;
[0038] A comparator threshold fine-tuning DAC is set in the pixel-type readout circuit, which can fine-tune the single-pixel threshold based on the global threshold;
[0039] The preamplifier in the pixel type readout circuit is provided with an equivalent charge input test module and an equivalent charge input port, which converts the voltage step signal from the outside of the detection chip into an equivalent charge pulse signal and inputs it into the preamplifier;
[0040] (2) Static baseline scanning and adjustment
[0041] The basic principle of static baseline scanning of pixels: when the global threshold of the pixel comparator is set within the peak-to-peak value range of the pixel amplifier output signal, a noise trigger will be generated and an over-threshold flag signal will appear; when the threshold is out of the peak-to-peak value range of the CSA amplifier output signal, no noise trigger will be generated.
[0042] Static baseline scanning: When there is no X-ray input, the detection chip sets all pixels to the disabled state, then sets the pixels to the working state one by one, adjusts the global threshold from bottom to top and from top to bottom, and records the threshold when the over-threshold mark signal appears.
[0043] The specific static baseline scanning method is as follows:
[0044] 1. All pixels are configured to be disabled and the global threshold is configured to be the minimum value;
[0045] 2. Configure 1 row and 1 column of pixels to work;
[0046] 3. The global threshold value increases gradually from the minimum value, and stops when the monitoring is triggered by noise;
[0047] 4. Record the threshold when noise trigger occurs, which is the lower limit of the pixel amplifier output baseline;
[0048] 5. The global threshold is configured as the maximum value;
[0049] 6. The global threshold is gradually reduced from the maximum value, and the monitoring stops when noise triggers;
[0050] 7. Record the threshold when the noise is triggered, which is the upper limit of the pixel amplifier output baseline;
[0051] 8. All pixels are configured to be disabled and the global threshold is configured to be the minimum value;
[0052] 9. Configure 1 row and 2 columns of pixels to work, and repeat steps 3-8 above;
[0053] 10. Configure 1 row and 3 columns of pixels to work, and repeat steps 3-8 above;
[0054] …
[0055] XX. Configure the pixels in rows M and columns N to work, and repeat steps 3-8 above;
[0056] Through the above automated scanning process, the upper and lower limits of the baseline output of the preamplifier of all pixels are obtained. The average value of the upper and lower limits of each pixel is the baseline value of the pixel. The peak-to-peak value of the noise output by each pixel amplifier is obtained by subtracting the upper limit value of each pixel from the lower limit value. The peak-to-peak value of the noise can be marked as a bad pixel.
[0057] Fine-tuning of the intra-pixel threshold: Statistical analysis of the baseline values of all pixels can be performed to obtain the static baseline statistical distribution. Generally, the static baseline statistical distribution is caused by the random mismatch of parameters between different pixel circuits of the detection chip, so its statistical characteristics generally present a Gaussian distribution, such as Figure 2 shown.
[0058] According to the static baseline statistical distribution, the difference between each pixel and the distribution center value is calculated to form a baseline difference array of 1 row and 1 column (E11), 1 row and 2 columns (E12), 1 row and 3 columns (E13) ... M rows and N columns (Emn). The baseline difference array is used as a configuration file to automatically configure the comparator threshold fine-tuning DAC inside each pixel to eliminate the difference between the baseline of each pixel and the statistical center value. After the configuration is completed, the static baseline scan is performed again to obtain a more concentrated static baseline value distribution after threshold fine-tuning, such as Figure 3 As shown, this process can be repeated to obtain the best adjustment effect.
[0059] (3) Dynamic response simulation test and correction
[0060] Dynamic response simulation test: After the static baseline values of all pixels are concentrated, a global threshold is set near the static baseline value, and no noise trigger occurs. All pixels are set to the working state, and a voltage step signal is applied to the equivalent charge input port. After the test capacitor is connected in series inside the equivalent charge input test module, a charge quantity signal is formed. The charge quantity signal is input to the preamplifier of the pixel type readout circuit, and the voltage amplitude output by each pixel under this input charge quantity state is recorded. Different input voltage step amplitudes are set and the output voltage amplitude is recorded. The input-output relationship of all pixels is fitted to obtain the analog input-output linearity response function library of all pixels, and the dynamic response output saturation value array of all pixels is recorded at the same time;
[0061] Radiation source calibration test correction: The analog input-output linear response function of all pixels is obtained through dynamic response simulation test. Due to factors such as the conversion efficiency of pixel-type sensors to X-ray photons, the charge collection efficiency of pixel-type readout circuit amplifiers, the gain error of amplifiers, and test capacitor errors, this response function is different from the input-output response of actual X-ray photon incidence. It is also necessary to correct the analog input-output linear response function of all pixels through real radiation source calibration test. Three to four energy points are selected within the detection range, and at least two X-ray monochromatic sources are used to irradiate the detection chip. The monochromatic source energy and the output voltage amplitude of all pixels are recorded, and the analog input-output linear response function is corrected to obtain the final pixel parameter correction function library.
[0062] The specific dynamic response simulation test and correction process are as follows:
[0063] 1. Correct the static baseline to a unified state;
[0064] 2. Set the global threshold based on the unified baseline to avoid noise triggering;
[0065] 3. Configure all pixels to work;
[0066] 4. Set the signal source to a step voltage signal, and the voltage difference value on the rising edge is △V1. Then the charge Q input to each pixel is △V1*Ctest;
[0067] 5. Single output of step signal;
[0068] 6. The preamplifier of each pixel of the detection chip converts the input charge signal into a voltage pulse output, which then enters the peak holder in the pixel. The peak holder and address of each pixel are output outward in sequence with the trigger signal;
[0069] 7. Using the trigger signal as a sign, the energy level values output by all pixels are collected in sequence;
[0070] 8. After the acquisition is completed, the voltage difference value of the rising edge of the step signal is automatically adjusted to △V2, △V3...△Vn, and all energy level values are acquired until the energy level values output by all pixels are saturated;
[0071] 9. Fit the input-output relationship of all pixels to obtain the input-output response function library of the equivalent test, and record the dynamic response output saturation value array of all pixels;
[0072] 10. Use at least two X-ray monochromatic sources to irradiate the detection chip for a long time, record the monochromatic source energy and the output voltage amplitude of all pixels, correct the analog input and output linearity response function, and obtain the final pixel parameter correction function library;
[0073] 11. Use the monochrome source energy and the output voltage amplitude of all pixels to correct the analog input and output linearity response function to obtain the final pixel parameter correction function library:
[0074] (4) Automatic correction of pixel parameters
[0075] The data of static baseline scanning and adjustment, dynamic response testing and correction are integrated to obtain a complete parameter correction array for all pixels of a single detection chip, including: baseline value, baseline correction value, pixel parameter correction function, dynamic response output saturation value, and bad pixel flag. The complete parameter correction array is bound to the corresponding detection chip. After the detection chip is powered on, it can automatically perform baseline correction and bad pixel shielding. The raw data obtained by the detection chip is automatically output after passing through the pixel parameter correction function.
[0076] Although the present invention has been disclosed as above by way of embodiments, it is not intended to limit the present invention. Any person skilled in the art may make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the claims.
Claims
1. A method for automatically correcting pixel parameters of a pixel-type X-ray detection chip, wherein the detection chip comprises a plurality of pixels, each pixel comprising a pixel-type sensor and a pixel-type readout circuit, characterized in that: The method comprises: (1) Configure the function and interface for automatic scanning test of pixel performance parameters on the detection chip After X-ray photons hit the pixel-type sensor, they can output the hitting time pulse, hitting pixel address, and hitting energy data; Single pixels can be configured to be disabled or enabled through software; The output signal of the front-stage amplifier in the pixel-type readout circuit enters the rear-stage comparator, and the global threshold of the rear-stage comparator is adjustable; The output signal of the pre-amplifier enters the post-comparator, and the threshold crossing mark signal can be output immediately after the signal amplitude exceeds the threshold; A comparator threshold fine-tuning DAC is set in the pixel-type readout circuit, which can fine-tune the single-pixel threshold based on the global threshold; The preamplifier in the pixel type readout circuit is provided with an equivalent charge input test module and an equivalent charge input port, which converts the voltage step signal from the outside of the detection chip into an equivalent charge pulse signal and inputs it into the preamplifier; (2) Static baseline scanning and adjustment Static baseline scanning: When there is no X-ray input, the detection chip sets all pixels to the disabled state, and then sets the pixels to the working state one by one, adjusts the global threshold from bottom to top and from top to bottom, records the threshold when the over-threshold mark signal appears, and obtains the upper and lower limits of the preamplifier output baseline of all pixels. The average of the upper and lower limits of each pixel is the baseline value of the pixel. The upper limit value of each pixel minus the lower limit value is the peak-to-peak value of the noise output by each pixel amplifier. The peak-to-peak value of the noise can be marked as a bad pixel; Threshold fine-tuning within a pixel: Statistical analysis is performed on the baseline values of all pixels to obtain the static baseline statistical distribution. The center value of the static baseline statistical distribution is used as a reference to automatically configure the comparator threshold fine-tuning DAC inside each pixel. The configuration value is the difference between the static baseline value of each pixel and the center value of the statistical distribution. Because the fine-tuning DAC may also have a step error, after the configuration is completed, the static baseline scan needs to be performed again to obtain a more concentrated static baseline value distribution after threshold fine-tuning. This process can be repeated to obtain the best adjustment effect; (3) Dynamic response simulation test and correction Dynamic response simulation test: After the static baseline values of all pixels are concentrated, a global threshold is set near the static baseline value, and no noise over-threshold triggering occurs. All pixels are set to the working state, and a voltage step signal is applied to the equivalent charge input port. After the test capacitor is connected in series inside the equivalent charge input test module, a charge quantity signal is formed. The charge quantity signal is input to the preamplifier of the pixel readout circuit, and the voltage amplitude output by each pixel under this input charge quantity state is recorded. Different input voltage step amplitudes are set and the output voltage amplitude is recorded. The input-output relationship of all pixels is fitted to obtain the analog input-output linearity response function library of all pixels, and the dynamic response output saturation value array of all pixels is recorded at the same time; Radiation source calibration test correction: The analog input-output linear response function of all pixels is corrected through real radiation source calibration test. Three to four energy points are selected within the detection range, and at least two X-ray monochromatic sources are used to irradiate the detection chip. The monochromatic source energy and the output voltage amplitude of all pixels are recorded, and the analog input-output linear response function is corrected to obtain the final pixel parameter correction function library. (4) Automatic correction of pixel parameters The data of static baseline scanning and adjustment, dynamic response testing and correction are integrated to obtain a complete parameter correction array for all pixels of a single detection chip, including: baseline value, baseline correction value, pixel parameter correction function, dynamic response output saturation value, and bad pixel flag. The complete parameter correction array is bound to the corresponding detection chip. After the detection chip is powered on, it can automatically perform baseline correction and bad pixel shielding. The raw data obtained by the detection chip is automatically output after passing through the pixel parameter correction function.