Self-adaptive quantization compression type large dynamic photon counting reading circuit
Through the adaptive quantized compression large dynamic photon counting reading circuit, the area response statistics and adjustment threshold configuration module are used to adjust the quantized compressed value, which solves the dynamic range expansion and quantization accuracy loss of photon counting devices under the background of limited area bandwidth and strong background. The problem is that high-precision and efficient photon detection performance are achieved.
Patent Information
- Application Number
- CN202411459435.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-18
- Publication Date
- 2025-01-10
AI Technical Summary
The existing photon counting focal planes are difficult to expand their dynamic range under the limitations of area, power consumption and readout rate. They have weak signal quantization accuracy losses under strong backgrounds, and traditional nonlinear circuits respond to transitions and have high data processing complexity.
Adaptive quantization compression large dynamic photon counting reading circuit, including region response statistics module, adjustment threshold configuration module and multiple pixel circuits with the same structure, quantization adjustment is achieved through quantization regulator, voltage comparator, flip-flop and photon counter , the adjustment threshold configuration module adjusts the quantized compressed value according to the regional response statistical results to improve the dynamic range and quantization accuracy.
It realizes large dynamic range and high-precision event quantization, improves photon detection performance, and solves the problem of quantization accuracy loss under limited area bandwidth and strong backgrounds in complex backgrounds.
Smart Images
Figure CN119290153A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of photoelectric detection, relates to a photon counting focal plane, and in particular to an adaptive quantization compression type large dynamic photon counting readout circuit. Background Art
[0002] The photon counting Geiger avalanche focal plane is a new type of digital image sensor based on Geiger mode avalanche photodiodes and imaging with single photon detection or single photon counting mechanism. The photon counting Geiger avalanche focal plane is composed of a hybrid integration of a Geiger mode avalanche photodiode array and a dedicated photon counting readout circuit based on CMOS integrated circuits. Its working principle is to convert the number of photon events responded by the photosensitive element into a digital signal to form a binary field image, and form a multi-bit intensity frame image with grayscale information within a single frame integration time. Its dynamic range depends on the range of the photon event counter. The photon counting Geiger avalanche focal plane has the characteristics of large dynamic range, high-precision event quantization, high frame rate, low readout noise, compact area, etc., which are difficult to achieve with traditional passive focal plane readout circuits. It has a wide range of application needs in the defense military and civilian market fields such as ground-based space surveillance, defense reconnaissance night vision, and medical imaging.
[0003] In practical applications, the area, power consumption and readout rate limit the increase in the number of counting bits of the circuit. The industry often uses logarithmic circuits, background photon counting, special encoding, on-chip noise algorithms, etc. to expand the dynamic range of the circuit. However, factors such as the nonlinearity of the counting circuit itself, the increase in design and data processing complexity limit the further improvement of key performance indicators such as the dynamic range and readout rate of photon counting devices. The limiting factors are mainly in the following aspects:
[0004] 1) Event quantization transition zone fuzziness: In order to achieve dynamic expansion under limited area, the logarithmic compression circuit and digital compression coding circuit used have problems such as fuzzy compression boundary and introducing more area power consumption, which increases the complexity of subsequent data processing algorithms and even reduces the system response speed in complex cases.
[0005] 2) Loss of quantization accuracy under strong background: The response curve of the traditional dynamic expansion method usually shows a decreasing slope when the background interference increases, which seriously affects the quantization accuracy of weak signal photon events under strong background.
[0006] 3) Increased data volume: In order to further increase the device event counting range, special encoding, overflow bits and other improvements are introduced, which requires more transmission cycles and limits the device readout frame rate. Summary of the invention
[0007] In view of this, the purpose of the present invention is to provide an adaptive quantization compression type large dynamic photon counting readout circuit to solve the problems of dynamic range expansion under limited area bandwidth, loss of quantization accuracy of weak signal events under strong background, and transition ambiguity of traditional nonlinear circuit response, and difficulty in data processing.
[0008] In order to achieve the above object, the present invention provides the following technical solutions:
[0009] An adaptive quantization compression type high dynamic photon counting readout circuit comprises a regional response statistics module, an adjustment threshold configuration module and a plurality of pixel circuits with the same structure, and also comprises a statistics region regulator.
[0010] The structure of the pixel circuit includes: a quantization regulator, a voltage comparator, a trigger and a photon counter. The quantization regulator receives a photon event signal from a photosensitive element and is used to realize the quantization regulation of the photon event count. Each pixel circuit is configured with a photosensitive element connected to the quantization regulator; the positive input end of the voltage comparator receives the output voltage of the quantization regulator, and the reverse input end is connected to the reference voltage; the clock input end of the trigger is connected to the output end of the voltage comparator, and the input end of the trigger is connected to a high-level signal; the photon counter receives a carry signal from the trigger and completes the summation of the number of photon responses.
[0011] The regional response statistics module is connected to the output end of the photon counter of each pixel circuit in the statistics area, and counts the saturation of the photon event count of each pixel circuit in the statistics area.
[0012] The adjustment threshold configuration module is connected to the regional response statistics module, and adjusts the quantization compression value of the quantization regulator of each pixel circuit in the region according to the statistical result of the regional response statistics module.
[0013] The statistical region regulator is connected to the regional response statistical module and the adjustment threshold configuration module respectively, and is used to adjust the statistical region of the regional response statistical module and adjust the pixel circuits required to be connected to the adjustment threshold configuration module. The statistical region may include any number of pixel circuits, and the quantitative compression adjustment of each pixel circuit in the region is achieved through the cooperation of the regional response statistical module and the adjustment threshold configuration module.
[0014] Furthermore, the quantized regulator includes a capacitor and the same number of current sources and register switches. The current sources and register switches correspond to each other to form a plurality of series branches, each of which is connected in parallel to the first end of the capacitor; the first end of the capacitor is connected to the positive input end of the voltage comparator, and the second end is grounded. Each register switch is connected to a photosensitive element to receive the photon event signal of the photosensitive element.
[0015] Furthermore, the adjustment threshold configuration module adjusts the quantization compression value of the quantization adjuster according to the proportion of pixel circuits generating overflow in the region to the total number of pixel circuits in the region, wherein, when the proportion of pixel circuits generating overflow in the region exceeds the threshold, the quantization compression value is increased by 1 and the quantization compression value of each pixel circuit in the region is adjusted, and then the proportion of pixel circuits generating overflow in the region to the total number of pixel circuits in the region is counted through the regional response statistics module; the above process is repeated until the proportion of pixel circuits generating overflow to the total number of pixel circuits in the region is less than the threshold.
[0016] The beneficial effects of the present invention are as follows: the present invention solves the problems of dynamic range expansion under limited area bandwidth, loss of quantization accuracy of weak signal events under strong background, fuzzy response transition of traditional nonlinear circuits, and difficulty in data processing, and realizes a photon counting readout circuit with large dynamic range, high-precision event quantization, and compact area, which can improve the photon detection performance of the device under complex background environments.
[0017] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:
[0019] Figure 1 is a structural block diagram of the photon counting readout circuit of the present invention;
[0020] Figure 2 is a schematic diagram of a pixel circuit structure;
[0021] Figure 3 This is a schematic diagram of the regional response statistics module structure;
[0022] Figure 4 It is the timing diagram of photosensitive element control timing;
[0023] Figure 5 To quantify the photon counter input when the compression is 8;
[0024] Figure 6 Examples of segmented quantization for different numbers of photon events. DETAILED DESCRIPTION
[0025] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and the features in the embodiments can be combined with each other without conflict.
[0026] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.
[0027] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.
[0028] like Figure 1 As shown, an adaptive quantization compression type large dynamic photon counting readout circuit proposed in an embodiment of the present invention mainly includes a photon counting readout circuit array, a regional response statistics module and an adjustment threshold configuration module.
[0029] The pixel circuit array includes N+1 pixel circuits, each of which includes a quenching / recovery module, a quantization regulator, a voltage comparator, a trigger and a photon counter. Figure 2 As shown. The quenching / recovery module is used to switch the response state of the photosensitive element, the quantization regulator is used to expand the dynamic range of the pixel circuit count, and the photon counter is used to complete the summation of the number of photon responses of the corresponding pixels within the detection gate width. Among them, the quantization regulator includes a register-type switch array and a number of current sources. Specifically, the switch array includes N+1 switches SW0~SW N, the number of current sources is also N+1, the switches and current sources are paired to form N+1 series branches, these N+1 series branches are connected in parallel to the first end of a capacitor, and the first end of the capacitor is also connected to the positive input end of the voltage comparator. The negative input end of the voltage comparator is connected to a reference voltage V ref The output end of the voltage comparator is connected to the clock input end of the trigger, and the output end of the trigger is connected to the input end of the photon counter.
[0030] The working principle of the pixel circuit is as follows:
[0031] When the register type switch array is used, the switch SW i When the corresponding bit is logically "true", the switch SW i The corresponding current source I i Connect to the positive input of the comparator. When the photosensitive element responds to a photon event, the current source I i Charge the positive input of the comparator. When multiple current sources are connected, the positive input voltage is higher than the reference voltage V ref , the comparator output level will flip from "0" to "1", causing the trigger to generate a rising edge output, and the accumulated result of the photon counter increases by 1. i The logic signal is generated by the light-sensitive element connected to it. When the light-sensitive element receives a photon, it switches the light switch to i The output logic is a logic signal of "true". Therefore, the quantization compression of photon counts can be achieved by increasing or decreasing the number of photon events required for the quantizer to generate a voltage output, that is, increasing or decreasing the number of switches that need to be turned on in the quantizer.
[0032] The regional response statistics module is connected to the overflow bit of the photon counter of the pixel circuit through the bus. The regional response statistics module is connected to the overflow bit of the photon counter of M+1 pixel circuits in the region according to the region range set by the statistical region regulator, and is used to count the saturation of the photon count of each pixel circuit in the region. Its working principle is as follows Figure 3 As shown, the signals of the input terminals P0, P1, P2, etc. come from the overflow bits of the photon counters of the pixel circuits in the region. The number of overflow bits can be counted through the numerical logic circuit, and the result is output to the threshold adjustment configuration module. Specifically, in this embodiment, the number of overflow bits is counted by the numerical logic circuit composed of half adders. For example, the region counted by the regional response statistics module includes four pixel circuits P0 to P3. When the value in the half adder HA3b is 4, it means that the four pixel circuits in the region have all output overflow bits. At this time, the regional response statistics module outputs a signal to the threshold adjustment configuration module.
[0033] After receiving the statistical results of the regional response statistics module, the adjustment threshold configuration module adjusts the quantization adjustment value of the next detection according to the proportion of overflowed pixels in the entire area. If the overflowed pixels account for more than 80% of the entire area, the quantization compression value increases by 1 until the overflowed pixels account for less than 25% of the entire area. The quantization adjustment amount is generated through a numerical logic circuit, and then the configuration result is updated back to the quantization regulator in each pixel circuit in the area via the bus, so that each pixel circuit in the area performs quantization compression adjustment synchronously. Specifically, through quantization compression adjustment, the number of photon events required for the quantization regulator of each pixel circuit to generate a voltage output is increased (that is, more light is required), thereby making it more difficult for the photon counter to generate an overflow signal output, thereby realizing dynamic expansion adjustment.
[0034] In another embodiment of the present invention, the quantization compression value range of the adaptive quantization compression type large dynamic photon counting readout circuit is set to 1 to 10, which supports segmented configurable / adaptive quantization compression adjustment. In this embodiment, the photosensitive element control timing is set as follows Figure 4 shown.
[0035] When the quantization compression value is set to 8, the photon counter INPUT node input is as follows Figure 5 , it can be seen that the photon counter increases the photon count value by 1 if and only if 8 consecutive photon events occur.
[0036] The count values of the photon counter under different photon event numbers and quantization compression value settings are as follows Figure 6 As shown, where A1-A4 are integers and A1>A2>A3>A4, from Figure 6 It can be seen that as the quantization compression value decreases, the number of photon events required to generate a photon count value each time gradually decreases.
[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.
Claims
1. An adaptive quantization compression type high dynamic photon counting readout circuit, characterized in that: It includes a regional response statistics module, an adjustment threshold configuration module and a plurality of pixel circuits with the same structure; Each of the pixel circuits includes a quantization regulator and a photon counter connected to the quantization regulator; the quantization regulator receives a photon event signal from a photosensitive element and is used to implement quantization regulation of photon event counts, and each of the pixel circuits is configured with one photosensitive element; the photon counter receives a carry signal from the quantization regulator and completes the summation of the number of photon responses; The regional response statistics module is connected to the output end of the photon counter of each pixel circuit in the statistical area, and counts the saturation of the photon event count of each pixel circuit in the statistical area; The adjustment threshold configuration module is connected to the regional response statistics module, and adjusts the quantization compression value of the quantization regulator of each pixel circuit in the region according to the statistical result of the regional response statistics module.
2. The adaptive quantization compression type high dynamic photon counting readout circuit according to claim 1, characterized in that: The pixel circuit also includes a voltage comparator and a trigger; the positive input end of the voltage comparator receives the output voltage of the quantization regulator, the reverse input end is connected to the reference voltage, and the output end is connected to the clock input end of the trigger; the input end of the trigger is connected to a high-level signal, and the output end is connected to the input end of the photon counter.
3. The adaptive quantization compression type high dynamic photon counting readout circuit according to claim 1 or 2, characterized in that: The quantized regulator comprises a capacitor and the same number of current sources and register-type switches; the current sources and the register-type switches form a plurality of series branches corresponding to each other, and each series branch is connected in parallel to the first end of the capacitor; the first end of the capacitor is connected to the positive input end of the voltage comparator, and the second end is grounded; Each of the register-type switches is connected to a photosensitive element to receive a photon event signal from the photosensitive element.
4. The adaptive quantization compression type high dynamic photon counting readout circuit according to claim 1, characterized in that: The adjustment threshold configuration module adjusts the quantization compression value of the quantization regulator according to the ratio of the pixel circuits generating overflow in the region to the total number of pixel circuits in the region, wherein when the ratio of the pixel circuits generating overflow in the region exceeds the threshold, the quantization compression value is increased by 1 and the quantization compression value of each pixel circuit in the region is adjusted, and then the ratio of the pixel circuits generating overflow in the region to the total number of pixel circuits in the region is counted by the regional response statistics module; The above process is repeated until the proportion of pixel circuits generating overflow to the total number of pixel circuits in the region is less than a threshold.