Method and circuit for reducing power consumption of imaging device

Abstract

The embodiment of the invention provides a method and circuit for reducing power consumption of an imaging device. The imaging device at least comprises a pixel array composed of a plurality of SPAD pixels. The method comprises the steps that light intensity information and / or counting information are / is acquired, the light intensity information comprises light intensity parameters or first-class photon counting values of SPAD pixels in a pixel array, and the counting information comprises second-class photon counting values of the SPAD pixels in the pixel array; wherein the first type of photon count value is related to ambient light intensity, and the second type of photon count value is related to an imaging target; and judging an imaging condition according to the light intensity information or the counting information, and adjusting the photon counting rate of SPAD pixels in the pixel array according to a judgment result.

Description

Technical Field

[0001] The present disclosure relates to the field of photon counting imaging technology, and in particular to a method and circuit for reducing power consumption of an imaging device. Background Art

[0002] With the development of single photon avalanche diode (SPAD) device manufacturing technology and integrated circuits, single photon counting imaging (PCI) technology based on SPAD has been applied. In a SPAD-based PCI image sensor (SPAD PCI sensor), each pixel unit has an independent SPAD, quenching circuit, and counting circuit, which replicates and expands the pixel unit into a photosensitive area array with M rows and N columns (M and N are both integers greater than 0). At the same time, components such as readout circuits and control circuits are connected outside the photosensitive area array to form a PCI image sensor that can capture the target optical image.

[0003] Image resolution is one of the important performance indicators of image sensors. Improving image resolution requires integrating more pixel units in the photosensitive area of ​​the sensor to form a larger pixel array. However, the expansion of the pixel array will not only lead to a larger area of ​​the sensor chip, but also increase the power consumption of the chip. Especially in the case of strong ambient light, the number of SPAD avalanche events per unit time increases, the pixel operating frequency increases, and the current consumption increases. Furthermore, excessive power consumption of the chip will not only cause severe chip heating, but may also cause circuit function failure. Summary of the invention

[0004] Embodiments of the present disclosure provide a method and a circuit for reducing power consumption of an imaging device.

[0005] In a first aspect, an embodiment of the present disclosure provides a method for reducing power consumption of an imaging device, wherein the imaging device at least includes a pixel array composed of a plurality of SPAD pixels; the method includes:

[0006] Acquire light intensity information and / or counting information, wherein the light intensity information includes a light intensity parameter or a first type of photon counting value of the SPAD pixel in the pixel array, and the counting information includes a second type of photon counting value of the SPAD pixel in the pixel array; wherein the first type of photon counting value is related to the ambient light intensity, and the second type of photon counting value is related to the imaging target;

[0007] An imaging condition is determined according to the light intensity information or the counting information, and a photon counting rate of the SPAD pixel in the pixel array is adjusted according to the determination result.

[0008] In some embodiments, the counting information is used for determining the imaging condition and for imaging the imaging target; the light intensity information and the counting information are acquired in the same frame or in different frames.

[0009] In some embodiments, when the light intensity information and the counting information are acquired in different frames, the SPAD pixel used to acquire the first type of photon counting value is the same as the SPAD pixel used to acquire the second type of photon counting value, and the light intensity information is acquired in the previous frame and the counting information is acquired in the next frame.

[0010] In some embodiments, when the light intensity information and the counting information are acquired in the same frame, the SPAD pixels used to acquire the first type of photon counting values ​​and the second type of photon counting values ​​are different, and the light intensity information and the counting information are acquired simultaneously.

[0011] In some embodiments, judging the imaging condition according to the light intensity information, and adjusting the photon counting rate of the SPAD pixel in the pixel array according to the judgment result, includes:

[0012] The light intensity parameter is compared with at least one light intensity threshold. If the light intensity parameter is greater than or equal to the light intensity threshold, the photon counting rate of the SPAD pixel in the pixel array is lowered; if the light intensity parameter is less than the light intensity threshold, the photon counting rate of the SPAD pixel in the pixel array is increased.

[0013] In some embodiments, judging the imaging condition according to the light intensity information, and adjusting the photon counting rate of the SPAD pixel in the pixel array according to the judgment result, includes:

[0014] The first type of photon count value is compared with at least one judgment threshold. If the first type of photon count value is greater than or equal to the judgment threshold, the photon count rate of the SPAD pixel in the pixel array is lowered; if the first type of photon count value is less than the judgment threshold, the photon count rate of the SPAD pixel in the pixel array is increased.

[0015] In some embodiments, increasing the photon count rate of the SPAD pixels in the pixel array includes:

[0016] reducing the dead time of the SPAD pixels in the pixel array;

[0017] The step of lowering the photon count rate of the SPAD pixels in the pixel array comprises:

[0018] The dead time of the SPAD pixels in the pixel array is increased.

[0019] In some embodiments, judging the imaging condition according to the counting information, and adjusting the photon counting rate of the SPAD pixel in the pixel array according to the judging result, comprises:

[0020] The second type of photon count value is compared with a count threshold, and if the second type of photon count value is equal to the count threshold, the photon count rate of the SPAD pixel in the pixel array is reduced to 0.

[0021] In some embodiments, the first type of photon count value comprises a sum, an average or a median of the photon count values ​​of the SPAD pixels in the pixel array.

[0022] In a second aspect, an embodiment of the present disclosure provides a circuit for reducing power consumption of an imaging device, wherein the imaging device at least includes a pixel array composed of a plurality of SPAD pixels; the circuit includes an acquisition circuit, a counting circuit and an adjustment circuit; wherein:

[0023] The acquisition circuit is used to acquire light intensity information, wherein the light intensity information includes a light intensity parameter or a first type of photon count value of the SPAD pixel in the pixel array, wherein the first type of photon count value is related to the ambient light intensity;

[0024] The counting circuit is used to obtain counting information, wherein the counting information includes a second type of photon counting value of the SPAD pixel in the pixel array, and the second type of photon counting value is related to an imaging target;

[0025] The adjustment circuit is used to determine the imaging condition according to the light intensity information or the counting information, and adjust the photon counting rate of the SPAD pixel in the pixel array according to the determination result.

[0026] In a third aspect, an embodiment of the present disclosure provides an imaging device, which applies the method as described in any one of the first aspects and includes a circuit as described in any one of the second aspects.

[0027] In this way, the present invention can judge the imaging conditions according to the light intensity parameters or the first type of photon counting values, and then adjust the photon counting rate of the SPAD pixel, or judge the imaging conditions by the second type of photon counting values, and then adjust the photon counting rate of the SPAD pixel, thereby adjusting the photon counting rate of the SPAD pixel under different imaging conditions, reducing the operating frequency of the SPAD pixel at high exposure intensity (such as strong ambient light), and thus reducing the power consumption of the imaging device; at low exposure intensity (such as darker environment), increasing the operating frequency of the SPAD pixel to capture more photons and improve the imaging effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1A grayscale image and its corresponding photon count value of a SPAD pixel provided in an embodiment of the present disclosure;

[0029] Figure 2 A flowchart of a method for reducing power consumption of an imaging device provided by an embodiment of the present disclosure;

[0030] Figure 3 A schematic diagram of the relationship between light intensity (light power) and photon count rate provided in an embodiment of the present disclosure;

[0031] Figure 4 A schematic diagram of the structure of a circuit for reducing power consumption of an imaging device provided by an embodiment of the present disclosure;

[0032] Figure 5 A schematic diagram of a specific structure of a circuit for reducing power consumption of an imaging device provided by an embodiment of the present disclosure Figure 1 ;

[0033] Figure 6 A schematic diagram of the structure of a data readout circuit of a pixel array provided in an embodiment of the present disclosure;

[0034] Figure 7 A schematic diagram of a specific structure of a circuit for reducing power consumption of an imaging device provided by an embodiment of the present disclosure Figure 2 ;

[0035] Figure 8 A schematic diagram of a specific structure of a circuit for reducing power consumption of an imaging device provided by an embodiment of the present disclosure Figure 3 ;

[0036] Fig. 9 A schematic diagram of a specific structure of a circuit for reducing power consumption of an imaging device provided by an embodiment of the present disclosure Figure 4 ;

[0037] Fig.10 A schematic diagram of the structure of an imaging device provided in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. It is understood that the specific embodiments described herein are only used to explain the relevant applications, rather than to limit the present disclosure. It should also be noted that, for the convenience of description, only the parts related to the relevant applications are shown in the drawings.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present disclosure belongs. The terms used herein are only for the purpose of describing the embodiments of the present disclosure and are not intended to limit the present disclosure.

[0040] In the following description, reference is made to “some embodiments”, which describe a subset of all possible embodiments, but it will be understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0041] It should be pointed out that the terms "first\second\third" involved in the embodiments of the present disclosure are merely used to distinguish similar objects and do not represent a specific ordering of the objects. It can be understood that "first\second\third" can be interchanged in a specific order or sequence where permitted, so that the embodiments of the present disclosure described here can be implemented in an order other than that illustrated or described here.

[0042] In a SPAD-based PCI image sensor, its pixels can contain one or more pixel units, each of which contains an independent SPAD, so the pixels of a PCI image sensor are also called SPAD pixels. When a SPAD pixel is in operation, when one or more photons are incident on the SPAD, an avalanche event can be triggered; the avalanche event will cause the quenching circuit to work and output a pulse signal; the downstream counting circuit counts the number of pulse signals. The photon count value of a single SPAD pixel reflects the light intensity of a single-point target, while the photon count value counted by a two-dimensional pixel array can depict a digital image of the target field of view area.

[0043] See also Figure 1 , which shows a grayscale image provided by an embodiment of the present disclosure and the corresponding photon count value of a SPAD pixel. Figure 1 As shown, the grayscale image is composed of the grayscale corresponding to each SPAD pixel, and the grayscale of each SPAD pixel is represented by the number of photons received by the SPAD pixel or the ratio of the number of photons. Figure 1 In the example, the number of photons received by the SPAD pixel (i.e., the photon count value) is used to represent the brightness of the image output by the PCI image sensor. The more photons the SPAD pixel receives, the higher the photon count value, and the higher the brightness of the image output by the PCI image sensor.

[0044] It should be noted that image resolution is one of the important performance indicators of image sensors, reflecting the ability of image sensors to capture the details of optical targets. Improving image resolution requires integrating more pixel units in the photosensitive area of ​​the image sensor, expanding the pixel array, and forming a larger pixel array. In the case of a unified field of view, a larger pixel array can capture more target details.

[0045] However, the expansion of the pixel array not only leads to a larger area of ​​the sensor chip, but also causes the current consumed by the chip to increase proportionally, and the power consumption of the chip increases. Especially in the case of strong ambient light, the number of SPAD avalanche events per unit time increases, the pixel operating frequency increases, and the current consumption increases. Furthermore, excessive chip power consumption will not only cause severe chip heating and chip temperature deviation from the appropriate range, but more seriously, it will cause the chip internal voltage drop (IR drop) to be too high, and there is a risk of circuit function failure. In the related art, the method of reducing chip power consumption is mainly through low-power design and manufacturing of circuits, but it is difficult and will increase costs.

[0046] Based on this, an embodiment of the present disclosure provides a method for reducing power consumption of an imaging device, wherein the imaging device includes at least a pixel array composed of multiple SPAD pixels; the method includes: obtaining light intensity information and / or counting information, the light intensity information includes light intensity parameters or first type of photon counting values ​​of SPAD pixels in the pixel array, and the counting information includes second type of photon counting values ​​of SPAD pixels in the pixel array; wherein the first type of photon counting values ​​are related to ambient light intensity, and the second type of photon counting values ​​are related to imaging targets; judging imaging conditions based on the light intensity information or the counting information, and adjusting the photon counting rate of the SPAD pixels in the pixel array based on the judgment result. In this way, the present invention can judge the imaging conditions according to the light intensity parameters or the first type of photon counting values, and then adjust the photon counting rate of the SPAD pixel, or judge the imaging conditions by the second type of photon counting values, and then adjust the photon counting rate of the SPAD pixel, thereby adjusting the photon counting rate of the SPAD pixel under different imaging conditions, reducing the operating frequency of the SPAD pixel at high exposure intensity (such as strong ambient light), and thus reducing the power consumption of the imaging device; at low exposure intensity (such as darker environment), increasing the operating frequency of the SPAD pixel to capture more photons and improve the imaging effect.

[0047] The embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0048] In one embodiment of the present disclosure, see Figure 2 , which shows a flow chart of a method for reducing power consumption of an imaging device provided by an embodiment of the present disclosure. Figure 2 As shown, the method may include:

[0049] S101. Obtain light intensity information and / or counting information, where the light intensity information includes light intensity parameters or first-type photon counting values ​​of SPAD pixels in a pixel array, and the counting information includes second-type photon counting values ​​of SPAD pixels in the pixel array.

[0050] The first type of photon count value is related to the ambient light intensity, and the second type of photon count value is related to the imaging target; the imaging device at least includes a pixel array composed of a plurality of SPAD pixels.

[0051] Here, the imaging device may also be referred to as an imaging device, and the method provided in the embodiment of the present disclosure may specifically be a method for reducing the power consumption of a SPAD-based imaging device.

[0052] It should be noted that an additional photoelectric sensor may be provided to measure the ambient light intensity separately, and the light intensity parameter may be obtained to determine the light intensity information, or the first type of photon count value related to the ambient light intensity may be obtained to determine the light intensity information, and no specific limitation is made to this. Further, in this embodiment, it is not necessary to simultaneously obtain the light intensity parameter and the first type of photon count value. When the light intensity parameter is obtained to represent the light intensity information, it is not necessary to obtain the first type of photon count value to represent the light intensity information. Conversely, when the first type of photon count value is obtained to represent the light intensity information, it is not necessary to obtain the light intensity parameter to represent the light intensity information.

[0053] It should also be noted that in different application scenarios, a SPAD pixel may include only a SPAD device, or may include a SPAD device and a corresponding quenching circuit and a counting circuit, without specific limitation. The SPAD device is used to sense photons and generate pulse signals; the quenching circuit is used to quench the SPAD; and the counting circuit is used to count the pulse signals to obtain a photon count value.

[0054] It should also be noted that the first type of photon count value is related to the environment and can be used to judge the ambient light intensity. The larger the value of the first type of photon count value, the stronger the ambient light intensity. The second type of photon count value is related to the information of the imaging target itself. The imaging target can be imaged through the second type of photon count value. In the embodiment of the present disclosure, the process of SPAD pixels capturing photons to obtain the first type of photon count value or the second type of photon count value is:

[0055] (1) The SPAD in the waiting state is excited by light and generates photogenerated electrons. After causing an avalanche event, the quenching circuit works to extinguish the avalanche. The quenching circuit then recharges the SPAD to restore it to the waiting state.

[0056] (2) During the avalanche process, the quenching circuit will also generate a digital pulse signal to the downstream counting circuit. The counting circuit (regardless of asynchronous counting mode or synchronous counting mode) belongs to a digital circuit structure. After detecting the pulse signal generated by the quenching circuit, the photon count value increases by one.

[0057] (3) After the SPAD recovers, it waits for light excitation again, and the SPAD pixel unit performs processes (1) and (2) again. The above process is repeated during the exposure time.

[0058] It should be noted that each SPAD pixel has a corresponding independent counting circuit, and different SPAD pixels generally do not use the same counting circuit for counting. In order to simplify the circuit and improve chip integration, different SPAD pixels can also share the counting circuit, but different SPAD pixels need to be counted in time-sharing (or staggered) to avoid motion artifacts.

[0059] In some embodiments, the first type of photon count value includes the sum, average or median of the photon count values ​​of the SPAD pixels in the pixel array. Specifically, in practical applications, one of the sum, average and median of the photon count values ​​can be selected as the first type of photon count value according to actual conditions. It should be noted that when the above three types of values ​​are respectively used as the first type of photon count values, their corresponding standards for judging the light intensity information (return light intensity) are different. Exemplarily, the first type of photon count value can be the average value (C ) of the photon count values ​​of all or part of the SPAD pixels in the pixel array. avr ).

[0060] S102 , determining imaging conditions according to the light intensity information or the counting information, and adjusting the photon counting rate of the SPAD pixels in the pixel array according to the determination result.

[0061] It should be noted that, assuming that the light intensity of the optical target corresponding to a certain SPAD pixel is stronger, the more photons incident on this SPAD pixel during the exposure time, the more processes (1) and (2) will be triggered, and the higher the photon count value in the final counting circuit will be. Obviously, the higher the photon count value of the SPAD pixel, the higher the pixel count rate corresponding to the SPAD pixel. The pixel count rate can be understood as the counting frequency, which represents the photon count value per unit time, as shown in formula (1):

[0062] CR=C / T E (1);

[0063] Where CR represents the pixel count rate, C represents the photon count value, and T E Indicates exposure time.

[0064] It can be understood that if the unit power consumption of a SPAD pixel when it works once (i.e., the photon count value increases by one) is P0, then during the exposure process, the total power consumption of the SPAD pixel is P total As shown in formula (2):

[0065] P total =C×P0 (2);

[0066] Wherein, C represents the photon count value.

[0067] Combining formula (1) and formula (2), it can be seen that the total power consumption of the SPAD pixel during one exposure process is shown in formula (3):

[0068] P total =CR×T E ×P0 (3);

[0069] According to formula (3), by adjusting the photon count rate of the SPAD pixel, the total power consumption of the SPAD pixel in the pixel array can be adjusted.

[0070] Here, the photon counting rate of the SPAD pixel can also be understood as the pixel counting rate mentioned above.

[0071] It should also be noted that the imaging condition refers to the intensity of the ambient light or whether the counting circuit is in a saturated state. When it is determined that the ambient light intensity is large or the counting circuit is in a saturated state, the photon count rate of the SPAD pixel in the pixel array is correspondingly reduced; on the contrary, when it is determined that the counting circuit is in an unsaturated state and the ambient light intensity is small, the photon count rate of the SPAD pixel in the pixel array is increased. It can be understood that when the counting circuit is in a saturated state, it means that a large number of photons are captured by the SPAD pixel, which can also indirectly indicate that the ambient light intensity is strong. Among them, the counting circuit count saturation means that the counting circuit is full, the register included in the counting circuit has stored the maximum value, and the count value can no longer continue to increase.

[0072] In some embodiments, the counting information is used to determine the imaging conditions and to image the imaging target; the light intensity information and the counting information are acquired in the same frame or in different frames.

[0073] It should be noted that the counting information is used to judge the imaging conditions, which is actually to judge whether the counting circuit of the SPAD pixel is saturated, that is, to judge whether the counting value in the counting circuit has reached its maximum counting value; and the counting information is used to image the imaging target, which refers to the photon counting data (photon counting value) of imaging the imaging target.

[0074] In the disclosed embodiment, whether the light intensity information and the counting information are obtained in the same frame depends on the method of obtaining the light intensity information. Specifically, when the light intensity information is obtained by obtaining light intensity parameters through an additional photoelectric sensor, and when the light intensity information is obtained by obtaining the first type of photon count values ​​of some SPAD pixels in the pixel array, the light intensity information and the counting information can be obtained in the same frame; when the light intensity information is obtained by obtaining the first type of photon count values ​​of all SPAD pixels in the pixel array, the light intensity information and the counting information need to be obtained in different frames. In this way, it can be ensured that the judgment process of the imaging conditions and the collection process of the imaging data will not interfere with each other, ensuring the functional stability of the imaging device. Here, one frame refers to a complete imaging process, including exposure, data transfer, data processing and other steps.

[0075] In some embodiments, when light intensity information and counting information are acquired in different frames, the SPAD pixels used to acquire the first type of photon count value are the same as those used to acquire the second type of photon count value, and the light intensity information is acquired in the previous frame and the counting information is acquired in the next frame.

[0076] It should be noted that this is a situation in which light intensity information is acquired, determined, and the photon count rate of the SPAD pixel is adjusted, that is, the light intensity information is acquired and determined in the previous frame, and the photon count rate of the SPAD pixel is adjusted in the current frame according to the light intensity information of the previous frame. This situation requires imaging once, and the SPAD pixels that acquire light intensity information and acquire count information can be reused, that is, the SPAD pixels that acquire light intensity information and are used to image the imaging target can be reused. Here, when the light intensity information and the count information are acquired in different frames, the first type of photon count value acquired can be the average value of the photon count values ​​of all SPAD pixels in the pixel array (C avr ).

[0077] It should also be noted that when the light intensity information and the counting information are acquired in different frames, it is necessary to first determine the imaging conditions based on the light intensity information, and then adjust the photon counting rate of the SPAD pixel based on the determination result to image the imaging target. Therefore, the light intensity information is acquired in the previous frame, and then the counting information is acquired in the next frame. It is understandable that the frame time for acquiring the light intensity information and the frame time for imaging the imaging target may be different. Specifically, the frame time for acquiring the light intensity information may be shorter than the frame time for imaging the imaging target to improve imaging efficiency.

[0078] It should also be noted that generally two frames are used to obtain light intensity information and count information respectively, one frame is used to obtain light intensity information, and one frame is used to obtain count information and image the imaging target. If there are more than two frames, it may be possible to use multiple frames to obtain light intensity information, so that more accurate light intensity information can be determined, or it may be possible to use multiple frames to image the imaging target, and the imaging data of multiple frames can be compounded to make the imaging details better. In the embodiments of the present disclosure, the ratio of the number of frames for obtaining light intensity information and imaging the imaging target is not specifically limited.

[0079] In other embodiments, when the light intensity information and the counting information are acquired in the same frame, the SPAD pixels used to acquire the first type of photon counting values ​​and the SPAD pixels used to acquire the second type of photon counting values ​​are different, and the light intensity information and the counting information are acquired simultaneously.

[0080] It should be noted that this is another scenario of acquiring and judging light intensity information and adjusting the photon count rate of SPAD pixels, that is, acquiring and judging light intensity information and adjusting the photon count rate of SPAD pixels in the same frame. This scenario also requires imaging once, and light intensity information is acquired simultaneously during the imaging of the imaging target, but the SPAD pixels that acquire light intensity information and acquire count information cannot be reused, that is, the SPAD pixels that acquire light intensity information and are used to image the imaging target cannot be reused. Here, when the light intensity information and the count information are acquired in the same frame, the first type of photon count value acquired can be the average value of the photon count values ​​of some SPAD pixels in the pixel array (C avr ).

[0081] In the disclosed embodiment, when the light intensity information and the counting information are acquired in the same frame, the total time of the imaging condition judgment and the imaging process can be shortened. It is understandable that the light intensity information can be obtained by obtaining the light intensity parameters through an additional photoelectric sensor, or by obtaining the first type of photon count values ​​of some SPAD pixels in the pixel array. It should be noted that when the light intensity parameters are obtained by the aforementioned second method (i.e., obtaining the first type of photon count values ​​of some SPAD pixels), the acquisition of light intensity information and counting information can be performed simultaneously, that is, while obtaining the light intensity information to judge the imaging conditions, the photon count rate of the SPAD pixels of the pixel array is adjusted, real-time judgment and real-time adjustment, and imaging is more efficient.

[0082] In some embodiments, light intensity information and counting information can be acquired in the same frame, but the light intensity information can be acquired earlier than imaging the imaging target. That is, after acquiring the light intensity information and judging the imaging conditions, the photon counting rate of the SPAD pixel is adjusted according to the judgment result, and then the imaging target is imaged. This can reduce the probability of repeatedly adjusting the photon counting rate of the SPAD pixel due to unstable factors in the process of acquiring the light intensity information, thereby improving the imaging efficiency.

[0083] In some embodiments, when the light intensity information includes a light intensity parameter, the light intensity parameter is compared with a first threshold value. When the first threshold value has only one threshold value, if the light intensity parameter is greater than or equal to the first threshold value, the photon count rate of the SPAD pixel in the pixel array is reduced.

[0084] It should be noted that the photon count rate of all or part of the SPAD pixels in the pixel array can be lowered. Specifically, it can be determined based on the difference between the light intensity parameter and the first threshold. For example, if the difference between the two is large, it means that the photon count rate of the SPAD pixel is too high, then the photon count rate of all SPAD pixels in the pixel array can be lowered; conversely, only the photon count rate of part of the SPAD pixels in the pixel array can be lowered. The photon count rate of all or part of the SPAD pixels can be lowered according to actual conditions, and there is no specific limitation on this.

[0085] The first threshold may include multiple thresholds, that is, the first threshold may include at least one light intensity threshold. In some embodiments, the imaging condition is judged according to the light intensity information, and the photon count rate of the SPAD pixel in the pixel array is adjusted according to the judgment result, including:

[0086] The light intensity parameter is compared with at least one light intensity threshold. If the light intensity parameter is greater than or equal to the light intensity threshold, the photon count rate of the SPAD pixels in the pixel array is lowered; if the light intensity parameter is less than the light intensity threshold, the photon count rate of the SPAD pixels in the pixel array is increased.

[0087] In the disclosed embodiment, different light intensity threshold ranges may correspond to different optimal photon counting rates. Specifically, a large number of imaging tests may be performed to obtain the optimal photon counting rate corresponding to the light intensity parameter range, and then a mapping relationship table of "light intensity parameter-photon counting rate" may be formed. In the actual imaging process, after obtaining the light intensity parameter, the light intensity parameter range to which the light intensity parameter belongs may be directly found in the mapping relationship table, and then the optimal photon counting rate corresponding to the light intensity parameter range may be found, thereby adjusting the photon counting rate of the SPAD pixel in the pixel array to the optimal value.

[0088] Among them, after obtaining the light intensity parameter, by finding the light intensity parameter range to which the light intensity parameter belongs in the mapping relationship table, it can be understood as: reducing at least one light intensity threshold in accordance with the numerical value, comparing the light intensity parameter with these light intensity thresholds in turn, if the light intensity parameter is already greater than or equal to the maximum light intensity threshold, then lowering the photon count rate of the SPAD pixel to the photon count rate corresponding to the light intensity parameter range where the maximum light intensity threshold is located; if the light intensity parameter is less than the maximum light intensity threshold, then comparing with the next smaller light intensity threshold until the light intensity parameter is greater than or equal to a certain light intensity threshold and less than the previous light intensity threshold, then determining the light intensity parameter range to which the light intensity parameter belongs as between the light intensity threshold and the previous light intensity threshold, and then lowering the photon count rate of the SPAD pixel to the photon count rate corresponding to the light intensity parameter range.

[0089] Exemplarily, if the light intensity parameter is greater than or equal to light intensity threshold 1 and less than light intensity threshold 2, the photon count rate of the SPAD pixel is adjusted to the photon count rate corresponding to the light intensity parameter range from light intensity threshold 1 to light intensity threshold 2.

[0090] In addition, if the light intensity parameter is less than the minimum light intensity threshold, the photon count rate of the SPAD pixel is increased to the photon count rate corresponding to the light intensity parameter range where the minimum light intensity threshold is located. In this way, the adjustment can be turned on when the average light intensity is weak, the power consumption increase is within an acceptable range, and the dynamic range can also be increased.

[0091] It should be noted that the photon counting rate of all or part of the SPAD pixels can be increased according to actual conditions, and there is no specific limitation on this.

[0092] In some embodiments, when the light intensity information includes a first type of photon count value, the first type of photon count value is compared with a second threshold value (C th_hi In the case where the second threshold has only one threshold, if the first type of photon count value is greater than or equal to the second threshold, the photon count rate of the SPAD pixel in the pixel array is reduced.

[0093] It should be noted that the photon count rate of all or part of the SPAD pixels in the pixel array can be lowered. Specifically, it can be determined based on the difference between the first type of photon count value and the second threshold. For example, if the difference between the two is large, it means that the photon count rate of the SPAD pixel is too high, then the photon count rate of all SPAD pixels in the pixel array can be lowered; conversely, only the photon count rate of part of the SPAD pixels in the pixel array can be lowered. The photon count rate of all or part of the SPAD pixels can be lowered according to actual conditions, and there is no specific limitation on this.

[0094] The second threshold may include multiple thresholds, that is, the second threshold may include at least one judgment threshold (C th0 , C th1 , C th2 …), in some embodiments, determining an imaging condition according to the light intensity information, and adjusting the photon count rate of a SPAD pixel in the pixel array according to the determination result, includes:

[0095] The first type of photon count value is compared with at least one judgment threshold. If the first type of photon count value is greater than or equal to the judgment threshold, the photon count rate of the SPAD pixels in the pixel array is lowered; if the first type of photon count value is less than the judgment threshold, the photon count rate of the SPAD pixels in the pixel array is increased.

[0096] In the disclosed embodiment, different judgment threshold ranges may correspond to different optimal photon count rates. Specifically, a large number of imaging tests may be performed to obtain the optimal photon count rate corresponding to the first-class photon count value range, and then a mapping relationship table of "first-class photon count value-photon count rate" may be formed. In the actual imaging process, after obtaining the first-class photon count value, the first-class photon count value range to which the first-class photon count value belongs may be directly found in the mapping relationship table, and then the optimal photon count rate corresponding to the first-class photon count value range may be found, thereby adjusting the photon count rate of the SPAD pixel in the pixel array to the optimal value.

[0097] Among them, after obtaining the first-class photon count value, by finding the first-class photon count value range to which the first-class photon count value belongs in the mapping relationship table, it can be understood as: reducing at least one judgment threshold in accordance with the numerical value, and comparing the first-class photon count value with these judgment thresholds in turn; if the first-class photon count value is already greater than or equal to the maximum judgment threshold, then lowering the photon count rate of the SPAD pixel to the photon count rate corresponding to the first-class photon count value range where the maximum judgment threshold is located; if the first-class photon count value is less than the maximum judgment threshold, then comparing it with the next smaller judgment threshold until the first-class photon count value is greater than or equal to a certain judgment threshold and less than the previous judgment threshold, then determining the first-class photon count value range to which the first-class photon count value belongs to be between the judgment threshold and the previous judgment threshold, and then lowering the photon count rate of the SPAD pixel to the photon count rate corresponding to the first-class photon count value range.

[0098] Exemplarily, if the first type of photon count value is greater than or equal to judgment threshold 1 and less than judgment threshold 2, the photon count rate of the SPAD pixel is adjusted to the photon count rate corresponding to the first type of photon count value range from judgment threshold 1 to judgment threshold 2.

[0099] In addition, if the first-category photon count value is less than the minimum judgment threshold, the photon count rate of the SPAD pixel is increased to the photon count rate corresponding to the first-category photon count value range where the minimum judgment threshold is located. In this way, the adjustment can be turned on when the average light intensity is weak, the power consumption increase is within an acceptable range, and the dynamic range can also be increased.

[0100] It should be noted that the photon counting rate of all or part of the SPAD pixels can be increased according to actual conditions, and there is no specific limitation on this.

[0101] See also Figure 3 , which shows a schematic diagram of the relationship between light intensity (light power) and photon count rate provided by an embodiment of the present disclosure. Figure 3 As shown, the horizontal axis is the optical power (P th), the ordinate is the photon counting rate (CR), and A and B represent different SPAD pixels.

[0102] It should be noted that light intensity and light power have a positive correlation. The greater the light power, the stronger the light intensity; conversely, the smaller the light power, the weaker the light intensity.

[0103] From formula (1), it can be deduced that the photon count value can be obtained by formula (4):

[0104] C=CR×T E (4);

[0105] Where C represents the photon count value, CR represents the photon count rate, and T E Indicates exposure time.

[0106] As shown in formula (4), reducing the photon counting rate CR can suppress the photon counting value.

[0107] It should also be noted that the photon count rate CR has a negative correlation with the dead time of the SPAD pixel. Increasing the dead time can reduce the photon count rate. Under the same light intensity conditions (i.e., the same optical power), because the dead time of SPAD A is smaller than the dead time of SPAD B (T C A <T C B), so the photon counting rate of SPAD A is greater than the photon counting rate of SPAD B (CR max A>CR max B).

[0108] It should be noted that during the process of SPAD triggering, quenching, and recovery, it will not be triggered by other photons. During this period of time, the photons incident on the SPAD will not cause the processes (1) and (2) described above, and the pulse signal will not be counted. This period of time is called the dead time T C Among them, the increase in the dead time of the SPAD pixel will cause the photon count rate to decrease. The stronger the light intensity, the greater the decrease in the photon count rate.

[0109] like Figure 3 As shown, P th C represents that when the optical power of SPAD A and SPAD B is low, even though their dead time is different, their photon counting rates are basically the same. That is to say, in a low-light environment, the photon counting rate is less affected by the dead time, and the photon counting rates of SPAD A and SPAD B are basically the same. As the light intensity increases, the dead time of the SPAD pixel has a greater impact on its photon counting rate. The shorter the dead time, the greater the photon counting rate, so the photon counting rate of SPAD B is less than that of SPAD A.

[0110] Specifically, when the optical power is low, due to the low light intensity and small number of photons, the number of photons reaching the SPAD is very small, and the time interval between two adjacent photons reaching the SPAD is likely to be much longer than the dead time of SPAD A and SPAD B. Even if the dead time of SPAD is increased, the photon count rate will not change or will change very little. Therefore, when the optical power is low, even if the dead time of SPAD A and SPAD B is different, the number of photons they respond to per unit time is close, so the photon count rates of SPAD A and SPAD B are similar.

[0111] As the light intensity increases, the number of photons increases. The more photons reach the SPAD, the more photons will arrive in a concentrated manner. The time interval between two adjacent photons arriving at the SPAD is very small, which may be less than the dead time of the SPAD. At this time, the dead time of the SPAD will directly affect the number of photons that the SPAD can respond to per unit time. If the dead time of the SPAD is increased, most of the concentrated photons will fall into the dead time and cannot be counted, and the photon counting rate will drop significantly. Because the dead time of SPAD A is smaller than the dead time of SPAD B (T C A <T C B), so the photon counting rate of SPAD B is less than that of SPAD A. Therefore, by judging the target light intensity and adjusting the dead time of SPAD pixels in real time, power consumption can be reduced.

[0112] In some embodiments, increasing the photon count rate of a SPAD pixel in a pixel array includes:

[0113] Reducing the dead time of SPAD pixels in a pixel array;

[0114] Reduce the photon count rate of the SPAD pixels in the pixel array, including:

[0115] Increase the dead time of the SPAD pixels in the pixel array.

[0116] It should also be noted that the present embodiment may have multiple dead time levels corresponding to the multiple light intensity thresholds in the aforementioned first threshold and the multiple judgment thresholds in the second threshold, that is, a "light intensity parameter-photon count rate-dead time" mapping relationship table or a "first type of photon count value-photon count rate-dead time" mapping relationship table may be obtained through a large number of tests. Exemplarily, a light intensity parameter range corresponds to a dead time one-to-one, and when the light intensity parameter falls into a certain light intensity parameter range, the dead time of the SPAD pixel is adjusted to the value corresponding to the light intensity parameter range. Similarly, a first type of photon count value range corresponds to a dead time one-to-one, and when the first type of photon count value falls into a first type of photon count value range, the dead time of the SPAD pixel is adjusted to the value corresponding to the first type of photon count value range.

[0117] In addition, in the embodiment of the present disclosure, increasing the dead time of the SPAD pixel can not only reduce the total power consumption P by reducing the photon counting rate, but also reduce the total power consumption P by reducing the photon counting rate. total , and the unit power consumption P0 can also be reduced.

[0118] In some embodiments, determining an imaging condition based on the counting information, and adjusting the photon counting rate of a SPAD pixel in the pixel array based on the determination result, includes:

[0119] The second type of photon count value is compared with the count threshold, and if the second type of photon count value is equal to the count threshold, the photon count rate of the SPAD pixels in the pixel array is reduced to 0.

[0120] It should be noted that the counting threshold (C max ) represents the upper limit of the count value when the counting circuit is full or the threshold value when it is in a saturated state, that is, the maximum value that the register included in the counting circuit can store.

[0121] Here, when the second type photon count value is equal to the count threshold, it indicates that the counting circuit is in a saturation state.

[0122] If the unit power consumption of a SPAD pixel when it works once (i.e. the photon count value increases by one) is P0, then during the exposure process before the counting circuit is saturated, the total power consumption of the SPAD pixel is P total It can be obtained by the formula (2) mentioned above. During the exposure process after the counting circuit is in the saturation state, because the counting circuit is already saturated, new avalanche events and quenching processes in the SPAD pixel will not increase the photon count value of the counting circuit, but will increase power consumption. Therefore, after the counting circuit is in the saturation state, the photon count rate of the SPAD pixel in the pixel array needs to be reduced to 0.

[0123] It should also be noted that when the ambient light intensity is very strong, the photons of the ambient light may also saturate the counting circuit in a very short time. Specifically, during the imaging process, the pixel array receives photons related to the imaging target as well as photons of the ambient light. The photon count value counted by the counting circuit includes the photon count value of the imaging target as well as the photon count value of the ambient light.

[0124] In some embodiments, lowering the photon counting rate of a SPAD pixel in the pixel array to zero includes: turning off a counting circuit of the SPAD pixel.

[0125] In some embodiments, the counting circuit may include a quenching circuit, and shutting down the counting circuit may specifically be shutting down the quenching circuit.

[0126] It should also be noted that in addition to turning off the quenching circuit of the SPAD pixel, the exposure enable signal of the SPAD pixel can also be turned off, or the reverse bias voltage at the two poles of the SPAD pixel can be lowered or directly removed. The embodiment of the present disclosure does not specifically limit the specific method, as long as the SPAD pixel can be turned off.

[0127] The embodiments of the present disclosure provide a method for reducing the power consumption of an imaging device. The method can overcome the defect of excessively high power consumption of a SPAD-based PCI image sensor under strong ambient light by judging the target light intensity in real time and adjusting the dead time of a SPAD pixel through feedback, or by shutting down a quenching circuit after a counting circuit of the SPAD pixel is in a saturated state, thereby reducing the power consumption of the image sensor.

[0128] In another embodiment of the present disclosure, see Figure 4 , which shows a schematic diagram of the composition structure of a circuit for reducing power consumption of an imaging device provided by an embodiment of the present disclosure. Figure 4 As shown, the imaging device 20 at least includes a pixel array 21 composed of a plurality of SPAD pixels; the circuit 30 for reducing the power consumption of the imaging device may include an acquisition circuit 31, a counting circuit 32 and an adjustment circuit 33; wherein:

[0129] An acquisition circuit 31 is used to acquire light intensity information, where the light intensity information includes a light intensity parameter or a first type of photon count value of a SPAD pixel in the pixel array 21, where the first type of photon count value is related to the ambient light intensity;

[0130] A counting circuit 32, used for acquiring counting information, the counting information including second-type photon counting values ​​of SPAD pixels in the pixel array 21, the second-type photon counting values ​​being related to the imaging target;

[0131] The adjustment circuit 33 is used to determine the imaging condition according to the light intensity information or the counting information, and adjust the photon counting rate of the SPAD pixels in the pixel array 21 according to the determination result.

[0132] It should be noted that the circuit 30 for reducing power consumption of an imaging device provided in the embodiment of the present disclosure applies the aforementioned method for reducing power consumption of an imaging device.

[0133] It should also be noted that the present embodiment does not need to simultaneously acquire the light intensity parameter and the first type of photon count value. If the acquisition circuit 31 acquires the first type of photon count value to represent the light intensity information, that is, the light intensity information is acquired through the SPAD pixels in the pixel array 21, then the counting circuit 32 of the pixel array 21 can also be reused as the acquisition circuit 31; if the acquisition circuit 31 acquires the light intensity parameter to represent the light intensity information, an additional photoelectric sensor and a corresponding circuit are used to implement it. Exemplarily, the specific implementation of the disclosed embodiment is described in detail by taking the acquisition circuit 31 acquiring the first type of photon count value to represent the light intensity information as an example.

[0134] See also Figure 5 , which shows a specific structural diagram of a circuit for reducing power consumption of an imaging device provided by an embodiment of the present disclosure Figure 1 .

[0135] In the embodiment of the present disclosure, the case where the first type of photon count value is used as the light intensity information, the imaging condition is determined according to the light intensity information, and the photon count rate of the SPAD pixel is adjusted in the current frame according to the light intensity information of the previous frame is taken as an example. Figure 5 As shown, the circuit 30 includes a readout module 41, a signal processing module 42 and a quenching control module 43, the pixel array 21 is connected to the readout module 41, the readout module 41 is connected to the signal processing module 42, and the quenching control module 43 is connected to the signal processing module 42 and the pixel array 21.

[0136] Here, the first type of photon count value representing the light intensity information acquired in the previous frame is transmitted to the signal processing module 42 via the readout module 41 .

[0137] It should be noted that, illustratively, the signal processing module 42 counts and analyzes the average value (C avr ). If C avr Greater than the set second threshold (C th_hi ), the signal processing module 42 sends an adjustment signal to the quenching control module 43 in the current frame, and the quenching control module 43 increases the dead time of all or part of the SPAD pixels in the pixel array 21 to T Cth_hi Furthermore, the second threshold (C th_hi ) can include multiple programmable judgment thresholds C th0 , C th1 , C th2 ..., that is, you can set multiple programmable judgment thresholds C th0 , Cth1 , C th2 ...and the corresponding multi-speed dead time T Cth0 , T Cth1 , T Cth2 …, thus the dead time of the SPAD pixel can be adjusted to a corresponding value according to the compared judgment threshold. The specific judgment and setting methods can be referred to the above content, and the embodiments of the present disclosure will not be repeated.

[0138] It should also be noted that the quenching control module 43 adjusts the dead time of the SPAD pixel by generating a control signal and outputting it to the pixel array 21. The control signal is a signal for adjusting the dead time of the SPAD pixel.

[0139] It should also be noted that all SPAD pixels share a readout module 41 and a signal processing module 42. Figure 6 , which shows a schematic diagram of the composition structure of a data readout circuit of a pixel array provided by an embodiment of the present disclosure. Figure 6 As shown, the photon count values ​​on the SPAD pixels in the pixel array 21 are transferred row by row to the shift register module (corresponding to Figure 5 The data is then transferred from the readout module 41 to the signal processing module 42 by the shift register module.

[0140] See also Figure 7 , which shows a specific structural diagram of a circuit for reducing power consumption of an imaging device provided by an embodiment of the present disclosure Figure 2 .

[0141] In the embodiment of the present disclosure, the case where the first type of photon count value is used as the light intensity information, the imaging condition is determined according to the light intensity information, and the light intensity information is obtained and the dead time of the SPAD pixel is adjusted in the same frame is taken as an example. Figure 7 As shown, SPAD pixels 211 (only one number is shown in the figure) in a partial area of ​​the pixel array 21 are selected to obtain the first type of photon count value as light intensity information; during the exposure process, the selected SPAD pixels 211 are transmitted to the external signal processing module 42 through the readout channel 44; the signal processing module 42 counts and analyzes the data of the selected SPAD pixels 211, and extracts characteristic parameters, such as the average value (C ) of the first type of photon count value of the SPAD pixels 211. avr ).

[0142] It should be noted that there is no limit on the size of the "partial area", as long as there are SPAD pixels 211 for measuring light intensity. In addition, the SPAD pixels 211 in the partial area can be dispersed in the pixel array 21 to avoid the problem of inaccurate single-point light intensity. Preferably, the edge SPAD pixels in the pixel array 21 are used for light intensity measurement to reduce the photon sampling error of the light intensity measurement; and the center SPAD pixels in the pixel array 21 are used for photon counting imaging.

[0143] It should also be noted that the dead time of all SPAD pixels in the pixel array 21 can be increased, and the dead time of all SPAD pixels performing imaging in the pixel array 21 (i.e., SPAD pixels except SPAD pixel 211) can also be increased, without specific limitation.

[0144] It should also be noted that Figure 7 The readout channel 44 in Figure 5 The readout modules 41 in the embodiment may be the same or different, and there is no specific limitation on this.

[0145] See also Figure 8 , which shows a specific structural diagram of a circuit for reducing power consumption of an imaging device provided by an embodiment of the present disclosure Figure 3 .

[0146] In the embodiments of the present disclosure, Figure 8 As shown, the counting circuit 32 may include a counter 321 and a quenching module 322 in addition to the SPAD pixel, wherein the counter 321 may include a plurality of cascaded registers 3211 (only one number is shown in the figure), wherein the cascade connection of the plurality of registers 3211 is a conventional circuit structure in the related art, and the circuit structure of the quenching module 322 may adopt a common quenching structure in the related art, which will not be elaborated in the embodiments of the present disclosure.

[0147] It should be noted that the control module 53 is used to generate an exposure enable signal. During the period when the exposure enable signal is valid, the pixel array 21 is in an exposure state and can sense photons to generate photon count values. When the exposure enable signal is invalid, the SPAD pixel exposure ends and can no longer sense photons. When the exposure enable signal is invalid, the pixel array 21 is in a data transfer mode and transfers and reads out the photon count values ​​row by row.

[0148] Here, the counter 321 is composed of a plurality of registers 3211, which are used to cache the photon count value of the SPAD pixel. Among them, the first register 3211 (register D LSB ) is used to store the least significant bit (LSB) value. The last register 3211 (register D MSB) is used to store the most significant bit (MSB) value. When multiple registers 3211 are full, register D MSB When the Q-end output of becomes "1", it indicates that the counter 321 has been fully counted, and subsequent photons incident on the SPAD pixel cannot be counted. The photon count value remains unchanged but power consumption exists, that is, the counting circuit 32 is saturated, so the counting circuit 32 needs to be turned off.

[0149] It should also be noted that the present embodiment does not specifically limit the counting method, and both asynchronous counting method and synchronous counting method are possible, that is, multiple registers 3211 can form a ripple asynchronous counting circuit or a synchronous counting circuit. Figure 8 or Fig. 9 As shown, the counting circuit 32 is specifically a traveling wave asynchronous counting circuit.

[0150] It should be noted that register D MSB The Q-end signal of register D is used as an overflow flag. MSB After the Q-end signal of is flipped to "1", it can be used as an overflow flag, so that the counting circuit 32 no longer works; in addition, it can also turn off the enable signal of the quenching module 322, so that the SPAD pixel no longer generates an avalanche event.

[0151] In the embodiment of the present disclosure, since the exposure enable signal and the overflow flag can shut down the quenching module 322 in some cases, the exposure enable signal and the overflow flag can be operated by a logic circuit and then the quenching enable signal can be output to the quenching module 322. The quenching enable signal enables the quenching module 322 to work according to the following requirements:

[0152] Under the premise that the exposure enable signal is valid: when the overflow flag is valid (register D MSB When the Q-end signal of the register D is output "1", the quenching enable signal is invalid, and the quenching module 322 is turned off; when the overflow flag is invalid (register D MSB When the Q-end signal outputs "0", the quenching enable signal is valid, and the quenching module 322 can quench the SPAD pixel;

[0153] Under the premise that the exposure enable signal is invalid: no matter whether the overflow flag is valid or invalid, the quenching enable signal is invalid, and the quenching module 322 is turned off.

[0154] It should be noted that the exposure enable signal is valid, which means that the SPAD pixels in the pixel array 21 are in an exposure state and can respond to photons; the quenching enable signal is valid, which means that the quenching module 322 can quench the SPAD pixels and output a pulse signal.

[0155] Specifically, Figure 8 or Fig. 9 As shown, the input terminal of the quenching module 322 is set to be connected to the register D MSB The Q end of the quenching module 322 is connected to the quenching closing module 51, and the output end of the quenching module 322 is set to the register D LSB The connected counting closing module 52. The quenching closing module 51 and the counting closing module 52 are both a circuit composed of logic gates, and the logic gates of the quenching closing module 51 can make the quenching module 322 work according to the above requirements, and the specific logic is not limited in this embodiment.

[0156] The input end of the counting closing module 52 is connected to the output end of the quenching module 322 and the register D MSB The Q terminal of the counting shutdown module 52 is connected to the output terminal of the register D LSB The clock end of the counting shutdown module 52 can make the counter work according to the following requirements:

[0157] When the overflow flag is invalid (register D MSB Under the premise that the Q terminal of the quenching module 322 outputs a pulse signal, the counter 321 counts once;

[0158] When the overflow flag is valid (register D MSB Under the premise that the Q terminal of the quenching module 322 outputs "1", the counter 321 does not count regardless of whether the quenching module 322 outputs a pulse signal.

[0159] It should also be noted that Fig. 9 The corresponding logic gates in the quenching closing module 51 and the counting closing module 52 shown in the figure are only examples and can be selected according to actual conditions, and no specific limitation is made to this.

[0160] The disclosed embodiment uses two solutions to effectively reduce the problem of excessive power consumption when the resolution of the SPAD-based PCI image sensor is increased or the light intensity is too strong. On the one hand, the incident light intensity is dynamically and real-time judged. When the light intensity is too strong, the photon count rate is reduced by adjusting the dead time of the SPAD pixel, thereby lowering the photon count value within the exposure time. In this way, not only the overall power consumption can be reduced, but also the transient power consumption is reduced due to the decrease in the photon count rate. On the other hand, the structure of the counting circuit 32 is improved, and the last register D in the counting circuit 32 is changed to MSB As the overflow protection register, use the overflow protection register D MSB The Q-end signal of the counting circuit 32 is used to turn off the counting circuit 32 after the counting circuit 32 reaches saturation. Specifically, the quenching module 322 is turned off so that the SPAD pixel no longer undergoes avalanche and counting processes (i.e., processes (1) and (2) described above), thereby avoiding power consumption waste after the counting circuit 32 reaches saturation.

[0161] It should be noted that these two solutions can be used simultaneously and are applicable to pixel arrays 21 of any size, and are also applicable to synchronous counting methods or asynchronous counting methods, without any specific limitation. In short, these two solutions do not require additional low-power design overhead, and are automatically operated in real time during the imaging process, which can reduce the power consumption of the imaging device 20.

[0162] In another embodiment of the present disclosure, see Fig.10 , which shows a schematic diagram of the composition structure of an imaging device provided by an embodiment of the present disclosure. Fig.10 As shown, the imaging device 20 includes a pixel array 21 composed of a plurality of SPAD pixels and the aforementioned circuit 30 for reducing power consumption of the imaging device.

[0163] The imaging device 20 applies the aforementioned method for reducing the power consumption of the imaging device.

[0164] In the embodiment of the present disclosure, the imaging device 20 includes the aforementioned circuit 30 and has at least the same advantages as the circuit 30 , which can reduce the power consumption of the imaging device 20 and enable the imaging device 20 to work normally.

[0165] Details not disclosed in the embodiments of the present disclosure may be understood by referring to the description of the aforementioned embodiments.

[0166] The above description is only a preferred embodiment of the present disclosure and is not intended to limit the protection scope of the present disclosure.

[0167] It should be noted that in the present disclosure, the terms "include", "comprises" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "includes a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0168] The serial numbers of the above-mentioned embodiments of the present disclosure are only for description and do not represent the advantages or disadvantages of the embodiments.

[0169] The methods disclosed in several method embodiments provided in the present disclosure can be arbitrarily combined without conflict to obtain new method embodiments.

[0170] The features disclosed in several product embodiments provided in the present disclosure can be arbitrarily combined without conflict to obtain new product embodiments.

[0171] The features disclosed in several method or device embodiments provided in the present disclosure may be arbitrarily combined without conflict to obtain new method embodiments or device embodiments.

[0172] The above is only a specific embodiment of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present disclosure, which should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. A method for reducing power consumption of an imaging device, characterized in that: The imaging device at least comprises a pixel array composed of a plurality of SPAD pixels; the method comprises: Acquire light intensity information and / or counting information, wherein the light intensity information includes a light intensity parameter or a first type of photon counting value of the SPAD pixel in the pixel array, and the counting information includes a second type of photon counting value of the SPAD pixel in the pixel array; wherein the first type of photon counting value is related to the ambient light intensity, and the second type of photon counting value is related to the imaging target; An imaging condition is determined according to the light intensity information or the counting information, and a photon counting rate of the SPAD pixel in the pixel array is adjusted according to the determination result.

2. The method according to claim 1, characterized in that The counting information is used for judging the imaging condition and for imaging the imaging target; the light intensity information and the counting information are acquired in the same frame or in different frames.

3. The method according to claim 2, characterized in that When the light intensity information and the counting information are acquired in different frames, the SPAD pixels used to acquire the first type of photon counting value and the second type of photon counting value are the same, and the light intensity information is acquired in the previous frame and the counting information is acquired in the next frame.

4. The method according to claim 2, characterized in that: When the light intensity information and the counting information are acquired in the same frame, the SPAD pixels used to acquire the first type of photon counting values ​​and the second type of photon counting values ​​are different, and the light intensity information and the counting information are acquired simultaneously.

5. The method according to claim 1, characterized in that Determining the imaging condition according to the light intensity information, and adjusting the photon counting rate of the SPAD pixel in the pixel array according to the determination result, includes: The light intensity parameter is compared with at least one light intensity threshold. If the light intensity parameter is greater than or equal to the light intensity threshold, the photon counting rate of the SPAD pixel in the pixel array is lowered; if the light intensity parameter is less than the light intensity threshold, the photon counting rate of the SPAD pixel in the pixel array is increased.

6. The method according to claim 1, characterized in that Determining the imaging condition according to the light intensity information, and adjusting the photon counting rate of the SPAD pixel in the pixel array according to the determination result, includes: The first type of photon count value is compared with at least one judgment threshold. If the first type of photon count value is greater than or equal to the judgment threshold, the photon count rate of the SPAD pixel in the pixel array is lowered; if the first type of photon count value is less than the judgment threshold, the photon count rate of the SPAD pixel in the pixel array is increased.

7. The method according to claim 5 or 6, characterized in that: The step of increasing the photon count rate of the SPAD pixels in the pixel array comprises: reducing the dead time of the SPAD pixels in the pixel array; The step of lowering the photon count rate of the SPAD pixels in the pixel array comprises: The dead time of the SPAD pixels in the pixel array is increased.

8. The method according to claim 1, characterized in that Determining the imaging condition according to the counting information, and adjusting the photon counting rate of the SPAD pixel in the pixel array according to the determination result, includes: The second type of photon count value is compared with a count threshold, and if the second type of photon count value is equal to the count threshold, the photon count rate of the SPAD pixel in the pixel array is reduced to 0.

9. The method according to claim 1, characterized in that: The first type of photon count values ​​includes a sum, an average or a median of photon count values ​​of the SPAD pixels in the pixel array.

10. A circuit for reducing power consumption of an imaging device, characterized in that: The imaging device at least comprises a pixel array composed of a plurality of SPAD pixels; the circuit comprises an acquisition circuit, a counting circuit and an adjustment circuit; wherein: The acquisition circuit is used to acquire light intensity information, wherein the light intensity information includes a light intensity parameter or a first type of photon count value of the SPAD pixel in the pixel array, wherein the first type of photon count value is related to the ambient light intensity; The counting circuit is used to obtain counting information, wherein the counting information includes a second type of photon counting value of the SPAD pixel in the pixel array, and the second type of photon counting value is related to an imaging target; The adjustment circuit is used to determine the imaging condition according to the light intensity information or the counting information, and adjust the photon counting rate of the SPAD pixel in the pixel array according to the determination result.

Images