CN117784154A

CN117784154A - ToF ranging method, ranging equipment and storage medium

Info

Publication number: CN117784154A
Application number: CN202311696847.3A
Authority: CN
Inventors: 张睿; 张玺; 董志兵; 衷翰昆
Original assignee: Wuhan Arctic Core Microelectronics Co ltd
Current assignee: Wuhan Arctic Core Microelectronics Co ltd
Priority date: 2023-12-11
Filing date: 2023-12-11
Publication date: 2024-03-29

Abstract

The embodiment of the disclosure provides a ToF ranging method, ranging equipment and a storage medium. The ToF ranging method includes: determining response parameters of the SPAD array to the light pulse reflected by the target to be detected when the light pulse reflected by the target to be detected is responded at least once; the response parameter is related to the intensity of the detected light pulse; comparing the response parameter with a preset parameter range to judge whether to adjust the opening quantity of the SPAD pixels in the SPAD array; when the response parameter does not fall into the preset parameter range, adjusting the opening number of the SPAD pixels in the SPAD array; and when the response parameter falls into a preset parameter range, not adjusting the opening quantity of the SPAD pixels in the SPAD array.

Description

ToF ranging method, ranging equipment and storage medium

Technical Field

The present disclosure relates to the field of ranging, and in particular, to a ToF ranging method, ranging apparatus, and storage medium.

Background

The photon Flight Time (ToF) ranging method is to emit light pulses to a target to be measured, and the light pulses reach the target to be measured and then are reflected back to a detection end. In practical application, a plurality of light pulses are generally emitted to generate a large number of photon flight events, and a histogram is formed by counting a large number of photon flight times, and the distance of the object to be measured is determined by searching a peak value in the histogram or calculating the centroid position.

In the ToF ranging method, the photosensitive cells are typically arrays of single photon avalanche diodes (Single Photon Avalanche Diode, SPADs). However, for objects with high reflectivity and close distance, the return light intensity is too high, so that most of SPADs in the SPAD array are easily saturated quickly and enter dead time, photons arriving subsequently cannot be sensed, a detection peak appears in advance, and a ranging result is deviated.

Disclosure of Invention

In view of this, embodiments of the present disclosure provide a ToF ranging method, ranging apparatus, and storage medium.

In order to achieve the above purpose, the technical scheme of the present disclosure is realized as follows:

in a first aspect, an embodiment of the present disclosure provides a ToF ranging method, the method including:

determining response parameters of the SPAD array to the light pulse reflected by the target to be detected when the light pulse reflected by the target to be detected is responded at least once; the response parameter is related to the intensity of the detected light pulse;

comparing the response parameter with a preset parameter range to judge whether to adjust the opening quantity of the SPAD pixels in the SPAD array;

when the response parameter does not fall into the preset parameter range, adjusting the opening number of the SPAD pixels in the SPAD array;

And when the response parameter falls into a preset parameter range, not adjusting the opening quantity of the SPAD pixels in the SPAD array.

In some embodiments, when the response parameter does not fall within the preset parameter range, adjusting the number of SPAD pixels in the SPAD array includes:

when the response parameter is greater than or equal to a first threshold, reducing the opening number of SPAD pixels in the SPAD array, wherein the first threshold is the maximum value in the preset parameter range;

and when the response parameter is smaller than a second threshold, increasing the opening number of the SPAD pixels in the SPAD array, wherein the second threshold is the minimum value in the preset parameter range.

In some embodiments, the determining a response parameter of the SPAD array to the light pulse reflected by the object to be measured includes:

acquiring an electric signal output by the SPAD array in response to an optical pulse, wherein the electric signal is a voltage signal or a current signal;

and determining response parameters of the SPAD array to the light pulse reflected by the target to be measured according to the electric signals.

In some embodiments, determining a response parameter of the SPAD array to an optical pulse reflected by a target to be measured from the electrical signal includes:

Acquiring the number of voltage signals output by the SPAD array when responding to one light pulse, and determining response parameters according to the number of the voltage signals;

or, acquiring the amplitude of a current signal output by the SPAD array in response to one light pulse, and determining a response parameter according to the amplitude of the current signal.

In some embodiments, the obtaining the number of voltage signals output by the SPAD array in response to one light pulse includes:

determining a target SPAD pixel which outputs a voltage signal in an SPAD array, and acquiring pixel point distribution information of the target SPAD pixel in the SPAD array;

according to the pixel point distribution information, the basic quantity of all the target SPAD pixels and the quantity of pixel groups formed by at least two adjacent target SPAD pixels are counted;

acquiring basic weights corresponding to all the target SPAD pixels and pixel group weights corresponding to the pixel groups, wherein the pixel group weights are larger than the basic weights;

and determining the number of voltage signals output by the SPAD array in response to one light pulse according to the basic number and the basic weight as well as the pixel group number and the pixel group weight.

In some embodiments, the pixel group formed by at least two adjacent target SPAD pixels includes at least a first pixel group and a second pixel group, the number of the target SPAD pixels in the second pixel group is greater than the number of the target SPAD pixels in the first pixel group;

the pixel group weight at least comprises a first sub weight corresponding to the first pixel group and a second sub weight corresponding to the second pixel group, and the second sub weight is larger than the first sub weight.

determining a target SPAD pixel which outputs a voltage signal in the SPAD array, and acquiring pixel point distribution information of the target SPAD pixel in the SPAD array;

according to the pixel point distribution information, counting the number of the target SPAD pixels in different position areas in the SPAD array, wherein the distances between the different position areas and the center of the SPAD array are different;

acquiring position weights corresponding to different position areas, wherein the position weights corresponding to the position areas with larger space between centers of the SPAD array are larger;

And determining the number of voltage signals output by the SPAD array when responding to one light pulse according to the number of the target SPAD pixels in different position areas in the SPAD array and the position weights corresponding to the different position areas.

In some embodiments, determining a response parameter of the SPAD array to the light pulse reflected by the object to be measured when the at least one response light pulse comprises:

when the SPAD array responds to the light pulse reflected by the target to be detected for the first time, determining response parameters of the SPAD array to the light pulse reflected by the target to be detected;

or, according to the preset frequency, periodically determining the response parameter of the SPAD array to the light pulse reflected by the target to be detected;

or determining the response parameter of the SPAD array to the light pulse reflected by the object to be measured every time the SPAD array responds to the light pulse.

In a second aspect, embodiments of the present disclosure provide a ToF ranging apparatus, the apparatus comprising:

the combination logic processor is used for acquiring response parameters of the SPAD array to the light pulse reflected by the target to be detected; the response parameter is related to the intensity of the detected light pulse;

the comparator is used for comparing the response parameter with a preset parameter range and judging whether the response parameter falls into the preset parameter range or not;

The gating controller judges whether to adjust the opening quantity of the SPAD pixels in the SPAD array according to the relation between the response parameter and the preset parameter range; when the response parameter does not fall into the preset parameter range, the opening number of the SPAD pixels in the SPAD array is adjusted; and when the response parameter falls into a preset parameter range, not adjusting the opening quantity of the SPAD pixels in the SPAD array.

In a third aspect, embodiments of the present disclosure provide a computer readable storage medium, on which a computer program is stored, wherein the computer program, when executed by a processor, implements the method described in the above technical solution.

The embodiment of the disclosure provides a ToF ranging method, ranging equipment and a storage medium. The method comprises the following steps: determining response parameters of the SPAD array to the light pulse reflected by the target to be detected when the light pulse reflected by the target to be detected is responded at least once; the response parameter is related to the intensity of the detected light pulse; comparing the response parameter with a preset parameter range to judge whether to adjust the opening quantity of the SPAD pixels in the SPAD array; when the response parameter does not fall into the preset parameter range, adjusting the opening number of the SPAD pixels in the SPAD array; and when the response parameter falls into a preset parameter range, not adjusting the opening quantity of the SPAD pixels in the SPAD array. According to the embodiment of the disclosure, the opening quantity of the SPAD in the SPAD array can be dynamically adjusted according to the response parameters of the SPAD array to the light pulses, so that the detection sensitivity of the SPAD array can be flexibly adapted to the light pulses with different light intensities, and the problem that the reliability of the ranging data is reduced due to the fact that the SPAD array is saturated in signals or the detection sensitivity is too low is prevented, so that the accuracy of an optical detection link is improved.

Drawings

FIG. 1 is a diagram of a probe response curve and an ideal probe response curve for SPAD in an example;

fig. 2 is a flowchart of a ToF ranging method provided by an embodiment of the present disclosure;

fig. 3 is an exemplary diagram of a first ToF device provided by an embodiment of the present disclosure;

fig. 4 is an exemplary diagram of a second ToF device provided by an embodiment of the present disclosure;

fig. 5 is an exemplary diagram of a third ToF device provided by an embodiment of the present disclosure;

fig. 6 is a schematic view of a SPAD array in a third ToF device according to an embodiment of the present disclosure;

fig. 7 is an exemplary diagram of a fourth ToF device provided by an embodiment of the present disclosure;

fig. 8 is an operation logic diagram of a ToF ranging method according to an embodiment of the present disclosure;

fig. 9 is a block diagram of a ToF ranging apparatus provided by an embodiment of the present disclosure.

Detailed Description

The following description of the embodiments of the present disclosure will be made clearly and fully with reference to the embodiments of the present disclosure and the accompanying drawings, it being apparent that the described embodiments are only some, but not all, of the embodiments of the present disclosure. All other embodiments, which can be made by one of ordinary skill in the art without inventive effort, based on the embodiments in this disclosure are intended to be within the scope of this disclosure.

In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present disclosure. However, it will be apparent to one skilled in the art that the present disclosure may be practiced without one or more of these details. In other instances, well-known features have not been described in order to avoid obscuring the present disclosure; that is, not all features of an actual implementation are described in detail herein, and well-known functions and constructions are not described in detail.

In the drawings, the size of layers, regions, elements and their relative sizes may be exaggerated for clarity. Like numbers refer to like elements throughout.

It will be understood that when an element or layer is referred to as being "on" … …, "" adjacent to "… …," "connected to" or "coupled to" another element or layer, it can be directly on, adjacent to, connected to or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on" … …, "" directly adjacent to "… …," "directly connected to" or "directly coupled to" another element or layer, there are no intervening elements or layers present. It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present disclosure. When a second element, component, region, layer or section is discussed, it does not necessarily mean that the first element, component, region, layer or section is present in the present disclosure.

Spatially relative terms, such as "under … …," "under … …," "below," "under … …," "above … …," "above," and the like, may be used herein for ease of description to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use and operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements or features described as "under" or "beneath" other elements would then be oriented "on" the other elements or features. Thus, the exemplary terms "under … …" and "under … …" may include both an upper and a lower orientation. The device may be otherwise oriented (rotated 90 degrees or other orientations) and the spatially relative descriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term "and/or" includes any and all combinations of the associated listed items.

For a thorough understanding of the present disclosure, detailed steps and detailed structures will be presented in the following description in order to illustrate the technical aspects of the present disclosure. Preferred embodiments of the present disclosure are described in detail below, however, the present disclosure may have other implementations in addition to these detailed descriptions.

The photon time-of-flight method is a ranging method, and the basic principle of ToF is to calculate the distance of a measured object by continuously transmitting light pulses (typically invisible light) onto the measured object, then receiving light pulses reflected back from the measured object, and by detecting the flight (round trip) time of the light pulses. ToF has been widely used because of its simple principle, miniaturized equipment, large measurement distance range, and strong anti-interference ability.

ToF ranging typically uses a single photon avalanche diode array as the photosensitive element, and a SPAD array typically includes a plurality of SPAD pixels, where SPAD is a photodiode operating at a large reverse bias voltage, and is a special PN junction. During normal operation, reverse bias voltage greater than avalanche breakdown is applied across the PN junction. Since the PN junction is reverse biased, no carrier is present in the depletion region in the critical state, and no current flows. But when photons enter the PN junction depletion region, they are converted into photogenerated carriers. The photo-generated carriers continuously impact and excite other carriers in the PN junction under the action of an electric field formed by large bias voltage to generate large current, and the whole process is similar to avalanche, so that the photo-generated carriers are called single photon avalanche diodes.

However, SPADs have dead time after responding to photons, during which SPADs are "saturated" and no more photons can be detected. From the circuit structure, each SPAD corresponds to a quenching circuit, and in the dead time, the quenching circuit can reduce the voltage at two ends of the SPAD, so that the electric field of an avalanche region is rapidly reduced, and the avalanche process is terminated. Thus, if the arrival time of the next photon reflected back is within the dead time of a SPAD, the next photon cannot be responded to by the SPAD.

For targets with the same distance and different reflectivities or targets with different distances and the same reflectivities, the same light pulse is emitted, the light intensities reflected by the targets after light attenuation and reflection are different, wherein the light intensities of the light pulses reflected by the targets with high reflectivity and the targets with short distance are larger. When the light intensity of the reflected light pulse is too large, most of the SPAD pixels in the SPAD array quickly reach a detection saturation state, namely enter dead time, so that the subsequently arriving photons cannot be responded, and a detection peak appears in advance.

Referring to fig. 1, fig. 1 is a probe response curve and an ideal probe response curve of SPAD in an example.

As shown in fig. 1, a response curve 100 represents a distribution curve of the number of photons in a reflected light pulse of a SPAD array response over time under ideal conditions, and a photon flight time reflecting a target distance to be measured can be determined according to a duration between an emission time of the light pulse and a time 102 when a peak of the response curve 100 is detected. When the object to be measured is close to the ranging apparatus or the object to be measured has a high reflectivity (e.g., a mirror), the peak value of the detection response curve of the SPAD may be advanced, which is reflected as a distorted response curve 104 in fig. 1, and the time 108 of the peak value corresponding to the distorted response curve 104 is advanced by a period of time 106 with respect to the time 102 of the peak value corresponding to the ideal response curve 100, thereby causing a measurement error. In addition, the situation that the detected distance values are different although the distances between two targets with different reflectivities are the same can also occur in the measurement; it may also occur that the actual distances between two objects having the same reflectivity are different, but the detected distance values are the same, thereby causing measurement errors.

Therefore, how to solve the problem of inaccuracy of the detection result caused by deviation of the response curve of the SPAD array is a general concern in the industry.

Referring to fig. 2, fig. 2 is a flowchart of a ToF ranging method provided in an embodiment of the present disclosure.

As shown in fig. 2, an embodiment of the present disclosure provides a ToF ranging method, including:

step S201: determining response parameters of the SPAD array to the light pulse reflected by the target to be detected when the light pulse reflected by the target to be detected is responded at least once; the response parameter is related to the intensity of the detected light pulse;

step S202: comparing the response parameter with a preset parameter range to judge whether to adjust the opening quantity of the SPAD pixels in the SPAD array; when the response parameters do not fall into the preset parameter range, the opening number of the SPAD pixels in the SPAD array is adjusted; when the response parameters fall into the preset parameter range, the opening number of the SPAD pixels in the SPAD array is not adjusted.

In the embodiment of the present disclosure, the light pulse may be emitted through an optical emission system, wherein the light source may be a light Emitting Diode (Light Emitting Diode, LED), a Laser Diode (LD), an edge-Emitting Laser (Edge Emitting Laser, EEL), a Vertical-Cavity Surface-Emitting Laser (VCSEL), or the like, which emits the light pulse outwards under the driving control of the driver; the light pulses may be laser light, infrared light, ultraviolet light, etc., which are not limited by the disclosed embodiments.

Embodiments of the present disclosure may detect photons through an optical receiving system, wherein the optical receiving system includes a detection end and an optical element or the like that directs light propagation, such as one or more combinations of forms of lenses, microlens arrays, mirrors, etc., through which an optical signal is directed onto the detection end. The detection end may be a SPAD array made up of a plurality of SPAD pixels. In addition, the detection end can also comprise photoelectric conversion devices such as an avalanche photodiode, a photomultiplier tube, a silicon photomultiplier tube and the like.

The optical transmitting system in the embodiment of the disclosure can transmit laser pulses for a plurality of times, and after transmitting the light pulses, the SPAD array responds to the plurality of light pulses reflected by the target to be measured, and can determine the response parameters of the SPAD array to the light pulses reflected by the target to be measured at least once. For example, the SPAD array may determine the response parameters N times in response to N pulses of light reflected back from the object to be measured, N being a positive integer.

In the embodiment of the disclosure, the response parameters of the SPAD array to light at a certain moment are utilized to judge the light intensity, and then the number of SPAD pixels opened in the SPAD array is adaptively and dynamically adjusted according to the judgment result of the light intensity, so that the SPAD array can be flexibly adapted to light pulses with different light intensities, thereby preventing the SPAD array from signal saturation and improving the accuracy of an optical detection link.

In the embodiment of the disclosure, when the SPAD array detects a photon of a reflected light pulse, a response parameter of the SPAD array to the light pulse reflected by the object to be measured can be obtained. If the response parameter of the SPAD array is greater than or equal to the first threshold, the SPAD array has higher detection sensitivity to the current intensity light pulse, the probability that the SPAD pixels in the SPAD array receive photons is higher, and the probability that most SPAD pixels in the SPAD array reach a saturated state quickly is higher, and most SPAD pixels in saturation cannot detect other subsequently arriving photons. Therefore, some SPAD pixels need to be turned off to reduce the detection sensitivity of the SPAD array to match the intensity of the light pulses. When the next light pulse reflected back by the object to be measured arrives, the probability of photon reception by the SPAD pixels in the SPAD array is relatively reduced, so that the detection time of the next photon is outside the dead time of SPAD, and is detected by the SPAD pixels.

In the embodiment of the disclosure, the problem that targets cannot be effectively detected due to signal saturation in a strong light environment can be solved by adjusting the opening quantity of the SPADs in the SPAD array; the detection efficiency of the target to be detected is low in the low-light environment.

It should be noted that the number of SPADs included in the SPAD array may be specifically selected according to practical situations, and the embodiments of the present disclosure are not specifically limited.

In the embodiment of the disclosure, the ToF ranging method may be implemented by a ToF ranging apparatus, where the ToF ranging apparatus includes a photon response module, a control module, a time information module, and a data processing module. The photon response module may be a SPAD array, and the control module may include a combinational logic processor, a comparator, and a gating controller coupled in sequence.

In the embodiment of the disclosure, the photon response module (taking a SPAD array as an example) is used for sensing the reflected light pulse and outputting a corresponding electric signal according to the condition that each SPAD pixel responds to the photon. The control module is used for judging the light intensity of the reflected light pulse according to the electric signal output by the photon response module and combining with a preset parameter range, and then adjusting the opening quantity of the SPAD pixels of the SPAD array. The time information module is used for acquiring photon flight time. The data processing module is used for determining the distance of the object to be detected according to the time of detecting the light pulse and the time of emitting the light pulse.

Referring to fig. 3, fig. 3 is an exemplary diagram of a first ToF device provided by an embodiment of the present disclosure.

In an embodiment of the disclosure, determining a response parameter of the SPAD array to a light pulse reflected by a target to be measured includes:

acquiring an electric signal output by the SPAD array when responding to an optical pulse, wherein the electric signal is a voltage signal or a current signal;

Referring to fig. 3, in the present embodiment, the output end of each SPAD pixel of the SPAD array is coupled to the input end of the combinational logic processor 300, and the combinational logic processor 300 can obtain the response parameter M of the SPAD array to the light pulse reflected by the object to be measured according to the input electrical signal.

In the embodiment of the disclosure, the SPAD array is formed by a plurality of SPAD pixels, and the SPAD pixels in the ToF ranging apparatus provided by the disclosure can output an electrical signal, and the electrical signal can be a voltage signal or a current signal.

As shown in fig. 3, the output of the SPAD array may be coupled to an input of a combinational logic processor 300. Taking the example of obtaining response parameters according to the output voltage signals of the SPAD array, when the SPAD array detects the reflected light pulse, each turned-on SPAD pixel in the SPAD array outputs high-level voltage or low-level voltage to the combinational logic processor, and the combinational logic processor 300 processes each input voltage signal to obtain the response parameters M of the SPAD array to the light pulse reflected by the object to be tested. Here, the SPAD pixels turned on in the SPAD array output a high level voltage after detecting photons of the light pulse, and the SPAD pixels turned on in the SPAD array output a low level voltage when not detecting photons of the light pulse.

In an embodiment of the disclosure, determining, according to an electrical signal, a response parameter of a SPAD array to an optical pulse reflected by a target to be measured includes:

the method comprises the steps of obtaining the number of voltage signals output by the SPAD array in response to one light pulse, and determining response parameters according to the number of the voltage signals.

With continued reference to fig. 3, in an embodiment of the present disclosure, when a certain on SPAD pixel in the SPAD array senses a photon, the SPAD outputs a high level voltage, which may be noted as parameter 1. When a certain turned-on SPAD in the SPAD array does not sense a photon, the SPAD outputs a low level voltage (the voltage value of the low level voltage may be 0), which may be denoted as parameter 0. The combinational logic processor counts the number of input parameter 1 (i.e., the number of input high level voltages) to obtain the response parameter M.

In another embodiment of the present disclosure, a counter circuit, which may be a counter, is coupled to the output of each SPAD. The signal input end of the counter can be arranged between the signal output end of the SPAD and the quenching circuit, the counter is directly connected with the SPAD to directly collect the number of pulse signals generated on the SPAD, and the quenching circuit is prevented from affecting the signal collection of the counter. When a certain open SPAD pixel in the SPAD array senses photons, the SPAD pixel outputs high-level voltage, the high-level voltage is counted once by a corresponding counter, a counting parameter '1' is output, and the counter outputs the counting parameter to a combinational logic processor. When a SPAD on a SPAD array does not sense a photon, the SPAD pixel is not counted by the corresponding counter. The combination logic processor counts the input counting parameters to obtain a response parameter M, in other words, the combination logic processor counts the counter which performs the counting operation to obtain the response parameter M. In some alternative embodiments, the number of counters in the counter array is the same as the number of SPAD pixels in the SPAD array; and, there is a unique correspondence of one-to-one with SPAD pixels. This allows for more accurate and efficient counting of each SPAD pixel.

In an embodiment of the disclosure, obtaining the number of voltage signals output by the SPAD array in response to one light pulse includes:

determining a target SPAD pixel in the SPAD array, which outputs a voltage signal, and acquiring pixel point distribution information of the target SPAD pixel in the SPAD array;

according to the pixel point distribution information, the basic quantity of all target SPAD pixels and the quantity of pixel groups formed by at least two adjacent target SPAD pixels are counted;

acquiring basic weights corresponding to all target SPAD pixels and pixel group weights corresponding to pixel groups, wherein the pixel group weights are larger than the basic weights;

In the embodiment of the disclosure, when the turned-on SPAD pixels in the SPAD array sense the reflected light pulses, the SPAD array converts the reflected light pulses into electrical signals, and each turned-on SPAD pixel emits an electrical signal after receiving photons. Here, the electric signal is a voltage signal or a current signal. The electrical signal is taken as a voltage signal for illustration: the combinational logic processor may determine, based on the received voltage signals, a position distribution of SPAD pixels in the SPAD array that are on and that sense photons, where the SPAD pixels that sense photons may be referred to as target SPAD pixels. And the combination logic processor counts the number of all target SPAD pixels in the SPAD array to obtain the basic number. In addition, the situation that at least two target SPAD pixels in the SPAD array are adjacent is counted, and the at least two adjacent target SPAD pixels can form a pixel group. It should be noted that, in the embodiments of the present disclosure, the two target SPAD pixels are adjacent to each other in a horizontal or vertical direction, rather than diagonally. The combination logic processor counts the number of the pixel groups to obtain the number of the pixel groups, then respectively carries out weighted summation calculation on the base number and the number of the pixel groups by using the base weight and the weight of the pixel groups, so that the number of voltage signals output by the SPAD array when responding to one light pulse can be obtained, and then the response parameter M is determined according to the number of the voltage signals output by the SPAD array.

In this embodiment, the pixel group weight of the number of pixel groups may be greater than the base weight of the base number, because the detection of photons by adjacent pixel points in the pixel group indicates that the return light intensity is greater than by detecting photons by a single pixel point, and therefore, when calculating its contribution to the number of voltage signals output by the SPAD array, a higher weight should be matched.

In the embodiment of the disclosure, a pixel group formed by at least two adjacent target SPAD pixels at least comprises a first pixel group and a second pixel group, and the number of the target SPAD pixels in the second pixel group is larger than that of the target SPAD pixels in the first pixel group;

Referring to fig. 4, fig. 4 is an exemplary diagram of a second type of ToF device provided by embodiments of the present disclosure.

In a specific example, the first pixel group may include two adjacent target SPAD pixels and the second pixel group may include three adjacent target SPAD pixels. Illustratively, as shown in FIG. 4, the SPAD array is a 4 x 4 array comprising 16 SPAD pixels, wherein the SPAD pixel numbered 1 is a target SPAD pixel. Two adjacent SPAD pixels numbered 6 and 7 are target SPAD pixels, and two adjacent target SPAD pixels numbered 6 and 7 may form a first pixel group. The three adjacent SPAD pixels numbered 10, 11, and 15 are all target SPAD pixels, and the three adjacent target SPAD pixels numbered 10, 11, and 15 may form a second pixel group. The combinational logic processor 400 respectively counts the target SPAD pixels, the first pixel group and the second pixel group to obtain a base number, a first pixel group number and a second pixel group number. The base number is denoted as X, the first pixel group number is denoted as Y, and the second pixel group number is denoted as Z. The combination logic processor 400 performs a weighted calculation on the resulting base number, the first pixel group number, and the second pixel group number. The weights corresponding to the basic number, the first pixel group number and the second pixel group number are respectively a basic weight i, a first sub weight j and a second sub weight k. Note that the first pixel group and the second pixel group do not repeat counting, in other words, there is no overlap of the target SPAD pixels between the first pixel group and the second pixel group. The calculation formula of the number S of the voltage signals output by the SPAD array is as follows:

S＝X*i+Y*j+Z*k

In the disclosed embodiment, i, j, and k are weight parameters related to the number of target SPAD pixels contained in a SPAD pixel or group of pixels. The weight of the target SPAD pixels counted independently, namely the basic weight, is minimum, the more the number of adjacent target SPAD pixels contained in the pixel group is, the larger the weight of the pixel group is, namely i < j < k, i, j and k can be increased in equal proportion. Illustratively, the ratio between i, j and k may be 1:2:4. it should be noted that, the more adjacent target SPAD pixels in the pixel group where photons are detected, the greater the light intensity is also indicated, and therefore, the greater the number of adjacent target SPAD pixels in the pixel group is, the greater the weight thereof is.

In this embodiment, the number S of voltage signals output by the SPAD array and the response parameter M of the SPAD array are in positive correlation, and the larger the S value, the larger M is; conversely, the smaller the S value, the smaller M. The ToF ranging apparatus may determine the response parameter M corresponding to the S value according to the S value in combination with its own optical structure and parameter index.

In another embodiment, obtaining the number of voltage signals output by the SPAD array in response to one light pulse includes:

According to the pixel point distribution information, counting the number of target SPAD pixels in different position areas in the SPAD array, wherein the distances between the different position areas and the center of the SPAD array are different;

acquiring position weights corresponding to different position areas, wherein the position weight corresponding to the position area with the larger space between the centers of the SPAD arrays is larger;

and determining the number of voltage signals output by the SPAD array when responding to one light pulse according to the number of target SPAD pixels in different position areas in the SPAD array and the position weights corresponding to the different position areas.

Referring to fig. 5 and 6, fig. 5 is an exemplary diagram of a third ToF device provided by an embodiment of the present disclosure. Fig. 6 is a schematic view of SPAD arrays in a third ToF device according to an embodiment of the present disclosure.

As shown in fig. 6, the SPAD array is an exemplary 4 x 4 array comprising 16 SPAD pixels, including three location areas in the SPAD array along the center outward direction, a first area (including SPAD pixels numbered 6, 7, 10, and 11), a second area (including SPAD pixels numbered 2, 3, 5, 8, 9, 12, 14, and 15), and a third area (including SPAD pixels numbered 1, 4, 13, and 16) in sequence. When the SPAD array senses an optical pulse, the partially turned-on SPAD pixels in the SPAD array respond to photons and output a voltage signal. Here, the SPAD pixel responsive to the photon is a target SPAD pixel, for example, the SPAD pixel numbered 1 may be a target SPAD pixel, the target SPAD pixel being located in the third area; the SPAD pixel numbered 6 may be a target SPAD pixel, the target SPAD pixel being located in the first zone; the SPAD pixel numbered 12 may be a target SPAD pixel, the SPAD pixel being located in the second region. The combinational logic processor can determine the position distribution condition of the target SPAD pixels in the SPAD array according to the received voltage signals. The combinational logic processor 500 counts the voltage signals (i.e., high level voltages) generated by the target SPAD pixels of each region in the SPAD array, to obtain the number of voltage signals corresponding to each region, i.e., the first region parameter a, the second region parameter B, and the third region parameter C, respectively. The combinational logic processor 500 performs weighted summation calculation on the obtained first area parameter a, second area parameter B and third area parameter C to obtain the number S of voltage signals output by the SPAD array. The position weights corresponding to the first region, the second region and the third region are m, n and q respectively. The calculation formula of the number S of the voltage signals output by the SPAD array is as follows:

S＝A*m+B*n+C*q

In the embodiment of the disclosure, m, n and q are position weights related to positions in the SPAD array, and the further the target SPAD pixel is from the SPAD array center, the larger the weight is, i.e., m < n < q, where m, n and q may be equal difference increased, and the ratio of m, n and q may be 1:2:3. for the reflected light pulse, the probability that the SPAD pixel positioned at the center position of the SPAD array senses a photon is larger, and the probability that the SPAD pixel positioned at the edge position of the SPAD array senses a photon is smaller, so that if the SPAD pixel positioned at the edge position senses a photon, namely, a target SPAD pixel positioned at the edge position exists, the light intensity can be larger, and when the light intensity judgment is carried out, the target SPAD pixel positioned at the edge position needs to be multiplied by a larger weight parameter, so that the condition that the environment light intensity is larger can be judged more accurately.

In the embodiment of the disclosure, the electrical signals output by the SPAD array counted by the combinational logic processor are obtained by weighting and accumulating the electrical signals output by each SPAD pixel, wherein the combinational logic processor can weight and sum the electrical signals output by each target SPAD pixel one by one to obtain the number S of voltage signals, and obtain the response parameter M according to the number S of voltage signals. The combinational logic processor can also classify and count target SPAD pixels first, then weight and sum the electric signals output by SPAD pixels of each class to obtain the number of voltage signals S, and obtain the response parameter M according to the number of voltage signals S.

It can be understood that in the embodiment of the present disclosure, the value intervals of m, n and q are different for different SPAD array sizes (including array areas and pixel numbers), and also correspond to different preset parameter ranges.

and acquiring the amplitude of a current signal output by the SPAD array when responding to one light pulse, and determining a response parameter according to the amplitude of the current signal.

Referring to fig. 7, fig. 7 is an exemplary diagram of a fourth ToF device provided by embodiments of the present disclosure. As shown in fig. 7, when the SPAD array senses the reflected light pulse and outputs a current signal to the combinational logic processor 700, that is, each turned-on SPAD pixel outputs a current signal to the combinational logic processor 700, the current signal output by the SPAD pixel may be a high current or a low current (the current value of the low current may be 0). The combinational logic processor 700 superimposes the input current signals to obtain an output total current signal I of the SPAD array, and determines a response parameter M of the SPAD array to the light pulse reflected by the object to be measured according to the output total current signal I. Similar to the relation between the number S of the voltage signals output by the SPAD array and the response parameter M, the total current signal I output by the SPAD array and the response parameter M of the SPAD array are in positive correlation, and the larger the I value is, the larger M is; conversely, the smaller the I value, the smaller M. The ToF ranging apparatus may determine the response parameter M corresponding to the I value according to the I value in combination with its own optical structure and parameter index. Specifically, the combinational logic processor 700 performs analog sampling on the combined current signal, and obtains a response parameter M according to the amplitude of the current signal I obtained by sampling, where the response parameter M reflects the number of SPAD pixels in the SPAD array, i.e. the number of target SPAD pixels.

In the embodiment of the present disclosure, when the response parameter does not fall within the preset parameter range, adjusting the number of SPAD pixels in the SPAD array includes:

when the response parameter is greater than or equal to a first threshold, reducing the opening number of the SPAD pixels in the SPAD array, wherein the first threshold is the maximum value in a preset parameter range;

Referring to fig. 8, fig. 8 is a logic diagram illustrating an operation of a ToF ranging method according to an embodiment of the present disclosure. As shown in fig. 8, a light pulse is emitted to a target to be measured, a response parameter of the SPAD array to the light pulse reflected by the target to be measured is obtained, the response parameter is compared with a first threshold value and a second threshold value of a preset parameter range, the light intensity of the reflected light pulse is judged, and the number of SPAD pixels in the SPAD array is adjusted according to the judgment of the light intensity. If the response parameter falls within the preset parameter range, judging that the light intensity of the reflected light pulse is proper, keeping the number of the currently opened SPAD pixels unchanged, and if the response parameter does not fall within the preset parameter range, judging whether the light intensity of the reflected light pulse is bigger or smaller according to the specific value of the response parameter, and correspondingly reducing or increasing the opening number of the SPAD.

Referring to fig. 3 to 7, after the response parameter M is acquired, the response parameter M is compared with a preset parameter range by using a comparator 301, and the number of SPAD pixels turned on in the SPAD array is adjusted according to the comparison result. The preset parameter range comprises a first threshold and a second threshold, wherein the first threshold is larger than the second threshold, the first threshold is the maximum value in the preset parameter range, and the second threshold is the minimum value in the preset parameter range. Specifically, the second threshold is equal to a and the first threshold is equal to b. When a.ltoreq.M < b, the gating controller 302 does not adjust the on-number of SPAD pixels of the SPAD array. When M is greater than or equal to b, the reflected light pulse is judged to be strong light, and the gating controller 302 reduces the opening number of SPAD pixels in the SPAD array. When M is less than a, the reflected light pulse is judged to be weak light, and the gating controller increases the opening quantity of the SPAD pixels in the SPAD array. In the embodiment of the disclosure, a may be 1, and b may be 2. In the disclosed embodiment, the output of the gating controller 302 is coupled to each SPAD pixel in the SPAD array to gate each SPAD separately, thereby controlling the number of SPAD pixels in the SPAD array to turn on.

In some embodiments, the number and positions of SPAD pixels that are turned off or on may be inversely set according to the weights occupied by various SPAD pixels in the technical solutions shown in fig. 4 or fig. 5. For example, when M is greater than or equal to b, the reflected light pulse is determined to be strong light, and more target SPAD pixels in the pixel group with larger weight or more target SPAD pixels in the region with smaller position weight (for example, the first region) or less target SPAD pixels in the region with larger position weight (for example, the third region) can be turned off preferentially. When M < a, the reflected light pulse is judged to be weak light, and more SPAD pixels in the area with smaller position weight (for example, the first area) or fewer SPAD pixels in the area with larger position weight (for example, the third area) can be preferentially turned on.

Illustratively, when M is greater than or equal to b, the reflected light pulse is determined to be strong, the gating controller may randomly turn off some SPAD pixels in the SPAD array, or the gating controller may preferentially turn off some SPAD pixels in the SPAD array near the center region. When M is less than a, the reflected light pulse is judged to be weak light, the gating controller can randomly start the partial SPAD pixels which are turned off in the SPAD array, or the gating controller can preferentially start the partial SPAD pixels which are close to the central area in the SPAD array.

In the embodiment of the disclosure, the gate controller may control the magnitude of the applied reverse bias voltage corresponding to each SPAD pixel, or control the opening and closing of the circuit switch corresponding to each SPAD pixel, so as to control the opening or closing of the SPAD pixel.

In the embodiment of the disclosure, the preset parameter range may be a preset parameter threshold, or may be determined by ambient light information where the SPAD array is located.

The ToF ranging method of the present disclosure has a number of beneficial effects, in a first aspect, reducing detection errors for high reflectivity targets or near targets. After the laser is emitted once, the SPAD responds to the reflected light pulse, the response parameter of the SPAD array is calculated, whether the reflected light reflected by the target is strong light or weak light is judged, if the reflected light is strong light, the reflectivity of the target is judged to be higher or the distance is closer, and the opening number of SPAD pixels of the SPAD array is reduced to reduce the sensitivity of the SPAD array.

According to the embodiment of the disclosure, the intensity of the reflected light pulse can be judged through the response parameters of the SPAD array, and the number of the open SPAD pixels in the SPAD array is adaptively adjusted, so that the detection sensitivity of the SPAD array is matched with the intensity of the reflected light pulse, the possibility that most of the SPAD pixels in the SPAD array reach a saturated state is reduced, the target light pulse in the later stage of exposure can be continuously detected, the time box where the detected target peak is located is more similar to the time box where the real ideal target peak is located, and the detection accuracy of a high-reflectivity target or a close target is improved.

In a second aspect, interference of strong ambient light is reduced. Under the condition that laser is not emitted, the light intensity of the environmental light can be judged by comparing the response parameter of the SPAD array with the first threshold and the second threshold of the preset parameter range, if the response parameter is higher, the opening number of SPAD pixels in the SPAD array can be reduced to reduce the sensitivity of the SPAD array, if the response parameter is lower, the opening number of SPAD pixels in the SPAD array can be increased to improve the sensitivity of the SPAD array, and the opening number of the SPAD pixels of the SPAD array can be dynamically adjusted, so that the SPAD array is flexibly adapted to different environmental light information and the signal to noise ratio is improved.

In the disclosed embodiments, acquiring photon flight times requires acquiring the time of the emitted light pulse. In some embodiments, the time at which the light pulse is emitted comprises: one of a generation time of the control signal, a reception time of the control signal, or an actual emission time of the light pulse; wherein the control signal is a signal for controlling the emission of the light pulse. The generation time of the control signal may be, for example, the time at which the control signal is generated by a signal processing system including electronic components such as a CPU, an MCU, or the like. The time of receiving the control signal may be the time when the optical transmission system receives the control signal, or the time when a timer (e.g., TDC) receives the control signal, where the optical transmission system is configured to transmit the optical pulse according to the received control signal, and the timer is configured to start timing according to the received control signal. In addition, the time of emitting the light pulse may be determined based on other manners, such as an actual emission time of the light pulse determined after compensating the generation time of the control signal based on a preset time compensation parameter, or an actual emission time of the light pulse determined after fitting the time of receiving the control signal by the optical emission system based on a preset fitting function, etc.

In the embodiment of the disclosure, after determining the time of detecting the light pulse and the time of emitting the light pulse, the position of the target to be measured is determined by using a photon time-of-flight ranging principle.

In an embodiment of the present disclosure, determining a response parameter of a SPAD array to an optical pulse reflected by a target to be measured when responding to the optical pulse at least once includes:

alternatively, each time the SPAD array responds to an optical pulse, the SPAD array's response parameters to the optical pulse reflected by the object to be measured are determined.

In the embodiment of the disclosure, at least one light pulse can be emitted to the target to be measured, so as to make at least one adjustment on the opening number of SPAD pixels in the SPAD array. That is, the number of SPAD pixels in the SPAD array may be adjusted only once after the first sensing of the reflected light pulse or multiple times. If the adjustment is performed for multiple times, the response parameter of the SPAD array to the light pulse reflected by the object to be measured can be periodically determined according to the preset frequency, so that the opening number of SPAD pixels of the SPAD array is periodically adjusted. And the response parameters of the SPAD array to the light pulse reflected by the object to be measured can be determined when the SPAD array responds to the light pulse each time, so that the opening number of the SPAD pixels in the SPAD array is adjusted for each light pulse.

In the embodiment of the disclosure, the step of adjusting the number of SPAD pixels turned on of the SPAD array by determining the light intensity may be performed in a SPAD test phase or in a ranging phase after the SPAD test phase. Wherein the number of SPAD pixels in the SPAD array can be adjusted only once after the first sensing of the reflected light pulse. The number of the SPAD pixels started in the SPAD array can be adjusted after the light pulse is received each time, or the number of the SPAD pixels started in the SPAD array can be periodically adjusted, namely, the judgment logic is periodically started after the light pulse is received for a plurality of times, so that the stability of the system is improved.

The embodiment of the disclosure further provides a ToF ranging apparatus, and fig. 9 is a block diagram of the ToF ranging apparatus provided by the embodiment of the disclosure. As shown in fig. 9, the apparatus includes:

a combinational logic processor 901, which obtains response parameters of the SPAD array to the light pulse reflected by the object to be measured; correlating the light intensities of the light pulses detected in response to the parameters;

the comparator 902 compares the response parameter with a preset parameter range and judges whether the response parameter falls within the preset parameter range;

The gating controller 903 determines whether to adjust the number of SPAD pixels in the SPAD array according to the relationship between the response parameter and the preset parameter range; when the response parameters do not fall into the preset parameter range, the opening number of the SPAD pixels in the SPAD array is adjusted; when the response parameters fall into the preset parameter range, the opening number of the SPAD pixels in the SPAD array is not adjusted.

In the disclosed embodiment, the gating controller 903 is also used to:

In the disclosed embodiment, the combinational logic processor 901 is also used to:

or, acquiring the amplitude of the current signal output by the SPAD array in response to one light pulse, and determining the response parameter according to the amplitude of the current signal.

In the embodiment of the present disclosure, the pixel group formed by at least two adjacent target SPAD pixels includes at least a first pixel group and a second pixel group, the number of target SPAD pixels in the second pixel group is greater than the number of target SPAD pixels in the first pixel group, and the combinational logic processor 901 is further configured to:

Counting the first pixel groups in the SPAD array to obtain the number of the first pixel groups;

counting the second pixel groups in the SPAD array to obtain the number of the second pixel groups;

the basic quantity, the first pixel group quantity and the second pixel group quantity are weighted and summed to obtain a response parameter; the pixel group weight at least comprises a first sub weight corresponding to the first pixel group and a second sub weight corresponding to the second pixel group, and the second sub weight is larger than the first sub weight.

The embodiment of the disclosure also provides a computer readable storage medium, on which a computer program is stored, which when executed by a processor, implements the ToF ranging method in the above technical solution.

It should be noted here that: the description of the storage medium and the ToF ranging apparatus embodiments above are similar to the description of the ToF ranging method embodiments above, with similar benefits as the ToF ranging method embodiments. For technical details not disclosed in the embodiments of the disclosed storage medium and ToF ranging apparatus, please refer to the description of the embodiments of the disclosed ToF ranging method for understanding.

It should be appreciated that reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. It should be understood that, in various embodiments of the present disclosure, the sequence numbers of the foregoing processes do not mean the order of execution, and the order of execution of the processes should be determined by their functions and internal logic, and should not constitute any limitation on the implementation of the embodiments of the present disclosure. The foregoing embodiment numbers of the present disclosure are merely for description and do not represent advantages or disadvantages of the embodiments.

The foregoing description is only of the preferred embodiments of the present disclosure, and is not intended to limit the scope of the present disclosure, but rather, the equivalent structural changes made by the present disclosure and the accompanying drawings under the inventive concept of the present disclosure, or the direct/indirect application in other related technical fields are included in the scope of the present disclosure.

Claims

1. A ToF ranging method, the method comprising:

2. The method of claim 1, wherein adjusting the number of SPAD pixels in the SPAD array when the response parameter does not fall within the preset parameter range comprises:

3. The method of claim 1, wherein determining the response parameters of the SPAD array to the light pulses reflected by the object to be measured comprises:

4. A method according to claim 3, wherein determining, from the electrical signal, a response parameter of the SPAD array to an optical pulse reflected by a target to be measured, comprises:

5. A method according to claim 3, wherein the obtaining the number of voltage signals output by the SPAD array in response to an optical pulse comprises:

6. The method of claim 5, wherein the pixel group of at least two adjacent target SPAD pixels comprises at least a first pixel group and a second pixel group, the number of target SPAD pixels within the second pixel group being greater than the number of target SPAD pixels within the first pixel group;

7. The method of claim 4, wherein the obtaining the number of voltage signals output by the SPAD array in response to one light pulse comprises:

8. The method of claim 1, wherein determining a response parameter of the SPAD array to the light pulses reflected by the object under test when the light pulses are responded at least once comprises:

9. A ToF ranging apparatus, the apparatus comprising:

10. A computer readable storage medium, on which a computer program is stored, characterized in that the computer program, when being executed by a processor, implements the method of any one of claims 1 to 8.