CN111796296A

CN111796296A - Distance measuring method, system and computer readable storage medium

Info

Publication number: CN111796296A
Application number: CN202010501329.1A
Authority: CN
Inventors: 李国花; 何燃; 王瑞; 朱亮; 闫敏
Original assignee: Shenzhen Oradar Technology Co Ltd
Current assignee: Shenzhen Oradar Technology Co Ltd
Priority date: 2020-06-04
Filing date: 2020-06-04
Publication date: 2020-10-20

Abstract

The invention provides a distance measuring method, a distance measuring system and a computer readable storage medium, wherein the method comprises the following steps: controlling the transmitter to emit a pulsed light beam; controlling the collector to have a first detection efficiency and receiving photons with the first detection efficiency; the pixel array of the collector comprises a reference pixel array and an imaging pixel array; the reference pixel array comprises at least one reference pixel for receiving a reference photon; the imaging pixel array comprises at least one imaging pixel for receiving photons in the pulsed light beam reflected back through the target area to form a first photon signal; regulating and controlling the detection efficiency of the imaging pixel array according to the number of reference photons received by the reference pixel array within preset time and controlling the collector to receive photons with second detection efficiency until a second photon signal formed by the imaging pixel array meets preset requirements; and calculating the flight time of the pulse light beam according to the second photon signal.

Description

Distance measuring method, system and computer readable storage medium

Technical Field

The present invention relates to the field of ranging technologies, and in particular, to a distance measuring method and system, and a computer-readable storage medium.

Background

A distance measurement may be performed on a target using a Time of Flight (TOF) principle to obtain a depth image including a depth value of the target, and a distance measurement system based on the Time of Flight principle has been widely used in the fields of consumer electronics, unmanned driving, AR/VR, and the like. A distance measuring system based on the time-of-flight principle generally comprises an emitter and a collector, the field of view of a target is illuminated by a pulsed light beam emitted by the emitter and a reflected light beam is collected by the collector, and the distance to the object is calculated by calculating the time required for the light beam to be received from emission to reflection.

The emitters in current distance measuring systems based on the time-of-flight principle comprise an array of pixels, in particular a pixel array comprising single photon avalanche photodiodes (SPADs), which, when a photon in the emitted beam is incident on the SPAD, trigger an avalanche event output signal for recording the time of arrival of the photon at the SPAD, on the basis of which the time required for the beam to be emitted to be received is calculated. However, since the SPAD needs to wait for a dead time (dead time) to receive the next photon after receiving one photon, only one photon at most can be received for a plurality of photons in the dead time. In the case of an object at a short distance, an object with high reflectance, or strong ambient light, a large number of photons are incident on the SPAD at an earlier time to saturate the SPAD, and the SPAD cannot detect the subsequently incident photons, so that the pulse waveform drawn in the histogram circuit is abnormal, the reception time of the optical pulse cannot be determined, and it is difficult to determine the distance to the target object.

The above background disclosure is only for the purpose of assisting understanding of the concept and technical solution of the present invention and does not necessarily belong to the prior art of the present patent application, and should not be used for evaluating the novelty and inventive step of the present application in the case that there is no clear evidence that the above content is disclosed at the filing date of the present patent application.

Disclosure of Invention

The present invention provides a distance measuring method, system and computer readable storage medium for solving the existing problems.

In order to solve the above problems, the technical solution adopted by the present invention is as follows:

a distance measurement method comprising: t1: controlling the transmitter to emit a pulsed light beam;

t2: controlling the collector to have a first detection efficiency and receiving photons with the first detection efficiency; the pixel array of the collector comprises a reference pixel array and an imaging pixel array; the reference pixel array comprises at least one reference pixel for receiving reference photons; the imaging pixel array comprises at least one imaging pixel for receiving photons in the pulsed light beam reflected back through a target area to form a first photon signal; t3: regulating the detection efficiency of the imaging pixel array to be second detection efficiency according to the number of the reference photons received by the reference pixel array within a preset time, and controlling the collector to receive photons with the second detection efficiency until the imaging pixel array receives photons in the pulse light beams reflected by a target area to form a second photon signal to meet a preset requirement; t4: calculating a time of flight of the pulsed light beam from emission to reception from the second photon signal.

In one embodiment of the invention, the second detection efficiency of the imaging pixel array is regulated to be lower or higher than the first detection efficiency.

In another embodiment of the present invention, before step T3, the method further includes: presetting a threshold value of the number of reference photons received by the reference pixel array within the predetermined time. When the number of the reference photons received by the reference pixel array is smaller than the threshold value within a preset time, controlling the second detection efficiency of the collector to be larger than the first detection efficiency; and when the number of the reference photons received by the reference pixel array in a preset time is larger than or equal to the threshold value, controlling the second detection efficiency of the collector to be equal to the first detection efficiency.

In still another embodiment of the present invention, before step T3, the method further includes: predefining a correspondence of the number of reference photons received by the reference pixel array within the predetermined time to a detection efficiency of the imaging pixel. And regulating and controlling the detection efficiency of the imaging pixel in real time according to the corresponding relation between the number of the reference photons received by the reference pixel array within the preset time and the reference photon number, and determining the second detection efficiency.

The present invention also provides a distance measuring system comprising: a transmitter for transmitting a pulsed light beam to a target area; a collector including a pixel array composed of a plurality of pixels; the pixel array comprises a reference pixel array and an imaging pixel array; the reference pixel array comprises at least one reference pixel for receiving reference photons; the imaging pixel array comprises at least one imaging pixel for receiving photons in the pulsed light beam reflected back through a target area to form a first photon signal; and the control and processing circuit is connected with the transmitter and the collector and is used for realizing the method.

In one embodiment of the invention, the reference photons comprise ambient photons. The reference pixel array is configured as at least one column or row of reference pixels disposed along a peripheral edge of the imaging pixel array.

The invention further provides a computer-readable storage medium, in which a computer program is stored, which, when being executed by a processor, carries out the steps of the method as set forth in any of the above.

The invention has the beneficial effects that: provided are a distance measuring method, system, and computer-readable storage medium that eliminate the pile _ up phenomenon of received waveform distortion without reducing the frame rate in the measurement process by adjusting the detection efficiency of imaging pixels according to the number of reference photons (ambient photons) received by reference pixels.

Furthermore, the number of times of adjusting the detection efficiency of the imaging pixel is reduced by presetting the threshold value of the number of reference photons received by the reference pixel array in the preset time, and the complexity of adjustment is reduced.

Furthermore, the accuracy of the system is improved by predefining the corresponding relation between the number of reference photons received by the reference pixel array in the preset time and the detection efficiency of the imaging pixel.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 is a schematic diagram of a distance measuring system according to an embodiment of the present invention.

Fig. 2(a) is a schematic structural diagram of an emitter in an embodiment of the present invention.

Fig. 2(b) is a schematic structural diagram of a collector in the embodiment of the present invention.

Fig. 3 is a schematic diagram of a first distance measurement method in an embodiment of the present invention.

Fig. 4 is a schematic diagram of a first distance measuring system according to an embodiment of the present invention.

Fig. 5 is a schematic diagram of a pixel unit in a collector according to an embodiment of the present invention.

Fig. 6 is a schematic diagram of a second distance measurement method in the embodiment of the present invention.

Fig. 7 is a schematic diagram of a second distance measuring system in an embodiment of the present invention.

Fig. 8 is a schematic diagram of a third distance measuring system in an embodiment of the present invention.

Fig. 9 is a schematic diagram of a third distance measurement method in the embodiment of the present invention.

Fig. 10 is a schematic diagram of a pixel unit in another embodiment of the present invention.

Fig. 11 is a schematic structural diagram of another collector in the embodiment of the present invention.

Fig. 12 is a schematic diagram of a manufacturing method of a collector in an embodiment of the present invention.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the embodiments of the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and the embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element. In addition, the connection may be for either a fixing function or a circuit connection function.

It is to be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in an orientation or positional relationship indicated in the drawings for convenience in describing the embodiments of the present invention and to simplify the description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed in a particular orientation, and be in any way limiting of the present invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the embodiments of the present invention, "a plurality" means two or more unless specifically limited otherwise.

An avalanche photodiode refers to a photosensitive element used in laser communication. After a reverse bias is applied to the P-N junction of a photodiode made of silicon or germanium, the incident light is absorbed by the P-N junction to form a photocurrent. Increasing the reverse bias voltage produces an "avalanche" (i.e., a multiple surge in photocurrent) phenomenon, and such diodes are referred to as "avalanche photodiodes".

Fig. 1 is a schematic diagram of a distance measuring system 10 according to an embodiment of the present invention, which includes a transmitter 11, a collector 12, and a control and processing circuit 13. Wherein, the emitter 11 is used to emit a light beam 30 to the target area 20, the light beam is emitted to the target area space to illuminate the target object in the space, at least part of the emitted light beam 30 is reflected by the target area 20 to form a reflected light beam 40, at least part of the reflected light beam 40 is received by the collector 12, the control and processing circuit 13 is respectively connected with the emitter 11 and the collector 12, the trigger signals of the emitter 11 and the collector 12 are synchronized to calculate the time required by the light beam from emission to reception, i.e. the flight time t between the emitted light beam 30 and the reflected light beam 40, further, the distance D of the corresponding point on the target object can be calculated by the following formula:

D＝c·t/2 (1)

where c is the speed of light.

The transmitter 11 includes a light source 111, a transmitting optical element 112, a driver 113, and the like. The light source 111 may be a Light Emitting Diode (LED), a Laser Diode (LD), an Edge Emitting Laser (EEL), a Vertical Cavity Surface Emitting Laser (VCSEL), or the like, or may be a one-dimensional or two-dimensional light source array composed of a plurality of light sources, preferably, the light source array is a VCSEL array light source chip formed by generating a plurality of VCSEL light sources on a single semiconductor substrate, and the arrangement of the light sources in the light source array may be regular or irregular. The light beam emitted by the light source 111 may be visible light, infrared light, ultraviolet light, or the like. The light source 111 emits a light beam outward under the control of the driver 113. In one embodiment, the light source 111 emits a pulsed light beam outward under the control of the driver 113 at a frequency (pulse period) that can be used in Direct time of flight (Direct TOF) measurements, the frequency being set according to the measurement distance. It will be appreciated that the light beam emitted by the light source 111 may also be controlled by means of a part of the control and processing circuit 13 or a sub-circuit present independently of the control and processing circuit 13.

The emission optical element 112 receives the light beam emitted from the light source 111 and projects the light beam to a target region after shaping. In one embodiment, the transmitting optical element 112 receives the pulsed light beam from the light source 111 and optically modulates, such as diffracting, refracting, reflecting, etc., the pulsed light beam, and then transmits the modulated light beam, such as a focused light beam, a flood light beam, a structured light beam, etc., into space. The emitting optical elements 112 may be in the form of one or more combinations of lenses, liquid crystal elements, diffractive optical elements, microlens arrays, Metasurface (Metasurface) optical elements, masks, mirrors, MEMS mirrors, and the like.

Collector 12 includes pixel unit 121, filter unit 122, and receiving optical element 123, where receiving optical element 123 is used to receive at least part of the light beam reflected by the target and guide the light beam onto pixel unit 121, and filter unit 122 is used to filter out background light or stray light. The pixel unit 121 comprises a two-dimensional pixel array of a plurality of pixels, and in one embodiment, the pixel unit 121 comprises a pixel array of single photon avalanche photodiodes (SPADs) that are responsive to incident single photons and output signals indicative of respective times of arrival of received photons at each SPAD, and the acquisition of the weak light signals and the calculation of time of flight are accomplished using, for example, time-correlated single photon counting (TCSPC).

And the control and processing circuit 13 synchronizes the trigger signals of the emitter 11 and the collector 12, processes the photon signals of the pixel collected light beams, and calculates the distance information of the target to be measured based on the flight time of the reflected light beams. In one embodiment, the SPAD outputs a photon signal in response to an incident single photon, and the control and processing circuitry 13 receives the photon signal and performs signal processing to obtain the time of flight of the beam. In particular, the control and processing circuit 13 calculates the number of photons collected to form successive time bins, which are joined together to form a statistical histogram for reconstructing the time series of the reflected beam, and identifies the time of flight of the reflected beam from emission to reception using peak matching and filtering detection. In some embodiments, the control and processing circuitry 13 includes readout circuitry (not shown) comprising one or more of signal amplifiers, time-to-digital converters (TDCs), digital-to-analog converters (ADCs), and the like. These circuits may be integrated with the pixels or may be part of the control and processing circuit 13, and for convenience of description, they will be collectively considered as part of the control and processing circuit 13. It will be appreciated that the control and processing circuitry 13 may be separate dedicated circuitry, such as a dedicated SOC chip, FPGA chip, ASIC chip, etc., or may comprise general purpose processing circuitry.

In some embodiments, the distance measurement system 10 further includes a memory for storing a pulse code program with which to control the excitation time, emission frequency, etc. of the light beam emitted by the light source 111.

In some embodiments, the distance measurement system 10 may further include a color camera, an infrared camera, an IMU, etc., and a combination thereof may implement more rich functions, such as 3D texture modeling, infrared face recognition, SLAM, etc.

In some embodiments, emitter 11 and collector 12 may be arranged coaxially, i.e. they are implemented by an optical device with reflection and transmission functions, such as a half-mirror.

Fig. 2(a) and 2(b) are schematic structural diagrams of the emitter and the collector according to the first embodiment of the present invention. Wherein the emitter 11 includes a light source array 21 comprised of a plurality of light sources arranged in a pattern on a single substrate. The substrate may be a semiconductor substrate, a metal substrate, etc., and the light source may be a light emitting diode, an edge emitting laser, a Vertical Cavity Surface Emitting Laser (VCSEL), etc., and preferably, the light source array 21 is an array VCSEL chip composed of a plurality of VCSEL light sources disposed on the semiconductor substrate. The light source array 21 emits light under modulation driving of a driving circuit (which may be a part of the control and processing circuit 13), or may emit light in groups or as a whole under control of the driving circuit.

The pixel unit 121 includes a pixel array 22 and a readout circuit 23, wherein the pixel array 22 includes a two-dimensional array of a plurality of pixels for collecting at least a portion of the light beam reflected back by the object and generating a corresponding photon signal, and the readout circuit 23 is configured to process the photon signal to calculate the time of flight.

In one embodiment, the readout circuit 23 includes a TDC circuit 231 and a histogram circuit 232, which are used to plot a histogram reflecting the pulse waveform emitted by the light source in the emitter, and further, the time of flight can also be calculated according to the histogram, and the result is finally outputted. The readout circuit 23 may be a single TDC circuit and a histogram circuit, or may be an array readout circuit including a plurality of TDC circuit units and histogram circuit units.

In one embodiment, pixel array 22 is a pixel array comprising a plurality of SPADs, and when emitter 11 emits a spot beam toward a measured object, receiving optical element 123 in collector 12 directs the spot beam onto the corresponding pixel, and generally, in order to receive as many photon signals in the reflected beam as possible, the size of the single spot is generally set to correspond to a plurality of pixels (where corresponding is understood to be imaging, optical element 112 generally includes an imaging lens). For example, as shown in fig. 2(b), a single spot corresponds to 2 × 2 to 4 pixels, that is, photons reflected by a light beam of the spot are received by the corresponding 4 pixels with a certain probability, generally, a pixel region formed by a plurality of corresponding pixels is referred to as a "combined pixel", and the size of the combined pixel needs to be considered comprehensively according to a ranging system when setting. In one embodiment, each light source in the light source array 21 is configured to be paired with each combined pixel in the pixel array 22, i.e., the projected field of view of each light source corresponds to the acquisition field of view of the corresponding combined pixel. As shown in fig. 2(b), the light beam emitted from the light source 211 is reflected by the object and then guided by the receiving optical element 123 to the combining pixel 221, the light beam emitted from the light source 212 is reflected by the object and then guided by the receiving optical element 123 to the combining pixel 224, and the light beam emitted from the light source 213 is reflected by the object and then guided by the receiving optical element 123 to the combining pixel 225.

Generally, the distance measurement system between emitter 11 and collector 12 can be split between on-axis and off-axis depending on the arrangement. For the coaxial situation, the light beam emitted by the emitter 11 is reflected by the object to be measured and then is collected by the corresponding combined pixel in the collector 12, and the position of the combined pixel is not influenced by the distance of the object to be measured; however, in the case of off-axis, due to the existence of parallax, when the distance of the object to be measured is different, the position of the light spot on the pixel unit also changes, and generally shifts along the direction of the baseline (the connecting line between the emitter 11 and the collector 12, in the present invention, the direction of the baseline is uniformly represented by a horizontal line), and when the distance of the object to be measured is unknown, the position of the combined pixel is uncertain, in order to solve this problem, it is necessary to adopt the super-pixel technology, that is, a plurality of pixels with a number greater than the corresponding number of the combined pixel are arranged to form a pixel region, which is referred to as "super-pixel" herein, for receiving the reflected speckle beam, and one super-pixel 222 in the embodiment shown in fig. 2(b) includes three combined pixels. When the size of the super-pixel is set, the measurement range of the distance measurement system 10 and the length of the baseline need to be considered at the same time, so that the combined pixels corresponding to the spots reflected back by the object at different distances in the measurement range all fall into the super-pixel area, that is, the size of the super-pixel should exceed at least one combined pixel. In general, the size of a super-pixel is the same as a co-pixel in the direction perpendicular to the baseline, and is larger than the co-pixel in the direction along the baseline. The number of superpixels is generally the same as the number of spot beams acquired by a single measurement of collector 12.

A receive waveform is plotted in histogram circuit 232 that reflects the shape of the pulse emitted by the light source in the emitter, typically substantially similar in shape to the emitted pulse waveform, the receive waveform representing the number of photons in the reflected pulse incident on the pixel array. The photons received by the pixel array include ambient photons, which persist over a time bin of the histogram, and signal photons, which appear to form pulse peaks only within the time bin corresponding to the target location. However, because the SPAD array enters the dead time after receiving photons and does not detect photons any more, when the target to be detected is closer to the SPAD array or has high reflectivity, the photons in the front of the reflected beam are more quickly incident on the SPAD array to saturate a plurality of SPADs, and the probability that the subsequently incident photons are collected by the SPADs is reduced, so that the pulse peak position is advanced. Or, under strong ambient light conditions, a large number of ambient photons are incident into the SPAD array to saturate a plurality of SPADs, and then the probability that signal photons are collected by the SPADs is reduced, resulting in distortion of the formed received waveform, and inaccurate TOF values determined using the peaks of the distorted received waveform. The above-generated case of distortion of the received waveform is collectively referred to as the pile _ up phenomenon, and it will be described below by some embodiments that if this problem is solved, the accuracy of the distance measurement system is improved.

First embodiment

Fig. 3 is a flowchart of a distance measuring method according to a first embodiment of the present invention. The distance measuring method is executed by a control and processing circuit 13 in the distance measuring system, and the specific method steps are as follows:

and S1, controlling the emitter to emit the pulse light beam towards the target area.

Wherein the emitter 11 comprises an array of light sources 21 emitting a pulsed light beam in a speckle pattern towards the target area, which forms a reflected light beam after reflection by an object in the target area.

S2, regulating and controlling a pixel array of a collector to have at least two different detection efficiencies, receiving photon signals formed by photons in light beams reflected by the target area respectively according to the at least two different detection efficiencies, and obtaining depth images of the target area respectively according to the photon signals;

the control and processing circuitry 13 varies the detection efficiency (PDE) of the pixel array by regulating the reverse bias voltage applied to each pixel in the pixel array 22. Wherein, PDE is the ratio of the number of detected effective photons to the total number of incident photons in a unit time, the PDE of each pixel is closely related to the reverse bias voltage applied to the pixel, the higher the reverse bias voltage applied to the pixel, the longer the avalanche duration, the PDE is significantly increased, when the reverse bias voltage applied to the pixel is lower, the PDE is also decreased, when the reverse bias voltage is lower than the breakdown voltage, avalanche quenching is caused, and the pixel does not receive photons any more. However, the bias voltage is not infinitely increased, and when the bias voltage is set too high, the dark count rate may be significantly increased, so that the value of the reverse bias voltage needs to be reasonably set according to the system requirements in practical applications.

In the invention, the pixel array of the collector is controlled to have at least two different detection efficiencies to respectively obtain photon signals formed by photons in light beams reflected by an object to be measured in different distance ranges, the different detection efficiencies correspond to the distance measuring ranges, reflectivity and the like of different distance measuring systems, namely, the distance measuring range adopting the low detection efficiency is smaller and is used for processing near distance, high reflectivity and strong ambient light; the range finding range adopting high detection efficiency is far, and the long-distance, low-reflectivity and low-ambient light can be processed. In fact, the number of detection efficiencies can be set according to specific situations. The pixel array of the control collector has at least one detection efficiency for collecting photon signals formed by photons in light beams reflected by all targets to be measured in the target area.

In an embodiment of the present invention, a plurality of detection efficiencies may be set according to the distance between the target to be detected in the target region, and the difference between the plurality of detection efficiencies may be equal or unequal.

In one embodiment of the invention, the pixel array of the control collector has a first detection efficiency and a second detection efficiency respectively, and receives photon signals formed by photons in light beams reflected by an object to be measured in the target area at the first detection efficiency and the second detection efficiency respectively.

Specifically, when the first detection efficiency is lower than the second detection efficiency, the control and processing circuit 13 controls the pixel array 22 to have the first detection efficiency (when the reverse bias voltage applied to the pixels is low), that is, the pixel array 22 has a low PDE. At this time, the acquisition of the first frame depth image of the target field of view is completed. Then photons in the beam reflected by a first target closer to collector 12 are received by pixels in pixel array 22 to form a first photon signal; alternatively, photons in the beam reflected by the first target having the higher reflectivity are received by pixels in the pixel array 22 to form a first photon signal. Even in strong ambient light, the signal photons received in the effectively reflected beam form the first photon signal with reduced influence of ambient photons, since the pixel now has a lower PDE. The control and processing circuit 13 calculates a first flight time according to the first photon signal to obtain a first depth image of the target area, and a pixel point of the first depth image has a first TOF value.

It can be understood that the problem of pile _ up is effectively solved by reducing the PDE of the pixel array 22, the accuracy of measuring a near target is improved, but the PDE of the pixel array is reduced, and accordingly the range of the ranging system is also reduced, for a second target farther away from the collector or a second target with lower reflectivity, the pixel array 22 is difficult to collect a sufficient number of effective photons, and a second photon signal with a sufficient signal-to-noise ratio cannot be generated, and a second flight time representing the distance information of the second target cannot be calculated. The next step is taken to determine a second time of flight for the second target.

Then, the pixel array in the collector is regulated to have second detection efficiency, the pixel array receives photons in the light beam reflected by the target area to form a second photon signal and a third photon signal, and a second depth image of the target area is obtained according to the second photon signal and the third photon signal.

The control and processing circuit 13 regulates and controls the pixel array 22 to have a second detection efficiency (at this time, the reverse bias voltage applied to the pixels is higher, wherein the second detection efficiency is greater than the first detection efficiency, at this time, the pixel array 22 has a higher PDE, and completes the acquisition of a second frame depth image of the target region, at this time, photons in the light beam reflected by a second target farther away from the collector 12 can be received by the pixels in the pixel array 22 to form a second photon signal, or photons in the light beam reflected by a second target with lower reflectivity can be received by the pixels in the pixel array 22 to form a second photon signal, the control and processing circuit 13 calculates a second flight time according to the second photon signal to form a second depth image of the target region, and a part of pixel points in the second depth image have a second TOF value.

In one embodiment, the second detection efficiency is capable of detecting the object located at the farthest distance from the system, in one embodiment of the present invention, the maximum detection distance from the detection system is 150m, and the second detection efficiency can form a photon signal by receiving the photons reflected back when the object is located at 150 m; whereas a first detection efficiency can only receive photons reflected back by a target located at 20 m.

In addition, when the pixel array has a higher PDE, the pixel array may also receive photons in the light beam reflected by the first target to generate a third photon signal, and the control and processing circuit 13 may calculate a third flight time representing distance information of the first target according to the third photon signal, so that a part of pixel points in the second depth image have a third TOF value, but due to the existence of the pileup phenomenon, the third TOF value on the same pixel point is smaller than the first TOF value (accurate TOF value). Thus, in the next step an accurate depth image of the target region is determined.

It is to be understood that the present invention is equally applicable when the first detection efficiency is greater than said second detection efficiency. I.e. the control and processing circuit 13 conditions the pixel array 22 to have a first detection efficiency (when the reverse bias voltage applied to the pixels is higher), i.e. the pixel array 22 has a higher PDE. The pixel array 22 receives a fourth photon signal and a fifth photon signal formed by photons in the light beam reflected by the target area, and obtains a fourth depth image and a fifth depth image of the target area according to the fourth photon signal and the fifth photon signal respectively; the pixel array is then tuned to have a second detection efficiency (when the reverse bias voltage applied to the pixels is lower), i.e. the pixel array 22 has a lower PDE. The pixel array receives photons in the light beam reflected by the target area to form a sixth photon signal, and a sixth depth image of the target area is obtained according to the sixth photon signal. And will not be described in detail herein.

And S3, fusing the depth images of the target area to obtain a depth image fused with the target area.

And when the depth image of the target area is fused to obtain a depth image fused with the target area, selecting the depth value of the target to be detected in the depth image corresponding to high and low efficiency in the at least two different detection efficiencies according to the distance of the target to be detected.

Specifically, as described above, the control and processing circuit 13 assigns the first TOF value of each pixel point in the first depth image to the corresponding pixel point in the second depth image to replace the third TOF value of the pixel point, so as to form a third depth image, where the TOF value corresponding to each pixel point in the third depth image is the accurate flight time. It is to be understood that the pixel referred to herein mainly refers to a pixel having an effective TOF value.

The processing is similar for the fourth depth image, the fifth depth image and the sixth depth image.

The method based on the invention also provides a distance measuring system for realizing the method.

Fig. 4 is a schematic diagram of a distance measuring system according to a first embodiment of the present invention.

In this embodiment, the pixel array of the acquisition unit is regulated to have at least two different detection efficiencies, photon signals formed by photons in the light beam reflected by the target region are received by the at least two different detection efficiencies, depth images of the target region are obtained according to the photon signals, the depth images are fused into one frame of depth image, and measurement errors caused by pile _ up are effectively corrected.

By adopting the method and the system, the corresponding depth image is obtained by regulating and controlling the pixel array of the collector to have at least two different detection efficiencies, then the depth values of the target to be detected in the depth image corresponding to high and low efficiency in the at least two different detection efficiencies are selected according to the distance of the target to be detected, the fused depth image is obtained by fusing, and the pile _ up phenomenon of received waveform distortion is eliminated.

Second embodiment

Fig. 5 is a schematic diagram of a pixel unit in a collector according to a second embodiment of the present invention. The pixel unit comprises a pixel array 41 and a readout circuit 44, wherein the pixel array 41 comprises a two-dimensional array of a plurality of pixels for collecting at least part of the light beam reflected back by the object and generating a corresponding photon signal, and the readout circuit 41 is configured to process the photon signal to calculate the time of flight.

In one embodiment, the readout circuit 44 includes a TDC circuit 441 and a histogram circuit 442 for plotting a histogram reflecting the waveform of the pulses emitted by the light source in the emitter, and further, calculating the time of flight according to the histogram, and finally outputting the result. The readout circuit 44 may be a single TDC circuit and a histogram circuit, or may be an array readout circuit composed of a plurality of TDC circuit units and histogram circuit units.

In one embodiment, the pixel array 41 is a pixel array composed of a plurality of single photon avalanche photodiodes (SPADs), wherein the pixel array 41 includes a reference pixel array 42 and an imaging pixel array 43. The reference pixel array 42 includes at least one reference pixel 421.

As in the embodiment shown in fig. 5, the reference pixel array 42 is configured as a column of reference pixels disposed along the peripheral edge of the imaging pixel array 43, and in other embodiments, the reference pixel array 42 may be disposed in at least one column or row; alternatively, the reference pixel is located at any given position around the imaging pixel array 43. The configuration of the imaging pixel array 43 is as described in the pixel array shown in fig. 2(b), and will not be repeated here.

The control and processing circuit 13 controls the emitter 11 to emit a pulse light beam toward the target area, controls the pixels in the collector to be turned on to receive photons in the reflected light beam, guides the reflected light beam reflected by the target area to be imaged by the receiving optical element 123 to the imaging pixel array 43, and the imaging pixels in the imaging pixel array 43 collect photons in the reflected light beam to form photon signals, and the control and processing circuit 13 calculates the flight time of the reflected light beam from emission to reception according to the photon signals. However, due to the existence of the pile _ up phenomenon, errors may exist in the calculated reflected light beam, and therefore, the reference photon number received in a certain time is counted by configuring the reference pixel array 42, and the PDE of the imaging pixel in the imaging pixel array 43 at the time of next frame acquisition is regulated according to the reference photon number. The control and processing circuitry 13 varies the detection efficiency (PDE) of the imaging pixel array by regulating the reverse bias voltage applied across the imaging pixels in the imaging pixel array 43.

Where the reference photons received by the reference pixel array 42 during the predetermined time include ambient photons and possibly signal photons in the partially reflected beam, the number of reference photons used to characterize the product of the ambient light intensity and the target reflectivity is inversely proportional to the PDE of the imaging pixel. The detection efficiency of the imaging pixel array is adjusted and controlled according to the number of reference photons received by the reference pixel array 42 within a predetermined time, and the collector is controlled to receive photons with the adjusted detection efficiency until the imaging pixel array receives photons in the pulsed light beam reflected by the target area to form a second photon signal to meet a predetermined requirement. The predetermined requirement described herein may be that a predetermined accuracy or the like is satisfied, and the number of times of adjustment is at least once.

In one embodiment of the invention, the detection efficiency of the array of imaging pixels is adjusted to be lower or higher than the first detection efficiency, in particular, according to the inverse proportional relationship between the number of reference photons and the PDE of the imaging pixels.

In one embodiment, a threshold value for the number of reference photons received by the reference pixel array 42 within a certain time is preset, for example, a certain time is set to 10us, during the first frame depth map acquisition, the control and processing circuit 13 controls the imaging pixel array to receive photons in the reflected light beam with a first detection efficiency (lower PDE), and at the same time, the reference pixel array 42 is controlled to receive reference photons, if the number of reference photons received within 10us is smaller than the threshold value during the time of the lower ambient light and/or the lower target reflectivity, then the control and processing circuit 13 controls the imaging pixel array 43 to receive photons in the reflected light beam with a second detection efficiency (higher PDE) during the next frame acquisition, and if the number of reference photons is greater than or equal to the threshold value, the imaging pixel array still has the first detection efficiency during the next frame acquisition. By setting a threshold value of the reference photon number, the number of times of adjusting the PDE of the imaging pixel is less, and the complexity of the system during adjustment is reduced.

In one embodiment, the corresponding relationship between the number of reference photons received by the reference pixel array 42 in a predetermined time and the PDE of the imaging pixel may be predefined, and the control and processing circuit 13 may determine the PDE of the imaging pixel array 43 of the next frame according to the number of reference photons received by the reference pixel array 42 of the current frame and the predefined corresponding relationship, so as to implement real-time regulation. In a distance measurement system in practical application, a plurality of uncontrollable factors are generally encountered, for example, a LiDAR system used in automatic driving, situations of environment change or target change can occur in a continuous measurement process, distance measurement errors caused by the situations can be effectively solved by regulating and controlling a PDE of an imaging pixel in real time, the accuracy of the system is improved, and in addition, the frame rate in the measurement process does not need to be reduced by the method.

As shown in fig. 6, based on the description of the second embodiment, a distance measuring method is also proposed, which includes the steps of:

t1: controlling the transmitter to emit a pulsed light beam;

t2: controlling the collector to have a first detection efficiency and receiving photons with the first detection efficiency; the pixel array of the collector comprises a reference pixel array and an imaging pixel array; the reference pixel array comprises at least one reference pixel for receiving reference photons; the imaging pixel array comprises at least one imaging pixel for receiving photons in the pulsed light beam reflected back through a target area to form a first photon signal;

t3: regulating the detection efficiency of the imaging pixel array to be second detection efficiency according to the number of the reference photons received by the reference pixel array within a preset time, and controlling the collector to receive photons with the second detection efficiency until the imaging pixel array receives photons in the pulse light beams reflected by a target area to form a second photon signal to meet a preset requirement;

it is understood that the detection efficiency of the modulation imaging pixel array is lower or higher than the first detection efficiency, and is a reference for obtaining the imaging condition of the target area according to the reference photon number received by the reference pixel array.

T4: calculating a time of flight of the pulsed light beam from emission to reception from the second photon signal.

In one embodiment, a threshold value for receiving the reference photon quantity within a certain time is set, and the detection efficiency of the pixel array is regulated according to the reference photon quantity; if the reference photon quantity is greater than or equal to the threshold value, the control and processing circuit regulates and controls the imaging pixel array to have first detection efficiency when the next frame is collected; if the reference photon number is smaller than the threshold value, the control and processing circuit regulates and controls the imaging pixel array to have second detection efficiency when the next frame is collected; wherein the second detection efficiency is greater than the first detection efficiency.

In one embodiment, a correspondence table between the number of reference photons and the detection efficiency of the imaging pixel is stored in advance, and the detection efficiency of the imaging pixel array of the next frame is regulated and controlled by querying the correspondence table according to the number of reference photons.

Fig. 7 is a schematic diagram of a distance measuring system according to a second embodiment of the present invention.

By adopting the distance measuring method and the distance measuring system, the detection efficiency of the imaging pixel is adjusted according to the number of reference photons (environmental photons) received by the reference pixel, and the pile _ up phenomenon of received waveform distortion is eliminated under the condition of not reducing the measuring frame rate.

Furthermore, the adjustment accuracy is improved by predefining the corresponding relation between the number of reference photons received by the reference pixel array in the preset time and the detection efficiency of the imaging pixel.

Third embodiment

Fig. 8 is a schematic view of a distance measuring system according to a third embodiment of the present invention. Distance measurement system 60 includes transmitter 11, collector 12, camera 14, and control and processing circuitry 13. Wherein, emitter 11 is used for emitting light beam 30 to target area 20, and the light beam is emitted to target area space in order to illuminate the target object in the space, and at least part of emitted light beam 30 forms reflected light beam 40 after reflecting through target area 20, and at least part of reflected light beam 40 is received by collector 12, and control and processing circuit 13 is connected with emitter 11 and collector 12 respectively, and the trigger signal of synchronous emitter 11 and collector 12 is in order to calculate the time that the light beam takes from emitting to receiving. On the other hand, the control and processing circuit 13 is connected to a camera 14, the camera 14 being used to capture a gray scale image of the target area, wherein the gray scale values of the pixel points in the gray scale image represent the total light intensity of the light beam 50 reflected by the target and the ambient light. Control and processing circuit 13 regulates and controls the detection efficiency (PDE) of the corresponding pixel in the pixel array in collector 12 according to the gray value of the pixel in the gray image.

Specifically, the camera 14 includes a first pixel unit 141 for acquiring a gray scale image of the target area, and the first pixel unit 141 includes a first pixel array (not shown) composed of a plurality of first pixels, where pixel points in the gray scale image correspond to the first pixels in the first pixel unit 141 one to one. The camera 14 may be a grayscale camera, an RGB camera, or the like, preferably a grayscale camera. Collector 12 includes a second pixel element 121, and in one embodiment, second pixel element 121 is configured as shown in fig. 2(b), and includes a pixel array 22 and a readout circuit 23, where for convenience of description in this embodiment, pixel array 22 is referred to as a second pixel array, and the second pixel array includes a two-dimensional array composed of a plurality of second pixels, and preferably the second pixels are SPAD pixels. Camera 14 and collector 12 are configured to have the same collection field of view, such that at least one first pixel is paired with at least one second pixel (in this embodiment, the second pixel may be a combined pixel or a super pixel).

The control and processing circuit 13 determines the light intensity of the reflected light beam according to the gray value of each pixel point in the gray image, the gray value is between 0 and 255 and is divided into 256 levels, and the larger the gray value is, the larger the light intensity of the corresponding reflected light beam is. It can be understood that a first target closer to the collector reflects a light beam having a greater light intensity than a second target farther from the collector; or, the light beam reflected by a first target with higher reflectivity has a greater light intensity than the light beam reflected by a second target with lower reflectivity; or under the influence of strong ambient light, the reflected ambient light can correspondingly increase the gray value of the pixel point in the gray image.

In order to effectively reduce the influence of the pile _ up phenomenon, the control and processing circuit 13 adjusts the PDE corresponding to the second pixel in the second pixel array according to the gray value of the pixel point in the gray image. The control and processing circuitry regulates the detection efficiency of the second pixels by varying the reverse bias voltage applied across the second pixels in the second pixel array. Usually, when the depth map of the next frame is collected, the control and processing circuit 13 regulates and controls the PDE of each second pixel in the second pixel array, and the second pixel array does not have a uniform PDE any more at this time, so that the measurement accuracy is effectively improved when a plurality of different targets to be measured exist in the target area.

In one embodiment, a correspondence table of the gradation value of the gradation image and the value of the detection efficiency of the second pixel is stored in advance. The control and processing circuit 13 determines the corresponding PDE of the second pixel according to the gray value lookup relation table of each pixel point in the gray image, and adjusts and controls the reverse bias voltage applied to the second pixel to change the PDE of the second pixel during the next frame acquisition. The corresponding relation table of the gray value and the PDE value can be obtained by calibration.

In one embodiment, the gray value of the gray image is divided into at least two steps in sequence in advance, and the detection efficiency of the second pixel corresponding to each step is configured. Specifically, the gray values are arranged in a stepwise manner in the order from small to large (or from large to small), and each stepwise is configured to have a corresponding PDE. For example, the gray scale value of the first step is in the range of 0-85, the gray scale value of the second step is in the range of 86-171, the gray scale value of the third step is in the range of 172-256, and the corresponding PDEs of the second pixel are set as the first PDE (higher PDE), the second PDE (middle PDE), and the third PDE (lower PDE). The control and processing circuit 13 processes the gray image according to the gray value steps to divide the image into a plurality of first closed-loop regions, and the gray values of all pixel points in the same closed-loop region belong to the same step. Further, according to the coordinates of the pixel points on the boundary line of the first closed-loop area, a second closed-loop area corresponding to the first closed-loop area in the second pixel array is determined, and the detection efficiency of all second pixels in the second closed-loop area is regulated and controlled according to the detection efficiency corresponding to the step. For example, if the gray value in the first closed-loop region belongs to the first step, all the second pixels in the first closed-loop region are controlled to have the first PDE. The time for regulation can be increased by such a hierarchical setting of the region regulation. It is to be understood that the above regulation method is only one embodiment of the present invention, and does not specifically limit the content of the present invention.

As shown in fig. 9, based on the description of the third embodiment, a distance measuring method is also proposed, which includes the steps of:

p1: controlling the transmitter to emit a pulsed light beam;

p2: controlling a first pixel array of a gray scale image acquisition unit to acquire a gray scale image of a target area, and simultaneously controlling a second pixel array of an acquisition unit to have first detection efficiency, and receiving a first photon signal formed by photons in the pulsed light beam reflected back by the target area with the first detection efficiency;

p3: regulating and controlling the detection efficiency of the corresponding second pixel in the second pixel array according to the gray value of the pixel point in the gray image until the second pixel array receives the photons in the pulse light beam reflected by the target area to form a second photon signal to meet the preset requirement;

p4: calculating a time of flight of the pulsed light beam from emission to reception from the second photon signal.

It will be appreciated that the predetermined requirement is that the pixel array is capable of receiving a sufficient number of photon signals to form a received waveform; or to receive a photon signal that meets a certain signal-to-noise ratio.

It is to be understood that in one embodiment of the present invention, the detection efficiency of the second pixel array is regulated to be lower or higher than the first detection efficiency.

It should be noted that, the distance measuring method of the present embodiment adopts the distance measuring system of the third embodiment to perform distance measurement, and the technical solution thereof is the same as that of the distance measuring system, and therefore, the detailed description thereof is omitted.

According to the distance measuring method and system provided by the embodiment of the invention, the detection efficiency of the second pixel of the collector is adjusted according to the gray value of the gray image, so that the pile _ up phenomenon of received waveform distortion is eliminated under the condition that the frame rate in the measuring process is not reduced.

Furthermore, by pre-storing the corresponding relation table of the gray value of the gray image and the value of the detection efficiency of the second pixel, the accuracy of measurement is effectively improved when a plurality of different targets to be measured exist in the target area.

Further, the gray value is divided into at least two steps in sequence, the detection efficiency of the second pixel corresponding to each step is configured, and the regulation and control time is adjusted and promoted through the grading setting area.

Fourth embodiment

Fig. 10 is a schematic diagram of a pixel unit in a collector according to a fourth embodiment of the invention. The pixel unit comprises a pixel array 61 and a readout circuit 64, wherein the pixel array 61 comprises a two-dimensional array of a plurality of pixels for collecting at least part of the light beam reflected back by the object and generating a corresponding photon signal, and the readout circuit 64 is configured to process the photon signal to calculate the time of flight.

In one embodiment, the readout circuit 64 includes a TDC circuit 641 and a histogram circuit 642 for plotting a histogram reflecting the waveform of the pulses emitted by the light source in the emitter, and further, calculating the time of flight according to the histogram and outputting the result. The readout circuit 64 may be a single TDC circuit and a histogram circuit, or an array readout circuit composed of a plurality of TDC circuit units and histogram circuit units.

In one embodiment, the pixel array 61 is a pixel array composed of a plurality of SPADs, when the emitter 11 emits a spot beam to the object to be measured, the receiving optical element 123 in the collector 12 directs the spot beam to a corresponding pixel, generally, in order to receive photon signals in the reflected beam as much as possible, the size of a single spot is generally set to correspond to a plurality of pixels (the correspondence here can be understood as imaging, and the receiving optical element 123 generally includes an imaging lens), for example, the single spot corresponds to 2 × 2 or 4 pixels as shown in fig. 10, that is, photons reflected by the spot beam are received by the corresponding 4 pixels with a certain probability, generally, a pixel area composed of the corresponding plurality of pixels is referred to as a "combined pixel", and the size of the combined pixel needs to be comprehensively considered when setting.

In the distance measurement system in which the emitter and the collector are arranged off-axis, due to the existence of parallax, when the distance of the object to be measured is different, the position of the light spot on the pixel unit also changes, and generally shifts along the direction of a base line (a connecting line between the emitter 11 and the collector 12, in the present invention, the direction of the base line is uniformly represented by a horizontal line), and when the distance of the object to be measured is unknown, the position of a combined pixel is uncertain.

In one embodiment, as shown in fig. 10, the super pixel 611 is configured to include a first and a

second pixel

621 and 622, and the super pixel 611 is connected to a TDC and histogram circuits. Wherein, the collection field of view of the super pixel is matched with the projection field of view of the corresponding light source, when the light source corresponding to the super pixel 611 emits a pulse light beam toward the corresponding area, if the first target at the area is located at a closer distance from the collector, the spot light beam (indicated by the solid line circle) reflected by the first target is incident into the first combined pixel 621; if a second target at this region is located a greater distance from the collector, the spot beam reflected by the second target (indicated by the dashed circle) is incident on the second pixel 622. In order to effectively suppress the influence of the pile _ up effect, the attenuation sheet 62 is disposed on the first pixel 621, so that the light beam reflected from the first target in the target region firstly hits the attenuation sheet 62, the light intensity of the reflected light beam is reduced after passing through the attenuation sheet 62, and then the reflected light beam enters the first pixel 621, thereby reducing the number of photons collected by the first pixel 621. In an embodiment of the present invention, the attenuation coefficient of the attenuation sheet may be determined according to a range of the distance measurement system, and the first combined pixel is configured to receive a photon signal formed after a photon in the pulsed light beam reflected by a target object at a short distance in the target area. The attenuation sheet not only solves strong ambient light, but also mainly weakens strong reflected light generated by a near target, because the pile _ up problem is mainly caused by the strong reflected light reflected by the target when the target is located at a near distance, and high reflectivity and strong ambient light are only auxiliary factors and are not dominant factors.

In one embodiment, the number of pixels included in the first combined pixel 621 and the second combined pixel 622 may not be the same. In one embodiment, the number of pixels included in the first and second

combined pixels

621 and 622 may be the same.

It can be understood that the number of combined pixels in the super-pixel is not limited to two, and for example, a third combined pixel may be further included, which is used to collect the pulse light beam reflected by the target at the intermediate distance, and by setting a plurality of combined pixels to collect the reflected light pulses in the sub-interval of the ranging range, no matter how many combined pixels are set, an attenuation sheet may be set on the combined pixel collecting the short-range to reduce the pile _ up effect.

By arranging the attenuation sheet on the first pixel for collecting the light beam reflected by the near target, the PDE of the pixel array can be regulated to be higher, the measurement accuracy of the far target is improved, and the pile _ up effect generated by the near target can be reduced.

Fifth embodiment

Fig. 11 is a schematic diagram of a collector according to a fifth embodiment of the invention. The collector 70 includes a receiving optical element 71, a filtering unit 72, a beam expanding optical element 73, and a pixel unit 74. Generally, when the emitter 11 emits a spot beam to the object to be measured, the receiving optical element 71 in the collector 70 will guide the spot beam to the corresponding pixel, and the pixel unit 74 is usually disposed on the focal plane of the receiving optical element 71. When the distance between the target to be measured and the pixel array is short, photons in the front part of the reflected beam are quickly incident into the pixel unit to saturate a plurality of pixels, and the probability that the subsequently incident photons are collected by the pixels is reduced, so that the position of a pulse peak value is advanced. Therefore, in the present embodiment, a beam expanding optical element 73 is disposed in the collector 70 to reduce the pile _ up phenomenon caused by a stronger light beam reflected back by a close-up first target.

In an embodiment, as shown in fig. 11, the receiving optical element 71 receives a first spot beam reflected from the target, where the first spot beam matches with one pixel 741 (in the present invention, a combined pixel or a super pixel), passes through the filtering unit 72, and then passes through the beam expanding optical element 73 to implement beam expansion, so as to form a second spot beam with a uniformly diffused beam and a larger spot diameter, and then the second spot beam is incident on a plurality of pixels 741 in the pixel unit 74, where each pixel 741 is configured to receive a portion of an optical signal in the second spot beam. The filter unit 72 is mainly used to filter out background light or stray light. The pixel cell 74 comprises a two-dimensional pixel array of a plurality of pixels 741. in one embodiment, the pixel cell 74 comprises a pixel array of single photon avalanche photodiodes (SPADs) that are responsive to incident single photons and output signals indicative of respective times of arrival of received photons at each SPAD. Also included in the pixel unit 74 is a microlens array, each microlens 742 in the microlens array being matched to a pixel 741 for converging a portion of the optical signal in the second spot beam onto the corresponding pixel 741.

In one embodiment, the receiving optics 71 comprise a first lens having a first focal length and the beam expanding optics 73 comprise a second lens having a second focal length, wherein the second focal length is greater than the first focal length. In one embodiment, the beam expanding optical element 73 is a beam expander lens for forming a second spot beam having a uniform intensity distribution and a larger spot diameter.

The readout circuit 75 includes a TDC circuit array and a histogram circuit 752, which is used to draw a histogram reflecting the pulse waveform emitted by the light source in the emitter, and further, the time of flight may also be calculated according to the histogram, and finally, the result is output. The TDC circuit array comprises a plurality of TDC circuits 751, each pixel 741 in the pixel unit 74 is configured to be connected with one TDC circuit 751 for receiving and calculating a time interval of the photon signal, and converting the time interval into a time code, the plurality of TDC circuits simultaneously calculate photons collected by the pixel in the second speckle beam, the time code output by the TDC circuit array is processed by a histogram circuit 752, a histogram reflecting a waveform of a pulse emitted by a light source in the emitter is drawn, further, a time of flight from emission to reception of the first speckle beam can be calculated according to the histogram, and finally, a result is output.

In one embodiment, when the transmitter and the collector are configured as a distance measurement system in a coaxial scenario, pixels 741 are configured as a pair of pixels (with the specific arrangement described above), each pair configured to couple to a TDC circuit.

In one embodiment, when the emitter and collector are configured as a distance measurement system for the off-axis case, pixels 741 are configured as superpixels (the specific setup is as described above), each superpixel configured to connect to one TDC circuit.

It can be understood that the beam expanding optical element is arranged to expand the first spot light beam to form a second spot light beam with a larger diameter and uniform light intensity to be incident on the plurality of pixels, and for the situation that the first spot light beam is reflected by a first target closer to the collector, the beam expanding provides buffering receiving time for collecting photons by the pixels, and even if the front photons in the reflected light beam are incident into the pixel array more quickly, the effective photons can be collected by the plurality of pixels at the same time, so that an accurate pulse peak value is obtained in the histogram, and a correct distance value is calculated.

As shown in fig. 12, as another embodiment of the present invention, a method for manufacturing a collector is further provided, which includes the following steps:

providing a receiving optical element for receiving the first spot beam reflected back by the target; the first spot light beam is matched with one pixel of the pixel unit;

providing a beam expanding optical element, wherein the beam expanding optical element is used for receiving the first spot light beam and forming a second spot light beam with uniformly diffused light beams and larger spot diameter;

providing a pixel unit comprising a two-dimensional pixel array consisting of a plurality of pixels for receiving the second spot beam, the second spot beam being matched to the plurality of pixels.

In some embodiments, the pixels are co-pixels, each comprising at least two SPADs; alternatively, the pixels are super pixels.

In some embodiments, the method further comprises the steps of: a microlens array is provided, the microlens array including a plurality of microlenses, each microlens for focusing a portion of the optical signal onto a corresponding pixel.

In some embodiments, the receiving optical element comprises a first lens having a first focal length, and the beam expanding optical element comprises a second lens having a second focal length; wherein the second focal length is larger than the first focal length.

An embodiment of the present application further provides a control apparatus, including a processor and a storage medium for storing a computer program; wherein a processor is adapted to perform at least the method as described above when executing the computer program.

Embodiments of the present application also provide a storage medium for storing a computer program, which when executed performs at least the method described above.

Embodiments of the present application further provide a processor, where the processor executes a computer program to perform at least the method described above.

The storage medium may be implemented by any type of volatile or non-volatile storage device, or combination thereof. Among them, the nonvolatile Memory may be a Read Only Memory (ROM), a Programmable Read Only Memory (PROM), an erasable Programmable Read-Only Memory (EPROM), an electrically erasable Programmable Read-Only Memory (EEPROM), a magnetic random Access Memory (FRAM), a Flash Memory (Flash Memory), a magnetic surface Memory, an optical Disc, or a Compact Disc Read-Only Memory (CD-ROM); the magnetic surface storage may be disk storage or tape storage. Volatile Memory can be Random Access Memory (RAM), which acts as external cache Memory. By way of illustration and not limitation, many forms of RAM are available, such as Static Random Access Memory (SRAM), Synchronous Static Random Access Memory (SSRAM), Dynamic Random Access Memory (DRAM), Synchronous Dynamic Random Access Memory (SDRAM), Double data rate Synchronous Dynamic Random Access Memory (DDRSDRAM, Double DataRateSync Synchronous Random Access Memory), Enhanced Synchronous Dynamic Random Access Memory (ESDRAM, Enhanced Synchronous Dynamic Random Access Memory), Synchronous link Dynamic Random Access Memory (SLDRAM, Synchronous Dynamic Random Access Memory (SLDRAM), Direct Memory (DRMBER, Random Access Memory). The storage media described in connection with the embodiments of the invention are intended to comprise, without being limited to, these and any other suitable types of memory.

In the several embodiments provided in the present application, it should be understood that the disclosed system and method may be implemented in other ways. The above-described device embodiments are merely illustrative, for example, the division of the unit is only a logical functional division, and there may be other division ways in actual implementation, such as: multiple units or components may be combined, or may be integrated into another system, or some features may be omitted, or not implemented. In addition, the coupling, direct coupling or communication connection between the components shown or discussed may be through some interfaces, and the indirect coupling or communication connection between the devices or units may be electrical, mechanical or other forms.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, that is, may be located in one place, or may be distributed on a plurality of network units; some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, all the functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may be separately regarded as one unit, or two or more units may be integrated into one unit; the integrated unit can be realized in a form of hardware, or in a form of hardware plus a software functional unit.

Those of ordinary skill in the art will understand that: all or part of the steps for implementing the method embodiments may be implemented by hardware related to program instructions, and the program may be stored in a computer readable storage medium, and when executed, the program performs the steps including the method embodiments; and the aforementioned storage medium includes: a mobile storage device, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.

Alternatively, the integrated unit of the present invention may be stored in a computer-readable storage medium if it is implemented in the form of a software functional module and sold or used as a separate product. Based on such understanding, the technical solutions of the embodiments of the present invention may be essentially implemented or a part contributing to the prior art may be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the methods described in the embodiments of the present invention. And the aforementioned storage medium includes: a removable storage device, a ROM, a RAM, a magnetic or optical disk, or various other media that can store program code.

The methods disclosed in the several method embodiments provided in the present application may be combined arbitrarily without conflict to obtain new method embodiments.

Features disclosed in several of the product embodiments provided in the present application may be combined in any combination to yield new product embodiments without conflict.

The features disclosed in the several method or apparatus embodiments provided in the present application may be combined arbitrarily, without conflict, to arrive at new method embodiments or apparatus embodiments.

The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several equivalent substitutions or obvious modifications can be made without departing from the spirit of the invention, and all the properties or uses are considered to be within the scope of the invention.

Claims

1. A distance measuring method, characterized by comprising:

t1: controlling the transmitter to emit a pulsed light beam;

2. The distance measurement method according to claim 1, wherein the second detection efficiency of the imaging pixel array is regulated to be lower or higher than the first detection efficiency.

3. The distance measuring method according to claim 1, further comprising, before step T3:

presetting a threshold value of the number of reference photons received by the reference pixel array within the predetermined time.

4. The distance measuring method according to claim 3,

when the number of the reference photons received by the reference pixel array is smaller than the threshold value within a preset time, controlling the second detection efficiency of the collector to be larger than the first detection efficiency;

and when the number of the reference photons received by the reference pixel array in a preset time is larger than or equal to the threshold value, controlling the second detection efficiency of the collector to be equal to the first detection efficiency.

5. The distance measuring method according to claim 1, further comprising, before step T3:

predefining a correspondence of the number of reference photons received by the reference pixel array within the predetermined time to a detection efficiency of the imaging pixel.

6. The distance measuring method according to claim 5,

and regulating and controlling the detection efficiency of the imaging pixel in real time according to the corresponding relation between the number of the reference photons received by the reference pixel array within the preset time and the reference photon number, and determining the second detection efficiency.

7. A distance measuring system, comprising:

a transmitter for transmitting a pulsed light beam to a target area;

a collector including a pixel array composed of a plurality of pixels; the pixel array comprises a reference pixel array and an imaging pixel array; the reference pixel array comprises at least one reference pixel for receiving reference photons; the imaging pixel array comprises at least one imaging pixel for receiving photons in the pulsed light beam reflected back through a target area to form a first photon signal;

control and processing circuitry, connected to the transmitter and the collector, for implementing the method of any of claims 1-6.

8. The distance measurement system of claim 7 wherein said reference photons comprise ambient photons.

9. The distance measurement system of claim 7 wherein said reference pixel array is configured as at least one column or row of reference pixels disposed along a peripheral edge of said imaging pixel array.

10. A computer-readable storage medium, in which a computer program is stored which, when being executed by a processor, carries out the steps of the method according to any one of claims 1 to 6.