CN111796295B

CN111796295B - Collector, manufacturing method of collector and distance measuring system

Info

Publication number: CN111796295B
Application number: CN202010500293.5A
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: 2023-12-12
Anticipated expiration: 2040-06-04
Also published as: CN111796295A

Abstract

The invention provides a collector, a manufacturing method of the collector and a distance measuring system, wherein the collector comprises the following components: a receiving optical element for receiving the first spot beam reflected back by the target; the first spot beam is matched with one pixel of the pixel unit; 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 beam and larger spot diameter; and the pixel unit comprises a two-dimensional pixel array formed by a plurality of pixels and is used for receiving the second spot light beam, and the second spot light beam is matched with the plurality of pixels. The correct distance value is calculated by setting the beam expanding optical element, and the pipe_up effect is eliminated.

Description

Collector, manufacturing method of collector and distance measuring system

Technical Field

The invention relates to the technical field of distance measurement, in particular to a collector, a manufacturing method of the collector and a distance measurement system.

Background

Distance measurement of objects can be performed using the Time of Flight (TOF) principle to acquire depth images containing depth values of the objects, and distance measurement systems based on the Time of Flight principle have been widely used in the fields of consumer electronics, unmanned driving, AR/VR, and the like. Distance measurement systems based on the time-of-flight principle typically include an emitter and a collector, with the emitter emitting a pulsed light beam to illuminate the field of view of the target and the collector collecting a reflected light beam, calculating the time required for the light beam to travel from emission to receipt of the reflection to calculate the distance of the object.

Currently, in a distance measurement system based on the time-of-flight principle, the transmitter includes a pixel array, especially a pixel array including a single photon avalanche photodiode (SPAD), when one photon in the emitted light beam is incident on the SPAD, an avalanche event output signal can be triggered to record the time for the photon to reach the SPAD, and based on this, the time required for the light beam to be emitted to be received is calculated. However, since SPAD needs to wait for a dead time (dead time) after receiving a photon and then receive the next photon, at most, only one photon can be received for a plurality of photons in the dead time. In the case of an object that is closer, an object with high reflectivity, or strong ambient light, a large number of photons are incident into the SPAD at an earlier time to saturate it, so that the SPAD cannot detect the photons incident later, resulting in abnormal pulse waveforms drawn in the histogram circuit, and the reception time of the optical pulse cannot be determined, thereby making it difficult to determine the distance of the target object.

The foregoing background is only for the purpose of facilitating an understanding of the principles and concepts of the application and is not necessarily in the prior art to the present application and is not intended to be used as an admission that such background is not entitled to antedate such novelty and creativity by virtue of prior application or that it is already disclosed at the date of filing of this application.

Disclosure of Invention

The invention provides a collector, a manufacturing method of the collector and a distance measuring system for solving the existing problems.

In order to solve the problems, the technical scheme adopted by the invention is as follows:

a collector, comprising: a receiving optical element, a beam expanding optical element, and a pixel unit; the receiving optical element is used for receiving the first spot light beam reflected by the target; the first spot beam is matched with one pixel of the pixel unit; 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 beam and larger spot diameter; the pixel unit comprises a two-dimensional pixel array formed by a plurality of pixels and is used for receiving the second spot light beam, and the second spot light beam is matched with the plurality of pixels.

In one embodiment of the present invention, the pixel is a composite pixel, and the two-dimensional pixel array includes a plurality of the composite pixels; or, the combined pixel is a super pixel, and the two-dimensional pixel array comprises a plurality of super pixels; each of the combined pixels or the superpixels is configured to receive a portion of the optical signal in the second speckle beam.

In one embodiment of the present invention, the pixel unit further includes a microlens array, and each microlens in the microlens array is matched with the pixel, and is used for converging a part of the optical signals in the second speckle light beam to the corresponding pixel.

In yet another embodiment of the present invention, the receiving optical element comprises a first lens having a first focal length and the expanding optical element comprises a second lens having a second focal length, wherein the second focal length is greater than the first focal length. The beam expanding optical element is a beam expander and is used for forming the second spot light beam with uniform intensity distribution and larger spot diameter. The two-dimensional pixel array is connected with the readout circuit, and the readout circuit is used for drawing a histogram reflecting the pulse waveform emitted by the light source in the emitter, and comprises a TDC circuit array and a histogram circuit.

In yet another embodiment of the present invention, a filtering unit is further included, and the filtering unit is disposed between the receiving optical element and the beam expanding optical element, and is used for filtering out the background light or the stray light.

The invention also provides a manufacturing method of the collector, which comprises the following steps: providing a receiving optical element for receiving a first spot beam reflected back by the target; the first spot 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 beam and larger spot diameter; providing a pixel unit, wherein the pixel unit comprises a two-dimensional pixel array formed by a plurality of pixels and is used for receiving the second spot light beam, and the second spot light beam is matched with the plurality of pixels.

The invention further provides a distance measuring system, a transmitter for transmitting a pulse beam to a target area; a collector as claimed in any preceding claim for receiving a photon signal formed by photons in the pulsed light beam reflected back through the target area; the control and processing circuit is connected with the transmitter and the collector and comprises a TDC circuit array and a histogram circuit; the TDC circuit array comprises a plurality of TDC circuits, wherein each TDC circuit is connected with each pixel for receiving and calculating the time interval of the photon signals and converting the time interval into a time code; the histogram circuit counts according to the time code output by the TDC circuit array to draw a histogram; a time of flight of the first spot beam from emission to reception is calculated from the histogram.

In one embodiment of the invention, the pixels are co-pixels when the emitter is arranged coaxially with the collector; the pixels are super-pixels when the emitters are disposed off-axis from the collector.

The beneficial effects of the invention are as follows: the collector comprises a first beam spot which is reflected by a target, a second beam spot which is provided by a beam expansion optical element and forms a beam which is uniformly diffused and has a larger spot diameter, a plurality of pixels of a pixel unit are used for receiving, buffering receiving time is provided for collecting photons by the pixels, the pixels can collect effective photons at the same time, so that an accurate pulse peak value is obtained in a histogram, a correct distance value is calculated, and the pile_up effect is eliminated.

Drawings

In order to more clearly illustrate the embodiments of the invention or the technical solutions of the prior art, the drawings which are used in the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the description below are only some embodiments of the invention, and that other drawings can be obtained according to these drawings without inventive faculty for a person skilled in the art.

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 a transmitter in an embodiment of the present invention.

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

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

Fig. 4 is a schematic diagram of a first distance measurement 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 invention.

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

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

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

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

Fig. 10 is a schematic diagram of a pixel unit in a further collector according to an embodiment of the invention.

Fig. 11 is a schematic structural view of a further collector according to an embodiment of the present invention.

Fig. 12 is a schematic diagram of a method for manufacturing a collector according to an embodiment of the invention.

Detailed Description

In order to make the technical problems, technical schemes and beneficial effects to be solved by the embodiments of the present invention more clear, 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 for purposes of illustration only and are not intended to limit the scope of the invention.

It will be understood that when an element is referred to as being "mounted" 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 both the fixing action and the circuit communication action.

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 merely for convenience in describing embodiments of the invention and to simplify the description, and do not denote or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus are not to be construed as limiting the invention.

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

Avalanche photodiodes refer to photosensitive elements used in laser communication. After 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 photocurrent. Increasing the reverse bias voltage causes an "avalanche" (i.e., a doubling of the photocurrent) phenomenon, and such a diode is referred to as an "avalanche photodiode".

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

D＝c·t/2 (1)

Wherein c is the speed of light.

The emitter 11 includes a light source 111, an emitting 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 outwards under the control of the driver 113. In one embodiment, the light source 111 emits a pulsed light beam outwards at a frequency (pulse period) under control of the driver 113, which may be used in Direct time of flight (Direct TOF) measurements, the frequency being set in dependence of the measurement distance. It will be appreciated that a portion of the control and processing circuitry 13 or sub-circuitry present independently of the control and processing circuitry 13 may also be used to control the light source 111 to emit a light beam.

The emission optical element 112 receives the light beam emitted from the light source 111 and projects the shaped light beam onto a target area. In one embodiment, the transmitting optical element 112 receives the pulsed light beam from the light source 111 and optically modulates the pulsed light beam, such as diffracting, refracting, reflecting, etc., 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 emission optical element 112 may be one or more combinations of forms of lenses, liquid crystal elements, diffractive optical elements, microlens arrays, metasurface (Metasurface) optical elements, masks, mirrors, MEMS mirrors, and the like.

Collector 12 includes a pixel unit 121, a filter unit 122, and a receiving optical element 123, where receiving optical element 123 is configured to receive at least a portion of the light beam reflected by the target and direct the light beam onto pixel unit 121, and filter unit 122 is configured to filter out background light or stray light. The pixel cell 121 includes a two-dimensional array of pixels, and in one embodiment, the pixel cell 121 includes a single photon avalanche photodiode (SPAD) that can be responsive to an incident single photon and output a signal indicative of the respective arrival time of the received photon at each SPAD, with the collection of weak light signals and calculation of time of flight being accomplished using, for example, time dependent single photon counting (TCSPC).

The control and processing circuit 13 synchronizes trigger signals of the emitter 11 and the collector 12, processes photon signals of the pixel collecting light beams, and calculates distance information of the object to be measured based on 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 collected photons to form successive time bins which are concatenated together to form a statistical histogram for reproducing the time series of reflected beams, and peak matching and filtering detection is used to identify the time of flight of the reflected beam from emission to reception. In some embodiments, the control and processing circuit 13 includes a readout circuit (not shown) that is comprised of one or more of a signal amplifier, a time-to-digital converter (TDC), a digital-to-analog converter (ADC), and the like. These circuits may be integrated with the pixels or may be part of the control and processing circuit 13, and for ease of description, are collectively referred to as part of the control and processing circuit 13. It will be appreciated that the control and processing circuitry 13 may be a separate dedicated circuit, 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 that is used to control the firing time, firing frequency, etc. of the light beam emitted by the light source 111.

In some embodiments, the distance measurement system 10 may further include color cameras, infrared cameras, IMUs, etc., and combinations of these devices may enable more rich functionality such as 3D texture modeling, infrared face recognition, SLAM, etc.

In some embodiments, the emitter 11 and the collector 12 may also be arranged coaxially, i.e. by means of optics with reflection and transmission functions, such as a half mirror or the like.

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

The pixel unit 121 comprises a pixel array 22, wherein the pixel array 22 comprises a two-dimensional array of a plurality of pixels for collecting at least part of the light beam reflected by the object and generating a corresponding photon signal, and a readout circuit 23 for processing 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 for drawing a histogram reflecting the pulse waveform emitted by the light source in the emitter, and further, the time of flight may be calculated according to the histogram, and the result is finally outputted. The readout circuit 23 may be a single TDC circuit and histogram circuit, or may be an array readout circuit including a plurality of TDC circuit units and histogram circuit units.

In one embodiment, the pixel array 22 is a pixel array made up of a plurality of SPADs, and when the emitter 11 emits a spot beam onto the object under test, the receiving optics 123 in the collector 12 direct the spot beam onto the corresponding pixels, typically, to receive as much of the photon signal in the reflected beam as possible, the size of the single spot is typically set to correspond to a plurality of pixels (the correspondence here can be understood as imaging, and the optics 112 typically include an imaging lens). For example, as shown in fig. 2 (b), a single spot corresponds to 2×2=4 pixels, that is, photons reflected by the spot beam will be received by the corresponding 4 pixels with a certain probability, and generally, a pixel area formed by a plurality of corresponding pixels is called as a "combined pixel", and the size of the combined pixel needs to be comprehensively considered according to a ranging system during setting. In one embodiment, each light source in the array of light sources 21 is configured to be paired with each co-pixel in the array of pixels 22, i.e., the projected field of view of each light source corresponds one-to-one with the acquisition field of view of the corresponding co-pixel. As shown in fig. 2 (b), the light beam emitted from the light source 211 is reflected by the object and then is directed to the pixel 221 by the receiving optical element 123, the light beam emitted from the light source 212 is reflected by the object and then is directed to the pixel 224 by the receiving optical element 123, and the light beam emitted from the light source 213 is reflected by the object and then is directed to the pixel 225 by the receiving optical element 123.

In general, the distance measuring systems between the emitter 11 and the collector 12 can be divided into on-axis and off-axis according to the arrangement. For the coaxial situation, the light beam emitted by the emitter 11 is collected by the corresponding combined pixel in the collector 12 after being reflected by the measured object, and the position of the combined pixel is not influenced by the distance of the measured object; however, in the case of off-axis, because of parallax, when the measured object is far and near, the position of the light spot on the pixel unit will also change, and will generally shift along the direction of the base line (the line between the emitter 11 and the collector 12 is used to represent the direction of the base line in the present invention), and when the distance of the measured object is unknown, the position of the combined pixel is uncertain, so that in order to solve this problem, a super-pixel technology, that is, a plurality of pixels exceeding the corresponding number of the combined pixels are set to form a pixel area, which is called a "super-pixel" herein, for receiving the reflected spot light beam, and one super-pixel 222 includes three combined pixels in the embodiment shown in fig. 2 (b). When the size of the superpixel 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 total pixels corresponding to the spots reflected by the object at different distances in the measurement range can fall into the superpixel area, i.e. the size of the superpixel should exceed at least one total pixel. Generally, the super-pixel is the same size as the composite pixel along the direction perpendicular to the base line, and is larger than the composite pixel along the base line direction. The number of superpixels is typically the same as the number of spot beams acquired by a single measurement by the collector 12.

The histogram circuit 232 plots a received waveform reflecting the pulse waveform emitted by the light source in the emitter, typically a received waveform substantially similar in shape to the emitted pulse waveform, the received waveform representing the number of photons in the reflected pulse incident into the pixel array. The photons received by the pixel array include ambient photons that persist over a time bin of the histogram and signal photons that appear to form a pulse peak only within the corresponding time bin of the target location. However, since the SPAD array does not detect photons after receiving photons, when the object to be measured is closer to the SPAD array or the object to be measured has high reflectivity, photons in front of the reflected beam are more rapidly incident into the SPAD array to saturate a plurality of SPADs, and the probability of subsequently incident photons being collected by the SPADs is reduced, resulting in advance pulse peak positions. Or under the strong ambient light condition, 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, so that the formed received waveform is distorted, and TOF values determined by using the wave peaks of the distorted received waveform are inaccurate. The above-generated cases of received waveform distortion are collectively referred to as the pile_up phenomenon, and the improvement of accuracy of the distance measurement system if this problem is solved will be described below by some embodiments.

First embodiment

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

s1, controlling the emitter to emit a pulse beam towards a target area.

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

S2, the pixel array of the regulation collector has at least two different detection efficiencies, photon signals formed by photons in the light beam reflected by the target area are received respectively with the at least two different detection efficiencies, and depth images of the target area are obtained respectively according to the photon signals;

the control and processing circuitry 13 alters the detection efficiency (PDE) of the pixel array by modulating the reverse bias voltage applied across each pixel in the pixel array 22. Where PDE refers to the ratio of the number of detected photons to the total number of incident photons per unit time, PDE for 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 higher PDE, the lower the reverse bias voltage applied to the pixel, the lower PDE, and when the reverse bias voltage is below the breakdown voltage, avalanche quenching occurs, and the pixel no longer receives photons. 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 set reasonably according to the system requirements in practical application.

In the invention, photon signals formed by photons in light beams reflected by an object to be detected in different distance ranges are respectively obtained by controlling the pixel array of the collector to have at least two different detection efficiencies, the different detection efficiencies correspond to the ranging ranges, the reflectivities and the like of different ranging systems, namely, the ranging range with low detection efficiency is smaller, and the pixel array is used for processing near-distance, high-reflectivity and strong ambient light; the range of the range finding with high detection efficiency is far, and the long-distance, low-reflectivity and low-environment light are processed. In practice, the number of detection efficiencies may be set according to the specific circumstances. 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 objects to be detected in the target area.

In one 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 area, and the difference between the plurality of detection efficiencies may be equal or unequal.

In one embodiment of the present 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 a light beam reflected by an object to be measured in the target area with 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 regulates the pixel array 22 to have the first detection efficiency (when the reverse bias voltage applied to the pixels is lower), that is, the pixel array 22 has a lower PDE. At this time, the first frame depth image acquisition of the target field of view is completed. Photons in the light beam reflected from 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 higher reflectivity first target are received by pixels in the pixel array 22 to form a first photon signal. Even in stronger ambient light, since the pixel has a lower PDE at this point, the effect of ambient photons can be reduced and signal photons in the effectively reflected beam received form a first photon signal. The control and processing circuit 13 calculates a first flight time according to the first photon signal so as to obtain a first depth image of the target area, wherein a pixel point of the first depth image has a first TOF value.

It will be appreciated that by reducing the PDE of the pixel array 22, the problem of pile_up is effectively solved, the accuracy of measuring near objects is improved, but reducing the PDE of the pixel array, and correspondingly reducing the range of the ranging system, it is difficult for the pixel array 22 to collect a sufficient number of useful photons for a second object farther from the collector or a second object having a lower reflectivity, and it is not possible to generate a second photon signal having a sufficient signal to noise ratio, and it is not possible to calculate a second time of flight that characterizes the distance information of the second object. The next step is thus taken to determine a second time of flight for the second target.

Then, the pixel array in the regulation collector has 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 the pixel array 22 to have a second detection efficiency (the reverse bias voltage applied to the pixels is higher at this time, the second detection efficiency is higher than the first detection efficiency, at this time, the pixel array 22 has a higher PDE to complete the second frame depth image acquisition of the target area, photons in the light beam reflected by a second target farther from the acquirer 12 can be received by 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 pixels in the pixel array 22 to form a second photon signal, the control and processing circuit 13 calculates a second depth image of the target area according to the second photon signal, 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 a target located at a furthest distance from the system, and in one embodiment of the invention, the maximum detection distance from the detection system is 150m, and the second detection efficiency can receive photons reflected back when the target is located at 150m to form a photon signal; whereas the first detection efficiency can only receive photons reflected back from the target at 20 m.

In addition, when the pixel array has a higher PDE, photons in the beam reflected by the first object may also be received to generate a third photon signal, and the control and processing circuit 13 may calculate a third time of flight characterizing the distance information of the first object according to the third photon signal, which results in a third TOF value on a part of the pixels in the second depth image, but the third TOF value on the same pixel is smaller than the first TOF value (accurate TOF value) due to the presence of the pixel_up phenomenon. Thus, an accurate depth image of the target area is determined in the next step.

It will be appreciated that the same applies to the present invention when the first detection efficiency is greater than the second detection efficiency. I.e. the control and processing circuit 13 regulates 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 regulated pixel array then has a second detection efficiency (when the reverse bias voltage applied to the pixels is lower), i.e., 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.

S3, fusing the depth images of the target areas to obtain fused depth images of the target areas.

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

Specifically, as described above, the control and processing circuit 13 assigns the first TOF value at each pixel point in the first depth image to the third TOF value at the corresponding pixel point in the second depth image to replace the first TOF value at the pixel point, thereby forming a third depth image, where the corresponding TOF value at each pixel point in the third depth image is the accurate time of flight. It is understood that pixels referred to herein primarily refer to pixels having an effective TOF value.

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

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, by adjusting and controlling at least two different detection efficiencies of the pixel array of the collector, photon signals formed by photons in the light beam reflected by the target area are received respectively with the at least two different detection efficiencies, and depth images of the target area are obtained respectively according to the photon signals, and the depth images are fused into one frame of depth image, so that measurement errors caused by pipe_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 value of the target to be detected in the depth image corresponding to the high efficiency and the low efficiency in the at least two different detection efficiencies is selected according to the distance between the target to be detected, the fused depth image is obtained, and the tile_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 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 by the object and generating a corresponding photon signal, and the readout circuit 41 is adapted to process the photon signal for calculating the time of flight.

In one embodiment, the readout circuit 44 includes a TDC circuit 441 and a histogram circuit 442 for drawing a histogram reflecting the pulse waveform emitted by the light source in the emitter, and further, the time of flight may be calculated according to the histogram, and the result is finally outputted. The readout circuit 44 may be a single TDC circuit and 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 41 is a pixel array comprised of a plurality of single photon avalanche photodiodes (SPADs), wherein 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, reference pixel array 42 is configured as a column of reference pixels disposed along a peripheral edge of imaging pixel array 43, and in other embodiments reference pixel array 42 may be disposed in at least one column or row; alternatively, the reference pixels are located at any given position around the imaging pixel array 43. The configuration of the imaging pixel array 43 is as described for the pixel array shown in fig. 2 (b), and a description thereof will not be repeated here.

The control and processing circuit 13 controls the emitter 11 to emit a pulsed light beam towards the target area, while controlling the pixels in the collector to be turned on to receive photons in the reflected light beam, the reflected light beam reflected back through the target area being directed by the receiving optical element 123 to be imaged to the imaging pixel array 43, the imaging pixels in the imaging pixel array 43 collecting photons in the reflected light beam to form a photon signal, the control and processing circuit 13 calculating the time of flight of the reflected light beam from emission to reception based on the photon signal. However, due to the existence of the pile_up phenomenon, errors may exist in the calculated reflected light beam, so by configuring the reference pixel array 42, the number of received reference photons in a certain period of time is counted, and the PDE of the imaging pixels in the imaging pixel array 43 at the next frame acquisition is regulated according to the number of reference photons. The control and processing circuitry 13 alters the detection efficiency (PDE) of the imaging pixel array by modulating the reverse bias voltages applied across the imaging pixels in the imaging pixel array 43.

Wherein the reference photons received by the reference pixel array 42 during the predetermined time period comprise ambient photons and possibly signal photons in the partially reflected beam, and the reference photon number is used to characterize the product of the ambient light intensity and the target reflectivity, the reference photon number 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 in the preset time, and the collector is controlled to receive photons with the adjusted detection efficiency until the imaging pixel array receives photons in the pulse beam reflected by the target area to form a second photon signal, so that the preset requirement is met. The predetermined requirement here may be to meet a predetermined accuracy or the like, the number of times being adjusted at least once.

In one embodiment of the invention, the detection efficiency of the array of imaging pixels is regulated to be lower or higher than the first detection efficiency, and specifically, the detection efficiency is regulated according to the inverse proportion relation between the reference photon number and the PDE of the imaging pixels.

In one embodiment, the threshold for the number of reference photons received by the reference pixel array 42 during a certain period of time is preset, for example, the certain period of time is set to 10us, and 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 controls the reference pixel array 42 to receive reference photons, if the number of reference photons received during the next frame acquisition is smaller than the threshold when the number of reference photons is lower than the threshold when the ambient light is lower and/or the target reflectivity is lower, 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) when the number of reference photons is greater than the threshold, and the imaging pixel array still has the first detection efficiency during the next frame acquisition. By setting a threshold for the number of reference photons, the number of PDEs adjusting the imaging pixel is reduced, reducing the complexity of the system at the time of adjustment.

In one embodiment, the correspondence between the number of reference photons received by the reference pixel array 42 in a predetermined time and PDE of the imaging pixel may be predefined, and the control and processing circuit 13 may determine 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 in combination with the predefined correspondence, so that real-time regulation may be implemented. In practical applications, the distance measurement system usually encounters many uncontrollable factors, such as LiDAR systems used in automatic driving, environmental changes or target changes may occur in the continuous measurement process, the PDE of the imaging pixels can be regulated in real time to effectively solve the ranging errors caused by the occurrence of the conditions, the accuracy of the system is improved, and 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, there is also proposed a distance measuring method including the steps of:

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

t2: controlling the collector to have a first detection efficiency and to receive photons at the first detection efficiency; the pixel array of the collector comprises a reference pixel array and an imaging pixel array; the reference pixel array includes at least one reference pixel for receiving reference photons; the imaging pixel array comprises at least one imaging pixel, and the imaging pixel is used for receiving photons in the pulse light beam reflected by the 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 the target area to form a second photon signal to meet preset requirements;

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

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

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

In one embodiment, a correspondence table of the number of reference photons and the detection efficiency of the imaging pixels 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 reference photon number (ambient 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.

Further, by presetting the threshold value of the number of reference photons received by the reference pixel array in a predetermined time, the number of times of adjusting the detection efficiency of the imaging pixels is reduced, and the complexity during adjustment is reduced.

Still further, by predefining a correspondence between the number of reference photons received by the reference pixel array within a predetermined time and the detection efficiency of the imaging pixels, the accuracy of the adjustment is improved.

Third embodiment

Fig. 8 is a schematic diagram of a distance measuring system according to a third embodiment of the present invention. The distance measurement system 60 comprises a transmitter 11, a collector 12, a camera 14 and a control and processing circuit 13. Wherein the emitter 11 is configured to emit a light beam 30 to the target area 20, the light beam is emitted to the target area space to illuminate a target object in the space, at least a portion of the emitted light beam 30 is reflected by the target area 20 to form a reflected light beam 40, at least a portion of the reflected light beam 40 is received by the collector 12, and the control and processing circuit 13 is respectively connected to the emitter 11 and the collector 12, and synchronizes trigger signals of the emitter 11 and the collector 12 to calculate a time required for the light beam from the emission to the reception. On the other hand, the control and processing circuit 13 is connected to a camera 14, the camera 14 being arranged to acquire a gray-scale image of the target area, wherein the gray-scale values of the pixels in the gray-scale image represent the total light intensity of the light beam 50 and the ambient light reflected by the target. The control and processing circuit 13 regulates the detection efficiency (PDE) of the corresponding pixel in the pixel array in the collector 12 according to the gray value of the pixel point in the gray image.

Specifically, the camera 14 includes a first pixel unit 141 for acquiring a gray image of the target area, where the first pixel unit 141 includes a first pixel array (not shown) including a plurality of first pixels, and pixel points in the gray image are in one-to-one correspondence with the first pixels in the first pixel unit 141. The camera 14 may be a grayscale camera, an RGB camera, or the like, preferably a grayscale camera. The collector 12 comprises a second pixel unit 121, and in one embodiment, the second pixel unit 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, the pixel array 22 is denoted as a second pixel array, and the second pixel array includes a two-dimensional array formed by a plurality of second pixels, preferably, the second pixels are SPAD pixels. The camera 14 and collector 12 are configured to have the same field of view for collection such that at least one first pixel is paired with at least one second pixel (in this embodiment, the second pixel may be a co-pixel or a super-pixel).

The control and processing circuit 13 determines the light intensity of the reflected light beam based on the gray value of each pixel in the gray image, the gray value being divided into 256 levels altogether between 0 and 255, the larger the gray value, the larger the light intensity of the reflected light beam corresponding. It will be appreciated that the light beam reflected by a first target located closer to the collector will have a greater intensity than the light beam reflected by a second target located farther from the collector; alternatively, the light intensity of the light beam reflected by the first target with higher reflectivity is greater than the light beam reflected by the second target with lower reflectivity; or the reflected ambient light can correspondingly increase the gray value of the pixel point in the gray image under the influence of stronger ambient light.

In order to effectively reduce the influence of the pixel_up phenomenon, the control and processing circuit 13 adjusts the PDE of the corresponding 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 pixel by varying the reverse bias voltage applied across the second pixel in the second pixel array. In general, during the next frame depth map acquisition, the control and processing circuit 13 regulates and controls the PDE of each second pixel in the second pixel array, and at this time, the second pixel array no longer has a uniform PDE, so that the accuracy of measurement is effectively improved when a plurality of different targets to be measured are located in the target area.

In one embodiment, a correspondence table of gray values of the gray image and numerical values of detection efficiency of the second pixels is stored in advance. The control and processing circuit 13 determines the PDE of the second pixel corresponding to the gray value lookup table according to the gray value lookup table of each pixel point in the gray image, and regulates the reverse bias voltage applied to the second pixel to change the PDE of the second pixel in the next frame acquisition. The corresponding relation table of the gray value and the PDE value can be obtained through 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, gradation values are stepwise in the order of decreasing gradation values (or increasing gradation values) in advance, and each stepwise is configured to have a corresponding PDE. For example, the pixel can be divided into three steps, wherein the gray scale value range of the first step is 0-85, the gray scale value range of the second step is 86-171, the gray scale value range of the third step is 172-256, and the PDE of the corresponding second pixel is set as a first PDE (higher PDE), a second PDE (middle PDE) and a third PDE (lower PDE). The control and processing circuit 13 processes the gray-scale image according to gray-scale value steps to divide the image into a plurality of first closed-loop areas, and gray-scale values of all pixels in the same closed-loop area 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 regulated to have the first PDE. The time of regulation can be improved by such a step-setting zone regulation. It will be appreciated that the above regulation method is only one embodiment of the present invention, and the present invention is not limited in particular.

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

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

p2: controlling a first pixel array of a gray image acquisition unit to acquire a gray 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 pulse light beam reflected back by the target area at 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 photons in the pulse light beam reflected by the target area to form a second photon signal which meets the preset requirement;

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

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

It will be appreciated that in one embodiment of the 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, in the distance measurement method of the present embodiment, the distance measurement system of the third embodiment is used for performing distance measurement, and the technical solution is the same as that of the foregoing distance measurement system, so that a detailed description is not repeated here.

According to the distance measurement method and the distance measurement system, the detection efficiency of the second pixel of the collector is adjusted according to the gray value of the gray image, and the pixel_up phenomenon of received waveform distortion is eliminated under the condition that the frame rate in the measurement process is not reduced.

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

Still further, the time for lifting and controlling is adjusted by the hierarchical setting region by dividing the gray value into at least two steps in sequence in advance and configuring the detection efficiency of the second pixel corresponding to each step.

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 by the object and generating a corresponding photon signal, and the readout circuit 64 is for processing 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 drawing a histogram reflecting the pulse waveform emitted by the light source in the emitter, and further, the time of flight may be calculated from the histogram, and the result is finally outputted. The readout circuit 64 may be a single TDC circuit and histogram circuit, or may be an array readout circuit including 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 onto the corresponding pixels, and generally, in order to receive as many photon signals in the reflected beam as possible, the size of a single spot is generally set to correspond to a plurality of pixels (the correspondence may be understood as imaging, the optical element 123 generally includes an imaging lens), for example, a single spot corresponds to 2×2=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, and 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 in setting.

In a distance measurement system with an off-axis configuration between the emitter and the collector, because of parallax, when the measured object is far and near, the position of the light spot falling on the pixel unit will also change, and generally shift along the direction of the base line (the line between the emitter 11 and the collector 12 is used to represent the direction of the base line in the present invention), and when the distance between the measured object is unknown, the position of the combined pixel is uncertain, so that in order to solve this problem, a super-pixel technology, that is, a plurality of pixel component pixel areas 611 and 612 (referred to as "super-pixels" herein) exceeding the corresponding number of the combined pixels are set for receiving the reflected spot light beam) is required.

In one embodiment, as shown in fig. 10, the super pixel 611 is configured to include a first pixel 621, a second pixel 622, and the super pixel 611 is connected to a TDC circuit and a histogram circuit. Wherein, the collecting 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 the pulse light beam towards the corresponding area, if the first target at the area is located at a shorter distance from the collector, the spot light beam (represented by a solid line circle) reflected by the first target is incident into the first combined pixel 621; if the second target at this area is located at a greater distance from the collector, the spot beam (indicated by the dashed circle) reflected by the second target is incident into the second combined pixel 622. In order to effectively suppress the effect of the pipe_up effect, the attenuation sheet 62 is disposed on the first pixel 621, so that the light beam reflected from the first target at the target area firstly strikes the attenuation sheet 62, the light intensity of the reflected light beam after passing through the attenuation sheet 62 is reduced, and then the light beam is incident into the first pixel 621, so that the number of photons collected by the first pixel 621 is reduced. In one embodiment of the present invention, the attenuation coefficient of the attenuation sheet may be determined according to the ranging range of the distance measurement system, and the first pixel is used for receiving a photon signal formed after photons in the pulse beam reflected by a short-distance target object in the target area. The attenuation sheet not only solves the problem of strong ambient light, but also mainly attenuates the strong reflected light generated by a short-distance target, because the pipe_up problem is mainly caused by the strong reflected light reflected when the target is positioned in the short distance, and the high reflectivity and the strong ambient light are only auxiliary factors but not dominant factors.

In one embodiment, the number of pixels included in the first and second combined pixels 621 and 622 may be different. In one embodiment, the number of pixels included in the first and second combined pixels 621 and 622 may also be the same.

It is understood that the number of the combined pixels in the super-pixel is not limited to two, for example, the super-pixel may further include a third combined pixel, so as to collect the pulse beam reflected by the target at the middle distance, and by setting a plurality of combined pixels to collect the reflected light pulses in the subinterval of the ranging range respectively, no matter how many combined pixels are set, an attenuation pad may be set on the combined pixels collecting the near range so as to reduce the pipe_up effect.

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

Fifth embodiment

Fig. 11 is a schematic view of a collector according to a fifth embodiment of the invention. Collector 70 includes receiving optics 71, filtering unit 72, beam expanding optics 73, and pixel unit 74. Generally, when the emitter 11 emits a spot beam toward the object to be measured, the receiving optical element 71 in the collector 70 directs the spot beam onto the corresponding pixel, and then the pixel unit 74 is typically disposed at the focal plane of the receiving optical element 71. When the object to be measured is closer to the pixel array, photons in the front part of the reflected light beam are more quickly incident into the pixel unit to saturate a plurality of pixels, and the probability that the photons which are subsequently incident are collected by the pixels is reduced, so that the pulse peak position is advanced. Thus, in this embodiment beam expanding optics 73 are provided in collector 70 to reduce the pile_up phenomenon caused by the relatively strong light beam reflected back from the first object in close proximity.

In one embodiment, as shown in fig. 11, the receiving optical element 71 receives the first spot beam reflected from the target, where the first spot beam matches with one pixel 741 (in the present invention, a pixel may be a super pixel) on the pixel unit, and after passing through the filtering unit 72, the beam expansion is implemented by the beam expansion optical element 73, so as to form a second spot beam with uniformly diffused beam and larger spot diameter, and the second spot beam is incident on a plurality of pixels 741 in the pixel unit 74, where each pixel 741 is used to receive a part of the optical signal in the second spot beam. The filtering unit 72 is mainly used for filtering out background light or stray light. The pixel cell 74 comprises a two-dimensional array of pixels 741, and in one embodiment, the pixel cell 74 comprises an array of single photon avalanche photodiodes (SPADs) that can be responsive to an incident single photon and output a signal indicative of the respective arrival time of the received photon at each SPAD. The pixel unit 74 further includes a microlens array, where each microlens 742 in the microlens array is matched with the pixel 741, and is configured to converge a portion of the light signal in the second spot beam onto the corresponding pixel 741.

In one embodiment, the receiving optical element 71 comprises a first lens having a first focal length and the expanding optical element 73 comprises 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 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 for drawing a histogram reflecting the waveform of the pulses emitted by the light source in the emitter, and further, may calculate the time of flight from the histogram, and finally output the result. The TDC circuit array includes a plurality of TDC circuits 751, each pixel 741 in the pixel unit 74 is configured to be connected to one TDC circuit 751 for receiving and calculating a time interval of the photon signal, and converting the time interval into a time code, so that the plurality of TDC circuits simultaneously calculate photons collected by the pixel in the second spot beam, the time code output by the TDC circuit array is processed by the histogram circuit 752, a histogram reflecting the pulse waveform emitted by the light source in the emitter is drawn, further, the time of flight of the first spot beam from emission to reception can also be calculated according to the histogram, and finally the result is output.

In one embodiment, when the transmitter and collector are configured as a distance measurement system in a coaxial case, pixel 741 is configured as a composite pixel (specifically configured as described above), each composite pixel being configured to connect to one TDC circuit.

In one embodiment, when the emitter and collector are configured as distance measurement systems in an off-axis situation, the pixels 741 are configured as super-pixels (specifically configured as described above), each super-pixel being configured to connect to one TDC circuit.

It can be understood that, by arranging the beam expanding optical element to expand the first spot beam to form a second spot beam with larger diameter and uniform light intensity, the second spot beam is incident on the pixels, and for the situation that the first spot beam is reflected back by the first object closer to the collector, buffer receiving time is provided for collecting photons by the pixels through beam expansion, even if photons in front of the reflected beam are incident into the pixel array faster, effective photons can be collected by the pixels at the same time, so that accurate pulse peaks are obtained in the histogram, and correct distance values are calculated.

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

Providing a receiving optical element for receiving a first spot beam reflected back by the target; the first spot 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 beam and larger spot diameter;

providing a pixel unit, wherein the pixel unit comprises a two-dimensional pixel array formed by a plurality of pixels and is used for receiving the second spot light beam, and the second spot light beam is matched with the plurality of pixels.

In some embodiments, the pixels are composite pixels, each comprising at least two SPADs; alternatively, the pixel is a super pixel.

In some embodiments, the method further comprises the steps of: a microlens array is provided that includes a plurality of microlenses, each microlens for converging 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 expanding optical element comprises a second lens having a second focal length; wherein the second focal length is greater than the first focal length.

The embodiment of the application also provides a control device, which comprises a processor and a storage medium for storing a computer program; wherein the processor is adapted to perform at least the method as described above when executing said computer program.

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

The embodiments of the present application also provide a processor executing a computer program, at least performing the method as described above.

The storage medium may be implemented by any type of volatile or non-volatile storage device, or combination thereof. The nonvolatile Memory may be a Read Only Memory (ROM), a programmable Read Only Memory (PROM, programmable Read-Only Memory), an erasable programmable Read Only Memory (EPROM, erasableProgrammable Read-Only Memory), an electrically erasable programmable Read Only Memory (EEPROM, electricallyErasable Programmable Read-Only Memory), a magnetic random Access Memory (FRAM, ferromagneticRandom Access Memory), a Flash Memory (Flash Memory), a magnetic surface Memory, an optical disk, or a compact disk Read Only (CD-ROM, compact Disc Read-Only Memory); the magnetic surface memory may be a disk memory or a tape memory. The volatile memory may be random access memory (RAM, random Access Memory), which acts as external cache memory. By way of example, and not limitation, many forms of RAM are available, such as static random access memory (SRAM, static Random Access Memory), synchronous static random access memory (SSRAM, synchronousStatic Random Access Memory), dynamic random access memory (DRAM, dynamic Random AccessMemory), synchronous dynamic random access memory (SDRAM, synchronous Dynamic Random AccessMemory), double data rate synchronous dynamic random access memory (ddr SDRAM, double Data RateSynchronous Dynamic Random Access Memory), enhanced synchronous dynamic random access memory (ESDRAM, enhanced Synchronous Dynamic Random Access Memory), synchronous link dynamic random access memory (SLDRAM, syncLink Dynamic Random Access Memory), direct memory bus random access memory (DRRAM, direct Rambus Random Access Memory). The storage media described in embodiments of the present application are intended to comprise, without being limited to, these and any other suitable types of memory.

In the several embodiments provided by the present application, it should be understood that the disclosed systems and methods may be implemented in other ways. The above described device embodiments are only illustrative, e.g. the division of the units is only one logical function division, and there may be other divisions in practice, such as: multiple units or components may be combined or may be integrated into another system, or some features may be omitted, or not performed. In addition, the various components shown or discussed may be coupled or directly coupled or communicatively coupled to each other via some interface, whether indirectly coupled or communicatively coupled to devices or units, whether electrically, mechanically, or otherwise.

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

In addition, each functional unit in each embodiment of the present application may be integrated in one processing unit, or each unit may be separately used as one unit, or two or more units may be integrated in one unit; the integrated units may be implemented in hardware or in hardware plus software functional units.

Those of ordinary skill in the art will appreciate that: all or part of the steps for implementing the above method embodiments may be implemented by hardware associated with program instructions, where the foregoing program may be stored in a computer readable storage medium, and when executed, the program performs steps including the above method embodiments; and the aforementioned storage medium includes: a mobile storage device, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), a magnetic disk or an optical disk, or the like, which can store program codes.

Alternatively, the above-described integrated units of the present invention may be stored in a computer-readable storage medium if implemented in the form of software functional modules and sold or used as separate products. Based on such understanding, the technical solutions of the embodiments of the present invention may be embodied in essence or a part contributing to the prior art in the form of a software product stored in a storage medium, including several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) 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, ROM, RAM, magnetic or optical disk, or other medium capable of storing program code.

The methods disclosed in the method embodiments provided by the application can be arbitrarily combined under the condition of no conflict to obtain a new method embodiment.

The features disclosed in the several product embodiments provided by the application can be combined arbitrarily under the condition of no conflict to obtain new product embodiments.

The features disclosed in the embodiments of the method or the apparatus provided by the application can be arbitrarily combined without conflict to obtain new embodiments of the method or the apparatus.

The foregoing is a further detailed description of the application in connection with the preferred embodiments, and it is not intended that the application be limited to the specific embodiments described. It will be apparent to those skilled in the art that several equivalent substitutions and obvious modifications can be made without departing from the spirit of the application, and the same should be considered to be within the scope of the application.

Claims

1. A collector of a distance measurement system for receiving photon signals formed by photons in a pulsed light beam reflected back from a target during ranging, comprising: a receiving optical element, a beam expanding optical element, and a pixel unit;

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

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 beam and larger spot diameter;

the pixel unit comprises a two-dimensional pixel array formed by a plurality of pixels and is used for receiving the second spot light beam, and the second spot light beam is matched with the plurality of pixels; the pixel is a super pixel, the two-dimensional pixel array comprises a plurality of super pixels, the super pixel comprises a first combined pixel and a second combined pixel, a spot light beam reflected by a first target is incident into the first combined pixel, a spot light beam reflected by a second target farther from the collector is incident into the second combined pixel, and an attenuation sheet is arranged on the first combined pixel, so that the light beam reflected by the first target is incident into the first combined pixel after passing through the attenuation sheet.

2. The collector of claim 1 wherein the pixel unit further comprises an array of microlenses, each microlens in the array of microlenses being matched to the pixel for converging a portion of the light signal in the second speckle beam onto a corresponding pixel.

3. The collector of claim 1 wherein 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 greater than the first focal length.

4. The collector of claim 1 wherein the beam expanding optics are beam expanders for forming the second spot beam of uniform intensity distribution and larger spot diameter.

5. The collector of claim 1 wherein the two-dimensional array of pixels is coupled to a readout circuit for drawing a histogram reflecting the pulse shape emitted by the light source in the emitter, comprising a TDC circuit array and a histogram circuit.

6. The collector of any of claims 1-5 further comprising a filter unit disposed between the receiving optical element and the beam expanding optical element for filtering out background or stray light.

7. A method of manufacturing a collector for a distance measurement system, comprising the steps of:

providing a pixel unit, wherein the pixel unit comprises a two-dimensional pixel array formed by a plurality of pixels and is used for receiving the second spot light beam, and the second spot light beam is matched with the plurality of pixels; the pixel is a super pixel, the two-dimensional pixel array comprises a plurality of super pixels, the super pixel comprises a first combined pixel and a second combined pixel, a spot light beam reflected by a first target is incident into the first combined pixel, a spot light beam reflected by a second target farther from the collector is incident into the second combined pixel, and an attenuation sheet is arranged on the first combined pixel, so that the light beam reflected by the first target is incident into the first combined pixel after passing through the attenuation sheet.

8. A distance measuring system, characterized in that,

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

comprising a collector as claimed in any of claims 1-6 for receiving photon signals formed by photons in said pulsed light beam reflected back through said target area;

The control and processing circuit is connected with the transmitter and the collector and comprises a TDC circuit array and a histogram circuit;

the TDC circuit array comprises a plurality of TDC circuits, wherein each TDC circuit is connected with each connection and is used for receiving and calculating the time interval of the photon signals and converting the time interval into a time code;

the histogram circuit counts according to the time code output by the TDC circuit array to draw a histogram;

a time of flight of the first spot beam from emission to reception is calculated from the histogram.