CN212694039U

CN212694039U - Distance measuring system

Info

Publication number: CN212694039U
Application number: CN202020831853.0U
Authority: CN
Inventors: 李国花; 朱亮; 闫敏
Original assignee: Shenzhen Oradar Technology Co Ltd
Current assignee: Shenzhen Oradar Technology Co Ltd
Priority date: 2020-05-18
Filing date: 2020-05-18
Publication date: 2021-03-12
Anticipated expiration: 2030-05-18

Abstract

The utility model discloses a distance measurement system, include: a transmitter comprising a light source array composed of a plurality of light sources configured to transmit a pulsed light beam, the light source array comprising at least two sub-light source arrays; the collector comprises a pixel array consisting of a plurality of pixels, the pixel array comprises at least two sub-pixel arrays, and the sub-pixel arrays are configured to collect photons reflected by the target object by pulse beams emitted by the sub-light source arrays and form photon signals; the control and processing circuit is connected with the emitter and the collector and used for calculating the flight time of the pulse light beam from emission to collection according to the photon signals; wherein the control and processing circuitry is configured to activate only one sub-light source array to emit pulsed light beams during a measurement phase and to simultaneously activate more than a corresponding number of pixels in the corresponding sub-pixel array. The scanning of the target view field is realized under the condition that the scanning unit is not arranged by setting the light sources to be sequentially started, so that the anti-interference capability of the system is improved.

Description

Distance measuring system

Technical Field

The utility model relates to an optics range finding technical field especially relates to a distance measurement system.

Background

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

Current LIDAR based on the time-of-flight principle mainly includes mechanical LIDAR systems and solid-state LIDAR systems; the mechanical LIDAR system realizes distance measurement of a 360-degree large field of view by rotating the base, and the emitters of the mechanical LIDAR system are generally point light sources and line light sources, and have the characteristics of concentrated beam intensity and high precision, but the scanning time is longer, so that the frame rate is lower.

The solid-state LIDAR system does not comprise movable mechanical parts, the transmitter comprises a transmitter array which is used for transmitting an area light beam with a certain view field to a space at one time and receiving the area light beam through the area array receiver, so that the resolution and the frame rate are improved, but the area array receiver is used for collecting a reflected light beam of the whole view field during measurement, so that the solid-state LIDAR system is easily interfered by the outside, and the crosstalk of signals can be generated between adjacent pixels.

The above background disclosure is only for the purpose of assisting understanding of the inventive concepts and technical solutions 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 contents are disclosed at the filing date of the present patent application.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a distance measurement system to solve at least one among the above-mentioned background art problem.

In order to achieve the above object, the embodiment of the present invention provides a technical solution that:

a distance measurement system comprising:

a transmitter configured to transmit a pulsed light beam, the transmitter comprising an array of light sources consisting of a plurality of light sources, the array of light sources comprising at least two arrays of sub-light sources, each of the arrays of sub-light sources comprising at least one light source;

the collector comprises a pixel array consisting of a plurality of pixels, the pixel array comprises at least two sub-pixel arrays, each sub-pixel array comprises at least one pixel, and the sub-pixel arrays are configured to respectively collect photons, emitted by the sub-light source arrays, of the pulse light beams reflected by a target object to be measured and form photon signals;

the control and processing circuit is connected with the emitter and the collector and used for calculating the flight time of the pulse light beam from emission to collection according to the photon signals;

wherein the control and processing circuitry is configured to activate only one of the arrays of sub-light sources to emit the pulsed light beam during a measurement phase and to simultaneously activate more than a corresponding number of the pixels in the corresponding array of sub-pixels.

In some embodiments, the pixel array is configured to be disposed corresponding to the light source array, wherein there is no overlapping portion between the sub-light source arrays.

In some embodiments, each of the sub-light source arrays consists of one or more columns of light sources in the light source array; alternatively, each of the sub-light source arrays is composed of one or more rows of light sources in the light source array.

In some embodiments, each of the sub-pixel arrays consists of one or more columns of pixels in the pixel array; alternatively, each of the sub-pixel arrays is composed of one or more rows of pixels in the pixel array.

In some embodiments, at least two pixels of the array of sub-pixels are paired with one light source of the array of sub-light sources.

In some embodiments, said array of sub-light sources and said corresponding array of sub-pixels are activated sequentially or based on a pseudo-random sequence, each said array of sub-light sources being activated at least once during a field of view scan measurement.

In some embodiments, the light source array includes a first sub light source array and a second sub light source array, and the pixel array includes a first sub pixel array and a second sub pixel array corresponding to the light source array.

In some embodiments, a driving circuit is further included, and the light source groups in the light source array are controlled to emit light through the driving circuit.

In some embodiments, a readout circuit is included for processing the photon signals to calculate time of flight.

In some embodiments, the readout circuit includes a TDC circuit for receiving and calculating a time interval of the photon signal and converting the time interval into a time code; and the histogram circuit counts according to the time code output by the TDC circuit to draw a histogram.

The utility model discloses technical scheme's beneficial effect is:

the distance measuring system of the utility model realizes the scanning of the target view field under the condition of not setting the scanning unit by setting the light sources to be sequentially started, thereby improving the anti-interference capability of the system; and photons are collected by activating the super-pixels to achieve simultaneous measurements of objects at different distances.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, 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 inventive exercise.

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

Fig. 2 is a schematic diagram of a light source array of a distance measurement system according to an embodiment of the present invention.

Fig. 3 is a schematic diagram of a pixel unit in a collector of a distance measuring system according to an embodiment of the present invention.

Detailed Description

In order to make the technical problem, technical scheme and beneficial effect that the embodiment of the present invention will solve more clearly understand, the following combines the drawings and embodiment, and goes forward the further detailed description of the present invention. 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. The connection may be for fixation or for circuit connection.

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 the 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 and operated in a particular orientation, and are not to be construed as limiting the 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.

Fig. 1 is a schematic diagram of a distance measuring system according to an embodiment of the present invention, and the distance measuring system 10 includes a transmitter 11, a collector 12, and a control and processing circuit 13. Wherein, emitter 11 is used to emit light beam 300 to target area 200, the light beam is emitted to target area space to illuminate target object in the space, at least part of emitted light beam 300 forms reflected light beam 400 after being reflected by target area 200, at least part of reflected light beam 400 is received by collector 12; the control and processing circuit 13 is connected to the emitter 11 and the collector 12, respectively, and synchronizes the trigger signals of the emitter 11 and the collector 12 to calculate the time required for the light beam to be received from emitting to reflecting, i.e. the flight time t between the emitted light beam 300 and the reflected light beam 400, and 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.

Specifically, 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 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 element 112 may be in the form of one or more of a lens, a liquid crystal element, a diffractive optical element, a microlens array, a Metasurface (Metasurface) optical element, a mask, a mirror, a MEMS galvanometer, and the like.

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

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 object 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, identifying 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 is a schematic diagram of a light source array according to an embodiment of the present invention. The light source is configured as a light source array 20 composed of a plurality of light sources disposed on a single substrate (or a plurality of substrates), the light source array 20 may be one-dimensional or two-dimensional, may be regularly arranged or irregularly arranged, and is preferably an array VCSEL chip composed of a plurality of VCSEL light sources disposed on a semiconductor substrate. The light source array 20 may emit light beams of any wavelength, such as visible light, infrared light, ultraviolet light, and the like. The light source array 20 emits light under modulation driving of a driving circuit (which may be part of the control and processing circuit 13), such as continuous wave modulation, pulse modulation, etc., or the light source array 20 may emit light in groups under control of the driving circuit.

In the present invention, the light source array 20 is configured to include at least two sub-light source arrays without an overlapping portion between the sub-light source arrays. In some embodiments, the non-overlapping may be achieved by controlling the light source groups in the light source array 20 to emit light using the driving circuit. In one embodiment, each sub-light source array may also be disposed on a separate substrate, and the sub-light source arrays are controlled by different driving circuits to emit light in groups. In the description of the embodiments below, the drive circuit is uniformly provided as part of the control and processing circuit 13.

In one embodiment shown in fig. 2, the light source array 20 includes a first sub-light source array 210 and a second sub-light source array 220, each of which is composed of a row of light sources in the light source array 20, and in other embodiments, the sub-light source array is composed of a plurality of rows of light sources. In the case of distance measurement, the control and processing circuit 13 is configured to activate only one of the sub-light-source arrays for emitting pulsed light beams in each measurement phase, for example, in a first measurement phase, only the first sub-light-source array 210 is activated, and in a second measurement phase, only the second sub-light-source array 220 is activated; preferably, the second measurement phase follows the first measurement phase. It is understood that the light source array 20 may further include a third sub light source array, a fourth sub light source array, and the like. The plurality of sub-light source arrays in the light source array 20 are sequentially activated from left to right or from right to left until all the sub-light source arrays are activated, and the scanning of the whole target field of view is completed, wherein the light beam emitted by each sub-light source array can illuminate a local area of the target field of view.

Fig. 3 is a schematic diagram of a pixel unit in a collector according to an embodiment of the present invention. The pixel unit includes a pixel array 30 and a readout circuit 40; wherein the pixel array 30 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; the readout circuit 40 is used to process the photon signals to calculate the time of flight.

In one embodiment, the readout circuit 40 includes a TDC circuit 411 and a histogram circuit 412, 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 be calculated according to the histogram, and the result is finally outputted. The TDC circuit is used for receiving and calculating the time interval of the photon signal and converting the time interval into a time code; the histogram circuit counts according to the time code output by the TDC circuit to draw a histogram. The readout circuit 40 may be composed of 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, pixel array 30 is a pixel array composed of a plurality of SPADs, and when emitter 11 emits a spot beam toward a measured object, receiving optical element 112 in collector 12 directs the spot beam onto the corresponding pixel; generally, in order to receive as many photon signals in the reflected light beam as possible, a single spot is generally sized to correspond to a plurality of pixels (the correspondence here may be understood as imaging, and the optical element 112 generally includes an imaging lens), such as the single spot corresponding to 2 × 2 ═ 4 pixels 314 shown in fig. 3, that is, the photons reflected back by the spot light beam will be received by the corresponding 4 pixels with a certain probability, and the shaded boxes in fig. 3 represent the possible occurrence of the reflected light beam being incident on the corresponding pixels.

As shown in fig. 2 and 3, the pixel array 30 is configured to be disposed corresponding to the light source array 20, and includes at least two sub-pixel arrays, which are activated under the control of the control and processing circuit 13, respectively, for receiving photons reflected by the target field of view from the light beams emitted by the corresponding sub-light source arrays, wherein each sub-pixel array includes at least one pixel, and there is no overlapping portion between the sub-pixel arrays. It will be appreciated that in other embodiments, there may be some overlap between the sub-pixel arrays, which may reduce the size of the light source array or achieve a higher density of light source arrays.

For example, when the control and processing circuit 13 controls the first sub-light source array 210 to emit light, the corresponding first sub-pixel array 310 is synchronously activated; the light beams emitted by the light source 211 are reflected by the target field of view to form the imaging light spots 312, and the imaging light spots are received by the corresponding 4 sub-pixels, and when the 6 sub-light sources included in the first sub-light source array 210 emit light beams simultaneously, the imaging light spots are received by the 24 sub-pixels in the first sub-pixel array 310. When the control and processing circuit 13 controls the second sub-light source array to emit light, the corresponding second sub-pixel array 320 is synchronously controlled to be turned on. The control and processing circuit 13 controls the sub-light source array and the sub-pixel array to be sequentially activated from left to right or from right to left, and the scanning measurement of the target field of view is sequentially completed along the horizontal direction (baseline direction).

In one embodiment, each sub-light source array may also include one light source, and each corresponding sub-pixel array also includes at least one pixel, and preferably, at least two pixels in the sub-pixel array are paired with one light source in the sub-light source array, so as to implement the point-by-point scanning measurement of the target field of view.

In some embodiments, the activation of the sub-light source arrays and corresponding sub-pixel arrays at each measurement stage need not be a sequential movement from left to right or right to left, but may also be a non-sequential activation to reduce crosstalk, e.g., based on a pseudo-random sequence. During the whole measurement process, each sub-light source array is activated at least once during the field scanning measurement; preferably, each sub-light source array is activated once during the field scan measurement.

Generally, the distance measuring system can be divided into a coaxial system and an off-axis system according to different arrangement modes between the emitter and the collector. For the coaxial situation, the light beam emitted by the emitter is reflected by the measured object and then is collected by the corresponding pixel in the collector, and the position of the pixel cannot be influenced by the distance of the measured object. Taking the light source array shown in fig. 2 as an example, the light beams emitted by the sub-light source 211 form corresponding imaging light spots 310 in the sub-pixels, and the light beams emitted by the sub-light source 221 form corresponding imaging light spots 320 in the sub-pixels.

For the off-axis situation, 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 will also change, and will generally deviate along the direction of the base line (the connecting line between the emitter and the collector, in the embodiment of the present invention, the base line direction is uniformly represented by the horizontal line), and the position of the pixel is uncertain when the distance of the object to be measured is unknown; for example, the sub-light sources 213 in the corresponding first sub-light source array 210 are affected by parallax, and the reflected light beam forming imaging spot 313 does not fall in the first sub-pixel array 310, and to solve this problem, the control and processing circuit 13 is configured to, when one sub-light source array is activated to emit a pulse light beam, synchronously activate more than the corresponding number of pixels in the corresponding sub-pixel array, and mark the number of pixels in the sub-pixel array receiving each spot as a super-pixel. The size of the super-pixel needs to take into account both the measurement range of the system and the length of the base line when setting up (mainly the size in the direction along the base line) so that the light beams reflected back by objects at different distances within the measurement range are all incident within the area of the super-pixel.

In one embodiment, the super-pixel is arranged to: when the distance is at the lower limit of the measuring range, the reflected light beam at the short distance is incident to one side of the super pixel; when at the upper limit of the measurement range, the reflected beam falls on the other side of the super-pixel at a long distance. The situation of the close-up blind area can be effectively compensated by setting the super pixels. In one embodiment, shown in fig. 3, the control and processing circuit 13 synchronously activates the first, second and third

sub-light source arrays

310, 320, 330 when the first sub-light source array 210 emits light beams; wherein the super pixel 311 for collecting one light spot is set to a size of 2 × 6, and the control and processing circuit 13 synchronously activates the second, third and fourth sub

light source arrays

320, 330 and 340 when the second sub light source array 220 emits the light beam.

In one embodiment, the super-pixels share one TDC circuit, that is, one TDC circuit is connected to each pixel in the super-pixels, and when any one of the super-pixels receives a photon and generates a photon signal, the TDC circuit unit can calculate the flight time corresponding to the photon.

It is to be understood that the above description is intended to be illustrative, and not restrictive, of the invention. In some embodiments, as shown in fig. 2, each sub-light source array may also be composed of one or more rows of light sources in the light source array, and the corresponding sub-pixel array may also be composed of one or more rows of pixels in the pixel array. In performing the scanning, the control and processing unit 13 activates each sub-light source array and synchronously activates pixels larger than the number of pixels in the corresponding sub-pixel array, thereby realizing the scanning in the vertical direction. The specific implementation is the same as the above description, and repeated explanation is not provided.

It is to be understood that the foregoing is a more detailed description of the invention, and specific/preferred embodiments thereof are described, and it is not intended that the invention be limited to the specific embodiments disclosed. For those skilled in the art to which the invention pertains, a plurality of alternatives or modifications can be made to the described embodiments without departing from the concept of the invention, and these alternatives or modifications should be considered as belonging to the protection scope of the invention. In the description herein, references to the description of the term "one embodiment," "some embodiments," "preferred embodiments," "an example," "a specific example," or "some examples" or the like, mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention.

In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the scope of the invention as defined by the appended claims.

Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. One of ordinary skill in the art will readily appreciate that the above-disclosed, presently existing or later to be developed, processes, machines, manufacture, compositions of matter, means, methods, or steps, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

Claims

1. A distance measuring system, comprising:

2. The distance measuring system of claim 1 wherein: the pixel array is configured to be disposed corresponding to the light source array, wherein there is no overlapping portion between the sub light source arrays.

3. The distance measuring system of claim 2, wherein: each sub light source array consists of one or more columns of light sources in the light source array; alternatively, each of the sub-light source arrays is composed of one or more rows of light sources in the light source array.

4. The distance measuring system of claim 2, wherein: each sub-pixel array consists of one or more columns of pixels in the pixel array; alternatively, each of the sub-pixel arrays is composed of one or more rows of pixels in the pixel array.

5. The distance measuring system of claim 2, wherein: at least two pixels of the sub-pixel array are paired with one light source of the sub-light source array.

6. The distance measuring system of claim 1 wherein: the sub-light source arrays and the corresponding sub-pixel arrays are activated sequentially or based on a pseudo-random sequence, each of the sub-light source arrays being activated at least once during a field of view scan measurement.

7. The distance measuring system of claim 1 wherein: the light source array comprises a first sub light source array and a second sub light source array, and the pixel array comprises a first sub pixel array and a second sub pixel array corresponding to the light source array.

8. The distance measuring system of claim 2, wherein: the light source array also comprises a driving circuit, and the driving circuit is used for controlling the light sources in the light source array to emit light in groups.

9. The distance measuring system of claim 1 wherein: a readout circuit is included for processing the photon signals to calculate time of flight.

10. The distance measuring system of claim 9 wherein: the readout circuit includes a TDC circuit and a histogram circuit; the TDC circuit is used for receiving and calculating the time interval of the photon signal and converting the time interval into a time code; and the histogram circuit counts according to the time code output by the TDC circuit to draw a histogram.