CN213903798U

CN213903798U - Distance measuring system with dual light-emitting modes

Info

Publication number: CN213903798U
Application number: CN202021305076.2U
Authority: CN
Inventors: 王兆民
Original assignee: Orbbec Inc
Current assignee: Orbbec Inc
Priority date: 2020-07-04
Filing date: 2020-07-04
Publication date: 2021-08-06
Anticipated expiration: 2030-07-04

Abstract

The utility model discloses a distance measurement system with dual light emitting mode, include: a transmitter configured to emit a flood beam or a spot beam towards a target area, having a flood beam emitting mode and a spot beam emitting mode; the method comprises the following steps of (1) adopting a spot light beam emitting mode during long-distance measurement and adopting a flood light beam emitting mode during short-distance measurement; a collector configured to collect photons in the flood beam or the spot beam reflected back by the target and generate a photon signal; and the control and processing circuit is connected with the emitter and the collector and is used for calculating the flight time of the light beam from emission to reflection to reception according to the photon signals. By configuring the transmitter to have a dual transmission mode, the problems of resolution and precision of the distance measurement system can be effectively solved, so that the resolution and the precision are both considered, and the distance measurement system combining high precision and high resolution is obtained.

Description

Distance measuring system with dual light-emitting modes

Technical Field

The utility model relates to an optics range finding technical field especially relates to a distance measurement system with dual light emitting mode.

Background

A distance measurement may be performed on a target using a Time of Flight (TOF) principle to obtain a depth image including a depth value of the target, and a distance measurement system based on the Time of Flight principle has been widely used in the fields of consumer electronics, unmanned driving, AR/VR, and the like. A distance measuring system based on the time-of-flight principle generally includes a transmitter and a collector, the transmitter is used to transmit a pulse beam to illuminate a target field of view and the collector is used to collect a reflected beam reflected back through the target field of view, and the time required for the beam to be received from transmission to reflection is calculated to calculate the distance of an object.

At present, a collector in a laser radar (LiDAR) based on a flight time principle is mainly based on a single photon avalanche photodiode (SPAD) array, an emitter emits a dot matrix light beam to a target field of view in a scanning mode, the collector acquires photons by using the SPAD array and obtains the flight time from emission to reception of the photons through photon counting, and some technologies also provide the emitter with an array light source, and the emitter can emit the array light beam to the target field of view simultaneously. The depth measurement of an object is carried out through a plurality of independent light beams by scanning or array light source illumination, and the depth measurement device has the advantages of concentrated power, long measurement range and high signal-to-noise ratio; the disadvantage is that the resolution is low, and the method is difficult to be applied to some application scenes with high requirements on resolution.

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 with dual light emitting mode to solve at least one kind of problem in 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 measuring system having a dual light emitting mode, comprising:

a transmitter configured to emit a flood beam or a spot beam towards a target area, having a flood beam emitting mode and a spot beam emitting mode; the method comprises the following steps of (1) adopting a spot light beam emitting mode during long-distance measurement and adopting a flood light beam emitting mode during short-distance measurement;

a collector configured to collect photons in the flood beam or the spot beam reflected back by the target and generate a photon signal;

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

In some embodiments, the emitter comprises a first array of light sources and a second array of light sources; wherein the first array of light sources is adapted to emit a flood beam of light towards a target area and the second array of light sources is adapted to emit a spot beam of light towards the target area.

In some embodiments, the emitter comprises an array of light sources and liquid crystal; the light source array comprises a plurality of sub light sources, and the liquid crystal has two modes of a transparent state and a diffusion state.

In some embodiments, the control and processing circuitry is for controlling timing of emission of the emitted flood beam pattern and the emitted spot beam pattern.

In some embodiments, the first array of light sources and the second array of light sources are disposed on the same substrate, or on different substrates, the timing of the emission of the pulsed light beams by the first array of light sources and the second array of light sources being controlled by the control and processing circuitry.

In some embodiments, the pulsed light beam emitted by the light source array emits a flood light beam towards the target area after passing through the liquid crystal in the dispersed state.

In some embodiments, the pulsed light beam emitted by the light source array emits a spot light beam toward the target area after passing through the liquid crystal in the transparent state.

In some embodiments, the collector comprises a pixel unit and a receiving optical element; the receiving optical element is used for receiving at least part of the light beam reflected by the target and guiding the light beam to the corresponding pixel to form an imaging light spot; wherein the size of a single blob is set to correspond to a plurality of pixels.

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

the utility model discloses a configure the transmitter into having dual transmission mode, can effectively solve the resolution ratio of distance measurement system and the problem of precision, can compromise resolution ratio and precision to obtain the distance measurement system that high accuracy and high resolution combine.

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 with dual light emitting modes according to an embodiment of the present invention.

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

Fig. 3 is a schematic diagram of a pixel unit of a collector of a distance measuring system having dual light emitting modes 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 with dual light emitting modes 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, the emitter 11 is used to emit a light beam 30 to a target area 50, the light beam is emitted to a target object in a target area space to illuminate the target object in the space, at least a part of the emitted light beam 30 is reflected by the target area 50 to form a reflected light beam 40, at least a part of the reflected light beam 40 is received by the collector 12, the control and processing circuit 13 is respectively connected with the emitter 11 and the collector 12, the trigger signals of the emitter 11 and the collector 12 are synchronized to calculate the time required by the light beam from emission to reception, i.e. the flight time t between the emitted light beam 30 and the reflected light beam 40, and further, the distance D of the corresponding point on the target object can be calculated by:

D＝c·t/2 (1)

where c is the speed of light.

The transmitter 11 includes a light source 111, a transmitting optical element 112, a driver 113, and the like. The light source 111 may be a Light Emitting Diode (LED), a Laser Diode (LD), an Edge Emitting Laser (EEL), a Vertical Cavity Surface Emitting Laser (VCSEL), or the like, or may be a one-dimensional or two-dimensional light source array composed of a plurality of light sources; preferably, the light source array is a VCSEL array light source chip formed by generating a plurality of VCSEL light sources on a single semiconductor substrate, and the arrangement of the light sources in the light source array may be regular or irregular. The light beam emitted by the light source 111 may be visible light, infrared light, ultraviolet light, or the like. The light source 111 emits a light beam outward under the control of the driver 113.

In one embodiment, the light source 111 emits a pulsed light beam outward under the control of the driver 113 at a frequency (pulse period) that can be used in Direct time of flight (Direct TOF) measurements, the frequency being set according to the measurement distance. It will be appreciated that the light beam emitted by the light source 111 may also be controlled by means of a part of the control and processing circuit 13 or a sub-circuit present independently of the control and processing circuit 13.

The emission optical element 112 receives the light beam emitted from the light source 111 and shapes the light beam to project the light beam to a target area. 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, where receiving optical element 123 is used to receive at least part of the light beam reflected by the target and guide the light beam onto pixel unit 121, and filter unit 122 is used to filter out background light or stray light. The pixel unit 121 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 can respond 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).

Generally, a readout circuit (not shown) including one or more of a signal amplifier, a time-to-digital converter (TDC), a digital-to-analog converter (ADC), and the like is further connected to the pixel unit 121. The readout circuitry may be integrated with the pixels or may be part of the control and processing circuitry 13, which for ease of description is collectively considered part of the control and processing circuitry 13.

And the control and processing circuit 13 synchronizes the trigger signals of the emitter 11 and the collector 12, processes the photon signals of the pixel collected light beams, and calculates the distance information of the target to be measured based on the flight time of the reflected light beams. In one embodiment, the SPAD outputs a photon signal in response to an incident single photon, and the control and processing circuitry 13 receives the photon signal and performs signal processing to obtain the time of flight of the beam. In particular, the control and processing circuit 13 calculates the number of photons collected to form successive time bins, which are joined together to form a statistical histogram for reproducing the time series of the reflected beam, identifying the time of flight of the reflected beam from emission to reception by peak matching and filtering detection. 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 in one embodiment of the invention. Wherein the light sources are configured as a light source array 21 consisting of a plurality of sub-light sources 211 arranged on a monolithic substrate, the sub-light sources being arranged in a pattern on the substrate. The substrate may be a semiconductor substrate, a metal substrate, or the like, and the sub-light sources may be light emitting diodes, edge emitting laser emitters, vertical cavity surface laser emitters (VCSELs), or the like. The sub-light sources are used to emit light beams of any desired wavelength, such as visible light, infrared light, ultraviolet light, and the like. The array of light sources 21 is illuminated in groups or in its entirety under the control of a driver circuit, which may be part of the control and processing circuit 13, as will be appreciated. The control and processing circuit 13 controls each sub-light source 211 to emit a pulsed light beam with a time interval, wherein the time interval may be in a time-coded pattern. The arrangement of the sub light sources can be one-dimensional arrangement or two-dimensional arrangement, and can be regular arrangement or irregular arrangement.

In one embodiment, the emitter 11 comprises a first array of light sources for emitting a flood beam of light towards the target area and a second array of light sources for emitting a spot beam of light towards the target area. The first light source array and the second light source array may be disposed on the same substrate or on different substrates, and the control and processing circuit 13 controls the timing at which the first light source array and the second light source array emit the pulsed light beams.

In one embodiment, the emitter 11 comprises an array of light sources, preferably an array VCSEL chip consisting of a plurality of VCSEL sub-light sources, and a liquid crystal. The liquid crystal has two modes of a transparent state and a diffusive state, and is in the transparent state mode when the liquid crystal is on and in the diffusive state mode when the liquid crystal is off. The pulse light beam emitted by the light source array passes through the liquid crystal in the diffusion state and then emits a floodlight beam towards a target area; the pulsed light beam emitted by the light source array passes through the liquid crystal in a transparent state and then emits a spot light beam toward a target area.

Fig. 3 is a schematic diagram of a pixel cell according to an embodiment of the invention. The pixel unit 121 includes a pixel array 22 and a readout circuit 23, wherein the pixel array 22 includes a two-dimensional array of a plurality of pixels for collecting at least a portion of the light beam reflected back by the object and generating a corresponding photon signal, and the readout circuit 23 is configured to process the photon signal to calculate the time of flight. In one embodiment, the pixel array 22 is a SPAD array comprised of a plurality of SPADs.

In one embodiment, readout circuit 23 includes a TDC circuit 231 for processing the photon signals to form a single photon count string and a histogram circuit 232; the histogram circuit draws a histogram based on the single photon counting string; determining the position of a pulse peak in the histogram; and determining the flight time according to the pulse peak position, and finally outputting the result. The readout circuit 23 may be an array readout circuit composed of a single TDC circuit and a histogram circuit, or composed of a plurality of TDC circuit units and histogram circuit units.

In one embodiment, when emitter 11 emits a pulsed light beam to the object to be measured, optical element 112 in collector 12 directs the light beam to a corresponding pixel to form an imaging spot, and generally, a single spot is sized to correspond to a plurality of pixels, so that more photon signals in the reflected light beam can be received, it should be noted that here, the correspondence is understood to be imaging, and receiving optical element 112 generally includes an imaging lens. As shown in fig. 2 and 3, a single spot corresponds to 2 × 2 to 4 pixels, that is, photons in each reflected light beam are received by the corresponding 4 pixels with a certain probability, generally, a pixel region composed of a plurality of corresponding pixels is referred to as a "combined pixel", the size of the combined pixel needs to be considered comprehensively by a distance measurement system when setting, and the number of the combined pixels in the pixel array determines the resolution of the acquisition field.

Generally, the distance measuring system can be divided into coaxial and off-axis according to different arrangement modes between the emitter 11 and the collector 12. In an embodiment, when the emitter and the collector are configured in an off-axis manner, in order to solve the offset caused by parallax, a super-pixel technology is generally used to solve the problem (the detailed description of the super-pixel technology may specifically refer to the relevant content in chinese patent application No. CN 201910888951.X, which is not described herein again), that is, a pixel region (referred to as "super-pixel") formed by a plurality of pixels exceeding the number of pixels in a combined pixel is set to receive photons in a light beam reflected back by a target, so that the combined pixels corresponding to light beams reflected back by objects at different distances in a measurement range all fall into the super-pixel region.

In some embodiments, the combined pixels share one TDC circuit unit, that is, one TDC circuit unit is connected to each pixel in the combined pixels, and when any one pixel in the combined pixels receives a photon and generates a photon signal, the TDC circuit unit can calculate the flight time corresponding to the photon signal. In some embodiments, the super pixels share one TDC circuit unit, i.e. are connected by one TDC circuit unit with each of the super pixels.

It will be appreciated that the emitter 11 emits a pulsed light beam in a dual emission mode, the particular emission mode being regulated by the control and processing circuitry 13. In one embodiment, the emitter 11 is configured to adopt a mode of emitting a spot beam for distance measurement and a mode of emitting a flood beam for close measurement. The control and processing circuit 13 makes a judgment according to the intensity of the photon signal output by the collector to control the emission time sequence of the two modes, for example, when the distance measurement system is started, the floodlight beam is emitted by default, if the control and processing circuit 13 does not find the peak position in the histogram when determining the peak position according to the histogram, the intensity of the photon signal output by the collector is too low, and the emitter 11 is regulated and controlled to emit the spot beam. In other embodiments, the distance measurement system may be set to default to emitting a spot beam when activated.

In one embodiment, during the distance measurement, the control and processing circuit 13 obtains a first depth image of a frame of target area according to the reflected light beam when the transmitter 11 is in the flood light beam emitting mode, obtains a second depth image of the frame of target area when the transmitter is in the spot light beam emitting mode, and fuses the first depth image and the second depth image into a frame of depth image to obtain a third depth image of the target area, wherein the first depth image has the characteristics of high resolution and low precision, and the second depth image has the characteristics of low resolution and high precision, so that the fused third depth image has the characteristics of high resolution and high precision. The fusion process is to use the second TOF value in the second depth image to correct the first TOF value in the first depth image (the correction method can refer to the related content in chinese patent application No. CN201911306106.3, which is not described in detail herein), i.e., to establish mapping between the first depth image and the second depth image, assign the second TOF value in the second depth image as a reliable point to a corresponding pixel position of the first depth image, and use the reliable points to correct the first TOF value in the first depth image.

It can be understood that, by configuring the transmitter to have a dual transmission mode, the problems of resolution and precision of the distance measurement system can be effectively solved, so as to give consideration to both resolution and precision, and obtain a distance measurement system combining high precision and high resolution.

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 having a dual light emitting mode, comprising:

2. The distance measuring system having a dual light emitting mode according to claim 1, wherein: the emitter comprises a first array of light sources and a second array of light sources; wherein the first array of light sources is adapted to emit a flood beam of light towards a target area and the second array of light sources is adapted to emit a spot beam of light towards the target area.

3. The distance measuring system having a dual light emitting mode according to claim 1, wherein: the emitter comprises an array of light sources and liquid crystal; the light source array comprises a plurality of sub light sources, and the liquid crystal has two modes of a transparent state and a diffusion state.

4. The distance measuring system having a dual light emitting mode according to claim 1, wherein: the control and processing circuitry is for controlling the timing of the emission of the emitted flood beam pattern and the emitted spot beam pattern.

5. The distance measuring system having a dual light emitting mode according to claim 2, wherein: the first light source array and the second light source array are arranged on the same substrate or different substrates, and the timing sequence of the pulse light beams emitted by the first light source array and the second light source array is controlled by the control and processing circuit.

6. The distance measuring system having a dual light emitting mode according to claim 3, wherein: the pulse light beam emitted by the light source array emits a floodlight beam towards a target area after passing through the liquid crystal in a diffusion state.

7. The distance measuring system having a dual light emitting mode according to claim 3, wherein: the pulsed light beam emitted by the light source array passes through the transparent liquid crystal and then emits a spot light beam towards the target area.

8. The distance measuring system having a dual light emitting mode according to claim 1, wherein: the collector comprises a pixel unit and a receiving optical element; the receiving optical element is used for receiving at least part of the light beam reflected by the target and guiding the light beam to the corresponding pixel to form an imaging light spot; wherein the size of a single blob is set to correspond to a plurality of pixels.