CN111965659B - Distance measurement system, method and computer readable storage medium - Google Patents
Distance measurement system, method and computer readable storage medium Download PDFInfo
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- 238000005259 measurement Methods 0.000 title claims abstract description 68
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
- G01S17/08—Systems determining position data of a target for measuring distance only
- G01S17/10—Systems determining position data of a target for measuring distance only using transmission of interrupted, pulse-modulated waves
Abstract
The application is applicable to the technical field of time of flight, and provides a distance measurement system, a distance measurement method and a computer readable storage medium, wherein a pulse beam is emitted to a target through a transmitter; the collector comprises at least one pixel block and at least two diaphragms, each pixel block comprises at least two sub-pixel blocks which are sequentially arranged according to the ascending or descending order of the size, the size of each sub-pixel block is positively correlated with the measuring distance and is negatively correlated with the aperture of the diaphragm corresponding to the sub-pixel block, each diaphragm shapes the pulse beam reflected by the target in the ranging range of the sub-pixel block corresponding to the sub-pixel block, and each sub-pixel block collects photons in the pulse beam after being shaped by the diaphragm corresponding to the sub-pixel block and outputs photon signals; by having the control and processing circuitry calculate the time of flight of the pulsed light beam from the photon signals, accurate measurement of the distance between the different targets located at the at least two measurement distances and the distance measurement system can be achieved, effectively reducing measurement errors.
Description
Technical Field
The application belongs to the technical field of Time of flight (TOF), and particularly relates to a distance measurement system, a distance measurement method and a computer readable storage medium.
Background
The distance of the target may be measured using a time-of-flight technique, and a depth image including depth values of the target may be further acquired based on the distance of the target. Distance measurement systems based on time-of-flight technology have been widely used in the fields of consumer electronics, unmanned vehicles, virtual reality, augmented reality, etc. A distance measurement system based on time-of-flight technology generally comprises an emitter and a collector, with the emitter emitting a pulsed light beam to illuminate the target and with the collector receiving a pulsed light beam reflected by the target, the distance between the target and the distance measurement system being calculated by calculating the time the pulsed light beam was emitted to be received. The distance measuring system can be divided into a coaxial system and an off-axis system according to the arrangement of the emitter and the collector. For a coaxial system, pulse light beams emitted by the emitter are collected by corresponding pixels in the collector after being reflected by the target, and the distance of the target cannot influence the accuracy of a measurement result; for off-axis systems, the position at which the pulsed light beam reflected by the long-distance and short-distance targets falls on the collector may vary due to the parallax, resulting in errors in the measurement results.
Disclosure of Invention
In view of the above, the embodiments of the present application provide a distance measurement system, a distance measurement method, and a computer readable storage medium, so as to solve the problem that the accuracy of the measurement result of the existing off-axis distance measurement system is affected by the distance of the target and errors occur.
A first aspect of an embodiment of the present application provides a distance measurement system, including:
a transmitter for transmitting a pulsed light beam toward a target;
the collector comprises at least one pixel block and at least two diaphragms, wherein each pixel block comprises at least two sub-pixel blocks which are sequentially arranged according to the ascending or descending order of the size, one sub-pixel block corresponds to one diaphragm, the size and the measurement distance of each sub-pixel block are positively correlated and negatively correlated with the aperture of the corresponding diaphragm, each diaphragm is used for shaping a pulse beam reflected by a target in the ranging range of the corresponding sub-pixel block, and each sub-pixel block is used for collecting photons in the pulse beam after being shaped by the corresponding diaphragm and outputting photon signals;
and the control and processing circuit is respectively connected with the emitter and the collector and is used for calculating the flight time of the pulse light beam according to the photon signals.
In one embodiment, the collector further includes at least one attenuation sheet, each attenuation sheet corresponds to a sub-pixel block with a measured distance smaller than a distance threshold, and each attenuation sheet is used for attenuating the light intensity of the pulse light beam incident to its corresponding sub-pixel.
In one embodiment, the collector further comprises an imaging lens for imaging and focusing the pulsed light beam reflected by the target before the pulsed light beam reflected by the target is incident on the diaphragm.
In one embodiment, the collector further comprises at least two first focusing lenses, each corresponding to one sub-pixel block, each for focusing the pulse beam after shaping via the aperture to its corresponding sub-pixel block.
In an embodiment, the collector further comprises a filtering unit for filtering out background light and stray light incident on the at least one pixel block.
In one embodiment, an aperture distance between two diaphragms corresponding to any two adjacent sub-pixel blocks in each pixel block is equal to a parallax corresponding to a lower limit value of a ranging range of the distance measuring system.
In one embodiment, the control and processing circuit includes a number of TDC circuits equal to the number of all the sub-pixel blocks, each of the TDC circuits being connected to one of the sub-pixel blocks, a time width of each of the TDC circuits being positively correlated with a measured distance of the sub-pixel block to which it is connected, and a time resolution of each of the TDC circuits being negatively correlated with the measured distance of the sub-pixel block to which it is connected.
In one embodiment, the emitter comprises at least two light source columns which are sequentially offset by a first distance in a preset direction, each light source column comprises at least two light sources which are sequentially arranged in the preset direction, and the distance between two adjacent light sources in each light source column in the preset direction is greater than or equal to a second distance;
the collector comprises at least two pixel columns which are sequentially offset by a first distance in a preset direction, each pixel column comprises at least two pixel blocks which are sequentially arranged in the preset direction, and the distance between two adjacent pixel blocks in each pixel column in the preset direction is larger than or equal to a second distance;
wherein the preset direction is a vertical direction when the distance measurement system is placed on a horizontal plane, the first distance is greater than or equal to the diameter of the light source, and the second distance is greater than or equal to the product of the total number of light source columns included by the emitter and the first distance.
A second aspect of an embodiment of the present application provides a distance measurement method, including:
controlling the transmitter to transmit a pulsed light beam to the target;
each sub-pixel block of the collector is controlled to collect photons in the pulse light beam after being shaped by the corresponding diaphragm and output photon signals, the collector comprises at least one pixel block and at least two diaphragms, each pixel block comprises at least two sub-pixel blocks which are sequentially arranged in the order of increasing or decreasing size, one sub-pixel block corresponds to one diaphragm, the size of each sub-pixel block is positively correlated with the measuring distance and is negatively correlated with the aperture of the corresponding diaphragm, and each diaphragm is used for shaping the pulse light beam reflected by a target in the ranging range of the corresponding sub-pixel block;
and calculating the flight time of the pulse light beam according to the photon signal.
A third aspect of the embodiments of the present application provides a computer-readable storage medium storing a computer program which, when executed by a processor, implements the steps of the distance measurement method according to the second aspect of the embodiments of the present application.
In the distance measurement system provided by the first aspect of the embodiment of the application, a pulse light beam is emitted to a target through an emitter; the collector comprises at least one pixel block and at least two diaphragms, wherein each pixel block comprises at least two sub-pixel blocks which are sequentially arranged according to the ascending or descending order of the size, one sub-pixel block corresponds to one diaphragm, the size and the measuring distance of each sub-pixel block are positively correlated and negatively correlated with the aperture of the corresponding diaphragm, each diaphragm is used for shaping a pulse beam reflected by a target in the ranging range of the corresponding sub-pixel block, and each sub-pixel block is used for collecting photons in the pulse beam after being shaped by the corresponding diaphragm and outputting photon signals; by connecting the control and processing circuit with the emitter and the collector, respectively, and calculating the time of flight of the pulsed light beam based on the photon signals, accurate measurement of the distance between different targets located at least two measurement distances and the distance measurement system can be achieved, effectively reducing measurement errors.
It will be appreciated that the advantages of the second and third aspects may be referred to in the description of the first aspect, and will not be described in detail herein.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments or the description of the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a first configuration of a distance measurement system according to an embodiment of the present application;
fig. 2 is a schematic diagram of a first structure of a pixel block according to an embodiment of the present application;
FIG. 3 is a schematic diagram of a collector according to an embodiment of the present application;
FIG. 4 is a schematic diagram of a control and processing circuit provided by an embodiment of the present application;
FIG. 5 is a schematic diagram of a second structure of a pixel block according to an embodiment of the present application;
fig. 6 is a schematic diagram of a third structure of a pixel block according to an embodiment of the present application;
fig. 7 is a schematic diagram of a second configuration of a distance measurement system according to an embodiment of the present application.
Detailed Description
In the following description, for purposes of explanation and not limitation, specific details are set forth such as the particular system architecture, techniques, etc., in order to provide a thorough understanding of the embodiments of the present application. It will be apparent, however, to one skilled in the art that the present application may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present application with unnecessary detail.
It should be understood that the terms "comprises" and/or "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or arrays, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, arrays, and/or groups thereof.
Furthermore, the terms "first," "second," "third," and the like in the description of the present specification and in the appended claims, are used for distinguishing between descriptions and not necessarily for indicating or implying a relative importance.
Reference in the specification to "one embodiment" or "some embodiments" or the like means that a particular feature, structure, or characteristic described in connection with the embodiment is included in one or more embodiments of the application. Thus, appearances of the phrases "in one embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but mean "one or more, but not all embodiments" unless expressly specified otherwise. The term "including" and variations thereof mean "including but not limited to" unless otherwise specifically emphasized.
As shown in fig. 1, an embodiment of the present application provides a distance measurement system 100, including:
an emitter 1 for emitting a pulsed light beam 300 towards a target 200;
the collector 2 comprises at least one pixel block and at least two diaphragms, wherein each pixel block comprises at least two sub-pixel blocks which are sequentially arranged according to the ascending or descending order of the size, one sub-pixel block corresponds to one diaphragm, the size and the measurement distance of each sub-pixel block are positively correlated and negatively correlated with the aperture of the corresponding diaphragm, each diaphragm is used for shaping a pulse beam 400 reflected by a target 200 in the ranging range of the corresponding sub-pixel block, and each sub-pixel block is used for collecting photons in the pulse beam 400 after being shaped by the corresponding diaphragm and outputting photon signals;
and the control and processing circuit 3 is respectively connected with the emitter 1 and the collector 2, and the control and processing circuit 3 is used for calculating the flight time of the pulse beam according to the photon signals.
As shown in fig. 2, a schematic diagram of the structure of one pixel block 20 is exemplarily shown; the pixel block 21 includes a first sub-pixel block 211, a second sub-pixel block 212, …, and an mth sub-pixel block 21m, where m is greater than or equal to 2 and is an integer, which are sequentially arranged in order of increasing size.
As shown in fig. 3, a schematic diagram of the structure of the collector is exemplarily shown; the pixel block 20 includes a first sub-pixel block 211 and a second sub-pixel block 212, the first sub-pixel block 211 corresponds to a first aperture 241, the second sub-pixel block 212 corresponds to a second aperture 242, the size of the first sub-pixel block 211 is smaller than the size of the second sub-pixel block 212, and the aperture of the first aperture 241 is larger than the aperture of the second aperture 242.
In applications, the distance measurement system may be divided into a coaxial system and an off-axis system, depending on the arrangement between the emitter and the collector. For a coaxial system, the light beam emitted by the emitter is collected by the corresponding pixel in the collector after being reflected by the target, and the distance between the target and the distance measuring system does not influence the position of the pulse light beam reflected by the target on the collector. For an off-axis system, due to the existence of parallax, the positions of the pulse beams reflected by targets located at different distances on the collector are different, the spot size of the pulse beam reflected by a close-range target on the collector is larger than that of the pulse beam reflected by a far-range target on the collector, and the spot offset caused by the influence of the parallax of the system on the pulse beam reflected by the close-range target is larger.
The distance measuring system provided by the embodiment of the application is an off-axis system, at least two diaphragms with different apertures and at least two sub-pixel blocks with different measuring distances are arranged, each diaphragm corresponds to one sub-pixel block, the measuring distance and the size of each sub-pixel block are positively correlated and negatively correlated with the aperture of the corresponding diaphragm, each diaphragm shapes a pulse beam reflected by a target in the ranging range of the corresponding sub-pixel block, each sub-pixel block acquires photons in the pulse beam after being shaped by the corresponding diaphragm and outputs photon signals, so that the distance measuring system can accurately measure the distance between the target and the distance measuring system when the target is positioned at a position nearer or farther in the acquisition view field of the collector, and the measuring error is effectively reduced; the aperture of the diaphragm corresponding to the sub-pixel block with smaller measuring distance is larger than that of the diaphragm corresponding to the sub-pixel block with larger measuring distance, and the size of the sub-pixel block with smaller measuring distance is smaller than that of the sub-pixel block with larger measuring distance. Because the spot offset of the pulse beam reflected by the close-range target is larger, the pulse beam reflected by the close-range target is made to enter the sub-pixel block with smaller size through the diaphragm with larger aperture, so that the spot size can be reduced and the larger parallax range can be covered.
In an application, the size of a sub-pixel block is positively correlated with the number of pixels it contains, i.e. the larger the size of a sub-pixel block the more pixels it contains. When the collector comprises at least two pixel blocks, each pixel block has the same structure, and the size of the sub-pixel block is positively correlated with the measurement distance, i.e. the larger the size of the sub-pixel block, the larger the measurement distance thereof. The number, the size and the measurement distance of the sub-pixel blocks in each pixel block can be set according to the distance measurement range of the distance measurement system, and the measurement accuracy of the distance measurement system is higher as the number of the sub-pixel blocks is larger.
In the application, the ranging range includes an upper limit value and a lower limit value, and the measured distance may be the upper limit value, the lower limit value, or an average value of the upper limit value and the lower limit value of the ranging range, when the sub-pixel blocks in the pixel block are sequentially arranged in order of increasing size, the lower limit value of the ranging range of the preceding sub-pixel block is equal to the upper limit value of the ranging range of the following sub-pixel block; when the sub-pixel blocks in the pixel blocks are sequentially arranged in descending order of size, the upper limit value of the ranging range of the preceding sub-pixel block is equal to the lower limit value of the ranging range of the following sub-pixel block. For example, assuming that the ranging range of the distance measuring system is 0.5m (meter) to 100m, when each pixel block includes two sub-pixel blocks, if the two sub-pixel blocks are sequentially arranged in order of increasing size, the ranging ranges of the two sub-pixel blocks may be 0.5m to 3m and 3m to 100m, respectively, and if the two sub-pixel blocks are sequentially arranged in order of decreasing size, the ranging ranges of the two sub-pixel blocks may be 3m to 100m and 0.5m to 3m, respectively; similarly, when each pixel block includes three sub-pixel blocks, if the three sub-pixel blocks are sequentially arranged in order of increasing size, the ranging ranges of the three sub-pixel blocks may be respectively 0.5m to 3m, 3m to 10m, and 10m to 100m, and if the three sub-pixel blocks are sequentially arranged in order of decreasing size, the ranging ranges of the three sub-pixel blocks may be respectively 10m to 100m, 3m to 10m, and 0.5m to 3m.
In one embodiment, the aperture distance between two diaphragms corresponding to any two adjacent sub-pixel blocks in each pixel block is equal to the parallax corresponding to the lower limit value of the ranging range of the distance measuring system. For example, assuming that the lower limit value of the ranging range of the distance measuring system is 0.5m, the aperture pitch between two diaphragms corresponding to any adjacent two sub-pixel blocks in each pixel block is equal to 480 μm (micrometers).
In an application, the target may be any object in free space. At least part of the pulse light beams emitted by the emitter to the target are reflected by the target back to the collector, so that the collector can collect the pulse light beams reflected by the target and perform photoelectric conversion to obtain corresponding photon signals, and then the photon signals are output to the control and processing circuit. The control and processing circuit synchronously sends trigger signals to the emitter and the collector to synchronously trigger the emitter to emit pulse light beams and the collector to collect the pulse light beams reflected by the target. The trigger signal may be a clock signal, and the clock signal for triggering the transmitter to transmit the pulsed light beam to the target may be defined as a start clock signal. The control and processing circuitry obtains the time of flight of the pulsed light beam by calculating the time required for the pulsed light beam to be emitted to be acquired. Specifically, the control and processing circuit may calculate the time interval from when it sends the start clock signal to when it receives the photon signal, which is the time of flight. Further, the distance of the target can be calculated according to the flight time, and the calculation formula is as follows:
D＝c*t/2；
Where D represents the distance of the target, c represents the speed of light, and t represents the time of flight.
In an application, the emitter comprises a light source unit comprising at least one light source. The light source may be a light emitting Diode (Light Emitting Diode, LED), a Laser Diode (LD), an edge emitting Laser (Edge Emitting Laser, EEL), a vertical cavity surface emitting Laser (Vertical Cavity Surface Emitting Laser, VCSEL), or the like. The number of the light sources included in the light source unit can be set according to actual needs, and the light source unit can be a one-dimensional or two-dimensional light source array consisting of at least two light sources. The light source array can be a vertical cavity surface emitting laser array chip formed by generating a plurality of vertical cavity surface emitting lasers on a single semiconductor substrate, and the arrangement mode of the light sources in the light source array can be regular or irregular. The pulsed light beam emitted by the light source may be visible light, infrared light, ultraviolet light, etc.
In one embodiment, the transmitter further comprises a driver for controlling the light source unit to emit the pulse beam to the target at a preset frequency or a preset pulse period, the preset frequency and the preset pulse period being set according to a ranging range of the distance measuring system, the driver being connected to the light source unit.
In application, the light source unit emits a pulsed light beam towards a target under control of a driver. It will be appreciated that a portion of the control and processing circuitry, or other circuitry that is independent of the presence of the control and processing circuitry, may also be utilized to control the light source unit to emit a pulsed light beam. The preset frequency is positively correlated with the ranging range of the distance measurement system, and the preset pulse period is negatively correlated with the ranging range of the distance measurement system.
In one embodiment, the transmitter further comprises a first optical element for optically modulating the pulsed light beam emitted by the light source unit and projecting the modulated pulsed light beam onto the target.
In applications, the optical modulation may be diffraction, refraction, reflection, etc., and the modulated pulsed light beam may be a focused light beam, a flood light beam, a structured light beam, etc. The first optical element may include at least one of a lens, a liquid crystal element, a diffractive optical element, a microlens array, a super surface (Metasurface) optical element, a mask, a mirror, a Micro-Electro-Mechanical System (MEMS) galvanometer, and the like.
Fig. 1 exemplarily shows that the emitter 1 includes a light source unit 11, a first optical element 12, and a driver 13, the light source unit 11 being connected to the driver 13.
In an application, the collector comprises a pixel unit comprising at least one pixel block, each pixel block comprising at least two sub-pixel blocks. The pixel cell is a pixel array composed of a plurality of single photon avalanche photodiodes (Single Photon Avalanche Diode, SPAD) that can respond to an incident single photon and output a signal indicative of the Time of arrival of the photon at the single photon avalanche photodiode, with collection of weak light signals and calculation of Time of flight using techniques such as Time-dependent single photon counting (Time-Correlated Single Photon Counting, TCSPC).
In application, the collector further comprises at least one of a signal amplifier, a time-to-digital converter (Time to Digital Converter, TDC), an Analog-to-Digital Converter (ADC) and the like which are connected with the pixel unit. These devices may be integrated with the pixel cell or may be part of the control and processing circuitry.
In one embodiment, the collector further comprises a second optical element for focusing the pulsed light beam reflected by the target to the pixel cell.
In one embodiment, the second optical element comprises at least one attenuation sheet, each attenuation sheet corresponding to a sub-pixel block having a measured distance less than a distance threshold, each attenuation sheet for attenuating the light intensity of the pulsed light beam incident to its corresponding sub-pixel.
In one embodiment, the second optical element further comprises an imaging lens for imaging and focusing the pulsed light beam before it is incident on the at least two diaphragms.
In one embodiment, the second optical element further comprises at least two first focusing lenses, each first focusing lens corresponding to one sub-pixel block, each first focusing lens for focusing the pulse beam after shaping via the aperture to its corresponding sub-pixel block.
In an application, the second optical element may include imaging lenses, diaphragms, first focusing lenses and microlens arrays, which are sequentially arranged and equal in number to all sub-pixel blocks, and may further include attenuation sheets corresponding to sub-pixel blocks each of which has a measured distance smaller than a distance threshold. The microlens array includes second focusing lenses equal to the total number of pixels of all the sub-pixel blocks, one first focusing lens corresponding to one sub-pixel block and one second focusing lens corresponding to one pixel in the sub-pixel block. Each first focusing lens is used for focusing the pulse light beams reflected by the target and subjected to imaging focusing through the imaging lens to a plurality of second focusing lenses corresponding to the sub-pixel blocks when the target is positioned in the range of the corresponding sub-pixel blocks, and each second focusing lens is used for focusing the pulse light beams received by the second focusing lens to the pixels corresponding to the second focusing lenses.
In application, since the intensity of the pulse beam reflected by the target at a close distance is high and the photon number is high, the photon stacking effect (photo pileup effect) is easily caused, an attenuation sheet is required to attenuate the light intensity, so that the problem is solved. By setting the attenuation sheets with proper attenuation coefficients, the sub-pixel blocks corresponding to each attenuation sheet can generate effective photon signals for calculating the flight time of the pulse light beam.
In one embodiment, the second optical element further comprises a filtering unit for filtering out background light and stray light incident to all pixel blocks, the filtering unit being arranged between the imaging lens and the first lens. The filter unit may be a low pass filter.
The collector 2 is exemplarily shown in fig. 1 to comprise a pixel unit 21, a filter unit 22 and a second optical element 23. It should be understood that, in fig. 1, the filter unit 22 is disposed between the pixel unit 21 and the second optical element 23 for convenience of illustration, and is not used to limit the relative positions of the filter unit 22 and the second optical element 23 in practical applications.
The second optical element illustrated in fig. 3 exemplarily includes an imaging lens 231, two first focusing lenses 232 and 233, and a microlens array including a plurality of second focusing lenses 234, the first focusing lens 232 corresponding to the sub-pixel block 211, the first focusing lens 233 corresponding to the sub-pixel block 212, and each second focusing lens 234 corresponding to each pixel 2121, respectively, which are disposed in sequence; the filter unit 22 is disposed between the imaging lens 231 and the first and second diaphragms 241 and 242; an attenuation sheet 235 is disposed between the second focusing lens and the first focusing lens 232 corresponding to the sub-pixel block 211.
In one embodiment, the single photon avalanche photodiode is responsive to an incident single photon to output a photon signal, and the control and processing circuitry receives the photon signal and performs signal processing to obtain a time of flight of the optical signal reflected by the target. In particular, the control and processing circuitry calculates the number of photon signals collected to form successive time units (bins) that are concatenated together to form a statistical histogram for reproducing a time series of optical signals reflected by the target, and identifies the time of flight of the optical signals reflected by the target from being transmitted to being received using peak matching and filtering detection. The control and processing circuitry may be a central processing unit (Central Processing Unit, CPU), but may also be other general purpose processors, system-on-a-chips (SOCs), digital signal processors (Digital Signal Processor, DSPs), application specific integrated circuits (Application Specific Integrated Circuit, ASICs), off-the-shelf programmable gate arrays (Field-Programmable Gate Array, FPGAs) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware arrays, or the like. The general purpose processor may be a microprocessor or any conventional processor or the like.
In one embodiment, the distance measurement system further comprises a memory for storing a pulse code program. The driver is connected with the storage and is used for controlling the excitation time, the emission frequency and the like of the pulse light beam emitted by the light source unit by utilizing the pulse coding program.
In one embodiment, the distance measurement system may further include at least one of an RGB camera, an infrared camera, and an Inertial Measurement Unit (IMU) for implementing 3D texture modeling, infrared face recognition, time-positioning and mapping (simultaneous localization and mapping, SLAM), and the like.
In one embodiment, the control and processing circuitry includes:
the number of the TDC circuits is equal to that of all the sub-pixel blocks, each TDC circuit is connected with one sub-pixel block, and each TDC circuit is used for calculating the flight time according to photon signals output by the sub-pixel blocks connected with the TDC circuits and converting the flight time into time codes; alternatively, a TDC circuit equal to the total number of pixels of all the sub-pixel blocks, each TDC circuit being connected to one pixel, each TDC circuit being adapted to calculate a time of flight from a photon signal output from the pixel connected thereto and convert it into a time code;
and a histogram circuit equal to the number of all pixel blocks, each histogram circuit being connected to all the TDC circuits to which one pixel block is connected, the histogram circuit being configured to hold time codes output from all the TDC circuits connected thereto and generate a histogram based on the time codes held during at least one pulse period of the pulse beam, the histogram being configured to characterize the waveform of the pulse beam reflected by the object, based on the histogram.
Fig. 4 exemplarily shows that the control and processing circuit 3 includes a first TDC circuit 311, a second TDC circuit 312, …, and a mTDC circuit 31m, which are connected to the first sub-pixel block 211, the second sub-pixel blocks 212, …, and the mth sub-pixel block 21m in one pixel block 20 in one-to-one correspondence, and further includes a histogram circuit 32 connected to the first TDC circuit 311, the second TDC circuit 312, …, and the mTDC circuit 31 m.
In application, all the TDC circuits included in the control and processing circuit may constitute an array circuit, and each TDC circuit is correspondingly connected to one sub-pixel block or one pixel. The TDC circuit is used for calculating the flight time of the pulse light beam, namely the time difference between the receiving time and the transmitting time according to the receiving time of the received photon signal and the transmitting time of the pulse light beam transmitted by the transmitter to the target, converting the flight time into a time code and storing the time code in a histogram circuit connected with the time code, wherein the time code can be a temperature code or a binary code, and the target is positioned in the ranging range of a sub-pixel block connected with the TDC circuit. The histogram circuit is used for drawing a time code stored by the distance testing system after at least one measurement is finished into a histogram which can represent the waveform of the pulse beam reflected by the target, and the time of each measurement is at least one pulse period of the pulse beam.
In one embodiment, the time width of each TDC circuit is positively correlated with the measured distance of its connected sub-pixel block, and the time resolution of each TDC circuit is negatively correlated with the measured distance of its connected sub-pixel block.
In one embodiment, the time code is a temperature code or a binary code.
In application, the time width of the TDC circuit is influenced by the measured distance of the sub-pixel blocks connected with the TDC circuit, the time resolution of the TDC circuit influences the measuring precision of the distance measuring system, and the more the number of bits of the time code output by the TDC circuit is, the higher the memory requirement of the histogram circuit connected with the TDC circuit is. In order to reduce the data storage amount, reduce the consumption of the storage space of the histogram circuit and save the cost, the time width and the time resolution of each TDC circuit need to be reasonably set so that the time width of the TDC circuit connected to the sub-pixel block with smaller measurement distance is smaller than the time width of the TDC circuit connected to the sub-pixel block with larger measurement distance, and the time resolution of the TDC circuit connected to the sub-pixel block with smaller measurement distance is higher than the time resolution of the TDC circuit connected to the sub-pixel block with larger measurement distance. For example, when the ranging range of the sub-pixel block is 0.3m to 3m, the time resolution of the TDC circuit connected thereto is 125 picoseconds (ps); when the range of the sub-pixel block is 3 m-100 m, the time resolution of the TDC circuit connected with the sub-pixel block is 0.5 nanoseconds (ns). The histogram circuit forms a histogram of different time cell widths from a time code (time code) output from each TDC circuit connected thereto, the width of the time cell being determined by the time resolution of the TDC circuit.
In one embodiment, the turn-on time of the TDC circuit connected to the sub-pixel block having a large measured distance lags the turn-on time of the TDC circuit connected to the sub-pixel block having a small measured distance among all the TDC circuits electrically connected to one of the pixel blocks.
In application, for sub-pixel blocks with larger measuring distances, the transmission time of the pulse beam reflected by the target is longer because the measured target distance is longer, so the turn-on time of the connected TDC circuit can be delayed by a certain time relative to the start clock signal.
In one embodiment, the turn-on times of all TDC circuits connected to one pixel block are sequentially delayed in order of increasing measured distance of the sub-pixel block; the turn-on time of the first TDC circuit is synchronous with the emission time of the pulse beam, and the delay time of the turn-on time of other TDC circuits relative to the emission time is larger than or equal to the flight time corresponding to the lower limit value of the ranging range of the sub-pixel block connected with the turn-on time of the first TDC circuit.
In application, the turn-on time of the TDC circuit connected to the sub-pixel block with the smallest measurement distance in each pixel block is synchronous with the start clock signal (i.e. the emission time of the pulse beam), the turn-on time of other TDC circuits is sequentially delayed with respect to the start clock signal, the delay time of each TDC circuit may be determined according to the flight time corresponding to the lower limit value of the ranging range of the sub-pixel block connected thereto, for example, the ranging range of the sub-pixel block connected to one TDC circuit is 3m-100m, and then the TDC circuit delay time may be set to 3 m/c=20ns, which is the flight time corresponding to the lower limit value 3m of 3m-100m, and when the histogram circuit draws the histogram according to the time code output by the TDC circuit, the histogram circuit starts to draw at the time unit corresponding to the delay 20ns with respect to the start clock signal.
In one embodiment, the sub-pixel block having a size greater than the preset size threshold includes a blank area where no pixels are disposed, where the blank area is disposed in a non-edge area of the sub-pixel block where it is disposed or an area adjacent to other sub-pixel blocks.
In application, since the larger the size of the sub-pixel block is, the more pixels are included, in order to reduce the number of pixels in the sub-pixel block with larger size, a blank area can be set in the sub-pixel block, so that the number of photon signals received by a TDC circuit connected with the sub-pixel block can be reduced, correspondingly, the storage capacity of a histogram circuit which needs to be consumed can be reduced, so that the histogram circuit can use a memory with smaller memory, and the integration difficulty of a single sub-pixel block can be reduced by reducing the number of pixels of the sub-pixel block.
Fig. 5 exemplarily shows that one pixel block 20 includes a first sub-pixel block 211 and a second sub-pixel block 212, the first sub-pixel block 211 includes 3×3 pixels, the second sub-pixel block 212 includes a blank region 2121 and 3×6 pixels, and the blank region 2121 is disposed at a region of the first sub-pixel block 211 adjacent to the second sub-pixel block 212.
Fig. 6 exemplarily shows that one pixel block 20 includes a first sub-pixel block 211 and a second sub-pixel block 212, the first sub-pixel block 211 includes 3×3 pixels, the second sub-pixel block 212 includes 3×8 pixel areas, the pixel areas of the second column, the fourth column, and the sixth column in the second row of the second sub-pixel block 212 are not provided with pixels, and the remaining pixel areas are provided with pixels.
In one embodiment, the emitter includes at least two light source columns sequentially offset a first distance in a preset direction (e.g., a vertical direction), each light source column includes at least two light sources sequentially arranged in the preset direction, and a distance between two adjacent light sources in each light source column in the preset direction is greater than or equal to a second distance;
the collector comprises at least two pixel columns which are sequentially offset by a first distance in a preset direction, each pixel column comprises at least two pixel blocks which are sequentially arranged in the preset direction, and the distance between two adjacent pixel blocks in each pixel column in the preset direction is larger than or equal to a second distance;
the distance measuring system is arranged on a horizontal plane, the preset direction is a vertical direction, the first distance is larger than or equal to the diameter of the light sources, and the second distance is larger than or equal to the product of the total number of light source columns included by the emitter and the first distance.
In application, the preset direction can be customized to be any direction according to actual needs, when the distance measurement system is placed on a horizontal plane, the preset direction is a vertical direction perpendicular to the horizontal plane, no matter how the distance measurement system is placed, only the preset direction is ensured to be perpendicular to the plane where the distance measurement system is placed.
In application, the first distance may be set to any value greater than or equal to the diameter of the light source according to actual needs, and the second distance may be set to any value greater than or equal to the product of the total number of light source columns included in the emitter and the first distance according to actual needs. This arrangement of the light source units can be understood as inserting at least one light source between adjacent light sources of one light source column to form a light source column with a larger number of light sources and even distribution so that the pulse light beams projected to the object by the light source units form a scanning line with continuous spots. By increasing the interval between adjacent light sources in a single light source column, the crosstalk between pulse light beams emitted by the adjacent light sources can be effectively reduced; by setting at least two light source columns, the target is rotated and scanned to obtain a point cloud image, and the rotation scanning resolution of the target is higher than that of one light source column; and under the condition that the areas of the pixel units are the same, at least two light source columns are arranged opposite to one light source column, so that the number of light sources in each light source column can be reduced, the manufacturing difficulty of the light source units is reduced, a larger view field can be obtained in a preset direction, and the measurement frame rate of the distance measurement system is improved.
The light source unit 11 exemplarily shown in fig. 7 includes three light source arrays 101, 102 and 103, each of which includes 6 light sources 10, and the corresponding pixel unit 21 also includes three pixel arrays 201, 202 and 203, each of which includes 6 pixel blocks 20, a distance between adjacent two light sources 10 is d, and a first distance is d/3.
In one embodiment, the distance measurement system further comprises a rotating base, and the emitter and the collector are mounted on the rotating base, so that the emitter and the collector can rotate and scan under the control of the control and processing circuit to achieve distance measurement of the target in the 360-degree large field of view.
The swivel base 4 is exemplarily shown in fig. 7.
The embodiment of the application also provides a distance measurement method realized based on the distance measurement system 100, which comprises the following steps:
controlling the transmitter to transmit a pulsed light beam to the target;
each sub-pixel block of the collector is controlled to collect photons in the pulse light beam after being shaped by the corresponding diaphragm and output photon signals, the collector comprises at least one pixel block and at least two diaphragms, each pixel block comprises at least two sub-pixel blocks which are sequentially arranged in the order of increasing or decreasing size, one sub-pixel block corresponds to one diaphragm, the size of each sub-pixel block is positively correlated with the measuring distance and is negatively correlated with the aperture of the corresponding diaphragm, and each diaphragm is used for shaping the pulse light beam reflected by a target in the ranging range of the corresponding sub-pixel block;
And calculating the flight time of the pulse light beam according to the photon signal.
In one embodiment, said calculating the time of flight of said pulsed light beam from said photon signal comprises:
calculating flight time according to photon signals output by each sub-pixel block and converting the flight time into a time code;
all the time codes are saved and a histogram is generated from the time codes saved during at least one period of the pulsed light beam, based on which the time of flight of the pulsed light beam is determined, the histogram being used to characterize the waveform of the pulsed light beam reflected by the target.
In application, the distance measurement method may be performed by the control and processing circuitry when running a computer program stored in the control and processing circuitry or in a memory.
The embodiment of the application also provides a computer readable storage medium, wherein the computer readable storage medium stores a computer program, and the computer program realizes the steps in the embodiment of the distance measuring method when being executed by a processor.
Embodiments of the present application provide a computer program product for causing a distance measuring system to perform the steps of the distance measuring method embodiments described above when the computer program product is run on the distance measuring system.
According to the embodiment of the application, the pulse light beam is emitted to the target through the emitter; the collector comprises at least one pixel block and at least two diaphragms, wherein each pixel block comprises at least two sub-pixel blocks which are sequentially arranged according to the ascending or descending order of the size, one sub-pixel block corresponds to one diaphragm, the size and the measuring distance of each sub-pixel block are positively correlated and negatively correlated with the aperture of the corresponding diaphragm, each diaphragm is used for shaping a pulse beam reflected by a target in the ranging range of the corresponding sub-pixel block, and each sub-pixel block is used for collecting photons in the pulse beam after being shaped by the corresponding diaphragm and outputting photon signals; by connecting the control and processing circuit with the emitter and the collector, respectively, and calculating the time of flight of the pulsed light beam based on the photon signals, accurate measurement of the distance between different targets located at least two measurement distances and the distance measurement system can be achieved, effectively reducing measurement errors.
In the foregoing embodiments, the descriptions of the embodiments are emphasized, and in part, not described or illustrated in any particular embodiment, reference is made to the related descriptions of other embodiments.
Those of ordinary skill in the art will appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.
The above embodiments are only for illustrating the technical solution of the present application, and not for limiting the same; although the application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present application, and are intended to be included in the scope of the present application.
Claims (9)
1. A distance measurement system, comprising:
A transmitter for transmitting a pulse light beam to a target, the transmitter comprising at least two light source columns sequentially offset by a first distance in a preset direction, each light source column comprising at least two light sources sequentially arranged in the preset direction, a distance between two adjacent light sources in each light source column in the preset direction being greater than or equal to a second distance;
the device comprises an acquisition device, a measuring device and a measuring device, wherein the acquisition device comprises at least two pixel columns and at least eight diaphragms which are sequentially offset by a first distance in a preset direction, each pixel column comprises at least two pixel blocks which are sequentially arranged in the preset direction, the distance between two adjacent pixel blocks in each pixel column in the preset direction is larger than or equal to a second distance, each pixel block comprises at least two sub-pixel blocks which are sequentially arranged in an ascending or descending order of size, one sub-pixel block corresponds to one diaphragm, the size of each sub-pixel block is positively correlated with the measuring distance and is negatively correlated with the aperture of the diaphragm corresponding to the sub-pixel block, each sub-pixel block is used for shaping a pulse beam reflected by a target in the ranging range of the corresponding sub-pixel block, and each sub-pixel block is used for acquiring photons in the pulse beam after the corresponding diaphragm and outputting photon signals;
Wherein the preset direction is a vertical direction when the distance measurement system is placed on a horizontal plane, the first distance is greater than or equal to the diameter of the light source, and the second distance is greater than or equal to the product of the total number of light source columns included by the emitter and the first distance;
and the control and processing circuit is respectively connected with the emitter and the collector and is used for calculating the flight time of the pulse light beam according to the photon signals.
2. The distance measurement system of claim 1, wherein the collector further comprises at least one attenuation pad, each of the attenuation pads corresponding to a sub-pixel block having a measured distance less than a distance threshold, each of the attenuation pads for attenuating light intensity of the pulse light beam incident to its corresponding sub-pixel.
3. The distance measurement system of claim 2 wherein the collector further comprises an imaging lens for imaging and focusing the pulsed light beam reflected by the target before the pulsed light beam reflected by the target is incident on the diaphragm.
4. The distance measurement system of claim 1, wherein the collector further comprises at least eight first focusing lenses, one for each sub-pixel block, each for focusing the pulsed light beam after shaping via the aperture to its corresponding sub-pixel block.
5. The distance measurement system of claim 1, wherein the collector further comprises a filtering unit for filtering out background light and stray light incident on the at least one pixel block.
6. The distance measuring system according to claim 1, wherein an aperture distance between two diaphragms corresponding to any adjacent two sub-pixel blocks in each of the pixel blocks is equal to a parallax corresponding to a lower limit value of a ranging range of the distance measuring system.
7. The distance measurement system of any one of claims 1 to 6 wherein the control and processing circuitry includes a number of TDC circuits equal to the number of all of the sub-pixel blocks, each TDC circuit being connected to one of the sub-pixel blocks, the time width of each TDC circuit being positively correlated with the measured distance of the sub-pixel block to which it is connected, and the time resolution of each TDC circuit being negatively correlated with the measured distance of the sub-pixel block to which it is connected.
8. A distance measurement method based on any one of claims 1-7, comprising:
controlling an emitter to emit a pulse light beam to a target, wherein the emitter comprises at least two light source columns which are sequentially offset by a first distance in a preset direction, each light source column comprises at least two light sources which are sequentially arranged in the preset direction, and the distance between two adjacent light sources in each light source column in the preset direction is larger than or equal to a second distance;
Each sub-pixel block of the collector is controlled to collect photons in the pulse light beam after being shaped by the corresponding diaphragm and output photon signals, the collector comprises at least two pixel columns and at least eight diaphragms, the at least two pixel columns and the at least eight diaphragms are sequentially offset by a first distance in a preset direction, each pixel column comprises at least two pixel blocks which are sequentially arranged in the preset direction, the distance between two adjacent pixel blocks in each pixel column in the preset direction is greater than or equal to a second distance, each pixel block comprises at least two sub-pixel blocks which are sequentially arranged in an ascending or descending order of size, one sub-pixel block corresponds to one diaphragm, the size and the measurement distance of each sub-pixel block are positively correlated and negatively correlated with the aperture of the corresponding diaphragm, and each diaphragm is used for shaping the pulse light beam reflected by a target located in the ranging range of the corresponding sub-pixel block;
and calculating the flight time of the pulse light beam according to the photon signal.
9. A computer readable storage medium storing a computer program, characterized in that the computer program when executed by a processor implements the steps of the distance measuring method according to claim 8.
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| CN113075672A (en) * | 2021-03-03 | 2021-07-06 | 深圳市灵明光子科技有限公司 | Ranging method and system, and computer readable storage medium |
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