WO2021103428A1 - 一种深度测量***及方法 - Google Patents

一种深度测量***及方法 Download PDF

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WO2021103428A1
WO2021103428A1 PCT/CN2020/089780 CN2020089780W WO2021103428A1 WO 2021103428 A1 WO2021103428 A1 WO 2021103428A1 CN 2020089780 W CN2020089780 W CN 2020089780W WO 2021103428 A1 WO2021103428 A1 WO 2021103428A1
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time
duty cycle
rising
falling edge
pulse beam
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PCT/CN2020/089780
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English (en)
French (fr)
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马宣
孙飞
孙瑞
杨神武
周兴
崔东曜
方兆翔
王兆民
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深圳奥比中光科技有限公司
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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
    • 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
    • G01S17/88—Lidar systems specially adapted for specific applications
    • G01S17/89—Lidar systems specially adapted for specific applications for mapping or imaging
    • 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
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/483—Details of pulse systems
    • G01S7/484—Transmitters

Definitions

  • the present invention relates to the technical field of depth measurement, in particular to a depth measurement system and method.
  • ToF ranging technology is a technology that achieves precise ranging by measuring the round-trip flight time of light pulses between the transmitting/receiving device and the target object.
  • d-ToF direct-ToF
  • the emitted light signal is periodically modulated, and the phase delay of the reflected light signal relative to the emitted light signal is measured
  • the measurement technology that calculates the flight time by the phase delay is called iToF (Indirect-ToF) technology.
  • modulation and demodulation it can be divided into continuous wave (CW) modulation and demodulation method and pulse modulation (Pulse Modulated, PM) modulation and demodulation method.
  • CW continuous wave
  • PM Pulse Modulated
  • Continuous wave modulation usually modulates the frequency spectrum of the emitted light into a square wave with varying intensity, and the demodulation terminal detects the phase change of the waveform after being reflected by the target object.
  • This measurement method first binds the optical flight distance information with the phase information of the light intensity change. Then, the phase information is converted into the light intensity information that can be detected by the photodetector, which indirectly realizes the measurement of the optical flight time.
  • the light source emits a sine wave whose power varies with time to the target object, and the ToF image sensor collects the signal returned by the target object to calculate the optical flight distance.
  • this has very strict requirements on the light source and the driving circuit. Therefore, in practice, a square wave is used instead of a sine wave to modulate the emitted light power. This will inevitably cause system errors (wiggling) due to the unsatisfactory waveform of the light source emitted light power spectrum. .
  • the present invention provides a depth measurement system and method.
  • a depth measurement system includes: a transmitting module, including a light source, used to transmit a pulsed light beam whose power-time waveform is modulated to a target object; The pulse beam reflected by the target object generates a gray-scale image; a control and processing circuit is used to provide the modulation signal required by the light source to emit the pulse beam and control the duty cycle and rising/falling edge time of the pulse beam. Control the acquisition module to receive the pulse beam, and calculate the flight time of the pulse beam and/or the distance of the target object based on the gray image; the duty ratio of the pulse beam and the rise/ The matching of the falling edge time is used to reduce the system error.
  • the mutual matching includes: when the rising/falling edge time is fixed, the duty cycle of the pulsed beam is configured as an optimal duty cycle, and the optimal duty cycle is
  • the empty ratio is the duty ratio with the smallest extreme value, and the extreme value is the difference between the maximum system error corresponding to the actual optical flight distance and the minimum system error corresponding to the actual optical flight distance.
  • the range of the duty cycle is 1-99%.
  • the duty cycle of the pulse beam and the rising/falling edge time are configured to satisfy the relationship:
  • t rise/fall represents the rising/falling edge time
  • DR represents the duty cycle
  • T represents the modulation period of the pulse beam
  • B represents a numerical code.
  • each of the pixels includes four taps, and the taps are used to collect electricity generated by the pulse beam reflected by the target object in different time periods within a single frame period. signal.
  • the time of the collection interval of the four taps is T/4, and the initial collection time of the taps is any time within T, where T is the modulation period of the pulse beam.
  • the present invention also provides a depth measurement method, including the following steps: S1: controlling the transmitting module to transmit a pulse beam with modulated power-time waveform to the target object; S2: controlling the acquisition module to collect the pulse beam reflected by the target object and Generate a grayscale image; S3: provide the modulation signal required by the transmitter module to emit the pulsed beam, wherein the duty cycle and rising/falling edge time of the pulsed beam are matched with each other to reduce system errors; and control at the same time
  • the acquisition module receives the pulsed light beam, and calculates the flight time of the pulsed light beam and/or the distance of the target object based on the gray-scale image.
  • the mutual matching includes: when the rising/falling edge time is fixed, the duty cycle of the pulsed beam is configured as an optimal duty cycle, and the optimal duty cycle is
  • the empty ratio is the duty ratio with the smallest extreme value, and the extreme value is the difference between the maximum system error corresponding to the actual optical flight distance and the minimum system error corresponding to the actual optical flight distance.
  • the range of the duty cycle is 1-99%.
  • the duty cycle of the pulse beam and the rising/falling edge time are configured to satisfy the relationship:
  • t rise/fall represents the rising/falling edge time
  • DR represents the duty cycle
  • T represents the modulation period of the pulse beam
  • B represents a numerical code.
  • the beneficial effects of the present invention are as follows: provide a depth measurement system and method, by setting the duty ratio and rising/falling edge time of the pulse beams that match each other, the system error is reduced, and the problem that the power spectrum waveform of the light emitted by the light source is not ideal is solved , Improve measurement accuracy.
  • Fig. 1 is a schematic structural diagram of a depth measurement system in an embodiment of the present invention.
  • Fig. 2 is a schematic diagram of a method for transmitting and collecting optical signals of a depth measurement system in an embodiment of the present invention.
  • Fig. 3 is a schematic diagram of a depth measurement method in an embodiment of the present invention.
  • Fig. 4 is a schematic diagram of a systematic error-duty cycle in an embodiment of the present invention.
  • 11-transmitting module 11-transmitting module, 12-acquisition module, 13-control and processing circuit, 20-target object, 30-pulse beam, 121-image sensor, 40-pulse beam reflected by the target object.
  • connection can be used for fixing or circuit connection.
  • first and second are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with “first” and “second” may explicitly or implicitly include one or more of these features.
  • a plurality of means two or more than two, unless otherwise specifically defined.
  • FIG. 1 is a schematic structural diagram of a depth measurement system 10 in an embodiment of the present invention.
  • the depth measurement system 10 includes a transmitting module 11, an acquisition module 12 and a control and processing circuit 13.
  • the transmitting module 11 includes a light source (not shown in the figure) for transmitting a pulsed light beam 30 whose power is modulated to the target object 20, and the acquisition module 12 includes an image sensor 121 composed of at least one pixel, which is used to capture the target object 20.
  • the pulse beam 40 reflected by the object 20 generates a grayscale image; the control and processing circuit 13 is used to provide the modulation signal required by the light source to emit the pulse beam 30 and control the duty cycle and the rising/falling edge time of the pulse beam 30, while controlling the acquisition
  • the module 12 collects the pulse beam 40 reflected by the target object 20 and generates a grayscale image, and calculates the flight time of the pulse beam and/or the distance of the target object 20 based on the grayscale image.
  • the emission module 11 includes a light source, a patterned optical element, a light source driver (not shown in the figure), and the like.
  • the light source can be a light source such as a light emitting diode (LED), an edge emitting laser (EEL), a vertical cavity surface emitting laser (VCSEL), or a light source array composed of multiple light sources.
  • the light beam emitted by the light source can be visible light, infrared light, Ultraviolet light, etc.
  • the light source is controlled by the light source driver (which can be further controlled by the control and processing circuit 13) and then emits a light beam to the target object 20 after being modulated in amplitude at a certain time sequence.
  • the light source emits a pulse modulated light beam or a square wave at a certain frequency under control. Beams such as modulated beams. It is understandable that a part of the control and processing circuit 13 or a sub-circuit that exists independently of the control and processing circuit 13 can be used to control the light source to emit related light beams.
  • the collection module 12 includes an image sensor 121.
  • the image sensor 121 may be a Charge Coupled Device (CCD), a Complementary Metal-Oxide-Semiconductor Transistor, CMOS), Avalanche Diode (AD), and Single Photon Avalanche Diode (Single Photon Avalanche). Diode, SPAD) and other image sensor 121.
  • CCD Charge Coupled Device
  • CMOS Complementary Metal-Oxide-Semiconductor Transistor
  • AD Avalanche Diode
  • SPAD Single Photon Avalanche Diode
  • SPAD Single Photon Avalanche Diode
  • the ToF image sensor 121 includes at least one pixel, and each pixel includes four taps (tap, used to store and read or discharge the charge signal generated by incident photons under the control of the corresponding electrode). Within the frame period (or within a single exposure time), the taps are sequentially switched in a certain order to collect corresponding photons for receiving light signals and converting them into grayscale values.
  • the control and processing circuit 13 is used to provide a modulation signal required when the light source emits a pulsed light beam, and the light source emits a light beam to the target object 20 under the control of the modulation signal.
  • the modulation signal is a continuous wave signal such as a sine wave signal, and the light source emits a pulse beam to the target object 20 under the modulation of the sine wave signal, and the power changes in the form of a sine wave in time sequence.
  • the light source emits a pulsed beam 30 to the target object 20 under the modulation of a sine wave signal, and the power changes in the form of a sine wave in time sequence.
  • the grayscale image collected by different taps of each pixel of the image sensor 121 can calculate the target.
  • the power-time waveform of this modulation is very demanding on the light source and the driving circuit, so in practice, a square wave is used instead of a sine wave to modulate the emitted light power.
  • the modulated emission wave will become a trapezoidal wave with rising/falling edges due to device limitations, which will inevitably lead to unsatisfactory emitted light power spectrum waveforms and system errors.
  • the wiggling caused by the non-sinusoidal power spectrum-time wave emitted by the light source can be reduced by adjusting the optical power spectrum-time waveform emitted by the light source.
  • the actual optical power spectrum waveform emitted by the light source is trapezoidal. It is assumed that the time for the trapezoidal wave signal to rise from the minimum value to the maximum value or to fall from the maximum value to the minimum value is equal, that is, the rising/falling edge time is equal.
  • the waveform can be changed by changing the duty cycle of the light source emitted light power spectrum-time, and the influence of the duty cycle and the rising/falling edge time on the system error (wiggling) can be obtained, so that the duty cycle and the rising/falling of the pulse beam 30
  • the edge time is configured to reduce wiggling.
  • FIG. 2 is a schematic diagram of a method for transmitting and collecting optical signals of a depth measurement system according to an embodiment of the present invention.
  • Figure 2 exemplarily shows the timing diagram of the laser emission signal (power spectrum-time modulation signal), the received signal, and the acquisition signal (demodulation signal) within two frame periods T, where the meaning of each signal is: Sp represents the light source Each pulse emission signal represents a pulse beam; Sr represents the reflected light signal of the pulse light reflected by the object, and each reflected light signal represents the corresponding pulse beam emitted by the target object 20, which is in the time line ( The horizontal axis in the figure has a certain delay relative to the pulse emission signal.
  • the delay time t light, m is the flight time of the pulse beam that needs to be calculated; S1 represents the time interval of the first tap pulse collection of the pixel, and S2 represents the first pixel of the pixel.
  • the electrical signals (electronics) generated by the pixels are output with different gray values from each tap.
  • the transmitting module 11 emits a pulsed beam 30 to the target object 20.
  • the rising/falling edge time t of the pulsed beam is equal, and the image sensor 121 has four pixels per pixel. Taps are used to collect light signals four times in different time intervals of a single frame period and convert them into electrical signals, and finally output the gray value, in the order of S1-S2-S3-S4 to collect 0 ⁇ T/4( 0 ⁇ 90°), T/4 ⁇ T/2(90° ⁇ 180°), T/2 ⁇ 3T/4(180° ⁇ 270°), 3T/4 ⁇ T(270° ⁇ 360°) Based on the electrical signals collected by the four taps, the control and processing circuit 13 can calculate the actual optical flight time and distance according to the following formula:
  • L m represents the light flight distance calculated by the gray value collected by the image sensor
  • t light represents the light flight time calculated by the gray value collected by the sensor
  • c represents the speed of light
  • T represents the optical power spectrum modulation cycle.
  • interval time of each tap may not be equal to T/4
  • the initial acquisition time of the tap can be any time within the period T
  • the number of taps can be two or three. None is done here. limits.
  • the light source emits a pulsed beam to the target object 20 under the modulation of a sinusoidal power-time signal.
  • the power changes in the form of a sinusoidal wave in time sequence.
  • the ideal light flight without error can be obtained according to formula (1) Time t fly , and thus calculate the ideal light flight distance L fly without error according to formula (2).
  • the actual light flight distance L m is calculated from the modulated non-sinusoidal power-time emission light and the modulated sine
  • the difference between the power-time emission light calculation and the ideal light flight distance L fly is the system error (wiggling), so the system error (wiggling) can be calculated according to the following formula:
  • t light.m represents the light flight time calculated from the modulated non-sinusoidal power-time emission light
  • t fly represents the light flight time calculated from the modulated sinusoidal power-time emission light
  • the control and processing circuit 13 controls the transmitter module 11 to emit a modulated trapezoidal power-time pulse beam. Assuming that the pulse beam has a rising/falling edge time of 0% and a duty cycle of 1%, the duty cycle can be obtained according to formula (3)
  • the system error (wiggling) corresponding to the ratio and rising/falling edge time; changing the actual light flight time t fly multiple times, that is, changing the actual light flight distance L fly can obtain the change curve of the system error (wiggling) and the actual light flight distance L fly , i.e.
  • the extremum is a maximum flight actual optical system corresponding to the error distance L fly (wiggling) the difference between the actual light L fly the flight distance corresponding to the minimum system error (wiggling) of.
  • the duty cycle ranges from 1 to 99%, and the extreme value change curves corresponding to different duty cycles at a rising/falling edge time of 0% can be obtained, and then a maximum value can be obtained.
  • Optimal duty cycle (the extreme value corresponding to this duty cycle is the smallest).
  • the rising/falling edge time of the pulsed beam is 1%
  • the duty cycle ranges from 1 to 99%
  • the rising/falling edge time of 1% can also be obtained.
  • an optimal duty ratio can also be obtained.
  • the rising/falling edge time of the emitted pulse beam is different.
  • the extreme value change curve corresponding to the different duty ratio at each rising/falling edge time can be obtained, and then each can be obtained.
  • the corresponding optimal duty cycle at the rising/falling edge time For a fixed rising/falling edge time, the extreme value corresponding to the optimal duty cycle of the pulse beam is the smallest, that is, the system error generated under the rising/falling edge time-duty cycle configuration is the smallest. Therefore, the system error (wiggling) can be reduced by controlling the duty ratio and the rising/falling edge time of the transmitted pulse beam 30.
  • the duty cycle and rising/falling edge time of the pulsed beam 30 are configured to satisfy the relationship to minimize the system error (wiggling):
  • t rise/fall represents the rising/falling edge time
  • DR represents the duty cycle
  • T represents the modulation period of the pulse beam
  • B represents a numerical code, which takes a value in B ⁇ (1.9334, 2.1334).
  • Fig. 3 is a flowchart of a depth measurement method in an embodiment of the application, including the following steps:
  • the transmitting module includes a light source for emitting a power-time modulated pulse beam 30 to the target object 20, and the duty cycle and rising/falling edge time of the pulse beam 30 are configured to reduce system errors.
  • the mutual matching includes: when the rising/falling edge time is fixed, the duty cycle of the pulsed beam is configured as an optimal duty cycle, and the optimal duty cycle is the smallest extreme value.
  • the extreme value is the difference between the maximum system error corresponding to the actual optical flight distance and the minimum system error corresponding to the actual optical flight distance.
  • the duty cycle and rising/falling edge time of the pulse beam 30 are configured to satisfy the relationship:
  • t rise/fall represents the rising/falling edge time
  • DR represents the duty cycle
  • S302 Control the collection module to collect the pulsed light beam reflected by the target object and generate a grayscale image
  • the acquisition module 12 includes an image sensor 121 composed of at least one pixel, and each pixel includes four taps. The taps are used to collect the pulsed light beam 40 reflected by the target object 20 and output a gray value.
  • S303 Provide a modulation signal required by the transmitting module to transmit the pulse beam, wherein the duty cycle of the pulse beam and the rising/falling edge time are matched with each other to reduce system errors; at the same time, the acquisition is controlled.
  • the module receives the pulsed light beam, and calculates the flight time of the pulsed light beam and/or the distance of the target object based on the gray-scale image.
  • FIG 4 it is a schematic diagram of the system error-duty cycle in a depth measurement system of the present invention. It can be obtained from the figure that when the duty cycle is about 34%, the maximum value and the minimum value of the system error The difference is the smallest (12mm), which is 26mm smaller than the system error extreme difference (38mm) corresponding to a 50% duty cycle. At the same time, the relationship between the difference of the extreme value of the system error and the change of the duty cycle meets the theoretical prediction, and the relationship between the optimal duty cycle and the rising/falling edge time meets the theoretical relationship. Therefore, the duty cycle and rising/falling edge time of the pulse beam can be matched to each other to reduce the system error.

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Abstract

本发明提供一种深度测量***及方法，***包括：发射模组，包括光源，用于向目标物体发射功率-时间波形被调制的脉冲光束；采集模组，包括由至少一个像素组成的图像传感器，用于采集由所述目标物体反射的脉冲光束并生成灰度图像；控制与处理电路，用于提供所述光源发射所述脉冲光束所需的调制信号并控制脉冲光束的占空比和上升/下降沿时间，同时控制所述采集模组接收所述脉冲光束，基于所述灰度图像计算出所述脉冲光束的飞行时间和/或所述目标物体的距离；所述脉冲光束的占空比和所述上升/下降沿时间相互匹配用于降低***误差。通过设置相互匹配的脉冲光束的占空比和上升/下降沿时间，降低***误差，提高测量精度。

Description

一种深度测量***及方法 技术领域
本发明涉及深度测量技术领域，尤其涉及一种深度测量***及方法。
背景技术
ToF的全称是Time-of-Flight，即飞行时间，ToF测距技术是一种通过测量光脉冲在发射/接收装置和目标物体间的往返飞行时间来实现精确测距的技术。在ToF技术中直接对光飞行时间进行测量的技术被称为d-ToF(direct-ToF)；对发射光信号进行周期性调制，通过对反射光信号相对于发射光信号的相位延迟进行测量，再由相位延迟对飞行时间进行计算的测量技术被成为iToF(Indirect-ToF)技术。按照调制解调类型方式的不同可以分为连续波(Continuous Wave，CW)调制解调方法和脉冲调制(Pulse Modulated，PM)调制解调方法。
连续波调制通常将发射光波率谱调制为强度变化的方波，解调端检测经目标物体反射后的波形相位变化，这种测量方法首先将光飞行距离信息与光强变化的相位信息进行绑定，再将相位信息转换为光电探测器可检测的光强信息，间接实现了光飞行时间的测量。
光源向目标物体发射功率随时间变化的正弦波，ToF图像传感器采集目标物体返回来的信号以计算光飞行距离。然而，这对光源以及驱动电路的要求十分苛刻，因此在实际中是以方波代替正弦波进行发射光功率的调制，这必然会由于光源发射光功率谱波形不理想而引起***误差(wiggling)。
发明内容
本发明为了解决现有的问题，提供一种深度测量***及方法。
为了解决上述问题，本发明采用的技术方案如下所述：
一种深度测量***，包括：发射模组，包括光源，用于向目标物体发射功率-时间波形被调制的脉冲光束；采集模组，包括由至少一个像素组成的图像传感器，用于采集由所述目标物体反射的脉冲光束并生成灰度图像；控制与处理电路，用于提供所述光源发射所述脉冲光束所需的调制信号并控制脉冲光束的占空比和上升/下降沿时间，同时控制所述采集模组接收所述脉冲光束，基于所述灰度图像计算出所述脉冲光束的飞行时间和/或所述目标物体的距离；所述脉冲光束的占空比和所述上升/下降沿时间相互匹配用于降低***误差。
在本发明的一种实施例中，所述相互匹配包括：在所述上升/下降沿时间固定的情况下，所述脉冲光束的占空比配置为最优占空比，所述最优占空比为极值最小的占空比，所述极值是实际光飞行距离对应的最大***误差与实际光飞行距离对应的最小***误差之差。所述占空比的范围是1～99％。所述脉冲光束的占空比和所述上升/下降沿时间被配置成满足关系式：
Figure PCTCN2020089780-appb-000001
其中，t rise/fall表示上升/下降沿时间，DR表示占空比，T表示所述脉冲光束的调制周期，B表示一个数值代号。
在本发明的另一种实施例中，每个所述像素包括四个抽头，所述抽头用于在单个帧周期内的不同时间段分别采集由所述目标物体反射的脉冲光束所产生的电信号。四个所述抽头采集间隔的时间为T/4，所述抽头的初始采集时间为T内的任意时间，所述T是所述脉冲光束的调制周期。
本发明又提供一种深度测量方法，包括如下步骤：S1：控制发射模组向目标物体发射功率-时间波形被调制的脉冲光束；S2：控制采集模组采集所述目标物体反射的脉冲光束并生成灰度图像；S3：提供所述发射模组发射所述脉冲光束所需的调制信号，其中，所述脉冲光束的占空比和上升/下降沿时间相互匹配用于降低***误差；同时控制所述采集模组接收所述脉冲光束，基于所述灰度图像计算出所述脉冲光束的飞行时间和/或所述目标物体的距离。
在本发明的一种实施例中，所述相互匹配包括：在所述上升/下降沿时间固定的情况下，所述脉冲光束的占空比配置为最优占空比，所述最优占空比为极值最小的占空比，所述极值是实际光飞行距离对应的最大***误差与实际光飞行距离对应的最小***误差之差。所述占空比的范围是1～99％。所述脉冲光束的占空比和所述上升/下降沿时间被配置成满足关系式：
Figure PCTCN2020089780-appb-000002
其中，t rise/fall表示上升/下降沿时间，DR表示占空比，T表示所述脉冲光束的调制周期，B表示一个数值代号。
本发明的有益效果为：提供一种深度测量***及方法，通过设置相互匹配的 脉冲光束的占空比和上升/下降沿时间，降低***误差，从而解决光源发射光功率谱波形不理想的问题，提高测量精度。
附图说明
图1是本发明实施例中深度测量***的结构示意图。
图2是本发明实施例中深度测量***光信号发射与采集方法示意图。
图3是本发明实施例中一种深度测量方法的示意图。
图4是本发明实施例中一种***误差-占空比的示意图。
其中，11-发射模组，12-采集模组，13-控制与处理电路，20-目标物体，30-脉冲光束，121-图像传感器，40-目标物体反射的脉冲光束。
具体实施方式
为了使本发明实施例所要解决的技术问题、技术方案及有益效果更加清楚明白，以下结合附图及实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。
需要说明的是，当元件被称为“固定于”或“设置于”另一个元件，它可以直接在另一个元件上或者间接在该另一个元件上。当一个元件被称为是“连接于”另一个元件，它可以是直接连接到另一个元件或间接连接至该另一个元件上。另外，连接既可以是用于固定作用也可以是用于电路连通作用。
需要理解的是，术语“长度”、“宽度”、“上”、“下”、“前”、“后”、“左”、“右”、“竖直”、“水平”、“顶”、“底”“内”、“外”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本发明实施例和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本发明的限制。
此外，术语“第一”、“第二”仅用于描述目的，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量。由此，限定有“第一”、“第二”的特征可以明示或者隐含地包括一个或者更多该特征。在本发明实施例的描述中，“多个”的含义是两个或两个以上，除非另有明确具体的限定。
图1为本发明一实施例中深度测量***10的结构示意图。深度测量***10包括发射模组11、采集模组12以及控制与处理电路13。其中发射模组11包括光源(图中未示出)，用于向目标物体20发射功率被调制的脉冲光束30，采集 模组12包括由至少一个像素组成的图像传感器121，用于采集由目标物体20反射的脉冲光束40并生成灰度图像；控制与处理电路13用于提供光源发射脉冲光束30所需的调制信号并控制脉冲光束30的占空比和上升/下降沿时间，同时控制采集模组12采集由目标物体20反射回的脉冲光束40并生成灰度图像，基于该灰度图像以计算出脉冲光束的飞行时间和/或目标物体20的距离。
发射模组11包括光源、图案化光学元件以及光源驱动器(图中未示出)等。光源可以是发光二极管(LED)、边发射激光器(EEL)、垂直腔面发射激光器(VCSEL)等光源，也可以是多个光源组成的光源阵列，光源所发射的光束可以是可见光、红外光、紫外光等。光源在光源驱动器(其可以进一步被控制和处理电路13控制)的控制下以一定的时序被调制振幅后向目标物体20发射光束，比如光源在控制下以一定的频率发射脉冲调制光束、方波调制光束等光束。可以理解的是，可以利用控制和处理电路13中的一部分或者独立于控制和处理电路13存在的子电路来控制光源发射相关的光束。
采集模组12包括图像传感器121。图像传感器121可以是电荷耦合元件(Charge Coupled Device，CCD)、互补金属氧化物半导体(Complementary Metal-Oxide-Semiconductor Transistor，CMOS)、雪崩二极管(Avalanche Diode，AD)、单光子雪崩二极管(Single Photon Avalanche Diode，SPAD)等组成的图像传感器121。一般地，与图像传感器121连接的还包括由信号放大器、时数转换器(TDC)、模数转换器(ADC)等器件中的一种或多种组成的读出电路(图中未示出)。
在一个实施例中，ToF图像传感器121包括至少一个像素，每个像素包含四个抽头(tap，用于在相应电极的控制下存储并读取或者排出由入射光子产生的电荷信号)，在单个帧周期(或单次曝光时间内)内以一定的次序依次切换抽头以采集相应的光子，以用于接收光信号并转换成灰度数值。
控制与处理电路13用于提供光源发射脉冲光束时所需的调制信号，光源在调制信号的控制下向目标物体20发射光束。比如调制信号为连续波信号如正弦波信号，光源在该正弦波信号的调制下，向目标物体20发射脉冲光束，功率在时序上以正弦波形式变化。
可以理解的是，光源在正弦波信号的调制下，向目标物体20发射脉冲光束30，功率在时序上以正弦波形式变化，通过图像传感器121每个像素的不同抽头 采集灰度图能够计算目标物体20的距离。然而，这种调制的功率-时间波形对光源以及驱动电路要求十分苛刻，因此在实际中是以方波代替正弦波进行发射光功率的调制。对于具体的驱动电路和光源，被调制的发射波由于器件限制将变成包含上升/下降沿的梯形波，而这必然会导致发射光功率谱波形不理想引起***误差。而对于由光源发射非正弦功率谱-时间波引起的***误差(wiggling)，可以通过调节光源发射的光功率谱-时间波形来减小。一般地，光源发射的实际光功率谱波形是梯形，假设梯形波信号从最小值上升至最大值或最大值下降至最小值所用的时间相等，即上升/下降沿时间相等。因此可以通过改变光源发射光功率谱-时间的占空比来改变波形，得到占空比和上升/下降沿时间对***误差(wiggling)的影响，使得脉冲光束30的占空比和上升/下降沿时间被配置成可以降低***误差(wiggling)。
图2是根据本发明实施例的一种深度测量***光信号发射与采集方法示意图。图2中示例性给出了两个帧周期T内激光发射信号(功率谱-时间调制信号)、接收信号以及采集信号(解调信号)的时序示意图，其中各个信号的含义为：Sp表示光源的脉冲发射信号，每个脉冲发射信号表示一次脉冲光束；Sr表示脉冲光被物体反射回的反射光信号，每个反射光信号表示被目标物体20发射回相应的脉冲光束，其在时间线(图中横轴)上相对于脉冲发射信号有一定的延迟，延迟的时间t light,m是需要计算的脉冲光束的飞行时间；S1表示像素第一抽头脉冲采集的时间区间、S2表示像素的第二抽头脉冲采集的时间区间、S3表示像素的第三抽头脉冲采集的时间区间、S4表示像素的第四抽头脉冲采集的时间区间，每个脉冲采集信号表示抽头采集了该信号对应的时间段内像素所产生的电信号(电子)，并由各个抽头输出不同的灰度数值。在该实施例中，在控制与处理电路13的控制下，发射模组11向目标物体20发射脉冲光束30，该脉冲光束的上升/下降沿时间t相等，图像传感器121每个像素的四个抽头，分别用于在单个帧周期的不同时间区间内分别采集四次光信号并转换成电信号，最终输出灰度数值，以S1-S2-S3-S4的顺序依次采集0～T/4(0～90°)、T/4～T/2(90°～180°)、T/2～3T/4(180°～270°)、3T/4～T(270°～360°)时间段内的电信号，控制与处理电路13基于四个抽头采集的电信号，可根据下式计算实际光飞行时间和距离：
Figure PCTCN2020089780-appb-000003
Figure PCTCN2020089780-appb-000004
其中，L m表示图像传感器采集的灰度数值计算得到的光飞行的距离，t light,m表示由传感器采集的灰度数值计算得到的光飞行时间，c表示光速，T表示为光功率谱调制周期。同时I i，i＝0,90,180,270表示图像传感器121中单个像素不同积分时序的抽头捕获的灰度值。
可以理解的是，每个抽头的间隔时间也可以不等于T/4，抽头的初始采集时间可以为周期T内的任意时间，且抽头的数量可以为两个或三个，在此不做任何的限制。
建立一个理想模型，光源在正弦型功率-时间信号的调制下，向目标物体20发射脉冲光束，功率在时序上以正弦波形式变化，可根据公式(1)得出不包含误差的理想光飞行时间t fly，从而根据公式(2)计算不包含误差的理想光飞行距离L fly，可以理解的是，由调制的非正弦功率-时间发射光计算得到实际光飞行距离L m和由调制的正弦功率-时间发射光计算得到理想光飞行距离L fly之差即为***误差(wiggling)，因此***误差(wiggling)可根据下式计算：
Figure PCTCN2020089780-appb-000005
其中，t light.m表示由调制的非正弦功率-时间发射光计算得到的光飞行时间，t fly表示由调制的正弦功率-时间发射光计算得到的光飞行时间。
控制与处理电路13控制发射模组11发出调制的梯形功率-时间脉冲光束，假设该脉冲光束上升/下降沿时间是0％，占空比是1％，可以根据公式(3)得到该占空比和上升/下降沿时间下对应的***误差(wiggling)；多次改变实际光飞行时间t fly即改变实际光飞行距离L fly可以得到***误差(wiggling)和实际光飞行距离L fly的变化曲线，即可以得到一个极值，这个极值是实际光飞行距离L fly对应的最大***误差(wiggling)与实际光飞行距离L fly对应的最小***误差(wiggling)之差。通过改变脉冲光束的占空比，该占空比的范围为1～99％，可以得到在0％的上升/下降沿时间下不同占空比所对应的极值变化曲线，进而可以得到一个最优占空比(该占空比下所对应的极值最小)。
同样地，假设该脉冲光束的上升/下降沿时间为1％，通过改变脉冲光束的占 空比，该占空比的范围为1～99％，也可以得到在1％的上升/下降沿时间下不同占空比所对应的极值变化曲线，即也可以得到一个最优占空比。
可以理解的是，发射脉冲光束的上升/下降沿时间不同，通过改变脉冲光束的占空比，可以得到各个上升/下降沿时间下不同占空比所对应的极值变化曲线，进而可以得到各个上升/下降沿时间下相应的最优占空比。对于某一固定的上升/下降沿时间，脉冲光束的最优占空比所对应的极值最小，即在该上升/下降沿时间-占空比配置下所产生的***误差最小。因此，可以通过控制发射脉冲光束30的占空比和上升/下降沿时间降低***误差(wiggling)。
在一个实施例中，脉冲光束30的占空比和上升/下降沿时间被配置成以满足关系式使得***误差(wiggling)最小：
Figure PCTCN2020089780-appb-000006
其中，t rise/fall表示上升/下降沿时间，DR表示占空比，T表示所述脉冲光束的调制周期，B表示一个数值代号，在B∈(1.9334,2.1334)内取值。
图3为本申请一实施例中一种深度测量方法的流程图，包括如下步骤：
S301，控制发射模组向目标物体发射功率-时间波形被调制的脉冲光束；
具体地，发射模组包括光源，用于向目标物体20发出功率-时间被调制的脉冲光束30，该脉冲光束30的占空比和上升/下降沿时间被配置成以降低***误差。
在一个实施例中，相互匹配包括：在所述上升/下降沿时间固定的情况下，所述脉冲光束的占空比配置为最优占空比，所述最优占空比为极值最小的占空比，所述极值是实际光飞行距离对应的最大***误差与实际光飞行距离对应的最小***误差之差。
在一个实施例中，脉冲光束30的占空比和上升/下降沿时间被配置成以满足关系式：
Figure PCTCN2020089780-appb-000007
其中，t rise/fall表示上升/下降沿时间，DR表示占空比。
S302，控制采集模组采集所述目标物体反射的脉冲光束并生成灰度图像；
具体地，采集模组12包括由至少一个像素组成的图像传感器121，每个像素包括四个抽头，抽头用于采集由目标物体20反射回的脉冲光束40并输出灰度数值。
S303，提供所述发射模组发射所述脉冲光束所需的调制信号，其中，所述脉冲光束的占空比和所述上升/下降沿时间相互匹配用于降低***误差；同时控制所述采集模组接收所述脉冲光束，基于所述灰度图像计算出所述脉冲光束的飞行时间和/或所述目标物体的距离。
上述深度测量的方法原理与上述深度测量***的原理相同，在此不再赘述。
如图4所示，是本发明一种深度测量***中***误差-占空比的示意图，从图中可以得到，占空比约在34％左右时，***误差的极大值与极小值之差最小(12mm)，比50％的占空比对应的***误差极值之差(38mm)小26mm。同时***误差极值之差与占空比的变化关系符合理论预测，且最优占空比与上升/下降沿时间的关系满足理论关系。故可以通过脉冲光束的占空比和上升/下降沿时间相互匹配用于降低***误差。
以上内容是结合具体的优选实施方式对本发明所做的进一步详细说明，不能认定本发明的具体实施只局限于这些说明。对于本发明所属技术领域的技术人员来说，在不脱离本发明构思的前提下，还可以做出若干等同替代或明显变型，而且性能或用途相同，都应当视为属于本发明的保护范围。

Claims (10)

  1. 一种深度测量***，其特征在于，包括：
    发射模组，包括光源，用于向目标物体发射功率-时间波形被调制的脉冲光束；
    采集模组，包括由至少一个像素组成的图像传感器，用于采集由所述目标物体反射的脉冲光束并生成灰度图像；
    控制与处理电路，用于提供所述光源发射所述脉冲光束所需的调制信号并控制脉冲光束的占空比和上升/下降沿时间，同时控制所述采集模组接收所述脉冲光束，基于所述灰度图像计算出所述脉冲光束的飞行时间和/或所述目标物体的距离；
    所述脉冲光束的占空比和所述上升/下降沿时间相互匹配用于降低***误差。
  2. 如权利要求1所述的深度测量***，其特征在于，所述相互匹配包括：在所述上升/下降沿时间固定的情况下，所述脉冲光束的占空比配置为最优占空比，所述最优占空比为极值最小的占空比，所述极值是实际光飞行距离对应的最大***误差与实际光飞行距离对应的最小***误差之差。
  3. 如权利要求1所述的深度测量***，其特征在于，所述占空比的范围是1～99％。
  4. 如权利要求1所述的深度测量***，其特征在于，所述脉冲光束的占空比和所述上升/下降沿时间被配置成满足关系式：
    Figure PCTCN2020089780-appb-100001
    其中，t rise/fall表示上升/下降沿时间，DR表示占空比，T表示所述脉冲光束的调制周期，B表示一个数值代号。
  5. 如权利要求1所述的深度测量***，其特征在于，每个所述像素包括四个抽头，所述抽头用于在单个帧周期内的不同时间段分别采集由所述目标物体反射的脉冲光束所产生的电信号。
  6. 如权利要求5所述的深度测量***，其特征在于，四个所述抽头采集间隔的时间为T/4，所述抽头的初始采集时间为T内的任意时间，所述T是所述脉冲光束的调制周期。
  7. 一种深度测量方法，其特征在于，包括如下步骤：
    S1：控制发射模组向目标物体发射功率-时间波形被调制的脉冲光束；
    S2：控制采集模组采集所述目标物体反射的脉冲光束并生成灰度图像；
    S3：提供所述发射模组发射所述脉冲光束所需的调制信号，其中，所述脉冲光束的占空比和上升/下降沿时间相互匹配用于降低***误差；同时控制所述采集模组接收所述脉冲光束，基于所述灰度图像计算出所述脉冲光束的飞行时间和/或所述目标物体的距离。
  8. 如权利要求7所述的深度测量方法，其特征在于，所述相互匹配包括：在所述上升/下降沿时间固定的情况下，所述脉冲光束的占空比配置为最优占空比，所述最优占空比为极值最小的占空比，所述极值是实际光飞行距离对应的最大***误差与实际光飞行距离对应的最小***误差之差。
  9. 如权利要求7所述的深度测量方法，其特征在于，所述占空比的范围是1～99％。
  10. 如权利要求7所述的深度测量方法，其特征在于，所述脉冲光束的占空比和所述上升/下降沿时间被配置成满足关系式：
    Figure PCTCN2020089780-appb-100002
    其中，t rise/fall表示上升/下降沿时间，DR表示占空比，T表示所述脉冲光束的调制周期，B表示一个数值代号。
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