WO2021248273A1 - 基于飞行时间的测距方法和相关测距*** - Google Patents

基于飞行时间的测距方法和相关测距*** Download PDF

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Publication number
WO2021248273A1
WO2021248273A1 PCT/CN2020/094918 CN2020094918W WO2021248273A1 WO 2021248273 A1 WO2021248273 A1 WO 2021248273A1 CN 2020094918 W CN2020094918 W CN 2020094918W WO 2021248273 A1 WO2021248273 A1 WO 2021248273A1
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WIPO (PCT)
Prior art keywords
ratio
time
brightness information
pixels
sampling
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PCT/CN2020/094918
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English (en)
French (fr)
Inventor
李宗德
王浩任
杨孟达
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深圳市汇顶科技股份有限公司
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Priority to EP20923682.7A priority Critical patent/EP3955025A4/en
Priority to PCT/CN2020/094918 priority patent/WO2021248273A1/zh
Priority to US17/472,158 priority patent/US20210405166A1/en
Publication of WO2021248273A1 publication Critical patent/WO2021248273A1/zh

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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
    • 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
    • G01S7/486—Receivers
    • G01S7/4861—Circuits for detection, sampling, integration or read-out
    • G01S7/4863—Detector arrays, e.g. charge-transfer gates
    • 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
    • G01S17/894—3D imaging with simultaneous measurement of time-of-flight at a 2D array of receiver pixels, e.g. time-of-flight cameras or flash lidar
    • 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
    • G01S7/486—Receivers
    • G01S7/4865—Time delay measurement, e.g. time-of-flight measurement, time of arrival measurement or determining the exact position of a peak
    • 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
    • G01S7/486—Receivers
    • G01S7/4868—Controlling received signal intensity or exposure of sensor
    • 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
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/06—Systems determining position data of a target
    • G01S13/08—Systems for measuring distance only
    • G01S13/10—Systems 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
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/89—Radar or analogous 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
    • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/02—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems using reflection of acoustic waves
    • G01S15/06—Systems determining the position data of a target
    • G01S15/08—Systems for measuring distance only
    • G01S15/10—Systems 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
    • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/88—Sonar systems specially adapted for specific applications
    • G01S15/89—Sonar systems specially adapted for specific applications for mapping or imaging

Definitions

  • This application relates to distance measurement and depth sensing technology, and more particularly to a distance measurement method based on flight time, and a related distance measurement system.
  • pulse modulation measures the distance of the target through the time difference between the transmission and reception of optical pulses, and has a relatively simple measurement mechanism.
  • HDR high dynamic range
  • An embodiment of the present application discloses a time-of-flight-based ranging method, including: intermittently sending multiple pulses from a pulse generating unit, wherein the multiple pulses are reflected by a target to generate multiple reflected signals;
  • the time-of-flight sensor allows the plurality of reflected signals of each pixel in the plurality of pixels in the time-of-flight sensor to perform the first signal sampling for a first predetermined time and the second ratio of the reflected signals.
  • a plurality of reflection signals are performed for a second predetermined time to perform second signal sampling to generate a plurality of sampling results corresponding to the plurality of pixels, wherein the start time point of the first predetermined time and the corresponding transmission time of the pulse Point has a first time difference, and the start time point of the second predetermined time and the corresponding sending time point of the pulse have a second time difference, and the first time difference is smaller than the second time difference, and the first The signal samples correspond to the first depth range, and the second signal samples correspond to the second depth range; according to the multiple sampling results, multiple depth information and multiple brightness information corresponding to the multiple pixels are obtained; and according to the The plurality of depth information and the plurality of brightness information adjust the first ratio and the second ratio.
  • a time-of-flight-based ranging system including: a pulse generating unit; a control circuit, coupled to the pulse generating unit, for controlling the pulse generating unit to intermittently send multiple Pulses, and adjusting the first ratio and the second ratio according to a plurality of depth information and a plurality of brightness information, wherein the plurality of pulses are reflected by the target to generate a plurality of reflected signals; and a time-of-flight sensor including a plurality of pixels , The time-of-flight sensor is controlled by the control circuit to allow each pixel in the plurality of pixels to the first ratio of the plurality of reflection signals to the first predetermined time to perform the first Signal sampling, and performing second signal sampling on the plurality of reflected signals of the second ratio for a second predetermined time to generate a plurality of sampling results corresponding to the plurality of pixels, wherein the first predetermined time The starting time point of the pulse and the corresponding sending time point of the pulse have a first time difference, and the
  • the time-of-flight-based ranging method and related ranging system disclosed in this application can separately adjust the ratio of signal sampling taken for different distances by comprehensively considering depth information and brightness information, so as to improve the performance of high dynamic range sampling.
  • Fig. 1 is a functional block diagram of an embodiment of a distance measurement system based on flight time according to the present application
  • Fig. 2 is a schematic diagram of an embodiment of the circuit structure of a single pixel in the pixel array of the distance measuring system shown in Fig. 1;
  • FIG. 3 is a schematic diagram of an embodiment of signal timing involved in the pixel shown in FIG. 2;
  • FIG. 4 is a schematic diagram of another embodiment of signal timing involved in the pixel shown in FIG. 2;
  • 5 is a distribution histogram of a plurality of first pixels at brightness 0 to 11 and a distribution histogram of a plurality of second pixels at brightness 0 to 11 before adjusting the first ratio and the second ratio;
  • FIG. 6 is a distribution histogram of a plurality of first pixels at brightness 0 to 11 and a distribution histogram of a plurality of second pixels at brightness 0 to 11 after adjusting the first ratio and the second ratio;
  • Fig. 7 is a schematic diagram of pulses with phases of 0 degrees, 90 degrees, 180 degrees, and 270 degrees.
  • first and second features are in direct contact with each other; and may also include
  • additional elements/components are formed between the above-mentioned first and second features, so that the first and second features may not be in direct contact.
  • content of this application may reuse component symbols and/or labels in multiple embodiments. Such repeated use is based on the purpose of brevity and clarity, and does not in itself represent the relationship between the different embodiments and/or configurations discussed.
  • spatially relative terms here such as “below”, “below”, “below”, “above”, “above” and similar, may be used to facilitate the description of the drawing in the figure The relationship between one component or feature relative to another component or feature is shown.
  • the original meaning of these spatially-relative vocabulary covers not only the orientation shown in the figure, but also the various orientations in which the device is in use or operation.
  • the device may be placed in other orientations (for example, rotated 90 degrees or in other orientations), and these spatially-relative description vocabulary should be explained accordingly.
  • the present application can comprehensively consider depth information and brightness information when performing distance measurement based on flight time, and adjust the ratio of signal sampling taken for different distances respectively, so as to avoid the problem of overexposure or overdarkness caused by blind configuration.
  • Fig. 1 is a functional block diagram of an embodiment of a distance measurement system based on flight time according to the present application.
  • the ranging system 100 can be used to detect the distance between the target 102 and the ranging system 100. It should be noted that the distance between the target 102 and the ranging system 100 should be less than or equal to the maximum measurement distance of the ranging system 100.
  • the ranging system 100 may be a three-dimensional imaging system or a depth sensing system, which may use a time-of-flight method to measure the distance or depth of the surrounding target, thereby obtaining depth of field and three-dimensional image information .
  • the ranging system 100 can be implemented as a variety of different types of time-of-flight ranging systems, such as a time-of-flight-based optical ranging system, a time-of-flight-based acoustic ranging system, and a time-of-flight-based radar ranging system. , Or other types of time-of-flight ranging systems.
  • the distance measurement system 100 is implemented as an embodiment of an optical distance measurement system to illustrate the time-of-flight distance measurement solution of the present application.
  • the time-of-flight ranging solution of the present application can be applied to any time-of-flight ranging system.
  • the ranging system 100 may include (but is not limited to) a pulse generating unit 110, a control circuit 120, and a time-of-flight sensor 130.
  • the pulse generating unit 110 is used to send pulses intermittently, and has a pulse length T. After sending a pulse, the pulse generating unit 110 will stop sending the pulse for a period of time, and this period of time can be much longer or longer than the pulse length T. Until the next startup, the pulse generating unit 110 can send a pulse again.
  • the ranging system 100 may be an optical ranging system based on time of flight. Therefore, the pulse generating unit 110 may be implemented by a light pulse generating unit to generate a pulsed light signal EL.
  • the pulsed light signal EL may be a single light pulse that is generated intermittently. That is, the light pulse generating unit may intermittently send a single light pulse as a single pulse generated by the pulse generating unit 110 intermittently.
  • the pulse generating unit 110 may include (but is not limited to) a driving circuit and a light emitting unit (not shown in FIG. 1). The driving circuit is used to drive the light-emitting unit so that the light-emitting unit emits a single light pulse intermittently.
  • the light-emitting unit may be (but not limited to) a semiconductor laser (also known as a laser diode (LD)), a light-emitting diode (Light Emitting Diode, LED) or other light-emitting unit that can generate light pulses.
  • a semiconductor laser also known as a laser diode (LD)
  • LD laser diode
  • LED Light Emitting Diode
  • the semiconductor laser The generated light pulse is coherent light, and the light pulse generated by the light emitting diode is incoherent light.
  • the pulse generating unit 110 may generate other types of pulses, such as acoustic wave pulses or electromagnetic wave pulses.
  • the pulse generating unit 110 may be implemented by an acoustic wave pulse generator.
  • the sonic pulse generator is used to intermittently send a single sonic pulse (such as an ultrasonic pulse) as a single pulse generated by the pulse generating unit 110 intermittently.
  • the pulse generating unit 110 may be implemented by an electromagnetic wave pulse generator.
  • the electromagnetic wave pulse generator is used to intermittently send a single electromagnetic wave pulse as a single pulse generated by the pulse generating unit 110 intermittently.
  • the control circuit 120 is coupled to the pulse generating unit 110 for controlling the pulse generating unit 110 to generate a pulsed light signal EL.
  • the control circuit 120 may control the pulse generating unit 110 to send a single light pulse intermittently.
  • the control circuit 120 may control the driving circuit included in the pulse generating unit 110 so that the light emitting unit included in the driving circuit driving the pulse generating unit 110 sends a single light pulse intermittently.
  • the time-of-flight sensor 130 is controlled by the control circuit 120 to sample a reflected signal RL to detect the distance between the ranging system 100 (or the time-of-flight sensor 130) and the target 102, wherein the reflected signal RL is pulsed light
  • the signal EL is generated by being reflected by the target 102.
  • the control circuit 120 may be the main control unit in the terminal device and need not be included in the ranging system 100.
  • the time-of-flight sensor 130 continuously performs multiple signal sampling according to a sampling time interval within the adjustable predetermined time TR (for the convenience of description, represented by a waveform marked with a time length TR) to generate reflections
  • the sampling result of the signal RL in other words, the reflected signal RL arriving at the time-of-flight sensor 130 within the predetermined time TR can be sensed.
  • the predetermined time TR is set to be greater than or equal to the pulse length T, for example, greater than or equal to The pulse length T is several times, so that the reflected signal RL from near and far can be captured, but the disadvantage is that the amount of information received from near is often far more than the amount of information from far, resulting in far The amount of information is easily affected by the background light, causing shot noise. Therefore, the predetermined time TR in this application is adjustable, and the details are described later.
  • the time-of-flight sensor 130 may calculate the phase shift between the reflected signal RL and the pulsed light signal EL sent by the pulse generating unit 110 according to the sampling result .
  • the time-of-flight sensor 130 may include (but is not limited to) a pixel array 132 and a processing circuit 134.
  • the pixel array 132 includes a plurality of pixels, and each pixel may include a photosensor to generate a photo response signal (photo response signal) according to the reflection signal RL.
  • the control circuit 120 can enable the photosensor of each pixel to selectively output the corresponding light response signal of each pixel to the processing circuit 134.
  • the light sensor may be a photodiode.
  • the processing circuit 134 can sample the light response signal output by each pixel at intervals of the sampling time interval in a predetermined time TR according to a sampling control signal SC, and generate a sampling result SR accordingly.
  • the sampling control signal SC can be controlled
  • the circuit 120 is generated.
  • the processing circuit 134 may perform signal processing on the sampling result SR, such as mixing processing and discrete Fourier transform, to calculate the amplitude of the reflected signal RL received by each pixel (that is, the brightness information LI), And the phase shift between the reflected signal RL received by each pixel and the pulsed light signal EL sent by the pulse generating unit 110, thereby detecting the flight time of the pulsed light signal EL, and calculating the target 102 and the reference according to the flight time
  • the distance of the position that is, the depth information DI
  • the reference position may be (but is not limited to) the position of the ranging system 100.
  • FIG. 2 is a schematic diagram of an embodiment of the circuit structure of a single pixel in the pixel array 132 shown in FIG. 1. Please refer to Figure 2 together with Figure 1.
  • the pixel 332 includes (but is not limited to) a photosensor PD, a first readout circuit (such as a photoelectric readout circuit) 333, and a second readout circuit (such as a photoelectric readout circuit) 334.
  • the light sensor PD (such as a photodiode) is used for light sensing operation.
  • the photosensor PD can sense the reflected signal RL to correspondingly generate a photo response signal PR, where the photo response signal PR can be output by at least one of the first readout circuit 333 and the second readout circuit 334.
  • the photosensor PD can convert the received light signal into a photocurrent signal of a corresponding size, that is, the photoresponse signal PR can be a current signal that characterizes the magnitude of the light signal, and the first readout circuit 333/second readout The output circuit 334 is used to read the photocurrent signal.
  • the first readout circuit 333 can selectively transmit the light response signal PR generated by the photosensor PD according to a first control signal TX1 to generate a first pixel output PO1, wherein the first control signal TX1 can be provided by the control circuit 120 .
  • the pixel 332 can selectively transmit the light response signal PR to the processing circuit 130 through the first readout circuit according to the first control signal TX1 to generate the first pixel output PO1 and output it to the processing circuit 130.
  • the second readout circuit 334 can selectively transmit the light response signal PR generated by the photosensor PD according to a second control signal TX2 to generate a second pixel output PO2, wherein the second control signal TX2 can be provided by the control circuit 120 , And have a different phase from the first control signal TX1.
  • the phase difference between TX1 and TX2 is 180°.
  • the pixel 332 can selectively transmit the photoresponse signal PR to the processing circuit 130 through the second readout circuit according to the second control signal TX2 to generate a second pixel output PO2 and output it to the processing circuit 130.
  • the first control signal TX1 and the second control signal TX2 can be provided by the control circuit 120 shown in FIG. 1.
  • the first readout circuit 333 may include (but is not limited to) a first reset transistor MR1, a first transfer transistor MT1, a first output transistor MF1, and a first read transistor MW1.
  • the second readout circuit 334 includes (but is not limited to) a second reset transistor MR2, a second transfer transistor MT2, a second output transistor MF2, and a second read transistor MW2.
  • the first reset transistor MR1 and the second reset transistor MR2 both reset a first floating diffusion node FD1 and a second floating diffusion node FD2 according to a reset signal RST, wherein the reset signal RST can be provided by the control circuit 120.
  • the first transfer transistor MT1 and the second transfer transistor MT2 are both coupled to the photosensor PD, and are turned on according to the first control signal TX1 and the second control signal TX2 respectively, that is, the first transfer transistor MT1 and the second transfer transistor MT2 are respectively subjected to It is controlled by the first control signal TX1 and the second control signal TX2 to realize the connection and disconnection with the photosensor PD.
  • the first output transistor MF1 and the first output transistor MF2 are respectively used to amplify the voltage signals of the first floating diffusion node FD1 and the second floating diffusion node FD2 to generate a first pixel output PO1 and a second pixel output PO2, respectively.
  • the first reading transistor MW1 and the second reading transistor MW2 both selectively output the first pixel output PO1 and the second pixel output PO2 according to a selection signal SEL, wherein the selection signal SEL can be provided by the control circuit 120.
  • FIG. 3 is a schematic diagram of an embodiment of signal timing related to the pixel 332 shown in FIG. 2.
  • the pulse generating unit 110 sends a total of two pulses PE.
  • the sensor 130 will sample twice. The two sampling methods are roughly the same, but the time points are different, so that the previous sample can be used for the reflected signal RL.
  • the part that is reflected to the sensor 130 faster is sampled, and the latter sampling can be performed for the part of the reflected signal RL that is reflected to the sensor 130 slowly.
  • the first pulse PE after the first pulse PE is emitted at time t1, it is reflected to become the reflected signal RL, because the reflected signal RL carries the energy reflected back from different depths by the first pulse PE , The energy reflected from near will reach the pixel 332 faster than the energy reflected from far away. That is to say, in theory, any time after the time point t1 may have the energy of the reflected signal RL of the first pulse PE (please refer to the indication of the reflected signal RL after the time point t1 in FIG. 3).
  • the length of the predetermined time TR for each sampling can be increased, so that the amount of information sampled corresponds to a wider depth range. However, the information reflected from the distance will be far away from the sampled information. Is less than the information reflected from near, which makes the information reflected from far away susceptible to noise interference.
  • different target depth ranges are sampled for different pulse PEs.
  • the control circuit 120 causes the sensor 130 to sample the first signal within the time range of the predetermined time TR1; for the second pulse PE in FIG. 3, the control circuit 120 causes the sensor 130 to The second signal sampling is performed within the time range of the predetermined time TR2.
  • the predetermined time TR1 is later than the emission time of the first pulse PE by the first time difference tX
  • the predetermined time TR2 is later than the emission time of the second pulse PE by the first time difference tX+2TN
  • the predetermined time TR1 and the predetermined time TR2 The length is the same.
  • the first signal sampling can sample the energy of the first pulse PE reflected back to the sensor 130 in the predetermined time TR1; the second signal sampling can sample the second pulse in the predetermined time TR2
  • the PE reflects the energy back to the sensor 130 from a far distance, and the target sampling depths of the two are different and do not repeat.
  • multiple pulses PE are emitted (for example, thousands of times), and the first signal sampling or the second signal sampling is performed according to the predetermined time TR1 or the predetermined time TR2.
  • the pulse PE of the first proportion in the multiple pulses PE may correspond to the first signal sample
  • the pulse PE of the second proportion in the multiple pulse PE may correspond to the second signal sample, for example, according to
  • the first ratio and the second ratio are such that the number of pulses PE corresponding to the first signal sampling is less than the number of pulses PE corresponding to the second signal sample, so as to balance the energy from near and far, so that The energy from near will not be overexposed, and it will pull up the energy from far away.
  • the pulse PE corresponds to the second signal sample to sample the remote information; the remaining 20% of the pulse PE corresponds to the first signal sample to sample the incoming information.
  • the first ratio and the second ratio can be adjusted independently, and the detailed adjustment method will be described later.
  • the first time difference tX in FIG. 3 can be set to, for example, half of the pulse length T, but the application is not limited thereto.
  • the difference between the first time difference and the second time difference can also be greater or less than the two sampling intervals TN, but should not be less than the sampling interval TN.
  • the predetermined time TR1 may include two sampling intervals TN (that is, time point t2 to time point t4 and time point t4 to time point t6); the predetermined time TR2 may include two sampling intervals TN (that is, time point t10 to time point t12 and time point From point t12 to time point t14), the time length of each sampling interval TN is equal to the pulse length T.
  • the first control signal TX1 has the same waveform in each sampling interval TN; the second control signal TX2 has the same waveform in each sampling interval TN. There may be a 180 degree phase difference between the second control signal TX2 and the first control signal TX1.
  • the length of the predetermined time can be adjusted according to the required dynamic range, and the target depth ranges for different types of signal sampling can also overlap with each other.
  • the predetermined time TR3 can be used for the third signal sampling, the predetermined time TR3 can include 4 sampling intervals TN, for example, the predetermined time TR3 starts from the time point t2 and lasts for 4 sampling intervals TN, so the predetermined time TR3 can also include The dynamic range for the predetermined time TR1 and the predetermined time TR2.
  • the target depth range of the third signal sample is the set of the first signal sample and the second signal sample.
  • multiple pulse PEs can be arbitrarily used to correspond to different types of signal samples according to the requirements of the dynamic range, and the number of types of signal samples is not limited. For example, in some embodiments, it can be based on the first ratio and The second ratio is such that 15% of the pulse PE corresponds to the third signal sample, and 85% of the pulse PE corresponds to the second signal sample, because the target depth range of the third signal sample completely includes the first signal sample.
  • the signal sampling and the second signal sampling are therefore essentially equivalent to making 15% of the pulse PE correspond to the first signal sampling, and 100% of the pulse PE corresponding to the second signal sampling; or making 10% of the pulse PE correspond to For the first signal sampling, 10% of the pulse PE corresponds to the third signal sample, and 80% of the pulse PE corresponds to the second signal sample, which is essentially equivalent to 20% of the pulse PE corresponding to the first signal sample , 90% of the pulse PE corresponds to the second signal sample.
  • each pixel is sampled once every sampling time interval in each sampling interval TN, where the sampling time interval may be a quarter of the pulse length T.
  • the sampling time interval may also be one-eighth or one-sixteenth of the pulse length T.
  • the first signal sample in FIG. 3 can be sampled at the predetermined time TR1 until the energy of the first pulse PE reflected back to the sensor 130 from a closer place; the second signal sample can be sampled at the predetermined time TR2
  • the second pulse PE is sampled in the middle to reflect the energy back to the sensor 130 from a far distance, and the target sampling depths of the two are different and do not repeat.
  • the first signal sample corresponds to a first depth range
  • the distance ranging system 100 is a depth range of 5 to 10 meters
  • the second signal sample corresponds to a second depth range, such as distance ranging
  • the system 100 has a depth range of 10 to 20 meters.
  • the ranging system 100 When the ranging system 100 has not yet known any information about the scene in which the ranging is to be performed, it will first use the preset first ratio and second ratio to perform the first signal sampling and the second signal sampling.
  • the preset first ratio and second ratio can be set completely based on the depth range.
  • the first signal sampling is for sampling at a short distance
  • the second signal sampling is for sampling at a long distance.
  • the preset first ratio and second ratio will give the second signal more samples. But to be precise, such a configuration is not necessarily correct. For example, in a scene where distance measurement is desired, long-distance objects have very high brightness, while close objects have very low brightness.
  • the processing circuit 134 obtains the sampling result of each pixel from the pixel array 132 and calculates the value of each pixel.
  • the depth information DI and the brightness information LI are transmitted to the control circuit 120, and the control circuit 120 can adjust the first ratio and the second ratio according to the depth information DI and the brightness information LI.
  • the control circuit 120 classifies each pixel into a first pixel and a second pixel according to the depth information DI of each pixel, corresponding to the first depth range or the second depth range, respectively.
  • pixels with depth information DI falling in the first depth range will be classified as the first pixel; pixels with depth information DI falling in the second depth range will be classified as the second pixel Pixels.
  • the control circuit classifies the brightness information LI carried by the first pixel as first brightness information, and classifies the brightness information LI carried by the second pixel as second brightness information.
  • the first ratio can be adjusted to the highest, that is, the second signal sampling can be completely ignored. Conversely, if all pixels belong to the second pixel, the second ratio is adjusted to the highest.
  • the control circuit 120 will determine whether to emphasize or reduce the proportion of the first signal sample according to the brightness information LI of each first pixel;
  • the brightness information LI of the second pixel is used to determine whether to emphasize or reduce the proportion of the second signal sample.
  • the control circuit 120 performs statistics on the brightness information LI of each first pixel. For example, according to the brightness information LI of each first pixel, each first pixel is corresponding to a predetermined number of brightness intervals. One of them, as shown in the upper graph of Figure 5, there are 12 continuous and non-overlapping intervals, representing brightness from 0 to 11. Then, according to the brightness information LI of each first pixel, count how many first intervals each interval corresponds to. Pixels, and get a statistical histogram. Similarly, the lower graph of FIG. 5 represents a statistical histogram of the brightness information LI of each second pixel.
  • Table 1 shows the distribution number of multiple first pixels at brightness 0-11;
  • Table 2 shows the distribution number of multiple second pixels at brightness 0-11.
  • the statistical histogram of the brightness information LI of each first pixel shows that the first signal is oversampled according to the preset first ratio and second ratio. Exposure tendency, that is, the proportion of pixels with high brightness is too high; and according to the situation shown in Table 2 and the lower diagram in Figure 5, the statistical histogram of the brightness information LI of each second pixel is displayed, according to the preset The sampling of the second signal at the first ratio and the second ratio tends to be underexposed (too dark), that is, the ratio of pixels with low brightness is too high.
  • the control circuit 120 can set a number of preset reference values as a basis for determining whether to adjust the first ratio and the second ratio. For example, when the proportion of the plurality of first brightness information exceeding the first critical value is higher than the first preset value (for example, 10% of the total number), the first proportion is reduced; when the plurality of second brightness information The ratio of exceeding the first threshold value is higher than the first preset value, and the second ratio is reduced; when the ratio of the plurality of first brightness information that is lower than the second threshold value is higher than the second preset value Setting a value to increase the first ratio; and when the ratio of the plurality of second brightness information exceeding the second critical value is higher than the second preset value, the second ratio is increased.
  • the first preset value for example, 10% of the total number
  • the first critical value is brightness 9
  • the second critical value is brightness 2
  • the first preset value and the second preset value are both 10% of the total number.
  • the value exceeding brightness 9 The number of first pixels is 230, which accounts for about 49% of the total number 470. Therefore, the control circuit 120 determines that the first ratio needs to be reduced; and according to Table 2, the number of first pixels lower than brightness 2 is 200, accounting for about 53% of the total number 375, so the control circuit 120 determines that the second ratio needs to be increased.
  • control circuit 120 can also use other mechanisms to calculate the statistical values of Table 1 and Table 2 to determine how to adjust the first ratio and the second ratio, for example, it can also directly calculate all the statistical values. If the average brightness of the pixel is higher than the third critical value, the proportion of corresponding signal samples is reduced, and if it is lower than the fourth critical value, the proportion of corresponding signal samples is increased.
  • the third critical value is a brightness of 8 and the second critical value is a brightness of 1, then according to Table 3, the average value of the 470 pixel brightness is 9, so the control circuit 120 determines that the first ratio needs to be reduced; In Table 2, the average brightness of the 470 pixels is 1.6, so the control circuit 120 determines that the second ratio needs to be increased.
  • the control circuit 120 can update the first ratio and the second ratio, so that the results obtained by the subsequent ranging operation are more balanced.
  • the brightness of each first pixel The statistical histogram of the information LI shows that the first signal sampling based on the first ratio and the second ratio adjusted by the control circuit 120 has not been overexposed or underexposed, that is, the proportion of pixels with moderate brightness is the highest;
  • the statistical histogram of the brightness information LI of each second pixel shows that the second signal sampling based on the first ratio and the second ratio adjusted by the control circuit 120 is no longer Overexposure or underexposure, that is, the proportion of pixels with moderate brightness is the highest.
  • control circuit 120 may update the first ratio and the second ratio in real time according to the depth information DI and the brightness information LI transmitted from the processing circuit 134. In some embodiments, the control circuit 120 may also update the first ratio and the second ratio only once and continue to use them until the ranging operation ends. In addition, when there are more than two types of signal samples, the above-mentioned method can also be used to set the ratio of multiple types of signal samples.
  • the pulse generating unit 110 will intermittently send a plurality of pulses PE with a phase of 0 degrees, and then intermittently send a plurality of pulses PE with a phase of 90 degrees. Intermittently send a plurality of pulses PE with a phase of 180 degrees, and then intermittently send a plurality of pulses PE with a phase of 270 degrees. Since the four-phase pulse PE has a phase difference between each other, that is, the time when the reflected signal RL reaches the pixel array 132 is inherently different.
  • the signal sampling configuration method designed for the 0 degree pulse PE is used (such as for 0
  • the optimized first ratio and second ratio obtained by the pulse PE of 90 degrees) are used in the pulse PE of 90, 180 or 270 degrees, and the effect will be compromised. Therefore, in an embodiment of the present application, signal sampling configurations are calculated for pulse PEs of different phases. For example, for pulse PEs of 90, 180, and 270 degrees, the first ratio and the second ratio are respectively found according to the aforementioned method.

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Abstract

一种基于飞行时间的测距方法和基于飞行时间的测距***。测距方法包括：从脉冲产生单元(110)间歇性地发送多个脉冲（PE)，其中多个脉冲被目标物(102)反射而产生多个反射信号(RL)；使飞行时间传感器(100)让飞行时间传感器(100)中的多个像素中各像素对第一比例的多个反射信号(RL)持续第一预定时间来执行第一信号采样，以及对第二比例的多个反射信号(RL)持续第二预定时间来执行第二信号采样，以产生对应多个像素的多个采样结果(SR)；根据多个采样结果(SR)，得到对应多个像素的多个深度信息(DI)和多个亮度信息(LI)；以及依据多个深度信息(DI)和多个亮度信息(LI)调整分配第一比例和第二比例。

Description

基于飞行时间的测距方法和相关测距*** 技术领域
本申请涉及测距和深度传感技术，尤其涉及一种基于飞行时间的测距方法，及其相关的测距***。
背景技术
基于飞行时间(time of flight，TOF)的距离测量技术中，脉冲调制(pulse modulation)通过光脉冲发送和接收的时间差来测量目标物的距离，具备了较简单的测量机制。然而，在高动态范围(high dynamic range,HDR)的应用中，现有的技术对于近距离过曝与远距离信号量不足的问题，仍有相当大的改善空间。因此，如何在进行基于飞行时间的距离测量时，使远近距离的信号量能尽量的达到平衡，已成为本领域亟需解决的问题之一。
发明内容
本申请的一实施例公开了一种基于飞行时间的测距方法，包括：从脉冲产生单元间歇性地发送多个脉冲，其中所述多个脉冲被目标物反射而产生多个反射信号；使飞行时间传感器让所述飞行时间传感器中的多个像素中各像素对第一特并比例的所述多个反射信号持续第一预定时间来执行第一信号采样，以及对第二比例的所述多个反射信号持续第二预定时间来执行第二信号采样，以产生对应所述多个像素的多个采样结果，其中所述第一预定时间的开始时间点和对应的所述脉冲的发送时间点具有第一时间差，以及所述第二预定时间的开始时间点和对应的所述脉冲的发送时间点具有第二时间差，且所述第一时间差小于所述第二时间差，以及所述第一信号采 样对应第一深度范围，所述第二信号采样对应第二深度范围；根据所述多个采样结果，得到对应所述多个像素的多个深度信息和多个亮度信息；以及依据所述多个深度信息和所述多个亮度信息调整所述第一比例和所述第二比例。
本申请的另一实施例公开了一种基于飞行时间的测距***，包括：脉冲产生单元；控制电路，耦接于所述脉冲产生单元，用以控制所述脉冲产生单元间歇性地发送多个脉冲，以及依据多个深度信息和多个亮度信息调整第一比例和第二比例，其中所述多个脉冲被目标物反射而产生多个反射信号；以及飞行时间传感器，包括具有多个像素的像素阵列，所述飞行时间传感器由所述控制电路所控制，用以让所述多个像素中各像素对所述第一比例的所述多个反射信号持续第一预定时间来执行第一信号采样，以及对所述第二比例的所述多个反射信号持续第二预定时间来执行第二信号采样，以产生对应所述多个像素的多个采样结果，其中所述第一预定时间的开始时间点和对应的所述脉冲的发送时间点具有第一时间差，以及所述第二预定时间的开始时间点和对应的所述脉冲的发送时间点具有第二时间差，且所述第一时间差小于所述第二时间差，以及所述第一信号采样对应第一深度范围，所述第二信号采样对应第二深度范围，所述飞行时间传感器并根据所述多个采样结果，得到对应所述多个像素的所述多个深度信息和所述多个亮度信息。
本申请所公开的基于飞行时间的测距方法及相关测距***可以通过综合考虑深度信息和亮度信息，来分别调整针对不同距离所采取的信号采样的比例，来提升高动态范围采样的效能。
附图说明
图1是本申请基于飞行时间的测距***的一实施例的功能方框示意图；
图2是图1所示的测距***的像素阵列中单个像素的电路结构的一 实施例的示意图；
图3是图2所示的像素所涉及的信号时序的一实施例的示意图；
图4是图2所示的像素所涉及的信号时序的另一实施例的示意图；
图5是于调整第一比例和第二比例之前，多个第一像素于亮度0到11的分布直方图以及多个第二像素于亮度0到11的分布直方图；
图6是于调整第一比例和第二比例之后，多个第一像素于亮度0到11的分布直方图以及多个第二像素于亮度0到11的分布直方图；
图7是相位为0度、90度、180度和270度的脉冲的示意图。
具体实施方式
以下揭示内容提供了多种实施方式或例示，其能用以实现本申请内容的不同特征。下文所述之元件/组件与配置的具体例子是用以简化本申请内容。当可想见，这些叙述仅为示例，其本意并非用于限制本申请内容。举例来说，在下文的描述中，将一第一特征形成于一第二特征上或之上，可能包括某些实施例其中所述的第一与第二特征彼此直接接触；且也可能包括某些实施例其中还有额外的元件/组件形成于上述第一与第二特征之间，而使得第一与第二特征可能没有直接接触。此外，本申请内容可能会在多个实施例中重复使用元件符号和/或标号。此种重复使用乃是基于简洁与清楚的目的，且其本身不代表所讨论的不同实施例和/或组态之间的关系。
再者，在此处使用空间上相对的词汇，譬如「之下」、「下方」、「低于」、「之上」、「上方」及与其相似者，可能是为了方便说明图中所绘示的一组件或特征相对于另一或多个组件或特征之间的关系。这些空间上相对的词汇其本意除了图中所绘示的方位之外，还涵盖了装置在使用或操作中所处的多种不同方位。可能将所述设备放置于其他方位(如，旋转90度或处于其他方位)，而这些空间上相对的描述词汇就应该做相应的解释。
虽然用以界定本申请较广范围的数值范围与参数皆是约略的数值，此处已尽可能精确地呈现具体实施例中的相关数值。然而，任何数值本质上不可避免地含有因个别测试方法所致的标准偏差。在此处，「相同」通常系指实际数值在一特定数值或范围的正负10％、5％、1％或0.5％之内。或者是，「相同」一词代表实际数值落在平均值的可接受标准误差之内，视本申请所属技术领域中具有通常知识者的考虑而定。当可理解，除了实验例之外，或除非另有明确的说明，此处所用的所有范围、数量、数值与百分比(例如用以描述材料用量、时间长短、温度、操作条件、数量比例及其他相似者)均经过「相同」的修饰。因此，除非另有相反的说明，本说明书与附随申请专利范围所揭示的数值参数皆为约略的数值，且可视需求而更动。至少应将这些数值参数理解为所指出的有效位数与套用一般进位法所得到的数值。在此处，将数值范围表示成由一端点至另一端点或介于二端点之间；除非另有说明，此处所述的数值范围皆包括端点。
本申请能够在进行基于飞行时间的距离测量时，综合考虑深度信息和亮度信息，来分别调整针对不同距离所采取的信号采样的比例，以避免盲目地配置造成过曝或过暗的问题。
图1是本申请基于飞行时间的测距***的一实施例的功能方框示意图。测距***100可用于探测目标物102与测距***100之间的距离，需注意的是，目标物102与测距***100之间的距离应小于或等于测距***100的最大测量距离。举例来说(但本申请不限于此)，测距***100可以是三维成像***或者深度传感***，其可采用时间飞行法来测量周遭目标物的距离或深度，从而获得景深和三维图像信息。
值得注意的是，测距***100可实施为多种不同类型的飞行时间测距***，诸如基于飞行时间的光学测距***、基于飞行时间的声波测距***、基于飞行时间的雷达测距***，或其他类型的飞行时间测距***。为简洁起见，以下以测距***100实施为光学测距 ***的实施例来说明本申请的飞行时间测距方案。然而，本领域所属技术人员应可了解本申请的飞行时间测距方案可应用于任何基于飞行时间的测距***。
测距***100可包括(但不限于)一脉冲产生单元110、一控制电路120和一飞行时间传感器130。脉冲产生单元110用以间歇性地发送脉冲，其具有一脉冲长度T。在发送出一个脉冲之后，脉冲产生单元110会停止发送脉冲一段时间，而这段时间可远大于或大于脉冲长度T。一直到下一次启动时，脉冲产生单元110可再次发送一个脉冲。
于本申请中，测距***100可以是基于飞行时间的光学测距***，因此，脉冲产生单元110可由一光脉冲产生单元来实施，以产生一脉冲光信号EL。在本申请的第一种方案中，脉冲光信号EL可以是间歇产生的单个光脉冲。也就是说，所述光脉冲产生单元可间歇性地发送单个光脉冲，作为脉冲产生单元110间歇产生的单个脉冲。举例来说，脉冲产生单元110可包括(但不限于)一驱动电路和一发光单元(图1未示)。所述驱动电路用以驱动所述发光单元，使所述发光单元间歇性地发出单个光脉冲。所述发光单元可以是(但不限于)半导体激光器(又可称作激光二极管(Laser Diode，LD))、发光二极管(Light Emitting Diode，LED)或其他可以产生光脉冲的发光单元，其半导体激光器所产生的光脉冲是相干光(coherent light)，而发光二极管所产生的光脉冲是非相干光(incoherent light)。
值得注意的是，脉冲产生单元110可产生其他类型的脉冲，诸如声波脉冲或电磁波脉冲。例如，在测距***100实施为声波测距***的实施例中，脉冲产生单元110可由一声波脉冲产生器来实施。所述声波脉冲产生器用以间歇性地发送单个声波脉冲(诸如超声波脉冲)，作为脉冲产生单元110间歇产生的单个脉冲。又例如，在测距***100实施为雷达测距***的实施例中，脉冲产生单元110可由一电磁波脉冲产生器来实施。所述电磁波脉冲产生器用以间歇性 地发送单个电磁波脉冲，作为脉冲产生单元110间歇产生的单个脉冲。
控制电路120耦接于脉冲产生单元110，用以控制脉冲产生单元110产生脉冲光信号EL。例如，控制电路120可控制脉冲产生单元110间歇性地发送单个光脉冲。又例如，控制电路120可控制脉冲产生单元110所包括的驱动电路，使所述驱动电路驱动脉冲产生单元110所包括的发光单元间歇性地发送单个光脉冲。飞行时间传感器130由控制电路120所控制，用以对一反射信号RL进行采样，以检测测距***100(或飞行时间传感器130)与目标物102之间的距离，其中反射信号RL是脉冲光信号EL被目标物102反射而产生。在另外的实施例中，控制电路120可以是终端设备中的主控单元而不必包含在测距***100之中。
于本申请中，飞行时间传感器130在可调控的预定时间TR(为方便说明，以时间长度标记为TR的波形来表示)内持续地根据一采样时间间隔执行多次的信号采样，以产生反射信号RL的采样结果，换句话说，在预定时间TR的范围内抵达飞行时间传感器130的反射信号RL均可被感测到。一般来说，由于从近处和远处反射回来的反射信号RL会具有不同的到达时间，因此一般为了提升动态范围，会将预定时间TR设定为大于或等于脉冲长度T，例如大于或等于脉冲长度T的若干倍，使来自近处和远处的反射信号RL都能被捕获，但缺点是所收到的来自近处的信息量往往远多于来自远处的信息量，造成远处的信息量容易受到背景光的影响，引发散粒噪声(shot noise)。因此，本申请中的预定时间TR为可调控的，其细节说明于后。
在执行多次的所述信号采样以产生所述采样结果之后，飞行时间传感器130可根据所述采样结果计算出反射信号RL与脉冲产生单元110所发送的脉冲光信号EL之间的相位偏移。举例来说，飞行时间传感器130可包括(但不限于)一像素阵列132和一处理电路134。像素阵列132包括多个像素，各像素可包括一光传感器以根据反射 信号RL产生一光响应信号(photo response signal)。控制电路120可使各像素的光传感器选择性地将各像素相应的光响应信号输出到处理电路134。光传感器可以是光电二极管。
处理电路134可根据一采样控制信号SC，于预定时间TR中每隔所述采样时间间隔对各像素输出的光响应信号进行一次采样，并据以产生一采样结果SR，采样控制信号SC可由控制电路120产生。接下来，处理电路134可对采样结果SR进行信号处理，这些信号处理可以是诸如混频处理和离散傅里叶变换，以计算各像素所接收的反射信号RL的振幅(即亮度信息LI)，及各像素所接收的反射信号RL与脉冲产生单元110所发送的脉冲光信号EL之间的相位偏移，从而检测出脉冲光信号EL的飞行时间，以及根据飞行时间计算出目标物102与参考位置的距離(即深度信息DI)，并将亮度信息LI和深度信息DI传送至控制电路120，好让控制电路120据以控制脉冲产生单元110和像素阵列32，其细节说明于后。所述参考位置可以是(但不限于)测距***100的位置。
为了方便说明，以下采用一种像素电路的实施方式来说明本申请所公开的飞行时间测距方案。然而，本发明并不以此为限。图2是图1所示的像素阵列132中单个像素的电路结构的一实施例的示意图。请连同图1参阅图2。于此实施例中，像素332包括(但不限于)一光传感器PD、一第一读出电路(诸如光电读出电路)333和一第二读出电路(诸如光电读出电路)334。光传感器PD(诸如光电二极管)用以进行光传感操作。例如，光传感器PD可传感反射信号RL以对应地产生一光响应信号PR，其中光响应信号PR可通过第一读出电路333和第二读出电路334其中的至少一个读出电路输出。在一些实施例中，光传感器PD可将接收到的光信号转换成对应大小的光电流信号，即光响应信号PR可以是表征光信号大小的电流信号，第一读出电路333/第二读出电路334用于读出所述光电流信号。
第一读出电路333可根据一第一控制信号TX1选择性地传输光 传感器PD所产生的光响应信号PR，以产生一第一像素输出PO1，其中第一控制信号TX1可由控制电路120来提供。也就是说，像素332可根据第一控制信号TX1选择性地将光响应信号PR通过所述第一读出电路传送到处理电路130，以产生第一像素输出PO1并输出至处理电路130。第二读出电路334可根据一第二控制信号TX2选择性地传输光传感器PD所产生的光响应信号PR，以产生一第二像素输出PO2，其中第二控制信号TX2可由控制电路120来提供，并具有与第一控制信号TX1不同的相位，在一个具体例子中，TX1与TX2的相位差为180°。像素332可根据第二控制信号TX2选择性地将光响应信号PR通过所述第二读出电路传送到处理电路130，以产生第二像素输出PO2并输出至处理电路130。在此实施例中，第一控制信号TX1和第二控制信号TX2可由图1所示的控制电路120来提供。
于此实施例中，第一读出电路333可包括(但不限于)一第一复位晶体管MR1、一第一传输晶体管MT1、一第一输出晶体管MF1和一第一读取晶体管MW1。第二读出电路334包括(但不限于)一第二复位晶体管MR2、一第二传输晶体管MT2、一第二输出晶体管MF2和一第二读取晶体管MW2。第一复位晶体管MR1和第二复位晶体管MR2均根据一复位信号RST来分别复位一第一浮动扩散节点FD1和一第二浮动扩散节点FD2，其中复位信号RST可由控制电路120来提供。第一传输晶体管MT1和第二传输晶体管MT2均耦接于光传感器PD，分别根据第一控制信号TX1和第二控制信号TX2来导通，即第一传输晶体管MT1和第二传输晶体管MT2分别受控于第一控制信号TX1和第二控制信号TX2，以实现与光传感器PD的连接与断开。第一输出晶体管MF1和第一输出晶体管MF2分别用以放大第一浮动扩散节点FD1和第二浮动扩散节点FD2的电压信号，以分别产生一第一像素输出PO1和一第二像素输出PO2。第一读取晶体管MW1和第二读取晶体管MW2均根据一选择信号SEL，分别将第一像素输出PO1和第二像素输出PO2选择性地输出，其中选择信号SEL可由控制电路120来提供。
请一并参阅图1、图2和图3。图3是图2所示的像素332所涉及的信号时序的一实施例的示意图。图3中，脉冲产生单元110共发送两次脉冲PE，对应地，传感器130会进行两次的采样，两次采样的方式大致相同，但时间点不同，使前一次采样可针对反射信号RL中较快反射至传感器130的部分进行采样，后一次采样可针对反射信号RL中较慢反射至传感器130的部分进行采样。
进一步来说，以第一个脉冲PE来说，第一个脉冲PE于时间点t1发出后，经过反射成为反射信号RL，由于反射信号RL带有第一个脉冲PE从不同深度反射回来的能量，从近处反射回来的能量会较从远处反射回来的能量更快抵达像素332。也就是说，理论上从时间点t1之后任何时间都有可能带有第一个脉冲PE的反射信号RL的能量(请参考图3中反射信号RL在时间点t1之后的标示)。一般在高动态范围的应用中，可以增加每次采样的预定时间TR的长度，使采样到的信息量对应更广的深度范围，但采样到的信息中，反射自远处的信息会远远的少于反射自近处的信息，造成反射自远处的信息容易受到噪声干扰。
本实施例中，针对不同的脉冲PE进行不同的目标深度范围采样。例如针对图3中的第一个脉冲PE，控制电路120使传感器130对在预定时间TR1的时间范围内进行第一信号采样；对图3中的第二个脉冲PE，控制电路120使传感器130对在预定时间TR2的时间范围内进行第二信号采样。其中预定时间TR1相对于第一个脉冲PE的发出时间晚了第一时间差tX，预定时间TR2相对于第二个脉冲PE的发出时间晚了第一时间差tX+2TN，预定时间TR1和预定时间TR2的长度相同。因此，所述第一信号采样可以在预定时间TR1中采样到第一个脉冲PE从较近处反射回传感器130的能量；所述第二信号采样可以在预定时间TR2中采样到第二个脉冲PE从较远处反射回传感器130的能量，两者的目标采样深度不同且不重复。
在本实施例中，会发射多次的脉冲PE(例如上千次)，并依据预定时间TR1或预定时间TR2来进行所述第一信号采样或所述第二 信号采样。具体来说，可以使多次的脉冲PE中第一比例的脉冲PE对应所述第一信号采样，以及使多次的脉冲PE中第二比例的脉冲PE对应所述第二信号采样，例如依据所述第一比例和第二比例，使对应所述第一信号采样的脉冲PE的数目少于对应所述第二信号采样的脉冲PE的数目，以平衡来自近处和远处的能量，使来自近处的能量不会过度曝光，并拉高来自远处的能量。举例来说，80％的脉冲PE对应所述第二信号采样来针对远处信息进行采样；剩下20％的脉冲PE对应所述第一信号采样来针对进处信息进行采样。所述第一比例和所述第二比例可分别独立调整，其详细的调整方式将说明如后。
图3中第一时间差tX可设定为例如脉冲长度T的一半，但本申请不以此限。所述第一时间差和所述第二时间差的差也可以大于或小于两个采样区间TN，但应不小于采样区间TN。预定时间TR1可以包含两个采样区间TN(即时间点t2至时间点t4和时间点t4至时间点t6)；预定时间TR2可以包含两个采样区间TN(即时间点t10至时间点t12和时间点t12至时间点t14)，其中各采样区间TN的时间长度等于脉冲长度T。第一控制信号TX1于各采样区间TN的波形相同；第二控制信号TX2于各采样区间TN的波形相同。第二控制信号TX2和第一控制信号TX1之间可具有180度的相位差。
在某些实施例中，可以依据所需要的动态范围调整预定时间的长度，且不同类型的信号采样所针对的目标深度范围也可以彼此重叠。请参考图4，预定时间TR3可用于第三信号采样，预定时间TR3可以包含4个采样区间TN，例如预定时间TR3从时间点t2开始持续4个采样区间TN，因此预定时间TR3便可以同时包括预定时间TR1和预定时间TR2所针对的动态范围。换句话说，所述第三信号采样的目标深度范围为所述第一信号采样和所述第二信号采样的集合。因此，可以任意地依动态范围的需求来使多次的脉冲PE去对应不同类型的信号采样，且信号采样的类型数目没有限制，例如在某些实施例中可以依据所述第一比例和所述第二比例来使15％的脉冲PE对应所述第三信号采样，85％的脉冲PE对应所述第二信号采样，由于所述第三信号采样的目标深度范围完全包含了所述第一信号采样和 所述第二信号采样，因此实质上等同于使15％的脉冲PE对应所述第一信号采样，100％的脉冲PE对应所述第二信号采样；或使10％的脉冲PE对应所述第一信号采样，10％的脉冲PE对应所述第三信号采样，80％的脉冲PE对应所述第二信号采样，实质上等同于使20％的脉冲PE对应所述第一信号采样，90％的脉冲PE对应所述第二信号采样。
另外，于各采样区间TN中每隔所述采样时间间隔对各像素的输出进行一次采样，其中所述采样时间间隔可以是脉冲长度T的四分之一。然而，本申请并不以此为限，所述采样时间间隔也可以是脉冲长度T的八分之一或十六分之一。
如前所述，图3中的所述第一信号采样可以在预定时间TR1中采样到第一个脉冲PE从较近处反射回传感器130的能量；所述第二信号采样可以在预定时间TR2中采样到第二个脉冲PE从较远处反射回传感器130的能量，两者的目标采样深度不同且不重复。换句话说，所述第一信号采样对应了第一深度范围，例如距离测距***100为5到10公尺的深度范围；所述第二信号采样对应了第二深度范围，例如距离测距***100为10到20公尺的深度范围。
在测距***100尚未得知所欲进行测距的场景的任何信息时，会先使用预设的第一比例和第二比例来进行所述第一信号采样和所述第二信号采样。举例来说，预设的第一比例和第二比例可以完全依据深度范围来设定，例如所述第一信号采样是针对近距离的采样，所述第二信号采样是针对远距离的采样，则预设的第一比例和第二比例会给予所述第二信号采样较多的比重。但精确地来看，这样的配置不一定是正确的，例如在所欲进行测距的场景中，远距离的物体具有非常高的亮度，而近距离的物体反而具有非常低的亮度。
因此，在使用预设的第一比例和第二比例来进行所述第一信号采样和所述第二信号采样后，处理电路134从像素阵列132得到各像素的采样结果并计算出各像素的深度信息DI和亮度信息LI，并传送至控制电路120，控制电路120便可依据深度信息DI和亮度信息LI调整第一比例和第二比例。具体来说，控制电路120会依据各 像素的深度信息DI，来将各像素分类为第一像素和第二像素，分别对应至所述第一深度范围或所述第二深度范围。也就是说，深度信息DI落于所述第一深度范围的像素会被归类为所述第一像素；深度信息DI落于所述第二深度范围的像素会被归类为所述第二像素。并且，控制电路将所述第一像素所带有的亮度信息LI归类为第一亮度信息，以及将所述第二像素所带有的亮度信息LI归类为第二亮度信息。
假设所有像素皆属于所述第一像素，则可将所述第一比例调至最高，也就是可完全忽视所述第二信号采样。反之,如果所有像素皆属于所述第二像素，则将第二比例调至最高。
假设所述第一像素和所述第二像素皆有多个，则控制电路120会依据各第一像素的亮度信息LI来判断是否要加重或减轻所述第一信号采样的比重；以及依据各第二像素的亮度信息LI来判断是否要加重或减轻所述第二信号采样的比重。在本实施例中，控制电路120针对各第一像素的亮度信息LI进行统计，举例来说，依据各第一像素的亮度信息LI，将各第一像素对应至预设的多个亮度区间的其中之一，如图5的上方图表所示，有12个连续且互不重叠的区间，代表亮度0到11，则依据各第一像素的亮度信息LI来统计各区间对应至多少个第一像素，并得到统计直方图。类似地，图5的下方图表代表各第二像素的亮度信息LI的统计直方图。
表1为多个第一像素于亮度0到11的分布数目；表2为多个第二像素于亮度0到11的分布数目。
Figure PCTCN2020094918-appb-000001
表一
Figure PCTCN2020094918-appb-000002
Figure PCTCN2020094918-appb-000003
表二
依据表一及图5里的上方图绘示的情况，各第一像素的亮度信息LI的统计直方图显示出，依据预设的第一比例和第二比例进行所述第一信号采样有过度曝光的倾向，也就是亮度偏高的像素比例过高；而依据表二及图5里的下方图绘示的情况，各第二像素的亮度信息LI的统计直方图显示出，依据预设的第一比例和第二比例进行所述第二信号采样有曝光不足(过暗)的倾向，也就是亮度偏低的像素比例过高。
控制电路120可设定若干预设的参考值来作为判定是否要调整所述第一比例和所述第二比例的依据。例如当多个第一亮度信息中超过第一临界值的比例高于第一预设值(例如总个数的10％)，则降低所述第一比例；当所述多个第二亮度信息中超过所述第一临界值的比例高于所述第一预设值，降低所述第二比例；当所述多个第一亮度信息中低于第二临界值的比例高于第二预设值，提高所述第一比例；以及当所述多个第二亮度信息中超过所述第二临界值的比例高于所述第二预设值，提高所述第二比例。
因此，假设所述第一临界值为亮度9，第二临界值为亮度2，第一预设值和第二预设值皆为总个数的10％，则依据表1，超过亮度9的第一像素的个数为230，占总个数470的约49％，因此控制电路120判断需降低所述第一比例；又则依据表2，低于亮度2的第一像素的个数为200，占总个数375的约53％，因此控制电路120判断需提高所述第二比例。
在某些实施例中，控制电路120亦可以使用其他的机制来对表1和表2的统计值加以计算以决定如何调整所述第一比例和所述第二比例，例如也可以直接计算所有像素的平均亮度，若高于第三临 界值则降低对应的信号采样的比例，若低于第四临界值则提高对应的信号采样的比例。
因此，假设所述第三临界值为亮度8，第二临界值为亮度1，则依据表3，470个像素亮度的平均值为9，因此控制电路120判断需降低所述第一比例；依据表2，470个像素亮度的平均值为1.6，因此控制电路120判断需提高所述第二比例。
经过上述方式，控制电路120可更新所述第一比例和所述第二比例，使后续的测距操作得到的结果更为平衡，如图6里的上方图所示，各第一像素的亮度信息LI的统计直方图显示出，依据经过控制电路120调整后的第一比例和第二比例进行所述第一信号采样已经没有过度曝光或曝光不足的情况，也就是亮度适中的像素比例最高；如图6里的下方图所示，各第二像素的亮度信息LI的统计直方图显示出，依据经过控制电路120调整后的第一比例和第二比例进行所述第二信号采样也已经没有过度曝光或曝光不足的情况，也就是亮度适中的像素比例最高。
在某些实施例中，控制电路120可实时地依据处理电路134传送来的深度信息DI和亮度信息LI来更新所述第一比例和所述第二比例。在某些实施例中，控制电路120亦可只更新一次所述第一比例和所述第二比例并持续使用直到测距操作结束。此外，针对有超过两种类型的信号采样的情况，亦可使用上述的方式来设定多个类型的信号采样的比例。
在某些实施例中，如图7所示，脉冲产生单元110会间歇性地发送多个相位为0度的脉冲PE，之后再间歇性地发送多个相位为90度的脉冲PE，之后再间歇性地发送多个相位为180度的脉冲PE，之后再间歇性地发送多个相位为270度的脉冲PE。由于四种相位的脉冲PE彼此间具有相位差，也就是反射信号RL到达像素阵列132的时间先天就有先后的差异，因此若使用针对0度的脉冲PE设计的信号采样配置方式(如针对0度的脉冲PE所得到的最佳化的第一比例和第二比例)使用在相位为90、180或270度的脉冲PE，效果会打 折扣。因此，本申请的一实施例中，会针对不同相位的脉冲PE分别计算信号采样配置方式，如针对90、180和270度的脉冲PE分别依据前述的方法找出第一比例和第二比例。
上文的叙述简要地提出了本申请某些实施例的特征，使本领域的技术人员可更全面地理解本申请的多个层面。本领域的技术人员应可了解，其可轻易地利用本申请作为基础，来设计或更动其他流程与结构，以实现与上文所述的实施方式相同的目的和/或达到相同的优点。本领域的技术人员应当明白，这些等效的实施方式仍属于本申请的精神与范围，且其可进行各种改变、替代与更改，而不会悖离本申请的精神与范围。

Claims (26)

  1. 一种基于飞行时间的测距方法，其特征在于，包括：
    从脉冲产生单元间歇性地发送多个脉冲，其中所述多个脉冲被目标物反射而产生多个反射信号；
    使飞行时间传感器让所述飞行时间传感器中的多个像素中各像素对第一比例的所述多个反射信号持续第一预定时间来执行第一信号采样，以及对第二比例的所述多个反射信号持续第二预定时间来执行第二信号采样，以产生对应所述多个像素的多个采样结果，其中所述第一预定时间的开始时间点和对应的所述脉冲的发送时间点具有第一时间差，以及所述第二预定时间的开始时间点和对应的所述脉冲的发送时间点具有第二时间差，且所述第一时间差小于所述第二时间差，以及所述第一信号采样对应第一深度范围，所述第二信号采样对应第二深度范围；
    根据所述多个采样结果，得到对应所述多个像素的多个深度信息和多个亮度信息；以及
    依据所述多个深度信息和所述多个亮度信息调整所述第一比例和所述第二比例。
  2. 如权利要求1所述的测距方法，其中依据所述多个深度信息和所述多个亮度信息调整所述第一比例和所述第二比例的步骤包括：
    依据对应所述多个像素的所述多个深度信息、所述第一深度范围和所述第二深度范围，来将对应所述多个像素的所述多个亮度信息分类为多个第一亮度信息和多个第二亮度信息；以及
    依据所述多个第一亮度信息和所述多个第二亮度信息来调整所述第一比例和所述第二比例。
  3. 如权利要求2所述的测距方法，其中依据对应所述多个像素的所 述多个深度信息、所述第一深度范围和所述第二深度范围，来将对应所述多个像素的所述多个亮度信息分类为所述多个第一亮度信息和所述多个第二亮度信息的步骤包括：
    将所述多个像素中，具有落于所述第一深度范围的深度信息的多个像素对应的多个亮度信息归类为所述多个第一亮度信息；以及
    将所述多个像素中，具有落于所述第二深度范围的深度信息的多个像素对应的多个亮度信息归类为所述多个第二亮度信息。
  4. 如权利要求2或3所述的测距方法，其中依据所述多个第一亮度信息和所述多个第二亮度信息来调整所述第一比例和所述第二比例的步骤包括：
    当所述多个第一亮度信息中超过第一临界值的比例高于第一预设值，降低所述第一比例；以及
    当所述多个第二亮度信息中超过所述第一临界值的比例高于所述第一预设值，降低所述第二比例。
  5. 如权利要求2或3所述的测距方法，其中依据所述多个第一亮度信息和所述多个第二亮度信息来调整所述第一比例和所述第二比例的步骤另包括：
    当所述多个第一亮度信息中低于第二临界值的比例高于第二预设值，提高所述第一比例；以及
    当所述多个第二亮度信息中超过所述第二临界值的比例高于所述第二预设值，提高所述第二比例。
  6. 如权利要求1-5中任一项所述的测距方法，其中所述第一预定时间包括相邻所述第一预定时间的开始时间点的至少一采样区间；所述第二预定时间包括相邻所述第二预定时间的开始时间点的至少一所述采样区间，所述采样区间具有固定的时间长度。
  7. 如权利要求6所述的测距方法，其中所述采样区间的时间长度等于所述多个脉冲中各脉冲的脉冲长度。
  8. 如权利要求7所述的测距方法，其中所述第二时间差和所述第一时间差的差至少为所述采样区间的时间长度。
  9. 如权利要求7所述的测距方法，其中所述第一预定时间和所述第二预定时间包括相同数目的所述采样区间。
  10. 如权利要求7所述的测距方法，其中所述第一预定时间包括的所述采样区间的数目大于所述第二预定时间包括的所述采样区间的数目。
  11. 如权利要求1-10中任一项所述的测距方法，其中所述第一深度范围和所述第二深度范围不重叠。
  12. 如权利要求1-10中任一项所述的测距方法，其中所述第一深度范围和所述第二深度范围部分重叠。
  13. 如权利要求1-10中任一项所述的测距方法，另包括：
    从所述脉冲产生单元间歇性地发送多个延迟脉冲，其中所述多个延迟脉冲被所述目标物反射而产生多个延迟反射信号，且所述多个延迟脉冲和所述多个脉冲的相位差是90、180或270度；以及
    使所述飞行时间传感器让所述飞行时间传感器中的所述多个像素中各像素对第三比例的所述多个延迟反射信号执行所述第一信号采样，以及对第四比例的所述多个延迟反射信号执行所述第二信号采样，以产生对应所述多个像素的多个延迟采样结果，其中所述第三比例和所述第一比例不同，以及所述第四比例和所述第二比例不同；
    根据所述多个延迟采样结果，得到对应所述多个像素的多个延迟深度信息和多个延迟亮度信息；以及
    依据所述多个延迟深度信息和所述多个延迟亮度信息调整所述 第三比例和所述第四比例。
  14. 一种基于飞行时间的测距***，其特征在于，包括：
    脉冲产生单元；
    控制电路，耦接于所述脉冲产生单元，用以控制所述脉冲产生单元间歇性地发送多个脉冲，以及依据多个深度信息和多个亮度信息调整第一比例和第二比例，其中所述多个脉冲被目标物反射而产生多个反射信号；以及
    飞行时间传感器，包括具有多个像素的像素阵列，所述飞行时间传感器由所述控制电路所控制，用以让所述多个像素中各像素对所述第一比例的所述多个反射信号持续第一预定时间来执行第一信号采样，以及对所述第二比例的所述多个反射信号持续第二预定时间来执行第二信号采样，以产生对应所述多个像素的多个采样结果，其中所述第一预定时间的开始时间点和对应的所述脉冲的发送时间点具有第一时间差，以及所述第二预定时间的开始时间点和对应的所述脉冲的发送时间点具有第二时间差，且所述第一时间差小于所述第二时间差，以及所述第一信号采样对应第一深度范围，所述第二信号采样对应第二深度范围，所述飞行时间传感器并根据所述多个采样结果，得到对应所述多个像素的所述多个深度信息和所述多个亮度信息。
  15. 如权利要求14所述的测距***，其中所述控制电路另用以：
    依据对应所述多个像素的所述多个深度信息、所述第一深度范围和所述第二深度范围，来将对应所述多个像素的所述多个亮度信息分类为多个第一亮度信息和多个第二亮度信息；以及
    依据所述多个第一亮度信息和所述多个第二亮度信息来调整所述第一比例和所述第二比例。
  16. 如权利要求15所述的测距***，其中所述控制电路另用以：
    将所述多个像素中，具有落于所述第一深度范围的深度信息的多个像素对应的多个亮度信息归类为所述多个第一亮度信息；以及
    将所述多个像素中，具有落于所述第二深度范围的深度信息的多个像素对应的多个亮度信息归类为所述多个第二亮度信息。
  17. 如权利要求15所述的测距***，其中所述控制电路另用以：
    当所述多个第一亮度信息中超过第一临界值的比例高于第一预设值，降低所述第一比例；以及
    当所述多个第二亮度信息中超过所述第一临界值的比例高于所述第一预设值，降低所述第一比例。
  18. 如权利要求15所述的测距***，其中所述控制电路另用以：
    当所述多个第一亮度信息中低于第二临界值的比例高于第二预设值，提高所述第一比例；以及
    当所述多个第二亮度信息中超过所述第二临界值的比例高于所述第二预设值，提高所述第二比例。
  19. 如权利要求14所述的测距***，其中所述第一预定时间包括相邻所述第一预定时间的开始时间点的至少一采样区间；所述第二预定时间包括相邻所述第二预定时间的开始时间点的至少一所述采样区间，所述采样区间具有固定的时间长度。
  20. 如权利要求19所述的测距***，其中所述采样区间的时间长度等于所述多个脉冲中各脉冲的脉冲长度。
  21. 如权利要求20所述的测距***，其中所述第二时间差和所述第一时间差的差至少为所述采样区间的时间长度。
  22. 如权利要求20所述的测距***，其中所述第一预定时间和所述第二预定时间包括相同数目的所述采样区间。
  23. 如权利要求20所述的测距***，其中所述第一预定时间包括的所述采样区间的数目大于所述第二预定时间包括的所述采样区间的数目。
  24. 如权利要求14所述的测距***，其中所述第一深度范围和所述第二深度范围不重叠。
  25. 如权利要求14所述的测距***，其中所述第一深度范围和所述第二深度范围部分重叠。
  26. 如权利要求14所述的测距***，其中所述控制电路进一步控制所述脉冲产生单元间歇性地发送多个延迟脉冲，以及依据多个延迟深度信息和多个延迟亮度信息调整第三比例和第四比例，其中所述多个延迟脉冲被所述目标物反射而产生多个延迟反射信号，且所述多个延迟脉冲和所述多个脉冲的相位差是90、180或270度；以及所述飞行时间传感器进一步让所述飞行时间传感器中的所述多个像素中各像素对所述第三比例的所述多个延迟反射信号执行所述第一信号采样，以及对所述第四比例的所述多个延迟反射信号执行所述第二信号采样，以产生对应所述多个像素的多个延迟采样结果，其中所述第三比例和所述第一比例不同，以及所述第四比例和所述第二比例不同，所述飞行时间传感器并根据所述多个延迟采样结果，得到对应所述多个像素的所述多个延迟深度信息和所述多个延迟亮度信息。
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