CN110456370B - Flight time sensing system and distance measuring method thereof - Google Patents
Flight time sensing system and distance measuring method thereof Download PDFInfo
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- CN110456370B CN110456370B CN201910695653.9A CN201910695653A CN110456370B CN 110456370 B CN110456370 B CN 110456370B CN 201910695653 A CN201910695653 A CN 201910695653A CN 110456370 B CN110456370 B CN 110456370B
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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
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F17/00—Digital computing or data processing equipment or methods, specially adapted for specific functions
- G06F17/10—Complex mathematical operations
- G06F17/17—Function evaluation by approximation methods, e.g. inter- or extrapolation, smoothing, least mean square method
Abstract
A flight time sensing system and a distance measuring method thereof are provided, wherein the flight time distance measuring method comprises the following steps: delaying the detection light pulse frame by frame in the order of the plurality of detection frames; receiving reflected light of the detection light pulse after being reflected by the object to be detected, and acquiring an initial depth value of each detection frame; acquiring a depth value curve of the initial depth value changing along with the delay time of the detection light pulse according to the initial depth value of each detection frame and the delay time of the corresponding detection light pulse; and obtaining the actually measured depth values of the single output frame corresponding to the plurality of detection frames according to the depth value curve. The flight time sensing system can improve the accuracy of distance detection.
Description
Technical Field
The invention relates to the technical field of sensing, in particular to a flight time sensing system and a distance measuring method thereof.
Background
The Time Of Flight (TOF) method measures the three-dimensional structure or three-dimensional profile Of an object to be measured by using a Time interval between transmission and reception Of a pulse signal from a measuring instrument or a phase difference generated when a laser beam travels back and forth to the object to be measured once. The TOF measuring instrument can simultaneously obtain a gray image and a distance image, and is widely applied to the fields of somatosensory control, behavior analysis, monitoring, automatic driving, artificial intelligence, machine vision, automatic 3D modeling and the like.
Time-of-flight (TOF) sensors generally include: the device comprises a light source module and a photosensitive module; the light source module is used for emitting pulse detection light with a specific waveband and a specific frequency, the detection light is reflected on the surface of a detected object, and the reflected light is received by the photosensitive module; and the photosensitive module calculates the distance information of the object to be measured according to the time difference or the phase difference between the transmitting light wave and the receiving light wave.
However, in the prior art, particularly when the detection environment is relatively complicated, a detection result of the TOF sensor has a large error.
Disclosure of Invention
The invention aims to solve the technical problem of providing a flight time sensing system and a distance measuring method thereof, which can eliminate the problem of multipath interference of light and improve the accuracy of distance detection.
In order to solve the above problem, the present invention provides a distance measuring method for a time-of-flight sensing system, comprising: delaying the detection light pulse frame by frame in the order of the plurality of detection frames; receiving reflected light of the detection light pulse after being reflected by the object to be detected, and acquiring an initial depth value of each detection frame; acquiring a depth value curve of the initial depth value changing along with the delay time of the detection light pulse according to the initial depth value of each detection frame and the delay time of the corresponding detection light pulse; and obtaining the actually measured depth values of the single output frame corresponding to the plurality of detection frames according to the depth value curve.
Optionally, the detection light pulses are delayed frame by frame at the same time intervals.
Optionally, the time-of-flight sensing system includes a pixel array composed of a plurality of pixel units; respectively acquiring initial depth values of all detection frames aiming at all pixel units; and respectively acquiring the depth value curves corresponding to the pixel units.
Optionally, an initial depth value corresponding to a starting point where the depth value on the depth value curve linearly decreases with the maximum slope along with the delay time is used as the actually measured depth value.
Optionally, when the depth value curve has more than one turning point, according to the requirement of the distance measurement precision, an initial depth value corresponding to a suitable turning point is selected as the actually measured depth value, or an initial depth value corresponding to any point between a point where a first depth value decreases with the delay time on the depth value curve and a starting point where the depth value decreases linearly with the maximum slope with the delay time is used as the actually measured depth value.
Optionally, the initial depth value and the delay time of the corresponding detection light pulse are fitted to obtain the depth value curve, and the fitting method includes 2D difference, polynomial fitting, or piecewise function fitting.
Optionally, in a plurality of detection frames corresponding to a single output frame, the maximum delay time of the detection light pulse is greater than the pulse width of the detection light pulse.
Optionally, a depth value correction rule is obtained according to the actually measured depth value of the output frame and the initial depth values of the corresponding detection frames; and correcting the initial depth value of each subsequent detection frame according to the depth value correction rule to obtain the actual measurement depth value of each detection frame, wherein each detection frame corresponds to an output frame.
The technical scheme of the invention also provides a flight time sensing system, which comprises: the light source module is used for emitting detection light pulses; the sensing module is used for receiving reflected light of the detection light pulse after being reflected by an object to be detected and acquiring the characteristics of the reflected light; the control module is connected with the light source module and used for controlling the light source module to delay the detection light pulse frame by frame according to the sequence of a plurality of detection frames; the processing module is connected with the sensing module and used for carrying out the following processing: acquiring initial depth values of all detection frames according to the detection light and the reflected light; acquiring a depth value curve of the initial depth value changing along with the delay time of the detection light pulse according to the initial depth value of each detection frame and the delay time of the corresponding detection light pulse; and obtaining the actually measured depth values of the single output frame corresponding to the plurality of detection frames according to the depth value curve.
Optionally, the control module is configured to control the light source module to delay the detection light pulse frame by frame at the same time interval.
Optionally, the time-of-flight sensing system includes a pixel array composed of a plurality of pixel units; the processing module is used for respectively obtaining the initial depth value of each detection frame aiming at each pixel unit and respectively obtaining the depth value curve corresponding to each pixel unit.
Optionally, the processing module is configured to use an initial depth value corresponding to a starting point where the depth value on the depth value curve linearly decreases with a maximum slope along with the delay time as the actually measured depth value.
Optionally, when there is more than one turning point on the depth value curve, the processing module is configured to select an initial depth value corresponding to a suitable turning point as the actually measured depth value according to the requirement of the distance measurement precision, or select, as the actually measured depth value, an initial depth value corresponding to any point between a point where a first depth value decreases with a delay time on the depth value curve and a starting point where the depth value decreases with a maximum slope linearity with the delay time.
Optionally, the processing module is configured to fit the initial depth value to the corresponding delay time of the detected light pulse to obtain the depth value curve, where the fitting method includes 2D difference, polynomial fitting, or piecewise function fitting.
Optionally, in a plurality of detection frames corresponding to a single output frame, the maximum delay time of the detection light pulse is greater than the pulse width of the detection light pulse.
Optionally, the processing module is further configured to obtain a depth value correction rule according to the actually measured depth value of the output frame and the corresponding initial depth values of the plurality of detection frames; and correcting the initial depth value of each subsequent detection frame according to the depth value correction rule to obtain the actual measurement depth value of each detection frame, wherein each detection frame corresponds to an output frame.
The distance measuring method eliminates the influence of multiple reflected lights on the detection result by delaying the detection light pulse, thereby correcting the detection result and improving the accuracy of distance detection.
Drawings
FIG. 1 is a schematic diagram of a reflection path existing during a ranging process according to an embodiment of the present invention;
FIG. 2a is a schematic illustration of the detection of optical pulse delay in the presence of only one reflected light according to an embodiment of the present invention;
FIG. 2b is a schematic illustration of the detection of optical pulse delays in the presence of one and more reflected lights according to an embodiment of the present invention;
FIG. 3 is a flow chart illustrating a ranging process according to an embodiment of the present invention;
FIG. 4 is a diagram illustrating a correspondence relationship between an output frame and a detection frame according to an embodiment of the present invention;
FIG. 5 is a graph illustrating the variation of the detection distance with the number of detection light pulse downshifts according to an embodiment of the present invention;
FIG. 6 is a diagram illustrating a correspondence relationship between a plurality of output frames and a detection frame according to an embodiment of the present invention;
FIG. 7 is a diagram illustrating a ranging result correction according to an embodiment of the present invention;
FIG. 8 is a schematic structural diagram of a time-of-flight sensing system according to an embodiment of the present invention.
Detailed Description
As described in the background section, the time-of-flight sensor of the prior art has a large detection error in a complicated detection environment.
The inventor researches and discovers that part of detection errors are caused by multiple reflected lights, the multiple reflected lights are transmitted through multiple reflection paths, the optical path is large, and the multiple reflected lights are received in a delayed mode, so that the detection results are inaccurate. The specific description is as follows:
referring to fig. 1(a), in this case, only one reflected light exists, the detection light emitted by the light source module directly reaches the surface of the object to be detected, and when the reflected light reflected by the object to be detected is directly received by the light sensing module, the distance corresponds to the time difference or the phase difference between the emission light wave and the reception light wave.
In the actual measurement process, under the condition that the measurement environment is relatively complex, the problem of multipath interference of light exists. Part of the detection light directly reaches the surface of the object to be detected, and the reflected light is also directly received by the photosensitive module; part of the detecting light may be reflected by the interfering object multiple times and then reach the surface of the object to be detected, and the reflected light reflected by the surface of the object to be detected may also be reflected by the interfering object multiple times and then received by the photosensitive module again (see fig. 1 (b)). In this case, the optical path length of part of the detected light and/or reflected light is greater than twice the distance between the actual light source and the object to be measured, and the time difference or phase difference between the emitted light wave and the received light wave does not correspond to the distance, which results in a decrease in the accuracy of the finally detected distance information.
Further, referring to fig. 2a and fig. 2b, in this embodiment, the pulse of the detecting light is a rectangular pulse. In the process of receiving the reflected light, the reflected light signal (actually including the reflected light of the detected light and the ambient light) is received by the shutters G2 and G3, and the ambient light signal is received by the shutter G1. Specifically, the shutters G1, G2, and G3 may be implemented by a capacitive structure, and after the ambient light and the reflected light are received by the pixel units of the sensor array, the light signals are converted into electrical signals, and charges of the electrical signals are accumulated by the shutters G1, G2, and G3, so that the amount of the obtained charges is proportional to the light energy. The integration time of the shutters G1, G2, and G3 is T, and is consistent with the pulse width of the detection light pulse, the depth value may be a distance, or an intermediate parameter corresponding to the distance, for example, a ratio of the charge amounts received by the shutters G2 and G3, and the charge amount may be represented by an electrical parameter such as voltage. The edges of the integration pulses of G1, G2 and G3 are aligned in sequence, the falling edge of G1 is aligned with the rising edge of G2, and the falling edge of G2 is aligned with the rising edge of G3.
In the case of no multiple reflection (please refer to fig. 2a), G1, G2, and G3 represent the accumulated charge amount of each shutter, respectively, when the detecting light pulse LO1 is aligned with the shutter G2 pulse, i.e. the delay time is 0, the shutters G2 and G3 each accumulate part of the reflected light energy, and the distance corresponding to the depth value measured by exposure is as follows:
since the ambient light energy collected by the shutters G1, G2, and G3 are all the same, the equation can be simplified to:
wherein G2 'and G3' represent reflected light energy of the detection light received by the shutters G2 and G3 after being reflected by the object to be measured. Detecting the obtained depth information and
or
Is in direct proportion.
The detection light pulse is difficult to be a standard rectangular pulse because of errors in the light intensity of the detection light and in time control. Therefore, in other embodiments, the detection light pulse may be a triangular wave pulse or a non-standard rectangular wave pulse. At this time, the detected distance is still equal to
And (4) positively correlating.
When the detection light pulse is not moving,
detecting the distance d and
positive correlation;
when the pulse is shifted back by Ts,
wherein d is0And
the relationship of (c) is unchanged.
For the case where there are no multiple reflections, d is the only reflection light that is not moved out of the reception range of the shutter G30Is increased by an amount just equal to
Therefore, d does not change either; and the reflected light is completely moved out of the reception range of the shutter G2,
d0no longer increases and thus d decreases linearly with the delay time Ts.
For the case of multipath reflection, referring to fig. 2b, since the optical path of the multiple reflected light is larger than the optical path of the single reflected light, the time to reach the sensor array of the sensor is delayed. The reflected light LB11 corresponding to the detection light pulse LO11 includes first reflected light and multiple reflected light, and the energy of the multiple reflected light is small; the offset Td between the primary reflected light pulse and the detection light pulse is proportional to the actual distance, and the multiple reflected light lags behind the primary reflected light by Tp, which results in the shutter G3 receiving the multiple reflected light for an extra time Tp to obtain more reflected light energy, and according to the formula (2), the larger G3' results in the measured distance being larger than the actual distance.
From the above-described studies, the inventors have further found that by shifting the pulse width of the detection light backward, the reflected light can be shifted backward, and the delay portion of the secondary and multiple reflected lights is gradually out of the range of reception of the integrated pulse of the shutter G3 due to more delay, and cannot be received by the shutter G3, thereby reducing the influence of the delay portion of the secondary and multiple reflected lights on the distance detection. Referring to fig. 2b, when the delay time Ts of the detection light pulse LO12 is Td + Tp, the part of the twice reflected light delayed in the time period of the once reflected light Tp cannot be received by the shutter G3 any more, and the shutter G3 can only receive the reflected light within T time, at this time, the shutter G2 cannot collect the reflected light energy, so that the measured initial depth value linearly decreases with the increase of the delay time, that is, the initial depth value corresponding to the start point of the linearly decreasing initial depth value d with the delay time is used as the actual distance of the target reflection object regardless of the existence of multiple reflected lights, so as to eliminate the influence of the multiple reflected lights.
However, in the actual distance measurement process, we cannot know the specific delay time of the multiple reflected light, and therefore cannot accurately set the optimum delay time for detecting the light pulse.
Therefore, the inventor proposes a new time-of-flight sensing system and a ranging method thereof, which use a method of delaying the detection light pulse frame by frame to correct the detection result by gradually moving the detection light pulse backwards for a plurality of times.
The following describes in detail a specific embodiment of a time-of-flight sensing system and a ranging method thereof according to the present invention with reference to the accompanying drawings.
Fig. 3 is a schematic flow chart of a distance measuring method of a time-of-flight sensing system according to an embodiment of the present invention.
The distance measuring method of the flight time sensing system at least comprises the following steps:
step S101: the detection light pulse is delayed frame by frame in the order of the plurality of detection frames.
In this embodiment, the detection data of each output frame is obtained by processing the detection data of a plurality of detection frames, one output frame corresponds to outputting one detection result, and one detection frame corresponds to performing one detection exposure. Referring to FIG. 4, for the first output frame F1Corresponding to n detection frames f11～f1nSubsequently, the detection results of the n detection frames are processed to obtain a first output frame F1And (5) corresponding detection results.
In this embodiment, the frame f is detected as the first frame f11With reference to the generation timing of the detection light pulse, and the subsequent detection frame f12～f 1nThe detected light pulse of (a) is delayed frame by frame to gradually delay the multiple reflected light and the portion of the one reflected light out of the range of the integration time of the shutter G3.
In a specific embodiment, the detection light pulses are delayed frame by frame at the same time interval t. Setting the delay time of a first detection light pulse of a first detection frame as 0, delaying a second detection light pulse of a second detection frame relative to the first detection light pulse by t, and setting the total delay time as t; the delay time of the third detection light pulse of the third detection frame with respect to the second detection light pulse is also t, the total delay time is 2t, and so on, the detection light pulse of the nth detection frame is delayed with respect to the detection light pulse of the (n-1) th detection frame by t, and the total delay time is (n-1) t.
In other embodiments, the delay time interval may be reduced frame by frame, and the delay time interval is larger between the first several detection frames to improve the efficiency, for example, the second detection pulse light is delayed by 3t with respect to the first detection pulse light, the third detection pulse light is delayed by 2t with respect to the second detection pulse light, and so on.
The frame-by-frame delay of the detection light pulse can be realized by controlling the light emitting time sequence of the light source module of the time-of-flight sensing system.
Step S102: and receiving reflected light of the detection light pulse after being reflected by the object to be detected, and acquiring the initial depth value of each detection frame.
The depth value may be a distance, or may be another parameter corresponding to the distance. The depth value is subsequently described as being equivalent to the distance.
The initial depth values may be calculated according to equation (1), and in the case where reflected light, whether once reflected light or multiple reflected light, is received by the shutters G2 and G3, although the reflected light energy received by the shutter G3 gradually increases and the reflected light energy received by the shutter G2 gradually decreases as the detection pulse light moves backward, the calculated initial depth values are theoretically the same.
When the multiple reflected lights delayed from the one reflected light start to be gradually shifted out of the integration time region of the shutter G3, the reflected light energy received by the G3 is reduced, thereby causing the initial depth value calculated according to the formula (1) to be gradually reduced.
When the multiple reflected light delayed from the primary reflected light is completely shifted out of the integration time region of the shutter G3 (as the reflected light LB12 in fig. 2 b), the shutter G2 cannot receive the energy of the reflected light, and the light pulse is continuously delayed for detection, which results in that the primary reflected light is gradually shifted out of the integration time region of the shutter G3, and thus the light energy collected by the shutter G3 is decreased by an increased amount, and thus the initial depth value is decreased by an increased amount.
Step S103: and acquiring a depth value curve of the initial depth value changing along with the delay time of the detection light pulse according to the initial depth value of each detection frame and the corresponding delay time of the detection light pulse.
And fitting the initial depth value and the delay time of the corresponding detection light pulse to obtain the depth value curve, wherein the fitting method comprises 2D difference value, polynomial fitting or piecewise function fitting and the like.
Since the integrated energy of G3 decreases only when the detection light pulse is shifted backward causing the reflected light pulse to move out of the integration time of the shutter G3 in the case where only one reflected light exists, resulting in a linear decrease of the resulting initial depth value with delay time, the depth value curve will have an inflection point for only one reflected light.
In the case of multiple reflected lights, for example, three reflected lights, the two reflected lights and the one reflected light are gradually shifted out of the integration time of G3, because the light intensities of the one reflected light, the two reflected lights and the three reflected lights are different, the initial depth value has three turning points, and the decreasing rate after each turning point is increased.
In order to obtain a starting point at which the initial depth value linearly decreases with the maximum slope with the delay time, the maximum delay time of the detection light pulse is greater than the pulse width T of the detection light pulse within a plurality of detection frames corresponding to a single output frame.
In one embodiment, the detection range is L0 ═ 5m, that is, the detection light pulse width T is 33 ns; the detection light pulse initially coincides with the shutter G2 at the target theoretical distance L of 1m, and is shifted backward by 3.3ns from frame to frame, and when the detection light pulse is shifted backward 10 times, the detection light pulse coincides with the shutter G3.
Referring to fig. 5, a graph illustrating the change of the detected distance and the subsequent shift times (i.e., delay time) in this embodiment is shown.
In an actual ranging process, the initial depth information of a plurality of detection frames is fitted to the delay time to form a curve, which may include a plurality of linear segments, or may be a plurality of arc segments or continuous arcs, and the initial depth value decreases linearly with the delay time only when the reflected light is shifted out of the receiving time of the shutter G2 as the detection light pulse is delayed. The turning point may be a connection point of a plurality of arc segments, may be exactly a data point corresponding to a certain detection frame, or may be a data point fitted between two detection frames.
The time-of-flight sensing system comprises a pixel array composed of a plurality of pixel units; since the distances of the measured object in the detection field corresponding to each pixel unit are different and the situations of multiple reflected lights included in the obtained reflected lights are also different, it is necessary to obtain the initial depth value of each detection frame and the depth value curve corresponding to each pixel unit for each pixel unit, so as to correct the detection result obtained by each pixel unit.
Step S104: and obtaining the actually measured depth values of the single output frame corresponding to the plurality of detection frames according to the depth value curve.
An initial depth value corresponding to a turning point position on the depth value curve may be selected as a measured depth value of a single output frame corresponding to a plurality of detection frames.
In the actual detection process, the delay times and the delay time of the detection pulse light of each detection frame are reasonably set according to the distance measurement efficiency, the power consumption of the sensing system, the computing capacity and the like. Under the condition that the number of the detection frames is enough and the delay time is long enough, turning points corresponding to the reflected light of each path can appear on the depth value curve, and the initial depth value corresponding to the turning point with the maximum slope change at the two sides of the depth value curve can be selected as the actually-measured depth value.
However, considering the power consumption and detection efficiency of the system, there is a limit to the accuracy control of the delay times and delay times, so that when there is more than one turning point on the depth value curve, the initial depth value corresponding to the appropriate turning point may be selected as the measured depth value according to the requirement of the distance measurement accuracy. Alternatively, an initial depth value corresponding to any point between a point on the depth value curve where the first depth value decreases with the delay time and a starting point where the depth value decreases linearly with the maximum slope with the delay time may be used as the measured depth value.
In other specific embodiments, an initial depth value corresponding to a starting point on the depth value curve where the depth value linearly decreases with the maximum slope along the delay time may be used as the measured depth value, where the obtained measured depth value is closest to the actual distance.
By shifting the detection light pulse backward so that the multiple reflections exceed the integral range of the reflected light, the accuracy of the distance measurement can be improved.
Referring to FIG. 4, for the first output frame F1Correspondingly outputting the measured depth value D1The first output frame F1Corresponding to n detection frames, obtaining initial depth values d for the n detection frames1～d1nProcessing to obtain the first output frame F1Output measured depth value D1。
Referring to FIG. 6, for the second output frame F2Correspondingly outputting the measured depth value D2Said second output frame F2Corresponding to n detection frames, obtaining initial depth values d for the n detection frames1n～d2nProcessing to obtain the second output frame F2Output measured depth value D2(ii) a Analogize in turn, for the m-th output frame FmCorrespondingly outputting the measured depth value DmSaid m-th output frame FmCorresponding to n detection frames, obtaining the n detection framesOf the initial depth value dm1～dmnProcessing to obtain the m-th output frame FmOutput measured depth value Dm。
In some embodiments, the initial depth values obtained from the multiple detection frames of the first output frame may be processed, and in the process of obtaining the actually measured depth value, the proper number of delays, delay time, and the like may be obtained as the subsequent detection parameters. In other specific embodiments, a delay time Ts corresponding to an actually measured depth value of a first output frame may also be obtained, in a detection process of a subsequent frame, the detection pulse light pulse delay Ts may be directly detected, and a detection result of a single detection frame may be used as an actually measured depth value of a corresponding output frame, so that detection efficiency may be improved, and system power consumption may be reduced.
Fig. 7 is a schematic diagram of a distance measuring method according to another embodiment of the present invention.
After obtaining the measured depth values of the first output frame, a mapping function between the initial depth values and the measured depth values of each detection frame may be obtained. Let d be1tThe first turning point value of the depth value curve of the first output frame, that is, the initial depth value corresponding to the starting point of the depth value descending along with the delay time. The break point value d can be obtained1tInitial depth value d of each previous detection frame11～d1tThe mapping function of (2). Theoretically, the turning point value d1tPrevious initial depth values d11～d1tThe same, the same mapping function; however, since various system errors, environmental noises, and the like may exist in the actual detection process, the final mapping function R, i.e., the depth value correction rule for correcting the initial depth value, may be formed by performing processing and calibration through a plurality of mapping functions R1 to rt, where R is (R1, R2 … … rt).
In the subsequent output frames, each output frame only needs to correspond to one detection frame, for example, detection is carried out by a detection light pulse without delay to obtain an initial depth value diThe initial depth value d is addediBy said mapping functionCorrecting the number R to obtain an actually measured depth value Di。
According to the distance measuring method of the flight time sensing system, the influence of multiple reflected lights on the detection result is eliminated by delaying the detection light pulse, so that the detection result is corrected, and the accuracy of distance detection is improved.
The invention further provides a flight time sensing system.
Fig. 8 is a schematic structural diagram of a time-of-flight sensing system according to an embodiment of the present invention.
The time-of-flight sensing system comprises: a light source module 701, a sensing module 702, a control module 703 and a processing module 704.
The light source module 701 is configured to emit detection light pulses, where the detection light is pulse detection light, and the light source module 701 is configured to sequentially emit detection light pulses according to a set time sequence;
the sensing module 702 includes a sensing array formed by a plurality of pixel units, and is configured to receive reflected light of the detection light pulse after being reflected by the object to be measured, and obtain characteristics of the reflected light. Each pixel cell receives the reflected light and converts the light signal into an electrical signal. Each pixel unit is connected to an integration circuit, and obtains the charge amount corresponding to the flight time of light by integrating the electrical signal converted by the reflected light. The integrating circuit comprises three shutters G1-G3 which can be respectively realized through a capacitance structure, ambient light and reflected light are received by pixel units of the sensing array, optical signals are converted into electric signals, the electric signals are subjected to charge accumulation through the shutters G1, G2 and G3, and the charge amount is in direct proportion to light energy.
The control module 703 is connected to the light source module 701, and configured to control the light source module 701 to delay detection of light pulses frame by frame according to a detection frame sequence. In one embodiment, the light source module 701 may be controlled to delay the detection light pulse frame by frame at the same time interval. In other embodiments, the delay time interval may be reduced frame by frame, and the delay time interval is larger between the first several detection frames to improve efficiency. And in a plurality of detection frames corresponding to a single output frame, the maximum delay time of the detection light pulse is greater than or equal to the pulse width of the detection light pulse.
The control module 703 is also connected to the integration timing of the integration circuit of each pixel unit of the sensing array 702.
The processing module 704 is connected to the sensing module 702, and is configured to perform the following processing: acquiring initial depth values of all detection frames according to the detection light and the reflected light; acquiring a depth value curve of the initial depth value changing along with the delay time of the detection light pulse according to the initial depth value of each detection frame and the delay time of the corresponding detection light pulse; and obtaining the actually measured depth value of a single output frame corresponding to a plurality of detection frames according to the depth value curve. The processing module 704 is configured to fit the initial depth value and the corresponding delay time of the detected light pulse to obtain the depth value curve, where the fitting method includes 2D difference, polynomial fitting, or piecewise function fitting.
The time-of-flight sensing system comprises a pixel array composed of a plurality of pixel units; the processing module 704 is configured to obtain, for each pixel unit, an initial depth value of each detection frame, and obtain a depth value curve corresponding to each pixel unit.
In some embodiments, in the case that there is more than one turning point on the depth value curve, the processing module 704 is configured to select an initial depth value corresponding to a suitable turning point as the measured depth value according to the requirement of the ranging accuracy. In another embodiment, the measured depth value may be determined as an initial depth value corresponding to any point between a point on the depth value curve where the first depth value decreases with a delay time and a starting point where the depth value decreases linearly with a maximum slope with the delay time.
In other embodiments, the processing module 704 is configured to use an initial depth value corresponding to a starting point on the depth value curve where the depth value linearly decreases with a maximum slope along a delay time as the measured depth value.
In other specific embodiments, the processing module 704 is further configured to obtain a depth value correction rule according to the measured depth value of the output frame and the corresponding initial depth values of the plurality of detection frames; and correcting the initial depth value of each subsequent detection frame according to the depth value correction rule to obtain the actually measured depth value of each detection frame, wherein each detection frame corresponds to an output frame at the moment so as to improve the detection efficiency.
In some embodiments, the processing module 704 may further obtain, as subsequent detection parameters, appropriate delay times, and the like in the process of obtaining actually measured depth values by processing the initial depth values obtained for the multiple detection frames of the first output frame; the delay time Ts corresponding to the actually measured depth value of the first output frame may also be obtained, and in the detection process of the subsequent frame, the light source module 701 may be directly controlled to detect the pulse light pulse delay Ts, and the detection result of a single detection frame is used as the actually measured depth value of the corresponding output frame, so that the detection efficiency may be improved, and the power consumption of the system may be reduced.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (16)
1. A method of ranging a time-of-flight sensing system, comprising:
delaying the detection light pulse frame by frame in the order of the plurality of detection frames;
receiving reflected light of the detection light pulse after being reflected by the object to be detected, and acquiring an initial depth value of each detection frame;
acquiring a depth value curve of the initial depth value changing along with the delay time of the detection light pulse according to the initial depth value of each detection frame and the delay time of the corresponding detection light pulse;
and obtaining the actually measured depth values of the single output frame corresponding to the plurality of detection frames according to the depth value curve.
2. A method of ranging of a time-of-flight sensing system according to claim 1, wherein the detection light pulses are delayed frame by frame at the same time interval.
3. A method of ranging of a time-of-flight sensing system according to claim 1, wherein the time-of-flight sensing system comprises a pixel array constituted by a plurality of pixel units; respectively acquiring initial depth values of all detection frames aiming at all pixel units; and respectively acquiring the depth value curves corresponding to the pixel units.
4. The method of claim 1, wherein the initial depth value corresponding to the starting point of the linear decrease of the depth value with the maximum slope along the delay time on the depth value curve is used as the measured depth value.
5. A ranging method according to claim 1, wherein in case that there is more than one turning point on the depth value curve, according to the ranging accuracy requirement, selecting an initial depth value corresponding to a suitable turning point as the measured depth value, or using an initial depth value corresponding to any point between a point on the depth value curve where a first depth value decreases with a delay time and a starting point where a depth value decreases linearly with a maximum slope with a delay time as the measured depth value.
6. A method of ranging as claimed in claim 1 wherein fitting an initial depth value to the corresponding delay time of a detected light pulse yields the depth value curve, the method of fitting including 2D difference, polynomial fitting or piecewise function fitting.
7. A method of ranging as claimed in claim 1 wherein the maximum delay time of the detection light pulse is greater than the pulse width of the detection light pulse within a plurality of detection frames corresponding to a single output frame.
8. The method of claim 1, wherein a depth value correction rule is obtained according to the measured depth value of the output frame and the initial depth values of the corresponding detection frames; and correcting the initial depth value of each subsequent detection frame according to the depth value correction rule to obtain the actual measurement depth value of each detection frame, wherein each detection frame corresponds to an output frame.
9. A time-of-flight sensing system, comprising:
the light source module is used for emitting detection light pulses;
the sensing module is used for receiving reflected light of the detection light pulse after being reflected by an object to be detected and acquiring the characteristics of the reflected light;
the control module is connected with the light source module and used for controlling the light source module to delay the detection light pulse frame by frame according to the sequence of a plurality of detection frames;
the processing module is connected with the sensing module and used for carrying out the following processing: acquiring initial depth values of all detection frames according to the detection light and the reflected light; acquiring a depth value curve of the initial depth value changing along with the delay time of the detection light pulse according to the initial depth value of each detection frame and the delay time of the corresponding detection light pulse; and obtaining the actually measured depth values of the single output frame corresponding to the plurality of detection frames according to the depth value curve.
10. The time-of-flight sensing system according to claim 9, wherein the control module is configured to control the light source module to delay the detection light pulse frame by frame at the same time interval.
11. The time-of-flight sensing system of claim 9, comprising a pixel array comprised of a plurality of pixel cells; the processing module is used for respectively obtaining the initial depth value of each detection frame aiming at each pixel unit and respectively obtaining the depth value curve corresponding to each pixel unit.
12. The time-of-flight sensing system of claim 9, wherein the processing module is configured to use an initial depth value corresponding to a starting point on the depth value curve where the depth value linearly decreases with a maximum slope along with a delay time as the measured depth value.
13. The time-of-flight sensing system of claim 9, wherein when there is more than one inflection point on the depth value curve, the processing module is configured to select an initial depth value corresponding to a suitable inflection point as the measured depth value according to a ranging accuracy requirement, or select an initial depth value corresponding to any point between a point on the depth value curve where a first depth value decreases with a delay time and a starting point where a depth value decreases linearly with a maximum slope with a delay time as the measured depth value.
14. The time-of-flight sensing system of claim 9, wherein the processing module is configured to fit an initial depth value to a corresponding delay time of the detected light pulse to obtain the depth value curve, and the fitting method comprises 2D difference, polynomial fitting, or piecewise function fitting.
15. The time-of-flight sensing system of claim 9, wherein the maximum delay time of the detection light pulse is greater than the pulse width of the detection light pulse within a plurality of detection frames corresponding to a single output frame.
16. The time-of-flight sensing system of claim 9, wherein the processing module is further configured to obtain a depth value correction rule according to the measured depth value of the output frame and the initial depth values of the corresponding detection frames; and correcting the initial depth value of each subsequent detection frame according to the depth value correction rule to obtain the actual measurement depth value of each detection frame, wherein each detection frame corresponds to an output frame.
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| JP2021117036A (en) * | 2020-01-23 | 2021-08-10 | 株式会社日立エルジーデータストレージ | Measurement value correction method of range-finding device |
| CN111366943B (en) * | 2020-03-25 | 2022-09-09 | 炬佑智能科技(苏州)有限公司 | Flight time ranging system and ranging method thereof |
| CN111443355B (en) * | 2020-05-22 | 2022-06-10 | 炬佑智能科技(苏州)有限公司 | Ranging method based on TOF module and computer storage medium |
| CN115667989A (en) * | 2020-06-28 | 2023-01-31 | 华为技术有限公司 | Depth image processing method and device |
| CN111896971B (en) * | 2020-08-05 | 2023-12-15 | 上海炬佑智能科技有限公司 | TOF sensing device and distance detection method thereof |
| CN113791422B (en) * | 2020-12-04 | 2024-04-09 | 神盾股份有限公司 | Flying time ranging device and flying time ranging method |
| CN115546306B (en) * | 2022-01-30 | 2023-06-02 | 荣耀终端有限公司 | Camera calibration method and device, electronic equipment and readable storage medium |
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