CN112505715B - ToF sensing device and distance detection method thereof - Google Patents
ToF sensing device and distance detection method thereof Download PDFInfo
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- CN112505715B CN112505715B CN202011442540.7A CN202011442540A CN112505715B CN 112505715 B CN112505715 B CN 112505715B CN 202011442540 A CN202011442540 A CN 202011442540A CN 112505715 B CN112505715 B CN 112505715B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
- G01S17/08—Systems determining position data of a target for measuring distance only
- G01S17/10—Systems determining position data of a target for measuring distance only using transmission of interrupted, pulse-modulated waves
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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
- G01S17/88—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
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Abstract
The application discloses a ToF sensing device and a distance detection method thereof, wherein the ToF sensing device comprises a graphical light source and a sensing array, the graphical light source is used for emitting detection light with a graphical light area, and the sensing array comprises a plurality of pixel units distributed in an array; the distance detection method comprises the following steps: emitting detection light by adopting the graphical light source to irradiate a detection field of view; the method comprises the steps that a sensing array receives reflected light of a measured object in a detection field of view and generates sensing signals, the reflected light forms a bright area comprising bright pixel units and a dark area comprising dark pixel units in the sensing array, the bright area corresponds to a graphical light area of detection light and comprises a plurality of sensing areas, and the dark area is arranged outside the bright area; and acquiring corresponding distance information according to the sensing signals, wherein different sensing areas respectively correspond to different detection precision requirements. The above method enables a higher distance detection accuracy to be obtained while providing as many visible areas as possible.
Description
Technical Field
The application relates to the technical field of sensing, in particular to a ToF sensing device and a distance detection method thereof.
Background
A Time of Flight (ToF) sensor measures the distance, three-dimensional structure, or three-dimensional profile of an object to be measured by detecting the Time interval between transmission and reception of emitted modulated detection light or the phase difference generated from one Time to one Time of the object to be measured. The ToF sensor can simultaneously obtain a gray image and a distance image, and is widely applied to the fields of motion sensing control, behavior analysis, monitoring, automatic driving, artificial intelligence, machine vision, automatic 3D modeling and the like.
In the prior art, the detection fields of view of the respective regions within the detection field of view generally have the same detection accuracy. In actual ToF measurement, because the environment in the measured field of view is complex, there are usually indirect reflected light such as multipath reflection and scattered light, which affects the accuracy of distance detection, and the larger the viewing angle, the more the indirect reflected light affects. In an actual distance detection process, different application requirements usually have different detection accuracy and visual angle requirements. For example, for obstacle avoidance application of a sweeping robot, whether an obstacle exists on the ground in a certain distance range right in front of the robot is only required to be judged, the horizontal and vertical directions all need to have larger visual angles, and the distance precision requirement on the obstacle is lower; for the application of instant positioning and mapping (SLAM), the distance accuracy requirement on the obstacle is higher, and a larger longitudinal visual angle is not needed. Generally, a distance detection device in the prior art cannot meet the requirements of high detection precision and a large visual angle at the same time, and generally can only meet the requirement of a single distance measurement target, so that the application scene is single.
Therefore, how to obtain a high distance detection accuracy and a large visual angle is a problem to be solved at present.
Disclosure of Invention
In view of this, the present application provides a ToF sensing apparatus and a distance detecting method, which can obtain a high detection accuracy in a local area and provide a large visible field angle.
The application provides a distance detection method of a ToF sensing device, wherein the ToF sensing device comprises a graphical light source and a sensing array, the graphical light source is used for emitting detection light with a graphical light area, and the sensing array comprises a plurality of pixel units distributed in an array; the distance detection method comprises the following steps: emitting detection light by adopting the graphical light source to irradiate a detection field of view; the method comprises the steps that a sensing array receives reflected light of a measured object in a detection field of view and generates a sensing signal, the reflected light forms a bright area comprising bright pixel units and a dark area comprising dark pixel units in the sensing array, the bright area corresponds to a graphical light area of detection light and comprises a plurality of sensing areas, and the area outside the bright area is a dark area; and acquiring corresponding distance information according to the sensing signals, wherein different sensing areas respectively correspond to different detection precision requirements.
Optionally, the bright area includes bright pixel units that receive the directly reflected light with intensity greater than the average reflected light intensity, and the dark area includes dark pixel units that do not receive the directly reflected light or receive the directly reflected light with intensity lower than the average reflected light intensity.
Optionally, the intensity of the reflected light received by the bright pixel unit is more than 3 times of the intensity of the reflected light received by the adjacent dark pixel unit.
Optionally, a pattern and a distribution position of the light region of the detection light may be set according to a requirement for detection accuracy of different regions within the detection field of view.
Optionally, the bright area at least includes a first sensing area and a second sensing area, the detection accuracy corresponding to the first sensing area is greater than the detection accuracy corresponding to the second sensing area, and the first sensing area includes a plurality of rows/columns of pixel units closest to the dark area in the bright area.
Optionally, the bright area is located in the lower half of the sensing array, and the dark area is located in the upper half of the sensing array; the first sensing area comprises a plurality of rows of bright pixel units closest to the dark area, and the second sensing area is located below the first sensing area.
Optionally, the bright region includes at least two bar patterns extending along different directions, and an edge region of the bar pattern is used as the second sensing region.
Optionally, the method further includes: and processing the distance information of the multiple sensing areas to realize detection targets with different detection precision requirements.
Optionally, the method for acquiring corresponding distance information according to the sensing signal further includes: acquiring an actual detection value A of each bright pixel unit in a bright area and an actual detection value B of a dark area in the sensor array; correcting the actual detection value A of the bright pixel units in the first sensing area according to the actual detection value B to obtain the corrected detection value A' of each bright pixel unit; acquiring distance information of the measured position corresponding to each bright pixel unit in the partial detection area according to the corrected detection value A'; for the second sensing area, the actual detection value of the bright pixel unit in the sensing area is directly used for acquiring the distance information at the corresponding measured position.
Optionally, the corrected detection value a' is a-B; or, according to the relationship between the non-interference detection value of the bright area and the non-interference detection value of the dark area calibrated in the environment without indirect reflected light and the actual detection value B, correcting the actual detection value A to obtain the corrected detection value A'.
Optionally, the method for calibrating the relationship between the non-interference detection value of the bright area and the non-interference detection value of the dark area includes: under a plurality of measurement conditions in the environment without indirect reflection light, obtaining a plurality of non-interference detection values A0 of a bright area and a plurality of non-interference detection values B0 of a corresponding dark area; by the fitting operation, a relational expression between the no-interference detection value a0 and the no-interference detection value B0 is obtained.
Optionally, the plurality of measurement conditions include: illuminating the diffuse reflection plane plate at different distances; alternatively, the plurality of measurement conditions include: the diffusely reflecting planar panel is illuminated at different light intensities.
Optionally, in relation B 0 ＝γA 0 Performing fitting operation to obtain an influence coefficient gamma of the bright area on the dark area; correcting the actual detection value A according to the actual detection value B and the influence coefficient gamma to obtain a corrected detection value
Or, according to the actual detection value B and the influence coefficient gamma, and the proportion coefficient alpha between the detection values of the pixel units under different light intensities, correcting the actual detection value A to obtain a corrected detection value
Optionally, the actual detection value B of the dark region includes: at least one of a detection value of a single dark pixel cell, an arithmetic average of detection values of a plurality of dark pixel cells, a median of detection values of a plurality of dark pixel cells, a weighted average of detection values of a plurality of dark pixel cells; the non-interference detection value includes: in the calibration process, at least one of the detection value of a single pixel unit, the arithmetic mean value of the detection values of a plurality of pixel units, the median of the detection values of a plurality of pixel units and the weighted mean value of the detection values of a plurality of pixel units; the detection value is a detection quantity related to the light intensity of the reflected light received by the pixel unit.
The present application further provides a ToF sensing device, comprising: a patterned light source for emitting detection light having a patterned light region; the sensing array comprises a plurality of pixel units distributed in an array and is used for receiving reflected light of a measured object; the processor is connected with the graphical light source and the sensing array and used for controlling the graphical light source to emit detection light and acquiring a detection value generated by the sensing array; a memory in which a computer program is stored which is executable by the processor, the computer program being executable by the processor to perform the distance detection method as claimed in any one of the preceding claims.
The ToF sensing device is provided with the graphical light source, corresponding reflected light can generate a bright area and a dark area which are distributed in a graphical mode in the sensing array, and the actual detection value of the dark area is mainly caused by indirect scattered light.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a ToF sensing device according to an embodiment of the present application;
FIG. 2 is a schematic flow chart illustrating a distance detection method according to an embodiment of the present disclosure;
FIG. 3 is a schematic diagram of the distribution of bright and dark regions according to an embodiment of the present application;
FIG. 4 is a timing diagram illustrating a charge accumulation window and the timing of detecting light and reflected light in a distance detection process according to an embodiment of the present disclosure;
FIG. 5 is a timing diagram illustrating a charge accumulation window and the timing of detecting light and reflected light in a distance detection process according to an embodiment of the present disclosure;
FIG. 6 is a schematic diagram of the distribution of bright and dark regions according to an embodiment of the present application;
FIG. 7 is a schematic diagram of the distribution of bright and dark regions according to an embodiment of the present application;
fig. 8 is a schematic diagram of the distribution of bright and dark regions according to an embodiment of the present application.
Detailed Description
As described in the background art, the detection fields of view of the prior art for respective areas within the detection field of view generally have the same distance detection accuracy, and as the angle of visibility increases, the distance detection accuracy is generally more difficult to guarantee due to increased interference of indirect reflected light. In an actual distance detection process, different application requirements usually have different detection accuracy and visible field range requirements.
The method and the device have the advantages that the requirements of local high detection precision are met and the requirement of a visual angle can be met through the imaging detection light and the regional correction processing.
The technical solutions in the embodiments of the present application are clearly and completely described below with reference to the accompanying drawings, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application. The embodiments described below and their technical features may be combined with each other without conflict.
Fig. 1 is a schematic structural diagram of a ToF sensing device according to an embodiment of the invention.
The ToF sensing device comprises a patterned light source 101, a sensing array 102 having a plurality of pixel cells arranged in an array, a processor 103, and a memory 104.
The patterned light source 101 is configured to emit detection light capable of generating a patterned light region. The pattern distribution of the detection light can be set according to the detection precision requirement of each area in the detection field of view. The light region corresponds to a target detection region within the detection field of view where distance detection is required, such that the target region is able to receive illumination of detection light, whereas the non-target region corresponds to a dark region of detection light, which is not required to receive illumination of detection light. The pattern distribution of the light regions of the detection light may be set according to the specific distribution of the target detection regions.
The reflected light of the object to be measured, which reflects the detection light, passes through the optical lens, and forms a bright area corresponding to the light area of the detection light and a dark area located outside the bright area on the sensor array 102.
In some embodiments, the bright region includes bright pixel cells that receive the directly reflected light with an intensity greater than an average reflected light intensity, and the dark region corresponds to a region outside the light region of the detection light, including dark pixel cells located within the bright region that do not receive the directly reflected light or that receive a directly reflected light with an intensity lower than the average reflected light intensity. The average reflected light intensity is an average value of total energy of received reflected light per unit time for all pixel units, and the reflected light includes direct reflected light and other indirect reflected light such as multipath reflected light and scattered light.
In some embodiments, the intensity of the reflected light received by the bright pixel unit is more than 3 times that received by the dark pixel unit, so that the light intensity received by the bright pixel unit is obviously different from that received by the dark pixel unit.
The patterned light source 101 can be formed by shaping the detection light emitted from the point light source with a specific optical shape or by blocking the detection light with a specific pattern, so that the emitted light field thereof generates a light distribution region with a certain pattern. The pattern of the light area can be a line pattern, a spot pattern, a rectangle, an irregular pattern or a combination of various patterns.
The processor 103 is connected to the patterned light source 101 and the sensing array 102, and is configured to control the patterned light source 101 to emit detection light, and acquire sensing signals generated by pixel units in the sensing array 102, so as to obtain corresponding detection values, where the detection values are related to light intensity of reflected light received by the pixel units. In some embodiments, the detection value corresponds to the total amount of induced charges generated by the pixel unit in a certain period of time, and may be an electrical signal in analog or digital form, such as a voltage or a current.
The processor 103 is configured to control the ToF sensing device to perform distance detection.
The memory 104 is connected to the processor 103. The memory 104 stores a computer program executable by the processor 103, which computer program, when executed by the processor 103, enables distance detection.
In the following embodiments, the distance detection method is specifically described.
Fig. 2 is a schematic flow chart of a distance detection method according to an embodiment of the invention.
The distance detection method comprises the following steps:
step S101: and emitting detection light by adopting the graphical light source to irradiate the detection field of view.
The detection light is modulated periodic light waves, specifically, periodic pulse light with a certain duty ratio, or modulated detection light with a certain period and phase such as sine waves. And the light field generated by the detection light has a specific pattern.
And S102, receiving the reflected light of the measured object in the detection field by the sensing array, and generating a sensing signal.
When the detection light irradiates the detection field, the object to be detected in the detection field reflects the detection light to generate a reflected light, and the reflected light returns to the ToF sensing device and is received by the sensing array 102 (see fig. 1).
In the actual detection process, the detection light is reflected after reaching the surface of the object to be detected, the reflected light directly received by the sensing array 102 is direct reflected light, and the flight time of the direct reflected light corresponds to the distance of the object to be detected. In some cases, part of the reflected light reaches the sensor array after being reflected for multiple times or the detection light reaches the sensor array after being reflected for multiple times by the object to be detected, and the reflected light is multipath reflected light (MPI). Most of the reflected light received by the sensor array is directly reflected light, and the MPI or other indirect reflected light accounts for a small amount, but the indirect reflected light still affects the distance detection result.
Meanwhile, in the process that the reflected light passes through the lens of the ToF detecting device and irradiates on the sensor array, due to the optical structure of the lens or other factors, part of the reflected light is scattered and becomes scattered light, and irradiates on the pixel unit at a non-corresponding position, thereby affecting the distance detection result of the pixel unit receiving the scattered light.
Because a patterned light region exists in the emission light field of the detection light generated by the patterned light source, the detection light is reflected and then irradiates the sensor array, and a corresponding bright region and a corresponding dark region are generated on the sensor array. In some embodiments, the bright regions comprise bright pixel cells that receive the directly reflected light at an intensity greater than an average reflected light intensity, and the dark regions comprise dark pixel cells located within the bright regions that do not receive the directly reflected light or that receive a directly reflected light at an intensity less than the average reflected light intensity. In other embodiments, the light pixel cells receive more than 3 times the intensity of the reflected light as the adjacent dark pixel cells.
After the reflected light reaches the sensing array, sensing signals are generated on the bright pixel units mainly in the bright area. Meanwhile, due to the existence of light rays of indirect reflected light such as scattered light and multipath reflected light, crosstalk of sensing signals between adjacent pixel units and other factors, the dark pixel units in the dark area in the bright area also generate certain sensing signals. Generally, the sensing signal generated by a dark pixel cell in the dark area is greatly different from the sensing signal generated by a bright pixel cell in the bright area, and the sensing signal generated by a bright pixel cell is at least 3 times larger than the sensing signal generated by an adjacent dark pixel cell, and the sensing signal is usually a voltage or current signal.
In an embodiment of the present invention, the patterned bright area in the sensor array further includes a plurality of sensor areas, which respectively correspond to different detection accuracy requirements. The pattern and distribution position of the light region of the detection light may be set according to the detection accuracy requirements for different regions within the detection field of view. The bright regions may include a plurality of sensing regions extending in the same direction, or a plurality of sensing regions extending in different directions.
Step S103: and acquiring corresponding distance information according to the sensing signals, wherein different sensing areas respectively correspond to different detection precision requirements.
The sensing areas at different positions are affected differently by indirect reflected light by adjusting the distribution pattern of the bright areas and the position and size distribution of each sensing area, so that each sensing area has different detection precision.
In some embodiments, the bright region includes at least a first sensing region and a second sensing region, the first sensing region corresponds to a detection precision greater than a detection precision corresponding to the second sensing region, and the first sensing region includes rows/columns of pixel cells in the bright region that are closest to the dark region.
Fig. 3 is a schematic diagram illustrating a distribution of bright regions in a sensor array according to another embodiment of the present invention.
The bright area 301 is located at the lower half part of the sensing array 102, and the dark area 302 is located at the upper half part of the sensing array 102; the bright region includes a first sensing region 3011 and a second sensing region 3012, the first sensing region 3011 includes a plurality of rows of bright pixel units closest to the dark region 302, and the second sensing region 3012 is located below the first sensing region.
In the process of distance detection, after an actual detection value obtained by a bright pixel unit in the first sensing region 3011 is corrected, distance information is obtained according to the corrected detection value; the actual detection values obtained by the bright pixel units in the second sensing region 3012 do not need to be corrected, and distance information can be obtained directly according to the actual detection values or obtained through the corrected detection values. The detection accuracy of the distance information of the object to be measured in the detection area corresponding to the first sensing area 3011 is higher, and the detection requirement of higher accuracy can be met.
After the detected distance information is obtained, the distance information of each sensing area can be processed to realize detection targets with different detection precision requirements. The detection target includes: judging whether an obstacle exists or not, and acquiring at least one of obstacle height information and SLAM drawing. The detection accuracy requirements of different detection targets for the distance information are different, for example, the accuracy requirement for the distance information is low for judging whether an obstacle exists, and the acquisition of the specific height of the obstacle and the implementation of SLAM require that the distance information has relatively high detection accuracy.
In some embodiments, the distance information corresponding to the second sensing region 3012 may be processed to determine whether an obstacle exists in the detection region corresponding to the second sensing region 3012, and the distance information corresponding to the first sensing region 3011 may be processed to obtain a detection target with higher detection accuracy requirement, for example, perform SLAM drawing. The second sensing region 3012 occupies a large number of pixels, so that the requirement for detecting a large field angle can be met, and the detection value of the first sensing region 3011 is corrected by the detection value of the dark pixel unit, so that the detection accuracy of the first sensing region 3011 can be improved, and the requirement for high detection accuracy can be met. Therefore, in the embodiment of the invention, the bright and dark area distribution generated by the graphical light source on the sensing array is utilized, the requirements of a larger detection visual angle and high detection precision are met, and various detection requirements can be met.
In order to improve the correction effect as much as possible and improve the detection accuracy of the first sensing region 3011, the bright pixel units in the first sensing region 3011 should be as close as possible to the dark pixel units in the dark region. In some embodiments, the first sensing region 3011 occupies 1-10 rows of pixels.
In some embodiments of the present invention, a specific method for modifying the detection data of the first sensing region 3011 to improve the detection accuracy of the part of the sensing region includes: acquiring an actual detection value A of each bright pixel unit in a first sensing area 3011 in the sensing array and an actual detection value B of a dark area; correcting the actual detection value A of the bright pixel units in the first sensing area according to the actual detection value B to obtain a corrected detection value A' of each bright pixel unit; acquiring distance information of the measured position corresponding to each bright pixel unit in the partial detection area according to the corrected detection value A'; the second sensing region 3012 may directly acquire distance information at the corresponding measured position from the actual detection value of the bright pixel cell in the sensing region, or may acquire distance information from the corrected detection value. In this embodiment, only the actual detection values of the bright pixel units in the first sensing region 3011 are corrected, and the data processing amount in the correction process can be reduced.
The actual detection value B of the dark region includes: at least one of a detection value of a single dark pixel cell, an arithmetic average of detection values of a plurality of dark pixel cells, a median of detection values of a plurality of dark pixel cells, a weighted average of detection values of a plurality of dark pixel cells.
Generally, the indirect reflection light affects the adjacent pixel units in the sensor array more uniformly, and the indirect reflection light affects not only the detection value of the pixel unit in the dark area, but also the bright pixel unit in the bright area adjacent to the dark area. Therefore, the bright area may be corrected using the actual detection value B of the dark area closest to the bright pixel unit, or the average, weighted average, or median of the actual detection values B of several dark areas closest to the bright pixel unit.
In an ideal state, since the dark area does not substantially receive the directly reflected light, and the dark area does not generate an induced signal during the detection process, the theoretical detection value in the dark area is 0. However, in the actual detection process, due to the influence of indirect reflected light such as scattered light or multipath reflected light, a sensor signal is generated also in a dark pixel unit in a dark region, and an actual detection value B ≠ 0 is acquired in the detection process.
The actual detection value a is a '+ Δ, B is B' + Δ, Δ is a detection value generated by indirect reflected light, and a 'and B' are corrected detection values generated by direct reflected light. In one embodiment, since the dark region does not receive the directly reflected light or the received directly reflected light is weak, B' may be approximately equal to 0, and the actual detection values B are all generated by the indirectly reflected light, i.e., B ═ Δ; thereby obtaining a corrected detection value a' ═ a-B.
In another embodiment, the influence of crosstalk or other factors due to signals transmitted in the semiconductor substrate between adjacent pixel units can be further considered, even if the dark area has no influence of indirect reflection light, the pixel units in the dark area can still generate sensing signals due to crosstalk or other factors of sensing signals generated in the bright area. In a scene without indirect reflected light, a certain corresponding relation exists between the non-interference detection value of the bright area and the non-interference detection value of the dark area. The correspondence may be calibrated in a scene without indirect reflected light.
Specifically, the calibration method comprises the following steps: under the environment of indirect reflected light, a plurality of non-interference detection values A of bright pixel units in a bright area under a plurality of measurement conditions are acquired 0 And a plurality of non-interference detection values B of corresponding dark regions 0 (ii) a Obtaining a non-interference detection value A through fitting operation 0 And a non-interference detection value B 0 The relation between them.
The non-interference detection value includes: in the calibration process, at least one of the detection value of a single pixel unit, the arithmetic mean value of the detection values of a plurality of pixel units, the median of the detection values of the plurality of pixel units and the weighted mean value of the detection values of the plurality of pixel units; the detection value is a detection quantity related to the light intensity of the reflected light received by the pixel unit.
The plurality of measurement conditions may be different detection distances, or different detection light intensities. The method specifically comprises the following steps: irradiating the diffuse reflection plane plate for multiple times at different distances, and sequentially acquiring multiple non-interference detection values A of bright areas 0 And a plurality of non-interference detection values B of dark regions 0 (ii) a Or, the diffuse reflection plane board is irradiated by different light intensities, and a plurality of non-interference detection values A of the bright area are sequentially obtained 0 And a plurality of non-interference detection values B of dark regions 0 . The non-interference detection value A 0 The detection value of one bright pixel unit in the bright region, the arithmetic mean value of the detection values of a plurality of bright pixel units,At least one of a median of the detection values of the plurality of bright pixel cells and a weighted average of the detection values of the plurality of bright pixel cells.
In one embodiment, a plurality of non-interference detection values A are obtained 0 And a corresponding plurality of non-interference detection values B 0 Then, the relation B is used 0 ＝γA 0 Performing fitting operation to obtain the influence coefficient gamma of the bright pixel unit to the dark pixel unit, correcting the actual detection value A according to the actual detection value B and the influence coefficient gamma, and correcting the detection value
The formula for the specific modification is derived as follows:
A＝A'+Δ (1)
B＝B'+Δ (2)
from the calibrated influence coefficients γ, B ═ γ a', we obtain:
B＝γA'+Δ (3)
the formulas (1) to (3) give:
A-B＝(1-γ)A' (4)
thereby obtaining:
by correcting the actual detection value a using the above formula (5), a more accurate corrected detection value a' can be further obtained.
In some embodiments, the non-interference detection value B that may pass through one of the dark regions 0 And a non-interference detection value A of a bright area in the vicinity of the dark area 0 And obtaining the influence coefficient gamma after fitting, wherein the influence coefficient gamma is used as the influence coefficient corresponding to all dark areas in the whole sensing array. In other embodiments, fitting calculation may be performed on the dark regions at different positions, to obtain influence coefficients corresponding to different dark regions, and different influence coefficients are used to correct bright pixel units near different dark regions.
In other embodimentsIn this case, the influence of different intensities received by the pixel unit on the indirectly scattered light can be further considered. In the actual detection process, the detection values are not linearly changed along with the influence of the light intensity, a proportionality coefficient alpha exists between the detection values under different light intensities, and the corrected detection value B 'is equal to gamma A' and delta A ＝α·Δ B 。
The proportional coefficient alpha can be obtained by calibrating a relation curve of light intensity and a detection value, and a specific numerical value of the proportional coefficient alpha can be obtained according to the calibrated relation curve and the light intensity received by each pixel unit in the actual detection process.
Correcting the actual detection value A by combining the proportional coefficient alpha, the influence coefficient gamma and the actual detection value B, and correcting the detection value
The formula for the specific modification is derived as follows:
A＝A'+Δ A ； (6)
from B ═ B' + Delta B Obtaining:
αB＝αB'+αΔ B ； (7)
formulae (6) to (7) and Δ A ＝α·Δ B Obtaining:
A-αB＝A'-αB'； (8)
from the calibrated influence coefficients γ, B ═ γ a', we obtain:
A-αB＝A'-αγA'；
thereby obtaining:
by correcting the actual detection value a according to the formula (9), a more accurate correction value can be obtained.
Acquiring distance information of the measured position corresponding to each bright pixel unit according to the corrected detection value A' aiming at the corrected partial sensing area; and the part of the sensing area which is not corrected directly obtains the distance information at the corresponding measured position according to the actual detection value A.
In another embodiment, the actual detection values of all bright pixel units in the first sensing region 3011 and the second sensing region 3012 may be corrected, and the distance information corresponding to the first sensing region 3011 and the second sensing region 3012 may be obtained according to the corrected detection values after correction. Since the second sensing region 3012 is far from the dark region 302, the degree of influence of indirect reflected light greatly varies, and even if correction is performed, the detection accuracy is lower than that of the first sensing region 3011.
Referring to fig. 4, in an embodiment, the detection light LO is modulated pulsed light with a width T, induced charges generated by the pixel units are accumulated through three consecutive accumulation windows G1, G2 and G3, and G1 is used for accumulating detection values generated by ambient light to obtain actual detection values a1 and B1; g2 and G3 are used to accumulate detection values produced by the detection light and the ambient light together, respectively, to obtain actual detection values a2, B2 and A3, B3. The actual detection values a1, a2, and A3 are corrected by the above-described method to obtain corrected detection values a1 ', a2 ', and A3 '.
In this embodiment, the accumulation windows G1, G2, and G3 have window durations equal to the pulse width of the detection light, which is T, and the rising edge of the pulse of the detection light is aligned with the open edge of the accumulation window G2.
Based on the corrected detection values a1 ', a2 ' and A3 ', the distance at the measured position corresponding to each bright pixel cell in the corresponding bright area can be obtained:
in other embodiments, the accumulation windows G1, G2, and G3 and the timing of detecting the light LO may also be adjusted, and the calculation of the corresponding distance information d may also be adjusted accordingly.
In other embodiments, the detection light may be a modulated continuous sine wave, and the received directly reflected light may also be a continuous sine wave.
Referring to fig. 5, in one embodiment, a timing diagram of a charge accumulation window and detection light and reflection light in a distance detection process is shown.
The period of the reflected light is T, and in one period T, the induced charges of the reflected light are sequentially accumulated within delta T time to obtain an actual detection value c (tau) 0 )、c(τ 1 )、c(τ 2 ) And c (τ) 3 ). Correcting each actual detection value to obtain a corrected detection value c (tau) 0 )'、c(τ 1 )'、c(τ 2 ) ' and c (τ) 3 )'。
Thereby obtaining a phase difference
Thus, the distance:
no matter what distance detection method is adopted, the actual detection value A needs to be obtained, and the influence of indirect reflected light on the detection value can be reduced and the accuracy of the final distance d can be improved through the method from the corrected detection value A' obtained by correcting the actual detection value A.
Fig. 6 is a schematic diagram illustrating a distribution of bright areas on a sensor array according to an embodiment of the invention.
In this embodiment, the bright areas on the sensing array include a first sensing area 6011 and a second sensing area 6012.
In this embodiment, the bright region includes two bar patterns along the x-axis direction (pixel row direction) and the y-axis direction (pixel column direction), including several rows of pixels at the bottom of the sensor array and several columns of pixels in the middle. The first sensing area 6011 is located in an edge area of the bright area 601 adjacent to the sub-area 602, and includes a plurality of bright pixel units distributed in a row direction and a column direction.
The detection accuracy of the first sensor region 6011 can be improved by correcting the actual detection values of the bright pixel cells in the first sensor region 6011 with the detection values of the dark pixel cells in the dark region 602. The second sensing area 6012 may be configured to detect local areas in the horizontal direction and the vertical direction in the detection view field, and determine whether an obstacle exists in the corresponding detected area, where the detection accuracy of the second sensing area 6012 meets requirements for obstacles. By processing the distance information of the first sensing area 6011 with higher detection accuracy, the detection accuracy of the actual distance to the obstacle and the specific height can be improved, and the requirement of a high-accuracy application scene is met.
In one embodiment, the ToF sensing device is applied to a sweeping robot, and only needs to pay attention to information of obstacles near the ground, and a graphical light source capable of generating a bright area as shown in fig. 6 is adopted, so that the detection of whether obstacles exist near the ground in the horizontal direction of the ground and whether obstacles exist in the vertical direction of the ground on the advancing path of the sweeping robot and the detection of the specific height of the obstacles can be met. When obstacles exist near the ground, the sweeping robot can carry out treatment such as avoidance in advance without accurately knowing the accurate distance and height of the obstacles; if an obstacle exists in the height direction of the sweeping robot, for example, the obstacle exists above the forward path of the robot, the position of the obstacle and the distance between the obstacle and the ground need to be accurately obtained so as to judge whether the sweeping robot can pass below the obstacle. Therefore, by setting the first sensing area 6011 and the second sensing area 6012, detection with different accuracy can be achieved for different areas. For a detection area needing higher precision, the requirement of detection precision can be met by setting different two area graphs.
Please refer to fig. 7, which is a schematic diagram illustrating a distribution of bright areas according to another embodiment of the present invention.
In this embodiment, the bright regions 701 include two bar chart rows in the pixel row and pixel column directions, and the first sensing region 7011 is located at an edge region of the bright regions 701.
By moving the lens of the TOF apparatus, the bright region 701 pattern can detect more regions within the detection field of view.
Please refer to fig. 8, which is a schematic diagram illustrating a distribution of bright regions according to another embodiment of the present invention.
In this embodiment, the bright area 801 includes a plurality of inclined bar patterns, including a first sensing area 8011 and a second sensing area 8012, where the first sensing area 8011 is located at an edge of the bright area 801 where the dark area 802 meets.
The strip-shaped patterns of the bright regions 801 are obliquely arranged, and can simultaneously correspond to detection regions in horizontal and vertical directions in a detection field, so that more detection regions can be swept in the motion process of the TOF device, and obstacle avoidance and SLAM application in more regions can be realized.
The pattern of the bright area generated by the patterned light source of the present invention, and the pattern and the position distribution of the sensing area in the bright area are not limited to the above embodiments. Based on the basic concept of the present invention, those skilled in the art can set different bright area patterns and different distributions of sensing areas according to actual situations.
That is, the above description is only an embodiment of the present application, and not intended to limit the scope of the present application, and all equivalent structures or equivalent flow transformations made by using the contents of the specification and the drawings, such as mutual combination of technical features between various embodiments, or direct or indirect application to other related technical fields, are included in the scope of the present application.
Claims (12)
1. A distance detection method of a ToF sensing device is characterized in that the ToF sensing device comprises a graphical light source and a sensing array, wherein the graphical light source is used for emitting detection light with a graphical light area, and the sensing array comprises a plurality of pixel units distributed in an array; the distance detection method comprises the following steps:
emitting detection light by adopting the graphical light source to irradiate a detection field of view;
the method comprises the steps that a sensing array receives reflected light of a measured object in a detection field of view and generates sensing signals, the reflected light forms a bright area comprising bright pixel units and a dark area comprising dark pixel units in the sensing array, the bright area corresponds to a graphical light area of detection light and comprises a plurality of sensing areas, different sensing areas correspond to different detection precision requirements respectively, and the area outside the bright area is a dark area; the bright area at least comprises a first sensing area and a second sensing area, the detection precision corresponding to the first sensing area is higher than that corresponding to the second sensing area, and the first sensing area comprises a plurality of rows/columns of pixel units which are closest to the dark area in the bright area;
acquiring corresponding distance information according to the sensing signal, wherein the distance information comprises the following steps: acquiring an actual detection value A of each bright pixel unit in a bright area and an actual detection value B of a dark area in the sensing array; correcting the actual detection value A of the bright pixel units in the first sensing area according to the relationship between the interference-free detection value of the bright area and the interference-free detection value of the dark area calibrated in the environment without indirect reflected light and the actual detection value B to obtain the corrected detection value A' of each bright pixel unit; acquiring distance information of the measured position corresponding to each bright pixel unit in the first sensing area according to the corrected detection value A'; for the second sensing area, the actual detection value of the bright pixel unit in the sensing area is directly used for acquiring the distance information at the corresponding measured position.
2. The distance detection method according to claim 1, wherein the bright regions comprise bright pixel cells in which the intensity of the received directly reflected light is greater than the average reflected light intensity, and the dark regions comprise dark pixel cells in which the directly reflected light is not received or the intensity of the received directly reflected light is lower than the average reflected light intensity.
3. The distance detection method according to claim 1, wherein the intensity of the reflected light received by the bright pixel unit is more than 3 times the intensity of the reflected light received by the adjacent dark pixel unit.
4. The distance detection method according to claim 1, wherein a pattern and a distribution position of the light region of the detection light are set in accordance with a requirement for detection accuracy for different regions within a detection field of view.
5. The distance detection method according to claim 1, wherein the bright area is located in a lower half of the sensor array, and the dark area is located in an upper half of the sensor array; the first sensing area comprises a plurality of rows of bright pixel units closest to the dark area, and the second sensing area is located below the first sensing area.
6. The distance detection method according to claim 1, wherein the bright region includes at least two bar patterns extending in different directions, with the bar pattern edge region as the second sensing region.
7. The distance detection method according to claim 1, further comprising: and processing the distance information of the multiple sensing areas to realize detection targets with different detection precision requirements.
8. The distance detection method according to claim 1, wherein the method of calibrating the relationship between the non-interference detection value of the bright area and the non-interference detection value of the dark area includes: under a plurality of measurement conditions in the environment without indirect reflection light, obtaining a plurality of non-interference detection values A0 of a bright area and a plurality of non-interference detection values B0 of a corresponding dark area; by the fitting operation, a relational expression between the non-interference detection value a0 and the non-interference detection value B0 is obtained.
9. The distance detection method according to claim 8, wherein the plurality of measurement conditions include: illuminating the diffuse reflection plane plate at different distances; alternatively, the plurality of measurement conditions include: the diffusely reflecting planar panel is illuminated at different light intensities.
10. The distance detection method according to claim 8, wherein the relationship B 0 ＝γA 0 Performing fitting operation to obtain an influence coefficient gamma of the bright area on the dark area; correcting the actual detection value A according to the actual detection value B and the influence coefficient gamma to obtain a corrected detection value
Or, according to the actual detection value B and the influence coefficient gamma, and the proportion coefficient alpha between the detection values of the pixel units under different light intensities, correcting the actual detection value A to obtain a corrected detection value
11. The distance detection method according to claim 8, wherein the actual detection value B of the dark region includes: at least one of a detection value of a single dark pixel cell, an arithmetic average of detection values of a plurality of dark pixel cells, a median of detection values of a plurality of dark pixel cells, a weighted average of detection values of a plurality of dark pixel cells; the non-interference detection value includes: in the calibration process, at least one of the detection value of a single pixel unit, the arithmetic mean value of the detection values of a plurality of pixel units, the median of the detection values of the plurality of pixel units and the weighted mean value of the detection values of the plurality of pixel units; the detection value is a detection quantity related to the light intensity of the reflected light received by the pixel unit.
12. A ToF sensing device, comprising:
a patterned light source for emitting detection light having a patterned light region;
the sensing array comprises a plurality of pixel units distributed in an array and is used for receiving reflected light of a measured object;
the processor is connected with the graphical light source and the sensing array and used for controlling the graphical light source to emit detection light and acquiring a detection value generated by the sensing array;
a memory in which a computer program executable by the processor is stored, the computer program being executable by the processor to perform the distance detection method according to any one of claims 1 to 11.
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