CN114660576A - Calibration method and system of TOF module - Google Patents

Calibration method and system of TOF module Download PDF

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Publication number
CN114660576A
CN114660576A CN202011533547.XA CN202011533547A CN114660576A CN 114660576 A CN114660576 A CN 114660576A CN 202011533547 A CN202011533547 A CN 202011533547A CN 114660576 A CN114660576 A CN 114660576A
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tof
module
tof module
end assembly
assembly
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钟柯松
蔡赞赞
郑锡斌
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Yuyao Sunny Optical Intelligence Technology Co Ltd
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Yuyao Sunny Optical Intelligence Technology Co Ltd
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Priority to CN202011533547.XA priority Critical patent/CN114660576A/en
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/497—Means for monitoring or calibrating
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/481—Constructional features, e.g. arrangements of optical elements
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/80—Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Computer Vision & Pattern Recognition (AREA)
  • Theoretical Computer Science (AREA)
  • Optical Radar Systems And Details Thereof (AREA)

Abstract

A calibration method and a system of a TOF module are provided, the calibration method of the TOF module comprises the following steps: diffusing the output light beam projected by the projecting end component of the TOF module to form a diffused light beam with an enlarged emission angle, so that the field angle of the projecting end of the TOF module is enlarged; reflecting the diffused light beam to a receiving end assembly of the TOF module so as to be received by the receiving end assembly to acquire at least one TOF image; and calibrating the internal reference and the external reference of the TOF module based on the at least one TOF image so as to improve the calibration precision of the TOF module with the projection end field angle smaller than the receiving end field angle.

Description

Calibration method and system of TOF module
Technical Field
The invention relates to the technical field of TOF (time of flight), in particular to a calibration method and a calibration system of a TOF module.
Background
In recent years, with the rapid development of 3D imaging technology, TOF imaging technology is also developed accordingly, so that TOF modules are gradually applied to more and more fields, such as somatosensory control, behavior analysis, monitoring, automatic driving, artificial intelligence, machine vision or automatic 3D modeling and the like. The TOF module generally measures depth information Of an object to be measured (or an object to be measured) by a Time Of Flight (TOF) method. Specifically, the time-of-flight method is used for measuring a three-dimensional structure or a three-dimensional profile of an object to be measured by measuring a time interval t between transmission and reception of an actively-transmitted pulse signal (i.e., a pulse ranging method) or a phase difference generated when laser light makes a round trip to the object to be measured (i.e., a phase difference ranging method) to convert the distance into a distance of the object to be photographed, and is used for generating depth information to realize measurement of the three-dimensional structure or the three-dimensional profile of the object to be measured, thereby obtaining a gray image and the depth information of the object to be measured.
At present, the field angle of a projecting end and the field angle of a receiving end in a TOF module in the market are generally matched with each other, for example, the field angles of the projecting end and the receiving end of the TOF module (i.e., the horizontal field angle × the vertical field angle) are generally 60 ° × 45 ° or 72 ° × 55 °, so that the receiving end of the TOF module can receive sufficient light intensity information, so as to completely calibrate the TOF module. However, for TOF modules mounted on apparatuses such as a sweeping robot, the field angle of the projecting end of the TOF module is often smaller than that of the receiving end, and even much smaller than that of the receiving end (for example, a line type TOF module, the field angle of the projecting end is often 100 ° × 5 ° or 120 ° × 10 ° to project a line type light spot). Therefore, because the field angle of the projecting end of the TOF modules is smaller than that of the receiving end of the TOF modules, a dark angle appears on a chip of the receiving end of the TOF module, even most areas cannot receive sufficient light intensity information, and therefore the calibration accuracy of the TOF module is seriously reduced, and even the TOF module cannot be calibrated.
Disclosure of Invention
One advantage of the present invention is to provide a calibration method and system for a TOF module, which can improve the calibration accuracy for TOF modules with a smaller field angle at the projection end than at the receiving end.
Another advantage of the present invention is to provide a calibration method and a calibration system for a TOF module, wherein in an embodiment of the present application, the calibration method for the TOF module can solve the problem of calibration accuracy reduction caused by a dark edge or a dark corner area on a receiving end chip of the TOF module.
Another advantage of the present invention is to provide a calibration method and a calibration system for a TOF module, wherein in an embodiment of the present application, the calibration method for the TOF module can calibrate a dark corner region and a dark edge region on a receiving end chip of the TOF module, which is beneficial to improving calibration accuracy for the TOF module.
Another advantage of the present invention is to provide a calibration method of a TOF module and a system thereof, wherein in an embodiment of the present application, the calibration method of the TOF module can enable the receiving end chip to receive light intensity information with sufficient intensity by improving fixed phase noise precision of the receiving end chip, so as to improve calibration precision.
Another advantage of the present invention is to provide a calibration method of a TOF module and a system thereof, wherein in an embodiment of the present application, the calibration method of the TOF module can increase a field angle of a projection end of the TOF module by a light-homogenizing element, so as to improve a fixed phase noise precision of the receiving end chip, so as to calibrate the TOF module with high precision.
Another advantage of the present invention is to provide a calibration method of a TOF module and a system thereof, wherein in an embodiment of the present application, the calibration method of the TOF module can further diffuse a beam divergence angle through the additionally arranged dodging element to reduce or eliminate a dark edge or a dark corner area appearing on the receiving end chip, so that the receiving end chip can obtain sufficient light intensity information.
Another advantage of the present invention is to provide a calibration method of a TOF module and a system thereof, wherein in an embodiment of the present application, the calibration method of the TOF module can improve the calibration accuracy of the TOF module through simple operations.
Another advantage of the present invention is to provide a calibration method and a system thereof for a TOF module, wherein in an embodiment of the present invention, the calibration method for the TOF module can greatly reduce the difficulty of performing high-precision calibration on the TOF module with a smaller field angle at a projection end than at a receiving end, which is beneficial to popularization and promotion in industry.
Another advantage of the present invention is to provide a calibration method of a TOF module and a system thereof, wherein in an embodiment of the present invention, the calibration method of the TOF module can fully utilize optical energy emitted by a projection end assembly of the TOF module, so as to improve the effective utilization rate of the optical energy.
Another advantage of the present invention is to provide a calibration method and system for TOF module, wherein expensive materials or complex structures are not required in the present invention to achieve the above objectives. Therefore, the invention successfully and effectively provides a solution, not only provides a simple calibration method and a simple calibration system for the TOF module, but also increases the practicability and reliability of the calibration method and the calibration system for the TOF module.
To achieve at least one of the above advantages or other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a calibration method for a TOF module includes:
diffusing the output light beam projected by the projecting end component of the TOF module to form a diffused light beam with an enlarged emission angle, so that the field angle of the projecting end of the TOF module is enlarged;
reflecting the diffused light beam to a receiving end assembly of the TOF module so as to be received by the receiving end assembly to acquire at least one TOF image; and
and calibrating the internal parameters and the external parameters of the TOF module based on the at least one TOF image.
In an embodiment of the invention, the step of diffusing the output light beam projected by the projecting end module of the TOF module to form a diffused light beam with an enlarged emission angle, so that the field angle of the projecting end of the TOF module is enlarged includes the steps of:
adding a dodging element to the field of view of the projecting end assembly of the TOF module; and
the output light beam projected through the projection end assembly is diffused by the dodging element to increase a divergence angle of the output light beam.
In an embodiment of the invention, in the step of diffusing, by the dodging element, the output light beam projected by the projection end assembly to increase a divergence angle of the output light beam:
one-dimensionally diffusing the output beam projected through the projection end assembly to form the diffused beam with an increased vertical divergence angle.
In an embodiment of the invention, in the step of diffusing, by the dodging element, the output light beam projected by the projection end assembly to increase a divergence angle of the output light beam:
two-dimensionally diffusing an output beam projected through the projection end assembly to form the diffused beam with an increased horizontal and vertical divergence angles.
In an embodiment of the invention, the light homogenizing element is one selected from a diffuser, a diffractive optical element and a refraction-based light homogenizing plate.
In one embodiment of the present invention, the vertical shimming angle of the shimming element is greater than or equal to the difference between the vertical receiving field angle of the receiving end assembly and the vertical projecting field angle of the projecting end assembly.
In an embodiment of the invention, a horizontal dodging angle of the dodging element is greater than or equal to a difference between a horizontal receiving field angle of the receiving end assembly and a horizontal projecting field angle of the projecting end assembly.
In an embodiment of the invention, the horizontal dodging angle and/or the vertical dodging angle of the dodging element is larger than 60 °.
In an embodiment of the present invention, a cross-sectional dimension of the light unifying element is larger than a cross-sectional dimension of an optical component of the projection end assembly, and a lower surface of the light unifying element is spaced apart from an upper surface of the optical component by a predetermined distance.
In an embodiment of the present invention, the step of reflecting the diffused light beam to a receiving end assembly of the TOF module to be received by the receiving end assembly to acquire at least one TOF image includes the steps of:
configuring a target assembly in a field-of-view region overlapped between a projection end field of view and a receiving end field of view of the TOF module; and
the spread light beam is reflected by the target assembly to be received by the receiving end assembly to obtain the at least one TOF image.
In an embodiment of the present invention, the step of reflecting the diffused light beam to a receiving end assembly of the TOF module to be received by the receiving end assembly to acquire at least one TOF image further includes the steps of:
selectively adjusting the position of the target assembly, so that after the position of the target assembly is adjusted each time, the reflected light beam is received by the receiving end assembly to obtain a TOF image of the corresponding position.
According to another aspect of the present application, there is further provided a calibration system for a TOF module, wherein the TOF module includes a projecting end assembly and a receiving end assembly, wherein the calibration system for the TOF module includes:
the diffusion module is used for diffusing the output light beam projected by the projecting end component of the TOF module so as to form a diffused light beam with a variable emission angle, so that the field angle of the projecting end of the TOF module is increased;
the reflecting module is used for reflecting the diffused light beam to a receiving end assembly of the TOF module so as to be received by the receiving end assembly to acquire at least one TOF image; and
and the calibration module is used for calibrating the internal parameters and the external parameters of the TOF module based on the at least one TOF image.
In an embodiment of the invention, the diffusing module includes an adding module and a light homogenizing element, wherein the adding module is configured to add the light homogenizing element to a field of view of the projection end assembly of the TOF module, so as to diffuse the output light beam projected by the projection end assembly through the light homogenizing element, so as to increase a divergence angle of the output light beam.
In an embodiment of the invention, the reflection module includes a configuration module and a target assembly, wherein the configuration module is configured to configure a field of view region of the target assembly overlapping between a projection end field of view and a receiving end field of view of the TOF module, so as to reflect the diffused light beam through the target assembly to be received by the receiving end assembly to obtain the at least one TOF image.
In an embodiment of the invention, the reflection module further includes a positioning module, wherein the positioning module is configured to selectively adjust the position of the target assembly, so that after each adjustment of the position of the target assembly, the receiving end assembly receives the reflected light beam to obtain a TOF image of the corresponding position.
Further objects and advantages of the invention will be fully apparent from the ensuing description and drawings.
These and other objects, features and advantages of the present invention will become more fully apparent from the following detailed description, the accompanying drawings and the claims.
Drawings
Fig. 1 is a schematic diagram of a TOF module according to an embodiment of the present application.
Fig. 2 shows a schematic diagram of calibration of the TOF module by using a conventional calibration method.
Fig. 3A shows a schematic diagram of light intensity distribution on a receiving end chip of the TOF module when the conventional calibration method is adopted.
Fig. 3B shows a schematic diagram of the distribution of the fixed phase noise on the receiving end chip of the TOF module when the existing calibration method is adopted.
FIG. 4 is a flowchart illustrating a calibration method of a TOF module according to an embodiment of the present disclosure.
Fig. 5 is a schematic flow chart illustrating a diffusion step in the calibration method of the TOF module according to the embodiment of the application.
Fig. 6 shows a schematic diagram of the calibration method of the TOF module according to the present application.
Fig. 7 shows a schematic structural diagram of the TOF module when the calibration method of the TOF module of the present application is adopted.
Fig. 8A shows a schematic diagram of light intensity distribution on a receiving end chip of the TOF module when the calibration method of the TOF module of the present application is adopted.
Fig. 8B shows a schematic diagram of distribution of fixed phase noise on a receiving end chip of the TOF module when the calibration method of the TOF module of the present application is used.
Fig. 9 is a schematic flow chart illustrating a reflection step in the calibration method of the TOF module according to the above embodiment of the present application.
FIG. 10 is a block diagram illustrating a calibration system for a TOF module according to an embodiment of the present disclosure.
Detailed Description
The following description is presented to disclose the invention so as to enable any person skilled in the art to practice the invention. The preferred embodiments in the following description are given by way of example only, and other obvious variations will occur to those skilled in the art. The basic principles of the invention, as defined in the following description, may be applied to other embodiments, variations, modifications, equivalents, and other technical solutions without departing from the spirit and scope of the invention.
It will be understood by those skilled in the art that in the present disclosure, the terms "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate orientations or positional relationships that are based on those shown in the drawings, which are merely for convenience in describing the present disclosure and to simplify the description, and do not indicate or imply that the device or element so referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus the terms above should not be construed as limiting the present disclosure.
In the present invention, the terms "a" and "an" in the claims and the description should be understood as meaning "one or more", that is, one element may be one in number in one embodiment, and the element may be more than one in number in another embodiment. The terms "a" and "an" should not be construed as limiting the number unless the number of such elements is explicitly recited as one in the present disclosure, but rather the terms "a" and "an" should not be construed as being limited to only one of the number.
Module calibration generally refers to establishing a module geometric imaging model describing the correspondence between a scene point in a world coordinate system (i.e., a space coordinate system) and its image point on an image plane. In other words, module calibration is essentially a process of determining the intrinsic and extrinsic parameters of the module, wherein the intrinsic parameters of the module are parameters that are intrinsic to the module and are independent of position information, typically including focal length, lens distortion, image center point, etc.; and the extrinsic parameters of the module are the relationship between the three-dimensional position and orientation of the module coordinate system relative to a world coordinate system. The accurate solution of the parameters can not only improve the accuracy of three-dimensional information recovery, but also lay a good foundation for subsequent stereo image matching and three-dimensional reconstruction. Therefore, in order to ensure the normal use of the TOF module and improve the use accuracy of the TOF module, the TOF module needs to be calibrated accurately, that is, the TOF module needs to be calibrated to obtain the internal parameters and the external parameters of the TOF module. However, for the TOF module installed on a sweeping robot or other equipment, the field angle of the projecting end of the TOF module is often smaller than that of the receiving end, even far smaller than that of the receiving end, so that a dark angle appears on the receiving end chip of the TOF module, even most areas cannot receive sufficient light intensity information, and therefore the calibration accuracy of the TOF module is seriously reduced, even the TOF module cannot be calibrated.
For example, fig. 1 and 2 show a TOF module applied to a sweeping robot, which is capable of projecting a line-shaped light beam. Specifically, as shown in fig. 1 and 2, the TOF module 10 generally includes a projecting end module 11 and a receiving end module 12, wherein the projecting end module 11 is configured to project a light beam with a predetermined wavelength to a target under test, and the receiving end module 12 is configured to receive and process the light beam reflected by the target under test to obtain depth information and a gray scale image (i.e., TOF image) of the target under test.
It is noted that, as shown in fig. 2, during the calibration of the TOF module 10, the target under test is implemented as a target assembly 20, so that the TOF module 10 is calibrated by the target assembly 20. It is to be understood that the beam emitted (emitted) by the projecting end assembly 11 of the TOF module 10 of the present invention can be an infrared laser. Preferably, the projecting end assembly 11 is implemented as a vertical cavity surface laser emitter (VCSEL for short).
However, as shown in FIG. 2, the vertical projection field angle V of the projection end assembly 11 of the TOF module 101Typically between 5 and 10 deg. to allow said projectionThe end-assembly 11 is capable of projecting a line-shaped light beam, and the vertical receiving field angle V of the receiving end-assembly 12 of the TOF module 102Between 45 ° and 55 °, dark-side and dark-corner phenomena will occur on the receiving-end chip of the receiving-end subassembly 12, so that most of the area on the receiving-end chip of the receiving-end subassembly 12 will not receive sufficient light intensity information (such as the light intensity distribution diagram shown in fig. 3A), and the fixed phase noise precision of the receiving-end chip of the receiving-end subassembly 12 is low (such as the fixed phase noise distribution diagram shown in fig. 3B).
Thus, when the TOF module 10 is calibrated, the conventional TOF module calibration method cannot accurately calibrate the dark edge or dark corner area on the receiving end chip of the receiving end assembly 12, or even cannot calibrate the dark edge or dark corner area on the receiving end chip at all. However, when the TOF module 10 is used, the projected light beam is often reflected to a dark edge or dark corner area on the receiving end chip of the receiving end assembly 12 due to environmental factors such as the surface roughness of the target to be measured. At this time, if the dark edge or the dark corner area on the receiving end chip is not precisely calibrated, the imaging quality of the TOF module 10 will be seriously affected, so in order to solve the problem, the present application provides a calibration method and a calibration system for a TOF module, which can improve the calibration precision for the TOF module with the field angle of the projection end smaller than that of the receiving end.
Schematic process
Referring to fig. 4-9 of the drawings, a method of calibrating a TOF module is shown in accordance with an embodiment of the invention. Specifically, as shown in fig. 4, the calibration method of the TOF module may include the following steps:
s100: diffusing an output light beam projected through a projecting end component of a TOF module to form a diffused light beam with a widened divergence angle, so that a field angle of a projecting end of the TOF module is widened;
s200: reflecting the diffused light beam to a receiving end assembly of the TOF module so as to be received by the receiving end assembly to acquire at least one TOF image; and
s300: and calibrating the internal parameters and the external parameters of the TOF module based on the at least one TOF image.
It should be noted that, in the calibration method of the TOF module according to the present application, when calibrating the TOF module, the output light beam projected by the projecting end component of the TOF module is firstly diffused to increase the angle of view of the projecting end of the TOF module (for convenience of description and understanding, the increased angle of view of the projecting end is defined as the diffused angle of view of the projecting end component), so that the diffused angle of view of the projecting end component can correspondingly cover the dark edge and/or dark corner area on the receiving end chip in the receiving end component of the TOF module, and therefore the diffused light beam can be reflected to the dark edge and/or dark corner area on the receiving end chip in the receiving end component of the TOF module to be received, so that the dark edge and/or dark corner area on the receiving end chip in the receiving end component can obtain sufficient light intensity information, so as to improve the calibration precision of the TOF module by the calibration method of the TOF module.
More specifically, according to the above embodiment of the present application, as shown in fig. 5, the step S100 of the calibration method of the TOF module may include the steps of:
s110: adding a dodging element to the field of view of the projecting end assembly of the TOF module; and
s120: the output light beam projected through the projection end assembly is diffused by the dodging element to increase a divergence angle of the output light beam.
Exemplarily, in the step S100 of the calibration method of the TOF module: as shown in fig. 6 and 7, the dodging element 30 may be added to the field of view of the projecting end assembly 11 of the TOF module 10, wherein the dodging element 30 is configured to diffuse the output light beam 101 projected by the projecting end assembly 11 to form a diffused light beam 102 with an enlarged divergence angle, so that the original field angle of the projecting end of the TOF module 10 is enlarged.
It should be noted that, in an example of the present application, as shown in fig. 6, in the step S120 of the calibration method of the TOF module, the dodging element 30 may one-dimensionally diffuse the output light beam 101 projected by the projecting end assembly 11 to form the diffused light beam 102 with an enlarged vertical divergence angle, so that the vertical projection field angle of the projecting end assembly 11 is enlarged to serve as the vertical diffusion field angle of the projecting end assembly 11, so as to reflect the diffused light beam to the dark edge and/or dark corner area on the receiving end chip in the receiving end assembly 12 of the TOF module 10 for being received, so that the dark edge and/or dark corner area on the receiving end chip in the receiving end assembly 12 can obtain sufficient light intensity information, thereby improving the calibration accuracy of the calibration method of the TOF module.
Of course, in other examples of the present application, the dodging element 30 may also two-dimensionally diffuse the output light beam 101 projected by the projecting end assembly 11 to form the diffused light beam 102 with the horizontal divergence angle and the vertical divergence angle both being increased, so that the horizontal projection angle of view and the vertical projection angle of view of the projecting end assembly 11 are both increased, so as to reflect the diffused light beam 102 to a majority of dark-edge and/or dark-angle areas on a receiving end chip in the receiving end assembly 12 of the TOF module 10 for being received, so that a majority of dark-edge and/or dark-angle areas on a receiving end chip in the receiving end assembly 12 can obtain sufficient light intensity information, thereby improving the calibration accuracy of the calibration method of the TOF module.
Preferably, the vertical dodging angle of the dodging element 30 is greater than or equal to the difference between the vertical receiving field angle of the receiving end assembly 12 and the vertical projecting field angle of the projecting end assembly 11, that is, the vertical spreading field angle of the projecting end assembly 11 is greater than or equal to the vertical receiving field angle of the receiving end assembly 12.
More preferably, the horizontal dodging angle of the dodging element 30 is also greater than or equal to the difference between the horizontal receiving field angle of the receiving end assembly 12 and the horizontal projecting field angle of the projecting end assembly 11, that is, the horizontal spreading field angle of the projecting end assembly 11 is also greater than or equal to the horizontal receiving field angle of the receiving end assembly 12. It is understood that the horizontal or vertical dodging angle of the dodging element 30 of the present application is respectively equal to the difference between the horizontal or vertical divergent angle of view of the projection end assembly 11 and the horizontal or vertical projection angle of view of the projection end assembly 11; in other words, the horizontal or vertical dodging angle of the dodging element 30 is correspondingly equal to the difference between the horizontal or vertical divergence angle of the diffused light beam 102 and the horizontal or vertical divergence angle of the output light beam 101, respectively.
Illustratively, as shown in FIG. 6, the vertical divergent field angle V of the projecting end assembly 11 of the TOF module 101' enlarged and larger than a vertical receiving field angle V of the receiving end assembly 12 of the TOF module 102Therefore, the dark-edge and dark-corner phenomena will not occur on the receiving-end chip of the receiving-end assembly 12, so that all areas on the receiving-end chip of the receiving-end assembly 12 will receive sufficient light intensity information (such as the light intensity distribution diagram shown in fig. 8A), and the precision of the fixed phase noise of the receiving-end chip of the receiving-end assembly 12 also becomes high (such as the fixed phase noise distribution diagram shown in fig. 8B), so that the calibration method of the TOF module calibrates all dark-edge and dark-edge areas on the receiving-end chip of the TOF module, which is beneficial to improving the calibration precision of the TOF module.
Preferably, the dodging element 30 has a horizontal and/or vertical dodging angle greater than 60 ° to meet the calibration requirements of most TOF modules.
According to the above-mentioned embodiments of the present application, the light uniformizing element 30 of the present application may be, but is not limited to be, implemented as a Diffuser (Diffuser) which can function as a light scattering effect, so that the light is scattered more uniformly. In other words, in the step S120 of the calibration method of the TOF module: scattering, by a diffuser, the light beam projected via the projection end assembly to increase a projection end field angle of the TOF module.
Of course, in other examples of the present application, the dodging element 30 may also be implemented as an optical device such as a diffractive optical element or a refraction-based dodging plate, etc., as long as the output light beam 101 projected via the projection end assembly 11 of the TOF module 10 can be diffused such that the angle of field of the projection end of the TOF module 10 is enlarged. In other words, in the step S120 of the calibration method of the TOF module: diffracting, by a diffractive optical element, the light beam projected via the projection end assembly to increase a projection end field angle of the TOF module; or the light beam projected by the projection end component is refracted through the refraction-based dodging plate so as to increase the field angle of the projection end of the TOF module.
It is noted that, as shown in fig. 7, the projecting end component 11 of the TOF module 10 generally includes a light source module 111 and an optical component 112, wherein the optical component 112 is disposed on a light emitting side of the light source module 111, wherein the light source module 111 is used for emitting an input light beam 103 to the optical component 112, and the optical component 112 is used for modulating the input light beam 103 into the output light beam 101 to form a light field (e.g., a linear light field) required by a specific scene. Since the optical component 112 of the projecting end assembly 11 is also typically implemented as a diffuiser, such that the divergence angle of the output light beam 101 will be greater than the divergence angle of the input light beam 103, the output light field 101 projected by the projecting end assembly 11 of the TOF module 10 is also divergent. At this time, if the position where the dodging element 30 is added is far from the optical component 112 of the projection end assembly 11, or the size of the dodging element 30 is small, a portion of the output light beam 101 modulated by the optical component 112 bypasses the dodging element 30 and is not diffused by the dodging element 30, which not only causes the scattered light beam 102 and a portion of the output light beam 101 to be stacked to cause uneven light field intensity distribution, but also seriously affects the imaging quality of the TOF module 10, so that the light beam in the area where the scattered light beam 102 and a portion of the output light beam 101 are stacked cannot be utilized due to the fact that the flight time cannot be accurately calculated, thereby greatly reducing the utilization rate of light energy.
In order to avoid the above problem, in step S110 of the calibration method of the TOF module of the present application: the cross-sectional dimension of the dodging element is larger than that of an optical component of the projection end assembly, and a predetermined distance is reserved between the lower surface of the dodging element and the upper surface of the optical component of the projection end assembly so as to ensure that the output light beam modulated by the optical component completely passes through the dodging element and is further diffused into the diffused light beam by the dodging element.
Preferably, the predetermined distance is implemented to be less than 2mm, that is, the distance between the lower surface of the dodging element and the upper surface of the optical component of the projection end assembly is less than 2 mm.
It should be noted that, according to the above embodiment of the present application, as shown in fig. 9, the step S200 of the calibration method of the TOF module may include the steps of:
s210: configuring a target assembly in a field-of-view region overlapped between a projection end field of view and a receiving end field of view of the TOF module; and
s220: the diffused light beam is reflected by the target assembly to be received by the receiving end assembly to obtain the at least one TOF image.
Notably, because the reticle assembly 20 is located within a common field of view region of the projecting end assembly 11 and the receiving end assembly 12 of the TOF module 10, when the TOF module 10 photographs, first, the projecting end assembly 11 of the TOF module 10 is disposed to project the output light beam toward the reticle assembly 20; then, the dodging element 30 diffuses the output light beam to form the diffused light beam; the diffused beam then propagates to the calibration face of the reticle assembly 20 to be reflected back; finally, the receiving end assembly 12 of the TOF module 10 receives the reflected light beam to acquire the depth image and the grayscale image of the target assembly 20, that is, the TOF module 10 captures the TOF image obtained by the target assembly 20.
In addition, the target assembly 20 may be, but is not limited to being, implemented as a diffuse reflector for diffusely reflecting the diffused light beam to improve the calibration of the TOF module 10 by the TOF module calibration method of the present application.
In particular, as shown in fig. 9, the step S200 of the calibration method of the TOF module may further include the steps of:
s230: selectively adjusting the position of the target assembly, so that after the position of the target assembly is adjusted each time, the reflected light beam is received by the receiving end assembly to obtain a TOF image of the corresponding position. Therefore, the TOF module is calibrated subsequently according to TOF images at different positions so as to obtain internal parameters and external parameters of the TOF module, and further improvement of calibration accuracy of the TOF module 10 is facilitated.
It should be noted that, after the TOF module 10 obtains the TOF image, the step S300 of the calibration method of the TOF module of the present application may process the TOF image by an existing calibration method to calibrate the internal reference and the external reference of the TOF module 10. For example, the step S300 of the calibration method of the TOF module may include the following steps:
establishing a world coordinate system, a TOF module coordinate system, a TOF image plane coordinate system and a TOF pixel coordinate system;
extracting TOF pixel coordinates of at least four nonlinear characteristic points on each TOF image, and acquiring world coordinates of the at least four characteristic points; and
and solving a homography matrix based on the TOF pixel coordinate and the world coordinate, and solving an initial internal parameter and an initial external parameter of the TOF module according to the homography matrix.
Further, the step S300 may further include the steps of:
solving TOF distortion parameters of the TOF module by a distortion correction model and a data fitting objective function of the TOF module; and
and optimizing the initial internal parameters and the initial external parameters according to a maximum likelihood estimation method to obtain the internal and external parameters of the TOF module.
Next, after obtaining the internal and external parameters of the TOF module, the ideal ray distance of each pixel in the receiving end chip of the TOF module can be calculated according to the known distance of the reticle assembly.
It should be noted that, although the above embodiments and the accompanying drawings illustrate a linear TOF module as an example to clarify the advantages and the objects of the present application, the type of the TOF module is not limited thereto, as long as the viewing angle of the TOF module at the projection end is smaller than that of the receiving end, and the description of the present application is omitted.
Illustrative System
According to another aspect of the present invention, in order to better implement the calibration method for calibrating the TOF module easily, the present invention further provides a calibration system for a TOF module 10 according to the calibration method for the TOF module, wherein the TOF module 10 includes a projecting end assembly 11 and a receiving end assembly 12. According to an embodiment of the present invention, as shown in fig. 10, the calibration system 40 of the TOF module may include a diffusing module 41, a reflecting module 42 and a calibrating module 43, wherein the diffusing module 41 is configured to diffuse the output light beam projected by the projecting end component of the TOF module to form a diffused light beam with an enlarged emitting angle, so that the field angle of the projecting end of the TOF module is enlarged; the reflection module 42 is configured to reflect the diffused light beam to a receiving end assembly of the TOF module, so that the receiving end assembly receives the diffused light beam to acquire at least one TOF image; the calibration module 43 is configured to calibrate the internal parameter and the external parameter of the TOF module based on the at least one TOF image.
It is noted that, in an example of the present application, as shown in fig. 10, the diffusing module 41 may include an adding module 411 and a dodging element 412, wherein the adding module 411 is configured to add the dodging element 412 to the field of view of the projection end assembly of the TOF module, so as to diffuse the output light beam projected by the projection end assembly through the dodging element 412, so as to increase the divergence angle of the output light beam.
In an example of the present application, as shown in fig. 10, the reflection module 42 may include a configuration module 421 and a target assembly 422, wherein the configuration module 421 is configured to configure a field of view region of the target assembly 422 overlapping between a projection end field of view and a receiving end field of view of the TOF module, so as to reflect the diffused light beam through the target assembly 422 to be received by the receiving end assembly to obtain the at least one TOF image.
Preferably, as shown in fig. 10, the reflection module 42 further includes a positioning module 423, wherein the positioning module 423 is configured to selectively adjust the position of the target assembly 422, so that after each adjustment of the position of the target assembly 422, the reflected light beam is received by the receiving end assembly to obtain a TOF image of the corresponding position.
It will be appreciated by persons skilled in the art that the embodiments of the invention described above and shown in the drawings are given by way of example only and are not limiting of the invention. The objects of the invention have been fully and effectively accomplished. The functional and structural principles of the present invention have been shown and described in the examples, and any variations or modifications of the embodiments of the present invention may be made without departing from the principles.

Claims (15)

  1. The calibration method of the TOF module is characterized by comprising the following steps:
    diffusing the output light beam projected by the projecting end component of the TOF module to form a diffused light beam with an enlarged emission angle, so that the field angle of the projecting end of the TOF module is enlarged;
    reflecting the diffused light beam to a receiving end assembly of the TOF module so as to be received by the receiving end assembly to acquire at least one TOF image; and
    and calibrating the internal parameter and the external parameter of the TOF module based on the at least one TOF image.
  2. 2. The method for calibrating a TOF module of claim 1, wherein the step of diffusing the output beam projected through a projection end assembly of the TOF module to form a diffused beam with an increased emission angle such that the field angle of the projection end of the TOF module is increased comprises the steps of:
    adding a dodging element to the field of view of the projecting end assembly of the TOF module; and
    the output light beam projected through the projection end assembly is diffused by the dodging element to increase a divergence angle of the output light beam.
  3. 3. The method for calibrating a TOF module of claim 2, wherein in the step of diffusing, by the dodging element, the output beam projected through the projection end assembly to increase the divergence angle of the output beam:
    one-dimensionally diffusing the output beam projected through the projection end assembly to form the diffused beam with an increased vertical divergence angle.
  4. 4. The method for calibrating a TOF module of claim 2, wherein, in the step of diffusing, by the dodging element, the output beam projected through the projection end assembly to increase the divergence angle of the output beam:
    two-dimensionally diffusing an output beam projected through the projection end assembly to form the diffused beam with an increased horizontal and vertical divergence angles.
  5. 5. A method of calibrating a TOF module according to any one of claims 2 to 4 wherein the dodging element is selected from one of a diffuser, a diffractive optical element and a refraction-based dodging plate.
  6. 6. A method of calibrating a TOF module according to any one of claims 2 to 4 wherein a vertical dodging angle of the dodging element is greater than or equal to a difference between a vertical receiving field angle of the receiving end assembly and a vertical projecting field angle of the projecting end assembly.
  7. 7. The method of calibrating a TOF module of claim 6, wherein a horizontal dodging angle of the dodging element is greater than or equal to a difference between a horizontal receiving field angle of the receiving end assembly and a horizontal projecting field angle of the projecting end assembly.
  8. 8. The method for calibrating a TOF module according to claim 7 wherein the dodging element has a horizontal dodging angle and/or a vertical dodging angle greater than 60 °.
  9. 9. The method of calibrating a TOF module of claim 8, wherein the cross-sectional dimension of the dodging element is larger than the cross-sectional dimension of the optical component of the projection end assembly, and the lower surface of the dodging element is spaced a predetermined distance from the upper surface of the optical component.
  10. 10. The method for calibrating a TOF module according to any one of claims 1 to 4, wherein the step of reflecting the diffused light beam to a receiving end assembly of the TOF module for being received by the receiving end assembly to acquire at least one TOF image comprises the steps of:
    configuring a target assembly in a field-of-view region overlapped between a projection end field of view and a receiving end field of view of the TOF module; and
    the spread light beam is reflected by the target assembly to be received by the receiving end assembly to obtain the at least one TOF image.
  11. 11. The method for calibrating a TOF module of claim 10, wherein the step of reflecting the diffused beam of light to a receiving end assembly of the TOF module for being received by the receiving end assembly to acquire at least one TOF image further comprises the steps of:
    selectively adjusting the position of the target assembly, so that after the position of the target assembly is adjusted each time, the reflected light beam is received by the receiving end assembly to obtain a TOF image of the corresponding position.
  12. A calibration system for a TOF module, wherein the TOF module includes a projecting end assembly and a receiving end assembly, wherein the calibration system for the TOF module includes:
    the diffusion module is used for diffusing the output light beam projected by the projecting end component of the TOF module so as to form a diffused light beam with a variable emission angle, so that the field angle of the projecting end of the TOF module is increased;
    the reflecting module is used for reflecting the diffused light beam to a receiving end assembly of the TOF module so as to be received by the receiving end assembly to acquire at least one TOF image; and
    and the calibration module is used for calibrating the internal parameter and the external parameter of the TOF module based on the TOF image.
  13. 13. The system for calibrating a TOF module of claim 12, wherein the diffusing module comprises an adding module and a dodging element, wherein the adding module is configured to add the dodging element to a field of view of the projection end assembly of the TOF module, so as to diffuse the output beam projected through the projection end assembly by the dodging element to increase a divergence angle of the output beam.
  14. 14. A calibration system for a TOF module according to claim 12 or 13, wherein said reflection module comprises a configuration module and a reticle assembly, wherein said configuration module is configured to configure the reticle assembly to overlap a field of view region between a projection end field of view and a receiving end field of view of the TOF module, so as to reflect the diffused beam through the reticle assembly to be received by the receiving end assembly to obtain the at least one TOF image.
  15. 15. The system for calibrating a TOF module according to claim 14, wherein the reflection module further comprises a positioning module, wherein the positioning module is configured to selectively adjust the position of the reticle assembly, so that after each adjustment of the position of the reticle assembly, the reflected light beam is received by the receiving end assembly to obtain the TOF image of the corresponding position.
CN202011533547.XA 2020-12-22 2020-12-22 Calibration method and system of TOF module Pending CN114660576A (en)

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Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202011533547.XA CN114660576A (en) 2020-12-22 2020-12-22 Calibration method and system of TOF module

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Publication Number Publication Date
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