Calibration device and depth camera calibration method

Abstract

A calibration device includes a base, a column and a crossbar. The column is connected to the base and extends along a first direction, and the crossbar is connected to the column. The crossbar includes a base and a carrier. The base is fixed to the column, and the carrier is rotatably connected to the base around a second direction, and the second direction is perpendicular to the first direction. The carrier includes a distance measuring part and a calibration platform, and the calibration platform is used to fix a depth camera. A third direction is defined to be perpendicular to the first direction and the second direction, and the carrier is used to rotate around the second direction to drive the light-emitting axis of the depth camera to rotate within a first calibration plane defined by the first direction and the third direction. The calibration device provided by the present invention is conducive to determining and compensating the positional relationship between the light-emitting axis of the depth camera and the calibration surface, thereby improving the calibration accuracy of the depth camera. In addition, the present invention also provides a calibration method for a depth camera.

Description

Technical Field

[0001] The present invention relates to a calibration device and a calibration method for a depth camera. Background Art

[0002] As one of the mainstream 3D imaging technologies today, Time of Flight (TOF) technology has achieved rapid development in recent years, especially in achieving major breakthroughs in 3D face recognition, scene recognition, and three-dimensional perception on mobile devices, and has recently attracted much attention.

[0003] A TOF depth camera primarily consists of a transmitter and a receiver. The transmitter emits high-frequency modulated near-infrared light. After the infrared light is reflected by the surface of an object, the receiver receives the reflected light and calculates depth information based on the phase or time difference between the transmitted and received light. However, due to its own characteristics, imaging conditions, and interference from the external environment, the data obtained by the depth camera may contain errors, so the depth camera needs to be calibrated.

[0004] In the existing technology, during calibration, it is necessary to place the depth camera in front of a calibration surface (such as a wall), control the depth camera to emit and receive light, and calculate the depth between the depth camera and the calibration surface; at the same time, use a distance sensor to sense the distance between the depth camera and the calibration surface, and then calibrate the depth camera based on the difference between the calculated depth and the sensed distance. This process requires that the light output axis of the depth camera is perpendicular to the calibration surface. However, during actual calibration, the accuracy of the depth camera calibration is low due to factors such as the tilt of the calibration surface itself or the unequal placement of the calibration equipment. Summary of the Invention

[0005] In view of this, it is necessary to provide a calibration device that can improve the calibration accuracy of a depth camera.

[0006] In addition, it is necessary to provide a depth camera calibration method.

[0007] A calibration device includes a base, a column and a crossbar, wherein the column is connected to the base and extends along a first direction, and the crossbar is connected to the column.

[0008] The crossbar includes a base and a carrier. The base is fixed to the column, and the carrier is rotatably connected to the base about a second direction, wherein the second direction is perpendicular to the first direction. The carrier includes a rangefinder and a calibration platform, and the calibration platform is used to fix a depth camera. A third direction is defined as perpendicular to the first and second directions, and the carrier is used to rotate about the second direction to drive the light output axis of the depth camera to rotate within a first calibration plane defined by the first and third directions.

[0009] Furthermore, the column is rotatably connected to the base around the first direction, and the column is used to rotate around the first direction to drive the light-emitting axis of the depth camera to rotate within a second calibration plane defined by the second direction and the third direction.

[0010] Furthermore, the base includes a base body and a first driver, the column is connected to the first driver, and the first driver is used to drive the column to rotate around the first direction.

[0011] Furthermore, the crossbar further includes a second driver, and the second driver is used to drive the distance measuring element and / or the calibration platform to rotate around the second direction.

[0012] Furthermore, the base includes a first bottom plate and two first side plates arranged on one side of the bottom plate. The bottom plate and the two first side plates together form a accommodating space. The carrier can be rotatably accommodated in the accommodating space, and the second drive is fixed to the side of the first side plate away from the accommodating space.

[0013] Furthermore, the carrier further includes a rotating seat, the distance measuring component and the calibration platform are fixed on the rotating seat, and the rotating seat is rotatably accommodated in the accommodating space around the second direction.

[0014] The rotating seat includes a second base plate and a second side plate and a third side plate arranged on the second base plate. The distance measuring member and the calibration platform are connected to the third side plate and the distance measuring member is located between the calibration platform and the second side plate. The second side plate protrudes toward the second driver to form a first rotating shaft. The first rotating shaft is transmission-connected to the second driver. The calibration platform protrudes on a side away from the distance measuring member to form a second rotating shaft. The second rotating shaft and the first rotating shaft extend along the second direction.

[0015] Furthermore, the calibration platform is detachably connected to the third side plate.

[0016] Furthermore, the base body is made of rubber.

[0017] A depth camera calibration method comprises the following steps:

[0018] A calibration apparatus as described above is provided.

[0019] A depth camera is fixed on the calibration platform of the calibration device so that the light-emitting axis of the depth camera faces a calibration surface.

[0020] When the distance measuring component and the calibration platform are located at a first position, the distance measuring component senses a first distance between the depth camera and the calibration surface.

[0021] The distance measuring component and the calibration platform rotate around the second direction by a first predetermined angle to a second position, and the distance measuring component senses a second distance between the depth camera and the calibration surface.

[0022] A first deflection angle between the calibration surface and the first direction is calculated according to the first predetermined angle, the first distance, and the second distance.

[0023] A first compensation angle is calculated based on the first deflection angle and the first predetermined angle, and the distance measuring component and the calibration platform are rotated from the second position to a third position around the second direction by the first compensation angle, so that the optical axis is perpendicular to the calibration surface on the first calibration surface.

[0024] Furthermore, the method further comprises the steps of:

[0025] When the distance measuring component and the calibration platform are located at a fourth position, the distance measuring component senses a third distance between the depth camera and the calibration surface.

[0026] The column rotates around the first direction by a second predetermined angle until the depth camera reaches a fifth position, and the ranging component senses a fourth distance between the depth camera and the calibration surface at the fifth position.

[0027] A second deflection angle between the calibration surface and the second direction is calculated according to the second predetermined angle, the third distance, and the fourth distance.

[0028] A second compensation angle is calculated based on the second deflection angle and the second predetermined angle, and starting from the fifth position, the column is rotated around the first direction by the second compensation angle until the depth camera reaches a sixth position, so that the light-emitting axis of the depth camera is perpendicular to the calibration surface on the second calibration surface.

[0029] The calibration device provided by the present invention drives the light-emitting axis of the depth camera to rotate within the first calibration plane by rotating the carrier around the second direction, and drives the light-emitting main axis of the depth camera to rotate within the second calibration plane by rotating the column around the first direction, thereby making the light-emitting axis of the depth camera perpendicular to the calibration plane, thereby improving the calibration accuracy of the depth camera. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 An overall schematic diagram of a calibration device provided in one embodiment of the present invention.

[0031] Figure 2 for Figure 1 A magnified view of a portion of the calibration equipment shown.

[0032] Figure 3 for Figure 1 The diagram shows a schematic diagram of the calibration principle of the calibration device within the first calibration plane.

[0033] Figure 4 for Figure 1 Schematic diagram of the calibration principle of the calibration device in the second calibration plane.

[0034] Description of main component symbols

[0035] Calibration device 100 Calibration surface α

[0036] Base 10 First calibration surface E

[0037] Base body 11 Second calibration surface F

[0038] Column 20 Optical axis A

[0039] Crossbar 30 first position M

[0040] Base 31 Second position N

[0041] Accommodating space 311 third position S

[0042] First bottom plate 312 fourth position G

[0043] First side plate 313 fifth position H

[0044] Vehicle 32 Sixth Position I

[0045] Distance measuring element 321 first preset angle β

[0046] Calibration platform 322 second preset angle δ

[0047] Second rotation axis 3221 first deflection angle γ

[0048] Rotating seat 33 second deflection angle θ

[0049] Second base plate 331 first compensation angle λ

[0050] Second side plate 332 second compensation angle λ

[0051] First rotation axis 3321 First distance L1

[0052] The third side plate 333 has a second distance L2

[0053] Second driver 35 Third distance L3

[0054] First direction O Fourth distance L4

[0055] Second direction P Intersection line X

[0056] Third direction Q Depth camera 200

[0057] The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0058] In order to more clearly understand the above-mentioned objectives, features and advantages of the embodiments of the present invention, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the features in the embodiments of the present invention can be combined with each other without conflict.

[0059] The following description sets forth many specific details to facilitate a full understanding of the embodiments of the present invention. The embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are considered to fall within the scope of the embodiments of the present invention.

[0060] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art in the art of the embodiments of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the embodiments of the present invention.

[0061] Please also see Figure 1 、 Figure 2 and Figure 3 An embodiment of the present invention provides a calibration device 100 for calibrating a depth camera 200. The calibration device 100 includes a base 10, a column 20, and a crossbar 30. The column 20 is connected to the base 10 and extends along a first direction O. The crossbar 30 is connected to the column 20 and is used to connect a depth camera 200.

[0062] The crossbar 30 includes a base 31 and a carrier 32. The base 31 is fixed to the column 20. The carrier 32 is rotatably connected to the base 31 about a second direction P, and the second direction P is perpendicular to the first direction O. The carrier 32 includes a distance measuring component 321 and a calibration platform 322, and the calibration platform 322 is used to fix the depth camera 200. A third direction Q is defined as being perpendicular to the first direction O and the second direction P. The carrier 32 rotates about the second direction P to drive the light output axis A of the depth camera 200 to rotate within a first calibration plane E defined by the first direction O and the third direction Q. The distance measuring component 321 is used to measure the distance between the depth camera 200 and a calibration surface α.

[0063] When using, please refer to Figure 3 The depth camera 200 is fixed to the calibration device 100, with the optical axis A of the depth camera 200 oriented toward a calibration surface α. By arranging the distance measuring member 321 and the calibration platform 322 to rotate about the second direction P, the direction of the optical axis A of the depth camera 200 can be adjusted within the first calibration surface E, thereby adjusting the relative position between the optical axis A and the calibration surface α. The specific calibration method will be discussed in detail below.

[0064] In this embodiment, the column 20 is rotatably connected to the base 10 about the first direction O. The base 10 includes a base body 11 and a first actuator (not shown). The column 20 is movably connected to the base body 11, and the drive shaft of the first actuator is in driving connection with the column 20. The column 20 rotates about the first direction O to drive the light output axis A of the depth camera 200 to rotate within the second calibration plane F defined by the second direction P and the third direction Q.

[0065] When using, please refer to Figure 4 The depth camera 200 is fixed to the calibration device 100, with the optical axis A of the depth camera 200 oriented toward a calibration surface α. By arranging the support column 200 to rotate about the first direction O, the direction of the optical axis A of the depth camera 200 can be adjusted within the second calibration surface F. By further adjusting the relative position between the optical axis A and the calibration surface α, the optical axis A can be made perpendicular to the calibration surface α. The specific calibration method will be discussed in detail below.

[0066] In this embodiment, the base body 11 is made of a vibration-proof elastic material, such as rubber, to reduce the influence of factors such as floor vibration on the accuracy of calibration.

[0067] In this embodiment, the crossbar 30 further includes a second driver 35 , and the second driver 35 drives the distance measuring member 321 and / or the calibration platform 322 to rotate around the second direction P.

[0068] In this embodiment, the calibration device 100 further includes a controller (not shown). The controller is electrically connected to the first driver and the second driver 35 . The controller is used to control the rotation of the first driver and the second driver 35 .

[0069] In this embodiment, the controller 40 is a programmable logic controller, the first driver and the second driver 35 are stepper motors, and the positioning accuracy of the stepper motors is 0.05 degrees.

[0070] In this embodiment, the base 31 is generally U-shaped and includes a first bottom plate 312 and two first side plates 313 disposed on either side of the first bottom plate 312. The first bottom plate 312 and the two first side plates 313 together enclose a receiving space 311. The carrier 32 is rotatably received in the receiving space 311 about the second direction P. The second driver 35 is fixed to the side of the first side plate 313 away from the receiving space 311.

[0071] In this embodiment, the carrier 32 further includes a rotating base 33 . The distance measuring member 321 and the calibration platform 322 are fixed on the rotating base 33 . The rotating base 33 is rotatably received in the accommodating space 311 around the second direction P.

[0072] The carrier 32 also includes a rotating base 33, which includes a second base plate 331, a second side plate 332, and a third side plate 333. The second side plate 332 is disposed on one side of the second base plate 331, and the third side plate 333 is disposed on the other side of the second base plate 331. The second side plate 332 and the third side plate 333 are adjacent and face the same side of the second base plate 331. The distance measuring member 321 and the calibration platform 322 are connected to the third side plate 333, with the distance measuring member 321 located between the calibration platform 322 and the second side plate 332. The second side plate 332 protrudes toward the second actuator 35 to form a first rotating shaft 3321, which is in driving connection with the second actuator 35. A second rotating shaft 3221 is protruded from a side of the calibration platform 322 away from the distance measuring member 321 . The second rotating shaft 3221 is coaxial with the first rotating shaft 3321 , and the second rotating shaft 3221 is rotatably connected to the adjacent first side plate 313 .

[0073] In this embodiment, the calibration platform 322 is detachably connected to the third side plate 333 , and by selecting different calibration platforms 322 , the calibration platform 322 can be adapted to different models or sizes of the depth camera 200 .

[0074] Please also see Figure 1 、 Figure 2 and Figure 3 , an embodiment of the present invention provides a calibration method for a depth camera 200, comprising the steps of:

[0075] S1: Provide a depth camera 200, which can be applied to gesture control, 3D modeling, automotive radar, face recognition and other fields.

[0076] S2: Fix the depth camera 200 on the calibration device 100 as described above, and make the light-emitting axis A of the depth camera 200 face a calibration surface α;

[0077] S3: When the depth camera 200 is located at a first position M, the distance measuring component 321 senses a first distance L1 between the depth camera 200 and the calibration surface α;

[0078] S4: Rotate the distance measuring device 321 and the calibration platform 322 clockwise (or counterclockwise) around the second direction P by a first predetermined angle β, so that the depth camera 200 rotates from the first position M to a second position N, and the distance measuring device 321 again senses the second distance L2 between the depth camera 200 and the calibration surface α;

[0079] S5: Calculate a first deflection angle γ between the calibration surface α and the first direction O according to the first preset angle β, the first distance L1, and the second distance L2. The calculation formula is as follows:

[0080]

[0081] S6: Rotate the calibration stage 322 from the second position N around the third direction Q by a first compensation angle λ, so that the depth camera 200 rotates from the second position N to a third position S. At the third position S, the optical axis A of the depth camera 200 is perpendicular to the intersection line X of the first calibration surface E and the calibration surface α. The magnitude of the first compensation angle λ is determined according to the following formula:

[0082] λ=|β-γ|

[0083] If β-γ>0, the calibration platform 322 is rotated counterclockwise (or clockwise) around the second direction P by the first compensation angle λ, so that the depth camera 200 is rotated from the second position N to the third position S;

[0084] If β-γ<0, the calibration stage 322 is rotated clockwise (or counterclockwise) around the second direction P by the first compensation angle λ to the third position S, so that the depth camera 200 is rotated from the second position N to the third position S.

[0085] Please also see Figure 1 、 Figure 2 and Figure 4 In this embodiment, the calibration method further includes the steps of:

[0086] S7: The distance measuring component 321 senses a third distance L3 between the depth camera 200 and the calibration surface α at the fourth position G.

[0087] S8: Rotate the column 20 clockwise (or counterclockwise) around the first direction O by a second preset angle δ until the depth camera 200 reaches a fifth position H, and the distance measuring component 321 again senses a fourth distance L4 between the depth camera 200 and the calibration surface α.

[0088] S9: Calculate the second deflection angle θ between the calibration surface α and the second direction P according to the second preset angle δ, the third distance L3, and the fourth distance L4. The calculation formula is as follows:

[0089]

[0090] S10: Rotate the column 20 about the first direction O by a second compensation angle λ so that the depth camera 200 rotates from the fifth position H to a sixth position I. At the sixth position I, the optical axis A of the depth camera 200 is perpendicular to the calibration surface α. The magnitude of the second compensation angle λ is determined according to the following formula:

[0091] λ=|δ-θ|

[0092] If δ-θ>0, the column 20 is rotated counterclockwise (or clockwise) around the first direction O by the second compensation angle λ, so that the depth camera 200 is rotated from the fifth position H to the sixth position I.

[0093] If δ-θ<0, the pillar 20 is rotated clockwise (or counterclockwise) around the first direction O by the second compensation angle λ, so that the depth camera 200 is rotated from the fifth position H to the sixth position I.

[0094] The above embodiments are only used to illustrate the technical solutions of the embodiments of the present invention and are not intended to limit them. Although the embodiments of the present invention are described in detail with reference to the above preferred embodiments, those skilled in the art should understand that the technical solutions of the embodiments of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A calibration device, characterized in that The invention comprises a base, a column and a crossbar, wherein the column is connected to the base and extends along a first direction, and the crossbar is connected to the column. The crossbar includes a base and a carrier, the base is fixed to the column, the carrier is rotatably connected to the base around a second direction, the second direction is perpendicular to the first direction, the carrier includes a ranging component and a calibration platform, the calibration platform is used to fix a depth camera, and a third direction is defined that is perpendicular to the first direction and the second direction. The carrier is used to rotate around the second direction to drive the light output axis of the depth camera to rotate within a first calibration plane defined by the first direction and the third direction; The column is rotatably connected to the base around the first direction, and the column is used to rotate around the first direction to drive the light-emitting axis of the depth camera to rotate within a second calibration plane defined by the second direction and the third direction. Wherein, when the depth camera is located at a first position, the ranging component is used to sense a first distance between the depth camera and a calibration surface, and when the ranging component and the calibration platform are rotated around the second direction by a first predetermined angle until the depth camera is located at the second position, the ranging component is used to sense a second distance between the depth camera and the calibration surface, the first predetermined angle, the first distance, and the second distance are used to calculate a first deflection angle between the calibration surface and the first direction, the first deflection angle and the first predetermined angle are used to calculate a first compensation angle, the ranging component and the calibration platform are used to rotate the first compensation angle around the second direction so that the depth camera is rotated from the second position to a third position, and when the depth camera is at the third position, the optical axis is perpendicular to the intersection line of the first calibration surface and the calibration surface; When the ranging component and the calibration platform are located at a fourth position, the ranging component is used to sense a third distance between the depth camera and the calibration surface, and the column is used to rotate a second predetermined angle around the first direction, so that when the depth camera is rotated from the fourth position to a fifth position, the ranging component is used to sense a fourth distance between the depth camera and the calibration surface, the second predetermined angle, the third distance and the fourth distance are used to calculate a second deflection angle between the calibration surface and the second direction, the second deflection angle and the second predetermined angle are used to calculate a second compensation angle, the column is used to rotate the second compensation angle around the first direction, so that the depth camera is rotated from the fifth position to a sixth position, and when the depth camera is at the sixth position, the light-emitting axis of the depth camera is perpendicular to the calibration surface.

2. The calibration device according to claim 1, wherein The base includes a base body and a first driver. The column is connected to the first driver. The first driver is used to drive the column to rotate around the first direction.

3. The calibration device according to claim 1, wherein The crossbar further includes a second driver, which is used to drive the distance measuring element and / or the calibration platform to rotate around the second direction.

4. The calibration device according to claim 3, wherein The base includes a first bottom plate and two first side plates arranged on one side of the bottom plate. The bottom plate and the two first side plates together form a accommodating space. The carrier can be rotatably accommodated in the accommodating space, and the second driver is fixed to the side of the first side plate away from the accommodating space.

5. The calibration device according to claim 4, wherein The carrier further includes a rotating seat, the distance measuring member and the calibration platform are fixed on the rotating seat, and the rotating seat is rotatably accommodated in the accommodating space around the second direction; The rotating seat includes a second base plate and a second side plate and a third side plate arranged on the second base plate. The distance measuring member and the calibration platform are connected to the third side plate and the distance measuring member is located between the calibration platform and the second side plate. The second side plate protrudes toward the second driver to form a first rotating shaft. The first rotating shaft is transmission-connected to the second driver. The calibration platform protrudes on a side away from the distance measuring member to form a second rotating shaft. The second rotating shaft and the first rotating shaft extend along the second direction.

6. The calibration device according to claim 5, wherein The calibration platform is detachably connected to the third side plate.

7. The calibration device according to claim 2, wherein The base body is made of rubber.

8. A method for calibrating a depth camera, characterized in that: Including steps: Providing a calibration device according to any one of claims 1 to 7; Fixing a depth camera on the calibration platform of the calibration device so that the light-emitting axis of the depth camera faces a calibration surface; When the depth camera is located at a first position, the distance measuring component senses a first distance between the depth camera and the calibration surface; When the distance measuring component and the calibration platform rotate about the second direction by a first predetermined angle until the depth camera is located at a second position, the distance measuring component senses a second distance between the depth camera and the calibration surface; Calculating a first deflection angle between the calibration surface and the first direction according to the first predetermined angle, the first distance, and the second distance; calculating a first compensation angle according to the first deflection angle and the first predetermined angle, and Rotate the distance measuring device and the calibration platform around the second direction by the first compensation angle, so that the depth camera rotates from the second position to a third position, and when the depth camera is at the third position, the optical axis is perpendicular to the intersection line of the first calibration surface and the calibration surface; When the distance measuring member and the calibration platform are located at a fourth position, the distance measuring member senses a third distance between the depth camera and the calibration surface; The column rotates about the first direction by a second predetermined angle, so that the depth camera rotates from the fourth position to a fifth position, and the distance measuring component senses a fourth distance between the depth camera and the calibration surface; Calculating a second deflection angle between the calibration surface and the second direction according to the second predetermined angle, the third distance, and the fourth distance; Calculating a second compensation angle according to the second deflection angle and the second predetermined angle; as well as The column is rotated around the first direction by the second compensation angle to rotate the depth camera from the fifth position to a sixth position. When the depth camera is at the sixth position, the light-emitting axis of the depth camera is perpendicular to the calibration surface.

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