Calibration method and apparatus for three-dimensional sensing devices - Patents.com

Abstract

A calibration method for a three-dimensional sensing device including an optical output unit and an optical receiving unit according to an embodiment of the present invention includes a step of performing a first calibration for a two-dimensional image using a first target board, and a step of performing a second calibration for distance using a second target board, wherein the distance between the three-dimensional sensing device and the first target board, and the distance between the three-dimensional sensing device and the second target board are each set to be shorter than the minimum measurable distance of the three-dimensional sensing device.

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present invention relate to calibration, and more particularly to a calibration method and apparatus for a three-dimensional sensing device. [Background technology]

[0002] Location recognition technology has become an essential technology in various fields such as vehicles, robots, games, and artificial intelligence. A typical example of a 3D sensing device used in location recognition technology is a Lidar device. A Lidar device emits a laser pulse and calculates the distance to an object by using the time it takes for the laser pulse to be reflected from the object and return.

[0003] Generally, LIDAR devices are divided into short-range LIDAR devices that measure distances from a few centimeters to a few meters, and long-range LIDAR devices that measure distances from tens of meters to hundreds of meters.

[0004] The LIDAR device may include an optical output unit including a light source, and an optical receiving unit including a sensor. During the assembly process of the LIDAR device, distortion may occur due to distortion between internal parts or a structural problem between the optical output unit and the optical receiving unit in the LIDAR device. For this reason, during the manufacturing stage of the LIDAR device, a calibration process is essential to correct the distortion after assembly.

[0005] The calibration procedure can be performed using a target chart and a calibration device placed within a discernible distance of the lidar device.

[0006] Long-distance LIDAR equipment requires a space of tens to hundreds of meters for calibration work, resulting in low unit per hour (UPH). Summary of the Invention [Problem to be solved by the invention]

[0007] A technical problem to be solved by the present invention is to provide a calibration method and apparatus for a three-dimensional sensor device. [Means for solving the problem]

[0008] A calibration method for a three-dimensional sensing device including an optical output unit and an optical receiving unit according to one embodiment of the present invention includes a step of performing a first calibration for a two-dimensional image using a first target board, and a step of performing a second calibration for distance using a second target board, wherein the distance between the three-dimensional sensing device and the first target board, and the distance between the three-dimensional sensing device and the second target board are each set to be shorter than the minimum measurable distance of the three-dimensional sensing device.

[0009] Each of the distance between the three-dimensional sensing device and the first target board and the distance between the three-dimensional sensing device and the second target board may be less than or equal to 1 / 2 of the minimum distance measurable by the three-dimensional sensing device.

[0010] In the step of performing the first calibration, light output by a light source, reflected by the first target board, and then input to the optical receiving unit of the three-dimensional sensing device is used, and the wavelength of the light output by the light source may be included in the wavelength range of the light output by the optical output unit included in the three-dimensional sensing device.

[0011] The light source may be disposed on the same plane as the light output unit included in the three-dimensional sensing device, and an angle of view of the light output by the light source may be larger than an angle of view of the light output by the light output unit.

[0012] In the step of performing the second calibration, light is output by the optical output unit of the three-dimensional sensing device, passes through an optical element, is reflected by the second target board, and then is input to the optical receiving unit of the three-dimensional sensing device, and the optical element may be positioned in the optical path between the optical output unit and the second target board.

[0013] The optical member may include at least one of a collimator, a mirror, and a prism.

[0014] The three-dimensional sensing device may be a LiDAR.

[0015] A calibration apparatus for a three-dimensional sensing device including an optical output unit and an optical receiving unit according to one embodiment of the present invention includes a first calibration unit including a first computing unit that performs a first calibration for a two-dimensional image using a first target board, and a second calibration unit including a second computing unit that performs a second calibration for distance using a second target board, wherein the distance between the three-dimensional sensing device and the first target board and the distance between the three-dimensional sensing device and the second target board are each set to be shorter than the minimum measurable distance of the three-dimensional sensing device.

[0016] The first calibration unit may further include a light source, and a wavelength of the light output by the light source may be included in a wavelength range of the light output by the light output unit included in the three-dimensional sensing device.

[0017] The angle of view of the light output by the light source may be larger than the angle of view of the light output by the light output section.

[0018] The second calibration unit may further include an optical member disposed in an optical path between the light output unit and the second target board.

[0019] The optical member may include at least one of a collimator, a mirror, and a prism. Effect of the Invention

[0020] According to one embodiment of the present invention, the LIDAR device can be calibrated even at a distance shorter than the recognition distance of the LIDAR device, thereby increasing the UPH of the LIDAR device. [Brief description of the drawings]

[0021] [Figure 1] 1 is a diagram illustrating a LIDAR device according to an embodiment of the present invention and its distance recognition principle.

[0022] [Diagram 2] 1 is a block diagram of a calibration device according to an embodiment of the present invention;

[0023] [Diagram 3] FIG. 4 is a procedure diagram showing a calibration method of the calibration device according to the embodiment of the present invention.

[0024] [Figure 4] FIG. 13 is a conceptual diagram of a first calibration.

[0025] [Diagram 5] FIG. 11 is a conceptual diagram of a second calibration.

[0026] [Figure 6] 1 is an example of a target board applied to a calibration method according to an embodiment of the present invention.

[0027] [Figure 7] FIG. 11 is a conceptual diagram of a first calibration unit of a calibration device according to another embodiment of the present invention.

[0028] [Figure 8] 1 is a diagram illustrating a simulation method using a calibration device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0030] However, the technical concept of the present invention is not limited to the embodiments described, but may be embodied in various different forms, and one or more of the components of the embodiments may be selectively combined or substituted within the scope of the technical concept of the present invention.

[0031] Furthermore, unless otherwise explicitly defined and described, terms (including technical and scientific terms) used in the embodiments of the present invention may be interpreted as meanings that can be commonly understood by a person having ordinary knowledge in the technical field to which the present invention belongs, and commonly used terms, such as terms defined in a dictionary, may be interpreted in light of the contextual meaning of the relevant art.

[0032] Furthermore, the terms used in the embodiments of the present invention are intended to describe the embodiments and are not intended to limit the present invention.

[0033] In this specification, the singular form can include the plural form unless otherwise specified in the phrase, and when it is described as "A and (and) at least one (or more) of B and C", it can include one or more of all possible combinations of A, B, and C.

[0034] Additionally, terms such as first, second, A, B, (a), (b), etc. may be used in describing components of embodiments of the present invention.

[0035] Such terms are used merely to distinguish a component from other components, and are not intended to limit the nature, order, or procedure of the component.

[0036] Furthermore, when a component is described as being "coupled," "coupled," or "connected" to another component, this includes not only cases where the component is directly coupled, coupled, or connected to the other component, but also cases where the component is "coupled," "coupled," or "connected" by another component or between the component and the other component.

[0037] In addition, when described as being formed or disposed "above or below" each component, above or below includes not only the case where two components are in direct contact with each other, but also the case where one or more other components are formed or disposed between the two components. In addition, when described as "above or below," it can include not only the upper direction but also the lower direction based on one component.

[0038] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Regardless of the reference numerals, the same or corresponding elements are designated by the same reference numerals, and redundant description thereof will be omitted.

[0039] FIG. 1 is a diagram illustrating a LIDAR device according to an embodiment of the present invention and its distance recognition principle.

[0040] Referring to FIG. 1, a LiDAR (Light Detection And Ranging) device 10 includes an optical output unit Tx and an optical receiving unit Rx, as well as a control unit (not shown) and a distance calculation unit (not shown).

[0041] The light output unit Tx of the LIDAR device 10 irradiates light onto an object, the light receiving unit Rx receives the light reflected from the object and returning, and the distance calculation unit (not shown) calculates the distance between the LIDAR device 10 and the object using the time between irradiating the light and receiving it. The control unit (not shown) controls the entire LIDAR device 10. At least one of the control unit (not shown) and the distance calculation unit (not shown) may be located in the same space as the light output unit Tx and the light receiving unit Rx, or may be located in a different space.

[0042] The optical output unit Tx generates an output optical signal and then irradiates the output optical signal on an object. The output optical signal may include optical pulses generated at a constant period. To this end, the optical output unit Tx may include a light source and a lens assembly.

[0043] The light generated by the light source may be infrared light having a wavelength of 770 nm to 3000 nm, preferably 800 nm to 1000 nm, more preferably 850 nm to 940 nm, and for this purpose, the light source may include a laser diode (LD) or a VCSEL (Vertical Cavity Surface Emitting Laser). The light source generates an output optical signal in the form of a pulse wave or continuous wave by repeatedly turning on and off at a fixed time interval, and the fixed time interval may be the frequency of the output optical signal.

[0044] The lens assembly may collect light output from the light source and output the collected light to the outside. The lens assembly may be disposed above the light source and spaced apart from the light source. Here, the above of the light source may refer to the side from which light is output from the light source. The lens assembly may include at least one lens. When the lens assembly includes a plurality of lenses, the lenses may be aligned based on a central axis to form an optical system. Here, the central axis may be the same as the optical axis of the optical system.

[0045] The optical receiver (Tx) may include a lens assembly and a light receiving sensor. The light receiving sensor can receive infrared light that has passed through the lens assembly after being reflected from an object.

[0046] The recognizable distance of the LIDAR device 10 may vary depending on the angle of view of the light output unit Tx. For example, within a first distance d1, light that is irradiated from the light output unit Tx and then reflected from an object cannot be received by the light receiving unit Rx, and therefore an object present within the first distance d1 cannot be recognized by the LIDAR device 10. On the other hand, within a second distance d2, light that is irradiated from the light output unit Tx and then reflected from an object can be received by the light receiving unit Rx, and therefore an object present within the second distance d2 can be recognized by the LIDAR device 10.

[0047] Meanwhile, distortion may occur during the assembly process of the LIDAR device 10 due to distortion between internal parts or structural problems between the optical output unit and the optical receiving unit in the LIDAR device. As a result, a calibration process is required to correct the distortion after assembly during the manufacturing stage of the LIDAR device 10.

[0048] The calibration procedure can be performed using a target board and calibration device placed within a recognizable distance of the lidar device 10.

[0049] Long-distance LIDAR equipment requires a space of tens to hundreds of meters for calibration work, resulting in low unit per hour (UPH).

[0050] According to an embodiment of the present invention, an object is to efficiently calibrate a LIDAR device within a distance shorter than the recognition distance of the LIDAR device.

[0051] FIG. 2 is a block diagram of a calibration device according to one embodiment of the present invention, FIG. 3 is a procedural diagram showing a calibration method of the calibration device according to one embodiment of the present invention, FIG. 4 is a conceptual diagram of the first calibration, and FIG. 5 is a conceptual diagram of the second calibration.

[0052] 2 and 3, a first calibration unit 210 of the calibration device 200 performs a first calibration for a two-dimensional image using a first target board (S300), and a second calibration unit 220 of the calibration device 200 performs a second calibration for distance using a second target board (S310).

[0053] Here, the first calibration for the two-dimensional image refers to calibration for the X coordinate, Y coordinate, and yaw value on a two-dimensional plane facing the LIDAR device 10, and the second calibration for the distance refers to calibration for the Z coordinate, pitch value, and roll value perpendicular to the two-dimensional plane. Here, the calibration for the X coordinate, Y coordinate, Z coordinate, yaw value, pitch value, and roll value refers to software calibration, and a known software calibration technique can be applied.

[0054] According to an embodiment of the present invention, the first calibration for the two-dimensional image and the second calibration for the distance are performed separately, thereby minimizing the space required for calibration.

[0055] 1 to 5, the first calibration unit 210 includes a first computing unit 212. Here, the first computing unit 212 calculates an X coordinate, a Y coordinate, and a yaw value on a two-dimensional plane facing the LIDAR device 10. According to an embodiment of the present invention, in order to perform the first calibration in step S300, the first target board TB1 is disposed within the minimum measurable distance a of the LIDAR device 10. That is, the distance a1 between the LIDAR device 10 and the first target board TB1 is set to be shorter than the minimum measurable distance a of the LIDAR device 10. For example, the distance a1 between the LIDAR device 10 and the first target board TB1 may be set to be equal to or smaller than 1 / 2 of the minimum measurable distance a of the LIDAR device 10. For example, even in the case of a long-distance LIDAR device in which the minimum measurable distance is several meters, the distance between the LIDAR device 10 and the first target board TB1 may be set to within several tens of centimeters.

[0056] When the distance between the LIDAR device 10 and the first target board TB1 is shorter than the minimum distance measurable by the LIDAR device 10, the light output from the optical output unit Tx of the LIDAR device 10 cannot be received by the optical receiving unit Rx after being reflected from the first target board TB1. Meanwhile, in the step of performing the first calibration (S300), calibration is not performed for the Z coordinate, i.e., the distance between the LIDAR device 10 and the first target board TB1, so the light received by the optical receiving unit Rx of the LIDAR device 10 does not necessarily have to be the light output from the optical output unit Tx.

[0057] Accordingly, the first calibration unit 210 may further include a light source 214. That is, according to an embodiment of the present invention, in the step of performing the first calibration, light output by the light source 214 included in the first calibration unit 210 of the calibration device 200, reflected by the first target board TB1, and then input to the light receiving unit Rx of the LIDAR device 10 may be used. At this time, the angle of view of the light source 214 may be set to irradiate at least a part of the area, preferably the entire area, of the first target board TB1. According to this, even if the distance between the LIDAR device 10 and the first target board TB1 is within the minimum measurable distance of the LIDAR device 10, calibration for the two-dimensional image is possible. At this time, the wavelength of the light output by the light source 214 may be included in the wavelength range of the light output by the light output unit Tx included in the LIDAR device 10. For example, the wavelength of the light output by the light source 214 may be the same as the wavelength of the light output by the light output unit Tx included in the LIDAR device 10. According to this, light output by the light source 214 included in the first calibration unit 210 of the calibration device 200 and reflected by the first target board TB1 can be sensed by the optical receiving unit Rx of the LIDAR device 10.

[0058] For example, the light source 214 included in the first calibration unit 210 may be disposed on the same plane as the optical output unit Tx of the LIDAR device 10, and the angle of view of the light output by the light source 214 included in the first calibration unit 210 may be larger than the angle of view of the light output by the optical output unit Tx of the LIDAR device 10. In this way, even if the distance between the LIDAR device 10 and the first target board TB1 is within the minimum measurable distance of the LIDAR device 10, the optical receiving unit Rx of the LIDAR device 10 can receive light reflected from the first target board TB1, making it possible to calibrate a two-dimensional image.

[0059] Meanwhile, the second calibration unit 220 includes a second computing unit 222. Here, the second computing unit 222 calculates a distance perpendicular to a two-dimensional plane facing the LIDAR device 10, i.e., a Z coordinate, a pitch value, and a roll value. According to an embodiment of the present invention, in order to perform the second calibration in step S310, the second target board TB2 is disposed within the minimum measurable distance a of the LIDAR device 10. That is, the distance a2 between the LIDAR device 10 and the second target board TB2 is set to be shorter than the minimum measurable distance of the LIDAR device 10. For example, the distance a2 between the LIDAR device 10 and the second target board TB2 may be set to be equal to or smaller than 1 / 2 of the minimum measurable distance of the LIDAR device 10. For example, even in the case of a long-distance LIDAR device in which the minimum measurable distance is several meters, the distance between the LIDAR device 10 and the second target board TB2 can be set to within several tens of centimeters.

[0060] If the distance between the LIDAR device 10 and the second target board TB2 is shorter than the minimum distance measurable by the LIDAR device 10, the light output from the optical output unit Tx of the LIDAR device 10 cannot be received by the optical receiving unit Rx after being reflected from the second target board TB2. Meanwhile, in the step of performing the second calibration (S310), calibration is performed for the Z coordinate, i.e., the distance between the LIDAR device 10 and the first target board TB1, so the light received by the optical receiving unit Rx of the LIDAR device 10 must necessarily be the light output from the optical output unit Tx.

[0061] For this purpose, the second calibration unit 220 may further include an optical member 224, which may be disposed between the optical path between the LIDAR device 10 and the second target board TB2. For example, the optical member 224 may include at least one of a collimator, a mirror, and a prism. The optical member 224 may be disposed in front of the optical output unit Tx of the LIDAR device 10 to change the path of the light output from the optical output unit Tx, or may be disposed in front of the optical output unit Tx and the optical receiving unit Rx of the LIDAR device 10 to change the path of at least one of the light output from the optical output unit Tx and the light received by the optical receiving unit Rx. That is, according to an embodiment of the present invention, in the step of performing the second calibration, the light output by the optical output unit Tx of the LIDAR device 10, passing through the optical member 224, and being reflected by the second target board TB2 and then input to the optical receiving unit Rx of the LIDAR device 10 may be used. According to this, even if the distance between the LIDAR device 10 and the second target board TB2 is within the minimum distance measurable by the LIDAR device 10, the light reflected by the second target board TB2 after being output from the light output unit Tx of the LIDAR device 10 can be received by the light receiving unit Rx of the LIDAR device 10 by changing the light path using the optical member 224, and this can be used to calibrate the distance.

[0062] In this way, when calibration for a two-dimensional image and calibration for distance are performed separately, the space and time required for calibration can be minimized and highly accurate calibration can be achieved.

[0063] Although the first target board TB1 and the second target board TB2 have been described above as being separate target boards, this is not limiting, and the first target board TB1 and the second target board TB2 may be the same target board.

[0064] As described above, according to an embodiment of the present invention, the distance between the LIDAR device and the target board can be set to be shorter than the minimum distance measurable by the LIDAR device. This allows the area of ​​the target board to be reduced compared to a case where the target board is placed farther away than the minimum distance measurable by the LIDAR device. When the area of ​​the target board is reduced, the tact time required to scan the target board once can be reduced, and thus the total time required for calibration can be reduced.

[0065] 6 is an example of a target board applied to the calibration method according to the embodiment of the present invention. At least one of the first target board TB1 and the second target board TB2 according to the embodiment of the present invention may be the target board according to the embodiment of FIG.

[0066] Referring to FIG. 6, the target board may include an array of dot patterns P spaced apart from each other at a predetermined interval, and the dot patterns may be brighter than the background. The interval X1 between the dot patterns may be greater than the diameter X2 of one dot pattern. For example, the interval X1 between the dot patterns may be at least twice the diameter X2 of one dot pattern, preferably at least 2 times and at most 10 times, more preferably at least 2.5 times and at most 5 times. According to this, since it is only necessary to scan the dot patterns in the target board during calibration for a two-dimensional image or calibration for a distance, the tact time required to scan the target board once can be shortened compared to a target board such as a checkerboard, and thus the total time required for calibration can be shortened.

[0067] FIG. 7 is a conceptual diagram of a first calibration unit of a calibration device according to another embodiment of the present invention.

[0068] 7, the light source 214 of the first calibration unit 210 may be disposed on the first target board TB1. For example, when the first target board TB1 is the target board shown in FIG. 6, the light source 214 may be disposed at least in part at the position of the dot pattern. In this way, the light output from the light source 214 of the first calibration unit 214 can be received by the light receiving unit Rx of the LIDAR device 10, and thus calibration for the 2D image is possible even if the first target board TB1 is disposed within the minimum measurable distance of the LIDAR device 10.

[0069] In this case, the light source 214 arranged on the first target board TB1 may be a plurality of light sources, and the plurality of light sources may be arranged at regular intervals so that the light received by the optical receiver Rx from the first target board TB1 may have a uniform light distribution.

[0070] FIG. 8 is a diagram for explaining a simulation method using the calibration device according to the embodiment of the present invention.

[0071] FIG. 8(a) shows Example 1 in which a mirror 800 is placed on the optical path of the lidar device 10 to change the path of the light output from the optical output unit Tx of the lidar device 10. FIG. 8(b) shows Example 2 in which a collimator 810 is placed on the optical path of the lidar device 10 to change the path of the light output from the optical output unit Tx of the lidar device 10. FIG. 8(c) shows Example 3 in which a prism 820 is placed on the optical path of the lidar device 10 to change the path of the light output from the optical output unit Tx of the lidar device 10.

[0072] In all of Examples 1 to 3, the reflection angle with respect to the second target board was 30°, and the mounting error when mounting the LIDAR device 10 on the calibration device was set in the range of -1 mm to +1 mm. In Example 1, the tilt angle of the mirror 800 was set to 75°, in Example 2, the distance between the collimator 810 and the second target board was set to 3 m, and the focal length was set to 0.5 m, and in Example 3, the prism angle was set to 30°, and the refraction angle was set to 30°.

[0073] According to the first to third embodiments, even if a certain refraction error occurs when the light output from the light output unit Tx passes through the optical members 800, 810, and 820, the reception error received by the light input unit Rx is within the allowable range. This shows that calibration is possible even if the mounting error when mounting the LIDAR device 10 on the calibration device is within the range of −1 mm to +1 mm.

[0074] The term "unit" used in this embodiment means software or hardware components such as a field-programmable gate array (FPGA) or an ASIC, and the "unit" plays a specific role. However, the "unit" is not limited to software or hardware. The "unit" may be configured to reside in an addressable storage medium and to reproduce one or more processors. Thus, by way of example, the "unit" includes components such as software components, object-oriented software components, class components, and task components, as well as processes, functions, attributes, procedures, subroutines, program code segments, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The components and functions provided within the "unit" may be combined into a smaller number of components and "units" or further separated into additional components and "units". Furthermore, the components and "units" may be embodied to reproduce one or more CPUs in a device or a security multimedia card.

[0075] Although the present invention has been described with reference to preferred embodiments thereof, those skilled in the art will understand that the present invention can be modified and changed in various ways without departing from the spirit and scope of the present invention as set forth in the following claims.

Claims

1. A calibration method for a three-dimensional sensing device including an optical output unit and an optical receiving unit, comprising: performing a first calibration for a two-dimensional image using a first target board; and performing a second calibration for distance using a second target board; A calibration method, wherein the distance between the three-dimensional sensing device and the first target board and the distance between the three-dimensional sensing device and the second target board are each set to be shorter than the minimum measurable distance of the three-dimensional sensing device.

2. 2. The calibration method according to claim 1, wherein each of a distance between the three-dimensional sensing device and the first target board and a distance between the three-dimensional sensing device and the second target board is less than or equal to 1 / 2 of a minimum distance measurable by the three-dimensional sensing device.

3. In the step of performing the first calibration, using light outputted by a light source, reflected by the first target board, and then inputted to the light receiving unit of the three-dimensional sensing device; The calibration method according to claim 1 , wherein a wavelength of the light output by the light source is included in a wavelength range of the light output by the light output unit included in the three-dimensional sensing device.

4. 4. The calibration method according to claim 3, wherein the light source is disposed on the same plane as the light output unit included in the three-dimensional sensing device, and an angle of view of the light output by the light source is larger than an angle of view of the light output by the light output unit.

5. In the step of performing the second calibration, using light output by the optical output unit of the three-dimensional sensing device, passing through an optical member, being reflected by the second target board, and then being input to the optical receiving unit of the three-dimensional sensing device; The calibration method according to claim 1 , wherein the optical member is disposed in an optical path between the optical output unit and the second target board.

6. The calibration method according to claim 5 , wherein the optical member includes at least one of a collimator, a mirror, and a prism.

7. The calibration method of claim 1 , wherein the three-dimensional sensing device is a LiDAR.

8. A calibration apparatus for a three-dimensional sensing device including an optical output unit and an optical receiving unit, a first calibration unit including a first computing unit that performs a first calibration on a two-dimensional image using a first target board; a second calibration unit including a second computing unit that performs a second calibration for distance using a second target board; A calibration apparatus, wherein the distance between the three-dimensional sensing device and the first target board and the distance between the three-dimensional sensing device and the second target board are each set to be shorter than the minimum measurable distance of the three-dimensional sensing device.

9. The first calibration unit further includes a light source; The calibration apparatus according to claim 8 , wherein a wavelength of the light output by the light source is included in a wavelength range of the light output by the light output unit included in the three-dimensional sensing device.

10. The calibration device according to claim 9 , wherein an angle of view of the light output by the light source is larger than an angle of view of the light output by the light output section.

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