JP2010219663A - Calibration method and calibration system for imager - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a calibration method and a calibration system for an imager, which can be operated at a low cost with proper working efficiency. <P>SOLUTION: A method for calibrating an imager, comprising the steps of: as a first step, arranging an irradiation device 20 for emitting of a plurality of laser beams at a position decided beforehand in relation to a vehicle; as a second step, positioning a target board 30 for calibration in relation to an imager selected out of a plurality of imagers, using the plurality of laser beams; as a third step, photographing the target board 30 by the selected imager and storing the image data in a memory; as a fourth step, performing the first step or the third step repeatedly to each of the plurality of imagers; and as a fifth step, performing electronic calibration for each imager using the image data stored in the memory. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an in-vehicle imaging device that displays imaging data around a vehicle on an in-vehicle display, and more particularly to calibration of the in-vehicle imaging device.

  The mounting rate of in-vehicle cameras has increased, and accordingly, applications using imaging data are being developed. As a typical application, there is a top view display in which a horizontal direction of a vehicle is imaged, and the captured image data is converted from a viewpoint and displayed as an image viewed from above the vehicle. Since the top view display synthesizes the imaging data in the front-rear and left-right directions of the vehicle, if an error occurs in the mounting position of the imaging camera, distortion occurs in the joint between the images of the top view display. For this reason, the position accuracy of the imaging camera must be high.

  Patent Document 1 relates to a calibration method for an imaging apparatus, and captures a calibration pattern such as a circle with an imaging apparatus, and measures an installation state of the imaging apparatus on a vehicle from an image of the captured calibration pattern. Thereby, there is no optical axis adjustment of the imaging device for every vehicle, and the positional accuracy of the imaging device is guaranteed.

JP 2001-116515 A

  FIG. 1 is a diagram for explaining a conventional calibration method for an in-vehicle camera. Four imaging cameras 2a, 2b, 2c, and 2d are attached to the front, rear, left and right of the vehicle M. In order to calibrate the four imaging cameras 2a to 2d, the same number of target boards 4a, 4b, 4c, and 4d as the imaging cameras 2a to 2d are prepared. The target board is synonymous with a calibration board for calibrating the imaging camera. Each target board 4a-4d is positioned with respect to each imaging camera 2a-2d. This positioning is performed by, for example, arranging the vehicle M at a predetermined position and arranging the target boards 4a to 4d at predetermined positions. The positioned target boards 4a to 4d are imaged in the imaging field of each imaging camera 2a to 2d, and the position information of the imaged target board in the field of view is compared with the reference position information registered in the memory in advance. Then, the imaging range is adjusted so that the difference from the reference position information is eliminated, and calibration is performed.

  However, the conventional calibration method has the following problems. Since the number of target boards is the same as the number of imaging cameras, many target boards are required when performing calibration for each vehicle, and the cost of the target boards increases. Further, although the target board is arranged at a position determined in advance by manual work, since the arrangement conditions vary depending on the vehicle type and the type of the imaging camera, the work efficiency of calibration is not good.

  An object of the present invention is to solve such a conventional problem and to provide a calibration method for an in-vehicle imaging device that is low in cost and has high work efficiency.

  A method of calibrating a plurality of imaging devices attached to a vehicle according to the present invention includes a first step of arranging an irradiation device that emits a plurality of lights at a predetermined position with respect to the vehicle, A second step of positioning a calibration target board using the plurality of lights, and imaging the target board by the selected imaging device, the imaging device selected from among the imaging devices; A third step of storing imaging data in the memory, a fourth step of repeating the first to third steps for each of a plurality of imaging devices, and the imaging data stored in the memory, respectively. And a fifth step of performing electronic calibration of the imaging apparatus.

  Preferably, the irradiation device emits a pair of parallel laser beams and a distance measurement laser beam emitted at a predetermined emission angle with respect to the parallel laser beams, A first mark capable of irradiating the set of parallel laser beams and a second mark capable of irradiating the distance measuring laser beam are formed, and the one set of parallel laser beams and the first mark are formed. The parallelism of the target board can be adjusted from the relationship with the mark, and the distance between the target board and the imaging device can be adjusted from the relationship between the laser light for distance measurement and the second mark.

  In the method for calibrating a plurality of imaging devices attached to a vehicle according to the present invention, a positioning member having a plurality of rod-shaped members in a direction corresponding to the plurality of imaging devices is set at a predetermined position with respect to the vehicle. A first step of arranging, a second step of attaching a calibration target board to a rod-shaped member corresponding to the imaging device selected from the plurality of imaging devices, and the target by the selected imaging device. A third step of imaging the board and storing the imaging data in a memory; a fourth step of repeatedly performing the first to third steps for each of a plurality of imaging devices; And a fifth step of performing electronic calibration of each imaging apparatus using the imaging data.

  A system for calibrating a plurality of imaging devices attached to a vehicle according to the present invention is arranged at a predetermined position with respect to the vehicle, and an irradiation device that emits a plurality of laser beams, and for calibration of the imaging device A movable target board, and calibration means for performing electronic calibration of the imaging apparatus based on imaging data obtained by imaging the target board, and the irradiation apparatus includes a pair of parallel laser beams, A distance measuring laser beam emitted at a predetermined emission angle with respect to the parallel laser beam, and the target board is configured to emit a first set of parallel laser beams. A relationship between the pair of parallel laser beams and the first mark, including a mark and a second mark capable of irradiating the distance measuring laser beam. The parallelism of the target board can be adjusted, the distance between the target board and the imaging device can be adjusted from the relationship between the laser beam for distance measurement and the second mark, and the calibration means can select The image pickup apparatus is caused to pick up an image of the target board whose parallelism and distance are adjusted, and the image pickup data of the target board is stored in the memory.

  A system for calibrating a plurality of imaging devices attached to a vehicle according to the present invention is positioned at a predetermined position with respect to the vehicle and has a plurality of rod-shaped members in a direction corresponding to the plurality of imaging devices. An imaging device based on imaging data obtained by imaging the target board, a target board for calibration of the imaging device, and a target board that can be detachably attached to the selected rod-like member of the plurality of rod-like members Calibration means for performing a calibrated calibration, and when the target board is attached to the selected rod-shaped member, the calibration means causes the corresponding imaging device to image the target board and image the target board. Store data in memory.

  Preferably, the positioning member has a cross shape in which the rod-shaped members are orthogonal to each other, and an end portion of the rod-shaped member is provided with a fitting portion for fixing the target board.

  According to the present invention, the calibration of the imaging apparatus can be performed using one target board, so that the cost for calibration can be reduced and the working efficiency can be improved.

It is a figure explaining the conventional calibration method. It is a figure which shows the structure of the calibration system for implementing the calibration of the imaging camera which concerns on the Example of this invention. It is a schematic plan view explaining the structure of the irradiation apparatus of a present Example. It is a schematic perspective view explaining the target board of a present Example. It is a flowchart which shows the calibration method which concerns on 1st Example of this invention. It is a schematic plan view which shows the positional relationship of an irradiation apparatus and an imaging camera. It is a flowchart which shows the positioning operation | movement of the target board shown in FIG. It is a schematic side view explaining the positional relationship between a vehicle and a target board. It is a figure explaining the adjustment method of the parallelism and distance of a target board. It is a figure explaining the usage example of a target board. It is a figure explaining the example of the electronic calibration of an imaging device. It is a figure explaining the calibration method which concerns on 2nd Example of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 2 is a block diagram showing a configuration of a calibration system used for performing the calibration of the present embodiment. The calibration system 10 of the present embodiment includes an irradiation device 20 having a plurality of laser light sources that emit laser light, a target board 30 that is positioned using the laser light emitted from the irradiation device 20, and a target board 30. A vehicle-mounted imaging camera 40 that captures an image and a calibration device 50 that calibrates the imaging camera 40 based on imaging data from the imaging camera 40 are provided. In the present embodiment, it is assumed that four imaging cameras 40 are installed on the front, rear, left and right sides of the vehicle.

  As shown in FIG. 3, the irradiation device 20 preferably has a rectangular housing 22 and a plurality of laser light sources installed in the housing 22. FIG. 3 shows an example in which three laser light sources La, Lb, and Lc are arranged in the housing 22, and three laser beams L 1, L 2, and L 3 are emitted from one side surface 24 of the housing 22. The laser light sources La and Lc are spaced from each other by a distance D and emit laser beams L1 and L3 parallel to each other from the side surface 24. The laser light source Lb is adjacent to the light source La and emits the laser light L2 in a direction in which the emission angle with the laser light L1 is θ. Although details are not shown in the drawing, the irradiation device 20 can emit three laser beams L1, L2, and L3 from four side surfaces of the housing 22, respectively.

  FIG. 4 is a perspective view showing the configuration of the target board 30 of this embodiment. As shown in the figure, the target board 30 is made of an L-shaped member such as metal or resin, and includes a flat plate-like base portion 32 and a plate-like alignment portion 34 extending vertically from the base portion 32. Have. In the alignment unit 34, three black circular marks Ta, Tb, Tc are arranged in a line at the same height, and these marks Ta, Tb, Tc are emitted from the laser beam L1 from the irradiation device 20. , L2 and L3 are used for visually confirming the irradiation. Further, three column patterns 36 are formed on the base 32, and the three column patterns 36 are arranged so as to be in the same column as the marks Ta, Tb, and Tc, respectively. The three column patterns 36 are used when finely adjusting the irradiation of the marks Ta, Tb, and Tc with the laser beams L1, L2, and L3, or are captured by an imaging camera, and the image of the column pattern 36 is calibrated. Used for

  Next, a calibration method of the imaging camera using the target board will be described with reference to the flowchart of FIG. First, the irradiation device 20 is installed at a predetermined position with respect to the vehicle M (step S10). FIG. 6 is a plan view showing the positional relationship between the irradiation device 20 and the vehicle M. FIG. In the present embodiment, the imaging cameras 40a, 40b, 40c, and 40d are attached to the front, rear, left and right of the vehicle. As will be described later, the irradiation device 20 is installed between the vehicle M and the ground, and the optical axes of the laser light sources La and Lc (laser beams L1 and L3) of the irradiation device 20 are the imaging cameras 40a, 40b, 40c, respectively. It is installed so as to substantially coincide with the optical axis direction of 40d.

  Next, the target board 30 is positioned with respect to any one of the imaging cameras 40a to 40d (step S11). When the positioning of the target board 30 is completed, the calibration device 50 causes the imaging camera 40 to image the target board 30 (step S12), and stores the imaging data of the target board 30 in the memory (step S13). Steps S11 to S13 are performed for all the imaging cameras 40 (step S14). When the imaging of the target board 30 by all the imaging cameras is completed, the calibration device 50 performs electronic calibration of each imaging camera 40 based on the imaging data of the target board 30 stored in the memory (Step S15). ). For example, in electronic calibration, for example, position information of an image of the target board 30 is detected, the detected position information is compared with reference position information registered in advance in a memory, and the imaging camera is based on the difference between the two. Adjust the trimming area of the image data.

  Next, the target board positioning method in step 11 will be described in detail with reference to the flowchart of FIG. As shown in FIG. 6, the irradiation device 20 is installed on the ground just below the center of the vehicle M. Next, the target board 30 is arranged for the selected one imaging camera (step S101). Here, the target board 30 shall be arrange | positioned regarding the imaging camera 40a.

  Next, the irradiation apparatus 20 irradiates the laser beams L1, L2, and L3 (step S102). The irradiation device 20 does not need to emit laser light simultaneously in the four directions of front, rear, left and right of the vehicle, and it is sufficient to irradiate only the laser light in the front direction of the vehicle (that is, the imaging direction of the imaging camera 40a). FIG. 8 shows an example in which the target board 30 is arranged in front of the vehicle. Preferably, the base 32 of the target board 30 is positioned at a position where marking or the like is indicated. At this time, the alignment unit 34 is in an upright state substantially vertically from the ground, and a pair of parallel laser beams L1 and L3 emitted from the side surface 24 of the irradiation device 20, and the laser beam L1 and the emission angle are θ and The laser beam L2 is irradiated to the alignment unit 34.

  Next, the parallelism of the target board 30 is adjusted (step S103). FIG. 9 is a diagram for explaining a method of adjusting the parallelism and distance with the target board. The distance between the light sources La and Lc of the laser beams L1 and L3 is D. The marks Ta, Tb and Tc on the alignment portion 34 of the target board 30 are arranged in a line, and the center distance between the marks Ta and Tc is D. It is. When the laser beams L1 and L3 are irradiated to the marks Ta and Tc of the alignment unit 34, the alignment unit 34 is parallel to the irradiation device 20, that is, the imaging camera 40a. The user finely adjusts the position of the target 30 so that the marks Ta and Tc are irradiated with the laser beams L1 and L3.

  Next, the distance between the target board 30 and the imaging camera 40a is adjusted (step S104). The laser beam L2 is for distance measurement, and is emitted at an emission angle θ with respect to the laser beam L1. The interval between the marks Ta and Tb of the alignment unit 34 is a. The user adjusts the position of the target board 30 so that the mark Tb is irradiated with the laser light L2. In addition, the distance b from the target board 30 to the irradiation apparatus 20 is represented by b = a / tan θ. When adjusting the distance, it is necessary to maintain a state in which the parallelism is maintained. Therefore, while visually confirming that the laser beams L1 and L3 pass through the column pattern 36, the target board 30 is moved back and forth. Can be moved to.

  Thus, with respect to the imaging camera 40a, the parallelism and distance of the target board 30 are adjusted, and the positioning is completed (step S105). For example, when the user inputs an instruction to complete positioning of the target board to the calibration device 50, the calibration device 50 causes the imaging camera 40a to image the target board 30 in response thereto. The positioned target board 30 is projected in the field of view of the imaging camera 40a, and the imaging data is stored in the internal memory. When the imaging data is saved, the user moves the target board, and the target board is arranged for calibration for the next imaging camera.

  FIG. 10 is a diagram for explaining how to use the target board 30 of this embodiment. As shown in the figure, for example, the target board 30 is adjusted in parallelism and distance with respect to the imaging camera 40a and is imaged by the imaging camera 40a. Next, regarding the imaging cameras 40b, 40c, and 40d, the target board 30 is imaged after being similarly aligned. Through the above processing, the calibration device 50 stores the imaging data of the target board 30 captured by the imaging cameras 40a, 40b, 40c, and 40d. And the calibration apparatus 50 performs electronic calibration about each of imaging camera 40a-40d.

  Next, an electronic calibration method for the imaging camera will be described. As shown in FIG. 11, the field-of-view range P that can be captured by an imaging camera using a wide-angle lens can project a wide range of peripheral conditions with a constant aspect ratio, but the end of the field-of-view range P is distorted. Therefore, the central region with less distortion is trimmed and used for the image of the top view display. FIG. 11A shows the relationship between the visual field range P and the image P1 of the target board 30 when the ideally positioned target board 30 is imaged by the imaging camera. When the origin of the visual field range P is O and the lower left coordinate of the target board image P1 is Z, the coordinate Z (x, y) can be used as the reference position information.

  FIG. 11B shows the field-of-view range P and the target board image P2 when the positioned target board 30 is actually imaged by the imaging camera 40. FIG. The coordinates Z1 (x1, y1) of the target board image P2 are compared with the coordinates Z (x, y), and the position of the image P2 is corrected so that the difference between the two becomes zero.

  Next, a second embodiment of the present invention will be described. In the first embodiment, laser light is used for positioning the target board 30, but in the second embodiment, the target board 30 is positioned using a cross-shaped positioning member. As shown in FIG. 12, the positioning member 100 has four rod-like members 102, 104, 106, and 108 that are orthogonal to each other. The positioning member 100 is disposed at a predetermined position so that the center thereof is substantially the center of the vehicle M. The four rod-shaped members 102 to 108 each extend in the direction of the mounting position of the imaging camera, and the end portions of the four rod-shaped members 102 to 108 protrude outward from the front, rear, left and right of the vehicle M. Preferably, fitting portions for allowing the target board 30 to be freely attached and detached are formed at the end portions of the rod-shaped members 102 to 108. For example, as shown in FIG. A recess 110 is formed, and the target board 30 is formed with a protrusion 112 that fits into the recess 110.

  First, the target board 30 is attached to the end of the rod-like member 102, and in this state, the parallelism of the target board 30 and the distance from the vehicle are guaranteed. As in the first embodiment, the target board is imaged by the imaging camera, and the imaging data is stored in the memory. Next, the target board 30 is removed from the end portion of the rod-like member 102, attached to the end portion of the next rod-like member 104, picked up by the image pickup camera, and the picked-up image data is stored in the memory. Similarly, the target board 30 is sequentially attached to the rod-like members 106 and 108, and the imaging data of the target board 30 is stored in the memory. Then, electronic calibration of the imaging camera is performed using these imaging data.

  The preferred embodiment of the present invention has been described in detail above, but the present invention is not limited to the specific embodiment, and various modifications can be made within the scope of the present invention described in the claims. Deformation / change is possible.

  In the above-described embodiment, the calibration method when the imaging cameras 40a to 40d are attached to the four places on the front, rear, left, and right sides of the vehicle has been shown as an example. Can be changed as appropriate. Furthermore, in the said Example, although the irradiation apparatus 20 used the laser beam for the light source, light sources other than a laser beam like a diode may be used.

  Further, the irradiation device 20 does not necessarily include a light source for emitting laser light in all directions in which the imaging camera exists. For example, the irradiation device 20 can be rotated in one direction ( For example, the laser beam L1, L2, L3 may be irradiated toward the side surface 24).

  Furthermore, although the irradiation apparatus 20 showed the example which radiate | emits a pair of parallel laser beam L1, L3, it is also possible to radiate | emit three or more laser beams and to adjust the parallelism of the target board 30. FIG. In this case, it is desirable to form irradiation marks on the target board 30 according to the number of laser beams. Furthermore, the emitted laser beams do not need to be arranged in a straight line and may be two-dimensional.

10: Calibration system 20: Irradiation device 30: Target board 32: Base 34: Positioning unit 36: Row patterns 40a, 40b, 40c, 40d: In-vehicle imaging camera 50: Calibration device 100: Cross-shaped positioning member 102 104, 106, 108: Rod-shaped member 110: Concave portion 112: Convex portion

Claims (6)

A method for calibrating a plurality of imaging devices attached to a vehicle,
A first step of disposing an irradiation device that emits a plurality of lights at a predetermined position with respect to the vehicle;
A second step of positioning a target board for calibration using the plurality of lights with respect to an imaging device selected from a plurality of imaging devices;
A third step of imaging the target board by the selected imaging device and storing the imaging data in a memory;
A fourth step of repeating the first to third steps for each of a plurality of imaging devices;
A fifth step of performing electronic calibration of each imaging apparatus using imaging data stored in the memory;
A calibration method for an imaging apparatus including: The irradiation device emits a pair of parallel laser beams and a distance measurement laser beam emitted at a predetermined emission angle with respect to the parallel laser beams,
The target board is formed with a first mark that can be irradiated with the set of parallel laser beams and a second mark that can be irradiated with the laser beam for distance measurement,
The parallelism of the target board can be adjusted from the relationship between the set of parallel laser beams and the first mark, and the target board can be determined from the relationship between the laser beam for distance measurement and the second mark. The imaging device calibration method according to claim 1, wherein a distance between the imaging devices is adjustable. A method for calibrating a plurality of imaging devices attached to a vehicle,
A first step of disposing a positioning member having a plurality of rod-shaped members in a direction corresponding to the plurality of imaging devices at a predetermined position with respect to the vehicle;
A second step of attaching a calibration target board to a rod-shaped member corresponding to an imaging device selected from the plurality of imaging devices;
A third step of imaging the target board by the selected imaging device and storing the imaging data in a memory;
A fourth step of repeating the first to third steps for each of a plurality of imaging devices;
A fifth step of performing electronic calibration of each imaging apparatus using imaging data stored in the memory;
A calibration method for an imaging apparatus including: A system for calibrating a plurality of imaging devices attached to a vehicle,
An irradiation device that is arranged at a predetermined position with respect to the vehicle and emits a plurality of laser beams;
One movable target board for calibration of the imaging device;
Calibration means for performing electronic calibration of the imaging device based on imaging data obtained by imaging the target board,
The irradiation device emits a pair of parallel laser beams and a distance measurement laser beam emitted at a predetermined emission angle with respect to the parallel laser beams,
The target board includes a first mark that can be irradiated with the set of parallel laser beams, and a second mark that can be irradiated with the laser beam for distance measurement,
The parallelism of the target board can be adjusted from the relationship between the set of parallel laser beams and the first mark, and the target board can be determined from the relationship between the laser beam for distance measurement and the second mark. The distance between the imaging devices can be adjusted,
The calibration means causes the selected imaging device to image a target board whose parallelism and distance are adjusted, and stores imaging data of the target board in a memory.
Calibration system for imaging devices. A system for calibrating a plurality of imaging devices attached to a vehicle,
A positioning member disposed at a predetermined position with respect to the vehicle and having a plurality of rod-shaped members in a direction corresponding to the plurality of imaging devices;
A target board that is detachably attachable to a selected bar-shaped member of the plurality of bar-shaped members, and that is used for calibration of the imaging device;
Calibration means for performing electronic calibration of the imaging device based on imaging data obtained by imaging the target board,
The calibration means, when the target board is attached to the selected rod-shaped member, causes the corresponding imaging device to image the target board and stores the imaging data of the target board in the memory.
Calibration system for imaging devices. The imaging apparatus according to claim 5, wherein the positioning member has a cross shape in which rod-shaped members are orthogonal to each other, and an end portion of the rod-shaped member is provided with a fitting portion for fixing the target board. Calibration system.

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