JP2013024803A - Calibration device and calibration system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow photography of pattern images that are targeted when calibration of a photography device is performed to be easily carried out.SOLUTION: In the calibration device 2, a pattern part 11 where an LED is fixed and supported to a bottom part of a light emitting part 12 and which forms a pattern image 17 on a diffuser 16 is integrally formed with a support body so as to close an opening of the support body with a surface on the side of a pattern image 17 outside. Multistage adjustment of brightness of LED is performed. When brightness of the LED determined according to the pattern image 17 photographed by the photography device is not within a preset range, control is performed so that the brightness is adjusted so as to be within the range and then photography is performed again by the photography device.

Description

  The present invention relates to a calibration apparatus and a calibration system used for calibration of a photographing apparatus such as a CCD camera.

  A technique is known in which an object is photographed with a camera and the position, posture, shape, and the like of the object are measured from the image. When measuring the position and orientation of an object with a known model shape using a single camera, or when performing stereo measurement or three-dimensional measurement using multiple cameras, the internal characteristics that represent the physical characteristics of the camera Parameters (lens focal length, optical axis center, lens distortion, etc.), camera mounting positions and orientations, and external parameters indicating correspondence between multiple cameras are acquired in advance by calibration. There is a need.

Non-Patent Document 1 discloses a typical technique for calibration. This method uses a target on a plane whose actual dimension has a known three-dimensional coordinate value, arbitrarily changes the position and orientation of the target, shoots an image at that time, and uses this image as a two-dimensional feature point. A coordinate value is extracted, and an internal parameter and an external parameter of the camera are estimated by a least square method from a set of this and a corresponding known three-dimensional coordinate value. At this time, theoretically, parameters can be estimated if the target posture is three patterns, but in practice, it is necessary to acquire an image with ten to several tens of postures.
Patent Document 1 discloses a calibration apparatus in which a calibration pattern is formed on the upper surface of a transparent substrate, and illumination means is disposed below the transparent substrate.

JP 10-104033 A

Zhengyou Zhang, “Flexible Camera Calibration by Viewing a Plane from Unknown Orientations”, International Conference on Computer Vision, 1999, pp.666-673

  In the technique of Non-Patent Document 1, it is necessary to capture all images of targets with different postures clearly and surely, but the lighting method is devised so that the images are clear even when the target is changed in various directions. Necessary. In other words, in an experimental facility where lighting cannot be easily installed, outdoors, or in environments where there are structures in the surroundings, it is impossible to illuminate from all directions, so clear images cannot be taken and calibration can be performed as a result. It will disappear.

  On the other hand, in the technique of Patent Document 1, the calibration pattern is formed on the upper surface of the transparent substrate, and the illumination means is disposed below the transparent substrate. Therefore, the target pattern can be easily illuminated. Even if it is in an experimental facility that cannot be installed in the environment, or in an environment where there are structures in the surroundings, the pattern will be well illuminated by the lighting regardless of the direction, and a clear image will be taken be able to.

However, in such a technique, it is necessary to adjust the illumination position so that the position of the illumination is optimized every time the posture of the pattern image as a target is changed, and there is a problem that the target photographing operation at the time of calibration is complicated.
An object of the present invention is to facilitate the photographing operation of a pattern image which is a target at the time of calibration of the photographing apparatus.

  (1) In one embodiment of the present invention, in a calibration apparatus provided with a pattern image for calibration of an imaging apparatus that captures an image, a support body that houses and supports the light sources, and A translucent diffusion plate integrally formed with the support on the light irradiation side of the support from the light source, and the pattern image is formed on the light irradiation side of the diffusion plate. It is the calibration apparatus characterized by this.

(2) In this case, the brightness of the light source may be adjustable.
(3) According to another embodiment of the present invention, the brightness of the light source determined from the image capturing device that captures an image, the calibration device according to (2), and the pattern image captured by the image capturing device. And a control means for performing control to perform photographing again with the photographing device after adjusting the brightness so that the photographing device is within the predetermined range. System.

  According to the invention of (1), the support for supporting the light source and the diffusion plate are integrally formed, and the pattern image for the calibration target is formed on the light irradiation side of the diffusion plate. If the pattern image is positioned at the time of photographing, the position of the light source is determined, and the pattern image photographing work can be facilitated.

According to the invention of (2), the illumination of the pattern image can be adjusted according to the ambient brightness.
According to the invention of (3), the pattern image can be photographed with the optimum brightness according to the ambient brightness.

1 is a block diagram illustrating an overall configuration of a calibration system according to an embodiment of the present invention. It is a perspective view of the calibration apparatus in the calibration system which is one embodiment of the present invention. It is a longitudinal cross-sectional view of the light emission part of the calibration apparatus in the calibration system which is one embodiment of this invention. It is a block diagram which shows the electrical connection of the calibration system which is one embodiment of this invention. It is a functional block diagram explaining the calibration process which CPU in the calibration system which is one embodiment of this invention performs based on a program. It is a flowchart explaining the calibration process which CPU in the calibration system which is one embodiment of this invention performs based on a program. It is explanatory drawing which shows the example of the image image | photographed by changing the attitude | position of a pattern image variously in the state which turned off LED in the calibration system which is one embodiment of this invention. It is explanatory drawing which shows the example of the image image | photographed by changing the attitude | position of a pattern image variously in the state which lighted LED in the calibration system which is one embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing an overall configuration of a calibration system 1 according to an embodiment of the present invention. The calibration system 1 is connected to a calibration device 2, a photographing device 3 composed of a CCD camera or the like, a calibration device 2 and a photographing device 3, and a control unit 4 that controls the calibration device 2 and the photographing device 3. And.

  FIG. 2 is a perspective view of the calibration device 2. The calibration device 2 is roughly divided into a pattern unit 11 and a light emitting unit 12. FIG. 3 is a longitudinal sectional view of the light emitting unit 12. The light emitting unit 12 includes a support 13 that is a box having an upper surface opened. One or a plurality of light sources are provided on the inner bottom of the support 13. In this example, a plurality of light emitting diodes (LEDs) 14 as light sources are arranged and fixedly supported on one surface of the inner bottom portion of the light emitting unit 12. Thus, when the LED 14 is caused to emit light, the light is irradiated to the outside from the opening 15 of the support 13.

  The pattern unit 11 includes a translucent diffusion plate 16 and a pattern image 17 formed on one surface of the diffusion plate 16. The pattern image 17 is an image serving as a target used when the image capturing apparatus 3 is calibrated, and is an image in which white and black rectangular shapes appear alternately and continuously. The pattern image 17 can be formed by printing on one surface of the diffusion plate 16. In addition, a sheet or the like on which the pattern image 17 is formed can be attached to one surface of the diffusion plate 16. The pattern portion 11 in which the pattern image 17 is formed on the diffusion plate 16 is formed integrally with the support 13 so as to close the opening 15 of the support 13 with the surface on the pattern image 17 side facing outside.

FIG. 4 is a block diagram showing the electrical connection of the control system of the calibration system 1. In this control system, a CPU 21 that performs various calculations and centrally controls each unit, a ROM 22 that stores various programs executed by the CPU 21 and fixed data, and a RAM 23 that is a work area of the CPU 21 are connected by a bus 24. ing. Furthermore, the imaging device 3 is connected to the bus 24 via a drive circuit 25 that drives and controls the imaging device 3. Further, the LED 14 is connected via a lighting circuit 26 that drives and controls the LED 14. Further, a magnetic storage device 27 is connected to the bus 24 via a predetermined interface.
FIG. 5 is a functional block diagram for explaining calibration processing executed by the CPU 21 based on a program. FIG. 6 is a flowchart for explaining a calibration process executed by the CPU 21 based on a program.

  In order to calibrate the photographing apparatus 3, the photographing apparatus 3 and the calibration apparatus 2 are arranged at predetermined positions so that the pattern image 17 can be photographed by the photographing apparatus 3. First, the pattern image 17 is photographed by the photographing device 3 (step S1). The captured image is recorded in the image recording unit 31. The image recording unit 31 is prepared in the magnetic storage device 27 and the like. Then, it is determined from the image data after photographing whether the brightness of the LED 14 is within a predetermined range (step S2). When the brightness is not within the predetermined range (N in Step S2), the brightness of the LED 14 is adjusted (Step S3), and the process returns to Step S1 to capture the pattern image 17 again. That is, the brightness of the LED 14 can be adjusted in multiple stages, for example. And if the brightness | luminance of LED14 exceeds the upper limit of the predetermined range, it will darken one step from the present brightness, and will return to step S1. If the brightness of the LED 14 is below the lower limit of the predetermined range, the brightness is increased by one step from the current brightness, and the process returns to step S1. The adjustment of the brightness of the LED 14 is performed by the illumination control unit 32.

  When the brightness of the LED 14 is within a predetermined range (Y in step S2), the two-dimensional coordinate value of the feature point is extracted from the captured image (step S4). Here, the feature points are the intersections of the rectangular shapes in the image in which the white and black rectangular shapes in the pattern image 17 are continuous. This coordinate value extraction is performed by the image coordinate extraction unit 33. For calibration, it is necessary to take a plurality of images by changing the orientation of the pattern image 17 in various ways. Therefore, it is determined whether or not all of the set number of images have been shot (step S5). If all the shots have been taken (Y in step S5), the process proceeds to step S6. If there is shooting that has not been completed yet (N in step S5), the process returns to step S1 to perform shooting. It should be noted that this shooting needs to be performed by changing the posture of the pattern image 17, that is, the calibration device 2.

  In step S6, parameters are calculated. That is, the parameter calculation unit 34 calculates a parameter by a least square method from a set of the two-dimensional coordinate value of the image extracted in step S4 and the three-dimensional coordinate value of each feature point stored in advance in the storage unit 35. . The storage unit 35 is prepared in the magnetic storage device 27 and the like. Since more detailed calculation of these parameters is well known, detailed description is omitted.

  According to the calibration system 1 described above, the pattern image 17 is illuminated by the LED 14. In addition, since the diffusion plate 16 is used, the pattern image 17 is illuminated uniformly. Therefore, even in an experimental facility where lighting cannot be easily installed, outdoors, or in an environment where there are structures in the surroundings, the pattern image 17 can be illuminated evenly regardless of the posture, and the pattern image is always displayed. 17 clear images can be taken and calibration can be performed.

FIG. 7 is an explanatory diagram illustrating an example of an image captured by changing the posture of the pattern image 17 with the LED 14 turned off. It can be seen that the photographed image becomes unclear depending on the posture of the pattern image 17.
FIG. 8 is an explanatory diagram illustrating an example of an image captured by changing the posture of the pattern image 17 in a state where the LED 14 is turned on. It can be seen that each image taken is clear regardless of the posture of the pattern image 17.

  Further, in the calibration device 2, the LED 14 is fixedly supported on the inner bottom portion of the light emitting unit 12, and the pattern unit 11 in which the pattern image 17 is formed on the diffusion plate 16 has the surface on the pattern image 17 side facing outside. It is formed integrally with the support 13 so as to close the opening 15. Therefore, when the posture of the pattern image 17 is changed, it is not necessary to adjust the position of the LED 14 according to the change. If the posture of the pattern image 17 is changed by moving the calibration device 2 together, the pattern image 17 is changed. And the positional relationship between the LEDs 14 are also maintained. For this reason, it is possible to easily shoot the pattern image 17.

Moreover, since the brightness of LED14 can be adjusted, the illumination of the pattern image 17 can be adjusted according to the surrounding brightness.
Further, it is determined whether or not the brightness of the LED 14 is within a predetermined range from the image data after shooting (step S2), and when the brightness is not within the predetermined range (step S2). N), the brightness of the LED 14 is adjusted (step S3), and control is performed to return to the step S1 to capture the pattern image 17 again. Therefore, the pattern image 17 is captured with the optimum brightness according to the ambient brightness. can do.

DESCRIPTION OF SYMBOLS 1 Calibration system 2 Calibration apparatus 3 Image pick-up apparatus 11 Pattern part 12 Light emission part 13 Support body 14 LED
15 Opening 16 Diffuser

Claims (3)

In a calibration device provided with a pattern image for calibration of a photographing device for photographing an image,
One or more light sources;
A support that houses and supports the light source;
A translucent diffuser plate formed integrally with the support on the light irradiation side of the support from the light source;
With
The pattern image is formed on the light irradiation side of the diffusion plate,
A calibration apparatus characterized by that.   The calibration apparatus according to claim 1, wherein brightness of the light source is adjustable. A photographing device for photographing images;
A calibration device according to claim 2;
When the brightness of the light source determined from the pattern image photographed by the photographing device is not within a preset range, the brightness is adjusted to be within the range, and then the photographing device is again Control means for performing control of shooting with,
A calibration system characterized by comprising: