JP2017207346A - Calibration method of three-dimensional shape measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a calibration method of a three-dimensional shape measuring device capable of calibrating a camera accurately, when measuring a three-dimensional shape of a self-luminous measuring object.SOLUTION: In a three-dimensional shape measuring device including a pair of cameras 1A, 1B, for measuring a three-dimensional shape of a self-luminous measuring object by parallax of the cameras 1A, 1B, wavelength light not included in self-luminous light is irradiated to a prescribed calibration pattern, and a band-pass filter passable only by wavelength light from the calibration pattern is mounted on each camera 1A, 1B, to thereby calibrate the cameras 1A, 1B.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a calibration method for a three-dimensional shape measuring apparatus, and more particularly, to a calibration method for a measuring apparatus that includes a pair of cameras and measures a three-dimensional shape based on the parallax of these cameras.

  There is known a three-dimensional shape measuring apparatus that provides a pair of cameras (stereo cameras) on the left and right like a human eye and recognizes the three-dimensional shape from the parallax of these cameras when measuring the three-dimensional shape of a measured object. Yes. In this case, for example, as disclosed in Patent Document 1, it is often the case that a three-dimensional shape is measured by applying slit light to a measured object and projecting the slit light.

JP-A-7-91929

  By the way, in high-temperature hot steel materials and the like, the material itself emits light, and its wavelength region is often in a yellow to red region. Therefore, for example, blue slit light, which is wavelength light not included in the self-light emission, is irradiated, and only the projection image is obtained by a camera provided with a blue bandpass filter.

  In this case, calibration such as positional error adjustment between the cameras and lens distortion correction is performed by photographing a predetermined pattern such as a polka dot pattern or a lattice pattern with both cameras under natural light or a white light source. When a filter is attached, reflected light other than blue light does not enter, so the amount of light is insufficient and accurate calibration cannot be performed. Therefore, although the calibration is performed under natural light or a white light source with the bandpass filter removed, there is a problem that errors are caused by chromatic aberration due to various wavelength light contained in natural light and the like, and accurate calibration is still difficult.

  Therefore, the present invention solves such a problem, and provides a calibration method for a three-dimensional measurement apparatus that can accurately calibrate a camera when measuring the three-dimensional shape of a self-luminous object to be measured. For the purpose.

  In order to achieve the above object, the first invention includes a pair of cameras (1A, 1B), and the three-dimensional shape of the measured object (M) that emits light by the parallax of these cameras (1A, 1B). In the three-dimensional shape measuring apparatus for measuring, a bandpass filter that irradiates a predetermined calibration pattern (CP) with a wavelength light not included in the self-emission and passes only the wavelength light from the calibration pattern (CP) The cameras (1A, 1B) are calibrated by being mounted on the cameras (1A, 1B).

  In the first aspect of the invention, the calibration pattern is irradiated with the wavelength light not included in the self-emission of the object to be measured and has sufficient brightness, so that the band-pass filter allows only the wavelength light to pass through the camera. Accurate calibration can be performed even if the is mounted.

  In the second invention, the calibration pattern (CP) is formed by forming an opaque calibration pattern on a transparent substrate (21), and is not included in the self-light emission from behind the calibration pattern (CP). The wavelength light is irradiated and the wavelength light is transmitted through the calibration pattern (CP).

  In the second invention, the calibration pattern can be efficiently illuminated.

  The reference numerals in the parentheses refer to the correspondence with specific means described in the embodiments described later.

  As described above, according to the calibration method of the three-dimensional shape measuring apparatus of the present invention, the camera can be accurately calibrated when measuring the three-dimensional shape of the object to be self-luminous.

1 is a schematic perspective view of an apparatus for performing a calibration method according to an embodiment of the present invention. It is a schematic sectional drawing of the board for a calibration. It is a schematic perspective view of a three-dimensional shape measuring apparatus. It is a graph which shows a measurement error.

  The embodiment described below is merely an example, and various design improvements made by those skilled in the art without departing from the gist of the present invention are also included in the scope of the present invention.

  FIG. 1 shows an apparatus configuration when the calibration method of the present invention is performed. As shown in FIG. 1, a pair of left and right cameras 1 </ b> A and 1 </ b> B are positioned facing the calibration board 2. The cameras 1A and 1B are supported and fixed together with a line laser to be described later on a support frame (not shown). The cameras 1A and 1B do not have to be independent on the left and right sides, and may be integrated.

  The calibration board 2 has a rectangular box shape, and a calibration pattern CP is drawn on the upper surface facing the cameras 1A and 1B. In this embodiment, each camera 1A, 1B is equipped with a band-pass filter that transmits only blue. Further, in the present embodiment, the calibration pattern CP is constituted by a polka dot pattern in which a large number of small black circles are arranged at equal intervals on the left and right and up and down in a square black frame. Such a calibration pattern CP is formed by printing the frame or polka dot pattern on a transparent resin film or glass substrate 21 in black, and the black frame and small circles do not transmit light. In addition, the chain line in a figure has shown the visual field of each camera 1A, 1B.

  FIG. 2 shows a schematic sectional view of the calibration board 2. The base 21 on which the calibration pattern CP described above is formed is provided in the opening of the box 21 that opens upward on the calibration board 2 so as to close the opening. An illuminator 23 that emits blue light upward is housed in the box 22. The illuminator 23 has a large number of LEDs distributed in a plane so that blue light is output uniformly toward the upper base 21.

  When the cameras 1A and 1B are calibrated, the cameras 1A and 1B are positioned toward the board 2 above the calibration board 2 as shown in FIG. In this case, the calibration pattern CP of the calibration board 2 has sufficient brightness due to the backlight of the illuminator 23 (arrow in the figure), so that the blue band-pass filter is attached to the cameras 1A and 1B. But calibration can be done accurately.

  When measuring the three-dimensional shape of the measurement object with the cameras 1A and 1B calibrated in this way, the blue line laser 3 is positioned between the pair of cameras 1A and 1B as shown in FIG. The blue slit light SL output from the line laser 3 is projected onto the measurement object M placed on the rotary table 4 that rotates horizontally. Then, the projected shape of the slit light SL is photographed by the pair of cameras 1A and 1B, and the three-dimensional shape of the measurement object M is measured by a known method.

  FIG. 4 shows a measurement error from the actual size at each rotation angle position when the diameter of the cylindrical body shown in FIG. The measurement error when measured by the cameras 1A and 1B calibrated by the method of the present embodiment is nearly zero as shown by the line x, indicating that accurate three-dimensional shape measurement is possible.

  A line y in FIG. 4 shows a comparative example. The cameras 1A and 1B are calibrated under a white light source in a state where no bandpass filter is attached, and a blue bandpass filter is attached to the cameras 1A and 1B. The projected shape of the blue slit light in the cylindrical body M is photographed, and the diameter of the cylindrical body M is measured. In this case, a large measurement error occurs. Note that a line z in the figure calibrates the cameras 1A and 1B under a white light source without wearing a bandpass filter, and in the cylinder M with the cameras 1A and 1B without wearing a blue bandpass filter as it is. The projected shape of blue slit light is photographed, and the diameter of the cylindrical body M is measured.

  As described above, according to the calibration method of the present embodiment, accurate calibration can be performed with the blue bandpass filter attached to the camera. By projecting blue slit light not included in the light, an accurate three-dimensional shape can be measured. Of course, the wavelength light is not limited to the blue color as long as it is not included in the self-emission of the object to be measured. Moreover, illumination with respect to a calibration pattern may be performed from the front, and reflected light may be entered into a camera.

DESCRIPTION OF SYMBOLS 1A, 1B ... Camera, 2 ... Calibration board, 21 ... Board | substrate, 23 ... Illuminator, M ... Cylindrical body (measuring object), CP ... Calibration pattern.

Claims (2)

In a three-dimensional shape measuring apparatus that includes a pair of cameras and measures the three-dimensional shape of a measurement object that emits light by the parallax of these cameras, a predetermined calibration pattern is irradiated with light that is not included in the light emission. A calibration method for a three-dimensional shape measurement apparatus, wherein a band-pass filter that allows passage of only the wavelength light from the calibration pattern is attached to each camera to calibrate the cameras. The calibration pattern is formed by forming an opaque calibration pattern on a transparent substrate, and irradiates wavelength light not included in the light emission from behind the calibration pattern to transmit the wavelength light to the calibration pattern. The method for calibrating a three-dimensional shape measuring apparatus according to claim 1, wherein the three-dimensional shape measuring apparatus is calibrated.