| 摘要 |
PROBLEM TO BE SOLVED: To accurately find a pixel rate even when a position is shifted, by recognizing a target with a camera by relatively moving the camera for the circular target, detecting the number of pixels in a diameter direction of the target, and calculating the pixel rate from a ratio of the number of pixels to the diameter of the target. SOLUTION: A coordinate system (x, y) of a camera 11 is shifted from a reference coordinate system (X, Y) by Δθ in a rotational direction. Dt is a diameter of a target 10. Here, a pixel number Nx in the X direction and a pixel number Ny in the Y direction are found. Then a pixel rate Dt/Nx in the X direction and a pixel rate Dt/Ny in the Y direction are calculated from the diameter Dt of the target 10, and stored in a storage part. Thereby a pixel rate is decided. The image of the target 10 is circular, so that there is no directional property in the form thereof. Thereby, even when a photodetecting element 13 of the camera 11 and the target 10 are shifted in position in a θ direction, an accurate pixel number is detected. |
