| 摘要 |
PURPOSE:To detect a defect which can not be detected by a differentiating method by comparing the mean value of light quantity values of a target picture element and its circumferential picture elements with the light quantity value of the target picture element as to a surface to be inspected on which the quantity of reflected light from a normal part varies continuously. CONSTITUTION:The quantity of reflected light photodetected by an image pickup element 1 such as a telecamera is converted into an electric signal and the analog signal from the element 1 is converted into an 8-bit digital signal by an A/D conversion part 2. Then, the shift register 31 of a defect detection part 3 is stored with the current light quantity value and last light quantity values of (n) picture elements, a mean value calculating circuit 32 calculates a mean optical value from the light quantity values of (n+1) picture elements, and a comparator 33 compares the current light quantity value with the mean light quantity value. When the comparison value exceeds a set threshold value, a conforming/noncomforming decision part 4 decides that the current picture element is a defective and generates a defect signal. |
