| 摘要 |
PURPOSE:To reduce the movement of a measuring point in an optical axis direction which may be a cause of an error at the measurement of length down to an extremely slight distance to attain precise measurement by shifting the center of a line sensor from the optical axis of a lens. CONSTITUTION:A substance 3 to be measured such as an iron plate, paper and a composite resin plate is carried by press rollers 4, 5 and feed rollers 6, 7. In addition, rollers 8 are fitted to prevent bending. One end of a line sensor 2 in a camera 1 is made to coincide with the optical axis of a lens 1A and approximate parallel light is projected by a Fresnel lens 11. Even if (t) is changed by DELTAt, the distance (a) between the lens and the substance is not changed because the lower surface of the substance 3 to be measured is a reference, so that the magnification of the lens is not changed. The images of lower end points (q), (q') are formed on (f) and (f') points respectively and no image is formed on a point P, so that error factors can be removed. Since the approximate parallel light is used, the reflected light interrupting shadows is extremely reduced. |
