NONCONTACT OPTICAL DISPLACEMENT MEASURING DEVICE

PURPOSE:To take an accurate measurement by providing an auxiliary measuremen system which generates a control output according to variation in measured brightness in addition to an optoelectric conversion system for displacement measurement. CONSTITUTION:The noncontact optical displacement measuring device OPT is equipped with an optical system MO for measurement, the auxiliary optical system AO for error correcting operation, and an auxiliary measuring circuit accompanying it. A target T which has a light-shade border is displaced, for example, as shown by an arrow. An image of this displaced bordr is acquired by the optical system MO. When the target T is displaced as mentioned above, an optical image on a photocathode is displaced. If a light source L varies in the quantity of light, or if disturbing light is generated, the optical system AO acquires the quantity of light from a part having no variation in brightness due to the displacement of the target T all the time and displacement measurement condition is controlled by the auxiliary measuring circuit according to variation in the quantity of light. Therefore, the optical system MO is able to intermit the displacement measurement at any time.