A projection measuring instrument requiring no exchange work of overlay chart for comparatively observing a workpiece image and a template is provided. For the object, a table (56) for a workpiece (55) to be put on, an observation optical system having a screen (1) and a projection lens (53) for projecting an image of the workpiece (55) onto the screen (1), a relative movement unit (57) for relatively moving the table (56) and the observation optical system, and a displacement sensor (61) for detecting relative movement displacement by the relative movement unit (57) are provided, the screen (1) being a liquid crystal display, the liquid crystal display having a display controller (2) for displaying a line drawing for measuring a profile of the workpiece (55) onto the liquid crystal display at a predetermined magnification.
Provided is a displacement sensor which allows at least part of the data used from the time of obtaining an image until the time of computing the displacement can be readily verified. In a displacement sensor for automatically extracting a coordinate of a measuring point from an image obtained by using an imaging device according to a prescribed measuring point extraction algorithm, and computing a desired displacement from the automatically extracted measuring point coordinate, the sensor is further provided with the function to edit data used from the time of obtaining the image until the time of computing the displacement for use as display data for an image monitor.
