A paratus for no-contact measurement using an oscillating grating

Abstract

Abstract Apparatus for the no-contact measurement of the velocity or the path of objects without special optical markers with respect to a reference position in one or two coordinate directions, with imaging of the object onto a grating and measurement of the light flux leaving this grating means of photoelectric elements. The output signals of the photoelectric elements exhibit a frequency component proportional to the motion velocity. The grating effective as a correlator and position frequency filter is disposed in the proximity of the imaging plane of an objective and this grating is associated, per coordinate, with preferably two photoelectric receivers and the output signals of these receivers are associated with the position frequency of the grating, being in push-pull relationship to one another. The present apparatus differs from the prior art in that an electrical drive means (15) is provided for the oscillatory or continuous relative movement between the object image and grating (5'', 6, 25) and at right angles to the optical axis. In one embodiment, the grating has components which are threedimensional structures triangular in cross-section. In another embodiment, the grating has photoelectric receiver parts nested in a side-by-side relationship. In yet another embodiment the electrical drive means moves the grating in a manner having components in both measuring directions, e.g. circular or linear inclined by 45* to both coordinates. The image of the object may also be displaced relative to the grating by mobile optical means deflecting the image forming beams, e.g., by a tilted plane parallel plate or by a tilted lens rotated around the optical axis by an electric motor or by rotating or oscillating beam deflecting means as disclosed in German Patent 1 233 614 of Frenk and 1 213 141 German Published Application of Frenk.

Inventors

• 👤 K Heitmann
• 👤 E Schneider

Bibliographic Details