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Proceedings Paper

Fast optical distance measurement by analysis of the focus of a holographic lens
Author(s): Johannes K. Schaller; Ernst Ulrich Wagemann; Christo G. Stojanoff
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Paper Abstract

An implementation of an optical distance measuring system by commercially available electro-optical products was tested experimentally. The system utilizes the spatial dependence of the intensity distribution in an astigmatic focus of a lens system on the distance from the latter. The system can either be used for fast distance measurements with a resolution of 1 in 500 or alternatively for position control with sub-micron resolution. The spatial intensity distribution was determined utilizing a four-quadrant silicon detector. The amplified signal was digitized and read into a PC for evaluation. A holographic lens was used as astigmatic element. A holographic lens has the advantage of easy control of the astigmatisms and the possibility of rescaling to suit the designed measuring range. Furthermore, a holographic lens can be used in an off axis arrangement with simultaneous suppression of comatic aberrations. The best recording geometry for the holographic lens was found by computer simulation. The four quadrants of the detector are arranged such that two detector elements are illustrated by either of the two astigmatic line foci. The detector was moved through the focal region. The intensity is shifted from one quadrant pair in the first focal plane to all detectors in the lane of least confusion and finally to the other quadrant pair in the second focal plane. The difference of the photo currents of the quadrant pairs is a measure for the distance from the holographic lens.

Paper Details

Date Published: 18 September 1996
PDF: 8 pages
Proc. SPIE 2782, Optical Inspection and Micromeasurements, (18 September 1996); doi: 10.1117/12.250745
Show Author Affiliations
Johannes K. Schaller, Technical Univ. Aachen (Germany)
Ernst Ulrich Wagemann, Technical Univ. Aachen (Germany)
Christo G. Stojanoff, Technical Univ. Aachen (Germany)

Published in SPIE Proceedings Vol. 2782:
Optical Inspection and Micromeasurements
Christophe Gorecki, Editor(s)

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