Browse Prior Art Database

Optical Test Head with Flare Compensation

IP.com Disclosure Number: IPCOM000050475D
Original Publication Date: 1982-Nov-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Ruppert, W: AUTHOR

Abstract

The output signal of a photodetector arrangement in an optical sensing head is corrected for flare, using a further photodetector arranged in the optical head in such a manner that it receives scattered light from all flare-contributory sources.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 99% of the total text.

Page 1 of 2

Optical Test Head with Flare Compensation

The output signal of a photodetector arrangement in an optical sensing head is corrected for flare, using a further photodetector arranged in the optical head in such a manner that it receives scattered light from all flare-contributory sources.

In Fig. 1, a photodiode 2 is introduced into the bottom half of optical sensing head 1 so that it cannot be reached by any direct ray in the beams forming the image of object plane 3 on photodetector array 5 through lens 4.

Photodiode 2 thus measures direct flare 9a (caused, for example, by ray 7 impinging on prestop 6), lens flare 9b (in objective 4) and indirect flare 9c (emanating, for example, from wall positions 8a, 8b where flare is caused by previously scattered rays).

In the circuit of Fig. 2, the output signal of photodiode 2 is applied to differential amplifier 20 through potentiometer 21 and inverter 22 to be subtracted from the output signal of photodetector array 5; the output of amplifier 20 represents the flare-compensated signal.

In good optical systems, the contribution of flare to the output signal of photodetector array 5 is uniform in a first approximation, so that the subtraction of a signal generated by indirect light considerably improves the image quality; this flare compensation can be used, in addition to other known methods, to reduce the influence of flare (e.g., blackening of walls, etc.).

1

Page 2 of 2

2

[This page contains 3 pictures or other non-tex...