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Structured Lighting for Vidicon Camera Inspection

IP.com Disclosure Number: IPCOM000040374D
Original Publication Date: 1987-Nov-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Clearman, MR: AUTHOR [+3]

Abstract

A method which eliminates desensitization ("fatigue" or "burn-in") of phosphorus on vidicon camera tubes without the use of moving elements is described. High resolution video camera inspection many times necessitates the use of vidicon cameras. An inherent problem with the use of this type of analog camera in an inspection application is image drift. This drift can be caused by such external factors as temperature and power supply voltage. The drift can be compensated for by calibrating often. When calibrating often, the calibration target can be mounted directly behind the sample to be inspected. Because the sample and the target have the same image, the only change in the camera view is the small error in each sample. This image is focused on the phosphorus constantly.

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Structured Lighting for Vidicon Camera Inspection

A method which eliminates desensitization ("fatigue" or "burn-in") of phosphorus on vidicon camera tubes without the use of moving elements is described. High resolution video camera inspection many times necessitates the use of vidicon cameras. An inherent problem with the use of this type of analog camera in an inspection application is image drift. This drift can be caused by such external factors as temperature and power supply voltage. The drift can be compensated for by calibrating often. When calibrating often, the calibration target can be mounted directly behind the sample to be inspected. Because the sample and the target have the same image, the only change in the camera view is the small error in each sample. This image is focused on the phosphorus constantly. Even if auxiliary lighting is used during inspection, ambient light will focus the image on the phosphurus tube while the system is idle. In time the phosphorus will become desensitized ("fatigued" or "burned-in"). Conventional solutions are to install shutters at the camera lenses and to move or cover the calibration target when not in use. Both of these methods require moving elements. The vidicon cameras can be protected without the use of moving elements using structured lighting during inspection. The structured lighting should be at the opposite end of the spectrum with respect to the ambient lighting. Filters at the camera lens will only p...