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Optical Funnel for Light Pen

IP.com Disclosure Number: IPCOM000091164D
Original Publication Date: 1969-Nov-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Gray, RG: AUTHOR

Abstract

The light pen, utilized for light detection from a cathode ray tube phosphor, is constructed without the normal optical lens system. This light pen comprises an optical tunnel which pipes light at grazing angles and absorbs or totally reflects light from large angles. The light tunnel comprises exterior tubular shield 1 which is painted or coated with an opaque material to prevent light transmission. Interior truncated cone 2 is employed to accommodate the specified detection area on the one hand and the effective aperture of the photodetector on the other. The larger diameter is on the face plate side and the smaller diameter of the photodetector aperture on the other. The inner core of the light pen can be a conventional cylinder or a cone truncated in the opposite direction depending on design parameters.

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Optical Funnel for Light Pen

The light pen, utilized for light detection from a cathode ray tube phosphor, is constructed without the normal optical lens system. This light pen comprises an optical tunnel which pipes light at grazing angles and absorbs or totally reflects light from large angles. The light tunnel comprises exterior tubular shield 1 which is painted or coated with an opaque material to prevent light transmission. Interior truncated cone 2 is employed to accommodate the specified detection area on the one hand and the effective aperture of the photodetector on the other. The larger diameter is on the face plate side and the smaller diameter of the photodetector aperture on the other. The inner core of the light pen can be a conventional cylinder or a cone truncated in the opposite direction depending on design parameters. Light emitted from a CRT area in the field of view can be isolated from light emitted from adjacent areas since light tunnel core 4 is either touching face plate 5 of the CRT or positioned immediately adjacent to it. The field of view of the light pen can be varied by changing either the tunnel diameter or the tunnel length or both. Core 4 is made of glass, clear plastic, air or any conventional transparent material adapted to permit the passage of the detected light. The light detecting housing can be fitted with interchangeable tunnels of varying diameters to realize field of view variations and allow CRT faceplate thickness var...