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FIBER OPTIC FACEPLATE COUPLER FOR IMAGE BAR APPLICATION - LIQUID CRYSTAL IMAGE BAR PROJECT

IP.com Disclosure Number: IPCOM000025746D
Original Publication Date: 1987-Oct-31
Included in the Prior Art Database: 2004-Apr-04
Document File: 4 page(s) / 260K

Publishing Venue

Xerox Disclosure Journal

Abstract

The design of shutter or gate-array type image bars which incorporate Lambertian sources is usually complicated by the conflicting requirements of high radiant coupling efficiency between the light source and the gate-array and thermal isolation of the hot source from the gate-array. In order to obtain maximum irradiance at the gate-array image plane, one would like to place the lamp as close as possible to the gate-array. On the other hand, the proximity of the lamp to the array many times results in degraded performance characteristics of the array due to the elevated lamp temperature. One possible solution that has been used in the past is to employ a "critical illumination" scheme whereby a lens is used to image the source onto the gate-array. In the case of an extended linear source and gate-array, both linear SELFOC lenses, and cylinder lenses have been proposed. Although these methods work, there are drawbacks such as expense, difficulty in proper alignment, insufficient numerical aperture (hence low coupling efficiency), Fresnel loss problems, or "bow-tie" blurring effects (i.e., in the case of the cylinder lens).

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Page 1 of 4

XEROX DISCLOSURE JOURNAL

FIBER OPTIC FACEPLATE Proposed Classification COUPLER FOR IMAGE BAR
APPLICATION
- LIQUID CRYSTAL
IMAGE BAR PROJECT
Joseph F. Revelli, Jr.

Joel M. Pollack Frank C. Genovese

U.S. C1.355/3R Int. C1. G03G 15/00

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FIG. I lo

FIG. 2

FIG. 3

Volume 12 Number 5 September/October 1987

225

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Page 2 of 4

FIBER OPTIC FACEPLATE COUPLER FOR IMAGE BAR APPLICATION - LIQUID CRYSTAL IMAGE BAR PROJECT (Cont'd)

The design of shutter or gate-array type image bars which incorporate Lambertian sources is usually complicated by the conflicting requirements of high radiant coupling efficiency between the light source and the gate-array and thermal isolation of the hot source from the gate-array. In order to obtain maximum irradiance at the gate-array image plane, one would like to place the lamp as close as possible to the gate-array. On the other hand, the proximity of the lamp to the array many times results in degraded performance characteristics of the array due to the elevated lamp temperature. One possible solution that has been used in the past is to employ a "critical illumination" scheme whereby a lens is used to image the source onto the gate-array. In the case of an extended linear source and gate-array, both linear SELFOC lenses, and cylinder lenses have been proposed. Although these methods work, there are drawbacks such as expense, difficulty in proper alignment, insufficient numerical aperture (hence low coupling efficiency), Fresnel loss problems, or "bow-tie" blurring effects (i.e., in the case of the cylinder lens).

Still another scheme has been proposed for the case where a point source is used to illuminate an extended linear array. Optical fibers are positioned all about a point source (a tungsten halogen lamp, for exam le) to capture the

opposite ends of these fibers are arranged in a linear array and butted against the linear light gate array. This solution accomplishes two things at once. First of all, it converts a point source into a linear source. Secondly, it efficiently captures the light from the point source and transmits it to the gate-array with little loss while allowing physical separation of the source and the array. The disadvantages are that it is very bulky and difficult to fabricate.

P solid angle. The

Disclosed herein is the use of a longitudinally cut fiber optic faceplate 10 (LFOF) as an extremely efficient, inexpensive coupler between an extended linear light source 12 and gate array 14. The LFOF is placed in between the light source and the linear gate-array as shown in Fig. 1 with the axes of the fibers aligned with the optical axis of the system. Such an arrangement has several distinct advantages over previously cited methods. First of all, the numerical aperture of the individual fibers comprising the faceplate is quite high resulting in efficient capture of the light radiated from the source. In fact, the numerical apertu...