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Cycloreflective Holographic Sheet Data Entry Tablet

IP.com Disclosure Number: IPCOM000060127D
Original Publication Date: 1986-Mar-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 3 page(s) / 66K

Publishing Venue

IBM

Related People

Edgar, AD: AUTHOR

Abstract

A holographic data tablet is described for entering the data into a computer. The tablet is transparent, thin as a photographic film, and may be placed directly over a cathode ray tube (CRT), gas panel, projection screen or other object to take full advantage of the inherent accuracy of a holographic data tablet. The passive nature of the tablet permits the tablet's gratings to be coated on several items in the work area and used with the same stylus. The color bandwidth requirements of the tablet eliminate the need for a laser and allows an embodiment using white light. The stylus employed with the tablet may be rotated and tilted, allowing it to be handled like an ordinary pen. Fig.

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Cycloreflective Holographic Sheet Data Entry Tablet

A holographic data tablet is described for entering the data into a computer. The tablet is transparent, thin as a photographic film, and may be placed directly over a cathode ray tube (CRT), gas panel, projection screen or other object to take full advantage of the inherent accuracy of a holographic data tablet. The passive nature of the tablet permits the tablet's gratings to be coated on several items in the work area and used with the same stylus. The color bandwidth requirements of the tablet eliminate the need for a laser and allows an embodiment using white light. The stylus employed with the tablet may be rotated and tilted, allowing it to be handled like an ordinary pen. Fig. 1 illustrates the cross-section of the tablet which includes a grating 10 plus an infrared reflecting coating 11, a base 12, and an overcoat 13, as illustrated in Fig. 1. Also shown is the reflective path of an infrared beam 15, vertically impinging the surface 16. Internal grating frequency dispersion diffracts the light into uniformly wide angle, but thin, fins 20 of light, as shown in Fig. 2. The use of non-coherent,
i.e., white light would actually aid in dispersing uniformly throughout the fin 20, but would not increase its width, which is a function of the numerical aperture and aperture diffraction of the beam. Combining gratings at many angles produces an image resembling a hologram. A vertical ray diffracts into a multitude of fins, as shown in Fig. 3. Each fin 30 may be selectively activated as a function of the holographic image directly under the impingement beam. By appropriately coding the surface, the fins 20 can represent, when read in a circular sequence, bit positions in a gray binary code defining the exact X and Y coordinates of the light-struck point. All of the sensing is done above the data tablet, and, therefore, the underside is free to be in proximity with a document, display, etc. With an infrared reflecting, visible transmitting ("hot mirror") coating, the tablet will appear clear or slightly frosted to visible light, while appearing as a mirror to an infrared beam from the stylus. The holographic coding can be contact printed on a photographic glass plate for critical size tolerance accuracy, or onto a thin photographic film to be layered over documents for tracing, or...