Browse Prior Art Database

Electrooptic Input Tablet

IP.com Disclosure Number: IPCOM000079322D
Original Publication Date: 1973-Jun-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Keyes, RW: AUTHOR

Abstract

This description relates to a device for electrooptically sensing the position of a sensing probe. The physical structure of the device is shown in Fig. 1. The probe 10 contains a light sensor. The device also includes a tablet which consists of a light source 12 and a working surface 14 separated by a moveable mask 16. The working surface 14 is divided into alternating transparent and opaque strips, as shown in Fig. 2. The mask 16 is also divided into alternating transparent and opaque strips, but with a periodicity slightly different from that of the working surface as indicated.

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Electrooptic Input Tablet

This description relates to a device for electrooptically sensing the position of a sensing probe. The physical structure of the device is shown in Fig. 1. The probe 10 contains a light sensor.

The device also includes a tablet which consists of a light source 12 and a working surface 14 separated by a moveable mask 16. The working surface 14 is divided into alternating transparent and opaque strips, as shown in Fig. 2. The mask 16 is also divided into alternating transparent and opaque strips, but with a periodicity slightly different from that of the working surface as indicated. If the mask 16 has one more period than the working surface 14, there will be one region of the surface where the transparent strips of the working surface 14 and the mask 16 are in registration, and a maximum amount of light is transmitted upward through the structure.

When the mask 16 is moved, the region of registration will move, at a rate much faster than the physical speed of the mask 16. Moving the mask 16 one period will move the registration position across the tablet. When the registration position passes the probe 10, a maximum amount of light will reach the photosensor within probe 10. Since the position of registration bears a known relation to the position of the mask 16, the reading of the mask position sensor at this time will yield the position of the probe in one direction.

One method of determining the position of the probe 10 in the second direction is to superimpose another set of opaque stripes at an angle to the first set, so that the registration region slants across the tablet as shown in Fig. 3. Opaque here is defined to mean opaque i...