Browse Prior Art Database

Position Detection on Static Displays

IP.com Disclosure Number: IPCOM000046661D
Original Publication Date: 1983-Aug-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Dias, W: AUTHOR

Abstract

So-called light pens (hand-held photo receptors) have long been in wide use with respect to CRT displays. The usual method of operation is by time coincidence between instantaneous illumination of a spot on the CRT screen by the flying CRT beam and the position of data in a regeneration buffer which drives the display. This method cannot be used directly with static displays, such as liquid crystal or plasma panel displays. Described here is a system which overcomes this problem. The system has three key parts. The first part is the probe. The probe is similar to the one used for CRTs, except the optics and light sensor are matched to the display. The second is the image backup RAM (random-access memory). The last part is the unique circuitry that controls the scan.

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Position Detection on Static Displays

So-called light pens (hand-held photo receptors) have long been in wide use with respect to CRT displays. The usual method of operation is by time coincidence between instantaneous illumination of a spot on the CRT screen by the flying CRT beam and the position of data in a regeneration buffer which drives the display. This method cannot be used directly with static displays, such as liquid crystal or plasma panel displays. Described here is a system which overcomes this problem. The system has three key parts. The first part is the probe. The probe is similar to the one used for CRTs, except the optics and light sensor are matched to the display. The second is the image backup RAM (random-access memory). The last part is the unique circuitry that controls the scan. Operation Phase 1: When the operator wishes to identify a field on the screen, he places the probe 10 on the display 12 and presses a switch on the probe to activate the control circuits. Using the data contained in the backup RAM 14, the control circuits will begin erasing and rewriting the display. Detection by the probe of a change on the display will signal that the chosen block has been located. This locates the display block containing the point of interest and ends phase 1. Phase 2: In phase 2 the control circuits will erase all, but rewrite only part of the block. When the pen detects a change, the control circuits will divide the area of the display last...