Browse Prior Art Database

Light Pen Tracking System

IP.com Disclosure Number: IPCOM000094440D
Original Publication Date: 1965-Jan-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Triest, WE: AUTHOR

Abstract

In an arrangement for line tracking on a CRT under control of a light transducer such as a light pen, a circular marker spot generated on the face of a CRT is divided into eight identical time slots T0... T7. When the light pen is held with its axis perpendicular to the face of the CRT, the resulting output signal during the time the marker spot is being retraced is a function of the position of the axis of the light pen with respect to the center of the circle. For the axis of the light pen at any position except on the center of the circle, an output voltage is derived from the pickup which has a maximum value at the time when the spot is closest to it.

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Light Pen Tracking System

In an arrangement for line tracking on a CRT under control of a light transducer such as a light pen, a circular marker spot generated on the face of a CRT is divided into eight identical time slots T0... T7. When the light pen is held with its axis perpendicular to the face of the CRT, the resulting output signal during the time the marker spot is being retraced is a function of the position of the axis of the light pen with respect to the center of the circle. For the axis of the light pen at any position except on the center of the circle, an output voltage is derived from the pickup which has a maximum value at the time when the spot is closest to it.

This voltage signal is correlated with a corresponding time slot and appropriate corrective signals are generated to move the circle in a direction corresponding to the axis of the light pen. In the upper drawing, a plurality of And's 21...28 is conditioned by time sequence signals generated by conventional gating techniques. And 21 is conditioned by the T0 gate, And 22 by the T1 gate, etc.

When the photo pickup output signal is applied through line 29 to simultaneously strobe all And's 21... 28, only the particular And which is conditioned at this time generates an output. This is indicative of the location of the spot with respect to the eight timing segments of the circle. This output signal is then applied as a correction signal to the appropriate X or Y deflection so that the marke...