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Digital Multiplexed Video and Synchronization for Pulse-Stretched Signals

IP.com Disclosure Number: IPCOM000038555D
Original Publication Date: 1987-Feb-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 3 page(s) / 56K

Publishing Venue

IBM

Related People

Balliet, L: AUTHOR [+2]

Abstract

This article describes a circuit arrangement which provides compensation for pulse-width distortion while simultaneously multiplexing digital video and synchronization signals over a fiber-optic link. Presently available display systems have parallel digital interconnections that use multiple conventional wire cables to interface a (Image Omitted) controller and a display. Fig. 1 shows a typical connection for a monochrome wire cable link interfacing between a controller and a CRT display for a specific monochrome CRT. Two separate coaxial cables and one unshielded wire are used for video, horizontal sync and vertical sync, respectively. It is desirable to electrically isolate the controller and display to reduce electromagnetic interference by using cost effective fiber-optic devices and cable.

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Digital Multiplexed Video and Synchronization for Pulse-Stretched Signals

This article describes a circuit arrangement which provides compensation for pulse-width distortion while simultaneously multiplexing digital video and synchronization signals over a fiber-optic link. Presently available display systems have parallel digital interconnections that use multiple conventional wire cables to interface a

(Image Omitted)

controller and a display. Fig. 1 shows a typical connection for a monochrome wire cable link interfacing between a controller and a CRT display for a specific monochrome CRT. Two separate coaxial cables and one unshielded wire are used for video, horizontal sync and vertical sync, respectively. It is desirable to electrically isolate the controller and display to reduce electromagnetic interference by using cost effective fiber-optic devices and cable. However, characteristically many low-cost fiber-optic links reproduce pulse-stretched waveforms which affect the resolution of the video display. The circuit arrangement disclosed herein provides a solution to the pulse stretching while simultaneously multiplexing synchronization signals and providing the desired electrical isolation. Fig. 2 shows the fiber-optic interface in simplified form with multiplexed sync and distortion compensation. It consists of a dual fiber-optic connection which employs low-cost components. Each link consists of conventional drivers 1, light-emitting diodes (LEDs) 2, fiber-optic cables 3, and photo-receivers 4. The fiber links, when of short length, can be configured from visible LEDs, large plastic fiber, low-cost connectors and inexpensive receivers.

(Image Omitted)

At the controller end, the video signal 5 is fed to LINK #1 directly. LINK #2 receives the Exclusive ORed complemented (inverted) video signal 6 and the horizontal and vertical sync pulses. At the display unit, outputs of photo- receivers 4 produce pulse-stretched signals that are fed to the compensa...