Browse Prior Art Database

CRT Line Generation for Use With a TV Camera

IP.com Disclosure Number: IPCOM000091533D
Original Publication Date: 1968-Mar-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 3 page(s) / 51K

Publishing Venue

IBM

Related People

Cleveland, JL: AUTHOR [+2]

Abstract

When images are required to be picked up by TV camera 10 from the face of cathode ray tube CRT 12, as in drawing A, it is important that the CRT 12 traces be of sufficient thickness and brightness so that an adequate TV picture can be obtained. High-speed CRT displays present a problem in this regard because of their thin line traces and low brightness levels, as shown for example, by line B1 of drawing B.

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CRT Line Generation for Use With a TV Camera

When images are required to be picked up by TV camera 10 from the face of cathode ray tube CRT 12, as in drawing A, it is important that the CRT 12 traces be of sufficient thickness and brightness so that an adequate TV picture can be obtained. High-speed CRT displays present a problem in this regard because of their thin line traces and low brightness levels, as shown for example, by line B1 of drawing B.

One solution is to use a CRT with a high-persistence phosphor and, while the main deflection yokes 20 are being controlled to form line traces in a conventional manner, to apply appropriate magnitude 90 degrees out-of-phase sinusoidal or square-wave signals such as SX and SY in drawing C. Such signals produce results similar to sinusoidal waveforms at high frequencies when applied to the X and Y character deflection yokes 15 usually provided on high- speed displays in addition to yokes 20. The resulting CRT line trace appears as a plurality of overlapping circles as in waveform B2. The high-persistence phosphor makes the CRT line trace B2 appear to TV camera 10 as a solid line. However, this solution is not adequate for high-speed CRT displays. This is because the frequency of the 90 degrees out-of-phase SX and SY signals need to be undesirably high. Otherwise, the circles are spread apart as in waveform B3 or B4, leaving relatively large gaps.

The system in drawing A provides the resultant CRT line trace, waveform B5. The latter is obtained using the same deflection yoke signal frequency required for obtaining either of the waveforms B3 and B4. This is accomplished by providing for the generation of waveforms B3 and B4 during alternate frames so as to produce the resultant CRT trace, waveform B5.

Signal generator 32 produces the 90 d...