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CRT Line Width Magnifier

IP.com Disclosure Number: IPCOM000086798D
Original Publication Date: 1976-Oct-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Andrews, I: AUTHOR

Abstract

A special grating is described for use with a CRT display such that the qualities of the CRT focus, line spacing, line width, etc., may be readily determined by visual means.

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CRT Line Width Magnifier

A special grating is described for use with a CRT display such that the qualities of the CRT focus, line spacing, line width, etc., may be readily determined by visual means.

The grating, which consists of a series of straight parallel clear and opaque bands, is supported as a photographic, printed or similar record on either a film, plastic or glass substrate. The unit is intended to be used either hand-held or temporarily fixed to the front of the display screen by, for example, adhesive tape.

The period of the grating is made to be slightly different to that of the CRT raster, and the clear bands made much narrower than the opaque bands and, more particularly, narrower than the CRT line width. The light transmitted by the grating from a CRT screen will be the product of the two waveforms. The beat, or difference frequency, predominates and when the CRT pattern is a full close packed line block, the resultant effect is that the line width appears magnified by a reciprocal of the relative difference frequency. (A 10% frequency difference gives a magnification of 100X.)

When used with a CRT unit having a thick protective glass front, resolution is improved if the grid is mounted on a fiber-optic faceplate. In this case the fiber- optic plate ensures that only light direct from the required CRT line reaches the grating.

The figure shows the distribution of light from a CRT screen. ]The pattern will appear as a virtually continuous waveform...