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A Method of Checking Monitor Screens Using Photodiodes

IP.com Disclosure Number: IPCOM000060659D
Original Publication Date: 1986-Apr-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Cutshaw, RR: AUTHOR

Abstract

A technique is described whereby photodiodes are used to measure distortion, geometry, tilt, linearity, color tint and other parameters of cathode ray monitor screens. The photodiode technique eliminates the need for special cameras which may be used in checking monitor screens.

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A Method of Checking Monitor Screens Using Photodiodes

A technique is described whereby photodiodes are used to measure distortion, geometry, tilt, linearity, color tint and other parameters of cathode ray monitor screens. The photodiode technique eliminates the need for special cameras which may be used in checking monitor screens.

As a raster is generated on the monitor screen, the speed of the photodiode is such that a pulse is generated every time the scanning dot on the screen of the monitor passes a known position. By knowing when a pulse is due, the timing informa from the vertical and horizontal sync pulses, as related to the position of the photodiodes relative to the monitor screen, can be measured and recorded. The positions of the photodiodes, as shown in Fig. 1, are necessary for the measurement of distortion, linearity, geometry and tilt of a cathode ray tube and is then analyzed automatically against a preset standard.

In testing cathode ray monitor screens, photodiodes are selected with a known spectral response, along with a set of filters, and positioned in front of the monitor to be measured, as shown in the Fig. 2.

When measuring color, color tint is measured, also using a set of filters and photodiodes. Three color blocks are generated by the test equipment for display on the monitor screen. The output voltage generated by the photodiodes is compared to a known output to determine the purity of the color being tested. The luninance diode is u...