Browse Prior Art Database

Intensity Falloff Corrector

IP.com Disclosure Number: IPCOM000095794D
Original Publication Date: 1964-Jul-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Lazrzchick, N: AUTHOR

Abstract

In a recording system in which the CRT flying spot is used to record on film, deflection of the beam off its optical axis produces a light loss or intensity falloff at the edge of the CRT, resulting in lower density of the film at these points when the image is recorded. As the light varies from its optical axis, it is attenuated by cos40, where 0 is the angle from the center of the screen to the end point of the vector being drawn.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 71% of the total text.

Page 1 of 2

Intensity Falloff Corrector

In a recording system in which the CRT flying spot is used to record on film, deflection of the beam off its optical axis produces a light loss or intensity falloff at the edge of the CRT, resulting in lower density of the film at these points when the image is recorded. As the light varies from its optical axis, it is attenuated by cos40, where 0 is the angle from the center of the screen to the end point of the vector being drawn.

To maintain uniform light intensity of the entire surface of the CRT, a correction circuit provides intensity compensation for each display quadrant. A parabolic signal representing the radial distance of the spot from the center of the CRT is applied from the focus circuitry to input terminal 11. This is connected through an attenuating network to base 13 of transistor 15. Potentiometer 17, empirically set as a function of the film density, controls the signal level where additional intensity compensation will begin. The output of potentiometer 17 is connected through clamping diode 19 to the bases of transistors 23A... 23D. Terminals 21A... 21D are connected to digital input signals.

These are controlled in accordance with the particular quadrant in which the beam is positioned such that one of associated transistors 23 is turned on, while the amount of compensation to be provided is individually adjusted for each quadrant by potentiometers 25A ... 25D. The output signal on line 27 resulting from conducti...