High Speed Measurement of Color CRT Beam Profile and its Application to Focus Evaluation

Abstract

This paper presents a method for measuring and evaluating electron beam profiles of high resolution color CRTs in high speed. The system has a two-dimensional sensor to get the intensity data of an electron beam. The magnetic field is applied from the front panel side to shift the electron beam, and used to get the intensity data of the electron beam which is blocked by the shadow-mask. In this system, electron beam profiles (6 points×3 colors) can be measured within 10 minutes for each CRT. The beam profiles are then used to evaluate beam focusing grade. Some parameters (beam area, diameter, vertical and horizontal ratio etc.) are calculated to characterize beam profiles. Human evaluation was executed by a skillful inspector, who judged the beam focusing grade by the readability of character patterns on CRT screens. As a result, we found that two segmented areas' values (3% and 30% of profile intensity maximum) which represent a halo characteristics and a core size, respectively, have strong relations to human evaluation results.