Premium
A high‐resolution CRT monitor using built‐in ultrasonic motors for focus adjustment
Author(s) -
Kato Kazuo,
Sase Takashi,
Sasaki Kazuyosi,
Niits Ichiro
Publication year - 1998
Publication title -
journal of the society for information display
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.578
H-Index - 52
eISSN - 1938-3657
pISSN - 1071-0922
DOI - 10.1889/1.1985213
Subject(s) - focus (optics) , computer science , phase locked loop , microprocessor , transformer , ultrasonic sensor , pulse width modulation , computer hardware , voltage , jitter , acoustics , electrical engineering , engineering , optics , physics , telecommunications
— A digitally controlled focus‐adjustment system using built‐in ultrasonic motors for high‐resolution CRT monitors has been developed. It consists of two ultrasonic‐motor‐driven potentiometers, built into a CRT flyback transformer unit, and microprocessor‐controlled driver LSI. The motor has a simplified structure with an injection‐molded plastic rotor to ensure low‐cost manufacturing. Resonant‐frequency tracking of the motor is achieved with a digital frequency‐scanning method, instead of the conventional phase‐locked loop (PLL). This ensures fast pulse‐driven control. On the manufacturing floor, a factory control unit and a CCD camera are used. A monitor incorporating the focus‐adjustment system achieved an accurate focus adjustment (less than 0.3‐mm line width) with an adjustment time of less than 10 s. This satisfied the user's focus adjustment needs.