Computer graphics processing and selective visual display system – Display peripheral interface input device – Stylus
Patent
1997-04-16
1999-04-13
Shankar, Vijay
Computer graphics processing and selective visual display system
Display peripheral interface input device
Stylus
345 87, 345102, 345104, 345183, 178 181, 178 1811, G08C 2100, G09G 336, G09G 500
Patent
active
058943048
ABSTRACT:
A pen input apparatus includes an inversion signal generation circuit for generating an inversion signal to invert the direction of applied voltage to liquid crystal of a liquid crystal panel. There is a first conversion circuit to detect a voltage induced at a detection pen according to the inversion signal generated by the inversion signal generation circuit for converting the induced voltage into a direct-current voltage. A comparator circuit is included for comparing a voltage value of the direct-current voltage converted by the first conversion circuit with a predetermined value to determine whether the detection pen is close to the liquid crystal panel. A detection period signal generation circuit is used for turning on a back light of the liquid crystal panel when the first conversion circuit is not detecting an induced voltage, and for turning off the back light when the first conversion circuit is detecting an induced voltage.
REFERENCES:
patent: 4958915 (1990-09-01), Okada et al.
patent: 5065357 (1991-11-01), Shiraishi
patent: 5078476 (1992-01-01), Shin
patent: 5247286 (1993-09-01), Ishikawa
patent: 5410329 (1995-04-01), Tagawa
patent: 5589848 (1996-12-01), Shimizu
Shankar Vijay
Sharp Kabushiki Kaisha
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