Coordinate input apparatus

Details Coordinate input apparatus Coordinate input apparatus

1995-07-27

1997-11-04

Kuntz, Curtis

Telegraphy

Systems

Position coordinate determination for writing

178 19, 345177, 345179, G08C 2100, G09G 302

Patent

active

056842775

ABSTRACT:
A coordinate input apparatus which can attain an accurate coordinate input operation, includes a sensor for detecting an input variation. The vibration is amplified, and an envelope detection circuit generates the envelope of the amplified vibration. A gate signal generation circuit receives the envelope and a second-order differential signal of the envelope generated by an inflection point detection circuit. The gate signal generation circuit attenuates the envelope and adds a predetermined offset to the attenuated envelope. The gate signal generation circuit compares the sum signal with the second-order differential signal to generate a gate signal. In the duration of the gate signal, a tg comparator detects, as a group delay time, a time up to the zero cross point of the second-order differential signal, and a tp comparator detects, as a phase delay time, a time up to the zero cross point in a predetermined order of a phase signal. An arithmetic control circuit calculates the coordinate position of a vibration input source on the basis of these delay times.

REFERENCES:
patent: 4980518 (1990-12-01), Kobayashi
patent: 5484967 (1996-01-01), Yanagisawa
patent: 5565893 (1996-10-01), Sato
patent: 5570299 (1996-10-01), Takioka

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