US 5,684,277 AGranted

Coordinate input apparatus

AssigneeCanon Kabushiki Kaisha

InventorsMasaki Tokioka, Atsushi Tanaka, Yuichiro Yoshimura, Ryozo Yanagisawa, Katsuyuki Kobayashi, Hajime Sato

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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.

Claims12

Dependent claims

A coordinate input apparatus comprising:

a vibration transmission plate;
input means for inputting a vibration onto said vibration transmission plate;
vibration detection means for detecting at a plurality of detection positions an elastic wave vibration input to said vibration transmission plate;
envelope output means for outputting an envelope signal of a detection signal from said vibration detection means;
reference signal generation means for generating a reference signal by attenuating the envelope signal and adding a predetermined offset to the attenuated envelope signal;
base signal generation means for generating a second-order differential signal of the detection signal from said vibration detection means as a base signal;
gate signal generation means for comparing the reference signal and the base signal and generating a gate signal with a predetermined time width from a point where the base signal exceeds the reference signal;
group delay detection means for detecting an inflection point of the envelope signal during a duration of the gate signal, and detecting a group delay time of the vibration with reference to the detected inflection point;
phase delay detection means for detecting a zero cross point in a predetermined order of the envelope signal in the ON duration of the gate signal, and detecting a phase delay time of the vibration with reference to the detected zero cross point;
and
calculation means for calculating an input coordinate position of said input means on the basis of the group and phase delay times.

8 more elements

A coordinate input apparatus comprising:

a vibration transmission plate
input means for inputting a vibration onto said vibration transmission plate;
vibration detection means for detecting, at a plurality of detection positions, an elastic wave vibration input to said vibration transmission plate;
reference signal generation means for generating a reference signal whose level increases or decreases in correspondence with a signal level of a detection signal from said vibration detection means;
base signal generation means for generating a base signal with a predetermined waveform on the basis of the detection signal from said vibration detection means;
gate signal generation means for comparing the reference signal and the base signal and generating a gate signal with a predetermined time width from a point where the base signal exceeds the reference signal;
delay detection means for detecting a predetermined point of the envelope signal during a duration of the gate signal, and detecting a delay time of the vibration with reference to the predetermined point;
and
calculation means for calculating an input coordinate position of said input means on the basis of the delay time.

6 more elements

A coordinate input apparatus comprising:

a vibration transmission plate for transmitting a vibration;
vibration generation means for generating a vibration at a predetermined period;
vibration detection means for detecting at a plurality of positions on said vibration transmission plate an elastic wave vibration input by said vibration generation means, and outputting a detection signal;
level generation means for generating a level signal which attenuates to substantially match with an attenuation characteristic of the vibration generated by said vibration generation means so that the level signal assumes a maximum value at a generation timing of the vibration by said vibration generation means, and assumes a minimum value not less than a predetermined level after an elapse of a longest vibration transmission time on said vibration transmission plate;
gate signal generation means for generating a gate signal by detecting a portion, which exceeds the level signal, of the detection signal;
measurement means for detecting a predetermined point of the detection signal in a duration of the gate signal, and measuring a delay time of the vibration with reference to the predetermined point;
and
calculation means for calculating a coordinate position of said vibration generation means on the basis of the delay time measured by said measurement means.

5 more elements

Dependencies are inferred from the claim text.