Coordinate input device

• US 5,831,600 A
• Filed: 06/02/1997
• Issued: 11/03/1998
• Est. Priority Date: 06/04/1996
• Status: Expired due to Term

• Current Assignee: ALPS Electric Company Limited (Alps Alpine Co., Ltd.)
• Original Assignee: ALPS Electric Company Limited (Alps Alpine Co., Ltd.)
• Inventors: Shigetaka, Hiroshi, Inoue, Kinya
• Primary Examiner(s): Hofsass, Jeffery A.
• Assistant Examiner(s): LIEU, JULIE BICHNGOC
• Application Number:
  US08/867,134
• Time in Patent Office: 519 Days
• Field of Search: 345/173, 345/174, 345/179, 345/156, 345/177, 345/471 XY, 178/18, 178/19
• US Class Current: 345/173
• CPC Class Codes: G06F 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

There is provided a coordinate input device in which when the coordinate position of a contact portion on a tablet by a coordinate input object is to be detected, influence of external noise is minimized to improve the reliability of detection of the coordinate position. The coordinate input device comprises a tablet scanned by one scan signal selected from a plurality of scan signals having different frequencies, and a coordinate data generation section for generating coordinate data representing a coordinate position of a contact portion when a coordinate input object is brought into contact with the tablet, wherein when the tablet is to be scanned with a scan signal, the coordinate data formation section sequentially selects the plurality of scan signals at least once a selecting operation, measures levels of noise included in data output from the tablet each time the selecting operation is performed, and then uses a scan signal representing a minimum noise level of the measured noise levels to scan the tablet.

Claims

1. A coordinate input device comprising an operation area scanned by one scan signal selected from a plurality of scan signals having different frequencies, and coordinate data formation means for generating coordinate data representing a coordinate position of a contact portion when a coordinate input object is brought into contact with said operation area, characterized in that said coordinate data formation means sequentially selects the plurality of scan signals at least once a selecting operation to scan said operation area, measures levels of noise included in data output from said operation area each time the selecting operation is performed, and then uses a scan signal representing a minimum noise level of the measured noise levels to scan said operation area.

2. A coordinate input device according to claim 1, characterized in that the measured noise levels are stored in a memory in correspondence with the frequencies of the sequentially selected scan signals.