Tablet input device

• US 4,205,199 A
• Filed: 05/24/1978
• Issued: 05/27/1980
• Est. Priority Date: 05/31/1977
• Status: Expired due to Term

• Current Assignee: Nippon Telegraph and Telephone Corporation
• Original Assignee: Nippon Telegraph and Telephone East Corporation (Nippon Telegraph and Telephone Corporation)
• Inventors: Mochizuki, Tamotsu
• Primary Examiner(s): Robinson, Thomas A.
• Application Number:
  US05/909,282
• Time in Patent Office: 734 Days
• Field of Search: 178/18, 178/19, 325/62, 33/1 M, 33/1 J, 340/365 L
• US Class Current: 178/18.03
• CPC Class Codes: G06F 3/046 by electromagnetic means

Abstract

A tablet input device includes a manipulation pad with a group of parallel drive lines and a group of sense lines which are interlaced in parallel with the drive lines. A drive circuit is provided which sequentially scans the drive lines with a variable drive current. When an input pen indicates a point on the face of the manipulation pad and when one of the drive lines adjacent to this point is excited, a voltage is induced across one or more sense lines adjacent the excited drive line. A sense circuit is provided which detects the magnitude or the polarity of the induced voltage, thereby detecting the address of the point indicated by the input pen.

Claims

1. A tablet input device comprising

(a) a manipulation pad consisting of

a drive line group consisting of a plurality of parallel conductors, and

a sense line group consisting of a plurality of parallel conductors,

said groups being parallel to each other and mutually interlaced;

(b) a drive circuit connected to said drive line group for selecting sequentially one or more drive lines and passing a variable drive current through said selected drive line or drive lines;

(c) a sense circuit connected to said sense line group for selecting one or more sense lines at the positions corresponding to said one or more selected drive lines and detecting the voltage induced across said one or more selected sense lines, at least two lines of one group and one line of the other group disposed therebetween being simultaneously selected; and

(d) an input pen for coupling together adjacent drive and sense lines at any selected point on said manipulation pad;

whereby when said variable drive current flows through said one or more selected drive lines adjacent to the point indicated by said input pen, said sense circuit may detect voltage induced across said one or more selected sense lines, thereby detecting the point selected by said input pen.

2. A tablet input device as set forth in claim 1 wherein said sense circuit detects the magnitude of the voltage induced across said one or more selected sense lines.

3. A tablet input device as set forth in claim 1 wherein said sense circuit detects the polarity of the voltage induced across said one or more selected sense lines.

4. A tablet input device as set forth in claim 1 wherein said input pen includes a magnetic body.

5. A tablet input device as set forth in claim 1 wherein said input pen includes an electrical conductor.

6. A tablet input device as set forth in claim 1 wherein one ends of both said drive lines are connected together and one ends of said sense lines are connected together.

7. A tablet input device as set forth in claim 1 wherein one ends of said drive lines are connected together so as to be fed back to said drive circuit;

and one ends of said sense lines are connected together.

8. A tablet input device as set forth in claim 1 wherein one ends of said drive lines are connected together;

and one ends of said sense lines are connected together so as to be fed back to said sense circuit.

9. A tablet input device as set forth in claim 1 wherein one ends of said drive lines are connected together so as to be fed back to said drive circuit;

and one ends of said sense lines are connected together so as to be fed back to said sense circuit.

10. A tablet input device as set forth in claim 1 wherein one ends of both said drive and sense lines are connected together so as to be fed back to said drive and sense circuits.

11. A tablet input device as set forth in claim 1 wherein said drive and sense lines each are arrayed in the form of a loop;

and said looped drive and sense lines are interlaced.

12. A tablet input device as set forth in claim 1 wherein said manipulation pad further includes as second group of drive lines which are parallel to each other but perpendicular to the drive lines of said first mentioned drive line group;

and a second group of sense lines which are in parallel with each other but are perpendicular to the sense lines of said first mentioned sense line group.

13. A tablet input device characterized by the provision of

(a) a manipulation pad including

a group of parallel drive lines which are conductors, and a group of parallel sense lines which are conductors and which are arrayed in parallel and coplanar relationship with said parallel drive lines;

(b) an input pen for indicating a point on the face of said manipulation pad, said input pen holding a magnetic or electrically conductive body at the tip thereof;

(c) a counter consisting of a first counter means for counting the address data associated with said drive or sense lines and a second counter means for counting a fraction of the contents in said first counter means;

(d) a drive circuit connected to said group of drive lines for sequentially selecting one or more drive lines at a predetermined time interval and passing a variable drive current through said one or more selected drive lines; and

(e) a sense circuit connected to said group of sense lines and responsive to the contents in said first counter means for selecting one or more sense lines at a predetermined time interval which are associated with said one or more selected drive lines, obtaining an envelope of the voltage which is induced across said one or more selected sense lines and which changes in time and deriving the contents in said counter as the address of the point indicated by said input pen when said envelope equals a predetermined threshold level.

14. A tablet input device as set forth in clam 13 wherein a first group of drive lines and a first group of sense lines are arrayed in row while a second group of drive lines and a second group of sense lines are arrayed in column;

and said first and second groups of drive lines are connected to said drive circuit while said first and second groups of sense lines are connected to said sense circuit, whereby the point indicated by said input pen in the direction of rows may be detected by said first groups of drive and sense lines while said point in the direction of columns may be detected by said second groups of drive and sense lines.

15. A tablet input device characterized by the provision of

(a) a manipulation pad having

a group of drive lines which are conductors and which are arrayed in parallel with each other and equidistantly spaced apart from each other and whose one ends are connected together so as to be fed back to said drive circuit;

and

a group of sense lines which are conductors and whose one ends are connected together and which are arrayed in parallel with each other and in parallel and coplanar relationship with said drive lines and which are so interlaced with said drive lines that two sense lines may be located on either sides of any of said drive lines and equiangularly spaced apart therefrom;

(b) an input pen which is used for indicating a point on the face of said manipulation pad and which holds a magnetic body or an electrically conductive body at the tip thereof;

(c) a counter consisting of a first counter means for counting the address data associated with said drive lines and a second counter means for counting a fraction of the contents in said first counter means;

(d) a drive circuit which is connected to the other ends of said drive lines and which is responsive to the contents in said first counter means for sequentially selecting said drive lines one at a time and at a predetermined time interval and passing a rectangular waveform drive current through said selected drive line; and

(e) a sense circuit which is connected to the other ends of said sense lines and which is responsive to the contents in said first counter means for sequentially selecting at a predetermined time interval two sense lines which are equidistantly spaced apart from said selected drive line on either sides thereof, sampling the voltages induced across the terminals of said two selected sense lines at the leading edge or the trailing edge of said rectangular waveform drive circuit, obtaining an envelope of said sampled induced voltages which change in time and deriving the contents in said counter as the address of the point indicated by said input pen when said envelope becomes equal to a second threshold level after said envelope has reaches a first threshold level.

16. A tablet input device as set forth in claim 15 wherein a first group of drive lines and a first group of sense lines are arrayed in row while a second group of drive lines and a second group of sense lines are arrayed in column;

and said first and second groups of drive lines are connected to said drive circuit while said first and second groups of sense lines are connected to said sense circuit, whereby the point indicated by said input pen in the direction of rows may be detected by said first groups of drive and sense lines while said point in the direction of columns may be detected by said second groups of drive and sense lines.