Coordinate reader

• US 6,606,087 B1
• Filed: 09/11/2000
• Issued: 08/12/2003
• Est. Priority Date: 09/13/1999
• Status: Expired due to Term

• Current Assignee: Brother Kogyo Kabushiki Kaisha (Brother Industries Limited)
• Original Assignee: Brother Kogyo Kabushiki Kaisha (Brother Industries Limited)
• Inventors: Tomomatsu, Yoshitsugu
• Primary Examiner(s): WU, XIAO MIN
• Application Number:
  US09/659,754
• Time in Patent Office: 1,065 Days
• Field of Search: 345/173, 345/174, 345/179, 345/156, 345/157, 345/901, 178/18.01, 178/18.02, 178/18.03, 178/18.07, 178/18.08, 178/18.1, 178/19.03, 178/20.01
• US Class Current: 345/174
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/046 by electromagnetic means
• CPC Class Codes: G06F 3/047 using sets of wires, e.g. crossed wires

Abstract

A coordinate reader includes a base member having a plurality of X-loop wires provided in a first surface of the base member, a plurality of Y-loop wires provided in a second surface of the base member, a first input plane provided over the plurality of X-coils and a second input plane provided over the plurality of Y-loop coils. When a coordinate input device generates an alternating magnetic field for inputting its coordinates into the coordinate reader, the coordinate reader detects signals generated on the X-loop wires and the Y-loop wires in response to the alternating magnetic field. Then, the coordinate reader determines, based on the detected signals, which of the first input plane or the second input plane the coordinate input device is placed on, and the coordinates of the coordinate input device on the first input plane or the second input plane.

Claims

1. A coordinate reader for detecting coordinates designated by an alternating magnetic field, comprising:

a base member comprising;

a first side including a first loop wire that generates a first signal in response to the alternating magnetic field, and a first input plane;

a second side including a second loop wire that generates a second signal in response to the alternating magnetic field, and a second input plane;

a signal detection unit that detects the first and the second signals;

an input plane determination unit that determines from which of the first input plane or the second input plane the coordinates are designated by the alternating magnetic field by using at least one of the first and the second signals; and

a coordinate determination unit that determines a first coordinate and a second coordinate that are designated by the alternating magnetic field based on the detected first and second signals, respectively.

2. The coordinate reader of claim 1, wherein the base member further comprises a plate dividing the base member into the first side and the second side.

3. The coordinate reader of claim 2, wherein the base member has a plurality of first loop wires and a plurality of second loop wires, wherein the signal detection unit has a first signal level detector detecting a first signal level and a second signal level detector detecting a second signal level, the first signal level being the levels of the signals that are substantially equivalent on any adjacent two first loop wires among the plurality of the first loop wires, the second signal level being the levels of the signals that are substantially equivalent on any adjacent two second loop wires among the plurality of the second loop wires, and wherein the input plane determination unit determines from which of the first input plane or the second input plane the coordinates are designated by the alternating magnetic field by using at least one of the first signal level and the second signal level.

4. The coordinate reader of claim 3, wherein the input plane determination unit compares the first signal level and the second signal level, and determines, upon the comparison of the first signal level and the second signal level, from which of the first input plane or the second input plane the coordinates are designated by the alternating magnetic field.

5. The coordinate reader of claim 3, wherein the input plane determination unit stores a predetermined signal level, compares the reference level with one of the first signal level and the second signal level, and determines, upon the comparison of the predetermined signal level with one of the first signal level and the second signal level, from which of the first input plane or the coordinates are designated by the alternating magnetic field.

6. The coordinate reader of claim 5, wherein the predetermined signal level corresponds to an intermediate value between the first signal level and the second signal level.

7. The coordinate reader of claim 3, further comprising a correction unit that corrects at least one of the first coordinates and the second coordinates, upon the determination of the input plane by the input plane determination unit.

8. The coordinate reader of claim 2, further comprising a shielding member that shields one of the first input plane and the second input plane against noise from outside sources.

9. The coordinate reader of claim 1, wherein the first loop wire and the second loop wire is a copper wire covered with an insulating layer.

10. The coordinate reader of claim 2, wherein the base member is made of a foam material, the plate is made from either acrylic resin, ABS, or PC, and the first and second input plane is made of PET.

11. The coordinate reader of claim 1, wherein the first and second signals are amplified by an amplifier, filtered by a band-pass filter and detected by an amplitude detector in the signal detection unit.

12. A method for detecting a coordinate designated by an alternating magnetic field on one of a plurality of input planes provided in a coordinate reader, comprising the steps of:

generating a signal in response to the alternating magnetic field;

detecting the signal;

determining, based on the detected signal, from which of the coordinate input planes the coordinate is designated by the alternating magnetic field; and

determining, based on the signal, the coordinates designated by the alternating magnetic field on the determined input plane.

13. The method of claim 12, wherein the signal is generated by generating a first signal in response to the alternating magnetic field by a first loop wire and generating a second signal in response to the alternating magnetic field by a second loop wire.

14. The method of claim 13, wherein the designated coordinate input plane is determined by a first signal level detector detecting a first signal level and a second signal level detector detecting a second signal level, the first signal level being the levels of the signals that are substantially equivalent on any adjacent two first loop wires among the plurality of first loop wires and the second signal level being the level of the signals that are substantially equivalent on any adjacent two second loop wires among the plurality of second loop wires.

15. The method of claim 14, wherein the designated coordinate input plane is determined by comparing the first signal level and the second signal level and determining upon a comparison of the first signal level and the second signal level, from which of the coordinate input planes is designated by the alternating magnetic field.

16. The method of claim 14, wherein the designated coordinate input plane is determined by comparing a reference level with one of the first signal level and the second signal level and determining upon a comparison of the predetermined signal level which one of the first signal level and the second signal level, from which of the coordinate input planes is designated by the alternating magnetic field.

17. The method of claim 16, wherein the predetermined signal level corresponds to an intermediate value between the first signal level and the second signal level.

18. The method of claim 17, further comprising the step of correcting the at least one of the first coordinates and the second coordinates upon the determination of the input plane by the input plane determination unit.

19. The method of claim 13, further comprising the step of shielding one of the first loop wire and the second loop wire against noise from outside sources.

20. A coordinate reader for detecting a coordinate designated by an alternating magnetic field on one of a plurality of input planes provided in a coordinate reader, comprising:

signal generating means for generating a signal in response to the alternating magnetic field;

signal detecting means for detecting the signal;

input plane determination means for determining, based on the detected signal, from which of the input planes the coordinate is designated by the alternating magnetic field;

coordinate determination means for determining, based on the detected signal, the coordinate designated by the alternating magnetic field on the determined input plane.