Pointer detection apparatus and pointer detection method

• US 8,581,861 B2
• Filed: 03/25/2010
• Issued: 11/12/2013
• Est. Priority Date: 06/18/2009
• Status: Active Grant

• Current Assignee: Wacom Co Limited (Wacom)
• Original Assignee: Wacom Co Limited (Wacom)
• Inventors: Oda, Yasuo, Sugiyama, Yoshihisa, Yamamoto, Sadao
• Primary Examiner(s): Wang, Quan-Zhen
• Assistant Examiner(s): Runkle, III, Nelson D
• Application Number:
  US12/732,125
• Publication Number:
  US 20100321333A1
• Time in Patent Office: 1,328 Days
• Field of Search: 345/173
• US Class Current: 345/173
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• 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

A pointer detection apparatus includes a conductor pattern with first conductors disposed in a first direction and second conductors disposed in a second direction that crosses the first direction, and a code string signal production circuit for producing signals based on orthogonal code strings with phases different from each other and supplying the produced signals to the first conductors. The apparatus also includes a signal detection circuit connected to the second conductors for detecting a signal corresponding to a variation of electrostatic capacitance between the conductor pattern and a pointer, an analog to digital conversion (ADC) circuit for converting the signal output from the signal detection circuit into a digital signal comprising a word string of multiple bits, and a correlation detection circuit for determining correlation values between the code strings and the word string. The apparatus also includes a memory for storing correlation values successively output from the correlation detection circuit, wherein the pointer is detected based on the correlation values.

Claims

1. A pointer position detection apparatus, comprising:

(a) a conductor pattern including a plurality of first conductors disposed in a first direction and a plurality of second conductors disposed in a second direction which crosses the first direction;

(b) a code string signal production circuit configured to produce a plurality of orthogonal code signals, each having a predetermined time difference from each other, based on a code string having an orthogonal characteristic, each of the plurality of orthogonal code signals being configured to be supplied as a unit to the conductor pattern;

(c) a transmission conductor selection circuit configured to selectively supply the plurality of orthogonal code signals produced by the code string signal production circuit to the plurality of first conductors, by supplying each of the plurality of orthogonal code signals to at least two of the first conductors simultaneously for a length of the signal, to increase a reception signal level due to said each of the plurality of orthogonal code signals so as to expand a detection range for the pointer;

(d) a reception conductor selection circuit configured to selectively receive signals from the plurality of second conductors generated in response to the plurality of orthogonal code signals supplied to the plurality of first conductors;

(e) a signal detection circuit configured to detect a signal corresponding to a variation of capacitance caused between the conductor pattern and a pointer, based on the signals from the plurality of second conductors received via the reception conductor selection circuit;

(f) an analog to digital conversion circuit configured to convert the signal output from the signal detection circuit into a digital signal comprising a word string formed of a plurality of bits;

(g) a correlation detection circuit configured to determine correlation values between code strings provided for correlation and the digital signal comprising a word string formed of a plurality of bits output from the analog to digital conversion circuit;

(h) a memory circuit configured to store the correlation values output from the correlation detection circuit; and

(i) a position calculation circuit configured to calculate a position on the conductor pattern pointed to by the pointer based on the correlation values.

2. The pointer detection apparatus according to claim 1, wherein the plurality of first conductors are divided into blocks, each block including at least two first conductors that are adjacent to each other, and the transmission conductor selection circuit is configured to selectively supply each of the plurality of orthogonal code signals to each of the blocks.

3. The pointer detection apparatus according to claim 2, wherein the transmission conductor selection circuit is further configured to supply each of the plurality of orthogonal code signals to the first conductors within each block.

4. The pointer detection apparatus according to claim 2, wherein the transmission conductor selection circuit is further configured to successively change a group of the first conductors that constitute each block.

5. The pointer detection apparatus according to claim 1, wherein the transmission conductor selection circuit sets a first conductor, which is not supplied with one of the plurality of orthogonal code signals, to a determined potential.

6. The pointer detection apparatus according to claim 1, wherein the code string signal production circuit comprises a waveform inversion circuit to additionally produce the plurality of code signals having inverted phases, and the transmission conductor selection circuit is further configured to supply each of the plurality of orthogonal code signals and its phase-inverted code signal to at least two of the first conductors, respectively.

7. The pointer detection apparatus according to claim 6, wherein the transmission conductor selection circuit is further configured to:

select at least three first conductors, and

supply a code signal having a phase inverted from that of one of the plurality of orthogonal code signals to be supplied to the first conductors disposed at opposite end positions, to a first conductor interposed between those first conductors disposed at the opposite end positions.

8. The pointer detection apparatus according to claim 6, wherein the transmission conductor selection circuit is further configured to:

select an even number of first conductors that are positioned adjacent to each other, the even number being at least four, and

supply each of the plurality of orthogonal code signals and its phase-inverted code signal to two adjacent ones of the selected even number of first conductors.

9. The pointer detection apparatus according to claim 8, wherein the transmission conductor selection circuit supplies a code signal having a phase inverted from that of one of the plurality of orthogonal code signals to be supplied to the first conductors disposed at opposite end positions, to at least two of the first conductors that are interposed between those first conductors disposed at the opposite end positions.

10. The pointer detection apparatus according to claim 1, wherein the reception conductor selection circuit is further configured to:

divide the plurality of second conductors into a plurality of blocks each including at least two second conductors, and

combine signals received from the second conductors in each block for further processing.

11. The pointer detection apparatus according to claim 1, wherein a number of the plurality of orthogonal code signals to be produced by the code string signal production circuit is 4N−

1, N being an integer equal to or greater than 2, and the code string signal production circuit is further configured to produce a determined number of compensation signal(s), the number of the compensation signal(s) being set such that the sum of 4N−

1 and the number of the compensation signal(s) is an even number.

12. The pointer detection apparatus according to claim 1, wherein, when it is recognized, based on an output signal from the correlation detection circuit, that the conductor pattern is not pointed to by the pointer, the reception conductor selection circuit selectively skips the second conductors from which signals are to be received.

13. The pointer detection apparatus according to claim 1, wherein the conductor pattern is disposed on one surface of a substrate,

wherein the plurality of first conductors and the plurality of second conductors are electrically isolated from each other by an insulating member disposed in a region in which the plurality of first conductors and the plurality of second conductors cross each other;

and

wherein each of the plurality of second conductors is formed in a pattern of a line shape and each of the plurality of first conductors is formed in a pattern of a plurality of land shapes electrically connected to each other and a signal from the code string signal production circuit is supplied to the pattern of a plurality of land shapes.

14. The pointer detection apparatus according to claim 1, wherein the plurality of first conductors disposed in the first direction are disposed on one surface of a substrate and the plurality of second conductors disposed in the second direction which crosses the first direction are disposed on the other surface of the substrate.

15. The pointer detection apparatus according to claim 1, wherein the signal detection circuit includes a differential amplification circuit to which second conductors that are disposed adjacent to each other are to be selectively connected.

16. The pointer detection apparatus according to claim 1, wherein a pointing pressure exerted by the pointer on the conductor pattern is determined based on a three-dimensional spatial distribution of the correlation values.

17. The pointer detection apparatus according to claim 16, wherein the pointing pressure exerted by the pointer on the conductor pattern is further determined based on the touched area of the pointer on the conductor pattern.

18. The pointer detection apparatus according to claim 1, wherein the position calculation circuit is further configured to calculate a plurality of positions on the conductor pattern pointed to by a plurality of pointers, respectively, based on the correlation values.

19. The pointer detection apparatus according to claim 1, further comprising a conductor film, which is made of the same material used to form the first and second conductors and is applied in a region of the conductor pattern other than the region of the conductor pattern in which the first conductors and the second conductors are disposed.

20. The pointer detection apparatus according to claim 1, wherein a state in which the pointer is hovering above the conductor pattern is identified based on both a maximum value and a shape characteristic of the signals detected by the signal detection circuit.

21. The pointer detection apparatus according to claim 1, wherein the plurality of orthogonal code signals produced by the code string signal production circuit are divided into first signals to be supplied to the plurality of first conductors and second signal(s) to be supplied as a reference signal for use in the correlation detection circuit without being supplied to the plurality of first conductors.

22. The pointer detection apparatus according to claim 21, wherein the reference signal is supplied to an input of the signal detection circuit to provide a correlation reference level in an analog domain.

23. The pointer detection apparatus according to claim 21, wherein the reference signal is supplied to an output of the analog to digital conversion circuit to provide a correlation reference level in a digital domain.

24. A method for detecting a pointer position by a pointer detection apparatus having a conductor pattern that includes a plurality of first conductors disposed in a first direction and a plurality of second conductors disposed in a second direction which crosses the first direction, the method comprising:

producing a plurality of orthogonal code signals, each having a predetermined time difference from each other, based on a code string having an orthogonal characteristic, each of the plurality of orthogonal code signals being configured to be supplied as a unit to the conductor pattern;

selectively supplying the plurality of orthogonal code signals to the plurality of first conductors of the conductor pattern, by supplying each of the plurality of orthogonal code signals to at least two of the first conductors simultaneously for a length of the signal, to increase a reception signal level due to said each of the plurality of orthogonal code signals so as to expand a detection range for the pointer;

selecting a portion of the second conductors from which signals are to be received;

detecting a signal corresponding to a variation of capacitance caused between the conductor pattern and a pointer based on the signals received from the selectively switched second conductors;

converting the detected signal into a digital signal comprising a word formed of a plurality of bits;

determining correlation values between code strings provided for correlation and the digital signal comprising a word formed of a plurality of bits obtained by the conversion;

storing the correlation values; and

detecting the pointer position based on the correlation values.