POINTER DETECTION APPARATUS AND POINTER DETECTION METHOD

• US 20100321331A1
• Filed: 03/25/2010
• Published: 12/23/2010
• Est. Priority Date: 06/18/2009
• Status: Active Grant

• Current Assignee: Wacom Co Limited (Wacom)
• Original Assignee: Wacom Co Limited (Wacom)
• Inventors: Oda, Yasuo, Yamamoto, Sadao, Sugiyama, Yoshihisa
• Granted Patent: US 8,692,779 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• 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 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 code signals, each having the same code string and a phase different from each other, and to supply the plurality of code signals to the plurality of first conductors;

(c) a signal detection circuit connected to the plurality of second conductors and configured to receive signals from the plurality of second conductors generated in response to the plurality of code signals supplied to the plurality of first conductors, and to detect and output a signal corresponding to a variation of capacitance between the conductor pattern and a pointer;

(d) 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;

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

(f) a memory circuit configured to store the correlation values, each having a plurality of bits successively output from the correlation detection circuit; and

(g) 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 code string signal production circuit includes a shift register formed from a plurality of registers configured to successively shift a phase of an input signal thereto in response to a clock signal and to output a resulting signal, wherein the shift register holds the plurality of code strings so as to produce the plurality of signals based on the plurality of code strings.

3. The pointer detection apparatus according to claim 1, wherein the code string signal production circuit includes a code string storage circuit configured to store the plurality of code strings, wherein the plurality of code strings are read out from the code string storage circuit in accordance with a predetermined sequence and the plurality of signals are produced based on the plurality of code strings.

4. The pointer detection apparatus according to claim 1, wherein the code string signal production circuit includes a signal modulation circuit configured to carry out predetermined modulation of the plurality of code strings having phases different from each other, to thereby produce the plurality of signals based on the plurality of code strings, and to supply the produced plurality of signals to the plurality of first conductors, and

wherein the signal detection circuit includes a signal demodulation circuit configured to carry out signal demodulation, corresponding to the predetermined modulation carried out by the signal modulation circuit, of signals output from the plurality of second conductors.

5. The pointer detection apparatus according to claim 1, wherein the code string signal production circuit is further configured to carry out predetermined modulation of the plurality of code strings having phases different from each other to produce the plurality of signals, and to supply the produced plurality of signals to the plurality of first conductors, and

wherein the signal detection circuit includes a signal demodulation circuit configured to carry out signal demodulation, corresponding to the predetermined modulation, of signals output from the plurality of second conductors.

6. The pointer detection apparatus according to claim 1, wherein the code string signal production circuit includes a signal storage circuit configured to store the plurality of signals obtained by carrying out predetermined modulation of the plurality of code strings having phases different from each other, wherein the plurality of signals are read out from the signal storage circuit in accordance with a predetermined sequence and supplied to the plurality of first conductors, and

wherein the signal detection circuit includes a signal demodulation circuit configured to carry out signal demodulation, corresponding to the predetermined modulation, of signals output from the plurality of second conductors.

7. The pointer detection apparatus according to claim 1, wherein the code string signal production circuit is configured to produce signals having a code string length of 4N−

1, N being an integer equal to or greater than 2, wherein a number of the first conductors disposed in the first direction is at least 2×

(4N−

1), and

wherein the produced plurality of signals are supplied to a first group of first conductors that are positioned adjacent to each other, and successively supplied to a second group of first conductors that are positioned adjacent to each other, wherein at least one of the first group of first conductors overlaps with at least one of the second group of first conductors.

8. The pointer detection apparatus according to claim 1, wherein the number of the plurality of 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 predetermined 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.

9. The pointer detection apparatus according to claim 8, wherein the compensation signal produced by the code string signal production circuit is supplied to a conductor which is disposed adjacent to one side of the plurality of first conductors to which the produced 4N−

1 signals are supplied.

10. The pointer detection apparatus according to claim 8, wherein the compensation signal is supplied directly to the signal detection circuit, without being supplied to the plurality of first conductors.

11. The pointer detection apparatus according to claim 8, wherein the number of the plurality of first conductors disposed in the first direction is at least 2×

(4N−

1) and each of the 4N−

1 signals produced based on 4N−

1 code strings having phases different from each other is supplied to a pair of the first conductors that are positioned adjacent to each other.

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 plurality of second conductors are selectively skipped in accordance with a predetermined sequence to be connected to the signal detection circuit.

13. The pointer detection apparatus according to claim 1, wherein the plurality of 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.

14. The pointer detection apparatus according to claim 13, wherein the reference signal is supplied to an input of the signal detection circuit to provide a correlation reference level in an analog domain.

15. The pointer detection apparatus according to claim 13, 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.

16. The pointer detection apparatus according to claim 1, wherein the code string signal production circuit is further configured to produce a second plurality of signals based on a second plurality of code strings having phases different from each other, wherein the second plurality of code strings have a different orthogonality as compared to the original plurality of code strings, and to supply a combination of the second plurality of signals produced based on the second plurality of code string and the plurality of signals produced based on the original plurality of code strings to the plurality of first conductors.

17. The pointer detection apparatus according to claim 1, wherein the plurality of code strings having phases different from each other are produced by the code string signal production circuit, and the plurality of first conductors disposed in the first direction are divided into a plurality of groups, and the plurality of signals produced based on the plurality of code strings are supplied to corresponding ones of the plurality of groups.

18. 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.

19. 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.

20. The pointer detection apparatus according to claim 1, wherein the plurality of signals produced by the code string signal production circuit are supplied from opposite ends of the first conductors along the first direction.

21. The pointer detection apparatus according to claim 1, wherein the number of the first conductors to which the plurality of signals produced by the code string signal production circuit are supplied and the number of the second conductors that are to be selected for obtaining one correlation value are set based on the level of the signals output from the plurality of second conductors.

22. The pointer detection apparatus according to claim 1, wherein the number of the plurality of first conductors which are disposed in the first direction is at least 2×

(4N−

1), N being an integer equal to or greater than 2, and 4N−

1 signals are produced by the code string signal production circuit and supplied to 4N−

1 ones of the first conductors while signals output from a waveform inversion circuit which inverts the phase of the 4N−

1 signals are supplied to the remaining 4N−

1 ones of the first conductors.

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

24. The pointer detection apparatus according to claim 23, wherein plural ones of the second conductors which are disposed adjacent to each other with one or more ones of the second conductors interposed therebetween are selectively connected to the differential amplification circuit.

25. 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.

26. The pointer detection apparatus according to claim 25, 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.

27. 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.

28. 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.

29. 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.

30. A method for detecting a pointer 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:

supplying a plurality of signals produced based on a plurality of code strings, each having the same code string and a phase different from each other, to the plurality of first conductors of the conductor pattern;

detecting a signal corresponding to a variation of electrostatic capacitance between the conductor pattern and a pointer;

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

determining correlation values between the code strings provided for correlation and the digital signal obtained by the conversion;

storing the correlation values; and

detecting the pointer based on the correlation values.

31. The method according to claim 30, wherein a position on the conductor pattern pointed to by the pointer is calculated based on the stored correlation values.