Low-latency touch sensitive device
Disclosed are a sensor and method that provide detection of touch events from human fingers on a two-dimensional manifold with the capability for multiple simultaneous touch events to be detected and distinguished from each other. In accordance with an embodiment, the touch events are detected, processed and supplied to downstream computational processes with very low latency, i.e. on the order of one millisecond or less. Disclosed is a projected capacitive method that has been enhanced for high update rate and low latency measurements of touch events. The technique can use parallel hardware and higher frequency waveforms to gain the above advantages. Also disclosed are methods to make the measurements sensitive and robust, allow the technique to be used on transparent display surfaces and permit economical manufacturing of products which employ the technique.
1. A low-latency touch sensitive device comprising:
first and second plurality of conductors being arranged such that:
each of the paths of the conductors of the first plurality of conductors cross each of the paths of the conductors of the second plurality of conductors, and wherein
when the touch sensitive device is not being touched, a negligible amount of signal is coupled between them, and
when the touch sensitive device is being touched, a non-negligible amount of signal is coupled between them;
signal generator adapted to generate a plurality of unique orthogonal signals, each unique orthogonal signal being orthogonal to each of the other unique orthogonal signals and each unique orthogonal signals being a sinusoidal orthogonal signal that is pre-selected so as to have no simple harmonic relationship with the other sinusoidal signals;
transmitter associated with the first plurality of conductors, the transmitter being adapted to transmit each of the plurality of unique orthogonal signals on each of the first plurality of conductors simultaneously;
receiver associated with the second plurality of conductors, the receiver being adapted to receive signals present on each of the second plurality of conductors; and
signal processor being adapted to decode the signals present on each of the second plurality of conductors, and for each of the signals present on each of the second plurality of conductors to determine which of the unique orthogonal signals form a non-negligible part thereof.
2. The device claimed in claim 1 , wherein signal is coupled between crossing conductors as a result of capacitive coupling resulting from touch in proximity to the cross.
3. The device claimed in claim 1 , further comprising:
modulator for modulating the plurality of unique orthogonal signals prior to transmission;
demodulator for demodulating the plurality of unique orthogonal signals prior to decoding; and
wherein the transmitter transmits and the receiver receives the modulated unique orthogonal signals.
4. The device claimed in claim 3 , wherein the modulation and demodulation are BPSK.
5. The device claimed in claim 3 , wherein modulation and demodulation of the plurality of unique orthogonal signals are opposite functions.
6. The device claimed in claim 1 , wherein the signal processor performs a Fourier transform in connection with the decoding of signals.
7. The device claimed in claim 1 , wherein the signal processor utilizes a filter bank in connection with the decoding of signals.
8. The device claimed in claim 1 , wherein the signal processor comprises a filter bank to decode signals.
9. The device claimed in claim 1 , wherein the signal processor determines the relative strength of the unique orthogonal signals that form a non-negligible part of each of the signals present on each of the second plurality of conductors.
10. The device claimed in claim 9 , further comprising:
interpolator for determining the location of touch from information including the relative strengths of the unique orthogonal signals.
11. The device claimed in claim 8 , wherein the filter bank comprises an analog filter.
12. The device claimed in claim 8 , wherein the filter bank comprises a switched capacitor analog filter.
13. The device claimed in claim 1 , further comprising:
band-pass filter for filtering received signals present on each of the second plurality of conductors prior to being decoded by the signal processor; and
heterodyne for reducing the frequency of band-pass filtered received signals present on each of the second plurality of conductors prior to being decoded by the signal processor.
14. A low-latency touch sensitive device comprising:
first and second plurality of conductors being arranged such that:
each of the paths of the conductors of the first plurality of conductors cross each of the paths of the conductors of the second plurality of conductors, and wherein
when the touch sensitive device is not being touched, a negligible amount of signal is coupled between them, and
when the touch sensitive device is being touched, a non-negligible amount of signal is coupled between them;
signal generator adapted to generate a plurality of unique orthogonal signals, each unique orthogonal signal being orthogonal to each of the other unique orthogonal signals, wherein the signal generator comprises a source signal generator to generate a source signal comprising a combination of sinusoids and a filter bank adapted to take the source signal and filter it into a plurality of unique orthogonal signals;
transmitter associated with the first plurality of conductors, the transmitter being adapted to transmit each of the plurality of unique orthogonal signals on each of the first plurality of conductors simultaneously;
receiver associated with the second plurality of conductors, the receiver being adapted to receive signals present on each of the second plurality of conductors; and
signal processor being adapted to decode the signals present on each of the second plurality of conductors, and for each of the signals present on each of the second plurality of conductors to determine which of the unique orthogonal signals form a non-negligible part thereof.
15. The device claimed in claim 1 , wherein the first and second plurality of conductors each comprises a thin irregular web of conductive material.
16. The device claimed in claim 1 , wherein the first and second plurality of conductors each comprise at least some thin transparent conductors.
17. The device claimed in claim 16 , wherein the at least some thin transparent conductors are wider at locations where they are not crossing another conductor.
18. The device claimed in claim 1 , wherein the first and second plurality of conductors are arranged in rows and columns, respectively.
19. The device claimed in claim 18 , wherein the rows and columns are perpendicular to each other.
20. The device claimed in claim 18 , wherein the rows and columns are angled with respect to each other between about 30 and 150 degrees.
21. The device claimed in claim 18 , wherein the first plurality of conductors forming the rows are generally parallel to each other.
22. The device claimed in claim 21 , wherein the second plurality of conductors forming the columns are generally parallel to each other.
23. The device claimed in claim 1 , wherein the first and second plurality of conductors are arranged in a concentric circles and spoke configuration, respectively.
24. The device claimed in claim 1 , wherein the second and first plurality of conductors are arranged in a concentric circles and spoke configuration, respectively.
25. The device claimed in claim 1 , further comprising:
third plurality of conductors being arranged such that each of the conductors of the third plurality of conductors cross at least one other conductor; and
second signal generator adapted to generate a second plurality of unique orthogonal signals, each of the second plurality of unique orthogonal signals being orthogonal to each of the other signals in the second plurality of unique orthogonal signals and to each unique orthogonal signal.
26. A low-latency touch sensitive device comprising:
first and second plurality of optical waveguides being arranged such that:
when the touch sensitive device is not being touched, a negligible amount of light is coupled between them, and
when the touch sensitive device is being touched, a non-negligible amount of light is coupled between them;
light source adapted to generate a plurality of unique orthogonal light beams, each unique orthogonal beam being orthogonal to each of the other unique orthogonal beams;
optical coupler associated with the first plurality of optical waveguides, the optical coupler being adapted to transmit each of the plurality of unique orthogonal beams on each of the first plurality of conductors;
receiver associated with the second plurality of waveguides, the receiver being adapted to receive light present on each of the second plurality of waveguides and convert it to electronic signals; and
signal processor being adapted to decode the electronic signals corresponding to each of the second plurality of waveguides, and for each of the signals corresponding to each of the second plurality of waveguides to determine which of the signals form a non-negligible part thereof.
27. The device claimed in claim 26 , wherein the conductors are optical waveguides and each of the plurality of unique orthogonal signals is a wavelength of light.
28. The device claimed in claim 27 , wherein each wavelength of light is in the range from infrared to ultraviolet.
29. The device claimed in claim 27 , wherein each wavelength of light is in the infrared spectrum.
30. The device claimed in claim 27 , wherein each wavelength of light is in the ultraviolet spectrum.