Contact sensitive device
A contact sensitive device includes a member capable of supporting bending waves, a first sensor mounted on the member for measuring bending wave vibration in the member, the sensor determining a first measured bending wave signal, a second sensor to determine a second measured bending wave signal and a processor that optimises a product of a set of corrected impulse response measurements from each sensor to determine information related to a contact.
1 . A method for determining information relating to a touch on a touch member capable of supporting bending waves, the touch member including a plurality of points with known locations, the method comprising:
touching the points to create bending waves in the touch member;
measuring the bending waves using sensors coupled to the touch member;
determining a phase correction associated with each of the points from the bending waves created by touching the points; and
using the phase corrections in determining information related to a subsequent touch on the touch member.
2 . The method as recited in claim 1 further comprising defining the points by a set of vectors r j where j is the number of points.
3 . The method as recited in claim 1 wherein the points are arranged in a grid.
4 . The method as recited in claim 1 further comprising measuring, for each point touched, first and second bending wave signals W 1,j (t) and W 2,j (t) using a first and second sensor of at least two pairs of sensors.
5 . The method as recited in claim 4 further comprising calculating Fourier transforms of the bending wave signals.
6 . The method as recited in claim 5 further comprising calculating an empirical phase correction associated with each of the sensor pairs using a known path length difference from the first and second sensors of each pair to the point touched.
7 . The method as recited in claim 6 wherein the empirical phase correction is calculated according to:
ϕ
12
*
(
ω
)
=
∑
j
W
^
1
,
j
(
ω
)
W
^
2
,
j
*
(
ω
)
exp
[
-
ⅈ
k
(
ω
)
Δ
x
j
]
,
where Δx j is the difference between the path lengths, x 1,j & x 2,j from the first and second sensors to the contact, Ŵ 1,j (ω) and Ŵ* 2,j (ω) are the Fourier transformation and complex conjugate Fourier transformation of the two measured bending wave signals W 1 (t) and W 2 (t); t represents time ω is 2πf where f is frequency; and k is a predetermined panel dispersion relation.
8 . A method for determining information relating to a contact on a member capable of supporting bending waves comprising applying an empirically determined phase correction to a dispersion corrected correlation function used in processing measurements of bending waves in the member caused by the contact and measured by sensors coupled to the member.
9 . A method for determining information relating to a contact on a member capable of supporting bending waves comprising:
empirically determining phase corrections according to measured bending waves resulting from contacts made on points arranged in known locations on the member; and
utilizing the phase corrections for dispersion corrected correlation calculations used in processing measurements of bending waves in the member caused by a subsequent contact of the member to determine the information related to the contact.
10 . A contact sensitive device comprising:
a member capable of supporting bending waves including a plurality of points with known locations;
at least a first and second sensor mounted on the member for measuring bending wave vibration in the member; and
a processor configured to determine a phase correction associated with each of the points from the bending waves created by touching the points.
11 . The contact sensitive device as recited in claim 10 wherein the processor is further configured to utilize one or more of the phase corrections in determining information related to location of a user touch on the touch member.
12 . The contact sensitive device as recited in claim 10 wherein the points are arranged in a grid on the member.
13 . The contact sensitive device as recited in claim 10 further comprising a first and a second sensor responsive to measure first and second bending wave signals W 1,j (t) and W 2,j (t) for each point touched.
14 . The contact sensitive device as recited 13 wherein the empirical phase correction is calculated according to:
ϕ
12
*
(
ω
)
=
∑
j
W
^
1
,
j
(
ω
)
W
^
2
,
j
*
(
ω
)
exp
[
-
ⅈ
k
(
ω
)
Δ
x
j
]
,
where Δx j is the difference between the path lengths, x 1,j & x 2,j from the first and second sensors to the contact, Ŵ 1,j (ω) and Ŵ* 2,j (ω) are the Fourier transformation and complex conjugate Fourier transformation of the two measured bending wave signals W 1 (t) and W 2 (t); t represents time ω is 2πf where f is frequency; and k is a predetermined panel dispersion relation.