pressure sensor array touchpad user interface (u.s. patent 6,570,078)
Pressure Sensor Array Touchpad User Interface
Demonstration 2: Spatial Resolution and Parameter Derivation Stability
As discussed in the preceding demonstration page, six parameters (geometric column center, geometric row center,
angle of rotation, tilt column center, tilt row center, and average pressure) can be numerically calculated from pixel
data from a pressure sensor array [1]-[2]. As mentioned there, an increase in spatial resolution and/or decrease in
measurement value quantization increase the stability of the calculated parameters as the pressure image spatially evolves,
while a decrease in the spatial resolution and/or increase in value quantization decreases the stability of the calculated
parameters. This demonstration page illustrates this in more detail. The animations below repeate the previous example of
a pressure image emulating a finger trajectory over a pressure sensor array where each pixel registers local contact pressure
values between 0 and 10. In the animation pixels with a pressure value of zero are displayed in black, while the colors
ranging from blues to cyans to greens to yellows to oranges to reds to magenta depict increasing values of pressure range
of 1 to 10. Here the pad has been made smaller while pixel boundaries and numbers signifying pressure values have been removed.
The values of the six parameters are plotted as they evolve over time in three differenet cases. The first set of six graphs
match the integer-valued quantization steps of 0 to 10 (i.e., 11 steps) used in the previous demonstration page. The center
set of six graphs decrease the quantization by increasing the number of steps to 128. The bottom set of six graphs returns
to the 11-step quantization but increases the spatial resolution by a factor of 5.
REFERENCES
[1] U.S. Patent 6,570,078, "Tactile, visual, and array controllers for real-time control of music signal processing, mixing, video, and lighting," May 27, 2003
[2] "Rich Multi-Parameter Touchpad User Interface: Technology and Examplary Implementation," 2004
[3] "Rich Multi-Parameter Touchpad User Interface: Music Applications," 2004