Tactile effect surface for optical touch detection
An optical touch-sensitive device includes a top surface that includes tactile surface features. This produces a tactile effect experienced by the user using a finger or object (e.g., pen, stylus, or other instrument) on the surface.
1. An optical touch-sensitive device comprising:
a touch-sensitive surface that includes an active area over which touch events are detectable, wherein the touch-sensitive surface has a top surface that includes tactile surface features;
emitters and detectors arranged along a periphery of the touch-sensitive surface, the emitters producing optical beams that travel across the touch-sensitive surface to the detectors, wherein touches in the active area of the touch-sensitive surface disturb the optical beams, the touch-sensitive device determining touch events based on the disturbed optical beams.
2. The optical touch-sensitive device of claim 1 wherein the tactile surface features are undulations in the top surface.
3. The optical touch-sensitive device of claim 1 wherein the top surface is a surface of continuously varying height.
4. The optical touch-sensitive device of claim 3 wherein the top surface has a maximum difference in height from peak to trough of not more than an order of magnitude more than a wavelength of light in the optical beams.
5. The optical touch-sensitive device of claim 3 wherein the top surface has a varying height such that a contact area of a touch on the top surface is not less than half the contact area of the same touch on a flat surface without tactile surface features.
6. The optical touch-sensitive device of claim 1 wherein the tactile surface features are stepped surface features.
7. The optical touch-sensitive device of claim 6 wherein the stepped surface features have a maximum step height of not more than a wavelength of light in the optical beams.
8. The optical touch-sensitive device of claim 7 wherein the stepped surface features have a maximum step height of not more than half a wavelength of light in the optical beams.
9. The optical touch-sensitive device of claim 1 wherein the top surface is a binary surface.
10. The optical touch-sensitive device of claim 9 wherein the binary surface has a step height of not more than a wavelength of light in the optical beams.
11. The optical touch-sensitive device of claim 1 wherein the tactile surface features are laterally spaced aperiodically on the top surface.
12. The optical touch-sensitive device of claim 1 wherein a lateral spacing between tactile surface features is not less than a size of a typical human finger.
13. The optical touch-sensitive device of claim 1 wherein an average lateral size of the tactile surface features is less than a size of a typical human finger but greater than a wavelength of the optical beams.
14. The optical touch-sensitive device of claim 1 wherein the touch-sensitive surface comprises:
a flat, featureless top surface; and
a tactile coating on top of the flat, featureless top surface.
15. The optical touch-sensitive device of claim 14 wherein the tactile coating is a tactile film.
16. The optical touch-sensitive device of claim 14 further comprising:
a blocking layer on top of the flat, featureless top surface along a periphery of the active area, the blocking layer blocking ambient light from reaching the detectors.
17. The optical touch-sensitive device of claim 16 wherein the blocking layer is level with the tactile coating so that no tactile boundary is present between the blocking layer and the tactile coating.
18. The optical touch-sensitive device of claim 1 wherein the tactile surface features have a lateral size that is less than a pixel size for an underlying display module.