Pressure sensing touch systems and methods

Abstract

Pressure-sensing touch systems and methods are disclosed for sensing the occurrence of a touch event based on pressure applied at a touch location. The touch system includes a light-source system and a detector system operably adjacent respective input and output edges of a waveguide. Pressure at a touch location on the waveguide gives rise to a touch event causes the waveguide to bend or flex. The waveguide bending causes a change in the optical paths of light traveling by FTIR, causing the light distribution in the output light to change. The changes are detected and are used to determine whether a touch event occurred, as well as the time-evolution of the touch event. The changes in the output light can include polarization changes caused by birefringence induced in the waveguide by the applied pressure applied. Various detector configurations are disclosed for sensing the location and pressure of a touch event.

What is claimed is: 
     
         1 . A pressure-sensing touch system for detecting a touch event caused by the application of an amount of pressure at a touch location, comprising:
 a waveguide having an upper surface, a lower surface, an input edge and an output edge, wherein the waveguide is bendable when pressure is applied at the touch location;   a light source system in optical communication with the input edge and configured to introduce light into the waveguide that defines output light at the output edge, wherein the output light has an associated intensity distribution, and where bending the waveguide from the application of the amount of pressure causes a change in the intensity distribution.   a detector system in optical communication with the output edge and configured to detect at least a portion of the output light that exits the output edge and detect the change in the intensity distribution upon bending the waveguide, and in response thereto generate a detector signal; and   a controller operably connected to and configured to control the operation of the light source system and the detector system, and further configured to process the detector signal to determine whether a touch event has occurred.   
     
     
         2 . The pressure-sensing touch system of  claim 1 , wherein the waveguide has a thickness in a range from 0.05 mm to 1.5 mm. 
     
     
         3 . The pressure-sensing touch system of  claim 1 , where the light source system includes multiple light sources and the detector system includes multiple detectors. 
     
     
         4 . The pressure-sensing touch system of  claim 1 , wherein the waveguide has a thickness and wherein the detector system includes at least one detector and at least one aperture arranged adjacent the at least one detector, wherein the at least one aperture has a dimension that is smaller than the glass thickness 
     
     
         5 . The pressure-sensing touch system of  claim 1 , wherein the waveguide has a thickness and wherein the detector system includes at least one detector having a photosensitive area that is smaller in at least one direction than the waveguide thickness. 
     
     
         6 . The pressure-sensing touch system of  claim 1 , wherein the light source system includes an input optical system having one of an input optical fiber, an input prism, an input grating and an angled input edge, and wherein the detector system includes an output optical system having one of output optical fiber, an output prism, an output grating and an angled output edge. 
     
     
         7 . The pressure-sensing touch system of  claim 1 , wherein the detector system includes at least one detector operably arranged on the upper surface of the waveguide adjacent the output edge. 
     
     
         8 . The pressure-sensing touch system of  claim 7 , wherein the detector system includes at least one detector operably arranged on the lower surface of the waveguide adjacent the output edge, wherein the detectors on the upper and lower surface are arranged to provide respective detector signals that are out of phase. 
     
     
         9 . The pressure-sensing touch system of  claim 1 , wherein the light source has a divergence lower than 5 degrees in at least one direction 
     
     
         10 . The pressure-sensing touch system of  claim 1 , wherein the light source includes an LED or a VCSEL. 
     
     
         11 . The pressure-sensing touch system of  claim 1 , wherein the light source emits light of a select polarization, and wherein the detector system includes a detector polarizer, and wherein the detector signal is representative of an amount of induced birefringence caused by said application of pressure at the touch location. 
     
     
         12 . The pressure-sensing touch system of  claim 1 , wherein the change in the intensity distribution in the output light includes the movement of intensity fringes, and wherein the detector detects the movement of the intensity fringes to determine the amount of pressure associated with the touch event. 
     
     
         13 . The pressure-sensing touch system of  claim 12 , further including an aperture arranged adjacent the detector to make the detection aperture limited. 
     
     
         14 . The pressure-sensing touch system of  claim 12 , further including a sloped attenuator arranged adjacent the detector to make the detection of output light position-sensitive on the detector. 
     
     
         15 . The pressure-sensing touch system of  claim 1 , wherein:
 the light source emits light of a select polarization,   the detector system includes a detector polarizer, and   the detector signal is representative of an amount of change in the polarization state from the path altering through different birefringent regions of the glass caused by said application of pressure at the touch location.   
     
     
         16 . The pressure-sensing touch system of  claim 15 , wherein the change in polarization is from induced birefringence and the change of the path of light through different regions of existing birefringence that are formed in the fabrication of the glass. 
     
     
         17 . The pressure-sensing touch system of  claim 1 , wherein:
 the light source emits light of a select polarization, and   the detector system includes multiple detectors with different polarizing optics in front of each that allow the detection of the polarization state of the emitted light from the glass.   
     
     
         18 . The pressure-sensing touch system of the  claim 17 , wherein one or more of
 the magnitude of retardance from the input polarization;   the retardance from the input polarization;   the percentage of the light that is polarized; and   the magnitude of the intensity the emitted light from the glass is detected.   
     
     
         19 . A method of sensing an application of pressure for a touch event at a touch location on a flexible waveguide, comprising:
 sending light over multiple optical paths from an input edge to an output edge of the flexible waveguide to form output light having an intensity distribution at the output edge;   flexing the waveguide by applying pressure to the waveguide, thereby causing a change in the multiple optical paths to cause a change in an intensity distribution of the output light;   detecting the change in the intensity distribution and generating a detector signal representative thereof; and   processing the detector signal to associate the change in intensity distribution with the application of pressure at the touch location.   
     
     
         20 . The method of  claim 19 , wherein detecting the change in the intensity distribution include detecting the output light in a near-field relative to the output edge.