Extracting touch data that represents one or more objects on a touch surface
AssigneeFlatFrog Laboratories AB
InventorTomas Christiansson
Life of this patent
Estimating the term…
Abstract
A touch-sensing apparatus is based on frustrated total internal reflection (FTIR). The apparatus comprises a panel, in which sheets of light are propagated by internal reflection between a touch surface and an opposite surface. A light sensor arrangement is optically connected to the panel to measure transmitted light energy on detection lines across the touch surface. Each detection line represents a light path across the touch surface from a light source to a light sensor. An object that touches the touch surface will frustrate the propagating light and cause a local attenuation among the detection lines. A data processor is connected to the light sensor arrangement and configured to execute a process for extracting touch-related data.
Claims38
A method in a touch-sensing apparatus, said apparatus comprising a light transmissive panel that defines a touch surface and an opposite surface, a light source arrangement for providing sheets of light inside the panel, wherein said sheets comprise light that propagates by internal reflection between the touch surface and the opposite surface, and a light sensor arrangement for measuring transmitted light energy, wherein the light source arrangement and the light sensor arrangement are arranged to define a grid of detection lines on the touch surface, each detection line D representing a light path across the touch surface from the light source arrangement to the light sensor arrangement, and wherein the touch-sensing apparatus is configured such that one or more objects touching the touch surface causes a local attenuation in said grid of detection lines, said method comprising the steps of:
- obtaining an output vector containing signal values indicative of light received by the light sensor arrangement on a set of detection lines;
- representing a two-dimensional attenuation field on the touch surface by at least one two-dimensional basis function, wherein the or each basis function defines an attenuation strength within its two-dimensional extent;
- and
- calculating an estimated attenuation field, based on a mapping of said set of detection lines to the or each basis function, by optimizing at least one of the attenuation strength and the location of the or each basis function such that the estimated attenuation field yields the output vector;
- and
- processing the estimated attenuation field for extraction of touch data relating to said one or more objects.
A device for extracting touch data related to one or more objects on a touch surface included in a touch-sensing apparatus, said touch-sensing apparatus comprising a light transmissive panel that defines the touch surface and an opposite surface, a light source arrangement for providing sheets of light inside the panel, wherein said sheets comprise light that propagates by internal reflection between the touch surface and the opposite surface, and a light sensor arrangement for measuring transmitted light energy, wherein the light source arrangement and the light sensor arrangement are arranged to define a grid of detection lines on the touch surface, each detection line representing a light path across the touch surface from the light source arrangement to the light sensor arrangement, and wherein the touch-sensing apparatus is configured such that said one or more objects touching the touch surface causes a local attenuation in said grid of detection lines, said device comprising:
- an element for obtaining an output vector containing signal values indicative of light received by the light sensor arrangement on a set of detection lines;
- an element for representing a two-dimensional attenuation field on the touch surface by at least one two-dimensional basis function, wherein the or each basis function defines an attenuation strength within its two-dimensional extent;
- an element for calculating an estimated attenuation field, based on a mapping of said set of detection lines to the or each basis function, by optimizing at least one of the attenuation strength and the location of the or each basis function such that the estimated attenuation field yields the output vector;
- and
- an element for processing the estimated attenuation field for extraction of said touch data.
(canceled)
A method in a touch-sensing apparatus, said apparatus comprising a light transmissive panel that defines a touch surface and an opposite surface, a light source arrangement for providing sheets of light inside the panel, wherein said sheets comprise light that propagates by internal reflection between the touch surface and the opposite surface, and a light sensor arrangement for measuring transmitted light energy, wherein the light source arrangement and the light sensor arrangement are arranged to define a grid of detection lines on the touch surface, each detection line representing a light path across the touch surface from the light source arrangement to the light sensor arrangement, and wherein the touch-sensing apparatus is configured such that one or more objects touching the touch surface causes a local attenuation in said grid of detection lines, said method comprising the steps of:
- obtaining an output vector containing signal values indicative of light received by the light sensor arrangement on a set of detection lines;
- representing a two-dimensional attenuation field on the touch surface by attenuation values contained in an attenuation vector a,
- estimating the attenuation field by Bayesian inversion based on Bayes' formula:
- p(a|d)=κ·p(a)·p(d|a),
- wherein κ is a constant, p(a) is a prior distribution which represents the probability distribution of the attenuation values independently of the output vector d, p(d|a) is a likelihood distribution which represents the probability distribution of the signal values given the attenuation vector a, and p(a|d) represents the probability distribution of the attenuation values given the output vector d;
- and
- processing the estimated attenuation field for extraction of touch data relating to said one or more objects.
Dependencies are inferred from the claim text.