Touch determination with improved detection of weak interactions

• US 10,031,623 B2
• Filed: 09/26/2017
• Issued: 07/24/2018
• Est. Priority Date: 02/21/2012
• Status: Expired due to Fees

• Current Assignee: FlatFrog Laboratories AB
• Original Assignee: FlatFrog Laboratories AB
• Inventors: Christiansson, Tomas, Ohlsson, Nicklas
• Primary Examiner(s): Moon, Seokyun
• Application Number:
  US15/715,776
• Publication Number:
  US 20180018061A1
• Time in Patent Office: 301 Days
• Field of Search: None
• CPC Class Codes: G06F 2203/04104 Multi-touch detection in digitiser, i.e. details about the simultaneous detection of a plurality of touching locations, e.g. multiple fingers or pen and finger
• CPC Class Codes: G06F 2203/04109 FTIR in optical digitiser, i.e. touch detection by frustrating the total internal reflection within an optical waveguide due to changes of optical properties or deformation at the touch location
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/0421 by interrupting or reflecting a light beam, e.g. optical touch-screen

Abstract

Touch sensitivity is enabled using a touch system that comprises a panel configured to conduct signals along detection lines across a touch surface. A signal processor obtains observed values for the detection lines, and identifies an interaction pattern on the touch surface as a solution to a function that comprises an aggregation of differences, for each detection line, between the observed value and a projected value, which is given by a projection function that defines a functional relation between the interaction pattern and the projected value for each detection line. The signal processor implements a normalization to ensure that the interaction pattern indicates weak touches even in the presence of strong touches.

Claims

1. A method of enabling touch determination based on an output signal from a touch-sensitive apparatus, the touch-sensitive apparatus including a panel and a plurality of emitters and a plurality of detectors defining detection lines that extend across a surface portion of the panel between pairs of emitters and detectors, the touch-sensitive apparatus further including at least one signal generator coupled to the plurality of emitters to generate signals, and at least one signal detector coupled to the plurality of detectors to generate the output signal, the output signal being indicative of interaction between one or more touching objects and one or more of the detection lines, wherein the method comprises:

processing the output signal to obtain observed values for a plurality of the detection lines;

for each respective detection line among the plurality of the detection lines

generating a projected value for the respective detection line based on a projection function that defines a functional relation between a fitted interaction pattern and the projected value for the respective detection line, the fitted interaction pattern having at least one basis function defining an attenuation strength at a position on the surface portion within a two-dimensional extent, wherein the projection function models a projected value for each respective detection line as a sum of contributions from the at least one basis function arranged on the surface portion;

calculating a difference value between an observed value for the respective detection line and the projected value for the respective detection line, and

updating the fitted interaction pattern based on an optimization function to minimize the difference value; and

processing the fitted interaction pattern to determine a touch interaction.

2. The method of claim 1, wherein

the at least one basis function includes a parameter value for at least one of an x-position, y-position, height, largest width, smallest width, and rotation;

and

the updating updates the fitted interaction pattern by modifying at least one of the x-position, y-position, height, largest width, smallest width, and rotation.

3. The method of claim 1, wherein the updating the fitted interaction pattern comprises:

finding a fitted interaction pattern that causes a gradient of the optimization function for each interaction value in the fitted interaction pattern to be substantially zero.

4. The method of claim 1, wherein the processing the output signal comprises:

identifying a measurement value for each respective detection line among the plurality of the detection lines; and

generating an observed value for each respective detection line among the plurality of the detection lines, the observed value for each respective detection line representing a relative change of the measurement value to a reference value for the respective detection line.

5. The method of claim 4, wherein the observed value for each respective detection line is generated as a logarithm of the relative change.

6. The method of claim 4, wherein the reference value for the respective detection line is a function of the measurement value for the respective detection line at a calibration time without said touch interaction between said one or more touching objects and said one or more of the detection lines.

7. The method of claim 4, wherein

the method operates in a sequence of repetitions to identify the measurement value for each respective detection line among the plurality of the detection lines, generate the observed value for each respective detection line among the plurality of the detection lines, and estimate the fitted interaction pattern;

and

the method further includes intermittently updating the reference value for the respective detection line based on the output signal such that the fitted interaction pattern indicates changes in interaction with respect to a preceding repetition in the sequence of repetitions.

8. The method of claim 1, wherein the fitted interaction pattern is representative of changes in one of attenuation and transmission.

9. A non-transitory computer-readable medium storing computer code that, when executed on a data-processing system, causes the data-processing system to perform the method of claim 1.

10. A device for enabling touch determination based on an output signal from a touch-sensitive apparatus, the touch-sensitive apparatus including a panel and a plurality of emitters and a plurality of detectors defining detection lines that extend across a surface portion of the panel between pairs of emitters and detectors, the touch-sensitive apparatus further including at least one signal generator coupled to the plurality of emitters to generate signals, and at least one signal detector coupled to the plurality of detectors to generate the output signal, the output signal being indicative of interaction between one or more touching objects and one or more of the detection lines, said device comprising:

a signal processor configured to

process the output signal to obtain observed values for a plurality of the detection lines;

for each respective detection line among the plurality of the detection lines

generate a projected value for the respective detection line based on a projection function that defines a functional relation between a fitted interaction pattern and the projected value for the respective detection line, the fitted interaction pattern having at least one basis function defining an attenuation strength at a position on the surface portion within a two-dimensional extent, wherein the projection function models a projected value for each respective detection line as a sum of contributions from the at least one basis function arranged on the surface portion,

calculate a difference value between an observed value for the respective detection line and the projected value for the respective detection line, and

update the fitted interaction pattern based on an optimization function to minimize the difference value; and

process the fitted interaction pattern to determine a touch interaction.

11. The device of claim 10, wherein

the at least one basis function includes a parameter value for at least one of an x-position, y-position, height, largest width, smallest width, and rotation;

and

the signal processor is further configured to update the fitted interaction pattern by modifying at least one of the x-position, y-position, height, largest width, smallest width, and rotation.

12. The device of claim 10, wherein the signal processor is further configured to update the fitted interaction pattern by finding a fitted interaction pattern that causes a gradient of the optimization function for each interaction value in the fitted interaction pattern to be substantially zero.

13. The device of claim 10, wherein the signal processor is further configured to process the output signal by

identifying a measurement value for each respective detection line among the plurality of the detection lines;

and

generating an observed value for each respective detection line among the plurality of the detection lines, the observed value for each respective detection line among the plurality of the detection lines representing a relative change of the measurement value to a reference value for the respective detection line.

14. The device of claim 13, wherein the signal processor is further configured to generate the observed value for each respective detection line as a logarithm of the relative change.

15. The device of claim 13, wherein the reference value for the respective detection line is a function of the measurement value for the respective detection line at a calibration time without said touch interaction between said one or more touching objects and said one or more of the detection lines.

16. The device of claim 13, wherein

the signal processor is further configured to operate in a sequence of repetitions to identify the measurement value for each respective detection line among the plurality of the detection lines, generate the observed value for each respective detection line among the plurality of the detection lines, and estimate the fitted interaction pattern;

and

the signal processor is further configured to intermittently update the reference value for the respective detection line based on the output signal such that the fitted interaction pattern indicates changes in interaction with respect to a preceding repetition in the sequence of repetitions.

17. The device of claim 10, wherein the fitted interaction pattern is representative of changes in one of attenuation and transmission.

18. A touch-sensitive apparatus, comprising:

a panel,

a plurality of emitters and a plurality of detectors defining detection lines that extend across a surface portion of the panel between pairs of emitters and detectors;

at least one signal generator configured to generate signals at the plurality of emitters;

at least one signal detector configured to generate an output signal based on detected signals at the plurality of detectors; and

a signal processor coupled to the at least one signal detector, the signal processor configured to

process the output signal to obtain observed values for a plurality of the detection lines,

for each respective detection line among the plurality of the detection lines

generate a projected value for the respective detection line based on a projection function that defines a functional relation between a fitted interaction pattern and the projected value for the respective detection line, the fitted interaction pattern having at least one basis function defining an attenuation strength at a position on the surface portion within a two-dimensional extent, wherein the projection function models a projected value for each respective detection line as a sum of contributions from the at least one basis function arranged on the surface portion,

calculate a difference value between an observed value for the respective detection line and the projected value for the respective detection line, and

update the fitted interaction pattern based on an optimization function to minimize the difference value, and

process the fitted interaction pattern to determine a touch interaction.

19. The apparatus of claim 18, wherein the signal processor is further configured to process the output signal by

identifying a measurement value for each respective detection line among the plurality of the detection lines;

and

generating an observed value for each respective detection line among the plurality of the detection lines, the observed value for each respective detection line among the plurality of the detection lines representing a relative change of the measurement value to a reference value for the respective detection line.

20. The apparatus of claim 19, wherein

the signal processor is further configured to operate in a sequence of repetitions to identify the measurement value for each respective detection line among the plurality of the detection lines, generate the observed value for each respective detection line among the plurality of the detection lines, and estimate the fitted interaction pattern;

and

the signal processor is further configured to intermittently update the reference value for the respective detection line based on the output signal such that the fitted interaction pattern indicates changes in interaction with respect to a preceding repetition in the sequence of repetitions.