Touch force estimation in touch-sensing apparatus

• US 10,088,957 B2
• Filed: 07/14/2015
• Issued: 10/02/2018
• Est. Priority Date: 09/11/2012
• Status: Active Grant

• Current Assignee: FlatFrog Laboratories AB
• Original Assignee: FlatFrog Laboratories AB
• Inventors: Johansson, Andreas, Ohlsson, Nicklas
• Primary Examiner(s): Sitta, Grant
• Application Number:
  US14/799,153
• Publication Number:
  US 20150317036A1
• Time in Patent Office: 1,176 Days
• Field of Search: 345173-176
• 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

A device implements a method for estimating the application force of a touching object onto a touch surface in an FTIR-based projection-type touch-sensing apparatus. The apparatus generates projection signals representing radiation that has propagated on a plurality of propagation paths by total internal reflection (TIR) inside a transmissive panel beneath a touch surface of the transmissive panel such that a touching object on the touch surface causes attenuation (frustration) of at least one of the projection signals. The device generates a time series of force values, which represent the application force, based on a time series of magnitude values, which represent a magnitude of a peak in two-dimensional interaction patterns generated by image reconstruction processing of the projection signals, the peak corresponding to the touching object on the touch surface. The force estimation may involve one or more corrections.

Claims

1. A method of data processing in relation to a touch-sensing apparatus, wherein the touch-sensing apparatus is operable to generate projection signals representing radiation that has propagated on a plurality of propagation paths across a touch surface of a panel such that a touching object on the touch surface causes attenuation of at least one of the projection signals, said method comprising:

generating a peak corresponding to the touching object on the touch surface by image reconstruction processing of the projection signals;

generating, as a function of a time series of magnitude values, a time series of force values representing an application force of the touching object onto the touch surface, a current force value in the time series of force values calculated as a function of a current magnitude value among the magnitude values and a current speed of the touching object;

detecting, based on the current speed, that the touching object is in a low speed state; and

applying a duration-based modification function to the current magnitude value to counteract a gradual increase in attenuation with time for the touching object.

2. The method of claim 1, further comprising:

associating the touching object with a counter, which is configured to be incremented with a duration of the touching object in the low speed state, wherein

the duration-based modification function operates on the counter and the current magnitude value.

3. The method of claim 2, further comprising:

applying an increment to the counter that decreases with the current speed while the touching object is in the low speed state.

4. The method of claim 2, further comprising:

applying a decrement to the counter when the touching object has left the low speed state.

5. The method of claim 4, wherein the decrement is increased with increasing current speed of the touching object.

6. The method of claim 1, further comprising:

operating a low-pass filter on at least one of the time series of force values and the time series of magnitude values.

7. The method of claim 6, further comprising:

decreasing a cut-off frequency of the low-pass filter with increasing current speed of the touching object.

8. The method of claim 7, further comprising:

selectively delaying an increase in the cut-off frequency of the low-pass filter when the touching object is deemed to approach a stand-still on the touch surface.

9. The method of claim 1, further comprising:

applying a speed-based modification function to the current magnitude value to counteract a decreasing attenuation with increasing speed of the touching object.

10. The method of claim 1, further comprising:

obtaining a time series of size values representing a size measure of the peak in two-dimensional interaction patterns; and

applying a size-based modification function to the current magnitude value to counteract an increasing attenuation with increasing size of the peak.

11. The method of claim 1, further comprising:

obtaining the time series of magnitude values by repeatedly obtaining current values of the projection signals,

processing the current values by image reconstruction to generate a current interaction pattern for the touch surface,

identifying a peak associated with the touching object in the current interaction pattern, and

computing a magnitude value for the identified peak.

12. The method of claim 11, wherein the computed magnitude value represents a degree of attenuation or transmission of radiation at the location of the touching object on the touch surface.

13. A non-transitory computer readable medium comprising computer-readable instructions which, when executed by a data-processing system, cause the data-processing system to carry out the method of claim 1.

18. The method of claim 1, further comprising:

generating the projection signals representing the radiation that has propagated on the plurality of propagation paths across the touch surface of the panel.

21. The method of claim 1, wherein the current speed of the touching object is a current speed of the touching object across the touch surface.

14. A device for data processing in relation to a touch-sensing apparatus, wherein the touch-sensing apparatus is operable to generate projection signals for radiation that has propagated across a touch surface of a panel such that a touching object on the touch surface causes attenuation of at least one of the projection signals, said device comprising:

a signal processor configured to

generate a peak corresponding to the touching object on the touch surface by image reconstruction processing of the projection signals,

generate, as a function of a time series of magnitude values, a time series of force values representing an application force of the touching object onto the touch surface, a current force value in the time series of force values calculated as a function of a current magnitude value among the magnitude values and a current speed of the touching object,

detect, based on the current speed, that the touching object is in a low speed state, and

apply a duration-based modification function to the current magnitude value to counteract a gradual increase in attenuation with time for the touching object.

16. A touch-sensing apparatus including a device according to claim 14, wherein

the panel is a transmissive panel configured to conduct radiation from a plurality of incoupling points to a plurality of outcoupling points by total internal reflection inside the transmissive panel, thereby defining a plurality of propagation paths beneath the touch surface on the transmissive panel between pairs of incoupling points and outcoupling points such that the touching object on the touch surface causes the radiation on at least one of the plurality of propagation paths to be attenuated by frustration of the total internal reflection;

and

the touch-sensing apparatus further includes

at least one signal generator coupled to the incoupling points to generate the radiation, and

at least one signal detector coupled to the outcoupling points to detect the radiation on the plurality of propagation paths, and to generate corresponding projection signals.

17. A touch-sensing apparatus including the device of claim 14, the touch-sensing apparatus further comprising:

at least one signal generator configured to generate the radiation;

at least one signal detector configured to detect radiation on a plurality of propagation paths, and to generate corresponding projection signals; and

the panel having the touch surface.

19. The device of claim 14, wherein the signal processor is further configured to obtain the time series of magnitude values representing a magnitude of the peak in a time series of two-dimensional interaction patterns.

15. A device for data processing in relation to a touch-sensing apparatus, wherein the touch-sensing apparatus is operable to generate projection signals for radiation that has propagated across a touch surface of a panel such that a touching object on the touch surface causes attenuation of at least one of the projection signals, said device comprising:

means for generating a peak corresponding to the touching object on the touch surface by image reconstruction processing of the projection signals;

means for generating, as a function of a time series of magnitude values, a time series of force values representing an application force of the touching object onto the touch surface, a current force value in the time series of force values generated as a function of a current magnitude value among the magnitude values and a current speed of the touching object;

means for detecting, based on the current speed, that the touching object is in a low speed state; and

means for applying a duration-based modification function to the current magnitude value to counteract a gradual increase in attenuation with time for the touching object.

20. The device of claim 15, further comprising:

means for obtaining the time series of magnitude values representing a magnitude of the peak in a time series of two-dimensional interaction patterns.