Eraser for touch displays

• US 10,606,414 B2
• Filed: 03/19/2018
• Issued: 03/31/2020
• Est. Priority Date: 03/22/2017
• Status: Active Grant

• Current Assignee: FlatFrog Laboratories AB
• Original Assignee: FlatFrog Laboratories AB
• Inventors: Christiansson, Tomas, Jakobson, Kristofer, Ohlsson, Nicklas
• Primary Examiner(s): Lee, Nicholas J
• Application Number:
  US15/925,230
• Publication Number:
  US 20180275788A1
• Time in Patent Office: 743 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 2203/04106 Multi-sensing digitiser, i.e. digitiser using at least two different sensing technologies simultaneously or alternatively, e.g. for detecting pen and finger, for saving power or for improving position detection
• 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 3/04186 Touch location disambiguation
• CPC Class Codes: G06F 3/042 by opto-electronic means
• CPC Class Codes: G06F 3/0421 by interrupting or reflecting a light beam, e.g. optical touch-screen

Abstract

An optical IR touch sensing apparatus configured to determine, based on output signals of light detectors, a light energy value for each light path across a touch surface, and generate a transmission value for each light path based on the light energy value. A processor is then configured to process the transmission values to determine an object reference point on the touch surface where the light is attenuated or occluded by an object and determine, from a set of light paths unaffected by an object, a set of object boundary light paths comprising one or more light paths passing closest to the object reference point. The characteristics of the object may then be determined in dependence on the set of object boundary light paths.

Claims

1. A touch sensing apparatus, comprising:

a touch surface,

a plurality of emitters, arranged around a periphery of the touch surface, configured to emit a plurality of light beams such that one or more objects touching the touch surface cause an attenuation of at least one of the plurality of light beams;

a plurality of detectors, arranged around the periphery of the touch surface, configured to receive light from the plurality of emitters on a plurality of light paths, wherein each detector in the plurality of detectors is arranged to receive light from more than one emitter of the plurality of emitters; and

a hardware processor configured to;

determine, based on output signals from the plurality of detectors, a plurality of transmission values, each of the plurality of transmission values corresponding to each of the plurality of light paths;

determine an object reference point on the touch surface where the light is attenuated or occluded by an object based on the plurality of transmission values;

determine one or more unaffected light paths from the plurality of light paths that are not affected by the object based on the plurality of transmission values;

determine, from the one or more unaffected light paths that are not affected by the object, one or more object boundary light paths in relation with the object reference point; and

determine one or more characteristics of the object based on the one or more object boundary light paths,

wherein the one or more object boundary light paths comprise a closest boundary light path passing closest to the object reference point.

2. The touch sensing apparatus of claim 1, further comprising a light transmissive panel defining the touch surface and an opposite surface, wherein the emitters are configured to introduce light into the panel for propagation by internal reflection between the touch surface and the opposite surface, and the detectors are configured to receive the light propagating in the panel.

3. The touch sensing apparatus of claims 1, wherein the emitters are configured to transmit the beams of light above the touch surface and the detectors are configured to receive said beams of light travelling above the touch surface.

4. The touch sensing apparatus of claim 1, wherein processing the transmission values comprises operating an image reconstruction algorithm on at least a portion of the transmission values to determine areas of the touch surface attenuated by objects.

5. The touch sensing apparatus of claim 4, wherein the image reconstruction algorithm is an algorithm for transmission tomography.

6. The touch sensing apparatus of claim 1, wherein processing the transmission values to determine the object reference point on the touch surface where the light is attenuated by an object comprises triangulation of attenuated or occluded light paths.

7. The touch sensing apparatus of claim 1, wherein the one or more object boundary light paths further comprises a closest perpendicular boundary light path, the closest perpendicular boundary light path being the object boundary light path passing closest to the object reference point and having an angle of between

8. The touch sensing apparatus of claim 1, wherein determining characteristics of the object comprises determining at least one of the centre point, orientation angle, width, and height of the object.

9. The touch sensing apparatus of claim 1, wherein the step of determining characteristics of the object comprises determining an orientation of the object in dependence on the angle of the closest boundary light path.

10. The touch sensing apparatus of claim 1, wherein the step of determining characteristics of the object comprises determining an orientation of the object in dependence on the angle of the closest boundary light path and the closest perpendicular boundary light path.

11. The touch sensing apparatus of claim 1, wherein the step of determining characteristics of the object comprises determining a limit of a first surface of the object in dependence on the closest boundary light path.

12. The touch sensing apparatus of claim 1, wherein the step of determining characteristics of the object comprises determining a position of a first surface of the object in dependence on the closest boundary light path and the closest perpendicular boundary light path.

13. A method of determining characteristics of an object in contact with a touch surface of a touch sensing apparatus, said touch sensing apparatus comprising:

a touch surface,

a plurality of emitters arranged around a periphery of the touch surface, configured to emit a plurality of light beams such that one or more objects touching the touch surface cause an attenuation of at least one of the plurality of light beams; and

a plurality of detectors, arranged around the periphery of the touch surface, configured to receive light from the plurality of emitters on a plurality of light paths, wherein each light detector in the plurality of detectors is arranged to receive light from more than one emitter of the plurality of emitters;

said method comprising;

determining, based on output signals from the plurality of detectors, a plurality of transmission values, each of the plurality of transmission values corresponding to each of the plurality of light paths;

determine an object reference point on the touch surface where the light is attenuated or occluded by an object based on the plurality of transmission values;

determining one or more unaffected light paths from the plurality of light paths that are not affected by the object based on the plurality of transmission values;

determining, from the one or more unaffected light paths that are not affected by the object, one or more object boundary light paths in relation with the object reference point, and

determining one or more characteristics of the object based on the one or more object boundary light paths,

wherein the one or more object boundary light paths comprise a closest boundary light path passing closest to the object reference point.