EP-3602257-B1 - ERASER FOR TOUCH DISPLAYS

EP3602257B1EP 3602257 B1EP3602257 B1EP 3602257B1EP-3602257-B1

Inventors

CHRISTIANSSON, TOMAS
JACOBSON, Kristofer
OHLSSON, Nicklas

Dates

Publication Date: 20260506
Application Date: 20180319

Claims (13)

A touch sensing apparatus (100), comprising: a touch surface (20), a plurality of emitters (30a), 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 (30b), arranged around the periphery of the touch surface, configured to receive light from the plurality of emitters on a plurality of light paths (50), 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 (130) 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 (110) on the touch surface where the light is attenuated or occluded by an object (60, 310) based on the plurality of transmission values; wherein the hardware processor is configured to, for each emitter; i) determine a set of relatively un-attenuated or un-occluded detection lines passing closest to the object reference point, comprising analysing emitter/detection pairs forming each detection line to determine a light path passing closest to the object reference point as an intersect detection line (150), ii) 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 and determine, from the one or more unaffected light paths that are not affected by the object, one or more object boundary light paths (160, 170) passing closest to the object reference point, wherein light paths with closest angular distances to the intersect detection line, in clockwise and counterclockwise directions relative to the intersect detection line, that are determined to be unaffected light paths, are determined to be the object boundary light paths; wherein the hardware processor is further configured to determine one or more characteristics of the object based on the one or more object boundary light paths.
The touch sensing apparatus of claim 1, further comprising a light transmissive panel (10) 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.
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.
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.
The touch sensing apparatus of claim 4, wherein the image reconstruction algorithm is an algorithm for transmission tomography.
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.
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 π/2 ± π/4 relative to the closest boundary light path.
The touch sensing apparatus of claim 1, wherein determining characteristics of the object comprises determining at least one of the centre point (140), orientation angle (415), width (430), and height (420) of the object.
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.
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.
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.
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.
A method of determining characteristics of an object in contact with a touch surface of a touch sensing apparatus (100), said touch sensing apparatus comprising: a touch surface (20), a plurality of emitters (30a) 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 (30b), arranged around the periphery of the touch surface, configured to receive light from the plurality of emitters on a plurality of light paths (50), 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 the steps of: 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 (110) on the touch surface where the light is attenuated or occluded by an object (60, 310) based on the plurality of transmission values; for each emitter; determining a set of relatively un-attenuated or un-occluded detection lines passing closest to the object reference point, comprising analysing emitter/detection pairs forming each detection line to determine a light path passing closest to the object reference point as an intersect detection line (150), 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 (160, 170) passing closest to the object reference point, wherein light paths with closest angular distances to the intersect detection line, in clockwise and counterclockwise directions relative to the intersect detection line, that are determined to be unaffected light paths, are determined to be the object boundary light paths, the method further comprising determining one or more characteristics of the object based on the one or more object boundary light paths.

Description

BACKGROUND OF THE INVENTION Field of the Invention The present disclosure relates to techniques for detecting and identifying objects on a touch surface. Description of the Related Art To an increasing extent, touch-sensitive panels are being used for providing input data to computers, electronic measurement and test equipment, gaming devices, etc. The panel may be provided with a graphical user interface (GUI) for a user to interact with using e.g. a pointer, stylus or one or more fingers. The GUI may be fixed or dynamic. A fixed GUI may e.g. be in the form of printed matter placed over, under or inside the panel. A dynamic GUI can be provided by a display screen integrated with, or placed underneath, the panel or by an image being projected onto the panel by a projector. There are numerous known techniques for providing touch sensitivity to the panel, e.g. by using cameras to capture light scattered off the point(s) of touch on the panel, by using cameras to directly observe the objects interacting with the panel, by incorporating resistive wire grids, capacitive sensors, strain gauges, etc. into the panel. In one category of touch-sensitive panels known as 'above surface optical touch systems' and known from e.g. US patent 4,459,476, a plurality of optical emitters and optical receivers are arranged around the periphery of a touch surface to create a grid of intersecting light paths (otherwise known as detection lines) above the touch surface. Each light path extends between a respective emitter/receiver pair. An object that touches the touch surface will block or attenuate some of the light paths. Based on the identity of the receivers detecting a blocked light path, a processor can determine the location of the intercept between the blocked light paths. For most touch systems, a user may place a finger onto the surface of a touch panel to register a touch. Alternatively, a stylus may be used. A stylus is typically a pen shaped object with at least one end configured to be pressed against the surface of the touch panel. An example of a stylus according to the prior art is shown in figure 2. Use of a stylus 60 may provide improved selection accuracy and pointer precision over a simple finger touch. This can be due to the engineered stylus tip 62 providing a smaller and/or more regular contact surface with the touch panel than is possible with a human finger. Also, muscular control of an entire hand in a pen holding position can be more precise than a single finger for the purposes of pointer control due to lifelong training in the use of pens and pencils. PCT/SE2016/051229 describes an optical IR touch sensing apparatus configured to determine a position of a touching object on the touch surface and an attenuation value corresponding to the attenuation of the light resulting from the object touching the touch surface. Using these values, the apparatus can differentiate between different types of objects, including multiple stylus tips, fingers, palms. The differentiation between the object types may be determined by a function that takes into account how the attenuation of a touching object varies across the touch surface, compensating for e.g. light field height, detection line density, detection line angular density etc. US2011/157096A1 discloses defining candidate touch points at the intersections of interrupted beams and are confirmed or not as actual touch points by examining test beams near to or coincident with the candidate touch point. An indication of a bounding area of clusters of points is made by using the smallest and largest X ordinates of any points in the cluster and the smallest and largest Y ordinates of any points in the cluster. US2012/212457A1 discloses determining touch events from on a template matching problem based on prediction of transmission coefficients. The data is matched against the template model. The matching process then includes determining whether there is a match against the template model and, if so, which value produces the match. A template can include beams in a contact area that are interrupted, and beams in a surrounding shaded area that are not interrupted. US2014/320459 A1 discloses a method of analysing the plurality of intersection points among the individual detection lines. For larger objects applied to the touch surface, such as palms and board erasers, it is possible to use an interaction map of the touch surface to determine an approximate shape of the object. For example, where an optical IR touch sensing apparatus is used, an attenuation map may be generated showing an area on the touch surface where the light is highly attenuated. The shape of an attenuated area may then be used to identify the position and shape of the touching object. In figure 5. an example attenuation map of a board eraser is shown. In a technique known according to the prior art, a rough shape of the eraser can be determined by identifying all points with an attenuation above