Improved touch sensing device

Abstract

A touch sensing device is disclosed, comprising a panel having a touch surface, emitters and detectors arranged along a periphery, a light guiding portion arranged adjacent to the periphery and comprising a light guiding surface, the emitters and / or detectors being arranged opposite a back surface of the panel to emit and / or receive light through a passage in a frame element, the passage being arranged opposite the back surface and extending in a direction of a normal axis of the touch surface, the light guiding surface and the passage being arranged on opposite sides of the panel and overlapping in a planar direction, the light guiding surface receiving light from the emitters or guiding light to the detectors through the panel and the passage in the direction of the normal axis. A method of manufacturing a frame element for a touch sensing device is disclosed.

Description

TECHNICAL FIELD

[0001] The present invention relates to touch sensing devices operating by propagating light over a panel. More specifically, the present invention relates to optical and mechanical solutions for controlling and customizing the light path over the panel by fully or partially randomizing refraction, reflection or scattering. BACKGROUND

[0002] In a touch sensitive panel known as an "over-surface optical touch system", a set of optical emitters is arranged around the periphery of a touch surface to emit light that is reflected to travel and propagate over the touch surface. A set of light detectors is also arranged around the periphery of the touch surface to receive light from the set of emitters over the touch surface. That is, a grid-like cross light path, also known as a scan line, is created over the touch surface. An object touching the touch surface will attenuate the light on one or more scan lines of light and cause a change in the light received by one or more detectors. The position (coordinates), shape or area of the object can be determined by analyzing the light received at the detectors.

[0003] The optical and mechanical characteristics of the touch sensitive device affect the scattering of light between the emitters / detectors and the touch surface and accordingly the detected touch signal. For example, the width of the scan line affects touch performance factors such as detectability, accuracy, resolution and presence of reconstruction artifacts. The problem of prior art touch detection systems relates to sub-optimal performance with respect to the above factors. Furthermore, variations in the alignment of the optical mechanical assembly affect the detection process which can result in sub-optimal touch detection performance. Factors such as signal to noise ratio, detection accuracy, resolution, presence of artifacts can all be affected during the touch detection process. While prior art systems aim to improve these factors (e.g. detection accuracy), there is often a related trade-off in terms of the more complex and costly optical mechanical modifications that must be made to the touch system. This often results in a less compact touch system, a more complex manufacturing process and higher costs. SUMMARY

[0004] It is an object of the present invention to at least partially overcome one or more of the above-mentioned deficiencies of the prior art.

[0005] It is an object to provide a compact, less complex, robust and easy to assemble touch sensitive device.

[0006] It is another object to provide an "over-surface" based touch sensitive device that efficiently utilizes light.

[0007] One or more of these objects, as well as other objects that can appear from the following description, are at least partially achieved by a touch sensitive device according to the independent claims, embodiments of which are defined by the dependent claims.

[0008] According to a first aspect, there is provided a touch sensing device comprising: a panel defining a touch surface, the touch surface extending in a plane having a normal axis; a plurality of emitters and a plurality of detectors arranged along an outer periphery of the panel; a light directing portion arranged adjacent the outer periphery and comprising a light directing surface, wherein the emitters are arranged to emit light, the light directing surface is arranged to receive the light and direct the light through the touch surface, wherein the panel comprises a back surface opposite the touch surface, and the emitters and / or detectors are arranged opposite the back surface to emit and / or receive light through a channel in a frame element, the channel being arranged opposite the back surface and extending in the direction of the normal axis, wherein the light directing surface and the channel are arranged on opposite sides of the panel and overlap in the direction of the plane, whereby the light directing surface receives light from the emitters or directs light to the detectors through the panel and the channel in the direction of the normal axis.

[0009] According to a second aspect, there is provided a method of manufacturing a frame element for a touch sensing device, the method comprising extruding the frame element to form a light directing portion and a cavity, the cavity being adapted to receive a substrate comprising emitters and / or detectors, and milling a wall portion of the cavity to form a channel, such that, in use, a light directing surface of the light directing portion receives light from the emitters or directs light to the detectors through the channel.

[0010] Some examples of the disclosure provide a more compact touch sensing device.

[0011] Some examples of the disclosure provide a touch sensing device that is less expensive to manufacture.

[0012] Some examples of the disclosure provide a touch sensing device with a reduced number of electro-optical components.

[0013] Some examples of the disclosure provide a more robust touch sensing device.

[0014] Some examples of the disclosure provide a touch sensing device that is more reliable to use.

[0015] Some examples of the disclosure enable stray light effects to be reduced.

[0016] Some examples of the disclosure enable ambient light sensitivity to be reduced.

[0017] Some examples of the disclosure provide a touch sensing device that has a better signal-to-noise ratio for detected light.

[0018] Some examples of the disclosure provide a touch sensing device with improved resolution and improved detection accuracy for small objects.

[0019] Some examples of the disclosure provide a touch sensing device with fewer detection artifacts.

[0020] Some examples of the disclosure provide a touch sensing device with more uniform scan line coverage across a touch surface.

[0021] Other objects, features, aspects and advantages of the disclosure will become apparent from the following detailed description, the accompanying drawings, and the appended claims.

[0022] It should be emphasized that the term comprises / comprising, when used in this specification, is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. BRIEF DESCRIPTION OF DRAWINGS

[0023] These and other aspects, features and advantages of the present examples will become apparent to those of ordinary skill in the art from the following description, by way of non-limiting examples, with reference to the drawings.

[0024] Figure 1a is a schematic illustration of a cross-sectional side view of a touch sensing device according to one example of the disclosure;

[0025] Figure 1b is a schematic illustration of a cross-sectional side view of a touch sensing device according to one example of the disclosure;

[0026] Figure 1c is a schematic illustration of a top-down view of a touch sensing device according to one example of the disclosure;

[0027] Figure 1d and Figure 1e is a schematic illustration of a top-down view of an example of a touch sensing device of the prior art;

[0028] Figure 2 is a schematic illustration of a cross-sectional side view of a touch sensing device according to one example of the disclosure;

[0029] Figure 3 is a schematic illustration of a cross-sectional side view of a touch sensing device according to one example of the disclosure;

[0030] Figure 4 is a schematic illustration of a cross-sectional side view of a touch sensing device according to one example of the disclosure;

[0031] Figure 5 is a schematic illustration of a cross-sectional side view of a touch sensing device according to one example of the disclosure;

[0032] Figure 6is a schematic illustration of a cross-sectional side view of a touch sensing device according to one example of the present disclosure;

[0033] Figures 7a to 7c is a schematic illustration of a cross-sectional side view of a frame element for a touch sensing device according to a number of examples of the present invention;

[0034] Figure 8a and Figure 8b is a schematic illustration of a cross-sectional side view of a frame element for a touch sensing device according to a number of examples of the present disclosure;

[0035] Figure 8c is a schematic illustration of a cross-sectional side view of a frame element for a touch sensing device according to one example of the present disclosure;

[0036] Figure 8d is a schematic illustration of the following details of a frame element for a touch sensing device according to a number of examples of the present disclosure: a view (I) along a planar direction of a touch surface; a detailed cross-section of a light directing surface (II) as seen from the view in (I); and a side view of the cross-section in (II) (III);

[0037] Figure 9a is a schematic illustration of a cross-sectional side view of a touch sensing device according to one example of the present disclosure;

[0038] Figure 9b is a schematic illustration of a cross-sectional side view of a touch sensing device according to one example of the present disclosure;

[0039] Figure 10a is a flowchart of a method of manufacturing a frame element for a touch sensing device according to one example of the present disclosure; and

[0040] Figure 10b is another flowchart of a method of manufacturing a frame element for a touch sensing device according to one example of the present disclosure,

[0041] Figure 10c is another flowchart of a method of manufacturing a frame element for a touch sensing device according to one example of the present disclosure. DETAILED DESCRIPTION

[0042] In the following, embodiments of the present invention will be presented with respect to specific examples of touch sensitive devices. Throughout the description, the same reference numerals are used to identify corresponding elements.

[0043] Figure 1ais a schematic view of a touch sensing device 100 comprising a panel 101 defining a touch surface 102 extending in a plane 103 having a normal axis 104. The panel 101 is a light-transmissive panel. The touch sensing device 100 comprises a plurality of emitters 105 and a plurality of detectors 106 arranged along an outer periphery 107 of the panel 101. For clarity of presentation, Figure 1a only emitters 105 are shown, while Figure 1b detectors 106 are shown. It is shown how light is transmitted from the emitters 105 to the detectors 106 through the touch surface 102. The touch sensing device 100 comprises light directing portions 108 adjacent and along the outer periphery 107. The light directing portions 108 comprise light directing surfaces 109. The emitters 105 are arranged to emit light 110, the light directing surfaces 109 are arranged to receive the light 110 and direct the light through the touch surface 102 of the panel 101. As Figure 1b shown, the light is reflected to the detectors 106 via the corresponding light directing surfaces 109 after propagating through the touch surface 102. Figure 1c is a schematic view of the touch sensing device 100 from above. Figure 2 The reflections from the emitters 105 to the detectors 106 are also shown schematically. The panel 101 comprises a back surface 111 opposite the touch surface 102, and the emitters 105 and / or the detectors 106 are arranged opposite the back surface to emit and / or receive the light 110 through a channel 112 in a frame element 113 of the touch sensing device 100. The channel 112 is arranged opposite the back surface 111 and extends in a direction 104’ of the normal axis 104, i.e. substantially parallel to the normal axis 104. The light directing surfaces 109 and the channel 112 are arranged on opposite sides of the panel 101 and overlap along the direction of the plane 103. I.e. in Figure 1a there is an overlap in the horizontal position of the light directing surfaces 109 and the channel 112 such that the light path can extend vertically from the light directing surfaces 109 to the channel 112. The light directing surfaces 109 are arranged to receive the light 110 from the emitters 105 through the panel 101 and further through the channel 112 in the direction 104’ of the normal axis 104 to the detectors 106, or to direct the light to the detectors 106. It will be appreciated that the principal optical axis 110’ of the light emission can extend substantially along the direction 104’, but the light also has an angular spread around the optical axis 110’ as Figure 1a shown. As Figure 1a and Figure 4 shown, arranging the light directing surfaces 109 above the channel 112 provides an effective shielding against ambient light or system stray light. Thus, the amount of ambient light or stray light reflected to the detectors 106 can be minimized and the signal-to-noise ratio can be improved. Arranging the emitters 105 to emit the light 110 in the direction 104’ of the normal axis 104 such that the optical axis 110’ of the light 110 is substantially parallel to the normal axis 104, asFigure 1a and Figure 4 Further exemplified in Figure 1a and Figure 4 , the cross-sectional footprint of the assembly of emitters 105 and detectors 106 can be minimized in the direction of the plane 103. This can provide a further synergistic effect in providing a compact touch sensing device 100 and minimizing the number of optical components, as the light 110 is made to propagate through the panel 101, which acts as a sealing element for the emitters 105 and detectors 106 from the surrounding environment. Thus, the panel 101 can act as a sealing portion to protect the electronic device from e.g. liquid and dust. An additional optical sealing element can thus be saved. This is further advantageous as the angle at which the light is scattered through the panel 101 can be further increased, with less reflection losses, providing an improved scan line coverage across the panel 101. For example, Fresnel reflection losses can be minimized, as further described in relation to Figure 1d . Figure 1d An example of a prior art touch sensing device is shown, where emitters 401 and detectors 402 are arranged along the sides of a touch surface 403, and optical sealing components 404 are arranged along the sides. The optical sealing components 404 are arranged above the touch surface 403 and between the reflective surfaces of the opposite sides, which reflect light through the touch surface 403 (i.e. corresponding to the position of the light directing surface 109). Having such additional optical sealing components 404 can introduce unwanted reflections caused by light transmitted on the touch surface 403, especially when the light is reflected at high angles along the sides of the touch surface 403, as indicated by the reflections 406 in Figure 1d . Figure 1e is a further detailed view of the example in Figure 1d , showing further reflections 405, 405’ at each interface of such additional optical sealing components 404, 404’. Such reflections 405, 405’ can cause a significant loss of light along each side of the touch surface 403, especially with the additional optical sealing components 404, 404’.

[0044] In some applications where additional compactness is desired, the reduced number of components can be particularly advantageous. This also helps to reduce the cost of the touch sensing device 100. As will be described in more detail below, the light guiding portion 108 can be formed as part of the frame element 113, such that the light guiding surface 109 is formed in the material of the frame element 113. This further reduces the number of optical mechanical components along the light path from the touch surface 102 to the emitter 105 and the detector 106. As a result, the number of components that need to be aligned is also reduced, which simplifies the assembly. Thus, a particularly compact and robust touch sensing device 100 is provided, which is able to use the detection light more efficiently. The touch detection performance can thus be improved while reducing complexity and cost.

[0045] As shown in Figure 2 and Figure 4 , the angle (v) between the plane 103 of the touch surface 102 and the light guiding surface 109 can be less than 45 degrees. This can reduce the amount of unwanted reflection of light through the touch surface 102 (again exemplified by the reflection 406 in Figure 1d , which can otherwise cause artifacts or other disturbances when attenuation of the touch signal is detected. If the angle (v) is less than 45 degrees, the unwanted light reflection can be reflected out of the plane 103. In some examples, the angle (v) can be in the range of 41 to 44 degrees to particularly advantageously reduce the unwanted light reflection. The angle (v) can be greater than 45 degrees. For example, having the angle (v) in the range of 46 to 49 degrees can also reduce the unwanted reflection of the type shown by the scan line 406 in Figure 1d . It will be appreciated that the advantageous benefits as described above for the touch sensing device 100, i.e. less complex, more compact and cost effective manufacturing process, apply to examples where the angle (v) is both above and below 45 degrees.

[0046] The panel 101 has edges 114 extending between the touch surface 102 and the back surface 111. The channel 112 extends in a direction parallel to the plane 102 between a first channel wall 115a and an opposite second channel wall 115b at a width (dl), the first channel wall being arranged closest to the respective edge 114 of the panel 101, as schematically shown in, for example, Figure 2 and Figure 5 . The first channel wall 115a can extend at an angle 116 towards the direction 104’ of the normal axis 104. Having an angled channel wall 115a provides for reducing the amount of ambient light that is reflected towards the detector 106. A larger portion of any ambient light that is reflected by the channel wall 115a will be reflected in a direction past the detector 106, while also reducing light from the emitter 105 that directly passes the light guiding surface 109, which can cause stray light issues.

[0047] As Figure 3 and Figure 5 illustrate, the light guiding portion 108 has an edge portion 121 corresponding to the portion of the light guiding portion 108 arranged closest to the touch surface 102. The light guiding surface 109 can extend from the edge portion 121 of the light guiding portion 108 to the protrusion 117 of the light guiding portion 108, as schematically illustrated in Figure 3 and Figure 5 . The protrusion 117 can extend in a direction parallel to the plane 103 to shield ambient light from being reflected into the channel 112.

[0048] The width (d1) of the channel 112 can further be varied to optimize the amount of light 110 emitted towards the light guiding surface 109, while providing sufficient shielding against ambient or stray light. The position of the first channel wall 115a and the second channel wall 115b in the direction of the plane 103 relative to the position of the emitter 105 and / or the detector 106 can be optimized according to the specific implementation. In one example, as schematically illustrated in Figure 3 , the position of the second channel wall 115b is aligned with the position of the protrusion 117 in the direction of the plane 103. This can be particularly advantageous for shielding against ambient or stray light. At the same time, it can avoid obstruction of the emitted light 110 when optimizing the position of the emitter 105 relative to the center of the channel 112. The surface properties of the channel walls 115a, 115b can also be tailored to avoid loss of detection light or to reduce the impact of ambient or stray light, as further described below.

[0049] The emitter 105 and / or the detector 106 can be mounted to a substrate 119. The substrate 119 can comprise a chamfered edge 120a arranged opposite a corresponding mating surface 120b of the frame element 113. The mating surface 120b of the frame element 113 can form an angle 122 with the normal axis 104, as schematically illustrated in Figure 3 and Figure 6 . This enables efficient locking of the substrate 119 in place in the correct position relative to the frame element 113. Thus, safe alignment of the emitter 105 and / or the detector 106 relative to the light guiding surface 109 can be facilitated, which in turn facilitates signal optimization. As illustrated in Figure 3 , the provision of the angled surface 120b of the frame element 113 can at the same time enable removal of at least a portion of the second channel wall 115 closest to the substrate 119 and reduce the risk of obstruction of light from the emitter 105 or to the detector 106 (see e.g. Figure 2 and Figure 3 ).

[0050] The walls 115a, 115b of the channel 112 may include a diffusive light-scattering surface. Thus, the walls 115a, 115b can also be used as reflective elements, which enables better management of light, for example, recycling light and reflecting light from lost directions onto the light-guiding surface 109. As a result, a larger portion of the emitted light 110 is utilized. At the same time, the surfaces of the walls 115a, 115b can be customized to provide a specular component of the reflected light. This enables improvement of the directivity of the reflected light, for example, enabling the light to be guided to the light-guiding surface 109 above the panel 101. The ratio of the specular component of the reflected light can be changed by, for example, subjecting the channel walls 115, 115b to different surface treatments to affect their surface roughness, for example. The reflection characteristics of the light-guiding surface 109 can also be changed by surface treatments that may include etching, beading, sandblasting, brushing, and / or anodizing, as described in more detail below.

[0051] As Figure 3 and Figure 4 shown, the support 123 can be attached to the substrate 119. The support 123 can extend between the frame walls 124a, 124b of the frame element 113 and the substrate 119 in a direction parallel to the plane 103. The support 123 can facilitate alignment of the substrate 119 relative to the frame element 113. This can facilitate manufacturing and enable precise positioning of the emitter 105 and / or the detector 106 relative to the frame element 113.

[0052] The frame element 113 can be shaped to form a cavity 125. The emitter 105 and / or the detector 106 are mounted on the substrate 119, and the substrate 119 can be disposed in the cavity 125 such that the emitter 105 and / or the detector 106 are disposed closer to the respective edge 114 of the panel 101 than the substrate 119, as Figure 3 schematically shown. As described above, since the emitter 105 and / or the detector 106 are disposed closer to the edge 114 of the panel 101, this minimizes the width of the border (i.e., the width of the light-guiding portion 108 in the direction of the plane 103) while maintaining a favorable sealing effect of the panel 101. Thus, a more compact touch-sensing device 100 is provided.

[0053] Specifically, the cavity 125 can extend between the first frame wall 124a and the opposing second frame wall 124b in a direction parallel to the plane 103 with a width (d2), the first frame wall being disposed closest to the respective edge 114 of the panel 101. The substrate 119 can be disposed in the cavity 125 such that the emitter 105 and / or the detector 106 are disposed closer to the first frame wall​​

[0054] As Figure 2 illustrated, the substrate 119 can extend in the direction 104’ of the normal axis 104 in an elongated shape. This provides a reduction in the size of the touch sensing device 100 in a direction perpendicular to the normal axis 104, which can be desirable in some applications where the amount of space in this direction is limited and / or when the proportion of the available touch surface 102 to surrounding frame components is to be optimised. Extending the substrate 119 in the direction 104’ of the normal axis 104 in combination with the arrangement of the emitters 105 and / or detectors 106 closer to the first frame wall 124a than the substrate 119 provides a particularly efficient utilisation of space in the direction of the plane 103.

[0055] Figure 9a An example is shown in which the substrate 119 extends in the direction of the plane 103, enabling a compact size in the direction of the normal axis 104. This can be advantageous when used in combination with a particularly flat display panel 301, but in this case the size in the direction of the plane 103 around the display area can increase. Figure 9b is another example in which the substrate 119 extends in the direction of the plane 103, but in this other example the emitters 105 and / or detectors 106 are arranged to emit / receive light in the direction of the plane 103 via a reflective surface 135. This enables a compact size in the direction of the normal axis 104. The reflective surface 135 can be a specular reflective surface.

[0056] The light-guiding surface 109 can be anodized metal. The light-guiding surface 109 can also be surface-treated to diffusely reflect light 110 toward the touch surface 102. Anodizing alters the microtexture of surface 109 and increases the thickness of the natural oxide layer on surface 109. The thickness and porosity of the anodized oxide surface can be varied. Anodized surfaces can be dyed in various colors to achieve the desired appearance. Many different colors can provide favorable reflectivity values ​​(e.g., over 80%) in the infrared range; for example, aluminum is anodized to black, gray, or silver. Other metals can also provide favorable reflectivity characteristics, such as silver. Using wavelengths above 940 nm can be particularly advantageous, in which case many anodized materials begin to reflect significantly. Different colors can also be provided by using different alloys, such as aluminum. By applying different surface treatments to the anodized metal or alloy, the diffuse and specular components of reflectivity can be altered. Therefore, the surface roughness can be changed to optimize the ratio of these reflectivity components. The directionality of reflected light can be increased by increasing the specular component, while random scattering increases with increasing diffuse component. For example, increasing the specular component of reflection from the light-guiding surface 109 can increase the intensity of the scan line. In this case, the number and / or position of the emitters 105 can be varied to compensate for any narrowing of the scan line due to reduced diffuse light scattering. Thus, in some examples, the reflective properties of the light-guiding surface 109 can be optimized while achieving the desired aesthetic appearance of the anodized surface.

[0057] Different surface roughness characteristics can be achieved through various processes, such as etching, sandblasting, bead blasting, machining, wire drawing, polishing, and anodizing as mentioned above. In one example, the light-guiding surface 109 can have a surface roughness defined by a slope RMS(Δq) between 0.1 and 0.35. For favorable diffusivity, the slope RMS(Δq) can be between 0.1 and 0.25. Higher values ​​may reduce signal strength, and excessively weak signals may result in more tolerance-sensitive systems where light propagates through the touch surface 102 in plane 103 at an angle. (as in) Figure 1c The example in the text is by angle The scan line width (represented by the transmitter and detector viewpoints) is reduced and limited. Furthermore, the scan line width may become too narrow. In another example, for a particularly advantageous diffusion rate, the slope RMS(Δq) can be between 0.13 and 0.20, which is used to provide optimized signal strength and touch detection while maintaining favorable power consumption of the components of the touch sensing device 100.

[0058] When there is a suitable slope variation, the height variation of the sprayed or etched surface is typically in the range of 1 micrometer to 20 micrometers. However, slope RMS(Δq) optimization as described above provides the most efficient customization of reflective properties. In some examples, the light-guiding surface 109 has low roughness. In one example, the light-guiding surface 109 can be an anodized metal surface that has not undergone any treatment to increase surface roughness. In this case, the light-guiding surface 109 can be anodized directly after the extrusion process. In this case, the light-guiding surface 109 can be mirror-like, i.e., the surface 109 has not undergone any treatment to enable light propagation. In this case, the slope RMS(Δq) can be between 0 and 0.1 to provide a mirror-like surface. Such a surface may be advantageous in applications where a narrow scan line is required for a particular touch detection process, for example, when advantageously increasing the amount of available detection light passing through the touch surface 102 in the desired direction.

[0059] The frame element 113 may include a light guide portion 108. That is, the light guide portion 108 may be formed directly from the frame element 113 as a single piece, for example, by extrusion. The frame element 113 and the light guide portion 108 may be formed from various metals such as aluminum. Therefore, the light guide surface 109 may be an anodized metal surface of the frame element 113. The frame element 113 can thus be used as a diffuse light scattering element without the need for a separate optical component for diffuse light scattering. Therefore, by utilizing this integrated light guide surface 109, the number of components can be further reduced. This further eliminates the need for additional optical sealing elements to protect such a separate optical component. Thus, a more robust touch sensing device 100 that is easier to assemble is provided. Furthermore, the surfaces of the walls 115a, 115b of the channel 112 may be the metal surfaces of the frame element 113. The reflective properties of the walls 115a, 115b may be customized as described above with respect to the light guide surface 109. The frame element 113 can form a cavity 125 in which the emitter 105 and / or detector 106 are disposed. Therefore, the frame element 113 can be formed as a single integral piece having light-guiding surfaces 109, 115a, 115b for the substrate 119 and the cavity 125, as well as any mounting interfaces 129 for the display 301 to connect to the rear frame 302, such as... Figure 1a This is illustrated schematically. This allows for minimizing the number of optomechanical components in the touch sensing device 100, thereby providing a particularly robust touch sensing device 100 that is less complex and more suitable for mass production.

[0060] The light guiding portion 108 may include an outer surface 126 opposite to the light guiding surface 109, such as Figure 2The light directing surface 109 can have a higher reflectivity than the outer surface 126. Providing a different surface treatment for the light directing portion 108 of the frame element 113 enables an effective and optimized light scattering on the touch surface 102 through the light directing surface 109, while the outer surface 126 facing the user has a low reflectivity to minimize light reflection towards the user. Furthermore, this provides the desired surface appearance while not affecting the optical functionality, e.g. avoiding the light directing surface 109 being too matte due to having too steep a slope. Thus, a particularly effective use of manufacturing material can be achieved since the cross section of the single integral piece of the frame element 113 can be uniquely treated to achieve the desired light reflective functionality. For example, no alignment of separate optical components is required.

[0061] In one example, the walls 115a, 115b of the channel 112 can have a higher specular reflectivity than the light directing surface 109. This can provide a more controlled reflection of the emitted light towards the light directing surface 109. The light directing surface 109 can in turn provide a greater diffuse component for broadening the scan lines across the touch surface 102.

[0062] In one aspect, there is provided a touch sensing device 100 comprising a panel 101 defining a touch surface 102 extending in a plane 103 having a normal axis 104. A plurality of emitters 105 and a plurality of detectors 106 are arranged along an outer periphery 107 of the panel 101. A light directing portion 108 is arranged adjacent to the outer periphery 107 and comprises a light directing surface 109. The emitters 105 are arranged to emit light 110, the light directing surface 109 is arranged to receive the light 110 and direct the light 110 through the touch surface 102. The panel 101 comprises a back surface 111 opposite the touch surface 102. The emitters 105 and / or detectors 106 are arranged opposite the back surface 111 to emit and / or receive light through a channel 112 in a frame element 113. The light directing surface 109 receives light from the emitters 105 or directs light to the detectors 106 through the panel 101 and the channel 112. The frame element 113 is formed of metal and comprises the light directing portion 108, wherein the light directing surface 109 is an anodized metal surface of the frame element 113. The frame element 113 can further form a cavity 125 in which the emitters 105 and / or detectors 106 are arranged such that an optical axis 110’ of the emitted light 110 is substantially parallel to the normal axis 104. Thus, the touch sensing device 100 provides the advantageous benefits as described above by providing a compact touch sensing device 100 with improved signal-to-noise ratio and increased touch detection performance.

[0063] Figure 10ais a flowchart of a method 200 of manufacturing a frame element 113 for a touch sensing device 100. The method 200 comprises extruding 201 the frame element 113 to form a light guiding portion 108 and a cavity 125 adapted to receive a substrate 119 comprising an emitter 105 and / or a detector 106. Figure 7a An example of such an extruded frame element 113 is shown. The method 200 further comprises milling 202 a wall portion 127 of the cavity 125 to form a channel 112. Figure 7a The milled away wall portion 127 is indicated by dashed lines, so that as Figure 7b shown, an open channel 112 is provided into the cavity 125. The channel 112 is defined by channel walls or surfaces 115a, 115b. Thus, when the substrate 119 is arranged in the cavity 125, the light guiding surface 109 of the light guiding portion 108 can receive light from the emitter 105 or direct light to the detector 106 through the channel 112. Thus, a single integral piece of the frame element 113 can be provided by extruding 201 and milling 202, which integrates the alignment and support functions for the substrate 119 as well as the light guiding surfaces 109, 115a, 115b. A convenient manufacturing is provided, while the structural integrity and desired tolerances of the frame element 113 can be maintained during the process. Furthermore, the milling 202 is used to tailor the dimensions of the channel 112, which is difficult during extrusion.

[0064] Figure 7c Another example of an extruded frame element 113 is shown. The frame element 113 can be shaped such that the light guiding surface 109 has a free line of sight 137, 137' to facilitate any subsequent surface treatment of the light guiding surface 109. The line of sight 137, 137' can extend parallel to a normal (n) of the light guiding surface 109. Figure 7c An example is shown in which the line of sight of the light guiding surface 109 is indicated by a lower dashed line 137 and an upper dashed line 137', the lower dashed line corresponding to the normal (n) of the surface 109. Having a free line of sight 137, 137', i.e. said line of sight 137, 137' is not obstructed or intersected by the frame element 113, enables an optimized subsequent surface treatment process of the light guiding surface 109, such as sandblasting. Thus, it can facilitate obtaining the desired properties of the light guiding surface 109. The frame element 113 can comprise a tilt portion 138, as Figure 7c indicated schematically in, which enables the free line of sight 137, 137' of the light guiding surface 109 as described above, while maintaining a compact profile of the frame element 113. The tilt portion 138 can be arranged such that the lower line of sight 137, which corresponds to the intersection of the normal (n) with the surface 109 at a lower end point 139 of the surface 109 (closest to the wall portion 127), can extend beyond the frame element 113 without intersecting the frame element 113 or the tilt portion 138, as shown inFigure 7c The wall 127 can be part of the bevel 138.

[0065] Figure 10b to 10c is a further flowchart of the method 200. The method 200 can comprise etching or bead or grit blasting 2011, 2031 the light directing surface 109. Thus, the light directing surface 109 can have different reflectivity characteristics. In one example, as shown in Figure 10b the etching or bead or grit blasting 2011 of the light directing surface 109 is performed prior to the milling 202. Thus, the light directing surface 109 can have different reflectivity characteristics without affecting the surfaces 115a, 115b of the channels 112, which are shielded by the wall 127, for example, during the grit blasting. As mentioned above, it is advantageous to maintain a large specular reflection component of the walls 115a, 115b (as provided after the extrusion process) while the light directing surface 109 can be subsequently treated to provide more diffuse reflection. In some examples, the etching or bead or grit blasting 2031 of the light directing surface 109 can be performed after the milling 202, as shown in Figure 10c In some examples, the etching or bead or grit blasting 2031 of the light directing surface 109 can be performed after an additional milling step 203, as described below, as further indicated in Figure 10c The method 200 can comprise anodizing 204 the metal of the frame element 113.

[0066] The method 200 can comprise milling 203 the top 128 of the extruded light directing portion 108 such that the height (h) of the light directing portion above the touch surface 102 of the panel 101 is reduced when the light directing portion 109 is arranged in the frame element 113. Figure 8a A detailed view of an example of the extruded light directing portion 108 is shown. The radius of the tip 130 of the top 128 is limited by the extrusion process. Figure 8b The light directing portion 108 after the top 128 has been milled away along the dashed line in Figure 8a The milled light directing portion 108 has a height (h) and, as shown in Figure 8b the corresponding tip 130’ is sharper, i.e. the radius is reduced compared to the tip 130 provided after the extrusion. Thus, by milling away the top 128, a more compact light directing portion 108 is provided, while the part of the light directing portion 108 used for reflecting light through the touch surface 102 is substantially not affected. Figure 8a The rounded tip 130 in Figure 8bAs shown, the circular tip 130 is thus removed. Milling the top 128 thus enables a more efficient use of the height of the light guiding portion 108. It is thus possible to provide a sufficient height or height profile of the scan lines above the touch surface 102 to enable reliable identification of different touch objects with different tip sizes, while minimizing the bezel height. In some examples, the height is in the range of 1.5 mm to 2 mm. In some examples, a height of 1.8 mm can be particularly advantageous, which provides a flush bezel appearance.

[0067] The light guiding surface 109 can be concave, as Figure 8c is shown schematically in Fig. 2. Having a light guiding surface 109 that is concave towards the touch surface 102 enables controlling the direction of the reflected light and increasing the signal strength of the scan lines as needed. The light guiding surface 109 can be parabolic concave. Since the light guiding surface 109 can be formed directly in the frame element 113 as described above, the concave shape can be directly shaped in the frame element 113. It is thus possible to control the light reflection by directly shaping the frame element 113, without having to introduce any additional optical components.

[0068] Figure 8d Fig. 3 is a schematic illustration of details of the light guiding surface 109 in different views I to III. The first view (I) is along the direction 103 of the plane 103, e.g. along the arrow 103 in Fig. 1. Figure 8c The light guiding surface 109 is thus shown as an elongated portion arranged above the panel 101, while the emitters 105 and the detectors 106 are shown as elongated portions arranged below the panel 101. Figure 8d A detailed cross-section of the light guiding surface 109 is shown in the second view (II). The light guiding surface 109 can be milled or otherwise machined to form a pattern in the surface 109. Figure 8d The third view (III) of Fig. 3 is a cross-section along A-A in view (II), in Figure 8d An example of such a pattern is shown in Fig. 4, where periodic ridges 136 form a corrugated pattern or grid. Different patterns can be formed directly in the frame element 113 by milling or other machining processes to provide a light guiding surface 109 with the required reflection properties to control the direction of the light passing through the touch surface 102.

[0069] Further examples of diffuse light scattering surfaces are described below. Any of the described diffuse light scattering surfaces can be provided on the light directing surface 109. The diffuse light scattering surface can be configured to exhibit at least 50% diffuse reflection, preferably at least 70% to 85% diffuse reflection. For materials with e.g. a black appearance, reflectivity (940 nm) over 70% can be obtained by anodizing (e.g. electrolytic coloring using metal salts) as described above. The diffuse light scattering surface can be realized as a coating, layer or film applied e.g. by anodizing, painting, spraying, lamination, gluing, etc. Etching and sputtering as described above are effective processes for achieving the required diffuse reflectivity. In one example, the diffuse light scattering surface is realized as a matte white paint or ink. To obtain high diffuse reflectivity, the paint / ink can preferably contain pigments with a high refractive index. One such pigment is Ti02, which has a refractive index n = 2.8. The diffuse light scattering surface can comprise materials with varying refractive indices. It is also desirable, e.g. to reduce Fresnel losses, to match the refractive index of the paint filler and / or paint carrier to the refractive index of the material on the surface of which the paint filler and / or paint carrier is applied. With the EVOQUE® technology of Dow Chemicals, the performance of the paint can be further improved. There are many other coating materials commercially available for use as diffusers, such as fluoropolymer Spectralon, polyurethane enamel, barium sulfate based paints or solutions, granular PTFE, microporous polyester, polyethylene terephthalate film, etc. Alternatively, the diffuse light scattering surface can be realized as a planar or sheet-like device, e.g. the above-mentioned engineered diffuser, diffuser film or white paper attached e.g. by an adhesive. According to other alternatives, the diffuse light scattering surface can be realized as a semi-randomized (non-periodic) microstructure on the outer surface, possibly in combination with a cover layer of reflective material. TM Alternatively, the diffuse light scattering surface can be realized as a planar or sheet-like device, e.g. the above-mentioned engineered diffuser, diffuser film or white paper attached e.g. by an adhesive. According to other alternatives, the diffuse light scattering surface can be realized as a semi-randomized (non-periodic) microstructure on the outer surface, possibly in combination with a cover layer of reflective material.

[0070] The microstructure can be provided on such outer and / or inner surfaces by etching, embossing, molding, sandblasting, scratching, wire drawing, etc. The diffuse light scattering surface can comprise air pockets along such inner surface that can be formed during the molding process. In another alternative, the diffuse light scattering surface can be light transmissive (e.g. a light transmissive diffuser material or a light transmissive engineered diffuser) and covered with a reflective material coating on the outer surface. Another example of a diffuse light scattering surface is a reflective coating provided on a rough surface.

[0071] The diffuse light scattering surface can comprise a lens or a diffractive grating structure. A cylindrical lens structure can be incorporated into a film. The diffuse light scattering surface can comprise various periodic structures, e.g. sinusoidal corrugations provided on the inner and / or outer surface. The periodic length can be in the range between 0.1 mm and 1 mm. The periodic structures can be aligned to achieve scattering in a desired direction.​​

[0072] Thus, as mentioned above, the diffuse light scattering surface can comprise; white or colored paint, white or colored paper, Spectralon, light transmissive diffusive material covered by reflective material, diffusive polymer or metal, engineered diffuser, reflective semi-random microstructure, internally molded air pockets or diffusive material film, different engineered films comprising e.g. lenticular or other micro-lens structures or grating structures. Preferably, the diffuse light scattering surface has a low near-infrared (NIR) absorption.

[0073] In a variant of any of the above embodiments, where the diffuse light scattering element provides a reflector surface, the diffuse light scattering element can have no or little specular component. This can be achieved by using a matte diffusive film in air, a large internally reflective diffuser or a large transmissive diffuser. This enables effective scan line broadening by avoiding the narrow, superimposed specular scan lines typically produced by a diffuser interface with a specular component and only providing a broad, diffuse scan line profile. By removing the superimposed specular scan lines from the touch signal, the system can more easily use a broad, diffuse scan line profile. Preferably, the diffuse light scattering surface has a specular component of less than 1 %, even more preferably less than 0.1 %. Alternatively, in case the specular component is larger than 0.1 %, the diffuse light scattering element is preferably configured with a surface roughness, e.g. microstructure, to reduce the glossiness.

[0074] The panel 101 can be made of glass, poly(methyl methacrylate) (PMMA) or polycarbonate (PC). The panel 101 can be designed to be overlaid on or integrated into a display device or monitor (not shown). It is conceivable that the panel 101 need not be light transmissive, i.e. the output of the touch need not be presented via the display device through the panel 101, but displayed on another external display or communicated to any other device, processor, memory, etc. The panel 101 can be provided with a shielding layer, e.g. a print, i.e. a cover with ink, to block unwanted ambient light. Thus, the amount of stray light and ambient light reaching the detector 106 can be reduced.

[0075] As used herein, the emitters 105 can be any type of device capable of emitting radiation in a desired wavelength range, such as diode lasers, vertical-cavity surface-emitting lasers (VCSELs), light-emitting diodes (LEDs), incandescent lamps, halogen lamps, etc. The emitters 105 can also be formed by the end of an optical fiber. The emitters 105 can produce light in any wavelength range. The examples below assume that the light is produced in the infrared (IR), i.e., at a wavelength of about 750 nm. Similarly, the detectors 106 can be any device capable of converting light (in the same wavelength range) into an electrical signal, such as photodetectors, CCD devices, CMOS devices, etc.

[0076] With respect to the above discussion, "diffuse reflection" refers to the reflection of light from a surface such that the incident light ray is reflected at multiple angles, rather than just one angle as in "specular reflection." Thus, a diffusely reflecting element will emit light through a large solid angle at each location on the element when illuminated. Diffuse reflection is also referred to as "scattering." The examples described primarily refer to the aforementioned elements in relation to the emitters 105 for clarity of explanation, although it should be understood that corresponding arrangements can be applied to the detectors 106 as well.

[0077] The application has been described above mainly with reference to some embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope and spirit of the application, which is defined and limited only by the appended patent claims.

[0078] For example, the specific arrangement of emitters and detectors explained and discussed above is given merely as an example. The coupling structure of the application is useful in any touch sensing system that operates by transmitting light produced by a plurality of emitters through a panel and detecting changes in received light at a plurality of detectors caused by interaction of the transmitted light at a touch point.

Claims

1. Touch sensing device (100), the touch sensing device comprising: a panel (101) defining a touch surface (102) extending in a plane (103) having a normal axis (104), a plurality of emitters (105) and a plurality of detectors (106) arranged along an outer periphery (107) of the panel, a light guiding portion (108) arranged adjacent to the outer periphery and comprising a light guiding surface (109), wherein the emitters are arranged to emit light (110) and the light guiding surface is arranged to receive the light and guide the light through the touch surface, wherein the panel comprises a back surface (111) opposite the touch surface and the emitters and / or the detectors are arranged opposite the back surface to emit and / or receive light through a passage (112) in a frame element (113) arranged opposite the back surface and extending in a direction (104') of the normal axis, wherein the light guiding surface and the passage are arranged on opposite sides of the panel and overlap in a direction of the plane, whereby the light guiding surface receives light from the emitters or guides light to the detectors through the panel and the passage in the direction of the normal axis.

2. The touch-sensing device of claim 1, wherein, an angle (v) between the light guiding surface and the plane of the touch surface is less than 45 degrees or above 45 degrees.

3. Touch sensing device according to claim 1 or 2, the panel having edges (114) extending between the touch surface and the back surface, the passage extending between a first passage wall (115a) and an opposite second passage wall (115b) in a direction parallel to the plane with a width (dl), the first passage wall being arranged closest to a respective edge (114) of the panel, wherein, the first passage wall extending at an angle (116) towards the direction (104') of the normal axis.

4. The touch-sensing device of any one of claims 1 to 3, wherein, the light guiding surface (109) extending from an edge portion (121) of the light guiding portion arranged closest to the touch surface to a protrusion (117) of the light guiding portion extending in a direction parallel to the plane to shield ambient light or stray light from being reflected into the passage.

5. The touch sensing device of any one of claims 1 to 4, wherein, the emitters and / or the detectors are mounted to a substrate (119), the substrate comprising a chamfered edge (120a) arranged opposite a respective mating surface (120b) of the frame element forming an angle (122) with the normal axis.

6. The touch-sensing device of any one of claims 1 to 5, wherein, the walls (115a, 115b) of the passage comprise a diffusive light scattering surface.

7. The touch-sensing device of any one of claims 1 to 6, wherein, the emitters and / or the detectors are mounted to a substrate (119), wherein a support (123) is attached to the substrate, the support extending in a direction parallel to the plane between a frame wall (124a, 124b) of the frame element (113) and the substrate.

8. The touch-sensing device of any one of claims 1 to 7, wherein, the panel having edges (114) extending between the touch surface and the back surface, wherein the frame element forms a cavity (125), wherein the emitter and / or the detector are mounted to a substrate (119) and the substrate is arranged in the cavity such that the emitter and / or the detector are arranged closer to the respective edge of the panel than the substrate.

9. The touch-sensing device of claim 8, wherein, the cavity (125) extends in a direction parallel to the plane with a width (d2) between a first frame wall (124a) and an opposite second frame wall (124b), the first frame wall being arranged closest to the respective edge (114) of the panel, wherein the substrate is arranged in the cavity such that the emitter and / or the detector are arranged closer to the first frame wall than the substrate.

10. The touch-sensing device of claim 8 or 9, wherein, the substrate extends in a direction (104') of the normal axis with an elongated shape.

11. The touch-sensing device of any one of claims 1 to 10, wherein, the light directing surface is an anodized metal.

12. The touch-sensing device of any one of claims 1 to 11, wherein, the light directing surface is an etched metal, a sandblasted metal, a bead blasted metal or a wire-drawn metal for increasing the surface roughness and diffusely reflecting the light on the touch surface.

13. The touch-sensing device of claim 11 or 12, wherein, the frame element comprises the light directing portion, wherein the frame element is formed of the metal, thereby the light directing surface is an anodized metal surface of the frame element and / or an etched metal surface, a sandblasted metal surface, a bead blasted metal surface or a wire-drawn metal surface of the frame element.

14. The touch-sensing device of claim 13, wherein, the metal surface is recessed towards the touch surface.

15. The touch-sensing device of any one of claims 11 to 14, wherein, the frame element forms a cavity (125) in which the emitter and / or the detector are arranged.

16. The touch-sensing device of any one of claims 1 to 15, wherein, the light directing surface (109) has a surface roughness defined by a slope RMS (Δq) between 0.1 and 0.

25.

17. The touch-sensing device of claim 16, wherein, the light directing surface (109) has a surface roughness defined by a slope RMS (Δq) between 0.13 and 0.

20.

18. The touch-sensing device of any one of claims 1 to 15, wherein, the light directing surface (109) has a surface roughness defined by a slope RMS (Δq) between 0 and 0.

1.

19. The touch-sensing device of any one of claims 1 to 18, wherein, the light directing portion comprises an outer surface (126) opposite the light directing surface, wherein the light directing surface has a higher reflectivity than the outer surface.

20. The touch-sensing device of any one of claims 1-19, wherein, the walls (115a, 115b) of the channel have a higher specular reflectivity than the light directing surface.

21. A method (200) of manufacturing a frame element (113) for a touch sensing device (100), the method comprising: extruding (201) the frame element to form a light directing portion (108) and a cavity (125) adapted to receive a substrate (119) comprising an emitter (105) and / or a detector (106), and milling (202) a wall portion (127) of the cavity to form a channel (112) extending in the direction of a normal axis (104) such that, in use, a light directing surface (109) of the light directing portion receives light from the emitter or directs light to the detector through the channel in the direction of the normal axis, wherein the normal axis extends perpendicular to a plane (103) of a panel (101) defining a touch surface (102) of the touch sensing device when the panel is positioned between the light directing portion and the emitter and / or the detector.

22. The method according to claim 21, comprising etching or bead or grit blasting (2011) the light directing surface.

23. The method according to claim 21 or 22, comprising milling (203) a top portion (128) of the extruded light directing portion such that a height (h) of the light directing portion above the touch surface (102) of a panel (101) is reduced when arranged in the frame element.

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