Patent Application
20080074402
The present invention relates to input systems, and in particular, optical touch systems having relatively reduced bezel dimensions. However, it will be appreciated that the invention is not limited to this particular field of use.
Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of the common general knowledge in the field.
Touch screen input devices or sensors for computers and other consumer electronics devices such as mobile phones, personal digital assistants (PDAs) and hand-held games are highly desirable due to their extreme ease of use. In the past, a variety of approaches have been used to provide touch screen input devices. The most common approach uses a flexible resistive overlay, although the overlay is easily damaged, can cause glare problems, and tends to dim the underlying screen, requiring excess power usage to compensate for such dimming. Resistive devices can also be sensitive to humidity, and the cost of the resistive overlay scales quadratically with perimeter. Another approach is the capacitive touch screen, which also requires an overlay. In this case the overlay is generally more durable, but the glare and dimming problems remain.
In yet another common approach, a matrix of infrared light beams is established in front of a display, with a touch detected by the interruption of one or more of the beams. Such “optical” touch screens have long been known (U.S. Pat. No. 3,478,220; U.S. Pat. No. 3,673,327), with the beams generated by arrays of optical sources such as light emitting diodes (LEDs) and detected by corresponding arrays of detectors (such as phototransistors). They have the advantage of being overlay-free and can function in a variety of ambient light conditions (U.S. Pat. No. 4,988,983), but have a significant cost problem in that they require a large number of source and detector components, as well as supporting electronics. Since the spatial resolution of such systems depends on the number of sources and detectors, this component cost increases with display size and resolution.
An alternative optical touch screen technology, based on integrated optical waveguides, is disclosed in U.S. Pat. No. 6,351,260, U.S. Pat. No. 6,181,842 and U.S. Pat. No. 5,914,709, and in US Patent Application Nos. 2002/0088930 and 2004/0201579, each of which is incorporated herein by reference in its entirety. The basic principle of such a device is shown in
The touch screen sensors are usually two dimensional and rectangular, with two arrays (X, Y) of transmit waveguides 16 along adjacent sides of the screen, and two corresponding arrays of receive waveguides 17 along the other two sides of the screen. As part of the transmit side, in one embodiment a single optical source (such as an LED or a vertical cavity surface emitting laser (VCSEL)) launches light via some form of optical power splitter 18 into a plurality of waveguides that form both the X and Y transmit arrays. The X and Y transmit waveguides are usually arranged on an L shaped substrate, and likewise for the X and Y receive waveguides, so that a single source and a single position-sensitive detector can be used to cover both X and Y dimensions. However in alternative embodiments, a separate source and/or detector may be used for each of the X and Y dimensions. For simplicity,
These prior art devices house the waveguide structures that form the X and Y transmit arrays within a protective bezel that surrounds the screen. As will be appreciated, the bezel width necessarily limits the screen size within a given device, which may be a significant limitation for small devices such as mobile phones. A further problem is that, to minimise the bezel width, the distance between the in-plane lenses and the external VCLs should be minimised, leading to a high magnification optical system that is extremely susceptible to errors in the design, fabrication and placement of the external VCLs.
It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.
According to a first aspect the present invention provides a waveguide structure for a touch screen, wherein the touch screen defines a plane, the waveguide structure having at least one optical waveguide adapted to carry a signal for the touch screen, the waveguide structure being configured such that, in use, the at least one optical waveguide extends entirely below the plane.
The touch screen typically includes an upper portion for receiving user input, and in the preferred embodiment, the upper portion defines the plane of the touch screen. The touch screen also includes a periphery defined by a plurality of sides, and is preferably substantially rectangular in shape.
The signal may comprise an input signal or an output signal and is preferably light having a predetermined wavelength. The wavelength may be in the visible region of the spectrum or the infrared region of the spectrum. Desirably the wavelength is between 700 and 1000 nm.
The waveguide structure preferably includes a plurality of optical waveguides, wherein each optical waveguide extends entirely below the plane.
Preferably the waveguide structure is substantially flexible and formed from polymeric materials. Optimally, the waveguide structure is bendable through at least 90° without suffering mechanical damage. In a particularly preferred embodiment, the waveguide structure comprises a plurality of polymer optical waveguides fabricated on a flexible polymer substrate.
Preferably the waveguide structure extends around at least a portion of the periphery. Optionally the waveguide structure extends around adjacent sides of the periphery. However, in preferred embodiments the waveguide structure extends around the entire periphery.
In preferred embodiments, the waveguide structure is disposed substantially perpendicularly to the plane of the touch screen. However, in other embodiments the waveguide structure extends underneath and substantially parallel to the plane of the touch screen, and preferably lies substantially within the periphery.
The waveguide structure is preferably configured such that, in use, the at least one optical waveguide passes through a maximum of two mutually perpendicular planes.
The waveguide structure may be formed as a substantially rectangular two-dimensional sheet. However, in other embodiments, the waveguide structure is formed as a substantially L-shaped two-dimensional sheet.
In a particular embodiment of the invention the Waveguide structure comprises a plurality of input waveguides adapted to carry an input signal and a plurality of output waveguides adapted to carry an output signal. Preferably the input waveguides are grouped on the waveguide structure to define a transmit section, and the output waveguides are grouped on the waveguide structure to define a receive section. Typically, the input waveguides are referred to as transmit waveguides and the output waveguides referred to as receive waveguides. Each waveguide includes an input portion for receiving an input signal and an output portion for transmitting an output signal. Typically the waveguides are positioned such that the input portions of the transmit waveguides and the output portions of the receive waveguides are disposed on a first side of the waveguide structure, and the output portions of the transmit waveguides and the input portions of the receive waveguides are disposed on a second side of the waveguide structure, wherein the first and second sides are substantially mutually opposed. In this embodiment, the input portions of the transmit waveguides are grouped into an input array, and the output portions of the receive waveguides are grouped into an output array, each array extending along a portion of the first side. However, the output portions of the transmit waveguides and the input portions of the receive waveguides are spaced, preferably substantially evenly spaced, along substantially the entire length of the second side.
In other embodiments, the waveguides are positioned such that the input portions of the transmit waveguides and the output portions of the receive waveguides are disposed on opposite sides of the waveguide structure, and the output portions of the transmit waveguides and the input portions of the receive waveguides are disposed on a common side of the waveguide structure. Preferably the output portions of the transmit waveguides and the input portions of the receive waveguides are spaced, preferably substantially evenly spaced, along substantially the entire length of the common side.
The input array is suitably optically coupleable with a light source and the output array is optically coupleable with a light detector, which is preferably a position-sensitive detector.
In preferred embodiments the output portions of the transmit waveguides and the input portions of the receive waveguides include an integral structure, such as a planar lens. In other embodiments the integral structure may be a planar internally reflective mirror.
Preferably the waveguide structure includes at least one fold line defined by a line of weakness to assist in folding the waveguide structure about the periphery of a touch screen. In alternative embodiments, the fold line may be a printed mark to assist in manual assembly with a touch screen and/or with the optical element. Alternatively, a printed mark may be visible to a machine vision system when the waveguide structure is machine assembled with the touch screen.
According to a second aspect the present invention provides an optical element for a touch screen, wherein the touch screen defines a plane, the optical element comprising:
a first reflective surface; and a connect portion adapted for connection to a waveguide structure having at least one optical waveguide adapted to carry an input or an output signal for the touch screen; the optical element being configured for use with the touch screen such that, in use, the first reflective surface is positioned above the plane to re-direct the signal to and from the waveguide, the connect portion being at least partially below the plane whereby the at least one optical waveguide extends entirely below the plane. The reflective surface may be a mirror adapted for optical communication with the connect portion. The mirror may be plane or arcuate in cross-section and is optionally metallised. However, in a preferred embodiment the first reflective surface is an internally reflective surface.
Preferably, the optical element further includes a body of light transmissive material for transmission of the signal between the connect portion and the first reflective surface, in which case the first reflective surface is an internally reflective surface. More preferably, the internally reflective surface is a totally internally reflective surface. Preferably the first reflective surface is curved thereby to focus the signal in a direction substantially perpendicular to the plane of the touch screen. Alternatively, the first reflective surface may be planar so that it does not focus the signal.
In further aspects, the optical element includes a second reflective surface that, in use, is positioned below the plane of the touch screen. An optical element having a second reflective surface is particularly useful when the waveguide structure extends underneath and substantially parallel to the plane of the touch screen. Preferably, the second reflective surface is an internally reflective surface, more preferably a totally internally reflective surface. The second reflective surface may be curved so as to focus the signal in a direction substantially perpendicular to the plane of the touch screen. Preferably, the second reflective surface is curved in a cylindrical fashion so as to focus a plurality of signals associated with a plurality of optical waveguides. Alternatively, the second reflective surface may be planar.
In preferred embodiments, the optical element is formed as a strip of plastic material substantially transparent to the signal light (eg in the infrared region of the spectrum) and opaque to light at other wavelengths (eg ambient visible light). The optical element is preferably injection moulded or extruded. Preferably, the optical element is substantially rigid.
When formed as a strip of plastic material, the first reflective surface of the optical element is preferably arcuate in cross section thereby to focus a plurality of signals associated with a plurality of optical waveguides.
In the preferred embodiments where the optical element further includes a body of light transmissive material between the connect portion and the first reflective surface, the optical element includes an optical surface through which light passes as it transits the touch screen. In some embodiments, this optical surface will be planar. Alternatively, it may be arcuate in cross section to form a lens portion thereby to focus the signal in a direction substantially perpendicular to the plane of the touch screen. Preferably, the optical surface is curved in a cylindrical fashion so as to focus a plurality of signals associated with a plurality of optical waveguides. Irrespective of the precise shape of the optical surface, the optical element is preferably shaped such that, in use, the exterior angle between the touch screen and the optical surface is greater than or equal to 90°. In related aspects, the optical element includes a recess such that the optical element is attachable to the touch screen. Further, the waveguide structure may be fixedly attached to the optical element by, for example, gluing.
According to a third aspect the present invention provides an apparatus for use in an input device, comprising: a touch screen defining a plane, and having a periphery defined by a plurality of sides and an upper portion for receiving user input; a waveguide structure having at least one optical waveguide adapted to carry an input or an output signal for the touch screen; and
one or more optical elements extending along at least a portion of the periphery and in optical communication with respective waveguides, each optical element extending from a position below the plane to a position above the plane such that, in use, each optical element transmits the input or the output signal to or from the upper portion to respective waveguides extending entirely below the plane.
According to a fourth aspect the present invention provides a method of transmitting input and output signals for a touch screen device, the touch screen defining a plane and having an upper portion for receiving user input and a periphery, the method of comprising: providing at least one waveguide structure having at least one optical waveguide adapted to carry an input or an output signal for a touch screen, the at least one optical waveguide extending entirely below the plane; providing one or more optical elements along at least a portion of the periphery; and optically coupling the waveguide structure with a respective optical element such that, in use, each optical element transmits the input or the output signal to or from the upper portion to a respective waveguide extending entirely below the plane. Preferably each optical waveguide extends entirely below the plane.
According to a fifth aspect the present invention provides a method of reducing bezel width in a touch screen device, the touch screen defining a plane and having an upper portion for receiving user input and a periphery, the method comprising: providing at least one waveguide structure having at least one optical waveguide adapted to carry an input or an output signal for the touch screen; providing one or more optical elements along at least a portion of the periphery; and optically coupling the at least one optical waveguide with a respective optical element such that, in use, each optical element transmits the input or the output signal to or from the at least one optical waveguide; wherein the at least one optical waveguide is terminated at a position below the plane, and wherein the optical elements extend from above the touch screen plane to a position below the touch screen plane.
Unless the context clearly requires otherwise, throughout the description and the claims, the words ‘comprise’, ‘comprising’, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”.
Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:
FIGS. 19(a) and 19(b) show plan and side views of a typical prior art assembly of a transmit waveguide and an external vertical collimating lens.
Referring initially to FIGS. 2 to 9, a waveguide structure 20 for a touch screen 21 is formed as a substantially two-dimensional sheet comprising a plurality of waveguides 22 adapted to carry input signals or output signals for the touch screen 21. The touch screen 21 is substantially rectangular in shape and includes an upper portion 23 that defines a plane 24 for receiving user input, such as the touch of a finger or a stylus.
In the various embodiments as shown in FIGS. 2 to 4, the substantially rectangular waveguide structure 20 is formed from a resilient polymeric material that is substantially flexible. Preferably the waveguide structure 20 is repeatably bendable through at least 90° without being mechanically damaged. For example,
The waveguide structure 20 preferably comprises a plurality of optical waveguides 22 comprising a photo-curable polymer material fabricated on a flexible polymer substrate, for example by a method disclosed in U.S. Patent Application No. 60/796,722 entitled ‘Methods for fabricating polymer optical waveguides on large area panels’, incorporated herein by reference in its entirety. Briefly, this document describes methods for fabricating polymer optical waveguides comprising a three layer structure, wherein at least one of the optical layers is deposited by a two-stage deposition process whereby the second step is a spinning process. The invention disclosed in U.S. 60/796,722 is of particular relevance to the volume production of polymer optical waveguides on large area substrates.
As shown in
In other waveguide substrate configurations, the waveguide structure 20 is a two-dimensional sheet that extends underneath and substantially parallel to the plane 24 of touch screen 21. One such configuration comprises four waveguide structures 20, each extending along an edge of the touch screen 21. However, in preferred configurations as shown in
Referring again to the embodiment as shown in
Referring again to the embodiments as shown in
The input array 36 is optically coupleable with a light source 38 for supplying a light signal and the output array 37 is optically coupleable with a suitable light detector 39. The light has a predetermined wavelength that may, for example, be in the infrared region of the spectrum, preferably between 700 and 1000 nm. Alternatively, the predetermined wavelength may be in the visible region of the spectrum.
Referring in particular to the embodiment as shown in
Additionally, waveguide structures can be overlapped to ensure that the entire periphery 25 of a touch screen 21 is accessible to either the transmit section 28 or receive section 29 of the waveguide structure 20. For example, the waveguide structures shown in
In related embodiments, as shown in
In the waveguide structures 20 shown in FIGS. 2 to 4, the transmit waveguides 26 and receive waveguides 27 are provided on a single substantially rectangular strip designed to be folded around the entire periphery of the touch screen. It will be appreciated that the larger the touch screen, the longer the rectangular strip needs to be, however this will be limited by the size of the substrate used for waveguide fabrication. The waveguide fabrication techniques disclosed in U.S. Patent Application No. 60/796,722 will clearly be applicable to this situation. If substrate size is a limitation it is of course possible to fabricate the transmit waveguides and receive waveguides on separate substantially rectangular strips, each of which would be folded around two sides of the periphery, for example as shown in
Irrespective of whether the transmit waveguides and receive waveguides are fabricated on separate strips or a single strip, a key advantage of fabricating the waveguides on rectangular strips, as shown in
As discussed above, the waveguide structure 20 is substantially flexible for assisting in folding around the periphery 25 of a touch screen 21. In other embodiments, the waveguide structure 20 includes at least one fold line 41 defined by a line of weakness to assist in the installation around the touch screen 21. In alternative embodiments, the fold line 41 is a printed mark visible to a machine vision system when the waveguide structure 20 is machine assembled with a touch screen 21 and/or with the optical element 42. Alternatively a printed mark may assist with manual assembly of the waveguide structure 20 with a touch screen 21 and/or with an optical element 42.
Turning now to FIGS. 10 to 15, an optical element 42 for a touch screen 21 is shown comprising a first reflective surface 43 for reflecting a light signal 44 in a direction substantially parallel to the plane 24, and a connect portion 45 adapted for connection to the waveguide structure 20. The optical element 42 is configured for use with a touch screen 21 such that, in use, the first reflective surface 43 is positioned above the plane 24 of a touch screen 21 to re-direct a light signal 44 to or from the waveguide structure 20. Preferably the connect portion 45 is at least partially below the plane 24.
The optical element 42 further includes a body of light transmissive material 46 for transmission of a light signal 44 between the connect portion 45 and the first reflective surface 43.
In other embodiments, as shown in
It will be appreciated that optical element 42 could be constructed such that one or both of the reflective surfaces are externally reflective (ie conventional) mirrors rather than internally reflective surfaces. However a construction where optical element 42 has internally reflective surfaces, as shown for example in FIGS. 10 to 15, is preferred for robustness and ease of manufacture (by injection moulding for example). Further, an externally reflective mirror would need to be metallised, whereas the internally reflective surfaces may not need to be metallised provided the condition for total internal reflection is met. Those skilled in the art will understand that this can be ensured by appropriate design of the optical element.
As shown in
First internally reflective surface 43 may be curved thereby to focus a light signal 44 in a direction substantially perpendicular to the plane 24 of touch screen 21, as shown for example in
As shown in FIGS. 10 to 15, the optical element 42 has an optical surface 48 through which light 44 passes as it transits a touch screen 21. In some embodiments, for example as shown in
Preferably the optical element 42 includes a recess 50 such that the optical element 42 is attachable to a touch screen 21. In certain embodiments the optical element 42 is configured as a single piece having physical dimensions matching the periphery 25 of a touch screen 21 such that the optical element 42 is adapted to “clip” onto a touch screen 21. Alternatively, the optical element 42 can be glued onto a touch screen 21. In other embodiments the optical element 42 may be configured as two L-shaped pieces each adapted to clip around two adjacent sides of a touch screen 21, or as four straight pieces each adapted to be attached to one side of a touch screen 21 (as shown in
The waveguide structure 20 may be fixedly attached to the optical element 42 by gluing. However, it will be appreciated that any method of attachment that provides sufficient and stable optical communication between the waveguides 22 and optical element 42 will be suitable.
A particularly preferred design for optical element 42 is shown in
Referring now to
In one example, the present invention includes a method of transmitting input and output signals for a touch screen device. The method comprises providing a waveguide structure 20, providing one or more optical elements 42, and then optically coupling the waveguide structure 20 with a respective optical element 42 such that, in use, each optical element 42 transmits input or output signals to or from the upper portion 23 of a touch screen 21 to a respective waveguide 22 extending entirely below the plane 24 of a touch screen 21.
In a further example, the present invention includes a method of reducing the bezel width in a touch screen device. The method comprises providing a waveguide structure 20, providing one or more optical elements 42, and then optically coupling the waveguide structure 20 with a respective optical element 42 such that, in use, each said optical element 42 transmits an input or output signal to or from the waveguide structure 20. The optical elements 42 extend from above the touch screen 21 to a position below a touch screen 21 and the waveguides 22 are terminated at a position below the plane 24.
Referring to
In yet a further example, the present invention includes a method of reducing the tolerance required of an optical element used to provide focussing of optical signals in a direction substantially perpendicular to the plane of a touch screen. To illustrate, FIGS. 19(a) and 19(b) show plan and side views of a typical prior art assembly of an output portion 33 of a transmit waveguide 26 having an external vertical collimating lens (VCL) 70, wherein transmit waveguide 26 and VCL 70 are mounted on a common base 71. An essentially identical arrangement is normally present on the receive side. Typically, transmit waveguide 26 comprises a substrate 72, a lower cladding layer 73, a core layer 74 and an upper cladding layer 75, with core layer 74 terminating with an integrated planar lens 40 that collimates light signal 44 in the plane of the touch screen. Note that substrate 72, lower cladding layer 73 and upper cladding layer 75 have been omitted from
It will be appreciated that gap 77 between end face 76 of planar lens 40 and curved face 78 of VCL 70 contributes to the overall bezel width in a prior art device, and should ideally be minimised. However this requires VCL 70 to be a relatively powerful lens, ie to have a small radius of curvature. Those skilled in the art of micro-optics will understand that such a high magnification optical system is extremely susceptible to errors in the design, manufacture and placement of VCL 70.
The present invention on the other hand may provide such ‘out of plane’ focussing via optical element 42, several embodiments of which are shown in FIGS. 10 to 15. For example, ‘out of plane’ focusing may be provided by lens portion 49 and/or first reflective surface 43 and/or second reflective surface 47 (if present). Particularly notable are the embodiments shown in
It will be appreciated that the illustrated apparatus of the present invention provides many advantages over prior art devices, including but not limited to the following:
Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.
| Number | Date | Country | Kind |
|---|---|---|---|
| AU 2006905255 | Sep 2006 | AU | national |
