U.S. patent application number 14/604502 was filed with the patent office on 2015-05-21 for touch-sensing display panel.
The applicant listed for this patent is FlatFrog Laboratories AB. Invention is credited to Ola WASSVIK.
Application Number | 20150138161 14/604502 |
Document ID | / |
Family ID | 48426316 |
Filed Date | 2015-05-21 |
United States Patent
Application |
20150138161 |
Kind Code |
A1 |
WASSVIK; Ola |
May 21, 2015 |
TOUCH-SENSING DISPLAY PANEL
Abstract
A touch-sensing display panel, comprising a plurality of
image-forming pixel elements; a planar light guide with a first
refractive index, having a front surface forming a touch-sensing
region and an opposite rear surface facing the pixel elements; a
plurality of light emitters arranged at a peripheral region of the
panel to emit light into the light guide for propagation therein
through total internal reflection; a plurality of light detectors
disposed at the peripheral region for receiving light from the
light guide; and an optical layer disposed at the rear surface of
the light guide to cover a plurality of the image-forming pixel
elements in at least a central region of the panel, wherein said
optical layer is configured to reflect at least a part of the light
from the emitters impinging thereon from within the light
guide.
Inventors: |
WASSVIK; Ola; (Brosarp,
SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FlatFrog Laboratories AB |
Lund |
|
SE |
|
|
Family ID: |
48426316 |
Appl. No.: |
14/604502 |
Filed: |
January 23, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13742958 |
Jan 16, 2013 |
8963886 |
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14604502 |
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13548749 |
Jul 13, 2012 |
8884900 |
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13742958 |
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61507164 |
Jul 13, 2011 |
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Current U.S.
Class: |
345/175 |
Current CPC
Class: |
G02F 1/13338 20130101;
G06F 3/0428 20130101; G06F 3/04166 20190501; G06F 3/0421 20130101;
G06F 3/042 20130101; G06F 2203/04109 20130101 |
Class at
Publication: |
345/175 |
International
Class: |
G06F 3/042 20060101
G06F003/042; G06F 3/041 20060101 G06F003/041; G02F 1/1333 20060101
G02F001/1333 |
Claims
1. A touch-sensing display panel, comprising: a plurality of
image-forming pixel elements; a planar light guide with a first
refractive index, having a front surface forming a touch-sensing
region and an opposite rear surface facing the pixel elements; a
plurality of light emitters arranged at a peripheral region of the
panel to emit light into the light guide for propagation therein
through total internal reflection in at least the front surface; a
plurality of light detectors disposed at the peripheral region for
receiving light from the light guide; an optical layer disposed at
the rear surface of the light guide to cover a plurality of the
image-forming pixel elements in at least a central region of the
panel, wherein said optical layer is configured to reflect at least
a part of the light from the emitters impinging thereon from within
the light guide, and incoupling structures arranged at a peripheral
region of the light guide for directing light from the emitters
into the light guide.
2.-28. (canceled)
29. The touch-sensing display panel of claim 1, wherein said
optical layer has a second refractive index which is lower than the
first refractive index.
30. The touch-sensing display panel of claim 29, wherein an
extension portion of the optical layer is disposed over the light
emitters, said extension portion having a third refractive index
which is higher than the second refractive index.
31. The touch-sensing display panel of claim 30, wherein the
extension portion of the optical layer covers said peripheral
region.
32. The touch-sensing display panel of claim 1, wherein the light
emitters are coupled to emit light into the light guide, which
light bypasses said main portion of the optical layer.
33. The touch-sensing display panel of claim 1, wherein said light
emitters and said image-forming pixel elements are OLED
elements.
34. The touch-sensing display panel of claim 1, wherein the light
emitters are integrated with the image-forming pixel elements in
the panel.
35. The touch-sensing display panel of claim 1, wherein said light
emitters are disposed behind the image-forming pixel elements, and
configured to emit light through the image-forming pixel elements
and into the light guide.
36. The touch-sensing display panel of claim 30, wherein the
extension portion of the optical layer is also disposed over the
light detectors.
37. The touch-sensing display panel of claim 1, wherein said light
detectors are coupled to receive light from the light guide, which
light bypasses said main portion of the optical layer.
38. The touch-sensing display panel of claim 1, wherein said light
detectors are OLED elements.
39. The touch-sensing display panel of claim 1, wherein the light
detectors are integrated with the image-forming pixel elements in
the panel.
40. The touch-sensing display panel of claim 1, wherein said light
detectors and said image-forming pixel elements are stacked OLEDs,
wherein the light detectors are configured to detect light from the
light guide through the image-forming pixel elements.
41. The touch-sensing display panel of claim 1, further comprising
a light output mechanism arranged to lead out light from the light
guide to the light detectors.
42. The touch-sensing display panel of claim 1, wherein said light
guide is a substrate of the panel on which said pixel elements are
formed, and said light guide is sealed at an edge portion to a
cover disposed on the opposing side of the pixel elements.
43. The touch-sensing display panel of claim 1, wherein said pixel
elements are formed on a substrate, which is sealed at an edge
portion to a said light guide cover, which is disposed on the
opposing side of the pixel elements.
44. The touch-sensing display panel of claim 1, comprising an LCD
unit, of which a central region is controlled to operate as said
image-forming pixels and a peripheral region is controlled to pass
light from the light guide to the detectors.
45. The touch-sensing display panel of claim 1, comprising an LCD
unit including a backlight, wherein the LCD unit is controlled to
emulate said emitters by passing light from the backlight through
selected portions of the LCD unit.
46. An electronic device comprising the touch-sensing display panel
of claim 1, and a controller for causing the image-forming elements
to display information content within at least part of the touch
surface while causing the touch-sensor elements to provide touch
sensitivity within said at least part of the touch surface.
47. The touch-sensing display panel of claim 31, wherein the
incoupling structures are included in the extension portion of the
optical layer.
Description
TECHNICAL FIELD
[0001] The present invention relates to touch sensing systems and
especially to display devices that offer touch sensitivity.
BACKGROUND ART
[0002] Display devices with touch sensitivity are used today in a
wide variety of applications such as touch pads in laptop
computers, all-in-one computers, mobile phones and other hand-held
devices, etc. It is often a desire to provide these electronic
devices with a relatively large touch sensing display and still let
the devices be small and thin.
[0003] There are numerous techniques for providing a display device
with touch sensitivity, e.g. by adding layers of resistive wire
grids or layers for capacitive touch-sensing or by integrating
detectors in the display device. The major drawback of these
techniques is that they reduce the optical quality of the display
device, by reducing the amount of light emitted from the display or
by reducing the number of active pixels of the display device.
[0004] U.S. Pat. No. 7,432,893 discloses a touch sensing system
that uses FTIR (frustrated total internal reflection) to detect
touching objects. Light emitted by a light source is coupled into a
transparent light guide by a prism, then propagates inside the
light guide by total internal reflection where after the
transmitted light is received at an array of light detection
points. The light may be disturbed (frustrated) by an object
touching the light guide, whereby a decrease in transmitted light
is sensed at certain light detection points. Providing a display
device with this touch sensing system would add an undesired
thickness and complexity to the display device.
[0005] WO2009/077962 also discloses a touch sensing system that
uses FTIR to detect touching objects. Disclosed is a light guide
with a tomograph having signal flow ports adjacent the light guide,
the flow ports being arrayed around the border of the light guide.
Light is emitted into the light guide by the flow ports and
propagates inside the light guide by total internal reflection
where after the transmitted light is detected at a plurality of
flow ports. The light may be disturbed by an object touching the
light guide. Providing a display device with this touch sensing
system would add an undesired thickness and complexity to the
display device.
[0006] US20040140960 shows a system which makes use of a different
type och touch-sensing mechanism, namely by allowing beams of light
to pass over the top surface of an OLED display through a prism or
mirror system, and detecting obstruction of those beams. This
document also proposes to use OLEDs for the light emitters. Such a
design will be comparatively thick and also sensitive to
contamination at the edges of the light-deflecting mechanism.
[0007] US20080150848 discloses an OLED display combined with touch
sensor. In this disclosure, a separate waveguide in which infrared
(IR) light propagates by TIR is placed over the display light
guide, and throughout the surface of the display light guide,
IR-sensing OLED elements are dispersed. Upon touching the
waveguide, some light will be scattered downwards and detected by
the underlying OLED sensor element. Since this solution requires IR
sensors throughout the light guide, the light sensors may occupy a
significant part of the display surface, hence affecting the
imaging capability. The stacked solution also adds thickness to the
design.
SUMMARY
[0008] It is an object of the invention to at least partly overcome
one or more of the above-identified limitations of the prior
art.
[0009] Another objective is to reduce the required thickness for
providing touch sensitivity to a display device.
[0010] One or more of these objects, as well as further objects
that may appear from the description below, are at least partly
achieved by means of a touch-sensing display apparatus and an
electronic device according to the independent claims, embodiments
thereof being defined by the dependent claims.
[0011] A first aspect of the invention is a touch-sensing display
panel, comprising a plurality of image-forming pixel elements; a
planar light guide with a first refractive index, having a front
surface forming a touch-sensing region and an opposite rear surface
facing the pixel elements; a plurality of light emitters arranged
at a peripheral region of the panel to emit light into the light
guide for propagation therein through total internal reflection in
at least the front surface; a plurality of light detectors disposed
at the peripheral region for receiving light from the light guide;
and an optical layer disposed at the rear surface of the light
guide to cover a plurality of the image-forming pixel elements in
at least a central region of the panel, wherein said optical layer
is configured to reflect at least a part of the light from the
emitters impinging thereon from within the light guide.
[0012] In one embodiment said optical layer has a second refractive
index which is lower than the first refractive index.
[0013] In one embodiment an extension portion of the optical layer
is disposed over the light emitters, said extension portion having
a third refractive index which is higher than the second refractive
index.
[0014] In one embodiment the third refractive index is equal to or
higher than the first refractive index.
[0015] In one embodiment the extension portion of the optical layer
covers said peripheral region.
[0016] In one embodiment the light emitters are coupled to emit
light into the light guide, which light bypasses said main portion
of the optical layer.
[0017] In one embodiment said light emitters and said image-forming
pixel elements are OLED elements.
[0018] In one embodiment the light emitters are integrated with the
image-forming pixel elements in the panel.
[0019] In one embodiment said light emitters are disposed behind
one of the image-forming pixel elements, and configured to emit
light through the image-forming pixel elements and into the light
guide.
[0020] In one embodiment the extension portion of the optical layer
is also disposed over the light detectors.
[0021] In one embodiment said light detectors are coupled to
receive light from the light guide, which light bypasses said main
portion of the optical layer.
[0022] In one embodiment said light detectors are OLED
elements.
[0023] In one embodiment the light detectors are integrated with
the image-forming pixel elements in the panel.
[0024] In one embodiment the light detectors are functionally
arranged in a number of detector subsets, wherein the detectors of
one subset are configured to operate as one larger area light
detector.
[0025] In one embodiment said light detectors and said
image-forming pixel elements are stacked OLEDs, wherein the light
detectors are configured to detect light from the light guide
through the image-forming pixel elements.
[0026] In one embodiment at least one of said light detectors is
disposed behind a plurality of the image-forming pixel
elements.
[0027] In one embodiment the touch-sensing display panel further
comprises a light output mechanism arranged to lead out light from
the light guide to the light detectors.
[0028] In one embodiment said light guide is a substrate of the
panel on which said pixel elements are formed, and said light guide
is sealed at an edge portion to a cover disposed on the opposing
side of the pixel elements.
[0029] In one embodiment said pixel elements are formed on a
substrate, which is sealed at an edge portion to a said light guide
cover, which is disposed on the opposing side of the pixel
elements.
[0030] In one embodiment said image forming pixel elements are
configured to operate in the visible range, whereas the emitters
and detectors are configured to operate in the IR range.
[0031] In one embodiment a grid of propagation paths is defined
across the touch-sensing region between pairs of light emitters and
light detectors.
[0032] In one embodiment the touch-sensing display panel comprises
an LCD unit, of which a central region is controlled to operate as
said image-forming pixels and a peripheral region is controlled to
pass light from the light guide to the detectors.
[0033] In one embodiment the touch-sensing display panel comprises
LCD unit including a backlight, wherein the LCD unit is controlled
to emulate said emitters by passing light from the backlight
through selected portions of the LCD unit.
[0034] According to a second aspect, the invention relates to an
electronic device comprising the touch-sensing display panel of any
preceding claim, and a controller for causing the image-forming
elements to display information content within at least part of the
touch surface while causing the touch-sensor elements to provide
touch sensitivity within said at least part of the touch
surface.
[0035] According to a third aspect, the invention relates to a
method of producing a touch-sensing display panel, comprising the
steps of:
[0036] providing a transparent substrate with a first refractive
index;
[0037] providing an optical layer on a rear surface of the
substrate, with a second refractive index which is lower than the
first refractive index at a central region;
[0038] providing a matrix of pixels at the rear surface over the
central region and over a peripheral region;
[0039] providing a cover sheet over the pixel matrix; and
[0040] sealing the cover sheet to the substrate.
[0041] According to a fourth aspect, the invention relates to a
method of producing a touch-sensing display panel, comprising the
steps of:
[0042] providing a carrier sheet;
[0043] providing a matrix of pixels on the carrier sheet;
[0044] providing a transparent substrate with a first refractive
index over the pixels, with an intermediate optical layer with a
second refractive index which is lower than the first refractive
index at central region of the substrate within a peripheral
region;
[0045] sealing the transparent substrate to the carrier sheet.
[0046] In one embodiment, the method comprises the steps of:
[0047] connecting a plurality of pixels in at least the central
region to a control circuit configured to drive them to act as
image-forming pixel elements;
[0048] connecting at least one pixel in the peripheral region to a
control circuit configured to drive them to emit light into the
transparent substrate for propagation by TIR therein; and
[0049] connecting at least one detector in the peripheral region to
a control circuit configured to drive it to detect light from the
transparent substrate, emanating from the emitter.
[0050] In one embodiment said pixels are OLEDs.
BRIEF DESCRIPTION OF DRAWINGS
[0051] Embodiments of the invention will now be described in more
detail with reference to the accompanying schematic drawings.
[0052] FIG. 1 is a side view of an object in contact with a light
transmissive light guide to illustrated the use of FTIR for touch
sensing.
[0053] FIGS. 2A-2B show a top plan and a side view of an embodiment
of the invention.
[0054] FIG. 3 is a top plan view of an embodiment with one
activated emitter.
[0055] FIG. 4 is a side section view of an embodiment including an
OLED display unit.
[0056] FIG. 5 is a perspective view of a cutout corner portion of
an embodiment of FIG. 4
[0057] FIG. 6 is a side section view of variant of the embodiment
of FIG. 4.
[0058] FIG. 7 is a perspective view of a cutout corner portion of
an embodiment of FIG. 6
[0059] FIG. 8 is a top plan view of an embodiment with plural
grouped detectors.
[0060] FIGS. 9-10 are a side section views of other variants of the
embodiment of FIG. 4.
[0061] FIGS. 11-12 are flow charts of two embodiments of methods
for providing a touch-sensing display panel.
[0062] FIG. 13 is a section view of a touch-sensing display
apparatus according to an embodiment.
[0063] FIG. 14 is a flow chart of an additional method to the
methods of FIGS. 11-12.
[0064] FIG. 15 is a section view of another embodiment of the
invention.
[0065] FIG. 16 is a section view of an embodiment including a
TFT-LCD display unit.
[0066] FIG. 17 is a perspective view of a corner portion of a
TFT-TCD embodiment.
[0067] FIG. 18 is a top plan view of a backlight design for use in
the TFT-TCD embodiment of FIG. 17.
[0068] FIG. 19 shows a perspective view of a sandwiched embodiment
of the backlight design of FIG. 18.
[0069] FIG. 20 shows a perspective view of an integrated embodiment
of the backlight design of FIG. 18.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
[0070] The present invention relates to the use of optical
techniques, specifically FTIR, for providing touch sensitivity to a
display apparatus. More specifically, the invention provides a
truly integrated touch-sensing display panel 1, operating by means
of FTIR. Example embodiments are mainly presented in relation to
OLED displays but also to LCD, and throughout the description the
same reference numerals are used to identify corresponding
elements.
[0071] FIG. 1 illustrates the operating principle of an
touch-sensing FTIR system. In the side view of FIG. 1, a beam of
light is propagated by total internal reflection (TIR) inside a
planar (two-dimensional) light guide 2. The light guide 2 comprises
opposing surfaces 3, 4 which define a respective boundary surface
of the light guide 2. Each boundary surface 3, 4 reflects light
that impinges on the boundary surface from within the light guide 2
at an angle that exceeds the so-called critical angle, as is
well-known to the skilled person. When an object 5 is brought
sufficiently close to one of the boundary surfaces (here, the top
surface 3), part of the beam may be scattered by the object 5, part
of the beam may be absorbed by the object 5, and part of the beam
may continue to propagate in the light guide by TIR in the incoming
direction. Thus, when the object 5 touches the top surface 3, which
forms a "touch surface", the total internal reflection is
frustrated and the energy of the transmitted light is decreased, as
indicated by the thinned lines to the right of the object 5. This
phenomenon is known as FTIR (Frustrated Total Internal Reflection)
and a corresponding touch-sensing device may be referred to as an
"FTIR system".
[0072] Although not shown in FIG. 1, the FTIR system typically
includes an arrangement of emitters and detectors, which are
distributed along the peripheral region of the touch surface 3.
Light from an emitter is introduced into the light guide 2 and
propagates by TIR to one or more detectors. Each pair of an emitter
and a detector defines a "detection line", which corresponds to the
propagation path from the emitter to the detector. Any object that
touches the touch surface along the extent of the detection line
will thus decrease or attenuate the amount of light received by the
detector. The emitters and detectors are typically arranged to
define a grid of intersecting detection lines on the touch surface,
whereby each touching object is likely to cause an attenuation of
several non-parallel detection lines.
[0073] The arrangement of detectors is electrically connected to a
signal processor, which acquires and processes an output signal
from the arrangement. The output signal is indicative of the power
of transmitted light at each detector. The signal processor may be
configured to process the output signal for extraction of touch
data, such as a position (e.g. x, y coordinates), a shape or an
area of each touching object.
[0074] While FIG. 1 illustrates the working principle of FTIR touch
as such, the invention relates to a touch-sensing display panel in
which an FTIR touch-sensing mechanism is truly integrated with a
display, as will be shown with reference to the subsequent
drawings.
[0075] FIG. 2A is a top plan view and FIG. 2B is a side view of a
touch-sensing display light guide 1 according to an embodiment of
the invention. The touch-sensing display light guide 1 is
implemented as a combination of a light transmissive light guide 2
that defines a front touch surface 3, and a dual-function display
pixel matrix 6 which is configured to both display images through
the front surface 3 and provide touch sensitivity to the front
surface 3 via FTIR.
[0076] As seen in the plan view of FIG. 2A, a plurality of emitters
7 and detectors 8 (collectively referred to as "touch-sensor
elements") are arranged in interleaved fashion underneath a
peripheral region of the light guide 2. It should be noted, though,
that interleaved arrangement is merely one example of positioning
the emitters 7 and detectors. Another example may be to arrange
emitters along two sides, and detectors along the other two sides,
of the panel 1. In the drawings, for illustrative purposes only,
emitters 7 and detectors 8 are represented by circles and
rectangles, respectively. Furthermore, a center region of the light
guide 2 is aligned with a matrix of image-forming elements or
picture elements ("pixels" or "pixel elements") 10 that define a
display area for displaying visual images in monochrome or color.
The pixels 10, which are indicated as a matrix of square elements
in FIG. 2A, may be formed by any available integrated display
technology, including but not limited to OLED (Organic
Light-Emitting Diode), PLED (Polymer Light-Emitting Diode), LED
(Light Emitting Diode), LCD (Liquid Crystal Display) with internal
illumination ("backlighting"), TFT-LCD (Thin Film Transistor Liquid
Crystal Display), ELD (Electroluminescent Display), etc. Below,
embodiments of the invention will be further exemplified mainly
with respect to OLED, but also to LCD.
[0077] Embodiments of the invention are based on the insight that
the emitters 7 and detectors 8 may be integrated into the display
unit 6, and preferably be formed by the same technology as used for
producing images in the display area. Furthermore, the transparent
display cover, which covers the pixel elements, is also used as a
light guide. As such, various embodiments of the invention may be
realized with no addition of thickness or bulkiness at all. As used
herein, an "integrated" emitter/detector 7, 8 is to be construed as
an emitter/detector 7, 8 that is integrally formed on or in a
substrate, which typically is a composite substrate comprising a
plurality of layers. In FIG. 2B, the integration is indicated by
dashed lines indicating that the display unit 6 is functionally
(not physically) separated into a peripheral region 11 with
emitters 7 and detectors 8 and a center region 12 with pixels 10,
where the emitters 7, detectors 8 and pixels 10 are integrally
formed in a common substrate. Each emitter 7 is configured to
generate a cone of light in any suitable wavelength region. In one
embodiment, the emitter 7 generates light that is invisible to the
human eye, preferably in the infrared (IR) or possibly in the
ultraviolet (UV) region. Each detector 8 is configured to be
responsive to the light emitted by emitters 7.
[0078] Compared to the prior art as described in the background
section, embodiments of the invention make is possible to provide
touch sensitivity to a display apparatus essentially without adding
to the thickness of the display apparatus. Furthermore, the
manufacturing cost may be reduced since there is no need for a
separate mounting operation for attaching emitters 7 and detectors
8. As will be further exemplified below, the emitters/detectors 7,
8 may be formed from functional structures also present in the
display unit for the operation of the pixels 10. This means that
the emitters 7 and detectors 8 may be manufactured by the same or a
similar process as the pixels 10, whereby the added manufacturing
cost may be minimal. It is also to be noted that the number of
emitters 7 and detectors 8 that need to be added is comparatively
small compared to the number of pixels of a typical display
apparatus. For example, a 3.5'' display may be provided with about
10-10.sup.2 emitters and detectors, while the number of pixels is
typically in the order of about 10.sup.5-10.sup.6. Still further,
the touch sensitivity may be added without impairing the quality of
images displayed in the display area, since the need to add
touch-sensing layer(s) to the display area or integrate light
detectors among the pixels within the display area is obviated.
[0079] Furthermore, by integrating the emitters/detectors 7, 8 at
the peripheral region 11 of the display unit 6, it is possible to
omit separate contacting of the emitters/detectors 7, 8. Instead,
they may be contacted and electronically controlled in the same way
as the pixels 10. For example, a data bus structure or an
electronics backplane for supplying control signals to the pixels
10, to selectively control the light emitted by the pixels 10, may
also be used to supply control signals to the individual emitters 7
and detectors 8 and/or to retrieve output signals from the
individual detectors 8.
[0080] FIG. 2A indicates that the peripheral region 11 contains
only emitters 7 and detectors 8, and thus is free of pixels 10.
However, it is certainly possible to include pixels 10 also in the
peripheral region 11, if desired, as will be described further
below.
[0081] FIG. 3 is a top plan view to further illustrate the
operation of the touch-sensing display light guide 1. For reasons
of clarity, the pixels have been omitted. As shown, one emitter 7
is activated to emit an expanding beam of light. The emitted beam,
or at least part thereof, is coupled into the light guide 2 such
that it propagates by TIR across the touch surface 3, while
expanding in the plane of the light guide 2 away from the emitter 7
(indicated by the hatched area). Such a beam is denoted a "fan
beam" herein. Thus, each fan beam diverges from an entry or
incoupling site, as seen on a top plan view. Downstream of the
touch surface 3, the propagating light is coupled out of the light
guide 2 and received by a subset of the detectors 8. As noted
above, a detection line is formed between the emitter 7 and each of
the detectors 8 that receive the fan beam. It is realized that a
large number of detection lines may be generated by activating each
of the emitters 7 and measuring the power of received light at the
detectors 8 for each emitter 7. Depending on implementation, the
emitters 7 may be activated in sequence or concurrently, e.g. by
implementing the coding scheme disclosed in WO2010/064983.
[0082] Reverting to FIGS. 2A-2B, the display pixel matrix 6 may be
an optoelectronic device that makes use of organic materials for
defining the pixels 10, emitters 7 and detectors 8. Examples of
organic optoelectronic devices include organic light emitting
devices (OLEDs), organic phototransistors, organic photovoltaic
cells, and organic photodetectors. For further details regarding
the structure and manufacture of organic optoelectronic devices,
reference is made to WO2011/068761 and citations therein, all of
which are incorporated herein by reference.
[0083] In the following, it is assumed that the display pixel
matrix 6 in FIGS. 2A-2B is based on OLEDs. The display device 6
comprises a rear electrode (e.g. an anode) 15, and a front
electrode (e.g. a cathode) 16, and an intermediate organic
structure 17, which may be formed by one or plural organic layers,
as is known in the art. The front electrode layer 16 is transparent
and may e.g. be made of indium tin oxide (ITO). The pixels 10 of
the display area may be defined by patterning of the electrode
layers 15, 16, and optionally by patterning of the organic
structure 17. Each pixel 10 may include one or more sub-pixels (not
shown), which may be formed by selective doping to generate
different light emissive properties of the different sub-pixels,
e.g. such that the sub-pixels emit red, green and blue light,
respectively. Different designs of a combined thin film transistor
(TFT) structure and OLED pixels are shown in US20080150848, which
is incorporated herein by reference.
[0084] The emitters 7 and detectors 8 in the peripheral region 11
may also be defined by patterning of the electrode layers 15, 16
and/or by patterning of the organic structure 17. It is well-known
that junction diodes, such as LEDs and OLEDs, are operable as both
emitters and detectors by application of proper control voltages to
the junction diodes. Thus, the emitters 7 and the detectors 8 may
be implemented by the same or similar elements, whereby the
emitters 7, the detectors 8 and the pixels 10 are formed as
portions in the organic structure 17 that are selectively and
individually addressable via the electrode layers 15, 16. In this
embodiment, the combination of electrode layers 15, 16 and organic
structure thus forms a composite substrate in which emitters 7,
detectors 8 and pixels 10 are integrated.
[0085] Preferably, the light guide 2 is included as a transparent
substrate during manufacture of the display pixel matrix 6, e.g. as
a backing for supporting the front electrode 16. Alternatively, the
OLEDs may be built up from the side of the lower electrode layer
15, and in that case the light guide 2 is a cover sheet that is
nevertheless required for an OLED display, due to its sensitivity
to moisture. Generally, the light guide 2 may be made of any
material that transmits a sufficient amount of radiation in the
relevant wavelength range to permit a sensible measurement of
transmitted energy. Such material includes glass, poly(methyl
methacrylate) (PMMA), polycarbonates (PC), PET (poly(ethylene
terephthalate)) and TAC (Triallyl cyanurate). The light guide 2 may
be flat or curved and may be of any shape, such as circular,
elliptical or polygonal. It is possible that the light guide 2 is
comprised of plural material layers, e.g. for the purpose of
scratch-resistance, anti-fingerprint functionality, anti reflection
or other functional purpose.
[0086] The use of OLED technology makes it possible to design the
display unit 6 as a thin and flexible unit, if desired. It is also
possible to design the emitters 7 and the pixels 10 with different
emissive properties, if desired. For example, the wavelength(s) at
which the organic structure 17 emits light may be readily tuned
with appropriate dopants during manufacture. Furthermore, the
display unit 6 does not need to have a backlight. Still further,
the size and shape of the image-forming pixels 10, emitters 7 and
detectors 8 are readily set in manufacture. It may e.g. be
advantageous to make the emitters 7 and detectors 8 larger than the
pixels 10. The amount of light emitted by an OLED element increases
with its surface area, and it may thus be desirable to make the
emitters 7 larger than the pixels 10 to increase the amount of
emitted light from each emitter 7. OLEDs are known to have small
heat losses, which enables the use of large emitters 7 without a
need for additional cooling measures. The detectors 8 may also be
made larger than the pixels 10 in order to improve the light
gathering ability of the detectors 8. Another advantage of OLED
technology is that OLEDs typically have a large index of
refraction, typically in the range of 1.7-2 or even higher, whereby
light is emitted in a large solid angle, which may serve to
favorably increase the divergence angle of the respective fan beam
inside the light guide 2 (cf. FIG. 3).
[0087] As noted above, it is conceivable that the light guide 2 is
formed by a transparent substrate or backing for the front
electrode layer 16. It is realized that the process for
manufacturing the display unit 6 may be adapted to add a layer of
lower index of refraction between the electrode layer 16 and the
transparent backing, i.e. the light guide 2, if needed to sustain
light propagation by TIR therein. FIG. 4 shows an embodiment of the
invention, wherein a cross-section of a touch-sensing display panel
1 is disclosed. In this drawing, the layering of the electrodes and
the organic structure outlined with respect to FIG. 2B are not
shown in detail. However, separate pixel elements 10 are indicated
at the central region of the panel. As is well known in the art,
each pixel 10 may be configured to emit light in one color only, or
may comprise several sub pixels configured to emit light in
different colors, such as RGB (red, green, blue). Such sub pixels
may be formed by stacking OLEDs, i.e. forming them on top of each
other, or by placing them next to each other within the area of the
pixel element 10. So, each pixel 10 may include one or several
OLEDs. At the peripheral region the emitters 7 and detectors 8 are
arranged, one of each shown in the drawing. Preferably, as already
described, also the emitter 7 and detector 8 are OLEDs, formed
integrally with the image-forming pixels 10. However, the purposive
use of the emitter 7 and detector 8 on the one hand, and the
image-forming pixel elements 10 on the other hand, are quite
different. The image-forming pixels 10, i.e. the display pixels,
are configured to shine light out from the display panel 1,
preferably in a wide cone angle but most importantly straight up
(in the drawing), which would normally represent the best viewing
angle for an observer. The emitter 7, however, will only be useful
if its light is captured within the light guide 2 to propagate with
TIR towards the detector 8. As a consequence, the part of the light
emanating from the emitter 7 that goes straight up will be lost.
However, a good part of the light will impinge on the front surface
3, from the inside of the light guide 2, in a wide enough angle to
be deflected by TIR. The problem is that since the refractive index
of the image-forming pixels 10 normally is higher than the index of
the light guide 2, the light would escape downwards through the
pixels 10 after reflection in the front surface 3. For this
purpose, an optical layer 21 is disposed between the rear surface 4
of the light guide 2 and the image-forming pixels 10. In one
embodiment this optical layer 21 is made from a material which has
a refractive index n.sub.1 which is lower than the refractive index
n.sub.0 of the light guide 2. That way, there will be TIR in the
light guide 2 in both the front surface 3 and the rear surface 4,
as indicated by the arrows, provided that the angle of incidence is
wide enough. As an example, the optical layer 21 may be provided by
means of a resin used as a cladding material for optical fibers.
Such a resin lay may be provided on the substrate 2 before
deposition of the electrode and organic layers. Alternatively, if
the OLED structure is built from a bottom sheet or plate 9, the
optical layer 21 may be provided on the lower face 4 of the light
guide 2 before attachment over the OLEDs, or over the OLEDs before
attachment of the light guide 2. Another example of an optical
layer 21 with a lower refractive index is an air gap 21, as will be
described further below with reference to FIG. 15.
[0088] In another embodiment, the optical layer 21 is a
wavelength-dependent reflector. Particularly, reflection of the
emitter light in the rear surface 4 is obtained by providing an
optical layer 21 which is at least partly reflective for the
emitter light, while at the same time being highly transmissive for
visible light. As an example, such an optical layer 21 may be
provided by means of a commercially available coating called IR
Blocker 90 by JDSU. This coating 21 has a reflectivity of up to 90%
in the NIR, while at the same time being designed to minimize the
effect on light in the visible (VIS) range to not degrade the
display performance of the touch system, and offers a transmission
of more than 95% in the VIS. It should be noted that there are also
other usable available types of coatings, IR Blocker 90 being
mentioned merely as an example. This type of wavelength-dependent
reflectors are typically formed by means of multi-layer coatings,
as is well known in the art. In an embodiment of this kind, light
from the emitters 7 will propagate by TIR in the front surface 3
and by partial specular reflection in the rear surface 4.
[0089] As is well known, OLEDs are sensitive to moisture, and the
organic layers must therefore be encapsulated. Apart from the light
guide 2 and the bottom sheet 9, a hermetic peripheral seal 91 is
therefore also provided on the panel, e.g. by means of a UV-curable
epoxy.
[0090] It should be noted that the drawings here do not represent
any realistic scale. The thickness of the light guide front glass 2
may be dependent on the size of the panel 1 and what it intended to
be used for, i.e. the environment it will be used in. However, an
OLED structure as such, with electrode layers and intermediate
organic layers, may be very thin and even less than 1 .mu.m. The
substrate 2 or 9 and the cover 9 or 2 will add to the thickness
considerably, though, in order to provide rigidity to a certain
extent. In one embodiment, the light guide may be in the order of
200-500 .mu.m thick. The optical layer 21, though, need not be
thicker than 1-5 .mu.m to provide the cladding effect of realizing
TIR in the rear surface 4 of the light guide 2.
[0091] FIG. 5 shows quite schematically a corner portion of a
touch-sensing display panel 1 according to an embodiment of the
invention. For the sake of simplicity, the peripheral seal 91 is
left out in this drawing. The lower left corner in the drawing
represents an outer corner of the panel 1, whereas the right and
upper edges are to be understood as cutout from a larger panel 1.
Emitters 7 and detectors 8, shown in grey, are arranged along the
peripheral region 11, and the optical layer 21 is provided to cover
the central region 12 of the panel 1 and the image-forming pixels
10 arranged at the central region 12. In an alternative embodiment
(as can be seen in FIG. 8), image-forming pixels 10 are also
present in the peripheral region 11 among the emitters 7 and
detectors 8. Also, the peripheral region 11 may comprise more than
one row of pixels. In addition, the optical layer 21 may cover also
such image-forming pixel elements 10 provided in the peripheral
region 11, in addition to covering the central region 12. It should
be understood that FIG. 5 (and FIG. 7) only schematically show the
different elements in a separated manner in order to clearly point
out those elements, it shall not to be understood as an assembly
instruction or the like.
[0092] FIGS. 6 and 7 show an alternative embodiment, in which an
extension portion 21 a of the optical layer 21 is provided over the
emitters 7 and detectors 8. The extension portion 21a preferably
has substantially the same thickness as the optical layer 21, which
will make it easier to make produce the OLEDs in the peripheral
region 11 and in the central region 12 in the same process, since
they will be provided at the same level. This extension portion 21
a has a refractive index n.sub.2 which is higher than the
refractive index n.sub.1 of the optical layer 21. This way, light
that is injected into the light guide 2 through the extension
portion 21 a may still be reflected in the rear surface 4 where it
faces the optical layer 21, provided that the angle of incidence is
large enough. The refractive index n.sub.2 of the extension portion
21 a may e.g. be the same as the refractive index n.sub.0 for the
light guide 2. Alternatively, a material for the extension portion
21a may be chosen such that its refractive index lies between the
refractive index for the light guide 2 and the refractive index for
the emitter 7 and/or the detector 8.
[0093] In the embodiment shown in FIG. 7, which also shows a cutout
lower left corner portion of a panel 1, the extension portion 21a
runs as a frame portion covering the entire peripheral region. As
an alternative, where image-forming pixels 10 are disposed also in
the peripheral region, the optical layer 21 may be disposed over
such image-forming pixel elements in the peripheral region too.
[0094] FIG. 8 schematically shows a top view of a lower left cutout
corner portion of a panel 1 in accordance with an embodiment of the
invention. In this embodiment, emitters 7, preferably OLEDs, are
shown in grey and are located in the peripheral region 11.
Detectors 8, preferably also realized by means of OLEDs, are marked
with a double frame. The optical layer 21 is not included in the
drawing, but shall be understood to cover at least all of the image
forming elements 10 in the central region 12, and possibly also
some or all of the image forming elements 10 in the peripheral
region 11. If devised in accordance with the embodiment described
with reference to FIGS. 6 and 7, an extension portion 21a is also
employed to cover the emitters 7 and the detectors 8. FIG. 8 also
illustrates how several detectors 8 can be functionally grouped (in
the drawing also physically grouped) into a subset 80 to act as one
larger detector. This way the light-sensing detector surface can be
increased, and be operated as having its center between the
detectors 8 of the subset 80. FIG. 8 also shows that the peripheral
region 11, in some embodiments, may include more than one row of
pixels.
[0095] FIG. 9 illustrates a variant of the embodiment of FIG. 6.
However, instead of arranging the emitters 7 and detectors 8 to
take the place of respective image-forming elements 10, they are
instead configured together as stacked OLEDs. Also, as illustrated,
the detector 8 may be realized as one larger surface OLED 8, or as
a grouped subset 80 of separate adjacent or dispersed OLED
detectors 8, each stacked with an image-forming element 10. The
drawing shows the emitter 7 and detector 8 stacked beneath a
respective image-forming OLED element 10. In an alternative design,
the emitter 7 and/or the detector 8 may instead by stacked on top
of the respective image-forming OLED element 10.
[0096] FIG. 10 shows an embodiment, which exhibits yet another type
of detector arrangement. In this embodiment, the detector 8 is
provided as a separate element, attached beneath the entire OLED
structure of image-forming elements 10. Such a design has a large
degree of freedom for the placement and size of the detector
element 8, but requires that also the back panel 9 is transmissive
to the operating wavelength range of the emitter 7, which typically
lies in the near IR (NIR). In FIG. 10 this detector design is
combined with an integrated OLED emitter 7, corresponding to the
disclosure of FIG. 6. However, a stacked OLED emitter 7, as in FIG.
9, may also be employed.
[0097] FIGS. 11-12 outline some steps included in embodiments of a
method of producing a touch-sensing display panel 1 in accordance
with the invention. FIG. 11 relates to a method of producing a
pixel matrix that starts from anode side, and FIG. 12 relates to a
method of producing a pixel matrix starting at a cathode side,
according to known alternative principles within the industry. In a
preferred embodiment, those pixels are OLEDs.
[0098] Following the embodiment of FIG. 11, step 111 involves
providing a transparent substrate 2 with refractive index n.sub.0.
This transparent substrate 2 will serve as the FTIR light guide in
the final product, with a front surface 3 providing the
touch-sensitive region, potentially with additional functional
layers on it. The substrate 2 may e.g. be made of a suitable glass
material, of PMMA, PC, or other transparent material.
[0099] In a subsequent step 112, an optical layer 21 is provided on
a rear surface 4 of the substrate with a refractive index
n.sub.1<n.sub.0 at a central region 12. The optical layer 21 may
e.g. be a resin or an adhesive attached to the rear surface 4.
Alternatively, the optical layer 21 may be formed in e.g. a vapor
deposition process. The difference in refractive index need not be
large. As a mere example, n.sub.0 may be between 1.5 and 1.6, and
n.sub.1 may be between 1.4 and 1.5. With reference to the preceding
disclosure, the optical layer 21 may be added with an extension
portion 21a at a peripheral region 11 around the central region 12.
In such an embodiment, the refractive index n.sub.2 of the
extension portion shall be higher than n.sub.1.
[0100] In a subsequent step 113 a matrix of pixel elements is
provided at the rear surface 4 over the central region 12 and over
a peripheral region 11. According to processes well known in the
art of OLED technology, such a process may include a TFT layer and
possibly a TFT passivation layer thereon, before applying an anode
layer. One or plural organic layers are then built up, typically
including an emissive layer but selectively also transport layers
and blocking layers. A cathode layer is then provided to create the
polarity of the OLED cell.
[0101] In step 114 a cover sheet 9 is provided over the pixel
matrix. This may be realized by means of an assembly of a rigid or
flexible solid sheet 9, by coating the pixel matrix with a curable
liquid, or in a vapor deposition process.
[0102] In step 115, the cover sheet 9 is sealed to the substrate 2,
so as to obtain a hermetic encapsulation. This sealing is made
using a peripheral seal 91, while still providing means for a
galvanic connection to the pixel matrix, e.g. by means of a flex
film connection. It should be noted that the steps of providing the
cover sheet 9 and sealing it may at least to some extent be
performed concurrently with each other.
[0103] The embodiment of FIG. 12 begins at the other end, with the
step 121 of providing a carrier sheet 9. This carrier sheet will
form the backside of the touch-sensing display panel 1, and while
it therefore does not need not be transparent it may still be made
of glass, a plastic material, a metal such as aluminum, etc.
[0104] Step 122 includes providing a matrix of pixels on the
carrier sheet 9. This will be a process which has a reversed order
in comparison with the process of FIG. 11, beginning with the
cathode layer. Otherwise it may include the same type of electrode
layers and organic layers, as is known in the art.
[0105] In step 123, a transparent substrate 2 with refractive index
n.sub.0 over the pixels is then provided, which has an intermediate
optical layer 21 with a refractive index n.sub.1<n.sub.0 at a
central region 12 of the substrate within a peripheral region 11.
As outlined above, the optical layer 21 may be applied to the
backside 4 of the substrate 2 and then attached over the pixels.
Alternatively, the optical layer 21 may first be coated onto the
pixel matrix, after which the substrate 2 is attached. Also, as
noted with reference to FIG. 11, an extension portion 21a may be
provided over the peripheral region 11, adjacent to the optical
layer 21.
[0106] In step 124, the transparent substrate is sealed to the
carrier sheet. As for the embodiment of FIG. 11, this will include
a peripheral seal and the provision of a connector to the electrode
layers for driving of the pixel matrix. Again, the steps of
providing the substrate 2 and sealing it may at least to some
extent be performed concurrently with each other.
[0107] The process step of FIGS. 11 and 12, respectively, deal with
the provision of the layered structure according to the invention.
In order to become a final working product, the layered structure
must also be connected and driven so as to enable the use of the
panel 1 both for image reproduction and touch-sensing.
[0108] FIG. 13 is a section view of a touch-sensing display
apparatus 40, which comprises the display panel 1, including the
light transmissive light guide 2 and a pixel matrix 6, and a signal
processor 41, which are arranged in an enclosure 42 such that the
light guide 2 forms a transparent front cover of the display
apparatus 40. The signal processor 41 is a processing element (or
means) which is connected to the display panel 1 so as to transmit
control signals to the pixels, the emitters and the detectors, as
well as to acquire output signals from the detectors. The signal
processor 41 is also operable to generate and output touch data
calculated based on the output signals. It is to be understood that
the signal processor 41 may alternatively be implemented as a
dedicated controller for the pixels and a dedicated controller for
the emitters and the detectors.
[0109] It is to be understood that the display apparatus/display
unity may form part of any form of electronic device, including but
not limited to a laptop computer, an all-in-one computer, a
handheld computer, a mobile terminal, a gaming console, a
television set, etc. Such an electronic device typically includes a
processor or similar controller that may be connected to control
the display panel 1 to display information content within at least
part of the touch surface 3 and to provide touch sensitivity within
the touch surface 3. The controller may be implemented to control
the display panel 1 via the signal processor 41, or it may
implement part or all of the functionality of the signal processor
41.
[0110] FIG. 14 shows a number of steps, which need not be provided
in the given order, that may be included in any one of the
embodiments of FIGS. 11 and 12, so as to create a functional
connection of the display panel 1 to a signal processor 41.
[0111] In step 141 a plurality of pixels 10 in at least the central
region 12 are connected to a control circuit 41 configured to drive
them as image-forming pixel elements. As noted before, these
image-forming elements are preferably all disposed under the
optical layer 21, and may to some extent also be provided in the
peripheral region 11. Collectively, the image-forming elements 10
form the display part of the panel 1.
[0112] In step 142 at least one pixel 7 in the peripheral region 11
is connected to a control circuit 41 configured to drive the pixel
7 to emit light into the transparent substrate 2 for propagation by
TIR therein. Preferably, a number of emitters 7 are connected this
way, provided in the peripheral region along at least two sides of
the panel 1.
[0113] In step 143 at least one detector 8 in the peripheral region
11 is connected to a control circuit 41 configured to drive that
detector 8 to detect light from the transparent substrate 2,
emanating from the emitter 7. Correspondingly, a number of
detectors 8 are preferably connected this way, provided in the
peripheral region along at least two sides of the panel 1. Together
with the emitters 7, they will form the touch-sensing detection
grid of the touch surface 3. With reference to the embodiments of
e.g. FIGS. 4 and 9-11, the detectors 8 may also be pixels 8 of a
common matrix as the image-forming elements 10 and the emitters 7,
preferably OLEDs, or alternatively separate detector elements 8
applied below the pixel matrix. Also, the detectors 8 may be
connected to the control circuit 41 so as to be controlled in
subsets 80, where each subset 80 has an aggregate detector surface
of the combined surface areas of the included detectors 8.
[0114] Reference will now be made to the embodiment of FIG. 15,
illustrating a side view of an FTIR system of a combined display
and touch-sensing panel 1, formed by attaching a light guide 2 to a
display 6. The light guide 2 may be bonded to the display unit 6 by
means of an adhesive, such as an optical adhesive. In one
embodiment, the light guide 2 is laminated onto the display unit 6.
To enable the light from the emitters 7 to be coupled into and out
of the light guide 2 at the peripheral region 11, while enabling
the light to propagate by TIR across the light guide above the
center region 12, different adhesives may be used in the peripheral
region 11 and the center region 12, as indicated by reference
numerals 20, 21. Specifically, the adhesive 21 in the center region
12 may be selected to have an lower index of refraction lower than
the light guide 2, while the adhesive 20 in the peripheral region
11 may be selected to have an index of refraction that is higher or
substantially equal to the index of refraction of the light guide
2.
[0115] In a variant, the light guide 2 is attached by an adhesive
20 to the display unit 6 at the peripheral region 11 only and
arranged with an air gap 21 to the center region 12 of the display
unit 6. It is currently believed that an air gap of at least about
2-3 .mu.m is sufficient to enable propagation by TIR in the light
guide 2. This variant may facilitate removal and replacement of the
light guide 2 in the course of service and maintenance.
[0116] It is also conceivable that the light guide 2 is attached to
the display unit 6 via a spacer 20 of solid transmissive material.
The spacer may be bonded to the light guide 2 and the display unit
6, respectively, by thin adhesive layers, such that the coupling of
light is controlled by the index of refraction of the spacer 20
rather than the adhesive. In analogy with the above, the spacer 20
may be located at the peripheral region 11 only, or spacers 20, 21
with different index of refraction may be located at both the
peripheral region 11 and the center region 12.
[0117] The combined touch-sensing display panel FTIR system 1 may
also include structures configured to re-direct the light emitted
by the emitters 7, e.g. to reshape the emitted cone of light so as
to increase the amount of light coupled into the light guide 2 in a
desired fashion. For example, the emitted light may be redirected
so as to form the fan beam in the plane of the light guide 2, as
shown in FIG. 3, and/or the emitted light may be redirected to
increase the amount of light that is trapped by TIR in the light
guide 2. These light-directing structures may be included in the
above-mentioned spacer 20, or the portion of the surface 4 that
faces the peripheral region 11 of the display unit 6, or the
peripheral region 11 of the display unit 6 itself. Similar
light-directing structures may be included between the light guide
2 and the detectors 8, so as to re-direct outcoupled light onto the
detectors 8. Generally, the light-directing structures may be said
to define the field of view of the emitter/detector 7, 8 inside the
light guide 2. The light-directing structures may be in the form of
a micro-structured elements, such as but not limited to,
reflectors, prisms, gratings or holographic structures. The
micro-structured elements may be etched, printed, hot embossed,
injection molded, pressure molded or otherwise provided between the
emitters/detectors 7, 8 and the light guide 2. One approach for
coupling the LEDs to the light guide panel is proposed in the
article "Injecting Light of High-Power LEDs into Thin Light
Guides", by Cornelissen et al, published in Proc. SPIE 7652,
International Optical Design Conference 2010, pp 7652121-7652126,
2010. According to this approach, the top surface of the LED is
modified to have a rough surface behaving like a Lambertian
reflector. A dielectric multilayer filter is deposited on the
bottom of the light guide panel, and the top surface of the LED is
optically coupled to the filter by a silicone adhesive. The filter
is optimized to only transmit light emitted from the LED at angles
larger than the critical angle at the interface between the light
guide and its neighboring optical layer. The purpose of the
multilayer is thus to only transmit light that can propagate in the
light guide. The light emitted at smaller angles is reflected back
toward the rough LED surface where it is subsequently recycled by
reflection and redistribution.
[0118] The light-directing structures may be omitted, whereby part
of the emitted light will pass through the light guide 2 without
being trapped by TIR. Selected parts of the front surface 3 of the
light guide 2, e.g. above the peripheral region 11, may be provided
with a coating or cover 22, as will be described in more detail
below, to prevent such light from passing the front surface 3.
[0119] With or without light-directing structures, it may be
desirable to implement stray light reduction measures. In one
example, the edge surface of the light guide 2 and/or the portion
of the surface 3 above the peripheral region 11 may be provided
with surface structures that prevent light from the emitters from
being reflected back into the light guide 2. Useful anti-reflective
surface structures include diffusers and light-absorbing
coatings.
[0120] In a variant, surface structures are provided on the edge
surface of the light guide 2 and/or the portion of the surface 3
above the peripheral region 11 to re-direct light from the emitters
into the light guide 2 for propagation by TIR. It is also possible
that the edge surface is formed with a suitable bevel to re-direct
the light. Such surface structures may include light-reflective
coating(s) and/or micro-structured elements, and may implement or
be part of the above-mentioned light-directing structures.
[0121] FIG. 15 further illustrates a cover frame 22, a feature
which may be included in any one of the other described embodiments
as well. The cover frame 22 is disposed to cover the peripheral
region 11, and possibly also extend a portion into the central
region 12. The cover frame 22 may fulfill one or more of three
different purposes.
[0122] As noted above, a surface of the cover frame 22, facing the
light guide 2, may be configured to reflect light from the emitter
7 such that it may propagate in the light guide 2 rather than
escape. As an example, a diffuser may be used for this purpose,
which will reflect a part of the emitter light in angle that may
satisfy the requirements for TIR in the light guide 2.
[0123] Secondly, the cover frame 22 may hide any structures in the
peripheral region 11 from a user, particularly if only the central
region 12 is used as an image display. For this purpose the cover
frame 22 should be opaque to visible light.
[0124] As a third purpose, the cover frame 22 may be configured to
block out ambient light from reaching the detectors 8. For this
purpose, the cover frame 22 should be opaque to the operating
wavelength of the touch-sensing system, i.e. the light detected by
the detectors 8 from the emitters 7 to determine the occurrence of
a touch. As mentioned, also the FTIR system may make use of visible
light, but in a preferred embodiment NIR radiation is employed.
[0125] The cover frame 22 may e.g. be provided by means of a thin
metal sheet. It may be provided as a separate element or form part
of a housing 42 or bracket for holding the display panel 1. In
another embodiment, the cover frame 22 may be implemented as a
coating or film, in one or more layers, on the front surface 3. For
example, an inner layer facing the front surface 3 may provide
specular and possibly partly-diffuse reflectivity, and an outer
layer may block ambient and/or visible light. In one embodiment,
the cover frame 22 may comprise a chromium layer provided onto the
top surface 3, to obtain a surface towards the panel light guide 2
which is at least partially specularly reflective to light in the
emitter wavelength. In addition, the cover frame 22 may comprise an
outer layer, which is substantially black to block visible light,
by oxidizing the upper surface of the chromium layer. In other
embodiments, other metals, with corresponding oxides, may be used,
such as aluminum, silver etc. In yet other embodiments, the
specularly reflecting lower layer may be provided by means of a
metal, whereas an upper layer may be provided by means of paint,
e.g. black paint. In any case, the cover frame 22 is preferably
substantially flat, and should be as thin as possible while
providing the desired benefits of blocking IR light and visible
light. In yet another embodiment, the cover frame may be disposed
as an opaque frame layer between two different layers of the light
guide 2, rather than on the front surface 3. This way it may be
possible to obtain a flush front surface 3. In a further embodiment
the cover frame 22 is disposed at the rear surface 4 of the light
guide 2, and is configured to block visible light but to transmit
IR. This way, the peripheral region structures are covered but
light from the emitters 7 may still pass through the cover frame 22
to the light guide 2, and subsequently out through the cover frame
to the detectors 8.
[0126] FIG. 16 is a section view of an embodiment in which the
display unit 6 is based on liquid crystal technology, and
specifically with the display unit 6 being a TFT-LCD. The display
unit 6 comprises a rear electrode layer 25, a front electrode layer
26 and an intermediate liquid crystal (LC) structure 27. The
electrode layers 25, 26 are transparent and comprises a respective
polarizer. The rear electrode layer 25 comprises a pixel-defining
electrode structure and a TFT active matrix for pixel selection,
whereby the polarization of the LC structure 27 may be selectively
controlled (addressed) at the location of each pixel. The front
electrode layer 26 may be implemented as a common electrode and may
also comprise color filters, as is known in the art. In the
illustrated embodiment, the display unit 6 further comprises a LED
matrix backlight 28, which projects light for transmission through
the electrode layers 25, 26 and the LC structure 27. Like in the
foregoing embodiments, a light transmissive light guide 2 is
arranged to define a front touch surface 3. In effect, the light
guide 2 may be a sandwich structure including both color filters
and polarizer, or simply be a planar cover lens, dependent on at
which layer forms the rear surface 4 for reflection of the
propagating light. In the illustrated embodiment, the rear
electrode layer 25 is designed with detectors in its peripheral
region 11. The detectors may e.g. be integrated as light-sensitive
TFTs. Further details on TFT-LCDs and light-sensitive TFTs are e.g.
found in WO2007/058924 and US2008/0074401, which are incorporated
herein by reference.
[0127] In one embodiment, the LC structure 27 does not extend into
the peripheral region 11, in order to avoid that the liquid crystal
obstructs the detection of the light that is coupled out of the
light guide 2. In the example of FIG. 16, the emitters are formed
by dedicated LEDs in the peripheral region 11 of the backlight 28.
In this embodiment, the combination of backlight 28, electrode
layers 25, 26 and LC structure 27 thus forms a composite substrate
in which emitters 7, detectors 8 and pixels 10 are integrated.
Further, a light-coupling element 30 is arranged to direct the
light from the emitters to the light guide 2 and from the light
guide 2 to the detectors. The light-coupling element 30 may or may
not include the above-mentioned light-directing structures.
[0128] In an alternative embodiment (not shown), all or part of the
emitters are integrated in the rear electrode layer 25, e.g. in the
form of LEDs or light-emitting TFTs. In a further alternative
embodiment (not shown), all or part of the detectors are integrated
into the backlight 28, e.g. in the form of light-sensing LEDs or
TFTs. In all of these embodiments, the backlight 28 may instead be
implemented to illuminate the electrode layers 25, 26 and the
liquid crystal structure 27 from the side, as is known in the
art.
[0129] It is to be understood that the above discussion in relation
to FIG. 15 is equally applicable to the embodiment in FIG. 16.
[0130] FIG. 17 shows another embodiment of the invention,
implementing an LCD unit 6. The drawing shows a corner portion of a
touch-sensing display panel 1, in which a number of elements have
been vertically separated for the purpose of illustration only.
Basically, the display panel 1 of this embodiment includes the LCD
unit 6 and a light guide 2 which provides the touch-sensitive
surface 3. At the bottom of the drawing, a backlight 28 is
disposed. Light is injected into the backlight 28 from a light
source (not shown), preferably through an incoupling arrangement
designed to spread light within the light guide, as is well known
in the art. In this embodiment the backlight 28 includes a light
guide with at least one structured surface 281, functioning to lead
out light upwards through the display layers. Typically it is the
lower surface 281 which is structured, whereas light propagates by
TIR in the upper surface of the backlight light guide 28, and
preferably also in the lower surface 281 between structured areas
thereof. The backlight 28 may also include a rear side reflector
(not shown) for reflecting light, which escapes through the
structured surface 281 of the light guide, back into the backlight
light guide. Further details with regard to embodiments of the
backlight 28 will now be outlined below with reference to FIG.
18-20, before returning to the embodiment of FIG. 17.
[0131] FIG. 18 shows a plane view of the backlight 28, whereas
FIGS. 19 and 20 shown perspective views of two different ways of
realizing the backlight 28. In the present embodiment, the
backlight 28 is not only used for the image-forming pixels 10, but
also as the light source of the emitters 7. For the first purpose,
an area 28a representing the central region 12 of the lower surface
281 of the backlight 28 is structured to evenly spread light up
through the upper surface 282 of the backlight 28. This is, as
such, well-known technology frequently used in the art. Exact or
detailed ways of structuring a surface of a backlight for this
purpose will therefore not be outlined here, but typically the
structured area 28a is designed with respect to where light is
injected, such that not all light is leaked close to the light
source. In addition to the central region structured area 28a, the
backlight is also devised with a structured area 28b in the
peripheral region 11. The structured area 28b preferably has a
sequential design, such that light is leaked out at distinct
places, where it is wanted, throughout the peripheral region 11.
This way less light is wasted. In an alternative embodiment (not
shown) also the peripheral region 11 may be devised with a more
evenly dispersed structured area 28b, similar to the structured
area 28a of the central region 12, and which light is to be led up
is instead only defined by the pixel structure of the driving of
the liquid crystals.
[0132] FIG. 19 shows one way of realizing the backlight 28. In this
embodiment, the backlight 28 comprises two light guides; a central
light guide 283 and a peripheral light guide 284, one disposed over
the other in a sandwich structure. The two light guides 283, 284
may be configured with different refractive indexes for the
wavelengths used, typically white light in the central region 12
and NIR in the peripheral region, so at to allow light to propagate
by TIR in the respective light guides without leaking. In the
drawing, the central light guide 283 is only about as wide as the
central region 12, i.e. the imaging part of the display. In an
alternative embodiment (not shown), the central light guide 283 may
be just as wide as the peripheral light guide 284, yet only
provided with its structured area 28a at the central region 12.
Correspondingly, it may be noted that the peripheral light guide
284 is illustrated as an entire sheet covering the central region
12 too. However, an alternative design (not shown) may include a
peripheral light guide 284 that is frame-like, lacking a central
portion. Such a frame-like light guide may be disposed around the
central light guide 283. Such an embodiment would thus mean an
arrangement where the two light guides 283 and 284 are arranged in
the same plane rather than being sandwiched, which theoretically
could entail a lower profile to the entire display panel 1. In the
embodiment of FIG. 19, separate light sources are employed for the
different purpose; a VIS light source 285 for injecting white light
into the central light guide 283, and a NIR light source 286 for
injecting NIR light into the peripheral light guide 284. As is
known by the skilled person, plural light emitters may be used for
injecting light into a light guide, and the representation of one
light source for each light guide shall therefore merely be seen as
an example.
[0133] FIG. 20 shows an alternative embodiment, where one and the
same light guide 287 is configured to be used for both purposes. A
single light source 288 is shown, but as already explained it may
comprise plural emitters. In any case, light is injected in the
light guide 287 within wavelength ranges for use both as imaging
backlight via the central structured area 28a and for FTIR purposes
via the peripheral structured area 28b. The light source 288 may
comprise a broad spectrum emitter, or may comprise several emitters
devised to inject light in different wavelengths, such as VIS and
NIR.
[0134] Returning to FIG. 17, starting from the bottom this drawing
shows a display panel 1 comprising an LCD unit 6 and a light guide
2. The LCD unit 6, in turn, comprises a backlight 28, an electrode
25 including a lower polarizer, a liquid crystal layer 27, and an
upper electrode 26 with an upper polarizer and color filters. The
peripheral structured area 28b of backlight 28 is indicated, but
the drawing leaves out the central structured area 28a for the sake
of clarity. As indicated by the dashed vertical arrows, the
peripheral structured area 28b serves to lead out light upwards in
the structure. The backlight 28 may e.g. be designed in accordance
with any of the embodiments described with reference to FIGS.
18-20. It should also be noted that the arrows are symbolic and
that rather a cone of light will be led out in reality, as
determined by the geometry of the backlight. The electrode 25
comprises a pixel-defining structure and a TFT active matrix. In
operation together with the upper electrode 26 (indicated as a
lower surface of the light guide 2), the electrode 25 is configured
to define pixels in the intermediate liquid crystal (LC) layer 27.
Also, the TFT active matrix connect to detectors 8, to read out
sensed received light. Such detectors may e.g. be photo detectors,
OLEDs or similar, as previously discussed for other
embodiments.
[0135] Preferably, the LC layer 27 is driven by a controller 41
using the electrodes 25, 26 according to a predetermined scheme
such that the LC layer is opened at portions 271 over the
structured area 28b in a certain pattern. In one embodiment,
portions 271 are opened one by one in succession over each one
structured area 28b, such that each portion 271 will serve as, or
emulate, one emitter 7, which emitters 7 will act as flashed one by
one. An incoupling arrangement 71 is configured at the rear surface
4 of the light guide, at which light is injected into the light
guide 2. Emitter light is indicated in the drawing by means of
dashed vertical arrows, from the structured area 28b to the light
guide 2.
[0136] Once injected in the light guide 2, at least parts of the
light will propagate by TIR in at least the front surface 3 to
outcoupling structures 81 at the rear surface 4. Furthermore, the
LC layer 27 is preferably driven by the controller 41 over the
electrodes 25, 26 such that the LC layer 27 is held open, i.e.
transmissive, at portions 272 over the detectors 8, below the
outcoupling structures 81. This way, light coupled out from the
light guide 2 is led to the detectors 8, as indicated by the
vertical dash-dotted arrows.
[0137] Although this is not shown in this drawing, it has been
outlined with respect to other embodiments that incoupling and
outcoupling may be achieved simply by bypassing an optical layer 21
disposed under the light guide 2 over the image-forming pixels 10
in the central region 12. In addition, the incoupling and
outcoupling structures may include diffusive and/or diffractive
elements to direct light in or out of the light guide 2. It may be
noted that the size of the portions 271 and 272 of the LC layer 27
need not be equally large, even though the drawing indicates this.
Also, each such portion 271 and 272 is preferably made up of a
plurality of pixels of the TFT active matrix and the LC layer
27.
[0138] While the invention has been described in connection with
what is presently considered to be the most practical and preferred
embodiments, it is to be understood that the invention is not
limited to the disclosed embodiments, but on the contrary, is
intended to cover various modifications and equivalent arrangements
included within the scope of the appended claims. It should be
noted that while certain features have been described in
conjunction with different drawings, such features may well be
combined in one and the same embodiment.
[0139] For example, it is conceivable that only the detectors 8 are
integrated in the display unit 6, while the emitters 7 are
otherwise installed in the display apparatus 40, e.g. as separate
components. Likewise, it is conceivable that only the emitters 7
are integrated in the display unit 6, while the detectors 8 are
otherwise installed in the display apparatus 40, e.g. as separate
components.
[0140] In certain embodiments, the display unit 6 may comprise only
one emitter 7 in combination with plural detectors 8, or only one
detector 8 in conjunction with plural emitters 7. It is even
conceivable that the display unit 6 has only one emitter 7 and one
detector 8, e.g. to detect the presence of a touching object 5 on
the touch surface 3.
[0141] Although it may be preferable that the emitter(s) 7 and the
detector(s) 8 are implemented by the same technology as used for
generating images in the display area, e.g. to have similar
functional structure as the pixels 10, it is also possible that the
detector(s) 7 or the emitter(s) 8, or both, are implemented by a
different technology when integrated into the display unit 6.
[0142] As noted above, it may be desirable that the surface area of
the emitters and detectors is larger than the surface area of the
pixels. It is to be understood that the emitters may be larger than
the detectors, and vice versa, and also that the emitters and
detectors may have any shape, including circular, elliptical, and
polygonal.
* * * * *