GB2475519A

GB2475519A - Optical channeling system for creating detection surfaces

Info

Publication number: GB2475519A
Application number: GB0920367A
Authority: GB
Inventors: Cassim Ladha
Original assignee: CASCOM Ltd
Current assignee: CASCOM Ltd
Priority date: 2009-11-21
Filing date: 2009-11-21
Publication date: 2011-05-25
Also published as: GB0920367D0

Abstract

An apparatus includes an input surface formed using optical conduits 2 (e.g. optical fibres) to pass input to a detector/s placed at the end of the optical conduits. A system of optical fibres may be clad in material of higher refractive index and fixed into a support material placed behind a liquid crystal display 4 to route reflection signals produced by illumination of invisible light (infrared) from objects 3 in front of the display. The light source 1 may be provided using the same array of optical fibres or a different array interspersed among the first array. The Array may be placed in front of an LCD back light 8 and used instead of a diffusing layer. Other displays such as OLED displays may also be used.

Description

Optical Channeling System for Creating Detection Surfaces

of which the following is a specification:

FIELD OF THE INVENTION

The present invention pertains generally to optical sensing technology, and more particularly to gathering inputs to the system when the invention is combined with an electronic visual display device.

BACKGROUND OF THE INVENTION

Recently the cost of liquid crystal displays, LCDs, has reduced and they are currently out selling the alternative technologies like cathode ray tube, CRT, technologies. This is because they can provide a higher definition output, are less bulky and provide a more pleasant contrast for displaying graphics and text. Recent advances in computing power have led to a number of technologies to develop that allow humans to interact with LCD display technology for the purpose of data manipulation, application interaction and audio-visual kinaesthetic learning. The touch input LCD display has been a familiar device for several years with significant improvements being made since its invention.

A usual embodiment of an LCD touch input display consists of a sensing element either directly laminated onto the LCD or placed closely to it. Current systems incorporate a variety of different technologies all implemented slightly differently. However, they can be sub-divided into two distinct classes: optical and non-optical.

Non-optical systems are split into two main categories, mechanical and capacitive. The simple mechanical systems use layers of resistive material separated by a thin insulative layer which is displaced by the force of a touch resulting in an electrical connection between the layers. These devices have a low life time due to wear and poor aesthetic due to the optical properties of the layers. Capacitive displays use the tiny capacitance between the users finger and the sensor network to detect the touch. The sensor network is usually formed on the reverse of a glass screen placed in front of a display using an array of conductive elements often made from visibly transparent materials such as indium-tin-oxide. A more successful implementation of such a system is used by Apple inc in its iPhone product. In general non-optical touch sensitive displays are hard to make in sizes above 19". This is partly because as the display size increases, the signal to noise ratio (SNR) on the sensor deteriorates and it is difficult to accurately discriminate intended interactions.

Optical systems more often than not lever on non-visible light (usually in the near infra-red, IR, spectrum) being concentrated and detected via a sensitive electronic detector. A common detector often used takes the form of a charged coupled device. CCD, however dark current detectors and forward biased semi-conductors may also he suitable. A very commonly implemented optical based touch input detector is based around contained light within a clear substrate in front of the display being caused to frustrate out at the point of touch and detected using a CCD camera. This effect is called frustrated total internal reflection, FTIR, and is understood in Han et al. An inherent characteristic of LCD technology is a high transmisivity to light in the near IR spectrum allowing a IR sensitive CCD camera to detect JR emission through the LCD display A common problem with current optical based touch detection systems is that the detector device must be placed sufficiently far enough from the touch screen that the full span of the surface is in field of view. Often positive focusing lenses are used to shorten this distance however for larger screens the effect has a major impact on physical depth of the display. Methods to reduce this depth include using multiple cameras and stitching the images however this solution is unattractive from both a complexity standpoint and when examining component costs.

SUMMARY OF THE INVENTION

This invention is a novel approach to achieve optical based multiple-touch sensitivity in con-junction with LCD displays over 17" while still maintaining a relatively shallow depth dimension (or thinness). The invention also alleviates the need for any components to be placed in front of the display. The invention utilises an array of optical channels or conduits, which may be optical fibres to guide and distribute emitted non-visible near IR emissions from a single source to multiple points behind the LCD display. An inherent property of the LCD display is to allow this JR light to propagate through. Any objects in the direct path of the near JR emissions will reflect the light back through the display. In addition to the first set of conduits behind the display is a second set.

This second set is optimally placed to receive the reflections and guide them in 3-dimensions to the side of the display where they are bundled, polished and presented to a detector. It is not required that the spatial position of the fibre tips behind the display is preserved within the bundle the computer interfaced to the detector is able to reason this spatial relationship with prior knowledge of the tip pitch and screen dimensions. The detector is interfaced to a computer running software that is capable of reasoning, in real time, the spatial position of detected reflections on all points of the display simultaneously. These reflections correspond to touch inputs at the screen surface may later be used for inputs to computer applications running on the display. Those skilled in the art will realise that the same set of optical conduits may be used for both IR. illumination and detection if they are split into two or more interleaved banks. In this embodiment two or more detectors and two or more IR emitters may be conveniently used coincidently (completely out of phase) such that one or more banks illuminates and the others detect.

Those skilled in the art will also note that the reflecting body does not need to be in direct contact with the screen to make a reflection and that the lower signal strength received from a distant reflector will enable an element of depth perception to be reasoned. IR emissions may also he externally introduced from an emitter placed in front of the screen. This would allow information to directly passed to the detector encompassing an element of spatial context.

One embodiment of the invention will incorporate an LCD display with the invention replacing the diffuser component in the backlight assembly. The backlight assembly will still contain one or more of the following: a light source, a reflector, a filter, lenses, distributing optics and other diffusers.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail, with reference to the accompanying drawings, in which: FIG. 1. is a cross sectional view detailing the basic principle of operation. The figure shows non-visible IR light (1) being guided through a flexible optical conduit (2) to illuminate a. finger (3) in close proximity to the LCD display (4). The finger (3) reflects some of the emitted light back down a secondary conduit (5) which is terminated at a detector (6) connected to a computer (7).

The figure shows a small region of overlap (14) in the acceptance angle of the receiving conduit (.5) and the conduit being used for illumination (2).

FIG. 2 is an illustration detailing one form factor that the invention can be embodied in. In the figure is shown a backlight assembly (8) placed behind the invention (9); the backlight is used to illuminate images displayed on the LCD display (4). Within the invention it is possible to see 2 banks of flexible optical conduits (2) and (5) routed in 3 dimensions before being polished and terminated in 2 separate bunches (10).

FIG. 3 is an exploded diagram of FIG 2 showing in more detail how the tips of the two banks of flexible optical conduits (2) and (5) are terminated at the surface of the invention housing material (11) such that the hank being used to receive Ill reflections is surrounded by conduit tips of the opposite bank.

FIG. 4 is a illustration highlighting the system of events that occurs between providing illumi-nation down one set of optical conduits (2) and providing manipulated application data to the LCD display (11). Within the process a computer (7) spatially reasons the position of each conduit tip (5) at the surface of the invention housing material (11). This is achieved with prior knowledge of the pitch and LCD display (4) dimensions. Also shown in the figure is the JR light emitter (12) being separated from the CCD detector (6) and an optional lens assembly (13).

While the patent invention shall now be described with reference to the embodiments shown in the drawings, it should he understood that the invention is not limited to these specific embodiments.

DETAILED DESCRIPTION OF THE DRAWINGS

One possible embodiment of the invention will now be described in detail by means of example using the attached referenced figures: FIG 1 Figure 1 shows the principle of operation of the invention. The embodiment includes the invention placed in between a hack light (8) and an LCD display (4). The significance of this placement is because the the invention is being used as diffuser. In the figure the optical conduits are held in place by a polymer (e.g plastic). The refractive index of this polymer is chosen such that no-light can escape from the conduits into the polymer. Those skilled in the art will note that this refractive index becomes irrelevant if sheathed optical conduits are used. A support structure shown in the figure is used to hold the tips of the fibres in place while the embodiment is constructed. This support structure may be formed out of any material as long as time material exhibits transmissive properties possibly in conjunction with diffusive optical properties.

The optical conduits are positioned in the embodiment such that light emitted through conduit (2) falls slightly within the acceptance angle of optical conduit (2). Those skilled in the art will note that this distance is a direct relationship between the diameter of the optical conduit and the distance that the invention is placed from the screen. Both these parameters require fine tuning for the desired sensitivity of the application using the invention. No exact specification is given to these dimensions because altering them does not detract from the principle of operation.

The figure shows invention works by placing a non-visible IR light source (1) (routed in 3 dimen-sions via an optical conduit (2)) very close to the rear surface of an LCD display (4). It is an inherent nature of the LCD to be highly transmisive to JR light and because the distance between the light source and the display is relatively short minimal losses are caused through reflections. The light that passes through the screen illuminates any object (3) in direct proximity to the screen; distant objects reflect less light than miear objects and thus presenting a mechanism for reasoning depth.

The reflected light is gathered by a second optical conduit (5). again placed in close proximity to the reverse side of the LCD. This collected reflected light is routed in 3-dimensions and presented to a detector (6) placed to the side of the LCD display. FIG 2

The figure shows the invention sandwiched between a hacklight (8) and and LCD display (4).

In this figure the optical conduits can be seen to be routed in 3-dimensions and brought to the side of the LCD display The conduits are hunched and polished into bundles at this point hefore being presented to a detector (6). FIG 3

Is an exploded version of figure (2) highlighting the spatial relationship between the optical conduits being used for emission and those being used for detection. In the figure it is clear that any libre being used for detection (2) has its nearest neighbouring conduits acting as illuminators, Those skilled in the art will note that the shown geometrical arrangement in only one of a possible number of arrangements that will exhibit this characteristic, FIG 4 Figure 4 illustrates an IR. emitter (12) illuminating a polished bunch of optical conduits. These optical conduits are routed in 3-dimensions into a. grid matrix at on surface of the invention as shown in Figure 3. Any reflected emissions arising from an object being placed in proximity to the screen is gathered by a second array of optical conduits at the surface of the invention and routed in 3-dimensions to a second polished bundle (5). It should be noted that during the 3-dimensional routing process it is not necessary to preserve the spatial relationship of the fibres on the surface of the invention. A sensitive detector (6) is used to capture the signals received on the polished bunch (5) into a pixelated image. This image is processed by a computer (7) to spatially reason the position of the object reflecting the emitted light at the surface of the invention. Those skilled in the art will appreciate the computer (12) may be replaced by a micro-controller or other embedded processor which in turn passes the processed images onto a computer or uses the processed data for input to an internally running application. The addition of a lens and filter arrangement (13) is optional but in one embodiment may allow bundles of a larger surface area than the detectors sensitised area to be interrogated.

ENHANCEMENTS

The principle behind this invention lends to many novel large scale manufacturing methods. One such method would be to place an array of reels containing the conduits behind a. plane. One or more robotically controlled arms could then be programmed to place the tips of the conduits through a series of pre-drilled holes in a set of plates. Once all the holes are populated a sufficient quantity of chosen polymer with a lower refractive index than the conduit could he poured over the fibres to secure them in place, Once cured the pee-drilled plates could be removed and the surface cut flat and finished. One or more of the aforementioned encapsulation processes can be combined to achieve the final embodiment as a single component.

A further manufacturing method may be realised using existing pick and place technology to roboticaly locate the conduit tips in a pre-cut plate which may or may not become part of the final embodiment. The conduits may he secured using a polymer of suitably low refractive index.

In the above enhancements those skilled in the art will note that if sheathed optical fibres are used then the refractive index of the aforementioned polymer becomes irrelevant.

BENEFITS OF THE INVENTION

The benefits of this invention include, but are not limited to, the manufacture of significantly thinner optical based multi-touch sensitive displays than conventional methods allow. This reduced depth is achieved by using optical conduits to carry light transmissions to the screen and then carry reflections from touch inputs back to the detector. If the conduits are flexible, e.g optical fibres, the detector is free to be placed to one side of the display, thus vastly reducing thickness over camera based systems that require the display to be in full view of the detector. Another advantage of the invention is that the described embodiment presents a method of using the optical conduits to be used as the backlight light diffuser thus alleviating the need for any auxiliary diffusers. The invention describes a possible embodiment that has lower associated manufacturing and component costs than previously documented inventions.

Although the given description references a LCD element for display part of the system, those skilled in the art will anticipate the system would he equally effective using organic light emitting diode, OLED, technology as well as projection based technology with suitable modification.

Other similar methods for optical based multi-touch sensitive displays are detailed in "Fiber-Board, a compact multi-touch display using channeled light" presented at Interactive Tabletop 2009 by D. Jackson and T. Bartindale, and patent application GB0903185.7. The maul difference be-tween our invention and prior art is the transmission of near infrared light through the fibres for illumination purposes. This process of introducing a diffuse illumination source directly though the channeled conduits alleviates the need for an infrared source of light above the display as detailed in Jackson et al and patent application GB0903185.7. The manor in which the light is introduced down the channelled conduits is done in a novel mechanism in order to further reduce system complexity.

The said mechanism is described in detail in the section labeled Summary of the Invention" Fur-ther and above the aforementioned benefits, the presented invention uses a much tighter matrix of optical conduits than described in prior art. This is significant as the described invention would not work on a matrix of the scale mentioned in prior art (patent application GB090318F.7 mentions a mm spaced array) as the acceptance angle is not sufficient to fully illuminate intended touches without the conduits being placed spatially distant from the display; thus increasing thickness.

In addition patent application GB0903185.7 makes reference to an optically transparent inven-tion. This patent describes an invention that deliberately lowers the transparency, but maintains transmisivity, such that the embodiment can replace the existing diffuser layer in a conventional LCD display, While not directly relevant to this invention, Patent US 7 444,887 B2 describes a method for using arrays of optical fibres for reasoning multiple touches over a non-uniform surface. The patent does not however cover the embodiment using an LCD screen or encompass this inventions method of using the optical conduits for transmission and reception of optical impulses.

OTHER EMBODIMENTS

From the foregoing description it will thus be evident that the present invention provides a design for realising large multi-touch displays. As various changes can be made in the above embodiments and operating methods without departing from the scope of the following claims, it is intended that all matter contained in the above description or shown in the accompanying drawings should be interpreted as illustrative amid not in a limiting sense.

Variations or modifications to the design and construction of this invention, within the scope of the appended claims, may occur to those skilled in the art upon reviewing the disclosure herein (especially to those using computer aided design systems). Such variations or modifications are intended to be encompassed within the scope of any claims to patent protection issuing upon this invention.

REFERENCES

* Han, J.Y. Low-Cost Multi-Touch Sensing through Frustrated Total Internal Reflection, In Proceedings of the 18th annual ACM Symposium on User Interface Software and Technology, ACM Press (2005) * D. Jackson and T. Bartindale. "FiberBoard, a compact multi-touch display using channeled light" presented at Interactive Tabletop conference November 2009.

* Patent application GB0903185.7. Multi Touch Sensor Systemn for Display Device.

* Patent US 7,444,887 B2 Ibudi sensor using optical fibre

Claims

CLAIMSThe embodiments of the invention in which I claim an exclusive property or privilege are defined as follows: 1 A multiple input surface formed by one or more optical conduits where the inputs are passed to one or more detectors placed at either end of the optical conduits.
2 As in claim 1 where the surface is combined with a visual display which max or may not be a liquid crystal display.
3 As in claims 1 and 2 where the inputs to the device are carried as optical signals along the optical conduits as either visible or non-visible light to an optical detector which may or may not be a charge coupled device.
4 As in claims 1 2 and 3 where light is passed through the display to illuminate objects close to it and hence cause light to reflect back into an array of optical conduits that route the signals to the detector As in claims 1, 2 and 3 where the signals are present as a result of optical emitters in front of the display and the signals from such emitters are passed through the optical conduit array to a detector 6 As in claims 1. 2, 3 and 4 where the source of illumination is provided by a second array of optical conduits interspersed throughout the first array such as to provide useful illumination of objects close to the display and in front of the sensing array used to gather reflections.7 As in claims 1, 2, 3, 4 and 6 where the illuminating array of optical conduits is also the detecting array of optical conduits for a portion of the time and vice versa such that the task of illuminating and detecting is shared between two arrays where each provided the task of illuminating the other before exchanging their roles.8 As in claims 1, 2, 3, 4 and 6 where the array of optical conduits simultaneously provided the source of illumination and detection of reflected signals.9 As in claims 1, 2, 3, 4 and 6 where the array of optical conduits is split into two or more banks which each fulfil the role of providing illumination above the screen whilst also being used to monitor reflections from objects above the screen surface by periodically switching off or masking their own illumination source for a period of time such as to ailow a detector to process such reflection data.As in claims 1. 2, 3, 4, 6 and 7 where the optical conduit is a fiber optic with or without a cladding of higher refractive index.11 As in claims 1. 2, 3, 4. 6, 7 and 8 where the optical conduit is a fiber optic with or without a cladding of higher refractive index.12 As in claims 1, 2, 3, 4, 6, 7, 8 and 9 where the optical conduit is a fiber optic with or without a cladding of higher refractive index.13 A system of optical fibers which may or may not be cladded in a higher refractive index material, fixed into a support material placed behind a liquid crystal display to route reflection signals produced by illumination of invisible light from objects in front of the display to an electronic detector detector located at the end of a bundle of said fibers.14 As in claim 13 but where the source of illumination is provided by either the same array of optical fibers, which may or may not be cladded in a higher refractive index material, or a different array placed interspersed among the first array or from an emitter placed behind the display.As in claim 14 but where the array of fibers is slit into two or more separate banks which exchange roles of illumination and detecting in the time domain to allow use of the same overall array for both functions.16 As in claim 14 but where the array of optical fibers and the support media is simultaneously used as the display diffuser which may or may not replay the existing diffuser of the display.17 As in claim 14 but where the spacing of the fibers in the array is from 1 mm to 25 mm.18 As in claim 15 but where the spacing of the fibers in the array is from 1 mm to 25 mm.19 As in claim 16 but where the spacing of the fibers in the array is from 1 mm to 25 mm.As in claim 17 but where the spacing of the fibers in the array is from 1 mm to 25 mm.