Photonic touch screen apparatus and method of use

US 7 705 835B2

drawing #0

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A method and an apparatus are disclosed for determining the position of a stimulus in two axes on a surface. The apparatus includes: a transparent waveguide panel with parallel top and a bottom surfaces and at least one edge that is perpendicular to the top and bottom surfaces; a light source that is directed to the edge of the waveguide to produce light that is contained within the waveguide by Total Internal Reflection and a light detector for producing an electrical signal that is representative of an image of the light emitted by the waveguide. The light detector is positioned to receive light emitted by Frustrated Total Internal Reflection from the transparent wave guide when a physical stimulus is placed in contact with the top surface of the transparent waveguide.

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Claims

1. An apparatus for determining position of a stimulus in two axes on a surface, comprising:
A transparent waveguide panel having a top and a bottom surface, which surfaces are parallel to each other, and at least one edge, which is perpendicular to said top and bottom surfaces;
a light source directed to said at least one edge wherein said light source is configured to produce light that is contained within said waveguide by Total Internal Reflection;
a light detector for producing an electrical signal representative of an image of light received;
a first edge on said transparent waveguide panel having a first edge length, which first edge is perpendicular to said top and bottom surfaces;
a second edge having a second edge length, which second edge is perpendicular to said top and bottom surfaces and which is at an angle to said first edge;
wherein said light detector is positioned to receive light emitted by Frustrated Total Internal Reflection from said transparent waveguide when a physical stimulus is placed in contact with said top surface of said transparent wave guide;
wherein said light source is directed to said first edge to produce a plurality of discrete light rays that are contained within said waveguide by Total Internal Reflection and wherein each of said discrete light rays has an emission location which is along the first edge length of said first edge; and
wherein said light detector is comprised of a plurality of discrete light detecting elements distributed along the second edge length of said second edge, said light detecting elements configured to produce an electrical signal representative of light intensity emitted by Frustrated Total Internal Reflection at said second edge when a physical stimulus is placed in contact with said top surface of said transparent wave guide, each light ray detector having a light ray detection location.

Show 6 dependent claims

8. An apparatus for determining position of a stimulus in two axes on a surface, comprising:
A transparent waveguide panel having a top and a bottom surface, which surfaces are parallel to each other, and at least one edge, which is perpendicular to said top and bottom surfaces;
a light source directed to said at least one edge wherein said light source is configured to produce light that is contained within said waveguide by Total Internal Reflection;
a light detector for producing an electrical signal representative of an image of light received;
a first edge, having a first edge length, on said transparent waveguide panel, which first edge is perpendicular to said top and bottom surfaces;
a second edge, having a second edge length on said transparent waveguide panel, which second edge is perpendicular to said top and bottom surfaces and which is at an angle to said first edge;
wherein said light detector is either a single element light detector or a linear light detector positioned to receive light emitted from said transparent waveguide panel by Frustrated Total Internal Reflection when a physical stimulus is placed in contact with said top surface of said transparent wave guide;
wherein said light source is directed to said first edge to produce a plurality of discrete first edge light rays that are contained within said waveguide by Total Internal Reflection wherein each of said discrete first edge light rays has a first edge emission location which is along the first edge length of said first edge;
wherein said light source is further directed to said second edge to produce a plurality of discrete second edge light rays that are contained within said waveguide by Total Internal Reflection and wherein each of said discrete second edge light rays has a second edge emission location which is along the second edge length of said second edge; and
wherein said light detector is configured to produce an electrical signal representative of light intensity emitted from said waveguide panel from said first edge light rays and said second edge light rays by Frustrated Total Internal Reflection when a physical stimulus is placed in contact with said top surface of said transparent wave guide.

Show 4 dependent claims

13. A method for determining a position of a stimulus in two axes on a surface of a transparent waveguide having top and bottom surfaces that are parallel to each other and a first edge that is perpendicular to said top and bottom surfaces and a second edge that is at an angle to said first edge and that is perpendicular to said top and bottom surfaces, comprising:
directing a light source producing discrete light rays to specific emission locations along said first edge to produce discrete light rays that are contained within said waveguide by Total Internal Reflection; and
detecting, at at least one specific detection location along said second edge, light emitted by Frustrated Total Internal Reflection (FTIR) from said transparent wave guide when a physical stimulus is placed in contact with said top surface of said transparent wave guide at a specific stimulus location on said top surface;
associating a specific emission location with a specific detection location when there is a detection of light emitted by FTIR at said specific detection location to determine said specific stimulus location.

Show dependent claim

Description

This application claims priority to, and the benefit of U.S. Provisional Application No. 60/665,727, filed Mar. 28, 2005 for all subject matter common to both applications. The disclosure of said provisional application is hereby incorporated by reference in its entirety.

FIELD OF INVENTION

This invention relates generally to input devices for display screens and more particularly to a system and method for detecting the position of a finger or similar object on a flat transparent surface for use as an interactive two dimensional position input device in conjunction with pointer(s) displayed on a computer or other display screen.

BACKGROUND

Pointer input devices, such as mice, touch pads and the like have been integral parts of computer systems since the advent of graphical user interfaces. In many instances, such as self serve ticket vending terminals and automated teller machines, these devices are impractical and direct tactile contact with the computer screen is the preferred input mode. The variable display on the screen, coupled with the ability to sense the presence and position of a finger on the screen itself provides an efficient means for information entry, whether it is by display of a full keyboard for alpha-numeric entry such as ticket holder name or more limited buttons to press for selections, that can then be changed when a new screen is displayed. Use of such on-screen input, commonly termed touch screen technology eliminates moving parts and wearable contacts required for keyboards and physical buttons and switches and is ideal for many environments.

The touch screen as a tool for graphical user interface (GUI) with a computer is inherently more intuitive, and faster than alternatives such as the mouse or the light pen. The mouse or the light pen is precise but slow, translating the dexterity of the human hand to tedious positioning of a single indicator icon on a screen. The mouse or light pen is difficult to place briefly for high-speed applications such as music composition, game playing, and free hand drawing.

Touch screen technology has largely been implemented with transparent sheets placed over a display screen, wherein the sheets have variable electrical properties (capacitive, resistive, piezo-electric, acoustic, breakbeam IR) that can sense when pressure is applied to a particular area of the sheet. A drawback of the sensing sheets technologies is that the sheets are necessarily less hard and less durable than the glass or other clear panel of the underlying display. Hence these sheets are prone to wear and damage. The breakbeam IR gives false positives. Thus, there is a need for a reliable touch screen technology that works with a clear, sealed panel that is at least as durable as a typical display screen made of glass or acrylic.

Additional disadvantages of current touch screen technology are the high cost of large screens, degradation in screen clarity and excessive bulk that limits the ergonomic adjustment for access to large touch screens. The touch screens in current use are scalable to large size only with substantial increase in cost and bulk, and constrained in the number of simultaneous input positions that can be entered simultaneously, typically one.

Multiple-signal processing with rapid positioning would enable new applications such as rapid manual sorting and positioning of icons on the screen, game playing applications, document creation, music creation, art-work creation, multiple user use, and many other current and future applications.

The optical effect known as Frustrated Total Internal Reflection (FTIR) can be used to detect where an external object has touched a clear optical waveguide. Normally, light transmitted into the edge of a waveguide, which can be a simple flat piece of glass, will not escape the waveguide (e.g., the top or bottom surface of the transparent plastic or glass). When an object, such as a finger, is placed on the surface, however, the index of refraction (versus what was previously just air) is changed and the FTIR takes place. In such a case wherein light will now not be reflected at this point, and partly escapes from the wave guide. The light reflected from the finger is reflected in different directions, including through or out of the waveguide, and within the waveguide in different directions. For a flat piece of transparent plastic or glass, this effect would cause light to leave the surface of the transparent plastic or glass opposite of where a finger is placed. For example, if the edge of a sheet of transparent plastic or glass is evenly illuminated and one touched one surface of the transparent plastic or glass, the area under the point of contact would light up as viewed from under the point of contact. This optical phenomenon is well known, but to date, efficient, robust devices have not been developed to exploit FTIR to produce an effective touch screen input device. The wave guide can be flexible. So long as the material's flex stays within Snell's angle.

BRIEF SUMMARY OF THE INVENTION

A method and an apparatus are disclosed for determining the position of a stimulus in two axes on a surface. The apparatus includes: a transparent waveguide panel with parallel top and a bottom surfaces and at least one edge that is perpendicular to the top and bottom surfaces; a light source that is directed to the edge of the waveguide to produce light that is contained within the waveguide by Total Internal Reflection and a light detector for producing an electrical signal that is representative of an image of the light emitted by the waveguide. The light detector is positioned to receive light emitted by Frustrated Total Internal Reflection from the transparent wave guide when a physical stimulus is placed in contact with the top surface of the transparent waveguide. Several embodiments are presented. These include embodiments where the emitted FTIR light is detected with a two-dimensional detector, such as a camera or a charge coupled device, either of which can be placed below the waveguide. Additional embodiments include detectors placed along an edge of the waveguide where the position of light emitted along one edge and the position of light detected along a second edge are determined to locate the position of the stimulus on the surface of the waveguide. Further embodiments include placing discrete light sources along two edges of the waveguide, detecting the presence of light emitted by FTIR and determining which of the light sources caused the light to be emitted by FTIR.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

The invention will be described in conjunction with the following drawings in which like reference numerals designate like elements and wherein:

FIG. 1 is a side view of an exemplary touch screen position input display system constructed in accordance with this invention as part of a computer system (shown in block diagram form);

FIG. 2 is a side view of an exemplary touch screen position input display system for a projection type display;

FIG. 3 is a side view of an exemplary touch screen position input display system for an LCD display;

FIG. 4 is a top plan view of an exemplary touch screen position input device with light sources on one axis and light detectors at an axis 90 degrees to the source axis;

FIG. 5 is a top plan view of an exemplary touch screen position input device with a limited number of detectors and light sources on two axes;

FIG. 6 is a side view of an exemplary touch screen position input device with light sources along one axis and detectors along an axis at 90 degrees to the source axis;

FIG. 7 is a side view of an exemplary touch screen position input device with light sources along at least one axis and showing a plurality of detector position embodiments.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings wherein like reference characters relate to like parts there is shown one basic exemplary embodiment of a touchscreen panel system 1 for providing position input to a computer display. Element 25 is an LCD or other computer display screen, such as an OLED display. The screen receives its images from a computer system 60. Element 20 is a transparent panel, which is flooded with light on its edge 16 by a lighting element 17. A physical input stimulus 10, which can be a finger or other pointing implement, is shown touching a silicone sheet 15 located over the element 20. The sheet 15 is in optical interface contact with the panel 20. Due to the effect of Frustrated Total Internal Reflection (FTIR), a light ray 30 is refracted out of the panel 20 where the stimulus 10 touches the panel. The silicone sheet 15 indents to interface more closely to the touch panel 20 creating a more uniform response to the stimulus 10, so that different sized pointers and fingers applied to panel 20 produce a more uniform and consistent refraction and reflection leading to light ray 30. The silicon sheet 15 is optional. The same effect can be achieved by pressing the finger directly on the transparent plastic or glass. The touch surface of panel 20 may also be treated to achieve a more complete and uniform contact with the panel, so that different sized pointers and fingers applied with different pressures to panel 20 produce a consistent refraction and reflection leading to the light ray 30. The light ray 30 is passed through a filter 35 to extract unwanted light and enters a photodetector or camera 40. In the exemplary embodiment shown, the camera 40 can be a CCD camera with a two dimensional array of photo sensors. The image created on the camera 40 shows the location of the source of the light ray 30 relative to the display screen 25. A signal interpreter 45 converts the image of the light ray 30 received by the camera 40 into an x/y position data signal. In an embodiment where the touchscreen 20 is used to move an on-screen pointer, mouse/keyboard emulator 50 receives the x/y position data signal and sends location data for a mouse pointer to the computer system 60. The computer system then provides visual feedback 65 by displaying a pointer on the screen, in the same position as the stimulus 10. In an embodiment where the touchscreen is used as a key entry device, wherein the display screen displays alpha numeric keys or dedicated function keys, a mouse/keyboard emulator 50 converts the x/y position of stimulus 10 into a signal indicating that a particular key was pressed.

The FTIR effect is well known to those skilled in the art and is explained, for example in J. Daintith and R. Rennie editors, The Facts on File Dictionary of Physics 4th ed., 2005, p. 250. The total reflection of radiation that can occur in a medium at the boundary with another medium of lower refractive constant. In such cases, rays incident at small angles will be refracted away from the normal; in other words, the angle of refraction (r) is greater than the angle of incidence (i). Because r is greater than i, it is possible to increase i to a value at which r is 90 degrees (or just under). That value of i is called the critical angle c. The relation for the refractive constant for radiation entering this medium is: 1n2=1/sinc. This is an expression of Snell's law as explained further below. If i is increased still further, refraction cannot occur. The radiation must then all be reflected. Normally, when radiation meets the boundary between two media some will be reflected and some will be refracted. Total internal reflection is the only exceptionhere all the energy is reflected. Because of this, optical instruments often include totally internally reflecting prisms rather than mirrors. The critical angles of optical glasses at visible wavelengths are typically 40 degrees or less.

The internal surface of the panel 20 acts as a waveguide which reflects the light from the stimulus, e.g., finger, 10, as regular, or specular reflection, according to Snell's law n=1/sinc . The rough surface of the finger acts as a substantially lambertian or diffuse isotropic reflector, equally bright if viewed from any direction. The diffuse reflection, emits substantially equally over 2 pi steradians, so any detector below the surface may detect the reflection, and any detector along the path of secondary reflections of the FTIR may also detect the light. For a discussion of lambertian reflection, see Friedman E., Miller J. L., Photonics Rules of Thumb 2nd edition 2003, SPIE Press-McGraw Hill New York, pp 341-42. For a diagram of the radiance pattern of a lambertian source compared with a highly directional source, such as a laser diode, see Keiser, G. Optical Communications Essentials McGraw-Hill New York 2003, pp 120-121 The use of FTIR for a pointing device of limited size is disclosed in U.S. Pat. No. 6,320,177 to Sayag and the optical effect is described therein at column 6, lines 4-25 and FIGS. 2 and 3. The entire disclosure of Sayag is incorporated by reference herein.

Citations

US 6,948,820 B2 - Interactive display system having an optical channeling element
A display system includes a waveguide optical panel having an inlet face and an opposite outlet face. A projector and imaging device cooperate with the...

US 6,927,384 B2 - Method and device for detecting touch pad unit
A method and system for detecting the presence of an object at a touch pad device, wherein the touch pad device has a designated interaction...

US 2006 114,237 A1 - Method and system for providing a frustrated total internal reflection touch interface
A method and system for providing a touch interface on a display are described. The method and system include providing an emitter on a first...

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