WO2003063069A2

WO2003063069A2 - Touch screen

Info

Publication number: WO2003063069A2
Application number: PCT/US2003/001988
Authority: WO
Inventors: Ying-Moh Liu; Lawrence M. Cuprys; Richard D. Tompkins
Original assignee: KAISER ELECTRONICS A ROCKWELL-COLLINS Co
Current assignee: KAISER ELECTRONICS A ROCKWELL-COLLINS Co
Priority date: 2002-01-24
Filing date: 2003-01-22
Publication date: 2003-07-31
Anticipated expiration: 2004-07-24
Also published as: AU2003217238A1; WO2003063069A8; WO2003063069A3

Abstract

A display screen for projected images can act as a touch screen through use of IR sources with homogenizers to create an area of illumination in a plane parallel to and adjacent the screen surface. The presence of a finger or pointer reflects a portion of the illumination to a detector remote from the screen. The detector is capable of identifying the x-y location on the screen of the light spot being detected. In an alternative embodiment in which the use of a finger or other pointing device is impractical, a laser pointer, equipped with an IR source, projects a light spot on the screen whose x-y location can uniquely be determined by the detector device.

Description

TOUCH SCREEN

This is a continuation-in-part of United States Provisional Application Serial Number 60/351,929, filed January 24, 2002, the priority of which is claimed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to input devices and more particularly, a manually operable position sensing device for use with a data processing system. 2. Description of the Related Art

There are many types of touch screens commercially available. The commercial applications are, for example, on some bank ATMs, automobile navigation displays, and vehicle instrument panels. More recently, touch screens have been proposed for voting machines. A typical touch screen system is disclosed in the patent to Denlinger, Pat. No. 4,782,328, which shows a touch screen that uses ambient light reflected from a pointer (such as a stylus, finger, or other device) in two optical sensor units at adjacent corners of the screen. Each optical sensor includes a lens and a line array of photo detectors. The angles of the detected images trigonometrically determine the position of the pointer.

Other devices operate on the principles of pressure sensing, such as the photo elastic screen taught in the patent to Kasday, Pat. No. 4,710,760 which employs light emitting and detecting modules at adjacent corners. The photo elastic screen changes the polarization of light which is detected and the intersection of the detected light beams can be determined, representing position. Yet another system, which uses a single source/detector in one corner of the screen is taught in the patent to Griffin, Pat. No. 4,553,842. Here a special reflecting structure is arranged about the periphery of the screen and the desired position is determined geometrically. Surface acoustic wave (SAW) sensing is also a common technique for determining the position of a pointer, as is resistive coupling, or infrared sensing. None of these are optimal for use with high resolution multifunction displays ("MFDs") and, in particular, rear projection MFDs commonly used in avionics applications . When adding a touch screen feature onto a high performance rear projection display system, it is important that there be no devices obscuring the path of light. As such, some of the conventional methods of touch screen sensing, which incorporate pressure sensitive meshes or other matrix screen structures in the back of the display are not suitable, as they would degrade display performance.

For touch screens that employs SAW, the acoustic waves are generated by using two piezoelectric transducers. The acoustic waves are subject to interference from ambient acoustic noises and could have higher false finger position rates if used in noisy environments.

Resistive coupling touch screens use a voltage gradient over a plastic-on-glass membrane overlay to sense "touch". A thin, clear conductive metal oxide layer is coated on the facing sides which are held apart by spacers. A uniform voltage distribution is first driven across the membrane. The touching finger can press the two layers together to create a signal voltage to the controller that translates the signal into coordinates. Due to the thin membrane that is used, this approach could be frag- ile and is not suitable for outdoor applications, or those applications exposing the screen to harsh environments.

Infrared (IR) touch screens typically utilize an array of infrared emitters that illuminates along the horizontal direction (X) . Another array of infrared emitters illuminates in the vertical direction (Y) . Two corresponding arrays of IR detectors are employed to sense the continuity of the light paths from the emitters. When a finger blocks one of the light paths in the X and Y directions, the detectors can easily locate the X-Y coordinates of the pointing finger. The major concern with this approach is that the touch - screen typically requires many IR emitters and detectors, which can incur a substantial material cost, especially when night vision goggle (NVG) compatibility is essential. Also, the system resolution of finger position is low due to the relatively low number of sensors. As the number of IR components increases, the resolution increases but the system reliability issues also increase and the system MTBF (Mean Time Before Failure) is reduced. Additionally, this approach requires spacing around the periphery. Accordingly, it would be most attractive to have a touch screen that requires the use of only a limited number of IR components .

SUMMARY OF THE INVENTION

The present discussion sets forth the basic principles of a novel touch screen that incorporates an IR light source assembly that is NVG compatible, only requires 1 or 2 laser diodes or equivalent illumination sources and a position sensor. The invention is primarily intended for use with rear projection display monitors.

As the need for rear projection displays grows stronger, it is important to provide improved touch screen operation capabil- ities. In many military applications, the display needs to be

NVG compatible, that is, the display and its touch screen functions cannot emit light in the wavelength region to which the NVG device is sensitive, which precludes any significant emission in the wave length range from 630 to 930nm The dis- play/touch screen also needs to be operational both day and night over a wide range of ambient conditions.

The display screen is illuminated from left and right sides of the screen, using laser diodes or LEDs with a center wavelength above the range of visible light. For NVG-compatible applications, the center wavelength would be below 600 nm or above 980nm to alleviate interference with the NVG device.

The light source outputs are fed into a ho ogenizer, whose function is to distribute the light uniformly over the entire display screen. Various homogenizer designs are described in the prior art and they are applicable to this invention, with some modifications. Devices incorporating small, spherical bumps or wedge-shaped optical devices are examples of homogenizers that are useful in the present invention.

The homogenizer output light is designed to exhibit a slight degree of divergence in a direction that is normal to the plane of the display screen. The divergent light illuminates a finger or stylus, which reflects part of the light back toward an optical position sensor. In the preferred embodiment, the rear projected image illumination has been filtered so that a small percentage of IR light reaches the projection screen. The IR light incident upon the optical sensor is then primarily that which is reflected from the finger or pointer that is positioned adjacent to or touching the screen. The signal IR level must be much higher than the noise IR level (which consists of components from the projector and components from the ambient environment) . This ratio is essential for the success of the pres- ent invention.

The sensor can be either a 2-dimensional CCD array, a 2-d CMOS sensor, or a lateral effect position sensor. Even though a CCD camera can be employed in theory, its size may be too great to allow integration into a rear projection display. Accord- ingly, a smaller sized photo detector package is preferable. A 2-d CMOS sensor could be a good candidate for its small size and built-in digital functionality.

Compact lateral effect position sensors are currently available with a 10mm square active sensing area and an overall package size of 1" in diameter. When operated together with simple analog electronics, such a device could provide accurate X-Y position information relative to the area of highest IR intensity on the sensor, which would correspond to the X-Y location of a finger, stylus or other pointing device. Based on this X-Y position, additional electronics and software can activate the proper response corresponding to the symbology represented by the point of finger or other pointer contact. The lateral effect sensor can also be operated in an AC coupled mode, which allows filtering of unwanted DC background, such as ambient IR light, thereby increasing the system signal to noise ratio (SNR) . This is an additional advantage over the prior art IR touch screens, which implement a light plate assem- bly in front of the display that is fully exposed to the ambient IR light, which reduces the system SNR and increases the rate of "false" position sensing.

When operating the sensor in the AC coupled mode, the laser diodes or LEDs also need to be operated in a pulse mode, synchronized to the sensor. If there is a constant level of IR illumination received on the sensor from either the display or the ambient environment, operating the sensor in the AC mode will tend to filter out the DC background and only the pulsed IR signal from the laser diodes will be recognized as the proper data.

The lateral effect sensor is made of silicon, and hence, its spectral response diminishes at about llOOnm. Therefore, when choosing a light source, the central wavelength needs to be at 1060nm or lower so that there will be a significant amount of detectable signal.

GaAs based photo-detectors are available for detection above llOOnm. However, they are not designed for lateral effect sensor use. Notwithstanding the availability of laser diodes with wavelengths up to 1300nm, they are not useful in this application. A CCD camera made of InGaAs can detect up to about 1700nm, but a 2D array could be very expensive and not suitable in the environment of a projection display. Moreover, such a camera typically needs cooling, which would require additional space and extra maintenance and make it less attractive.

A CCD array with high frame rate of about 1000 frames per second would be most desirable since it can be synchronized to a pulsed light source for reducing ambient noise and improving the signal to noise ratio. A video processing electronics system is required to process the digitized data in order to extract position information.

An imaging lens attached to the front of the lateral effect sensor can be made of inexpensive lens materials. The sensor position resolution is typically about 12μm and is a function of the detector electronic circuit and optics resolution. As an example, when using a lOxlOmm sensor to map out a 150x150mm display, the optical magnification is 15X, and thus, the touch- screen system position sensing resolution can be as good as 15xl2um or 180μm. Comparing this resolution with other IR touch screen designs that provide about 9.5mm position resolution, a major performance improvement in position accuracy and resolu- tion can be achieved.

In addition, conventional IR touch screens use a light plate, which includes all the IR emitters and detectors, in front of the display. When a finger moves across the display searching for the desired symbology to activate, an erroneous action may be triggered due to the finger blocking the IR light at an incorrect location. The present invention can require the finger to actually touch the screen to activate the selection. During finger motion in front of the screen, the reflected light intensity received at the sensor is much lower than a predeter- mined activation threshold level, thereby avoiding false operation.

Some level of optical distortion may still be acceptable, because it can be mapped and corrected in the software and electronics. This approach should allow for a smaller footprint than required by a CCD camera and is more economical than currently available IR emitter/detector arrays for the rear projection display.

There are occasions when a "touch screen" feature is desirable with large projection displays. However, there are in- stances when it is not convenient to actually touch the screen with a finger or a pointer. For these situations, a visible laser pointer may be used during a presentation to note features of interest. If a touch screen effect is desired, the laser pointer can be equipped with a separately actuable IR source which places an IR spot at the location to which the visible laser was directed. That IR spot and its location on the display can be detected and signaled by the optical sensor.

While such a variation can be utilized with the IR illuminated touch screen of the preferred embodiment, in a very large display where physical contact with the screen is difficult or impractical, the dual mode laser pointer can be used without need for the IR sources and homogenizers which illuminate the screen periphery. This embodiment may be considered a "touch screen", as well, even though there is no physical contact with the screen surface.

The reliability of this alternative embodiment can be improved through the use of a well focused light beam with a sufficiently small spot on the screen. A dual mode laser pointer could be a good choice with both beams par-focal by using a focusing mechanism.

In order for the highly directional IR beam to be detected by a sensor, a certain amount of scattering is needed from the screen. For example, pure optical glass has very low scattering and would not be suitable. Similarly, ground glass is highly scattering and may lose too much of the signal to be detected. Accordingly, the screen must be chosen with the requirement that the beam can be detected over a wide range of angles of incidence of the impinging beam.

The novel features which are characteristic of the invention, both as tp structure and method of operation thereof, together with further objects and advantages thereof, will be understood from the following description, considered in connection with the accompanying drawings, in which the preferred embodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only, and they are not intended as a definition of the limits of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example of a prior art touch screen using infra red light; FIG. 2 is a graph of NVIS spectral response curves;

FIG. 3 is a front view of a touch screen according to the present invention;

FIG. 4 is side and partially perspective view of the touch screen of FIG. 3; FIG. 5 is a partial perspective side view of the touch screen device of FIG. 4 with reference to the function of the optical detector assembly; and FIG. 6 is a side view of an alternative embodiment of the present invention in which a dual mode laser pointer places an IR spot on the screen which can be detected.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning first to FIG.l, there is shown a typical prior art touch screen 10 which incorporates a plurality of IR emitters 12 along two adjacent edges 14, 16 of a square or rectangular panel 18 and a comparable plurality of IR sensors 20 arrayed along facing edges 22, 24. Each of the emitters 12 is directed to an IR sensor 20. So long as all of the IR sensors 20 receive illumination, appropriate signals are provided to the signal processing elements that indicate that no pointing activity has been encountered. In operation, when a finger, pointer or other object (not shown) is applied to the panel 18, selected ones of the IR sensors 20 will receive little or no signal as the result of the presence of the finger or pointer interrupting the beam. The relative x- y location on the screen is then determined by which of the sensors 20 receives no IR illumination.

The resolution of such a prior art system is extremely limited, depending upon the number and placement of IR emitters 12 and IR sensors 20. If resolution is not a consideration, then a reasonable number of emitter-sensor pairs could be fabricated at an acceptable cost level.

Turning next to FIG. 2, a graph 30 is provided to illustrate the regions of sensitivity to radiation exhibited by NVIS equipment currently in use. Wavelength is plotted along the x-axis while relative sensitivity is plotted along the y-axis. A first curve 32 represents the sensitivity of the NVIS A systems and a second curve 34 represents the sensitivity of the NVIS B systems. As shown, the NVIS A sensitivity curve 32 rises at a wavelength of approximately 600 nanometers while the NVIS B sensitivity curve 34 rises at a wavelength of approximately 650 nanome- ters. The decrease in sensitivity appears to be the same for both and it occurs at approximately 910 nanometers. From these curves, it can be safely assumed that IR radiation of a wavelength greater than 1,000 nanometers or less than 600 nanometers will not affect NVIS equipment.

Turning next to FIG. 3, there is shown a touchscreen 40. A pair of IR light sources 42 are positioned at the base of opposing edges 44, 46 of the touchscreen 40. A pair of homogenizer strips 48, 50 are aligned with respective ones of the pair of light sources 42, and act to diffuse and distribute the IR illumination over the surface of the display panel 52 portion of the touch screen 40. The homogenizer strips provide a diverging pattern of illumination which impinges upon the panel 52 surface and also illuminates an area that is displaced from the surface of the panel 52.

In FIG. 4, there is shown an optical sensor assembly 54 which views the entire surface of the panel 52 and is sensitive to IR light. In a preferred embodiment, the optical sensor assembly 54 is a sensor which can signal the x-y location of the source of impinging light.

In FIG. 4, only one of the homogenizers 48, 50 need be shown. As a finger or other pointing object 56 approaches the panel 52, the diverging light beam 58 strikes the leading end of the object 56 and some of the light reflected from the object 58 passes through the panel 52 and is detected by the optical sensor assembly 54. Because the end of the finger or object 56 is illuminated, the relative location of that image with respect to the panel 52 can be determined and signaled by the sensor assembly 54. For greater sensitivity, the light source 42 can be pulsed and the assembly can be synchronized to the pulses to minimize the chance of erroneous readings of the position of the finger or pointing object 56. The alternative embodiment of FIG. 5 is substantially similar to that of FIG. 4. In this embodiment, however, the optical sensor assembly 54' can be a CCD or CMOS sensor with an appropriate lens system for placing an image of the panel 52" over the active array so that the appropriate CCD element will respond to reflected IR light at a location on the panel 52' . Providing a pair of sources 42' with homogenizers 48' (only one of which is shown) increases the illumination reflected from the finger or pointing object 56', which shows up as a bright spot on the surface of the panel 52 ' .

Turning next to FIG. 6, there is shown an alternative embodiment of the present invention that is useful with projected dis- plays where the actual touching of the screen is difficult or impractical. In this embodiment, a laser pointer 60 or other optical beam device may be used to direct the viewer' s attention to a particular area on the screen image. While the use of a laser or other light spot is adequate for a viewer, the detection circuitry and especially the chosen optical detector 62 will have difficulty selecting the applied pointing beam which is, appropriately, within the visible range of wave lengths.

To make the illuminated spot 64 visible to the optical detector, the pointer 60 includes an IR source that is coaxial with the laser or other light spot and is alternatively energizable. Once the spot to be identified has been selected, the laser or other light spot is switched off and the IR source is turned on, placing a spot of IR illumination on the screen at the same place that was previously illuminated by the visible spot. The optical device 62, being highly sensitive to IR radiation, can signal the location of the IR spot, effectively accomplishing the same result as with a finger or pointer in the preferred embodiment.

Thus, there has been shown, in alternative embodiments, an improved "touchscreen" device which uses IR sources to create a shallow illuminated area adjacent the display screen of the image projector. A detection device, which can signal the x-y coordinates of a light source is employed to work in conjunction with a finger or other pointer object. The finger/object then reflects light from the illuminated area to the detector which determines the location of the source of that reflected light, which is the pointing object.

In alternative embodiments, a laser pointer can be provided with a secondary IR source which, when energized, illuminates a spot on the screen which can be detected and located by the sensor. Modifications and other embodiments will occur to those skilled in the art as a result of the present disclosure. Accordingly, the scope of the invention should be limited only by the scope of the claims appended hereto. WHAT IS CLAIMED IS NEW IS:

Claims

1. A touch screen device, comprising: a translucent display screen adapted to display images, said screen including a front surface and a back surface; infrared signal generation means for generating a plane of illumination adjacent and substantially parallel to said front surface; optical sensor means positioned to view said back surface for generating a signal when said front surface is illuminated by a localized spot of infrared light.

2. The device of Claim 1 wherein said infrared signal generation means comprises an infrared light source.

3. The device of Claim 2 further comprising at least one homogenizer disposed near said infrared signal generation means for diffusing said infrared light.

4. The device of Claim 1 wherein said optical sensor means comprises a sensor which generates, in response to the presence of a localized spot of infrared illumination, an x-y position signal corresponding to and representative of the location of the local- ized infrared spot on said screen.

5. The device of Claim 1 wherein said optical sensor means comprises an array of CCD sensors and a lens, said lens being disposed between said CCD sensors and said screen.

6. The device of Claim 1 wherein said optical sensor means comprises an array of CMOS sensors and a lens, said lens being disposed between said CMOS sensors and said screen.

7. The device of Claim 1 further comprising a signal modu- lation means coupled to said infrared signal generation means for pulsing said infrared signal generation means on and off.

8. The device of Claim 7 wherein said optical sensor means is responsive to an infrared signal only when said infrared signal generation means is turned on.

9. A system for indicating a position on a screen display, comprising: a touch screen device comprising a translucent display screen adapted to display images, said screen including at least a back surface, and optical sensor means positioned to view said back surface for generating a signal when said surface is illuminated by a localized spot of infrared light; and a position indicating means comprising a laser pointing device including a source of infrared light.

10. A touch screen device, comprising: a translucent display screen having front and back surfaces adapted to display images, said screen including at least one edge, and substantially defining a plane; at least one infrared light source positioned along said at least one edge; at least one homogenizer positioned adjacent to said infrared light source, said infrared light source and said homogenizer working together to produce a plane of illumination adjacent and substantially parallel to said front surface of said screen; an optical sensor assembly positioned to view said back surface of said screen, said optical sensor producing a signal in response to illumination from a localized infrared light spot; whereby when a pointing object is placed within said plane of illumination, infrared light is reflected from said pointing object to create a localized infrared light spot on said screen to be viewed by said optical sensor.

11. The device of Claim 10 wherein said optical sensor assembly produces a signal indicating the x-y position of a local- ized infrared light spot on said screen.

12. The device of Claim 10 wherein said optical sensor means comprises an array of CCD sensors and a lens, said lens being disposed between said CCD sensors and said screen.

13. The device of Claim 10 wherein said optical sensor means comprises an array of CMOS sensors and a lens, said lens being disposed between said CMOS sensors and said screen.

14. The device of Claim 10 further comprising a signal modulation means coupled to said infrared signal generation means for pulsing said infrared signal generation means on and off, and wherein said optical sensor means is responsive to an infrared signal only when said infrared signal generation means is turned on.

15. The device of Claim 10 wherein there are two infrared light sources and two homogenizers, and wherein said infrared light sources are positioned at diagonally opposed corners of said front surface of said screen, and a homogenizer is positioned adjacent to each of said infrared light sources.

16. A touch screen device, comprising: a translucent display adapted to display images, said screen having first and second surfaces; a first infrared light source positioned along a first edge of said screen first surface; a first homogenizer positioned adjacent to said first infra- red light source; a second infrared light source positioned along a second edge of said screen, said second edge being opposite said first edge; a second homogenizer positioned adjacent to said second infrared light source wherein said first and second homogenizers are responsive to infrared light from said first and second infra- red light sources to create a region of infrared illumination slightly adjacent and substantially parallel to said first surface of said screen; and an optical sensor positioned to view said second surface of said screen, said optical sensor being responsive to a localized infrared light spot on said screen for producing a signal corresponding to and representative of the x-y position of an an applied localized infrared light spot on said screen; whereby when a pointing object is placed within said plane of illumination, infrared light is reflected from said pointing object to create a localized infrared light spot which can be viewed by said optical sensor.

17. The device of Claim 10 further comprising a signal modulation means coupled to said infrared signal generation means for pulsing said infrared signal generation means on and off, and wherein said optical sensor means is responsive to an infrared signal only when said infrared signal generation means is turned on.

18. The device of Claim 16 wherein said optical sensor means comprises an array of CCD sensors and a lens, said lens being disposed between said CCD sensors and said screen.

19. The device of Claim 16 wherein said optical sensor means comprises an array of CMOS sensors and a lens, said lens being disposed between said CMOS sensors and said screen.

20. A touch screen device for use with a projected display comprising: a. a screen adapted to display projected images; b. a first IR light source positioned along one edge of said screen for creating a plane of IR illumination, substantially parallel to the plane of said screen; c. IR responsive image capturing and signaling means for generating a signal representative of the location on the screen of a localized IR spot; whereby a pointing object in the plane of IR radiation reflects a portion of the IR radiation toward said screen to create a local- ized IR spot that can be recognized and the position of which on said screen can be signaled by said image capturing and signaling means .

21. Apparatus as in claim 20, further including light homog- enizer means arranged along an edge of said screen adjacent said IR light source and wherein said homogenizer means distribute applied IR radiation into said plane of illumination.

22. Apparatus as in claim 20, wherein said image capturing and signaling means determines the X and Y coordinates of a local- ized IR spot and creates signals representative of such X and Y coordinates .

23. Apparatus as in claim 20, wherein said image capturing and signaling means include IR detector means for generating a signal corresponding to and representative of the x-y location of the detected image on said detector means .

24. A touch screen apparatus comprising: a. a display screen for providing images to a remote viewer; b. an IR light source adjacent said display screen; c. homogenizer means coupled to said display screen and responsive to IR light from said IR light source for creating a region of IR illumination adjacent the viewing surface of the display screen; and d. position sensor means adapted to detect localized IR bright spots on said display screen and for signaling the X-Y location of detected localized IR bright spots; whereby pointing means, when placed adjacent a selected element of an image on said display screen, reflects an IR bright spot posi- tioned at the selected image element which is detected by said position sensor means to generate signals representing the X-Y location of the reflected IR bright spot and thus the X-Y location of the selected image element for use by an information processing system.

25. The touch screen apparatus of claim 24 wherein said IR light source is positioned at one corner of said display screen and wherein the apparatus further includes a second IR light source positioned at a corner opposite said one corner, and further includes second homogenizer means adjacent said second IR light source, coupled to said display screen and responsive to IR light from said second IR light source for adding to the region of IR illumination adjacent the viewing surface of the display screen.

26. A touch screen apparatus for use with a projected display comprising: a. a screen adapted to display projected images; b. IR responsive image capturing and signaling means for generating a signal representative of the location on the screen of a localized IR spot; and c. a light pointing device including a IR radiation source for directing a localized IR spot to a desired x-y location on said screen; whereby pointing IR radiation toward said screen creates a local- ized IR spot that can be recognized and the position of which on said screen can be signaled by said image capturing and signaling means .