KR101035253B1 - Touch screen signal processing - Google Patents

Abstract

Having a light source 4 at one or more edges of the screen 1 for directing light across the surface of the screen 1 and an electronic output located around the screen 1 for receiving light from the light source 4. A touch screen 1 using at least two cameras 6 is disclosed. The processor employs triangulation to receive the output of the camera 6 and to determine the position of the object in the vicinity of the screen 1. Detecting the presence of an object uses the screen surface as a mirror to detect the presence or absence of direct light attributable to the object at the camera 6 and the presence or absence of reflected light attributable to the object at the camera 6. It includes. The light source 4 can be modulated to provide a frequency band at the output of the camera 6.

Optical, touch screen, display, camera, processor, frequency

Description

Touch Screen Signal Processing {TOUCH SCREEN SIGNAL PROCESSING}

TECHNICAL FIELD The present invention relates to touch sensitive screens and, more particularly, to optically detecting the presence of an object using signal processing.

Prior art touch screens can take five main forms. These five types of touch screen input devices include resistive, capacitive, surface acoustic waves (SAW), infrared (IR), and optical types. Each of these five types of touch screens has its own features, advantages and disadvantages.

Resistive touch screens are the most common form of touch screen technology. It is a low cost solution found in many touch screen applications, including portable computers, PDAs, consumer electronics and point-of-sale applications. Resistive touch screens use a controller and a glass overlay coated on the display surface to produce a touch connection. The main types of resistive overlays are 4-wire, 5-wire, and 8-wire. 5-wire, and 8-wire techniques are expensive to manufacture and calibrate, and 4-wire yields low image clarity. Two options are given, either polished or antiglare. Polishing results in clarity of the image, but generally introduces glare. Antiglare minimizes glare, but makes light more diffuse and thereby reduces clarity. One advantage of using a resistive display is that it can be accessed with a finger (with or without gloves), a stylus or a hard object. However, resistive displays are less affected in public environments due to degradation in image clarity caused by layers of resistive films. Despite the tradeoffs, resistive screens are the most popular technology because of their relatively low cost (in small screen sizes) and input range capabilities (finger, gloves, hard and soft stylus).

Capacitive touch screens are all glass and designed for use in ATM and similar kiosk type applications. A small current flows across the screen by a circuit located at the edge of the screen to measure the capacitance of the person touching the overlay. Touching the screen cuts off the current and launches the software that runs the kiosk. Because the glass and the bezel mounting it to the monitor can be sealed, the touch screen is durable and resistant to water, dust and stains. This makes it common in harsh environments such as gaming, retail store displays, public kiosks and industrial applications. However, capacitive touch screens are only activated by touch by a human finger and do not operate with gloved fingers, pens, stylus or hard objects. Therefore, it is not suitable for use in many applications, including medical and food preparation.

Surface acoustic wave (SAW) technology provides good image clarity because it uses a pure glass structure. SAW touch screen uses a glass display overlay. Sound waves propagate across the surface of the display. Each wave spreads across the screen by striking the reflector array along the edge of the overlay. Two receivers detect sound waves. When the user touches the glass surface, the user's finger absorbs some of the energy of the acoustic wave and the controller circuit measures the touch position. SAW touch screen technology is used in ATMs, amusement parks, banking and investment applications, and kiosks. This technique cannot be sealed with a gasket and therefore is not suitable for many industrial or commercial applications. Compared to resistive and capacitive technologies, this provides excellent image clarity, resolution and high light transmission.

Infrared technology relies on interruption of the infrared light grid in front of the display screen. The touch frame or the opto-matrix frame includes a row of infrared LEDs and photo transistors; Each is mounted on two opposite sides to create a grid of invisible infrared light. The frame assembly consists of a printed wiring board with opto-electronics and is hidden behind the infrared transmission bezel. The bezel allows the infrared beam to pass while shielding the optoelectronics from the operating environment. The infrared controller sequentially pulses the LEDs to create a grid of infrared light beams. When a stylus like a finger enters the grid, it obstructs the beam. One or more phototransistors detect the absence of light and transmit a signal identifying the x and y coordinates. Infrared touch screens are often used in manufacturing and medical applications because they can be completely sealed and operated using any number of soft or hard objects. The main problem with infrared is to “sitting” the touch frame, ie slightly above the screen. As a result, the finger or stylus is vulnerable to "early maneuvering" before actually touching the screen. The manufacturing cost of the infrared bezel is also quite high.

Optical imaging for touch screens uses a combination of line-scan cameras, digital signal processing, residual or back illumination, and algorithms to determine touch points of view. The imaging lens images the user's finger, stylus or object by scanning along the surface of the display. This type of touch screen is vulnerable to error reading due to the movement of shadows and bright light and also requires the screen to be touched before the reading is done. Several attempts have been made to overcome these shortcomings. Touch screens using optical imaging techniques are disclosed in the following patent documents.

A touch screen using digital ambient light sampling is disclosed in US Pat. No. 4,349,806, in detail this patent discloses a touch input that continuously samples and stores ambient light readings and compares them with previously made readings. This is done to minimize bright light and shadow effects.

Touch screens for use in computer systems are disclosed in US Pat. No. 5,914,709. In particular, a touch sensitive user input device using threshold adjustment processing is disclosed. The light intensity value is read and an "ON" threshold is established, and this threshold measurement and adjustment is performed frequently and periodically.

US Patent 5317140 discloses a method for optically determining the position and orientation of an object on a touch screen display. Specifically, the diffuser is placed above the light source to yield an average light intensity on the touch screen.

US Pat. No. 5698845 discloses a touch screen display using an optical detection device for modulating the ON / OFF frequency of an optical emitter at a frequency twice that of a commercial AC line source. The receiver determines the presence of light and compares it with the actual signal transmitted.

US Pat. No. 4,528,28 discloses a touch screen that uses a light generator unit positioned at a predetermined height above the touch screen, and that when the pointer is near the touch screen, a ray of reflected or shaded ambient light can be detected. have.

US patent 4868551 discloses a touch screen capable of detecting a pointer near the surface of the display by detecting light reflected (reflected or diffused) by the pointer.

It is an object of the present invention to provide a touch-sensitive screen that overcomes the above drawbacks or provides at least a useful choice for the public.

Therefore, the first aspect of the present invention,

A screen on which the user can touch and view the image on or through the screen;

A light source at one or more edges of said screen, said light source directing light across the surface of said screen;

At least two cameras having outputs, each of the cameras being positioned around the screen to image a space in front of the screen, the outputs comprising a scanned image;

Means for processing the output to detect a level of light, wherein the light is:

Direct light from the light source, and / or

The means comprising light reflected from the light source; And

A processor to receive the processed output of the camera, the processor to determine if the processed output indicates the presence of an object near the screen and if so the processed output to determine the location of the object And a triangulation method.

Advantageously, said processed output indicates a relative bearing of the estimated object position relative to said camera.

Preferably said processed output indicates the relative orientation of the estimated object position with respect to the center of the lens of said camera.

Preferably the processor determines the position of the object as flat screen coordinates.

Preferably the light source is behind the screen arranged to project light through the screen and the display directs the light emitted from the light source across the surface of the screen at each edge having a light source. It includes a light deflector in front of the.

Preferably the camera is a line scan camera, the camera output includes information about the scanned line and the processor uses the information about the scanned line in determining the position of the object.

Preferably the touch display is:

Means for modulating the light from the light source to provide a frequency band within the imageable range of the camera; And

Means for excluding image data outside the frequency band.

Advantageously, said means for processing said output comprises said means for excluding image data outside said frequency band and said means for excluding image data outside said frequency band includes filtering.

Preferably the filtering is;

Comb filters;

High pass filter

Notch filter

And applying a filter selected from the group consisting of band pass filters.

Preferably the touch display is

Means for controlling the light source; And

Means for capturing and processing an image taken in a lighted state and in a non-lighted ambient light state,

The means for processing the output subtracts ambient light from the light splitting to detect the level of light.

Preferably the light sources are LEDs and the touch display comprises means for controlling the operation of a section of the light source independent of the other sections of the light source.

Preferably means for controlling the operation of the section of the light source comprises means for independently controlling the effective intensity of the light source.

Preferably said means for controlling the section of said light source comprises wiring said light source with antiphase and driving it using a bridge drive.

Preferably the means for controlling the section of the light source comprises using a diagonal bridge drive.

Preferably said means for controlling sections of said light source comprises using a shift register for causing each section to be controlled.

Preferably said means for capturing and processing an image comprises controlling each of said cameras and sections of said light source and means for processing said outputs to process information as to whether said section is illuminated or not. It includes.

Preferably, when the image is taken, some sections are illuminated and others are not.

Therefore, the second aspect of the present invention,

A screen on which the user can touch and view the image on or through the surface;

A light source at one or more edges of said screen, said light source directing light across the surface of said screen;

At least two cameras positioned around the screen and having an output, wherein the camera is positioned so as not to receive direct light from the light source, each camera imaging a space in front of the screen, and the output captures the scanned image At least two cameras;

Means for processing the output to detect a level of reflected light; And

A processor to receive the processed output of the camera, the processor to determine if the processed output indicates the presence of an object near the screen and if so the processed output to determine the location of the object And a triangulation method.

Advantageously, said processed output indicates the relative orientation of the estimated object position relative to said camera.

Preferably said processed output indicates the relative orientation of the estimated object position with respect to the center of the lens of said camera.

Preferably the processor determines the position of the object as flat screen coordinates.

Preferably the touch display is:

Means for modulating the light from the light source to provide a frequency band within the imageable range of the camera; And

Means for excluding image data outside the frequency band.

Advantageously, said means for processing said output comprises said means for excluding image data outside said frequency band and said means for excluding image data outside said frequency band includes filtering.

Preferably the filtering is;

Comb filter;

High pass filter

Notch filter

And applying a filter selected from the group consisting of band pass filters.

Preferably the touch display is

Means for controlling the light source; And

Means for capturing and processing an image taken in a lighted state and in a non-lighted ambient light state,

The means for processing the output subtracts ambient light from the light splitting to detect the level of light.

Preferably the light sources are LEDs and the touch display comprises means for controlling the operation of a section of the light source independent of the other sections of the light source.

Preferably means for controlling the operation of the section of the light source comprises means for independently controlling the effective intensity of the light source.

Preferably said means for controlling the section of said light source comprises wiring said light source with antiphase and driving it using a bridge drive.

Preferably the means for controlling the section of the light source comprises using a diagonal bridge drive.

Preferably said means for controlling sections of said light source comprises using a shift register for causing each section to be controlled.

Preferably said means for capturing and processing an image comprises controlling each of said cameras and sections of said light source and means for processing said outputs to process information as to whether said section is illuminated or not. It includes.

Preferably, when the image is taken, some sections are illuminated and others are not.

Preferably the screen is reflective, the camera further images the screen and the means for processing the output detects the level of light from the mirror image.

Advantageously, said processed output indicates the distance of said object from said screen and the relative orientation of the estimated object relative to said camera.

Accordingly, a third aspect of the invention provides a method for receiving user input in association with an image,

Providing a screen on which the user can touch and view the image on or through the screen;

Providing the light source at one or more edges of the screen and directing light across the surface of the screen;

At least two cameras having outputs, each of the cameras being positioned around the screen to image the space in front of the screen, the outputs comprising the scanned image step;

Processing the output to detect a level of light, wherein the light comprises:

Direct light from the light source, and / or

Said light comprising light reflected from said light source; And

Processing the processed output of the camera using triangulation to obtain the position of the object.

Advantageously, said processed output indicates the relative orientation of the estimated object position relative to said camera.

Preferably said processed output indicates the relative orientation of the estimated object position with respect to the center of the lens of said camera.

Preferably the location is in flat screen coordinates.

Preferably the light source is behind the screen arranged to project light through the screen and the display is at the front of the screen directing the light emitted from the light source across the surface of the screen at each edge with the light source. Contains an optical deflector in the.

Preferably the camera is a line scan camera, the camera output includes information about the scanned line and the processor uses the information to determine the location of the object.

Preferably the method is:

Modulating the light from the light source to provide a frequency band within the imageable range of the camera; And

And excluding image data outside the frequency band.

Advantageously, processing the output includes excluding image data outside the frequency band and excluding the image data outside the frequency band includes filtering.

Preferably the filtering is;

Comb filter;

High pass filter

Notch filter

Applying a filter selected from the group consisting of band pass filters.

Preferably the method is

Controlling the light source; And

Including capturing and processing an image taken in a lighted state and in a non-lighted ambient light state,

The step for processing the output subtracts the ambient light from the split light state before detecting the level of light.

Preferably the light sources are LEDs and the touch display comprises means for controlling the operation of a section of the light source independent of the other sections of the light source.

Preferably the step of controlling the operation of the section of the light source comprises the step of independently controlling the effective intensity of the light source.

Preferably the step of controlling the section of the light source comprises wiring the light source with antiphase and driving it using a bridge drive.

Preferably the step of controlling the section of the light source comprises using a diagonal bridge drive.

Preferably the step of controlling the sections of the light source comprises using a shift register to cause each section to be controlled.

Preferably the step of capturing and processing an image comprises controlling sections of each of the camera and the light source and the step of processing the output comprises processing the information as to whether the section is lit or not. Steps.

Preferably, when the image is taken, some sections are illuminated and others are not.

Thus, a fourth aspect of the invention is a method for receiving user input in association with an image,

Providing a screen that a user can touch and view an image on or through the surface;

Providing a light source at one or more edges of the screen, the light source directing light across the surface of the screen;

Providing at least two cameras positioned around the screen and having an output, the camera being positioned so as not to receive direct light from the light source, each camera imaging a space in front of the screen, the output being Comprising the scanned image;

Processing the output to detect a level of reflected light; And

Processing the processed output of the camera, the step employing the processed output and triangulation to determine whether to indicate the presence of an object near the screen and if so to determine the location of the object It is a touch display.

Advantageously, said processed output indicates the relative orientation of the estimated object position relative to said camera.

Preferably said processed output indicates the relative orientation of the estimated object position with respect to the center of the lens of said camera.

Preferably the processor determines the position of the object as flat screen coordinates.

Preferably the method is:

Means for modulating the light from the light source to provide a frequency band within the imageable range of the camera; And

Means for excluding image data outside the frequency band.

Advantageously, said means for processing said output comprises said means for excluding image data outside said frequency band and said means for excluding image data outside said frequency band includes filtering.

Preferably the filtering is;

Comb filter;

High pass filter

Notch filter

And applying a filter selected from the group consisting of band pass filters.

Preferably the method is

Means for controlling the light source; And

Means for capturing and processing an image taken in a lighted state and in a non-lighted ambient light state,

The means for processing the output subtracts ambient light from the light splitting to detect the level of light.

Preferably the light sources are LEDs and the touch display comprises means for controlling the operation of a section of the light source independent of the other sections of the light source.

Preferably means for controlling the operation of the section of the light source comprises means for independently controlling the effective intensity of the light source.

Preferably said means for controlling the section of said light source comprises wiring said light source with antiphase and driving it using a bridge drive.

Preferably the means for controlling the section of the light source comprises using a diagonal bridge drive.

Preferably said means for controlling sections of said light source comprises using a shift register for causing each section to be controlled.

Preferably said means for capturing and processing an image comprises controlling each of said cameras and sections of said light source and means for processing said outputs to process information as to whether said section is illuminated or not. It includes.

Preferably, when the image is taken, some sections are illuminated and others are not.

Preferably the screen is reflective, the camera further images the screen and the means for processing the output detects the level of light from the mirror image.

Advantageously, said processed output indicates the distance of said object from said screen and the relative orientation of the estimated object relative to said camera.

Accordingly, a fifth aspect of the invention is a method for receiving user input in association with an image,

Providing at least one light source around or near the image, the light source directing light across the image;

Detecting the level of light at at least two locations around or near the image and providing the level as output; And

Processing the output using triangulation to determine if the output indicates the presence of an object near the image and, if so, to determine the location of the object.

Preferably the position is substantially non-opposite such that the output substantially indicates light reflected from the object when the object is present.

Accordingly, a sixth aspect of the invention is a user input device for positioning an object with respect to an image,

At least one light source around or near the image, the light source directing light across the image;

At least one detector positioned at or near the image for imaging the space in front of the screen and having an output indicating the level of light; And

A processor that receives the output and determines whether the output indicates the presence of an object near the image and, if so, uses triangulation to determine the location of the object.

1 is a schematic diagram showing the front of a preferred embodiment of a touch screen of the present invention.

1A is a cross-sectional view through X-X of FIG. 1.

1B is an illustration of front illumination of a preferred embodiment of the touch screen of the present invention.

2 illustrates a mirroring effect in a preferred embodiment of the touch screen of the present invention.

2A is a block diagram of a filter implementation of a preferred embodiment of the touch screen of the present invention.

FIG. 2B is a diagram illustrating the pixels seen by the area camera and sent to the processing module in a preferred embodiment of the present invention. FIG.

3 is a block diagram of a system of a preferred embodiment of the touch screen of the present invention.

4 is a side view for determining the position of an object using a mirrored signal in a preferred embodiment of the touch screen of the present invention.

4A is a top plan view illustrating the determination of the position of an object using a mirrored signal in a preferred embodiment of the touch screen of the present invention.

5 illustrates calibration in a preferred embodiment of the touch screen of the present invention.

6 is a graph representing the frequency domain output from an imager of a processing module in a preferred embodiment of the touch screen of the present invention.

6A is a graph representing the frequency domain in which a filter responds to a signal from an imager of a processing module in a preferred embodiment of the touch screen of the present invention.

6B is a graph representing the frequency domain in which an object separates from the background after two types of filtering in a preferred embodiment of the touch screen of the present invention.

7 illustrates a front view of another preferred embodiment of the touch screen of the present invention.

7A is a cross sectional view through X-X of another preferred embodiment of a touch screen of the present invention;

FIG. 7B illustrates a rear light of another preferred embodiment of the present invention. FIG.

FIG. 7C illustrates a rear illumination controlling the sensing height of another preferred embodiment of the present invention. FIG.

FIG. 7D is a diagram illustrating pixels shown by a line scan camera and sent to a processing module in another preferred embodiment of the invention. FIG.

8 is a graph representing simple separation of an object from a background in another preferred embodiment of the present invention.

9 illustrates various drive arrangements for the section backlight of the present invention;

9A illustrates a two section backlight driven by a two wire of the present invention.

9B illustrates a 12 section backlight driven by a four wire of the present invention.

9C illustrates a distributed shift register backlight of the present invention.

Preferred embodiments of the present invention are described below with reference to the drawings.

Best Mode for Carrying Out the Invention

The present invention relates to improvements in signal processing in the field of optical imaging touch screens. In a preferred embodiment, the optical touch screen uses front illumination and consists of a screen, a series of light sources, and at least two area scan cameras located on the same plane and around the screen. In another embodiment, the optical touch screen uses backlight illumination; The screen is surrounded by an array of light sources located behind the touch panel that are redirected across the surface of the touch panel. At least two line scan cameras are used in the same plane as the touch screen panel. The signal processing improvements created by these implementations allow objects to be detected when they are very close to the surface of the touch screen, are easy to calibrate, and can be detected by changing ambient light conditions such as moving lights or shadows. It is not affected.

A block diagram of a general touch screen system 1 is shown in FIG. 3. The information flows from the camera 6 to the video processing unit called the processing module 10 and the computer together. The processing module 10 performs many types of calculations, including filtering, data sampling, and triangulation, and controls the modulation of the illumination source 4.

Front illuminated touch screen

A preferred embodiment of the touch screen of the present invention is shown in FIG. The touch screen system 1 consists of a monitor 2, a touch screen panel 3, at least two light sources 4, a processing module (not shown) and at least two area scan cameras 6. The monitor 2 for displaying information to the user is positioned behind the touch screen panel 3. Underneath the touch screen panel 3 and the monitor 2 are an area scan camera 6 and a light source 4. The light source 4 is preferably a light emitting diode (LED), but may also be another type of light source, for example a fluorescent tube. Ideally, LEDs are used as can be modulated as needed and do not have inherent switching frequencies. The camera 6 and the LED 4 are in the same plane as the touch panel 3.

Referring to FIG. 1A, the viewing field 6a of the area scan camera 6 and the radiation path 4a of the LED 4 are in the same plane and parallel to the touch panel 3. The object 7 shown by the finger is illuminated when entering the radiation path 4a. Typically this is known as front panel lighting or object lighting. In Fig. 1B this principle is again illustrated. After the finger 7 has entered the radiation path 4a, the signal is reflected back to the camera 6. This indicates that the finger 7 is near or touching the touch panel 3. In order to determine whether the finger 7 is actually touching the touch panel 3, the position of the touch panel 3 must be established. This is done using other signals, mirrored signals.

Mirrored signal

The mirrored signal occurs when the object 7 approaches the touch panel 3. The touch panel 3 is preferably made of glass with reflective properties. As shown in FIG. 2, the finger 7 is positioned at a distance 8 above the touch panel 3 and mirrored to the touch panel 3 (7a). The camera 6 (only shown as a camera lens) images both the finger 7 and the reflected image 7a. The image of the finger 7 is reflected on the panel 3 7a; This can be seen through the field lines 6b and 6c and the virtual field lines 6d. This allows the camera 6 to image the reflected 7a image of the finger 7. The data generated from the camera 6 corresponds to the position of the field lines 6e and 6b when entering the camera 6. This data is then fed to the processing module 10 for analysis.

A section of the processing module 10 is shown in FIG. 2A. Within the processing module 10 is a series of scanning imagers 13 and digital filters 11 and comparators 12 implemented in software. There is a set number of pixels on the touch panel, for example, 30,000 pixels. These can be divided into 100 columns of 300 pixels. The number of pixels may be more or less than the number used, and that number is only used for example. In this situation, 30,000 digital filters 11 and comparators 12 are divided into 100 columns of 300 pixels, which form a matrix similar to the matrix of pixels on the monitor 2. A representation of this is shown in FIG. 2A where one column is being served by one image scanner 13 and three sets of digital filters 11 and comparators 12 14a, 14b and 14c. This allows information from three pixels to be read. A more detailed example of this matrix is shown in Figure 2b. Eight pixels 3a-3h are connected to the image scanner 13, in a group of columns, which are connected to the filter 11 and the comparator 12 (which are part of the processing module 10). Are connected sequentially. The number used in FIG. 2B is merely an example, and the exact number of pixels may be more or less. The pixels shown in this diagram do not have to form such a shape in the panel 3, which shape will be dictated by the position and type of the camera 6 used.

Referring again to FIG. 2, finger 7 and mirrored finger 7a activate at least two pixels; Two pixels are used for simplicity. This is represented by field lines 6e and 6b entering the processing module 10. This activates the software so that two signals pass through digital filter 11 and comparator 12 resulting in digital signal outputs 12a-12e. Comparator 12 compares the output from filter 11 to a predetermined threshold. If there is a finger 7 detected at that pixel, the output will be high, otherwise it will be low.

The mirrored signal also provides information regarding the position of the finger 7 with respect to the camera 6. It can determine the height 8 of the finger 7 above the panel 3 and its angular position. The information collected from the mirrored signal is sufficient to determine where the finger 7 is in relation to the panel 3 without the finger 7 having to touch the panel 3.

4 and 4A show the positional information that can be obtained from the processing of the mirrored signal. Location information is given in polar coordinates. The positional information is related to the height of the finger 7 and the position of the finger 7 on the panel 3.

Referring again to FIG. 2, the height with the finger 7 over the panel 3 can be seen as the distance between the outputs 12a-12e. In this example, finger 7 is height 8 above panel 3 and outputs 12b and 12e are generating a high signal. The other outputs 12a and 12d are generating a low signal. It can be seen that the distance 9 between the high outputs 12b and 12e is twice as large as the actual height 8 of the finger on the panel 3.

Modulation

The processing module 10 modulates and collimates the LED 4 and sets the sampling rate. The LED 4 is modulated and, in the simplest embodiment, the LED 4 is switched on and off at a predetermined frequency. Other types of modulation, eg sinusoidal modulation, are also possible. Modulating the LED 4 at high frequencies results in a frequency reading (when the finger 7 is detected) that is significantly greater than any other frequency produced by changing the light and shadow. The modulation frequency is greater than 500 Hz but not greater than 10 kHz.

sampling

The camera 6 continuously generates output and is periodically sampled by the processing module 10 due to data and time constraints. In a preferred embodiment, the sampling rate is at least twice the modulation frequency; This is used to avoid aliasing. The modulation and sampling frequency of the LED need not be synchronized.

Filtering

The output in the frequency domain from the scanning imager 13 is shown in FIG. 6. 6, two typical graphs are shown, one showing 21 when no object is being detected and one showing 20 when a finger is detected. In either graph, there is a shadow moving region 22 of approximately 5-20 Hz, and AC predominantly covers the frequency region 23 of approximately 50-60 Hz.

In the preferred embodiment, when no object is present in the field view, no signal is transmitted to the area camera so there are no other peaks in the output. When there is an object in the field of view, for example there is a signal 24 corresponding to the LED modulated frequency of 500 Hz. Lower unwanted frequencies 22 and 23 can be removed by various types of filters. Types of filters may include comb, high pass, notch, and band pass filters.

The output from the image scanner is shown in FIG. 6A, where a pair of different filter responses 26, 27 are being applied to the signal 20. In a simple implementation, a 500 Hz comb filter 26 may be implemented (if using a 500 Hz modulation frequency). This will only remove the lowest frequency. A more advanced implementation would include the use of a band pass 27 or notch filter. In this situation, all data is removed except for the region where the desired frequency is expected. In FIG. 6A this is shown as a 500 Hz narrowband filter 27 applied to the signal 20 at a modulation frequency of 500 Hz. These outputs 30, 31 from filters 26, 27 are further shown in FIG. 6B. The upper graph shows the output 30 when the comb filter 26 is used, while the lower graph shows the output 31 when the band filter 27 is used. Band filter 27 removes all unwanted signals while leaving the region of interest.

After the signal is filtered and the signal of the region of interest is identified, the resulting signal is passed to a comparator and converted into a digital signal and triangulation is performed to determine the actual position of the object. Triangulation is known in the art and disclosed in US5534917 and US4782328, which is incorporated herein by reference.

correction

The preferred embodiment of the touch screen of the present invention uses a very quick and easy calibration so that the touch screen can be used in any situation and moved to a new location, for example the touch screen is manufactured as a laptop. Calibration includes touching the panel 3 at three different positions 31a, 31b, 31c as shown in FIG. 5; This defines the touch plane of the touch panel 3. These three touch points 31a, 31b, 31c provide the processing module (not shown) sufficient information to calculate the position and size of the touch plane in relation to the touch panel 3. Each touch point 31a, 31b, 31c uses both a mirrored signal and a direct signal to generate the necessary data, as already described. These touch points 31a, 31b, 31c can be different around the panel 3 and need not be the actual position shown.

Swan touch screen

Figure 7 shows an alternative of the touch screen of the present invention. As in the preferred embodiment, the monitor 40 is behind the touch panel 41 and there is an array of lights 42 around the lower edge and side of the panel 41. These points face out towards the user and are redirected across the panel 41 by the diffusion plate 43. The array of lights 42 consists of many light emitting diodes (LEDs). Diffusion plate 43 is used to redirect and diffuse the light emitted from LED 42 across panel 41. At least two line-scan cameras 44 lie at the top two corners of the panel 3 and can image the object. The cameras 44 may be alternated at any position around the periphery of the panel 41. Around the periphery of the touch panel 41 is a bezel 45 or enclosure. The bezel 45 serves as a frame to stop light emission from being transmitted to the external environment. When there is no object near the touch panel 41, the bezel 45 reflects the light ray into the camera 44 so that the light signal is always read into the camera 44.

Alternatively, the array of lights 42 can be replaced with a cold cathode tube. When using a cold cathode tube, the diffusion plate 43 is not essential because the outer tube of the cathode tube diffuses the light. The cold cathode tube extends along the entire length of one side of the panel 41. This provides a substantially uniform light intensity across the surface of the panel 41. Preferably, the cold cathode tube is not used because it is difficult and expensive to deform to fit the specific length of each side of the panel 41. Using LEDs allows more flexibility in the size and shape of panel 41.

The diffusion plate 43 is used when the array of lights 42 consists of many LEDs. The plate 43 is used to diffuse the light emitted from the LED and redirect it across the surface of the panel 41. As shown in FIG. 7A, the light 47 from the LED 42 begins its path at a right angle to the panel 41. After hitting the diffusion plate 43, it is redirected parallel to the panel 41. Light 47 passes slightly over the surface of panel 41 to illuminate panel 41. The light 47 is collimated and modulated by a processing module (not shown), as described above.

Referring to FIG. 7A, increasing the width 46 of the bezel 45 may be increased or decreased. Increasing the width 46 of the bezel 45 increases the distance that an object can be detected. Likewise, the opposite applies to reducing the width 10 of the bezel 45.

The line scan camera 44 consists of a CCD element, a lens, and a driver control circuit. When the image is viewed by the camera 44 a corresponding output signal is generated.

7B and 7C, when the touch screen is not in use, ie when there is no user interaction or input, all light emitted from the array of lights 42 is transmitted to the line-scan camera 44. . When there is user input, that is, when the user selects something on the screen by touching the screen with his finger, the section of light being transmitted to the camera 44 is interrupted. Through calculations using the triangulation algorithm with the output data from the camera 44, the location of the activation can be determined.

The line scan camera 44 can read two light variables, namely direct light and reflected light transmitted from the LED 42. The method of detecting and reading direct and mirrored lights is the same as described above, but the line scan camera is simpler because it can only read one column from the panel at a time; It is not divided into the same matrix as when using area scan cameras. This is shown in FIG. 7D, where the panel 41 is divided into sections 14a-14d (what the line scan camera can see). The rest of the process has been described above. The pixels shown in this diagram do not have to form this shape in the panel 41, which shape will be dictated by the location and type of the camera 44 used.

In an alternative, because the bezel surrounds the touch panel, the line scan camera will continue to read the modulated light transmitted from the LEDs. This will result in a modulated frequency present at the output whenever there is no object interrupting the light path. When an object interrupts the light path, there will be no modulated frequency at the output. This indicates that the object is near or touching the touch panel. The frequency present in the output signal is twice as large as the frequency of the preferred embodiment (double amplitude). This is due to the two signals (direct and mirrored) being present at the same time.

In another alternative, shown in FIG. 8, the output from the camera is sampled when the LED is on and off modulating. This provides a reading 50 of the backlight plus ambient light and a reading 51 of the ambient light only. When the object interrupts the light from the LED, there is a dip 52 at the output 50. Since the ambient light changes a lot, it is difficult to see this small dip 52. For this reason, the ambient reading 51 is subtracted from the ambient and backlight reading 50. This results in output 54 where dip 52 is shown so that a simple threshold can be used to identify dip 52.

Calibration of this alternative is carried out in the same manner as described above, but the touch points 31a, 31b and 31c (of FIG. 5) cannot be on the same line and must be scattered around the surface of the panel 3.

In Fig. 7, the backlight is divided into many individual sections 42a to 42f. One section or subset of sections is active at any time. Each of these sections is imaged by a subset of the pixels of the image sensor 44. Compared to systems with single backlight control, backlight emitters operate at higher currents for shorter periods of time. Since the average power of the emitter is limited, the peak brightness is increased. Increased peak brightness improves ambient light performance.

It is advantageous that the backlight switching can be arranged so that the ambient light level of the other section is being measured by the signal processor while one section is illuminated. By measuring the ambient and backlit sections simultaneously, the speed is improved over a single backlight system.

The backlight brightness is adaptive by controlling the LED current or pulse duration when each section is activated to use the minimum average power while maintaining a constant signal-to-noise plus ambient ratio for the pixels viewing that section. Is adjusted.

Control of the plurality of sections with the minimum number of control lines is accomplished in one of several ways.

In the first implementation of a two section backlight, two groups of diodes 44a and 44b can be wired with anti-phase and driven with a bridge drive.

In a second implementation with more than two sections, a diagonal bridge drive is used. In FIG. 9B, four wires can select one of twelve sections, five wires can drive twenty sections, and six wires can drive thirty sections.

In the third implementation 9c, for many sections, the shift register 60 is physically distributed around the backlight and only two control lines are needed.

X-Y multiplexing arrangements are well known in the art. For example, an 8 + 4 wire is used to control a 4 digit display with 32 LEDs. 9B shows a four wire diagonal multiplexing arrangement with twelve LEDs. Control lines A, B, C, and D are driven by a tristate output, such as that commonly found on the pins of microprocessors such as the Microchip PIC family. Each tristate output has two electronic switches that are commonly MOSFETs. Either of the switches can be turned on or neither can be turned on. In order to operate the LED L1a, the switches A1 and B0 are only enabled. To operate L1B, A0 and B1 are operated. To operate L2a, A1 and D0 are enabled and so on. This arrangement can be used with any number of control lines, but is particularly advantageous for the 4, 5, 6 control lines where 12, 20, 30 LEDs can be controlled while the printed circuit board tracking is kept simple. If more control numbers are used, it may be beneficial to use a degenerate form where some of the possible LEDs are omitted to facilitate practical interconnection difficulties.

The diagonal multiplexing system has the following features:

It is advantageous if there are four or more control lines.

It requires a tri-state push-pull driver on each control line.

Rather than using an x-y arrangement of control lines in the crossing, the arrangement is represented by a ring of control lines with a pair of anti-phase LEDs arranged on each of the diagonals between the control lines. Each LED may be uniquely selected, and a particular combination may be selected.

-Use the minimum possible number of wires.

When EMC filtering is required on the wire, significant savings are made in components.

For those skilled in the art to which this invention pertains, many modifications and broadly other embodiments and applications will come to mind in the implementation of the invention without departing from the scope of the invention as defined in the appended claims. The disclosure and description herein are exemplary only and are not intended to be limiting in any sense.

Claims (91)

A screen configured to allow a user to touch and view an image on or through the screen; A plurality of light sources at one or more edges of the screen, the light sources emitting light across the surface of the screen; Means for modulating the light from the light source at a frequency within an imageable range of the camera; At least two cameras producing an output, each of said cameras being located around said screen, said light representing traveling light on a surface of said screen and a mirror image of space on a surface of said screen; The at least two cameras positioned to image the reflected light, the output including data representing the scanned image; Means for processing the output to detect a level of light; Means for excluding image data outside the frequency band used to modulate light from the light source; And A processor configured to receive a processed output of the camera, The processor employs the processed output and triangulation to determine if the processed output indicates the presence of an object near the screen and to determine the location of the object if the object exists, and the location of the object Is a distance of the object from the surface of the screen. The method of claim 1, And the position of the object comprises a relative orientation of the object relative to the at least one camera. The method of claim 2, And the relative orientation is measured with respect to the center of the lens of the camera. The method of claim 1, And the processor determines the location of the object as flat screen coordinates. The method of claim 1, The light source is located behind the screen and is arranged to project light through the screen, the light deflector is located in front of the screen and is arranged to direct light emitted from the light source across the surface of the screen. Touch display, characterized in that. The method of claim 1, The camera is a line scan camera, the camera output includes information about the scanned line and the processor uses the information about the scanned line in determining the position of the object. The method of claim 1, And means for excluding image data outside the frequency band comprises a filter. The method of claim 7, wherein the filter; Comb filter; High pass filter; Notch filters; And Touch display, characterized in that selected from the group consisting of a band pass filter. The method of claim 1, Means for controlling said light source to switch between a lighted state and a non-lighted ambient light state, The output of the camera is representative of at least one image obtained in the light-extracted state and at least one image obtained in the non-light-environmental light state, And said means for processing said output subtracts an ambient light condition from said light splitting condition before detecting a level of light. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete In the touch sensing method, Providing a screen on which a user can touch and view an image on or through the screen; Providing a plurality of light sources at one or more edges of the screen, the plurality of light sources operative to emit light across the surface of the screen; Modulating the light from the light source at a frequency within an imageable range of the camera; Providing at least two cameras yielding an output, each of the cameras being positioned around the screen, the light moving in space on the surface of the screen and a mirror image of the space on the surface of the screen; Providing the at least two cameras positioned to image light reflected from the screen representing the output, the output comprising data indicative of the scanned image; Processing the output to detect a level of light; Processing said output to exclude image data outside said frequency band used to modulate light from said light source; And Processing the processed output of the camera using triangulation to obtain the position of the object, wherein the position of the object comprises a distance of the object from the surface of the screen Way. 46. The method of claim 45, wherein the location of the object includes a relative orientation of the object relative to the at least one camera. 47. The method of claim 46, wherein the relative orientation is measured with respect to the center of the lens of the camera. 46. The method of claim 45, wherein the location of the object is determined in planar screen coordinates. 46. The system of claim 45, wherein the light source is located behind the screen and is arranged to project light through the screen, a light deflector is located in front of the screen, and the light emitted from the light source crosses the surface of the screen. And is arranged to direct light. 46. The touch sensing of claim 45, wherein the camera is a line scan camera, wherein each camera output includes information about the scanned line and the processor uses the information to determine the location of the object. Way. 46. The method of claim 45, wherein the means for excluding image data outside the frequency band comprises filtering. 52. The system of claim 51, wherein said filtering; Comb filter; High pass filter; Notch filters; And And applying a filter selected from the group consisting of band pass filters. The method of claim 45, Controlling the light source to switch between a lighted state and an unlighted ambient light state; And Capturing and processing at least one image of said light in said at least one image and at least one image of said light in a non-splitting ambient light state, Said step for processing said output subtracts said light from said ambient light state from said light beam before detecting said level of light. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete A touch sensing method for receiving user input in relation to an image, Directing light from the plurality of light sources across the surface of the screen where the user can touch and view the image on or through the screen; using at least two cameras positioned to not receive direct light from the light source in a mirror image comprising (i) light traveling through the surface of the screen and (ii) light reflected from the surface of the screen Imaging by; Processing the output of the camera to detect a level of light from the mirror image and a level of reflected light from an object in space on a surface of the screen; And And determining the position of the object from the processed output of the camera based on triangulation. 80. The apparatus of claim 79, wherein the location of the object includes an indication of the relative orientation of the object and the distance of the object from the screen with respect to the at least one camera, wherein the distance is determined based on light from the mirror image. Touch sensing method characterized in that the. 81. The method of claim 80, wherein the relative orientation is relative to the center of the lens of the camera. 80. The method of claim 79, wherein determining the position of the object includes determining that the object touched the screen when the object and the reflection of the object match. 80. The method of claim 79, wherein the location of the object comprises flat screen coordinates. 80. The apparatus of claim 79, wherein the camera comprises an area scan camera, wherein each camera output includes information about the scanned area and wherein the processor uses the information to determine the location of the object. Touch detection method. The method of claim 79, Modulating the light from the light source to provide a frequency band within the imageable range of the camera; And And removing the image data outside the frequency band. 86. The method of claim 85, wherein the step of excluding image data outside the frequency band comprises filtering. 87. The method of claim 86, wherein the filtering; Comb filter; High pass filter; Notch filters; And A touch sensing method comprising applying a filter selected from the group consisting of band pass filters. The method of claim 79, Controlling the light source to switch between a lighted state and an unlighted ambient light state; And Further comprising: capturing and processing at least one image in a lighted state and at least one image in a non-lighted ambient light state, Processing the output comprises subtracting light from an ambient light condition before detecting the level of light. The touch display of claim 1, wherein the processor is operative to determine a distance of the object from a surface of the screen based on a mirror image of the object. 90. The touch display of claim 89, wherein the processor is operative to determine that the object has touched the screen when the image of the object and the reflection image of the object match. delete

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