07-11-2012, 04:20 PM
MULTI TOUCH
[attachment=38453]
ABSTRACT
Multi-touch technology is an advanced human-computer interaction technique that recogonises multiple touch points and also includes the hardware devices that implement it, which allow users to compute without conventional input devices . Multi-touch consists of a touch screen (screen, table, wall, etc.) or touchpad, as well as a software that recognizes multiple simultaneous touch points, as opposed to the standard touchscreen which recognizes only one touch point at a time. Multi touch using Frustrated Total Internal Reflection is a simple, inexpensive, and scalable technique for enabling high-resolution multi- touch sensing on rear-projected interactive surfaces. Different applications for multi-touch interfaces both exist and are being proposed. Some uses are individualistic eg iPhone, iPod touch, MacBook Pro, MacBook Air. The use of multi-touch technology is expected to rapidly become common place.
INTRODUCTION
TOUCH SCREEN
A touch screen is a display which can detect the presence and location of a touch within the display area. The term generally refers to touch or contact to the display of the device by a finger or hand. Touch screens can also sense other passive objects, such as a stylus. However, if the object sensed is active, as with a light pen, the term touch screen is generally not applicable. The thumb rule is: if you can interact with the display using your finger, it is likely a touch screen - even if you are using a stylus or some other object. Up until recently, most touch screens could only sense one point of contact at a time, and few have had the capability to sense how hard one is touching. This is starting to change with the emergence of multi-touch technology - a technology that was first seen in the early 1980s, but which is now appearing in commercially available systems. The touch screen has two main attributes. First, it enables you to interact with what is displayed directly on the screen, where it is displayed, rather than indirectly with a mouse or a touchpad. Secondly, it lets one do so without requiring any intermediate device, again, such as a stylus that needs to be held in the hand. Such displays can be attached to computers or, as terminals, to networks. They also play a prominent role in the design of digital appliances such as the personal digital assistant , satellite navigation devices and mobile phone
TECHNOLOGIES
There are a number of types of touch screen technology
Resistive
A resistive touch screen panel is composed of several layers. The most important are two thin metallic electrically conductive and resistive layers separated by thin space. When some object touches this kind of touch panel, the layers are connected at certain point; the panel then electrically acts similar to two voltage dividers with connected outputs. This causes a change in the electrical current which is registered as a touch event and sent to the controller for processing. Surface acoustic wave SAW technology uses ultrasonic waves that pass over the touchscreen panel. When the panel is touched, a portion of the wave is absorbed. This change in the ultrasonic waves registers the position of the touch event and sends this information to the controller for processing. Surface wave touch screen panels can be damaged by outside elements. Contaminants on the surface can also interfere with the functionality of the touch screen.
Capacitive
A capacitive touch screen panel is coated with a material, typically indium tin oxide that conducts a continuous electrical current across the sensor. The sensor therefore exhibits a precisely controlled field of stored electrons in both the horizontal and vertical axes - it achieves capacitance. The human body is also an electrical device which has stored electrons and therefore also exhibits capacitance. When the sensor's 'normal' capacitance field (its reference state) is altered by another capacitance field, i.e., someone's finger, electronic circuits located at each corner of the panel measure the resultant 'distortion' in the sine wave characteristics of the reference field and send the information about the event to the controller for mathematical processing. Capacitive sensors can either be touched with a bare finger or with a conductive device being held by a bare hand. Capacitive touchscreens are not affected by outside elements and have high clarity. The Apple iPhone is an example of a product that uses capacitance touchscreen technology.
Infrared
An IR touchscreen panel employs one of two very different methods. One method uses thermal induced changes of the surface resistance. This method is sometimes slow and requires warm hands. Another method is an array of vertical and horizontal IR sensors that detect the interruption of a modulated light beam near the surface of the screen.
Optical imaging
A relatively-modern development in touchscreen technology, two or more image sensors are placed around the edges (mostly the corners) of the screen. Infrared backlights are placed in the camera's field of view on the other sides of the screen. A touch shows up as a shadow and each pair of cameras can then be triangulated to locate the touch. This technology is growing in popularity, due to its scalability, versatility, and affordability, especially for larger units.
Dispersive signal technology
Introduced in 2002, this system uses sensors to detect the mechanical energy in the glass that occur due to a touch. Complex algorithms then interpret this information and provide the actual location of the touch. The technology claims to be unaffected by dust and other outside elements, including scratches. Since there is no need for additional elements on screen, it also claims to provide excellent optical clarity. Also, since mechanical vibrations are used to detect a touch event, any object can be used to generate these events, including fingers and stylus. A downside is that after the initial touch the system cannot detect a motionless finger. 1.1.2
DEVELOPMENT
Virtually all of the significant touchscreen technology patents were filed during the 1970s and 1980s and have expired. Touchscreen component manufacturing and product design are no longer encumbered by royalties or legalities with regard to patents and the manufacturing of touchscreen-enabled displays on all kinds of devices is widespread.
The development of multipoint touchscreens facilitated the tracking of more than one finger on the screen, thus operations that require more than one finger are possible. These devices also allow multiple users to interact with the touchscreen simultaneously. With the growing acceptance of many kinds of products with an integral touchscreen interface the marginal cost of touchscreen technology is routinely absorbed into the products that incorporate it and is effectively eliminated. As typically occurs with any technology, touchscreen hardware and software has sufficiently matured and been perfected over more than three decades to the point where its reliability is unassailable. As such, touchscreen displays are found today in airplanes, automobiles, gaming consoles, machine control systems, appliances and handheld display devices of every kind. The ability to accurately point on the screen itself is taking yet another step with the emerging graphics tablet/screen hybrids.
MULTI TOUCH
Multi-touch is a human-computer interaction technique and the hardware devices that implement it, which allow users to compute without conventional input devices e.g., mouse, keyboard. Multi-touch consists of a touch screen like screen, table, wall or touchpad, as well as software that recognizes multiple simultaneous touch points, as opposed to the standard touchscreen i.e. computer touchpad, ATM, which recognizes only one touch point. This effect is achieved through a variety of means, including but not limited to: heat, finger pressure, high capture rate cameras, infrared light, optic capture, tuned electromagnetic induction and shadow capture.
HISTORY
Multi-touch technology dates back to 1982, when the University of Toronto developed the first finger pressure multi-touch display. The same year, Bell Labs at Murray Hill published what is believed to be the first paper discussing touch-screen based interfaces.
Bell Labs
In 1984 Bell Labs engineered a multi-touch screen that could manipulate images with more than one hand. The group at the University of Toronto stopped working on hardware and moved on to software and interfaces, expecting that they would have access to the Bell Labs work.
A breakthrough occurred in 1991, when Pierre Wellner published a paper on his multi-touch Digital Desk, which supported multi-finger and pinching motions.
[attachment=38453]
ABSTRACT
Multi-touch technology is an advanced human-computer interaction technique that recogonises multiple touch points and also includes the hardware devices that implement it, which allow users to compute without conventional input devices . Multi-touch consists of a touch screen (screen, table, wall, etc.) or touchpad, as well as a software that recognizes multiple simultaneous touch points, as opposed to the standard touchscreen which recognizes only one touch point at a time. Multi touch using Frustrated Total Internal Reflection is a simple, inexpensive, and scalable technique for enabling high-resolution multi- touch sensing on rear-projected interactive surfaces. Different applications for multi-touch interfaces both exist and are being proposed. Some uses are individualistic eg iPhone, iPod touch, MacBook Pro, MacBook Air. The use of multi-touch technology is expected to rapidly become common place.
INTRODUCTION
TOUCH SCREEN
A touch screen is a display which can detect the presence and location of a touch within the display area. The term generally refers to touch or contact to the display of the device by a finger or hand. Touch screens can also sense other passive objects, such as a stylus. However, if the object sensed is active, as with a light pen, the term touch screen is generally not applicable. The thumb rule is: if you can interact with the display using your finger, it is likely a touch screen - even if you are using a stylus or some other object. Up until recently, most touch screens could only sense one point of contact at a time, and few have had the capability to sense how hard one is touching. This is starting to change with the emergence of multi-touch technology - a technology that was first seen in the early 1980s, but which is now appearing in commercially available systems. The touch screen has two main attributes. First, it enables you to interact with what is displayed directly on the screen, where it is displayed, rather than indirectly with a mouse or a touchpad. Secondly, it lets one do so without requiring any intermediate device, again, such as a stylus that needs to be held in the hand. Such displays can be attached to computers or, as terminals, to networks. They also play a prominent role in the design of digital appliances such as the personal digital assistant , satellite navigation devices and mobile phone
TECHNOLOGIES
There are a number of types of touch screen technology
Resistive
A resistive touch screen panel is composed of several layers. The most important are two thin metallic electrically conductive and resistive layers separated by thin space. When some object touches this kind of touch panel, the layers are connected at certain point; the panel then electrically acts similar to two voltage dividers with connected outputs. This causes a change in the electrical current which is registered as a touch event and sent to the controller for processing. Surface acoustic wave SAW technology uses ultrasonic waves that pass over the touchscreen panel. When the panel is touched, a portion of the wave is absorbed. This change in the ultrasonic waves registers the position of the touch event and sends this information to the controller for processing. Surface wave touch screen panels can be damaged by outside elements. Contaminants on the surface can also interfere with the functionality of the touch screen.
Capacitive
A capacitive touch screen panel is coated with a material, typically indium tin oxide that conducts a continuous electrical current across the sensor. The sensor therefore exhibits a precisely controlled field of stored electrons in both the horizontal and vertical axes - it achieves capacitance. The human body is also an electrical device which has stored electrons and therefore also exhibits capacitance. When the sensor's 'normal' capacitance field (its reference state) is altered by another capacitance field, i.e., someone's finger, electronic circuits located at each corner of the panel measure the resultant 'distortion' in the sine wave characteristics of the reference field and send the information about the event to the controller for mathematical processing. Capacitive sensors can either be touched with a bare finger or with a conductive device being held by a bare hand. Capacitive touchscreens are not affected by outside elements and have high clarity. The Apple iPhone is an example of a product that uses capacitance touchscreen technology.
Infrared
An IR touchscreen panel employs one of two very different methods. One method uses thermal induced changes of the surface resistance. This method is sometimes slow and requires warm hands. Another method is an array of vertical and horizontal IR sensors that detect the interruption of a modulated light beam near the surface of the screen.
Optical imaging
A relatively-modern development in touchscreen technology, two or more image sensors are placed around the edges (mostly the corners) of the screen. Infrared backlights are placed in the camera's field of view on the other sides of the screen. A touch shows up as a shadow and each pair of cameras can then be triangulated to locate the touch. This technology is growing in popularity, due to its scalability, versatility, and affordability, especially for larger units.
Dispersive signal technology
Introduced in 2002, this system uses sensors to detect the mechanical energy in the glass that occur due to a touch. Complex algorithms then interpret this information and provide the actual location of the touch. The technology claims to be unaffected by dust and other outside elements, including scratches. Since there is no need for additional elements on screen, it also claims to provide excellent optical clarity. Also, since mechanical vibrations are used to detect a touch event, any object can be used to generate these events, including fingers and stylus. A downside is that after the initial touch the system cannot detect a motionless finger. 1.1.2
DEVELOPMENT
Virtually all of the significant touchscreen technology patents were filed during the 1970s and 1980s and have expired. Touchscreen component manufacturing and product design are no longer encumbered by royalties or legalities with regard to patents and the manufacturing of touchscreen-enabled displays on all kinds of devices is widespread.
The development of multipoint touchscreens facilitated the tracking of more than one finger on the screen, thus operations that require more than one finger are possible. These devices also allow multiple users to interact with the touchscreen simultaneously. With the growing acceptance of many kinds of products with an integral touchscreen interface the marginal cost of touchscreen technology is routinely absorbed into the products that incorporate it and is effectively eliminated. As typically occurs with any technology, touchscreen hardware and software has sufficiently matured and been perfected over more than three decades to the point where its reliability is unassailable. As such, touchscreen displays are found today in airplanes, automobiles, gaming consoles, machine control systems, appliances and handheld display devices of every kind. The ability to accurately point on the screen itself is taking yet another step with the emerging graphics tablet/screen hybrids.
MULTI TOUCH
Multi-touch is a human-computer interaction technique and the hardware devices that implement it, which allow users to compute without conventional input devices e.g., mouse, keyboard. Multi-touch consists of a touch screen like screen, table, wall or touchpad, as well as software that recognizes multiple simultaneous touch points, as opposed to the standard touchscreen i.e. computer touchpad, ATM, which recognizes only one touch point. This effect is achieved through a variety of means, including but not limited to: heat, finger pressure, high capture rate cameras, infrared light, optic capture, tuned electromagnetic induction and shadow capture.
HISTORY
Multi-touch technology dates back to 1982, when the University of Toronto developed the first finger pressure multi-touch display. The same year, Bell Labs at Murray Hill published what is believed to be the first paper discussing touch-screen based interfaces.
Bell Labs
In 1984 Bell Labs engineered a multi-touch screen that could manipulate images with more than one hand. The group at the University of Toronto stopped working on hardware and moved on to software and interfaces, expecting that they would have access to the Bell Labs work.
A breakthrough occurred in 1991, when Pierre Wellner published a paper on his multi-touch Digital Desk, which supported multi-finger and pinching motions.