24-12-2012, 05:03 PM
MULTI TOUCH
[attachment=45167]
Introduction
Multi-touch is a human-computer interaction technique.
Consists of a touch screen as well as software that recognizes multiple simultaneous touch points.
Multi touch using Frustrated Total Internal Reflection
Enables high-resolution multi touch sensing on rear-projected interactive surfaces.
interact with more than one finger at a time and also able to accommodate multiple users simultaneously
Developments
In 2007 Apple unveiled the iPhone
In 2007 Microsoft introduced MS, a functional multitouch table-top computer based on a standard PC platform.
Technique
The technique used in multi touch is frustrated total internal reflection (FTIR).
It was introduced by Jefferson Y. Han who founded a company Perceptive Pixel.
Han envisions large collaborative spaces that will allow multiple users to work and interact.
Perceptive Pixel’s technology is currently being utilized, in the form of the Multi-Touch Collaboration Wall.
Frustrated Total Internal Reflection (FTIR)
Total internal reflection is an optical phenomenon that occurs when a ray of light strikes a medium boundary at an angle larger than the critical angle with respect to the normal to the surface.
If the refractive index is lower on the other side of the boundary no light can pass through, so effectively all of the light is reflected.
The critical angle is the angle of incidence above which total internal reflection occurs.
FTIR
if the angle of incidence is greater than the critical angle, then the light will stop crossing the boundary and be totally reflected back internally.
This occur when light travels from a medium with a higher refractive index to one with a lower refractive index.
Side effect of total internal reflection is the propagation of an evanescent wave across the boundary surface.
evanescent wave travel along the boundary between the two materials. This wave leads to a phenomenon known as frustrated total internal reflection.
Working
Multiple points are obtained on the camera
Each point is a pixel position
Each point locations are identified and all operations are performed
Advantages
Multi touch based on FTIR is a simple and inexpensive technique.
enables high-resolution graphics
It acquires true touch image information at high spatial and temporal resolutions.
It is scalable to large installations.
Larger shared-display systems
Disadvantages
being camera-based, it requires a significant amount of space behind the interaction surface
as an optical system, it remains susceptible to harsh lighting environments.
Conclusion
There are many ways to make a multi-touch screen. Some of the early designs measured the change in electrical resistance or capacitance on a surface when fingers touched it. But these devices have limited resolution, are relatively complex, and don't easily and inexpensively scale up to large dimensions. Multi-touch technologies have a long history. This technique using FTIR is simple and easy to implement. It provides any resolution displays supported with high graphics .The applications being both made and proposed are plenty in number.
[attachment=45167]
Introduction
Multi-touch is a human-computer interaction technique.
Consists of a touch screen as well as software that recognizes multiple simultaneous touch points.
Multi touch using Frustrated Total Internal Reflection
Enables high-resolution multi touch sensing on rear-projected interactive surfaces.
interact with more than one finger at a time and also able to accommodate multiple users simultaneously
Developments
In 2007 Apple unveiled the iPhone
In 2007 Microsoft introduced MS, a functional multitouch table-top computer based on a standard PC platform.
Technique
The technique used in multi touch is frustrated total internal reflection (FTIR).
It was introduced by Jefferson Y. Han who founded a company Perceptive Pixel.
Han envisions large collaborative spaces that will allow multiple users to work and interact.
Perceptive Pixel’s technology is currently being utilized, in the form of the Multi-Touch Collaboration Wall.
Frustrated Total Internal Reflection (FTIR)
Total internal reflection is an optical phenomenon that occurs when a ray of light strikes a medium boundary at an angle larger than the critical angle with respect to the normal to the surface.
If the refractive index is lower on the other side of the boundary no light can pass through, so effectively all of the light is reflected.
The critical angle is the angle of incidence above which total internal reflection occurs.
FTIR
if the angle of incidence is greater than the critical angle, then the light will stop crossing the boundary and be totally reflected back internally.
This occur when light travels from a medium with a higher refractive index to one with a lower refractive index.
Side effect of total internal reflection is the propagation of an evanescent wave across the boundary surface.
evanescent wave travel along the boundary between the two materials. This wave leads to a phenomenon known as frustrated total internal reflection.
Working
Multiple points are obtained on the camera
Each point is a pixel position
Each point locations are identified and all operations are performed
Advantages
Multi touch based on FTIR is a simple and inexpensive technique.
enables high-resolution graphics
It acquires true touch image information at high spatial and temporal resolutions.
It is scalable to large installations.
Larger shared-display systems
Disadvantages
being camera-based, it requires a significant amount of space behind the interaction surface
as an optical system, it remains susceptible to harsh lighting environments.
Conclusion
There are many ways to make a multi-touch screen. Some of the early designs measured the change in electrical resistance or capacitance on a surface when fingers touched it. But these devices have limited resolution, are relatively complex, and don't easily and inexpensively scale up to large dimensions. Multi-touch technologies have a long history. This technique using FTIR is simple and easy to implement. It provides any resolution displays supported with high graphics .The applications being both made and proposed are plenty in number.