Infrared
Infrared (IR) optical-touch systems use an array of infrared light-emitting diodes on two adjacent bezel edges of a display, with photo sensors placed on the two opposite bezel edges to analyze the system and determine a touch event. The infrared bezel is mounted to the front of the display screen where the LED and photo sensor pairs create a grid of light beams across the display. An object (such as a finger or pen) that touches the screen interrupts the light beams, causing a measured decrease in light at the corresponding photo sensors. The measured photo sensor outputs can be used to locate a touch-point coordinate.
A feature of infrared touch which has been long desired is the digital nature of the sensor output when compared to many other touch systems that rely on analog-signal processing to determine a touch position. These competing analog systems normally require continual re-calibration, have complex signal-processing demands (which adds cost and power consumption), demonstrate reduced accuracy and precision compared to a digital system, and have longer-term system-failure modes due to the operating environment. IR, has become one of the more versatile and flexible touch technologies given its scale, high performance and resolution, durability, ease of use, and cost-effectiveness for all devices 15 inches and larger.
Limitations and considerations
- The major issue with infrared is that the seating of the touch frame is slightly above the screen. Consequently, it is susceptible to early activation before the finger or stylus has actually touched the surface.
- Contaminants can also cause false activation on the screen inside the thick border that is required for the frame.
- Costs to manufacture infrared bezels is significant.
Advantages
- Digital sensor output, less re-calibration is needed which results in higher accuracy, precision and system durability.
- Life span: Not wear sensitive, as there are no layers, coatings or moving parts used.
- Doesn’t require a glass or plastic overlay, 100% light transmission.
- Especially suitable for large-size (over 40 inch) touch screens.
- Can be operated with finger, stylus, etc.
- Protected glass is optional.
Disadvantages
- The relatively high cost of the technology compared to competing touch technologies.
- Issue of performance in bright ambient light (e.g. sunlight).
- Pollution in the active areas inside corners of the bezel may influence system function. Cleaning from time to time resolves this issue.
Touch functionality
- Single touch
- Dual touch
- Multi-touch
- Multi-user touch
Product types
- Overlay frame/bezel
- Display solution
Applied in:
PTMMUT-46 Multi-user touch monitor
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