Multi-touch techniques compared
Despite increased consumer awareness of the "touch interface" courtesy of an expanding selection of touch-enabled consumer devices, the intricacies and varieties of touch technologies is a topic not fully understood by the gesture touch community. Courtesy of the product positioning of dozens of touch technology manufacturers, the filtering of bloggers and the responses posted by the larger touch community, mixed messages exist about how certain technologies work and what the true touch capabilities are for each technology. To help create a basis for technology comparisons, below is a discussion of the various applicable touch input terms and the touch technologies that reliably recognize these input categories:
Dual touch
Dual touch or two touch refers to a touch system that can detect and resolve two discrete, simultaneous touch events. The best demonstration of dual touch capability is to draw two parallel lines on the screen at the same time. Dual touch systems can also support gesturing.
Multi-touch
Multi-touch refers to a touch system's ability to simultaneously detect and resolve a minimum of 3+ touch points. All 3 or more touches are detected and fully resolved resulting in a dramatically improved touch experience. Multi-touch is considered by many to become a widely-used interface mainly because of the speed, efficiency and intuitiveness of the technology.
Touch technique capabilities comparison
| Touch Technology | Infrared | Optical Imaging | Planar Scatter Detection | Diffused Illumination | Diffused Surface Illumination | Frustrated Total Internal Reflection |
| Technology | Light interruption | Optical imaging | Waveguide analysis | Image analysis | Image analysis | Image analysis |
| Activation | Zero activation force required | Zero activation force required | Zero activation force required | LCD based: very good>92% | Zero activation force required | Zero activation force required |
| Transmissivity/optics | Very good >92% | Very good >92% | Very good >92% | Two options Projection: Diffuser needed: up to 85% LCD based: very good>92% | Two options Projection: Diffuser needed: up to 85% LCD based: very good>92% | Two options Projection: Diffuser needed: up to 85% LCD based: very good>92% |
| Drag and drop | Low resolution due to spacing of IR sensors and interpolation between XY grid | High resolution, draws smooth lines | High resolution, good drag and draws smooth lines | High resolution, good drag and draws smooth lines | High resolution, good drag and draws smooth lines | High resolution, good drag and draws smooth lines |
| Calibration | No drift | No drift | No drift | Requires periodic re-calibration | Requires periodic re-calibration | Requires periodic re-calibration |
| Surface Contaminants/Durability | Potential for false activation and dead zones from surface contaminants | Potential for false activation and dead zones from surface contaminants | Potential for false activation and dead zones from surface contaminants | Potential for false activation and dead zones from surface contaminants | Potential for false activation and dead zones from surface contaminants | Potential for false activation and dead zones from surface contaminants |
| Sensor Substrate | Any substrate | Any substrate | Glass | Acrylic or glass | Acrylic or glass | Acrylic or glass |
| Single/dual/multitouch | Dual/Multitouch | Dual * | Multitouch | Multitouch | Multitouch | Multitouch |
| Touch points | Up to 32 points | 2 points | Up to +20 points | Unlimited, but computer performance dependant | Unlimited, but computer performance dependant | Unlimited, but computer performance dependant |
| Display Size | 10.4"-60" | 12"-120" | 22"-70" | Depedant to technique used (projector of LCD) | Depedant to technique used (projector of LCD) | Depedant to technique used (projector of LCD) |
| Size constraints | Scales to larger sizes | Scales to larger sizes | Scales to larger sizes | Scales to larger sizes | Scales to larger sizes | Scales to larger sizes |
| Sealable | Yes, to NEMA 4. | Yes, to NEMA 4. | Yes, to NEMA 4 and 12 and IP 65 standards | Yes | Yes | Yes |
| Integration | Frame overlay | Overlay frame or display solution | Display solution only | Total setup only | Total setup only | Total setup only |
| Touch method | Can use any touching device | Can use any pointing device | Can use any pointing device | Can use any pointing device | Can use any pointing device | Can use any pointing device |
| Touch accuracy | Best | Best | Best | Good | Good | Good |
| Drivers | HID compliant no additional drivers required | HID compliant no additional drivers required | HID compliant no additional drivers required | HID compliant no additional drivers required | Proprietary drivers, may not be compatible with all software | Proprietary drivers, may not be compatible with all software |
| Main limitation of technology | Surface contaminants can cause false activation. Bezel overlay is placed in front of the display area (no flat surface). | Surface contaminants can cause false activation. Bezel overlay is placed in front of the display area (no flat surface). | Surface contaminants can cause false activation. Bezel overlay is placed in front of the display area (no flat surface). | Special surface coating required, sensitive to ambient lighting conditions | Special surface coating required, sensitive to ambient lighting conditions | Special surface coating required, sensitive to ambient lighting conditions |
| * Optical technology with 2+ cameras may be capable of dual touch and multi-touch with gesture upgrades. | ||||||
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