Single 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:
Single touch
Single Touch occurs when a finger or stylus creates a touch event on the surface of a touch sensor or within a touch field so it is detected by the touch controller and the application can determine the X,Y coordinates of the touch event. These technologies have been integrated into millions of devices and typically do not have the ability to detect or resolve more than a single touch point at a time as part of their standard configuration.
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 | Resistive | Surface capacitive | Projected capacitive | Bending Wave | Surface Acoustic Wave |
| Technology | Analog resistive | Electrostatic field | Electrostatic field | Bending wave radiation | Sound waves |
| Activation | Low activation pressure required | Low activation pressure required | Low activation pressure required | Low activation pressure required | Low activation pressure required |
| Transmissivity/optics | up to 82%, small distortion of graphics due to coatings | up to 85%, slight yellow cast due to coatings | up to 85%, slight yellow cast due to coatings | Very good >92% | Very good >92% |
| Drag and drop | Requires constant pressure, however draws smooth lines | Requires constant pressure, however draws smooth lines | Requires constant pressure, however draws smooth lines | Requires constant pressure, however draws smooth lines | Requires constant pressure, however draws smooth lines |
| Calibration | Requires periodic re-calibration due to wearing of the coatings | Requires periodic re-calibration | Requires periodic re-calibration | No drift | Requires periodic re-calibration |
| Surface contaminants/durability | Unaffected by surface contaminants. Polyester top sheet is easily scratched or burned. | Unaffected by water and most surface contaminants. | Unaffected by water and most surface contaminants. | Unaffected by water and most surface contaminants. | Adversely affected by surface contaminants and water. |
| Sensor substrate | Polyester top sheet, glass substrate with ITO coating | Glass with ITO coating | Glass with ITO coating | Glass with ITO coating | Glass with ITO coating |
| Single/dual/multi-touch | Single † | Single | Single** | Single | Single |
| Touch points | 1 point † | 1 point | 1 point | 1 point | 1 point |
| Display size | up to 19" | 8.4"-114" | 8.4"-114" | 8.4"-42" | 10.4"-30" |
| Size constraints | Originally designed for smaller sizes and may not scale easily; largest sensor is 19" | Originally designed for smaller sizes and may not scale easily; largest sensor is 19" | Originally designed for smaller sizes and may not scale easily; largest sensor is 19" | Scales to larger sizes | Originally designed for smaller sizes and may not scale easily; largest sensor is 30" |
| Sealable | Yes, to NEMA 4 and 12 and IP 65 standards | Yes, to NEMA 4 and 12 and IP 65 standards | Yes, to NEMA 4 and 12 | Yes, to NEMA 4 and 12 and IP 65 standards | Not completely: Yes, to meet NEMA 3/3R/5/12/12K/13, IP64 standards |
| Integration | Foil or overlay frame | Foil, overlay frame or component | Foil, overlay frame or component | Component | Component only |
| Touch method | Can use any pointing device | Human touch | Human touch (hand, gloved hand or conductive stylus). | Can use any touching device | Finger only |
| Touch accuracy | Good | Good | Best | Good | Good |
| Drivers | Proprietary drivers, may not be compatible with all software | Proprietary drivers, may not be compatible with all software | Proprietary drivers, may not be compatible with all software | Proprietary drivers, may not be compatible with all software | Proprietary drivers, may not be compatible with all software |
| Main limitation of technology | Polyester top sheet affects optics and is subject to damage. | Requires human touch, scratches in coatings cause dead spots. Field replacement difficult due to calibration coefficients. Sensitive for electromagnetic interference. | Requires human touch, scratches in coatings cause dead spots. Field replacement difficult due to calibration coefficients. | - | Surface contaminants cause dead spots and requires periodic cleaning of sensor, small spacing between touch window and display monitor is required. |
| * Optical technology with 2+ cameras may be capable of dual touch and multi-touch with gesture upgrades. | |||||
| ** Capable of 3 or more resolvable points, varies by vendor | |||||
| † Matrix resistive technology may be capable of dual touch and multi-touch, but they are not widely used. | |||||
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