screen. Each strip can be considered a type of digital “channel” in this configuration, where contact within one digital channel is always evaluated on an analog basis. While the reso- lution of this type also depends to some extent on the strip spacing (which is typically wider), the resolution is generally higher than in the first type, sometimes as fine as 0.2 mm. Since a rule of thumb for touch screens is that 1-mm resolution is adequate for most applications, this type is optimum for applications requiring better-than-average resolution. Examples of this type of AMR were shown by EETI (eGalax) and Dawar, among others (see Fig. 3).
The nine exhibitors showing AMR included AMT, Dawar, EETI, Fujitsu, Panjit, Stantum/ Sitronix, Techno Print/Nagase America, Touch International, and Wintek.
Fig. 1: This schematic illustration of a film-based projected-capacitive touch screen is typical of one of the two primary forms coming into common use in the touch industry (the other form is glass-based). Source: Sony Chemical.
Display, Maxim, Microchip, N-trig, Nissha, Ocular, Panjit, RiTdisplay (US Micro Products), Samsung, Sony Chemical, Touch International, Touch Revolution, Wacom, Wintek, and Zytronic.
Analog Multi-Touch Resistive (AMR) Analog multi-touch resistive touch technol- ogy, formerly called “digital resistive,” con- tinued its upward trajectory at Display Week 2010. With only one exhibitor in 2008 and three exhibitors in 2009, the total of nine exhibitors this year shows that the technology is beginning to emerge as a serious alternative to projected capacitive. A few suppliers are trying to build their own brand names for the technology (e.g., RMTS by Panjit and MARS by Touch International), but generally the industry seems to be settling on AMR as the name and acronym of choice.
half of the strip spacing – which is usually quite narrow. For example, if the spacing is 1.3 mm (as in Stantum’s very nice demo touch screen shown in Fig. 2), then the resolu- tion is 0.65 mm. This type of AMR could actually be called “DMR” or “digital multi- touch resistive.”
In the other type of AMR, the intersection of each set of conductive strips is treated as a miniature four-wire analog-resistive touch
In-Cell Touch Technology One of the most surprising aspects of Display Week 2010 was the almost total lack of in-cell touch technologies on display. On-cell touch, where the touch screen is fabricated on top of the color-filter glass, has taken the industry by storm. Exhibitors showing on-cell touch included Samsung (resistive and capacitive), LG Display (capacitive), NEC (surface capacitive), Toshiba (resistive), and Wintek (resistive).
One particularly interesting on-cell demon- stration was by NEC, which was showing a very novel version of on-cell surface capaci- tive (not projected capacitive). The demon- stration LCD, as described in NEC’s Sympo- sium paper, “Touch-Panel-Embedded IPS-
There are actually two different types of AMR, and it is clear from the exhibits at Display Week 2010 that the difference is not yet clearly communicated or even understood. Since neither type has a distinct name yet, perhaps that is not surprising. In the first type, the intersection of each set of conductive (ITO) strips is treated as a switch – it is either making contact or it is not. It is digital. The resolution of this type is therefore typically
Fig. 2: Above is Stantum’s very-high-resolution (0.65 mm) analog multi-touch resistive (AMR) touch screen, showing extremely fine digital ink. The touch screen uses four Sitronix controller chips around the edge (under the bezel). The left side of the photo is a standard video card used to drive the display electronics on the right.
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