Touch Panel Displays Gain Reliability
Touch panel displays have skyrocketed in popularity following introduction of Apple's iPhone and the Nintendo DS gaming system. At the FPD International 2008 show, F-Origin, Wacom and LG Electronics showed products with increased sensitivity and reliability.
Kenji Tsuda, Asia Contributing Editor -- Semiconductor International, 11/11/2008 9:21:00 AM
Touch panel displays with improved reliability and endurance emerged at the FPD International 2008 show, held recently in Yokohama, Japan. Touch panel displays have become a critical technology, especially since the popularity of Apple’s iPhone and the Nintendo DS gaming system, and Microsoft’s planned support for touch panel displays in the Windows 7 operating system. F-Origin Inc. (Morrisville, N.C.), Wacom Corp. (Yokohama, Japan) and LG Electronics Inc. (Seoul, South Korea) showed displays at the show that promise to advance the use of touch panels.
Yuji Mitani, president and CEO of Touch Panel Laboratories (Tokyo), estimates that conventional touch panels, using a resistance detection method, dominate the market with a 72% market share. However, they have not been particularly reliable: an estimated 30% of touch-enabled products in the market suffer from failures, most commonly abrasion of the touch contact in the panels. Endurance also is a major problem, he said, explaining that conventional resistive-type touch panels detect cross points in the X and Y directions. Those contact points tend to wear, reducing reliability.
F-Origin showed an 8 in. panel aimed at PDAs and car navigation systems, and a 15 in. panel for point-of-sale terminals. The panels use three pressure sensors, placed at three corners of the panel. When a point is pressed, the three sensors detect the forces and the touch tilt angles in the three directions. An off-the-shelf microprocessor calculates the position of the point, based on a sampling rate of 1000 point samples per second. The embedded calculation software uses a proprietary algorithm that reduces the memory footprint, said Joe Carsanaro, president and CEO of F-Origin. The F-Origin method does not require extra glass for the X- and Y-matrix electrodes, which helps maintain the brightness, keeps power consumption equivalent to conventional panels, and improves the endurance, he said.
Wacom showed a pen for touch panel input that features an ability to measure the pen’s tilt for hand-written letters and characters. Writing a signature, or creating the Japanese kanji characters, requires an ability to detect soft or hard pressure, emulating an ink pen. A human writes a wide letter with a firm touch, and a thin letter by a weak touch, for example.
Wacom integrates an LC (inductor-capacitor) resonator in the pen. As the pen writes letters and senses the pressure, the capacitance and resonant frequency changes. Multiple inductors are placed on the surface of the panel to detect the pen position. An AC current turns on the panel inductors for a short period, and the magnetic field is detected by the pen’s LC resonator. When the AC current turns off the panel inductor, the pen’s inductor current flows and generates a magnetic field. A specific inductor on the panel detects the magnetic field, which informs the system of the pen position. If a user tilts the pen, the first magnetic field is changed according to the tilt. A processor calculates the soft or hard feeling of the letters based on the tilt angles.
LG Electronics exhibited a 52 in. touch panel with 60 built-in LEDs and three CMOS line sensors. The screen is enlarged or shrunk by hand gestures for zooming in and zooming out. The position resolution is less than a single pixel, a company official said at the show, adding that the touch panel depends on an improved algorithm that calculates position.
