Resistive and Capacitive touch screens have been around for a while. But there are other newer touch screen technologies around including infrared. These all have different advantages and disadvantages and as a result are individually suited to differing applications and types of users. Capacitive touch screen technology is the technology that the Apple iPhone, iPad and Nook Color use and resistive technology is what is found on most stylus-based PDAs. Dedicated ebook readers with touch screens all use infrared touch screen technology. Examples include the Sony PRS ereaders, Barnes and Noble Simple Touch eReader, and Kobe Reader Touch edition. Sony was the first to use infrared screen technology with the PRS 350, PRS 650 and PRS 950 ebook readers September 2010. About 9 months later both Barnes and Noble and Kobo have followed suite and are using exactly the same component on their latest e-readers: Neonode’s zForce infrared technology. The market itself is telling us that infrared touch technology is the best for e-readers. But is that because it enhances the reading experience or is it because of secondary factors such as lower cost. Read on to find out the answer.
Limitations of Resistive and Capacitive Touch Screen Technology
Resistive technology is pressure sensitive technology. Resistive touch screens deform slightly upon finger and stylus pressure causing two resistive sheets to touch. The position of this point is calculated from by making several measurements of resistance from the edge of one sheet to the edge of the other sheets. Best used for detailed work and for selection of a particular spot on a screen, resistive technology is not useful for sweeping gestures or motion, such as zooming in and out.
Capacitive touch screens comprise of two layers of conductive strips arranged perpendicularly so that there is a grid of intersections. At each intersection there is no actual contact between the strips and so a small capacitance is created. Moving a stylus or finger close to the intersection alters the capacitance. Thus position can be measured by monitoring the capacitance change and each intersection point. Both resistive and capacitive touch screen technologies are quite mature and with further innovations, there relative advantages and disadvantages have been narrowing.
However, resistive and capacitive touch screens have the disadvantage of requiring an additional layers above the display, which then introduces the following disadvantages:
- Reflection and parallax effects.
- Added weight and thickness of the additional layers.
- Additional cost due to use of expensive components particularly in the case of capacitive touch screens.
- Accuracy is relatively better for resistive touch screen compared with capacitive touch screen, but is limited by parallax error.
- Does on recognize two finger gestures (resistive touch screen) or recognize gloved hands (capacitive touchscreen).
Infrared Touch Screen Technology Ideal For eBook Readers
Infrared Touch screen technology incorporates some of the best functionalities of both the capacitive and resistive touch screen technologies and does not require an additional layers on the display. Infrared touch technology relies on the interruption of an IR light grid in front of the display screen. A row of IR-light emitting diodes (LEDs) and photo transistors, each mounted on two opposite sides to create a grid of invisible infrared light beams. As a result infrared touch screens have the following advantages, nicely summarized by Neonode:
- No additional layers are added to the screen that may dilute the screen contrast and clarity. Thus provides a 100% clear viewing experience, free from reflection and parallax effects.
- Minimal device weight impact.
- Low display building height enabling design flexibility.
- Enable touch detection for any type of objects (finger, pen, glove).
- Supports high resolution pen writing in combination with finger navigation including gestures multi-touch, sweeps and much more.
- Low cost as it does not require Layering technology as with the capacitive and resistive touch screen options;
- More responsive than the capacitive screen technology and, as a result, is quicker and less prone to misreads. It allows movement and sweeping motions as compared to point-sensitive, stylus-based resistive screens;
- Zero force is necessary, obviates the need to use any force to select or move items on the screen as would be the case with a stylus;
- Cost-efficient due to the lower cost of materials and extremely simple manufacturing process when compared to the expensive layered capacitive and resistive screens;.
As well as ebook readers, Infrared touch screen technology is also used in Mobile phones, Tablets and other touch enabled devices. Infrared touch technology can be applied on any flat surface like a Liquid Crystal Display (LCD), Organic Light Emitting Diode Displays (OLED), Electronic Paper Displays (EPD) such a E-Ink, and Mouse Pad.
zForce A Leading Infrared Touch Screen Technology
In all current touch screen ebook readers the infrared touch screen technology used is called zForce, provided by Neonode. Neonode, a Swedish company traded on the the NASDAQ (NEON), was founded in 2001. Since the start its core technology has been zForce. Shortly after applying this technology to its own line of mobile phones, the company filed for bankruptcy in 2008. After restructuring the company focused solely on licensing out its zForce infrared-based touch-screen technology, and met with some success. zForce offers market leading performance in a number of critical areas, particularly for power consumption.
zForce uses a small frame around the display with light emitting diodes and photoreceptors on the opposites sides hidden behind a infrared-transparent black bezel. Have a close at a Sony Reader, Nook Simple Touch Reader of the Kobo Touch Reader. The screen surface is a slightly lowered to allow space for the Infrared touch frame. A controller sequentially pulses the LEDs to create a grid of infrared light beams across the display. A touch or just close proximity to the screen obstructs one or more of the beams which identifies the X and Y coordinates which also give area information. Signal processing give multiple touch readings and high speed gesture feedback.
Taking Care of Touch Screen E-readers
Whichever touch screen e-reader you choose, note that the screen is a very fragile part of the device. In the case resistive touch screen e-readers, the flexible top layer is prone to scratches, which can reduce the reading pleasure. And in the case of capacitive and infrared touch screen e-readers, the top glass layer is susceptible to shattering by sharp knocks. Therefore it is essential to protect your touch screen with a protective cover or case.
Note also that that some covers and cases include a flexible screen protector. Although a screen protector will work with resistive touch screen ereaders, albeit with some loss of touch sensitivity, the screen protector will almost certainly not work with capacitive screen protectors. For the iPad and NOOKcolor which use capacitive touch screen technology, an iPad cover or NOOKcolor protector is the best way to protect the screen.
Screen protectors can also work very effectively with infrared touch screen as the grid of infrared beams is above the screen and will be above a suitably designed screen protector with a low reflectivity coating.