zForce – An Optical Touch Screen from Neonode

Optical touch screens like the ones using Neonode’s zForce technology offer a cheaper and more versatile alternative to more popular touchscreens like resistive and capacitive types. In addition to obvious applications in devices like cell phones and tablet pc’s, they also open the doors to the possibility of producing touch screen ebook readers.

I’ve always loved the technology behind what I call pure ebook readers, i.e., those devices that use e-ink displays. E-ink technology allows the text to be readable even under direct sunlight, has ultra-low power consumption, and is not as strenuous to the eyes – almost like a real book. However, the allure of having a touch screen display is also overwhelming.

Unfortunately, e-ink screens by themselves are not touch-sensitive. That is why some people are drawn to tablet pc’s that enhance the reading experience by adding touch features. But while these devices will allow you to use a stylus or your finger to “flip” pages and interact with the screen, they don’t offer the benefits of e-ink mentioned above.

That’s where optical touch screen technologies like zForce will come in handy. Let me introduce you to the basic concept first.

Neonode zForce touch screen LEDs and photoreceptors

Imagine a bezel surrounding the screen. This bezel contains pairs of LEDs and photoreceptors (represented by the red and yellow dots in the image above) aligned on opposite sides of the frame. Pulses of infrared light are emitted from the LED to the photoreceptors, effectively forming a matrix as shown.

Neonode zForce touch screen matrix

Thus, when you touch the screen with your finger, it gets in the way of one or more infrared beams. This allows the system to determine the X and Y coordinates where the obstruction took place. The same thing happens when you use either a stylus or another object like the side of a card.
At this point, the advantages of an optical touch screen like this are now pretty obvious. Let’s mention some of them:

Neonode zForce feature highlights

• It does not require a glass overlay. This translates to better light transmission and subsequently better display quality.
• It does not require any force. With a resistive display, you need to press the surface with some amount of force before any feedback is received.
• It supports interactions using a finger, a stylus, or even a gloved hand. Most capacitive touch screens cannot function when you use a stylus or a gloved hand.
• Since it leaves the e-ink display as is, all the benefits associated with an e-ink display is retained.

Other not-so-obvious benefits include the following:

• It is cheaper than capacitive touch screen solutions
• It supports multi-touch
• It consumes minimal power
• It is not sensitive to Radio Frequency Interference (RFI) or Electromagnetic Interference (EMI)
• It is able to provide high resolutions

One of the earliest takers of this kind of optical touch screen is Sony. Its latest touch screen ebook readers are using the zForce technology. I wonder what touch screen technology the BenQ nReader uses. Looks like I just found another topic to write about.