RIM patent application details hybrid touchscreen

BlackBerry maker Research In Motion has applied for a patent on a hybrid resistive-capacitive touchscreen.

The company's patent application, published at the end of July, describes a fusion between the two main types of touchscreen currently on the market.

Resistive touchscreens have been used in many smartphones for most of this decade. They use two separated touch-sensor layers that, when pressed by a finger or stylus, connect to tell a controller where the pressure took place.

Capacitive touchscreens, which only came into widespread use in the handset market with Apple's iPhone, detect the location of input by registering a charge between the screen — coated in a conductive material, such as indium tin oxide — and the user's finger.

Capacitive touchscreens are more sensitive and have the advantage of being able to register input just before the finger actually touches the screen, making it possible to process instructions more quickly. By contrast, resistive touchscreens are cheaper to manufacture and also allow the use of a stylus.

In the screen described in RIM's application, the outer of the two layers has a conductive coating, allowing both types of interaction through a single controller-integrated circuit. According to the company's filing, "the capacitive and resistive functions of the touchscreen do not interfere with each other".

"Advantageously, a touch of the touchscreen display can be detected prior to contact with the touchscreen display," the application reads. "Thus, a signal can be sent to the processor for providing a timely response when the touchscreen is touched. For example, a tactile feedback can be provided more quickly, providing a better user feel."

The application also notes that the capacitive functionality of the screen could make it possible for the display to turn itself off when the user puts the device near their face during a call.

RIM only began selling its first touchscreen handset, the BlackBerry Storm, in November last year. That device had a different type of capacitive touchscreen to the one used by other phone makers, opting for a slightly curved screen that could physically be clicked up and down.

Pete Cunningham, a senior analyst with Canalys, told ZDNet UK on Friday that the Storm's screen had given RIM a track record in innovative displays, and the screen described in the patent could successfully combine the benefits of both capacitive and resistive screens.

"Usability, from a finger point of view, is probably better on a capacitive screen," Cunningham said. "However, resistive screens allow the use of handwriting with the stylus… [and] have the benefit of being more durable in terms of the temperature spectrum they can work in."

Cunningham added that on-screen handwriting is particularly important in Asian markets.