Apple granted another key multitouch patent

Apple won a core multitouch patent regarding oscillating signals that was alluded to when Steve Jobs first announced the original iPhone in 2007, and adds to the company's already formidable legal arsenal.

The United States Patent and Trademark Office published on Tuesday that the Cupertino, Calif. company now owns a crucial patent that describes how touch events are recognized by a touchscreen device, and was one of the "200+ Patents for new inventions" Jobs lauded when the iPhone first debuted, reports Apple patent blog Patently Apple.

The newly granted patent focuses on the oscillator signal and circuit of a touchscreen-equipped device, an integral invention directly related to how users interact with their multitouch products.

Apple states in the filing:

"In general, multi-touch panels may be able to detect multiple touches (touch events or contact points) that occur at or about the same time, and identify and track their locations."

Previous to the iPhone's introduction in 2007, most touch-capable devices relied on single-touch input like resistive touchscreens. The legacy technology "senses" a touch when two electrically resistive sheets separated by a small gap are connected by the push of a finger or stylus, which in turn creates a voltage division that is detected by a device controller that records the change along the x and y axes.

Resistive displays are limited in that they can only recognize single inputs no matter how many objects are touching the screen.

One way to record multiple touches at a time is to generate an oscillating signal circuit that can power and clock inputs over a substrate as in a capacitive touchscreen display, however it is difficult to create a precise circuit-based oscillator.

Apple's patent provides a solution to capacitive touchscreen problem by using calibration logic circuitry which compares the signal oscillation against a reference signal and tunes the clock frequency accordingly. The invention provides for an accurate capacitive display that can not only sense multiple touches, but also detect hover or near touches which are also recognized as "touch events."

Flowchart illustrating calibration logic tuning an oscillator | Source: Patently Apple

The patent wording states that the invention could apply to computing devices such as desktops, laptops, tablets or handhelds, including digital music and video players and mobile telephones. Also mentioned are public computing systems like kiosks and ATMs.

The news follows a Dec. 19 U.S. International Trade Commission decision which resulted in an import ban on HTC Android handsets that infringe on Apple's Data Detectors patent. The injunction will take take effect on April 19, 2012, however HTC CEO Peter Chou said the Taiwanese company is already testing workarounds to bypass the ITC ruling.