The details were revealed in a patent application published this week and discovered by AppleInsider. The new filing, entitled "Dual-Sided Track Pad," notes that the concept could be applied to a touch-only Magic Trackpad style device, or to a touchscreen device like an iPhone.
The dual touch panel concept could also allow for two different types of panels to be presented to users. For example, a top display could be accompanied by a bottom trackpad, foldable in a manner like a notebook.
In Apple's concept, the top touch panel may be translucent, so that when it is folded over on top of a bottom display, the two can complement each other.
"The display element and the array element may be configured with respect to each other, where different configurations can be associated with different operating modes," the filing reads. "For example, when the array elemtn lies over the display element screen so that the display screen is viewable through the array element, the array element can function as a touch screen."
The trackpad on a MacBook could even be used as a sort of window when the device is closed, in one example provided by Apple. It shows a closed MacBook with the screen still displaying through a slot where the translucent trackpad is located, displaying e-mail alerts or other pertinent information while the computer is closed.
Both surfaces could also be touch-sensitive and could be utilized at the same time in such a device. Apple's system could simultaneously "interpret or accept input from any of the devices according to the computer's mode of use."
The filing notes that touchscreens are desirable for certain tasks, while touchpads are sometimes better suited for other functions. A new device could automatically designate one touch panel for certain types of tasks, while the other touch-sensitive surface would be enabled for tasks more appropriate for its use. But Apple notes that this method could be too complicated for practical use.
"Despite the availability of useful input tools, making the appropriate input tool available for the user remains a problem," the filing reads. "It is therefore a goal of this invention to solve or at least reduce the problems associated with input tools on computing devices."
The proposed invention was first filed with the USPTO in September of 2006. It is credited to Chris A. Ligtenberg.