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In addition to a camera detecting the direction of a finger swipe, the phone's accelerometer could also be used to interpret a user tapping the iPhone, allowing control of the handset while on a call without taking the phone away from one's ear.
The application revealed this week, entitled "Camera as Input Interface," was originally filed for on Aug. 21, 2008. It is credited to Chad Seguin, Justin Gregg and Michael Lee.
The invention aims to make it easier to control a phone by utilizing the camera at times when it is typically idle. It describes fast forwarding or rewinding of a voicemail by swiping a finger across the camera, or pausing and resuming playback by tapping the back of the phone.
"These actions allow the user to control functions of voicemail review without removing the device from over his ear," the application reads.
The functionality could potentially extend beyond voicemail, allowing users to merge calls, place calls on hold, or switch between multiple simultaneous calls by simply tapping the device. Such controls could be customized by the user to their liking.
Apple could also choose to adopt the control method for traditional phone use, in addition to in-call controls.
"Furthermore, a user may navigate a document being shown on a display screen of the device by guiding his finger over the camera lens," the application reads. "While viewing the display screen, the user holds the device in the palm of his hand in a supine position. Rather than pressing or sliding directional buttons next to the screen or touching a touch screen to navigate a webpage document or contacts list, the user may move his finger over the camera lens in the direction he wishes to navigate the page."
Apple in the past has filed patent applications describing mobile devices with touch panels on the reverse side, allowing users to control a device without obscuring the screen with their fingers. In January, a rumor even alleged that the next-generation iPhone would have a Magic Mouse-like touch panel for its plastic back casing.