Using backlight intensity for device identification

This paper presents a method for identifying handheld devices (e.g. smart phones and pocket PCs) to facilitate the use of these devices as tangible interfaces for desktop augmented reality systems. The proposed system leverages the ability of these handheld devices to programmatically control their backlight intensity to display a binary code. The codes produced are non-intrusive, require no specialized hardware, and can be generated with most handheld devices. This technique is shown to accurately and robustly identify up to 16 different devices in under 500 msec and is easily expandable to 256 or more devices.