Development of a pen-shaped scanner and its applications

A truly portable scanner would add another dimension to mobile computing. U sing the compact optical configuration single optical fiber imaging (SOFI), a handheld scanner can be built inside a pen-shaped housing. Here, an imag e sensor formed on a glass substrate is used. Each photodiode of the image sensor has multiple apertures coupled to multiple optical fibers. The light is transmitted through the glass, the apertures and the fibers successivel y, and a document is illuminated. Scattered light comes back in the same fi bers and is detected by a sensitive part of the photodiode. Therefore, a si ngle fiber is involved to both illuminate the document and detect the refle cted light. By incorporating light-absorbing material at the fiber boundari es, optical crosstalk inside the fiber array is suppressed. The design of t his SOFI-based scanner is studied in detail. A prototype is developed: the width of its housing and the input length are 13 and 110 mm, respectively. The key components are an image sensor fabricated by a-Si and poly-Si thin film technology, a 2 mm-thick array of optical fibers with 0.9 numerical ap erture, and an array of three-color LEDs. Images of color documents and fin gerprints are successfully acquired by this scanner, (C) 1999 Society of Ph oto-Optical Instrumentation Engineers. [S0091-3286(99)00212-3].