Application of optical fiber array to contact-type image sensors

In order to develop small-size, high-fidelity input for reading letters and images, the authors studied the use of an optical fiber array to obtain compact contact-type image sensors. The optical system exhibited a modulation transfer function of 50% at 8 lp/mm, about the same depth of field as that of a rod lens array; a uniformity of less than ±4.5%; and a transmittance of about 25%. The illuminance achieved by the system is about four times as large as that of the conventional one, and the resolution characteristics of the system are excellent as well. A 2048-bit, 70-bit/mm linear charge-coupled device or a 1728-bit, 8-bit/mm a-Si:H thin-film linear photodiode array is used as the photodetector of the image sensor. Letters (e.g. 8 point size) and images of documents were read and reproduced by a thermal printer successfully