Logarithmic-Converting CCD Line Sensor

Abstract

A logarithmic-converting CCD line sensor incorporating logarithmic-converting circuits which utilizes MOSFET's subthreshold operation was developed. The sensor has 2240×3 pixels that are 12μm×12μm. It outputs a signal logarithmically proportional to the integrated amount of the incident light over more than five orders of magnitude in intensity, and therefore it can take bright and dark objects at the same time. Furthermore, its output signal is proportional to the densities on the prints or the films. Therefore, the digital data converted from its output signal retains image quality, and the shading can be corrected by just adding or subtracting. We expect that this technology will be very useful for digital copiers, camera type scanners, and film scanners.