A 3648 element CCD linear image sensor

A 3648 element CCD image sensor has been developed, which can read a 8 1/2-inch paper with 16 elements/mm resolution and achieves 20 MHz operation. Features of device design are small chip size of 1.1 mm × 31 mm for low cost and speeding-up electrodes for high speed scanning. The small chip is realized by photodiodes of 8 µm × 8 µm and 3-level poly-silicon electrode structure. To suppress degradation of resolution due to closely spacing photodiodes, the sensor uses p-well structure and obtains the MTF value of 70 % at Nyquist limit for green light (550 nm). The speeding-up electrode is arranged between the CCD register and the output circuit and is connected to the independent clock line. This structure enables the sensor to be operated at 20 MHz data rate.