Long linear image sensor

An a-Si H photosensor array has been successively applied to a long linear image sensor and high-performance area image sensor. A photodiode in which a-Si H is sandwiched between ITO and metal electrodes is used because of its short photoresponse time. In this structure, blocking contacts at both electrodes are necessary to prevent carrier injection from the electrodes. 

Thin-film technology is useful in fabricating these devices. CdS-CdSe photoconductive sensors (Boronkay et al., 1978 Komiya et al., 1981) and As-Se-Te photodiodes (Tsukada et al., 1977) were applied to the long linear-image sensor. As-Se-Te photodiodes (Tsukada et al., 1979) and ZnSe - ZnCdTe photodiodes (Terui et al., 1980) were used in the area image sensor. However, there are some problems with these sensors long photoresponse time for the CdS-CdSe sensor, thermal instability, and low yield for the As-Se-Te sensor, and a high-temperature process for the ZnSe-ZnCdTe sensor. 

A contact linear image sensor can make the equipment compact, because it does not require a high-magnification lens system. The sensor unit consists of an illuminator, a compact optical guide, and the long linear photosensor array, which is, for example, 210 mm long for the iso-A4... 

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