Experimental studies in application of a-Si : H to a photoreceptor of electrophotography and vidicon target of image pickup tube are summerized. Two types of blocking contacts, homojunction and heterophase blocking, have been proposed to sustain the sufficient charges on the photoreceptor and a low current level of vidicon target in the dark. An "intrisic" a-Si : H prepared in the optimized conditions is applicable as the photoconductive layer of the both devices. Excellent photoresponse can be achieved in the charge depletion devices with the blocking contacts in whole visible region. With in the framework of our laboratory scale study, we conclude that a-Si : H is a promising material as a photoconductor of image devices