We made a prototype rear-view mirror with built in an image sensor. Useful driver assistance systems, imageprocessing is one of the best approach and it is necessary to develop a suitable image sensor for acquiring driver's images. We developed an image sensor that could acquire driver's image under several environments and investigated the methods to detect driver's eye blink for the "Driver's Monitor System" that estimated driver awareness level. Described in this paper, are the superior characteristics and evaluation results of the prototype rear-view mirror.