1. A two-dimensional solid-state image sensor comprising: a photoelectric converter having a plurality of non-destructive readout type image sensor cells arranged in a predetermined form for exposure to a light pattern and for storing a charge in at least some of said cells related to the light pattern to form stored information which is not destroyed by reading out the stored information; an exposure detector connected to the photoelectric converter for reading out the stored information of a plurality of predetermined ones of the cells during the exposure, for obtaining an added value of the stored information thus read out and for detecting when the added value reaches a predetermined level to form a detected signal; an exposure controller connected to the exposure detector for being supplied with the detected signal from the exposure detector to control at least one of; a charge storage time of each image sensor cell, the intensity of light incident on the image sensor cells and a photosensitivity of the image sensor cells, to terminate the building of charge in the cells; and a scanner connected to the photoelectric converter for scanning the photoelectric converter to read out the stored information of the image sensor cells after the building of charge has been terminated.