an image reader in which a plurality of light - sensitive cells arranged in an array in a line image sensor are divided into a predetermined number of blocks , and the blocks are sequentially selected to sequentially drive the light - sensitive cells in each of the blocks to produce image signals . charging switches are provided for charging the light - sensitive cells via block selector switches . the charging switches are activated after a signal read time assigned to each light - sensitive cell has expired to thereby shorten the charging time necessary for the light - sensitive cell . the block selector switches are each actuated at a predetermined timing while the charging switches are activated , thereby preventing noise due to switching actions of the block selector switches from being introduced into image signals .