An optical sensor device for use in optical instruments is disclosed. The optical sensor device is provided with an optical sensing region having at least one sensor element responsive to incident light for producing a charge, first and second charge storing regions each having the same number of charge storage elements as that of said sensor elements for accumulating the charges produced from said sensor elements, a first gate region for controlling the transfer of charge from said optical sensing region to said first charge storing region, and a second gate region for controlling the transfer of charges from the optical sensing region to the second charge storing region. Upon alternate application of a voltage to said first and second gate regions, the charges produced from said optical sensing region are alternately accumulated on said first and second charge storing regions.