IMAGE PICKUP UNIT

PURPOSE: To improve deterioration in the output of a detector located in a border between reflection and transmission at the time of increasing more picture elements by a spectroscope unit which mutually has a reflection surface and a transmission surface in a multielement image pickup unit. CONSTITUTION: The picture element is increased in the border part between reflection and transmission so as to permit the detector elements of both are mutually overlapped in the detector 3 which is arranged on the backward image forming surface of the spectroscope 9 mutually having the reflection surface and the transmission surface. After the respective detector outputs are converted into digital signals respectively by an amplifier 4 and an A/D converter 5, the corresponding picture element by reflection and transmission is added in an adder 17 and the picture element in the border part between reflection and transmission is permitted to be the signal in the same level as that of another part so that the deterioration of the S/N is prevented.