In the example presented in FIG. 5(c), a third vertical signal line VL3, in addition to the first and second vertical signal lines VL1 and VL2, and a third electric current source 27 connected to the third vertical signal line VL3 are disposed in correspondence to a column of pixels disposed consecutively along the column direction. The pixel signal from the pixel 10C at the central position is read out to the third vertical signal line VL3, whereas the pixel signals from the nearby pixels 10B and 10D, located immediately above and below the central pixel 10C are read out to the second vertical signal line VL2 where they are combined. The pixel signals from the peripheral pixels 10A and 10E respectively adjacent to the pixel 10B and the pixel 10D located immediately above and below the central pixel are read out to the first vertical signal line VL1 where they are combined. The arithmetic unit 50 generates a sum pixel signal by adding together and averaging the combined pixel signal on the first vertical signal line VL1, the combined pixel signal on the second vertical signal line VL2 and the pixel signal from the central pixel 10C on the third vertical signal line VL3.
