In FIG. 5(a), the pixel signals from pixels 10A and 10C located above and below the pixel at the center are read out to the first vertical signal line VL1 where they are combined and the pixel signal from the central pixel 10B is read out to the second vertical signal line VL2. The combined pixel signal read out on the first vertical signal line VL1 and the pixel signal from the pixel 10B at the central position read out to the second vertical signal line VL2 are added together and averaged at the arithmetic unit 50, as has been explained earlier.
FIGS. 5(b) and 5(c) each present a chart illustrating a pixel signal readout method that may be adopted when pixel signals from five pixels 10 disposed consecutively along the column direction are combined. In the example presented in FIG. 5(b), the pixel signals from pixels 10A, 10B, 10D and 10E, excluding the central pixel, are read out to the first vertical signal line VL1 where they are combined, and the pixel signal from the pixel 10B at the central position is read out to the second vertical signal line VL2. The combined pixel signal derived from the four pixels 10A, 10B, 10D and 10E, read out on the first vertical signal line VL1 and the pixel signal from the central pixel 10B read out to the second vertical signal line VL2 are added together and averaged by the arithmetic unit 50.
