FIG. 5(b) presents a chart illustrating a pixel signal readout method that may be adopted when combining pixel signals from four pixels 10 disposed consecutively along the column direction. The value of the electric current generated in the second electric current source 26 is set greater than the value of the electric current generated in the first electric current source 25. The pixel signals from the two central pixels 10B and 10C are read out to the second vertical signal line VL2 where they are combined, and the pixel signals from the pixels 10A and 10D respectively located immediately above and below the two central pixels 10B and 10C, are read out to the first vertical signal line VL1 where they are combined. Then, the arithmetic unit 50 generates a sum pixel signal by adding together and averaging the combined pixel signal derived from the pixels 10B and 10C and the combined pixel signal derived from the pixels 10A and 10D. Since the electric current generated in the second electric current source 26 takes a value greater than the value of the electric current generated in the first electric current source 25 as described earlier, a greater weight, compared to the weight applied to the pixel signals from the pixels 10A and 10D at the top and the bottom, can be applied to the pixel signals from the two central pixels 10B and 10C.
The following advantageous effects can be achieved through the embodiment described above.
