As described above, the pixel signal from the pixel 10C at the central position alone is read out to the third vertical signal line VL3, the pixel signals from the nearby pixels 10B and 10D are read out and combined on the second vertical signal line VL2 and the pixel signals from the peripheral pixels 10A and 10E are read out and combined on the first vertical signal line VL1. As a result, a greater weight, in comparison to the weight applied to the pixel signals from the other four pixels 10A, 10B, 10D and 10E, can be applied to the pixel signal from the pixel 10C at the central position.
In the example presented in FIG. 5(c), a greater value may be set for the electric current generated in the second electric current source 26 in comparison to the value of the electric current generated in the first electric current source 25. In such a case, a greater weight, in comparison to the weight applied to the pixel signals from the two peripheral pixels 10A and 10E, can be applied to the pixel signals from the two nearby pixels 10B and 10D. It is desirable that the electric current generated in the third electric current source 27 in this situation achieve a value equal to or greater than the value of the electric current generated in the second electric current source 26.