US Patent 7545419 Solid-state pixel sensitivity variation correcting image-sensing device

Switches SHS and RSM are turned on to hold an image signal at a negative electrode of a capacitor Cs, then a switch SHN is turned on to hold a noise signal at a positive electrode of a capacitor Cn. Then a switch RSP is turned on and then a switch MIX is turned on to combine together the image and noise signals thus held and thereby produce, as a voltage signal, a noise-free image signal at the node between the capacitor Cs and the switch MIX. Then a switch Sx is turned on to output the noise-free image signal.