Signal processing device and method for reducing influence on column noise detection from defective pixels

A signal processing method for a signal processing device having a solid-state image pickup element having:

• a pixel part including pixels arrayed in a matrix of lines and columns, the pixel part including an effective pixel area to be irradiated with light, and a vertical light-shielded pixel area where irradiation of light is shielded,
• a vertical scanning circuit which controls control electrodes of pixels arranged in a line and connected by a vertical selection line,
• a horizontal scanning circuit which controls control electrodes of vertical signal lines to output pixel signals to horizontal signal lines, and
• an output circuit which outputs pixel signals from the horizontal signal lines, the method comprising:
• clamping black level values of pixel signals from the vertical light-shielded pixel area and the effective pixel area to a predetermined reference value;
• determining a threshold value, the threshold value defining the bounds of a range of acceptable black level values that fall between the predetermined reference value and the threshold value, the threshold value being defined by calculating a standard deviation of random noise from the vertical light-shielded pixel area and performing a multiplication operation on the standard deviation to find the threshold value;
• determining whether pixel signals from the vertical light-shielded pixel area which have the black level value clamped to the reference value exceed the threshold value;
• detecting a defective pixel among pixels arranged in the vertical light-shielded pixel area when a pixel signal exceeds the threshold value;
• and
• correcting the detected defective pixel by adjusting the pixel signal level of the detected defective pixel to equal the threshold value.

A signal processing device comprising:

• a solid-state image pickup element having:
• a pixel part including pixels uniformly arrayed in a matrix of lines and columns, the pixel part including an effective pixel area to be irradiated with light, and a vertical light-shielded pixel area where irradiation of light is shielded,
• a vertical scanning circuit which controls control electrodes of pixels arranged in a line and connected by a vertical selection line,
• a horizontal scanning circuit which controls control electrodes of vertical signal lines to output pixel signals to horizontal signal lines, and
• an output circuit which outputs pixel signals from the horizontal signal lines;
• a clamp section which clamps, to a predetermined reference value, black level values of pixel signals from the vertical light-shielded pixel area and the effective pixel area, which are outputted from the output circuit;
• a threshold determination section which determines a threshold value, the threshold value defining the bounds of a range of acceptable black level values that fall between the predetermined reference value and the threshold value, the threshold value being defined by calculating a standard deviation of random noise from the vertical light-shielded pixel area and performing a multiplication operation on the standard deviation to find the threshold value;
• a determination section which determines whether pixel signals from the vertical light-shielded pixel area that have the black level value clamped to the reference value exceed the threshold value;
• a defective pixel detector which detects a defective pixel among pixels arranged in the vertical light-shielded pixel area when a pixel signal exceeds the threshold value;
• and
• a signal processor which corrects the detected defective pixel by adjusting the pixel signal level of the detected defective pixel to equal the threshold value.