Patent ID: 7750955

Claim:
An image signal processing apparatus for subjecting to processing an image signal from a solid state image sensor having a plurality of effective pixels and a plurality of light shielded pixels, comprising: averaging means for calculating and outputting average values of signals from the light shielded pixels and holding the calculated average values; adding means for providing an output signal level obtained by superimposing a set threshold value, for determining whether a signal from the light shielded pixel is at an abnormal level or not, on the average values held by the averaging means; comparing means for comparing the level of the signal from the adding means with levels of the signal from the light shielded pixels; and clamping means for adjusting signals from the light shielded pixels to a predetermined level in accordance with the average value calculated by the averaging means, wherein signals from the light shielded pixels or the average values held by the averaging means are selectively supplied to the averaging means in accordance with a comparison result by the comparing means, and wherein, when the difference between the average value held by the averaging means and the level of signals from the light shielded pixels is larger than the set threshold value as determined by a comparison by the comparing means, the average value previously held by the averaging means is supplied to the averaging means instead of the signals from the light shielded pixels, and the signals from the light shielded pixels are provided to the average means instead of the average value previously held by the averaging means when the difference between the average value held by the averaging means and the level of signals from the light shielded pixels is smaller than the set threshold value as a result of comparison by the comparing means.