Defect correction apparatus for solid state imaging devices including inoperative pixel detection

Claim 1

A defect correction apparatus for a solid state imaging device having an array of pixels for producing image scene pixel data when exposed to scene light comprising: a frame buffer having memory locations corresponding to the pixels of the imaging device and being responsive for storing values of shuttered dark pixel data for each pixel in the corresponding memory locations prior to exposure of the image device to scene light; register means responsively coupled to the imaging device and having an output coupled to the frame buffer for sequentially clocking dark pixel data into the frame buffer for storage and for subsequently clocking selected image pixel data into the corresponding frame buffer locations for replacing the dark pixel data with image pixel data of the scene; wherein the register means includes and analog-to-digital (A/D) converter for producing digital outputs in response to analog inputs representative of pixel data from corresponding elements of the imaging device; a comparator having an output operatively coupled to the register means and being responsively coupled to the register means and being responsively coupled to the frame buffer for producing either an enable output for enabling the register means when the dark pixel data is less than a selected threshold indicative of an operative pixel or an inhibit output for inhibiting the register means when the dark pixel data is greater than the threshold indicative of an inoperative pixel, such that, the dark pixel data for a particular location is replaced in the buffer by image pixel data for a corresponding pixel when the pixel is operative an dark pixel data for such location is replaced by image pixel data from an operative pixel immediately prior to the defective pixel when the pixel is inoperative and means for adjusting the analog input to the A/D converter in accordance with the value of dark pixel data in the buffer for the corresponding element.