Apparatus for correcting for defective pixels in an image sensor

Abstract

A solid state image pickup apparatus comprises a solid state imager having a plurality of pixels and which outputs a signal corresponding to light incident thereon, a sample and hold circuit for sampling and holding analog output signals from respective pixels of the solid state imager in response to a sampling signal, a low-pass filter connected to the analog output of the sample and hold circuit for eliminating a high frequency component therefrom so as to output a filtered signal, an analog-to-digital converter for converting the filtered signal to a digital filtered signal, a memory for storing position data indicative of a position of a defective pixel, a circuit for stopping the supply of the sampling signal to the sample and hold circuit in response to the position data indicating a defective pixel so that the output signal from the defective pixel is replaced with the analog output signal from a pixel read immediately prior thereto, an interpolating circuit connected to the analog-to-digital converter for interpolating a digital signal corresponding to the position data indicating a defective pixel by using the digital signals corresponding to other pixels surrounding the defective pixel so as to generate an interpolated signal, and a switch for selectively outputting the digital filtered signal and the interpolated signal in accordance with the position data.