Real-time digital processor for producing full resolution color signals

Abstract

A digital processing system is described for processing luminance and chrominance signals from a single, multi-color image sensor. By concentrating signal improvements and corrections into an application-dependent post-processing phase, the pre-processing functions are isolated in a signle, generic pre-processor integrated circuit that provides fully interpolated color signals in a real-time system by utilizing a fully pipelined architecture. The pre-processor circuit separates luminance and chrominance interpolation so as to operate partly in quantized linear space and partly in quantized logarithmic space. The image signals are processed in a black reference clamp, a defect concealment circuit and a color separation and luminance interpolation circuit in linear space, using right shifts and additions to approximate predetermined multiplications. The signals are then transformed into hue signals and processed in log space for white balance and chroma (hue) interpolation. With the log green signal separately adjusted for gain, quantized red, green and blue signals are output from the pre-processor integrated circuit.