Predictive coding on-sensor compression

This paper presents the design and measurements a predictive coding on-sensor compression CMOS imager. Predictive coding is employed to decorrelate the image. The prediction operations are performed in the analog domain to avoid quantization noise and to decrease the area complexity the circuit. The decorrelated image is encoded with a bank column-parallel entropy encoders. Each encoder is combined with a single-slope analog-to-digital converter (ADC) to reduce area complexity and power consumption. The area savings resulting from such combination allow to integrate an ADC and entropy encoder at the column level. A prototype chip was fabricated in a 0.35 μm CMOS process. The output of the chip is compressed bit stream. The test chip occupies a silicon area of 2.60 mm x 5.96 mm which includes an 80 x 44 APS array. Tests the fabricated chip demonstrate the validity of the design.