Patent ID: 7116360

Claim:
An image signal processing circuit that converts an analog image signal to digital image data having values that change in a polyline with respect to changes in the analog image signal, the image signal processing circuit comprising: an upper bit A/D converter that generates an upper bit digital signal indicating a section of the polyline corresponding to the analog image signal; a D/A converter that converts the upper bit digital signal to an upper bit analog signal; a signal differential output circuit that subtracts the upper bit analog signal from the analog image signal to generate a lower bit analog signal; a lower bit A/D converter that receives the lower bit analog signal and the upper bit digital signal, and that converts the lower bit analog signal to a lower bit digital signal by comparing the lower bit analog signal with step potentials having potential differences determined by the upper bit digital signal, the step potentials increasing as the upper bit digital signal increases; and an encoder circuit that generates the digital image data by combining the upper bit digital signal and the lower bit digital signal.