Patent ID: 7471416

Claim:
An apparatus for processing signals, comprising: a sample-and-hold section to sample and hold a black signal level and an image signal level, both of which are included in an analogue image signal inputted from an image capturing element; an analogue-to-digital converting section to convert said analogue image signal to digital image data within a predetermined number of conversion steps, said predetermined number being larger than a number of conversion steps corresponding to a differential value between said black signal level and said image signal level acquired by said sample-and-hold section; a digital subtracting section to subtract black digital-image data representing said black signal level from signal digital-image data representing said image signal level, and to output digital-image data and resulting from the subtraction, said black digital-image data and said signal digital-image data being converted by said analogue-to-digital converting section; and a digital image data processing section to process said digital image data outputted by said digital subtracting section; wherein said predetermined number of conversion steps is calculated according to the relationship: Na≧Nt× ( R/R max), where: Na is said predetermined number of conversion steps, Nt is a number of signal steps acquired by said digital image data processing section, R is a predetermined conversion range established in advance for said analogue-to-digital converting section, and Rmax is a maximum amplitude of said analogue image signal inputted from said image capturing element.