Patent ID: 8098328

Claim:
An image signal processing apparatus comprising: a measuring means for measuring in a unit frame period whether each pixel in a designated measurement region of an input image signal has a signal level less than a threshold value; a black band detecting means for detecting a black band region included in the input image signal on the basis of a measurement result from the measuring means; a basic region providing means for providing a basic region as a basic part to be measured; an increment/decrement value providing means for providing an increment/decrement value in the measurement region; and a measurement region determining means for determining the measurement region on the basis of the basic region and the increment/decrement value, wherein the increment/decrement value providing means resets the increment/decrement value to half of the previous value, the measurement region determining means selectively resets a new measurement region by adding or subtracting the new increment/decrement value to or from the previous measurement region depending on whether the boundary between a black band region and an image region is detected by the black band detecting means, and the measuring means performs the measurement on a new measurement region.