Auto white balance circuit responds to light source and movie camera using auto white balence circuit responds to light source

摘要

PURPOSE: An automatic white balance circuit reacting on a change of a light source is provided to analyze an inputted image signal in two stages to sense whether the signal is changed by a light source or changed by a camera motion, and to enable an AWB(Automatic White Balance) operation if the signal is changed by the light source, thereby excluding an inappropriate AWB operation. CONSTITUTION: A pixel comparator(100) operates in response to a change of a light source. An AWB selector(200) decides whether to enable an AWB operation in response to an output of the pixel comparator. A coefficient decider(300) generates an AWB coefficient in response to an output of the AWB selector. A coefficient output unit(400) decides whether to use an output of the coefficient decider in response to an output of the AWB selector. Image frames are applied to the first pixel comparator(110). The first pixel comparator analyzes color data existing in one image frame. If color data of each pixel is irregularly distributed, the first pixel comparator enables an AWB operation. If three primary colors of the pixels are partially distributed, the first pixel comparator disables the AWB operation.