Systems and methods are provided for detecting objects of an object class, such as faces, in an image sensor. Broadcast reception recorders receive broadcast content broadcast by a broadcasting apparatus and record it in built-in hard disk drives. The monophonic input signal is applied to a perspective filter that produces a differential-mode signal and to an equalizer filter that produces a common-mode signal. At least one of the second semiconductor layer and the third semiconductor layer has a portion with its sheet dopant concentration varying along a depth direction of the semiconductor substrate.