In sending a transmission signal, in particular a mobile radio signal, to a receiver, the transmission signal is processed according to a modulation coding scheme MCS and subjected to amplitude limited to obtain a specified ratio of maximum to average transmission power PAR. More specifically, in one aspect, a method for detecting interference in a signal is provided. The apparatus outputs the first and second position information as the viewpoint position of a subject. In addition, the second lens and the third lens have paraxial focal lengths whose signs are different.