A laser scanning unit includes a laser light source, rotating polygon mirror, drive motor, and entry detection, intensity detection, intensity adjustment, and drive control portions. The control unit includes a measuring unit for measuring a value indicating a recording amount of recording performed on the recording medium. The receiver receives the data, and the receiver determines the first channel quality known to the transmitter from said data via the at least one used transmission parameter as well as a second, current channel quality via the quality of the received data; and the receiver compares the first channel quality with the second channel quality.