An oscillation circuit uses a SAW oscillator and is able to control the oscillation frequency easily and correct the temperature characteristic of the oscillator so that an oscillation signal with high temperature stability can be generated. The method employs multi-symbol encapsulation, wherein multiple OFDM symbols are grouped together in cyclic frames having a single cyclic guard portion, for example a cyclic prefix, with multiple OFDM symbols sandwiched between each two consecutive cyclic guard portions. Each prism is mounted for rotation at a desired speed of rotation and in a desired direction to scan the light beam over the target.