Patent ID: 8463140

Claim:
A reception device comprising: a light receiving unit which receives intensity-modulated light from a transmission device, wherein the transmission device executes phase modulation to a bit stream as an object to be transmitted and emits the intensity-modulated light which has an intensity changing at a preset time cycle and a phase changing in response to the phase modulation, and the phase is maintained during M cycles (where M is an integer at least 2); a phase calculation unit which detects the intensity of the intensity-modulated light p times per cycle of the intensity-modulated light (where p is an integer at least 3) and repeatedly calculates the phase of the intensity-modulated light on the basis of a result of the detection; and a demodulation unit which executes demodulation, which corresponds to the phase modulation, to the phase calculated by the phase calculation unit, and generates transmitted bit stream, wherein the light receiving unit comprises: a photoelectric conversion unit which generates charges corresponding to an intensity of the intensity-modulated light as received; p charge accumulation units, which each accumulates charges generated by the photoelectric conversion unit m times (m is an integer at least 1 and at most M) in the same cycle as that of the intensity-modulated light; and a reset unit which resets the charges accumulated by the charge accumulation units after reading the accumulated charges, wherein each charge accumulation unit accumulates the charges at mutually different predetermined timings in one cycle of the intensity-modulated light, wherein the phase calculation unit detects the intensity of the intensity-modulated light on the basis of the accumulated charges by reading the charges accumulated m times in each of the p charge accumulation units, wherein the reset unit of the light receiving unit resets the charges after the charge accumulation units accumulate the charges m times, and the phase calculation unit reads the charges accumulated m times, and wherein p distribution gates are configured to permit the p charge accumulation units to accumulate charge at different times from one another during each cycle.