| 摘要 |
PURPOSE:To transfer a large amount of information accurately and efficiently without using any high-output light emitting element by varying the transfer speed of a light signal according to the intensity of detected background light. CONSTITUTION:The quantity of the background light is detected by a photodetecting element 14 and converted into an electric signal, whose DC component only is supplied through an integration circuit 18 to the side of an amplifier 20 and voltage-amplified, so that a signal of frequency corresponding to the voltage is supplied from a voltage- controlled oscillator 23 to a transmitting circuit 24. Then the quantity of the background light increases and the output frequency of the voltage-controlled oscillator 22 decreases. The transmitting circuit 24 stores a sound signal inputted from a microphone 25 in a memory, performs time-base compression, and sends the signal to the light emitting element 26. In this case, the transfer speed of the signal outputted from the transmitting circuit 24 is proportional to the frequency supplied from the voltage- controlled oscillator 22 to the transmitting circuit 24. Namely, the transmitting circuit 24 supplies the signal to the light emitting element 26 with a clock signal proportional to the output frequency of the voltage-controlled oscillator 22. Therefore, the transfer speed of the light signal outputted from the light emitting element 26 is lower and lower as the quantity of the background light detected by the photodetecting element 14 is larger and larger. |
