| 摘要 |
PURPOSE:To increase the power supply efficiency with a simple constitution, by transmitting straight line poralized light obtained from an audio signal via a light emitting element to an optical isotropic substance, transmitting modulated light corresponding to a PWM signal modulated with the audio signal, and making photoelectric conversion and demodulation. CONSTITUTION:An acoustic signal read out 14 at the transmission side is inputted to a comparator 17, and a pulse signal with repetitive frequency equal to the frequency of a triangle wave 16 is modulated on the acoustic signal level to obtain a PWM signal. On the other hand, the light obtained via an LED 19 is inputted to a polarized element 22 for straight line poralization and to an optical isotropic substance 23 of specific nature. In this case, electric field is exerted by using a PWM signal and the poralized light direction is oscillated toward two directions. Modulated light is transmitted by eliminating one straight line poralization with a photodetector 24. At the reception side, the modulated light is in photoelectric conversion at a phototransistor 25, audio signal component only is picked up at an LPF 27 and it is reproduced at a speaker 28. |
