| 摘要 |
PURPOSE:To execute the transmission and reception of an optical signal into the finite area of a free space with satisfactory sensitivity without accompanying difficult control operation by providing the condensing means of an output optical signal in a transmitter and providing a photo-detecting means to have a sharp directional characteristic in a receiver. CONSTITUTION:In a transmitter 1, a reflecting mirror 8 is provided so that the optical signal to be outputted from a light emitting source 5 can be condensed in an optical lens 7 side and so as to go forward and backward along the shaft line direction together with the light emitting source 5 in a lens holder 6. By the movement forward and backward of the light emitting source 5, a distance between the light emitting source 5 and lens 7 is controlled to the size of an limited area, in which the optical signal is transmitted, and the transmitting area of the optical signal can be easily controlled by the lens 7. In a receiver 2, a hood 13 is formed to shield a light, which is made incident from a direction excepting for a constant direction. Then, the element of the sharp directionality is used for a photo-detecting element 14 and the light to be made incident from a direction excepting for the normal of a photo-detecting surface is hardly photo-detected. Thus, without accompanying the difficult control, the transmission and reception of the optical signal into the finite area of the free space can be executed with the satisfactory sensitivity. |
