| 摘要 |
PURPOSE:To maintain a good receiving state at all times even in case of an optical signal received from any direction, by placing plural photodetectors so that the half-power angles coincide with each other, and constituting so that the composite directional pattern becomes nearly circular. CONSTITUTION:Plural photodetectors, for instance, SiPIN photodiodes 23-25 are used, and they are placed and combined so as to become like a triangle when seeing from the almost upper face. As for the directional pattern of photodetecting sensitivity in this case, the diode 23, the diode 24 and the diode 25 become like a full line (a), a full line (b) and a full line (c), respectively, and when these respective directivity are synthesized against a photodetecting point P, a nearly circular synthesized directivity is obtained as shown by a broken line (d). That is to say, a directivity of 360 deg. is obtained against incident light. In this way, for instance, even if a head is moved by 360 deg. in a state that a wireless head phone is put on, a good receiving state can be maintained at all times. |
