| 摘要 |
PURPOSE:To make the light receiving device nondirectional in three dimensions and to eliminate the limitations of its installation place by using a light receiv ing element which is annular on the whole and includes triangularly sectioned prisms united together with light receiving pellets. CONSTITUTION:The light receiving device has the light receiving element 1 where the prisms 50 which are annular or in the shape of a frustum of a right circular cone on the whole and triangularly sectioned are united together with the light reception pellets 1C. Namely, the prisms are provided on both the sides of the light receiving element 1 in optional section containing a front axis. The directivity in the section is in a range of 0=+ or ->=90 deg. and the characteristic rotated on the front axis is the whole directivity. Consequently, the directivity is hemispherical and sensitivity even to infrared rays which is made incident on a filter 60 in any direction is obtained. Therefore, when light receiving devices are provided on both sides of a speaker device, the directivity of the light receiving device is composed and the device becomes nondirectional in three dimensions. |
