| 摘要 |
A condensing lens (10) carries an optical filter (16) in a central portion thereof which includes an optical axis. The filter intercepts ultraviolet rays and infrared rays except for those which are incident on an exposed peripheral portion (12) of the lens. The filtered light is conducted by a light conducting cable (14) to a plant culturing station for photosynthesis. The light receiving end of the cable is usually located at the focal point of visible rays output from the lens and, at the time of harvest, at the focal point of ultraviolet rays The lens may be entirely covered with the filter. |
