| 摘要 |
PURPOSE:To obtain a teleconverter of compact constitution which enables automatic focus adjustment by providing a conversion lens which meets specific requirements behind a photographic lens. CONSTITUTION:A conversion optical system 7 which multiplies the focal length of a photographic lens to be mounted by a specific factor and a driving device 20 which moves at least part of said conversion optical system 7 in an optical- axis direction are provided in an adapter body; when the F value of the photographic lens determined by the maximum photodetection angle of a focusing detector is Fd and the full-aperture F value of the darkest photographic lens to be mounted is Fo, the magnification (k) of the conversion optical system 7 is less than or equal to Fd/Fo. the conversion lens 7 is composed of a biconcave lens, but any negative lens group is usable and for the improvement of various aberrations, the system consists practically of plural lens groups of positive and negative lenses in combination. In focal adjustment, all of them may be moved and some of them are moved upon occasion. |
