抄録
A new focusing method for zoom lenses is developed. Although a part or the whole of a zoom lens is used as a focusing group, the focusing mechanism can be realized with single cam mechanism. One remarkable effect of this method is to shorten the closest object distance of wide angle zoom lens. The basic idea of this method is to obtain the simple relationship between the displacement of the focusing group, focal length and object-image distance. Two approximate relations and a best fit one with sufficient accuracy are obtained and discussed.
