1. Field of the Invention
The present invention relates to a zoom lens system for a compact camera, in particular, relates to achieving high zoom ratio and miniaturization of the zoom lens system.
2. Description of the Related Art
In a zoom lens system for a compact camera, there is no need to provide a long back focal distance, unlike a zoom lens system for a single lens reflex (SLR) camera which requires a space for providing a mirror behind the photographing lens system. Accordingly, a compact camera generally employs a telephoto type lens system in which positive and negative lens groups are provided in this order from the object, while a SLR camera generally employs a retrofocus type lens system in which negative and positive lens groups are provided in this order from the object.
If a zoom lens system is constituted by a two-lens-group arrangement, the number of lens elements therein can be reduced, and the structure thereof can be simplified, so that a small and light-weight zoom lens system can be achieved, and further, such a zoom lens system is advantageous in regard to production costs. Therefore a two-lens-group arrangement has frequently been employed in a zoom lens system for a compact camera. However, in a two-lens-group zoom lens system, if attempts are made to obtain a higher zoom ratio and further miniaturization, field curvature becomes larger at intermediate focal lengths in a zooming range, and thereby it is difficult to achieve a higher zoom ratio and further miniaturization.
USPTO Backgrounds
USPTO Backgrounds