Lens system for small-format (miniatures) cameras - includes an (anastigmatic) image field flattening element made of acrylic glass

摘要

A lens system for a photographic camera wherein the ratio of equiv. focal length to diagonal of image field is 1.3 or less, has a device defining a diaphragm aperture. There is a 1st biconvex collecting lens element, a 2nd biconcave dispersing-lens element, a 3rd biconvex collecting-lens element; and a 4th concave-planar element which is an image field flattening element. The absolute value of the refracting power of the 2nd element is 0.12. High-quality photographs with max. dept of field, allowing relatively large-size enlargements to be made, are achieved.