Abstract: A lens system comprises, in order from a first side to a second side four lens elements. They are: a first, positive power lens element having its convex surface oriented towards the first side; a second, negative power lens element; a third, meniscus lens element having its concave surface oriented towards the first side; and a fourth, meniscus lens element having its concave surface oriented towards the second side.

Abstract: A lens system has nominal focal length and aberrations and includes a plurality of lens components defined by design parameter values and a special airspace distance. The lens system is characterized in design such that manufacturing deviations from the design parameter values cause a variation from the nominal focal length and a variation in at least one of the aberrations. Both of these deviations can be offset simultaneously by a single change in the special airspace distance.

Abstract: A lens system particularly suitable for use in a camera using small format film has two lens units, a front negative power lens unit and a rear positive power lens unit. The rear lens unit has no negative lens elements and includes an aspheric surface and a diffractive surface.

Abstract: A cluster lens for imaging a transparency onto an image plane comprises a plurality of lenses which simultaneously have a field of view sufficient to include the transparency. All of the lenses image simultaneously. At least two of these lenses have different magnifications. The lenses are located in a spaced relationship to each other so that that not one of these lenses encroaches upon that section of the field of view of another lens that is used to image the transparency onto the image plane.

Abstract: An enlargement lens system with a large working distance comprising five lens components with a stop between the third and fourth components (numbered from the long conjugate side). It includes a first negative lens component, meniscus concave to the stop; a second positive lens component, having a convex surface toward the first lens component; a third and fourth lens component, both cemented negative doublets, meniscus concave to the stop; and a fifth positive power biconvex lens component, wherein BF/EF>1.0, where BF is the short conjugate back focus and EF is the focal length of the lens system.

Abstract: In order to reduce complexity and cost of fabrication of zoom lenses, the real image forming lens group module at the front of the zoom lens is replaced with a two-element group where one of the elements has a diffractive lens on a curved surface thereof instead of the usually cemented doublet of the front group, but with substantially the same aberrations as a front group with three elements, including a cemented doublet. Aberrations (chromatic and monochromatic) produced by the first and second groups remain corrected by the combination of these groups over the zoom range of the lens. A second group housing two-elements, one of which has a curved surface on which a diffractive lens is provided, may be also be used to replace the three-element second lens group and particularly the cemented doublet thereof.