1989-09-05
1990-10-16
Bovernick, Rodney B.
350412, 350477, G02B 1318, G02B 2718
Patent
active
049630075
ABSTRACT:
A projection lens in which a lens unit which may comprise one or two elements is closely coupled at the object end of the lens to a cathode ray tube. At the image end is a lens unit of overall weak optical power which comprises from the image end a first positive element followed by a closely spaced negative element of substantially higher dispersion. Intermediate the object side lens unit and the image side lens unit is a lens unit of substantial optical power supplying substantially all of the positive optical power of the lens. Closely spaced to this power lens unit on the object side is a negative lens element of high dispersion. This negative lens element may be considered to be part of the power lens unit. The negative lens elements have weak optical power at the axis of the lens but are of generally increasing negative optical power from the optical axis to the clear apertures of the negative lens elements to contribute to proper color correction of the lens, particularly axial chromatic aberration adjacent the full aperture. The intermediate positive power lens unit may comprise one or two positive elements depending upon the application and the manner in which the power is to be distributed to minimize aberrations. A lens embodying the invention is capable of maintaining a high image quality over a large range of magnifications by moving the first and second lens units form the image end in predetermined differential relationship.
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Lenses In Photography, pp. 131, 132, by Rudolph Kingslake, Garden City Books, Garden City, NY, Copyright 1951.
Bovernick Rodney B.
Gass Rebecca D.
Montgomery Robert H.
U.S. Precision Lens Inc.
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