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US 4,398,810 AGranted
Fresnel lens system
AssigneeB Optical
InventorsMarvin P. Hodges, Richard A. Buchroeder
Life of this patent
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Abstract
A projection lens system of the type used in connection with cathode ray tubes, and more specifically a cathode ray tube projection system having an internal lens folding means, useful in projecting an image or series of images on a screen.
Claims11
A Fresnel lens system having design parameters normalized for a 280 mm focal length represented by the following table:
- ______________________________________ Ele- Sepa- ment R D E F ration ______________________________________ A -364.848 +0.779 .times. -0.1990 .times. +0.2300 .times. mm 10.sup.-8 mm.sup.-3 10.sup.-12 mm.sup.-5 10.sup.-17 mm.sup.-7 280.6mm (nominal) B -269.834 +0.3539 .times. -0.118 .times. +0.5003 .times. mm 10.sup.-7 mm.sup.-3 10.sup.-11 mm.sup.-5 10.sup.-16 mm.sup.-7 119.8mm (nominal) C -142.473 +0.1322 .times. -0.6375 .times. +0.4502 .times. mm 10.sup.-7 mm.sup.-3 10.sup.-5 mm.sup.-5 10.sup.-17 mm.sup.-7 ______________________________________
- wherein letters A through C identify the respective lens elements from the screen side to the cathode ray tube side and R, D, E, and F are constants of the following generating function:
- x=y.sup.2 /2R+Dy.sup.4 +Ey.sup.6 +Fy.sup.8
- where y is the zonal ray distance from the optical axis, and wherein and the slope of the generating function given as a tangent, is defined as:
- tan .theta.=y/R+4Dy.sup.3 +6Ey.sup.5 +8Fy.sup.7
- with all dimensions being expressed in millimeters, and wherein the design parameters may be normalized to any other focal length, lengths and lens materials.
3 more elements
Dependencies are inferred from the claim text.