GB1130784A - Fresnel lens - Google Patents

Abstract

1,130,784. Fresnal lenses. CARL ZEISS JENA VEB. June 1, 1966, No.24354/66. Heading G2J. A Fresnal lens having a series of echelons such as F, Fig. 1, on both its optically active faces for producing an aberrationless image of any two points on its optical axis X 1 X 1 has the meridional curve of each of its optically active faces such as G defined by:- wherein: - h = height of the beam incident on the Fresnel face, n = refractive index in the object space, n<SP>1</SP> = refractive index in the image space, #s = distance apart of object points on the optical axis, #s<SP>1</SP> = distance apart of image points on the optical axis, α<SP>1</SP> = longitudinal magnification =#S<SP>1</SP>/#S e = angle of the beam incident on the Fresnel face, #<SP>1</SP> = angle of refraction on the Fresnel face, # = object - side aperture angle, #<SP>1</SP> = image - side aperture angle, and Á = inclination of the active flanks W of the Fresnel echelons. The face may contain either the vertices or the bases of the Fresnel echelons. For the active flanks W the following holds good: - When the lens is used for imaging two neighbouring points on the optical axis the meridional curve is given by :- S<SP>12</SP> sin<SP>2</SP> #<SP>1</SP> cos<SP>1</SP> = S<SP>2</SP> sin<SP>2</SP> # cos # where: - s = object - side intercept, and S<SP>1</SP> = image - side intercept. In such a case there may be Fresnel echelons on one face only, Fig.3, (not shown) the other face being spherical and concentric with either an object or an image point.