Optical: systems and elements – Lens – With multipart element
Patent
1996-06-04
1998-06-16
Font, Frank G.
Optical: systems and elements
Lens
With multipart element
359741, G02B 920
Patent
active
057680329
ABSTRACT:
A large aperture projection lens is disclosed which contains a TESSAR lens set and a FRESNEL lens. The TESSAR lens set consists of four lenses which satisfy the conditions of: Nd1>1.7; Nd2>1.7; and 33<Ud2<35. Nd1 is the refractive idex of a first lens at the wavelength of 0.5876 um; Nd4 is the refractive idex of a fourth lens at the same wavelength; and Ud2 is the Abbe number of a second lens. The FRESNEL lens is provided such that the following relationship is observed: ##EQU1## where Ff is the focal distance of the FRESNEL lens and Ft is the focal distance of the TESSAR lens set. The projection lens satisfies the following requirements while allowing the aperture to be as high as F/2.4, (i) when a color image is projected, the color differential is smaller than 25 um; (ii) the ratio between the brightness at an edge of the image and the brightness at the center of is greater than 60%; (iii) the distortion is smaller than 1%; (iv) the resolution is greater than 50% at 4 lps/mm.
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Font Frank G.
Industrial Technology Research Institute
Liauh W. Wayne
Stafira Michael P.
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