1985-06-20
1987-07-28
Corbin, John K.
G02B 934, G02B 1318
Patent
active
046828613
ABSTRACT:
A projection lens for enlarging and projecting a television image on a screen including: a first lens L1 having a positive refracting power; a second lens L2 having a positive refracting power and a convex surface which is located at the side of L2 nearer to the image and which has a larger curvature than that at the side of L2 nearer to the screen; a third lens L3 which consists of a meniscus lens having a concave surface located at the side of L3 nearer to the image; and a fourth lens L4 having a concave surface which is located at the side of L4 nearer to the screen and which has a larger curvature than that at the side of L4 nearer to the image. The lenses L1, L2, L3 and L4 are arranged from the side of the screen in the order named. The combined refracting power of the second and third lenses is larger than that of the first lens. At least one nonspherical surface is provided in the first lens, and at least one nonspherical surface is provided in the second, third and fourth lenses.
REFERENCES:
patent: 3868173 (1975-02-01), Miles et al.
patent: 4300817 (1981-11-01), Betensky
patent: 4348081 (1982-09-01), Betensky
patent: 4526442 (1985-07-01), Betensky
Canon Kabushiki Kaisha
Corbin John K.
Gass Rebecca D.
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