Patent
1984-10-18
1986-10-07
Corbin, John K.
350432, G02B 304, G02B 912
Patent
active
046155899
ABSTRACT:
A projection lens system for a projection television for projecting on a screen an enlargement of an image displayed on a cathode ray tube includes a first bi-aspherical lens of positive power, the surface of which is toward the end of the lens system which is to face the screen being a convex surface having a larger curvature than the other surface thereof, a second double convex lens of glass, and a third bi-aspherical lens of negative power, the surface of which is toward the screen end being a concave surface having a larger curvature than the other surface thereof, the first, second and third lens being disposed in the order from the screen end, and satisfying the conditions: 1.3f<f.sub.1 <1.9f; 0.9f<f.sub.2 <1.2f; 0.25f<d.sub.4 <0.35f; r.sub.1 <.vertline.r.sub.2 .vertline.; and 0.4<r.sub.3 /.vertline.r.sub.4 .vertline.<0.75, where f is the total focal length, f.sub.1 and f.sub.2 are the respective focal lengths of the first and second lenses, d.sub.4 is the distance between the second and third lens, and r.sub.1, r.sub.2, r.sub.3 and r.sub.4 are the respective radii of vertex curvatures of the first, second, third and fourth lens surfaces from the screen end.
REFERENCES:
patent: 4300817 (1981-11-01), Betensky
patent: 4348081 (1982-09-01), Betensky
patent: 4548480 (1985-10-01), Yamamoto et al.
Miyatake Yoshito
Yamamoto Yoshiharu
Corbin John K.
Gass Rebecca D.
Matsushita Electric - Industrial Co., Ltd.
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