Optical: systems and elements – Lens – With field curvature shaping
Patent
1993-03-15
1994-11-22
Sugarman, Scott J.
Optical: systems and elements
Lens
With field curvature shaping
359708, G02B 1318
Patent
active
053674057
ABSTRACT:
First, second, third, and fourth set lenses are located in this order from the direction of a screen. The first lens group comprises a plastic lens having a weak refracting power and at least one aspherical surface. The second lens group comprises a plastic lens having a weak refracting power and at least one aspherical surface, and an achromatic lens system having a substantial effect on the refracting power of the whole projecting lens. The achromatic lens system is composed of three or four glass lenses, and a plastic lens having a positive refracting power and at least one aspherical surface. The third lens group comprises a plastic lens having a weak refracting power and at least one aspherical surface. The fourth lens group comprises a plastic lens having at least one aspherical surface, and a field flattener lens, which is located with its concave surface facing the screen and which constitutes a liquid optical coupler. Special conditions are satisfied such that an unsharp state of a projected image due to an increase in temperature may be compensated for, and a wide variable power range may be obtained.
REFERENCES:
patent: 4900139 (1990-02-01), Kreitzer
patent: 5048940 (1991-09-01), Ueda et al.
patent: 5130850 (1992-07-01), Toide
patent: 5212597 (1993-05-01), Yamada
Fuji Photo Optical Co., Ltd.
Sugarman Scott J.
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