1985-12-10
1987-10-13
Corbin, John K.
350412, 350473, G02B 1318, G02B 934
Patent
active
046994769
ABSTRACT:
A lens system is provided which is suitable for back-projecting an enlarged image of a TV cathode ray tube (CRT). To achieve a compact cabinet design 1 for such a projection television set, a short projection throw and a wide projection angle are required, together with a wide aperture (F/1) for a bright projected picture and with a definition which may need to be good enough to resolve 1249 line television pictures. The lens system comprises a CRT face plate FP which is either flat or has a relatively shallow curavature on one or both sides and four lens elements L1, L2, L3 and L4. L1 is a weak lens, L2 and L3 are each of positive power and L4 is a negative element close to the CRT. At least two of the element surfaces are aspheric. The powers of the elements are chosen so that
REFERENCES:
patent: 4577935 (1986-03-01), Yamakawa et al.
patent: 4603950 (1986-08-01), Uehara et al.
Corbin John K.
Faller F. Brice
Gass Rebecca D.
U.S. Philips Corporation
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