Color corrected projection lens
AssigneeMatsushita Electric Industrial Co., Ltd.
InventorsYoshiharu Yamamoto, Yasuo Nakajima, Syusuke Ono
Life of this patent
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Abstract
A color corrected projection lens with a large aperture ratio and a wide angle of view for producing on a screen an enlargement of an image appearing on a CRT, the lens having sequentially from the screen end a first unit of a bi-convex element having a positive power with a strongly convex surface directed toward the screen end, a second unit of a bi-concave element having a negative power and being located at or in the vicinity of the entrance pupil position of the entire lens system, a third unit of a bi-convex element having a positive power, and a fourth unit having a negative power with a strongly concave surface directed toward the screen end.
Claims6
A color corrected projection lens for producing on a screen an enlargement of an image appearing on a cathode-ray tube (CRT), comprising, sequentially from the screen end:
- a first unit for correcting spherical aberration, coma and distortion, which is made of bi-convex element having a positive power at least one surface of which is an aspheric surface, the surface of said first unit directed toward the screen end being strongly convex;
- a seond unit for mainly correcting longitudinal chromatic abberation, which i made of a bi-concave element having a negative power and disposed at or in the vicinity of an entrance pupil position of said lens;
- a third unit for correcting astigmatism and distortion, which is made of a bi-convex element having a positive power;
- and
- a fourth unit having a negative power and having a concave surface directed toward the screen end which is strongly concave, at least said strongly concave surface of said fourth unit being an aspheric surface.
Dependencies are inferred from the claim text.