Projection lens for high definition TV
AssigneeMatsushita Electric Industrial Co., Ltd.
InventorsYasuo Nakajima, Yoshiharu Yamamoto, Yoshitomi Nagaoka
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Abstract
A high definition projection lens for projecting on a screen an enlargement of an image appearing on a high resolution CRT is disclosed. The projection lens comprises a first lens having a positive optical power and a convex surface facing the screen, a meniscus second lens having a positive optical power, a third lens having bi-concave surfaces and a negative optical power, a fourth lens having a positive optical power, a fifth lens having bi-convex surfaces and a positive optical power, and a sixth lens having a negative power and an aspheric concave surface facing the fifth lens.
Claims15
A projection lens for projecting on a screen an enlargement of an image appearing on a cathode ray tube (CRT), comprising, successively in a direction from the screen end to the CRT end:
- a first lens having a positive optical power and a convex surface facing the screen;
- a second lens having a positive optical power and a meniscus shape;
- a third lens having a negative optical power and bi-concave surfaces;
- a fourth lens having a positive optical power;
- a fifth lens having a positive optical power and bi-convex surfaces;
- and a sixth lens having a negative optical power and an aspheric concave surface facing said fifth lens, wherein the projection lens satisfies the following condition:
- 2.5.ltoreq.f.sub.a /f.ltoreq.5
- 0.45.ltoreq.d.sub.8 /d.sub.10 .ltoreq.1.0
- .nu..sub.2 .gtoreq.50
- .nu..sub.3 .ltoreq.38
- where:
- f is a focal length of the overall projection lens system;
- f.sub.a is a combined focal length of the first, second and third lenses;
- d.sub.8 is a distance between the fourth and fifth lenses;
- d.sub.10 is a distance between the fifth and sixth lenses;
- and .nu..sub.2 and .nu..sub.3 are respectively Abbe numbers of the second and third lenses.
A high resolution projection lens for projecting on a screen an enlargement of an image of a resolution of more than 525 lines appearing on a high resolution cathode ray tube (CRT), comprising, successively in a direction from the screen end to the CRT end:
- a first lens of a positive optical power having a convex surface facing the screen;
- a second lens of a positive optical power having a meniscus shape;
- a third lens of a negative optical power having bi-concave surfaces;
- a fourth lens of a positive optical power;
- a fifth lens of a positive optical power having bi-convex surfaces;
- and a sixth lens of a negative optical power having an aspheric concave surface facing the fifth lens.
Dependencies are inferred from the claim text.