High speed wide angle projection TV lens system
First Claim
1. A projection lens system for use with a cathode ray tube comprising in order from the image side a first weak meniscus aspherical element which is convex to the image, a second weak meniscus aspherical element which is concave to the image, a strong positive element which provides a majority of the power of the lens, a third weak aspherical meniscus element which is convex to the image, a fourth weak aspherical meniscus element which is concave to the image and a strong negative unit which is associated with the cathode ray tube during use of the lens system and which provides most of the correction for the field curvature of the lens system.
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Accused Products
Abstract
Projection lens systems for use in projection televisions are provided. The lens systems include a strong positive element which provides a majority of the power of the lens, a strong negative unit which provides most of the correction for the field curvature of the lens system, and four weak meniscus aspherical elements, two on each side of the positive element. By means of this arrangement, the lens system achieves a semi-field of view of approximately 40° at a f-number of about 1.0 or less. The lens systems are used to minimize the size of projection television sets since their semi-field of view of approximately 40° substantially matches the maximum numerical aperture of about 0.65 of projection screens used in such sets.
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Citations
14 Claims
- 1. A projection lens system for use with a cathode ray tube comprising in order from the image side a first weak meniscus aspherical element which is convex to the image, a second weak meniscus aspherical element which is concave to the image, a strong positive element which provides a majority of the power of the lens, a third weak aspherical meniscus element which is convex to the image, a fourth weak aspherical meniscus element which is concave to the image and a strong negative unit which is associated with the cathode ray tube during use of the lens system and which provides most of the correction for the field curvature of the lens system.
- 9. A projection television set comprising a cathode ray tube, a screen, and a projection lens system for projecting light from the cathode ray tube onto the screen to form an image, said projection lens system having a long conjugate in the direction of the screen and a short conjugate in the direction of the cathode ray tube, said projection lens system comprising from the long conjugate a first weak meniscus aspherical element which is convex to the long conjugate, a second weak meniscus aspherical element which is concave to the long conjugate, a strong positive element which provides a majority of the power of the lens, a third weak aspherical meniscus element which is convex to the long conjugate, a fourth weak aspherical meniscus element which is concave to the long conjugate and a strong negative unit which is associated with the cathode ray tube and provides most of the correction for the field curvature of the lens system.
Specification