Projection lens systems having reduced spherochromatism
First Claim
Patent Images
1. A projection lens system for use with a cathode ray tube comprising in order from the system'"'"'s image side:
- (a) a first lens unit comprising in order from the lens system'"'"'s image side;
(i) a first lens element having a positive power on axis and at least one aspheric surface which causes said positive power to become negative in the vicinity of the lens element'"'"'s clear aperture; and
(ii) a second lens element of weak optical power;
(b) a second lens unit which comprises a third lens element which provides the majority of the lens system'"'"'s positive optical power, the dispersion of the first lens element being greater than the dispersion of the third lens element and being greater than the dispersion of all other lens elements, if any, of the second lens unit; and
(c) a third lens unit of negative power 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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Abstract
A projection lens system for projecting an image from a cathode ray tube (CRT) onto a screen is provided. The spherochromatic aberration of the system is reduced through the use of a first lens element which has (i) a positive power on axis and at least one aspheric surface which causes the positive power to become negative in the vicinity of the lens element'"'"'s clear aperture, and (ii) a high dispersion. The first lens element is preferably composed of styrene.
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Citations
35 Claims
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1. A projection lens system for use with a cathode ray tube comprising in order from the system'"'"'s image side:
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(a) a first lens unit comprising in order from the lens system'"'"'s image side; (i) a first lens element having a positive power on axis and at least one aspheric surface which causes said positive power to become negative in the vicinity of the lens element'"'"'s clear aperture; and (ii) a second lens element of weak optical power; (b) a second lens unit which comprises a third lens element which provides the majority of the lens system'"'"'s positive optical power, the dispersion of the first lens element being greater than the dispersion of the third lens element and being greater than the dispersion of all other lens elements, if any, of the second lens unit; and (c) a third lens unit of negative power 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 28, 29)
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10. A projection lens system for use with a cathode ray tube comprising in order from the system'"'"'s image side:
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(a) a first lens unit having a first lens element at its image side which has a positive power on axis and at least one aspheric surface which causes said positive power to become negative in the vicinity of the lens element'"'"'s clear aperture; (b) a second lens unit which comprises a power subunit, said power subunit providing the majority of the lens system'"'"'s positive optical power and comprising at least one lens element, the dispersion of said first lens element being greater than the dispersion of the element or elements comprising the power subunit and being greater than the dispersion of all other lens elements, if any, of the second lens unit; and (c) a third lens unit of negative power 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. - View Dependent Claims (11, 12, 13, 14, 15, 16, 30, 31)
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17. A projection lens system for use with a cathode ray tube comprising in order from the system'"'"'s image side:
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(a) a first lens unit comprising in order from the lens system'"'"'s image side; (i) a first lens element composed of styrene and having a positive power on axis and at least one aspheric surface which causes said positive power to become negative in the vicinity of the lens element'"'"'s clear aperture; and (ii) a second lens element composed of an acrylic material; (b) a second lens unit comprising a positive lens element composed of a low dispersion glass, the dispersion of said low dispersion glass being less than the dispersion of styrene and the dispersion of all other lens elements, if any, of the second lens unit being less than the dispersion of styrene; (c) a corrector lens unit comprising two lens elements, each composed of an acrylic material; and (d) a third lens unit of negative power which is associated with the cathode ray tube during use of the lens system, said third lens unit comprising a lens element composed of an acrylic material. - View Dependent Claims (18, 19, 20, 21, 32, 33)
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22. A projection lens system for use with a cathode ray tube comprising in order from the system'"'"'s image side:
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(a) a first lens unit having a first lens element at its image side composed of a high dispersion plastic material; (b) a second lens unit for providing the majority of the lens system'"'"'s positive optical power, said second lens unit comprising one or more lens elements, the dispersion of said first lens element being greater than the dispersion of the element or elements comprising the second lens unit; and (c) a third lens unit of negative power 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. - View Dependent Claims (23, 24, 25, 26, 27, 34, 35)
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Specification