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Lens systems for projection televisions

  • US 7,019,793 B2
  • Filed: 08/03/2004
  • Issued: 03/28/2006
  • Est. Priority Date: 11/09/2000
  • Status: Expired due to Fees
First Claim
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1. A projection lens system for use in a projection television which has a screen and a first cathode ray tube which produces light of primarily a first color, a second cathode ray tube which produces light of primarily a second color, and a third cathode ray tube which produces tight of primarily a third color, said projection lens system comprising three projection lenses, one projection lens being associated with each of the cathode ray tubes during use of the system for forming an image of the light produced by that tube on the screen, each projection lens consisting of:

  • (A) a first lens unit on the long conjugate side of the lens, said first lens unit having a positive power and comprising, in order from the long conjugate side of the unit, a first lens element composed of plastic, a second lens element composed of glass, and a third lens element composed of plastic; and

    (B) a second lens unit which (i) is associated with a cathode ray tube during use of the lens, (ii) has a strong negative power when so associated, (iii) provides most of the correction of the lens'"'"' field curvature, and (iv) comprises a plastic lens element;

    wherein in addition to any difference based on satisfying the Scheimpflug condition or any difference in spectral transmission, the second lens unit of the second projection lens differs from the second lens unit of the first projection lens in at least one optical property, said difference being based on said first and second colors.

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