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US4976525A Expired / Lapsed US ⏱️ 0.0 years remaining

Projection lens system for projectors

Assignee: Fujinon Corp
•
Filing: 1989-12-20
•
Granted: 1990-12-11
•
Expires: 2009-12-20
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Abstract

Abstract Described herein is a projection lens system, comprising from the screen side a positive first lens unit of weak power consisting of a plastic meniscus, a positive or negative second lens unit of weak power consisting of a plastic lens element, third and fourth lens units in the form of a cemented glass lens having a positive combined focal length, a positive fifth lens unit of strong power, a positive sixth lens unit of weak power consisting of a plastic lens element, and a negative seventh lens unit having a concave surface on the screen side, each of the first, second, sixth and seventh lens units having at least an aspheric surface, and arranged to satisfy the following conditions 0.08<f/f.sub.1 <0.18 and (1) 0.01<|f/f.sub.2 |<0.1 (2) where f 1 and f 2 are focal lengths of the first and second lens units and f is the overall focal length of the projection lens system as a whole.

Inventors

  • 👤 Takeshi Matsumura
  • 👤 Noboru Koizumi

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-11-01 04:42
CPC Classifications
G; G02; G02B; G02B13/00; G02B13/18; G02B13/16

Claims Analysis

Total Claims: 4
Claim 1
Independent Claim 151 words
A projection lens system, comprising from a screen side a positive first lens unit of weak power consisting of a plastic meniscus, a second lens unit of weak power consisting of a plastic lens element, third and fourth lens units in the form of a cemented glass lens having a positive combined focal length, a positive fifth lens unit of strong power, a positive sixth lens unit of weak power consisting of a plastic lens element, and a negative seventh lens unit having a concave surface on the screen side, each of said first, second, sixth and seventh lens units having at least an aspheric surface, and arranged to satisfy the following conditions 0.08<f/f.sub.1 <0.18 and (1) 0.01<|f/f.sub.2 |<0.1 (2) where f 1 and f 2 are focal lengths of said first and second lens units and f is the overall focal length of said projection lens system as a whole.
Claim 2
Dependent Claim 151 words
A projection lens system, comprising from a screen side a positive first lens unit of weak power consisting of a plastic meniscus, a second lens unit of weak power consisting of a plastic lens element, third and fourth lens units in the form of a cemented glass lens having a positive combined focal length, a positive fifth lens unit of strong power, a positive sixth lens unit of weak power consisting of a plastic lens element, and a negative seventh lens unit having a concave surface on the screen side, each of said first, second, sixth and seventh lens units having at least an aspheric surface, and arranged to satisfy the following conditions 0.08<f/f.sub.1 <0.18 and (1) 0.01<|f/f.sub.2 |<0.1 (2) where f 1 and f 2 are focal lengths of said first and second lens units and f is the overall focal length of said projection lens system as a whole.
Claim 3
Dependent Claim 65 words
A projection lens system as defined in claim 1, further satisfying the condition of 0.3<d.sub.1+2+3+4 /d<0.4 (3) d 1+2+3+4 is the sum of on-axis spacings between the screen side surfaces of said first and third lens units and d is the sum of on-axis spacings between the screen side surface of said first lens unit and a CRT side surface of said seventh lens unit.
Claim 4
Dependent Claim 26 words
A projection lens system as defined in claim 1 or 2, wherein said lens units are supported by a lens barrel of a synthetic resin material.

References Cited (Backward Citations)

US4778264A Cited
US4761063A Cited
US4900139A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1993-12-10 1994-06-11 1994-12-11 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1997-12-10 1998-06-11 1998-12-11 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 2001-12-10 2002-06-11 2002-12-11 $7700.00 Window Closed / Lapsed

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