US4453178A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Projection television apparatus
Assignee: Panasonic Holdings Corp
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Filing: 1981-12-16
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Granted: 1984-06-05
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Expires: 2001-12-16
Abstract
Abstract A projection television apparatus having a retrofocus type projection lens system which has a sufficiently long back focus, a small F number and a large distortion. The lens system is constructed with five components and five lenses and comprises a first lens which is a negative meniscus lens that has at its screen side a convex surface, a second lens which is a biconvex lens, a third lens which is a biconcave lens, a fourth lens which is a positive lens, and a fifth lens which is a biconvex lens, and which is defined by the following four conditions, i.e. 1.4f<|f.sub.1 |<1.9f (i) 0.35f<d.sub.2 <0.55f (ii) 0.8f<r.sub.3 <1.2f (iii) 0.15f<d.sub.4 <0.35f (iv) where f is the composite focal length of the total lens system, f 1 is the focal length of the first lens, d 2 is the air space between the first lens and the second lens, d 4 is the air space between the second lens and the third lens, and r 3 is the radius of curvature of the screen side surface of the second lens.
Inventors
- 👤 Yoshito Miyatake
- 👤 Yoshitomi Nagaoka
- 👤 Yasuo Nakajima
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 13:32
CPC Classifications
G; G02; G02B; G02B9/00; G02B9/60; H; H04; H04N; H04N9/00; H04N9/12; H04N9/31
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
51 words
A projection television apparatus comprising: an image producing means for producing a picture image which is to be projected; a screen; and a retrofocus lens means between said image producing means and said screen for enlarging said image from said image producing means and projecting the enlarged image on said screen.
Claim 2
Dependent Claim
51 words
A projection television apparatus comprising: an image producing means for producing a picture image which is to be projected; a screen; and a retrofocus lens means between said image producing means and said screen for enlarging said image from said image producing means and projecting the enlarged image on said screen.
Claim 3
Dependent Claim
23 words
A projection television apparatus according to claim 1, wherein said image producing means comprises a cathode-ray tube for displaying said picture image thereon.
Claim 4
Dependent Claim
67 words
A projection television apparatus according to claim 1, wherein said image producing means comprises: two monochromatic cathode-ray tubes for displaying thereon color images, respectively; and a mirror block positioned for receiving said color images from said cathode-ray tubes and combining them into said picture image and directing said image into said retrofocus lens means, said retrofocus lens means having a back focus longer than said mirror block.
Claim 5
Dependent Claim
70 words
A projection television apparatus according to claim 1, wherein said image producing means comprises: three monochromatic cathode-ray tubes for displaying thereon red, green and blue color images, respectively; a mirror block positioned for receiving said color images from said cathode-ray tubes and combining them into said picture image and directing said image into said retrofocus lens means, said retrofocus lens means having a back focus longer than said mirror block.
Claim 6
Dependent Claim
106 words
A projection television apparatus according to claim 4, wherein said cathode-ray tubes are placed so that two of the cathode-ray tubes share a center normal line which intersects the center normal line of the other cathode-ray tube at right angles, the face-plates of the three cathode-ray tubes being the same distance from the intersection of the center normal lines, and said mirror block comprises two dichroic mirrors intersecting at the center thereof, the center-point of said dichroic mirrors being at the intersection of the center normal lines of the cathode-ray tubes, and the dichroic mirrors being at a 45° angle with respect to each cathode-ray tube.
Claim 7
Dependent Claim
38 words
A projection television apparatus according to claim 1 or 2 or 3 or 4 or 5, wherein the distortion on the tube side of said retrofocus lens means at the maximum field angle is from -5% to -20%.
Claim 8
Dependent Claim
19 words
A projection television apparatus according to claim 6, wherein the characteristic curve of said distortion has no inflection point.
Claim 9
Dependent Claim
76 words
A projection television apparatus according to claim 1, wherein said retrofocus lens means comprises five components and five lenses composed of, from the screen side, a first lens which is a negative meniscus lens the screen side of which is a convex surface, a second lens which is a biconvex lens, a third lens which is a biconcave lens, a fourth lens which is a positive lens, and a fifth lens which is a biconvex lens.
Claim 10
Dependent Claim
95 words
A projection television apparatus according to claim 8, wherein said retrofocus lens means satisfies the following conditions: 1.4f<|f.sub.1 |<1.9f (i) 0.35f<d.sub.2 <0.55f (ii) 0.8f<r.sub.3 <1.2f (iii) 0.15f<d.sub.4 <0.35f (iv) where f is the composite focal length of the lens system, f 1 is the local length of said first lens, d 2 is the air space between said first lens and said second lens, d 4 is the air gap between said second lens and said third lens, and ν 3 is the radius of curvature of the screen side surface of said second lens.
References Cited (Backward Citations)
US2642487A
Cited
US3328111A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-06-05 | 1987-12-05 | 1988-06-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-06-05 | 1991-12-05 | 1992-06-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-06-05 | 1995-12-05 | 1996-06-05 | $7700.00 | Window Closed / Lapsed |