EP0039619A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Projection television apparatus having improved optical configuration
Assignee: Panasonic Holdings Corp
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Filing: 1981-05-06
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Granted: —
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Expires: 2001-05-06
Abstract
Abstract projection television apparatus comprises three monochromatic cathode-ray tubes (1R, 1G, 1B), two dichroic mirrors (6), and a lens (3). Red, green and blue images from three tubes are combined into the colour image by the two dichroic mirrors (6) and the resulting image is enlarged and projected on the screen by a single lens (3). The two dichroic mirrors (6) cross at a right angle to form the character «X» and each dichroic mirror is split in two sections (6R, 6R'; 6B, 6B') on the line of intersection with the other mirror; the two sections of each dichroic mirror (6R, 6R' and 6B, 6B') having different transmission characteristics so that colour shading is improved.
Inventors
- 👤 Yoshito Miyatake
- 👤 Yoshitomi Nagaoka
- 👤 Yasuo Nakajima
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-30 22:13
CPC Classifications
H; H04; H04N; H04N9/00; H04N9/12; H04N9/31
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
104 words
Projection television apparatus comprising: three cathode-ray tubes which display red, green and blue images respectively and which are placed at right angles to each other with adjacent faceplates close to each other; a lens placed on the optical axis of one of said three tubes; and two dichroic mirrors placed in the space formed by said faceplates for reflecting different colours along said optical axis to said lens, characterised in that at least one of said dichroic mirrors consists of two dichroic mirror sections which have different transmission characteristics from each other so as to minimize the difference of brightness ratios of respective colours.
Claim 2
Dependent Claim
104 words
Projection television apparatus comprising: three cathode-ray tubes which display red, green and blue images respectively and which are placed at right angles to each other with adjacent faceplates close to each other; a lens placed on the optical axis of one of said three tubes; and two dichroic mirrors placed in the space formed by said faceplates for reflecting different colours along said optical axis to said lens, characterised in that at least one of said dichroic mirrors consists of two dichroic mirror sections which have different transmission characteristics from each other so as to minimize the difference of brightness ratios of respective colours.
Claim 3
Dependent Claim
130 words
Projection television apparatus comprising: three cathode-ray tubes which display red, green and blue images respectively and which are placed relative to each other to form the letter "T" with their faceplates close to each other; two dichroic mirrors placed to cross like a character "X" in the space formed by said faceplates and intersecting to form the letter "X", which mirrors reflect different colours, and a lens which is placed on the optical axis of the centre tube of said three tubes, characterised in that at least one of said dichroic mirrors consists of two dichroic mirror sections which are separated through the line of intersection of the mirrors, and which have different transmission characteristics from each other so as to minimize the difference of brightness ratios of respective colours.
Claim 4
Dependent Claim
130 words
Projection television apparatus comprising: three cathode-ray tubes which display red, green and blue images respectively and which are placed relative to each other to form the letter "T" with their faceplates close to each other; two dichroic mirrors placed to cross like a character "X" in the space formed by said faceplates and intersecting to form the letter "X", which mirrors reflect different colours, and a lens which is placed on the optical axis of the centre tube of said three tubes, characterised in that at least one of said dichroic mirrors consists of two dichroic mirror sections which are separated through the line of intersection of the mirrors, and which have different transmission characteristics from each other so as to minimize the difference of brightness ratios of respective colours.
Claim 5
Dependent Claim
26 words
Projection television apparatus as claimed in claim 1 or 2, wherein said two dichroic mirror sections have different cutoff wavelengths at the same angle of incidence.
Claim 6
Dependent Claim
42 words
Projection television apparatus as claimed in claim 3, wherein said dichroic mirror section which is placed further from said lens has a longer cutoff wavelength at the same angle of incidence than said dichroic mirror section which is placed nearer said lens.
Claim 7
Dependent Claim
36 words
Projection television apparatus as claimed in any one of the preceding claims wherein said two dichroic mirror sections have different optimum angles of incidence so as to make the transmission coefficient maximum at a particular wavelength.
Claim 8
Dependent Claim
41 words
Projection television apparatus as claimed in claim 5, wherein said optimum angle of said dichroic mirror section which is placed further from said lens is greater than said optimum angle of said dichroic mirror section which is placed nearer said lens.
Claim 9
Dependent Claim
26 words
Projection television apparatus as claimed in any one of the preceding claims wherein both dichroic mirrors are separated through the line of intersection of the mirrors.
References Cited (Backward Citations)
US4027328A
Cited
US4151554A
Cited
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