A beam splitting prism assembly in which at least some of the prisms are separated by an air gap, optionally connected at the edges through the beam splitting layers by means of strips of a thermo-plastic material.
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1. A beam splitting prism assembly comprising a plurality of prisms having surfaces separated by an air gap, the edges of the prism surfaces bounding the air-gap being provided with a small strip at the glass prism surfaces, said strip comprising an adhering film of a thermoplastic material located thereon forming a beam splitting layer.
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The invention relates to a colour splitting prism assembly for colour television cameras which splits the incident light in such a camera into a plurality of beams of different spectral compositions intended for the pick-up tubes of the camera.
Essentially such a camera comprises three pick-up tubes for the colour components of the different spectral compositions, and a prism arrangement which ensures splitting which is a combination of a plurality of prisms, for example three in number.
The positioning of the prisms relative to one another must be done very accurately and furthermore some prisms must be separated from one another by means of a very narrow air gap, of, for example, 15 microns.
According to United Kingdom patent specification No. 1,206,461 a beam splitting prism assembly is proposed for a colour television camera including adjacent prism surfaces, in which the air gaps are adjusted by means of metallic wire which is compressed between said surfaces at the edges, said wire being capable when compressed of distorting and adhering to the surfaces. A suitable metal is indium which is applied in the form of an open ring, the ends of which are overlapped.
In practice this assembly was not very satisfactory. The glass-to-indium transitions entail annoying reflections.
The assemblies whose strength and resistivity against shocks are not very large are in the long run still further affected by atmospheric influences. The minimum spacing of the prisms having such an indium spacer is not less than 30 microns which is rather large in practice.
Finally the method of producing such a composite prism is not simple.
The invention now provides a beam splitting assembly consisting of glass prisms, in which some of the at least one air-gap, air-gaps 1 and an interface 2. Prism C, as shown in more detail in FIG. 2 has a surface 3 bounding the air-gap 1 which is provided with a polyethylene strips S.
The ray paths through the prism assembly are shown in FIG. 1. An incident ray i passes through prisms A and B and emerges from prism C as ray r3. Part of the incident ray is reflected at the air-gaps 1 and 2 and emerges from prism B as r2 while a portion of the incident ray is reflected at the air-gap 1 2 and emerges from A as r1.
Stoffels, Jacobus, Peters, Petrus J. M., de Haan, administrator, by Friedrich J., Bleukens, deceased, Adrianus A. J.
| Patent | Priority | Assignee | Title |
| 4504123, | Oct 05 1981 | Raytheon Company | High efficiency polarizing beamsplitter |
| 4890899, | May 18 1987 | Matsushita Electric Industrial Co., Ltd. | Color separation optical system which utilizes glass frit for bonding |
| 4913528, | May 30 1987 | Pioneer Electronic Corporation | Optical prism, and projection television set using same |
| 6377409, | Dec 04 1996 | Asahi Kogaku Kogyo Kabushiki Kaisha | Prism and viewing optical system using the prism |
| 6704145, | Sep 04 2002 | RAYTHEON CANADA LIMITED | Air-gap optical structure having the air gap defined by a layered spacer structure |
| 7505208, | Feb 06 2006 | RAYTHEON CANADA LIMITED | Air-gap optical structure with a nonreflective air-gap spacer |
| Patent | Priority | Assignee | Title |
| GB1206461, |
| Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
| Sep 24 1979 | U.S. Philips Corporation | (assignment on the face of the patent) | / |
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