LIGHTING SYSTEM
First Claim
Patent Images
1. A lighting system comprising:
- a housing, a primary light source, a concave mirror for producing a secondary light source in the form of a virtual image of the said primary light source substantially spaced from said primary light source, said mirror being coated with a light-reflecting and heattransmitting material, a projection lens having its rear focal point substantially in a plane containing said virtual image for projecting a beam of light energy radiated by said secondary light source, said lens being substantially ineffective in projecting light energy radiated from said primary light source, said concave mirror, primary light source and projection lens being centered, respectively one behind another on a common optical axis within the said housing, and wherein the said light-reflecting and heat-transmitting material reflects only a minor proportion of the infrared energy radiated by said primary light source.
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Abstract
A lighting system has a generally hyperboloidal mirror having a light-reflecting and heat-transmitting coating to form a virtual image of a light source and a lens to project a beam of light of depleted heat content, the virtual image acting as the source of the light projected by the lens.
12 Citations
10 Claims
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1. A lighting system comprising:
- a housing, a primary light source, a concave mirror for producing a secondary light source in the form of a virtual image of the said primary light source substantially spaced from said primary light source, said mirror being coated with a light-reflecting and heattransmitting material, a projection lens having its rear focal point substantially in a plane containing said virtual image for projecting a beam of light energy radiated by said secondary light source, said lens being substantially ineffective in projecting light energy radiated from said primary light source, said concave mirror, primary light source and projection lens being centered, respectively one behind another on a common optical axis within the said housing, and wherein the said light-reflecting and heat-transmitting material reflects only a minor proportion of the infrared energy radiated by said primary light source.
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2. A lighting system as claimed in claim 1, wherein said concave mirror has a generally hyperboloidal reflecting surface.
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3. A lighting system as claimed in claim 1, wherein said projection lens is of the Fresnel lens.
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4. A lighting system as claimed in claim 1, including a mounting carrying both said primary light source and said concave mirror, the said primary light source being located in fixed relationship with and in front of said concave mirror.
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5. A lighting system as claimed in claim 4, wherein said mounting is movable towards and away from said projection lens to vary the position of said virtual image about one focal point of said projection lens so as to adjust the divergence of the light beam projected, means for controlling the position of said mounting being provided, which means are operable from the exterior of the housing.
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6. A lighting system as claimed in claim 5, wherein said means comprise a lead screw journalled on said housing which engages a correspondingly threaded bore in said mounting.
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7. A lighting system as claimed in claim 1, further including a dichroic filter to reflect infrared energy away from the direction in which said beam of light is projected.
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8. A lighting system as claimed in claim 7, wherein said dichroic filter is disposed on a light-transparent plate, said plate being located in the beam of light projected by said projection lens.
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9. A lighting system as claimed in claim 7, wherein said dichroic filter is disposed on said projection lens.
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10. A lighting system according to claim 1, wherein said primary light source is a tungsten-halogen lamp, said concave mirror is a generally hyperboloidal mirror, on the reflecting surface of which is disposed a light-reflecting and heat-transmitting coating, to produce a secondary light source in the form of a virtual image of said tungsten-halogen primary source, said projection lens which projects the beam of light energy radiated by said secondary light source is a Fresnel lens, said hyperboloidal mirror, tungsten-halogen primary source and said Fresnel lens being centered, one behind another on a common optical axis within said housing, the tungsten-halogen primary source and said hyperboloidal mirror being mounted in fixed spatial relationship on a common support movable along said optical axis towards and away from said Fresnel lens, means for controlling the position of said support relative to said Fresnel lens, said means comprising a screw-threaded bar entering said housing and rotatably mounted heRein, the screw threads of said bar engaging a correspondingly screw-threaded bore in said support, the said light-reflecting and heat-transmitting coating disposed on said hyperboloidal mirror reflecting only a minor proportion of the infrared energy radiated by said tungsten-halogen primary source.
Specification