US3900726A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Compact follow spot
Assignee: BERKEY COLORTRAN
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Filing: 1974-04-25
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Granted: 1975-08-19
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Expires: 1994-04-25
Abstract
Abstract A theatrical follow spot utilizes elliptic reflective optics to achieve compact size and non-astigmatic projection. A source lamp is situated in front of the mirror, sufficiently offset to one side thereof so as to be out of the path of reflected light. The mirror has the shape of an ellipsoid of revolution, the mirror section being entirely on one side of a meridian plane of the ellipsoid. The axis of light from the source lamp is coincident with a line through the near focus of the ellipsoid and the center of the mirror. This insures that an image in the near focal plane, such as the circular opening of an iris, will be projected at the distant focal plane of the ellipsoid, without distortion of shape.
Inventors
- 👤 Clyde L Tichenor
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 23:18
CPC Classifications
F; F21; F21V; F21V14/00; F21V14/02; F21V14/04; F21V14/06; F21V21/00; F21V21/14; F21V21/30; F21W; F21W2131/00; F21W2131/40; F21W2131/406
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
164 words
A compact follow spotlight comprising: a housing having one end that is optically transparent, an elliptic mirror mounted within said housing near the other end thereof, the reflecting surface of said mirror comprising a section of an ellipsoid of revolution, said section being offset to one side of a meridian plane including the axis of revolution of said ellipsoid, and a light source mounted within said housing near said one end remote from the near focus of said ellipsoid of revolution and offset to one side thereof so as to be substantially out of the path of light reflected from said mirror, said light source being arranged to project light past an object to be imaged placed at the near focus of said ellipsoid of revolution and toward said mirror, light from said source being reflected by said mirror through said transparent end and focused by said elliptic mirror in a distant focal plane coinciding with the far focus of said ellipsoid of revolution.
Claim 2
Dependent Claim
164 words
A compact follow spotlight comprising: a housing having one end that is optically transparent, an elliptic mirror mounted within said housing near the other end thereof, the reflecting surface of said mirror comprising a section of an ellipsoid of revolution, said section being offset to one side of a meridian plane including the axis of revolution of said ellipsoid, and a light source mounted within said housing near said one end remote from the near focus of said ellipsoid of revolution and offset to one side thereof so as to be substantially out of the path of light reflected from said mirror, said light source being arranged to project light past an object to be imaged placed at the near focus of said ellipsoid of revolution and toward said mirror, light from said source being reflected by said mirror through said transparent end and focused by said elliptic mirror in a distant focal plane coinciding with the far focus of said ellipsoid of revolution.
Claim 3
Dependent Claim
57 words
A follow spotlight according to claim 1 wherein said light source comprises a lamp and an associated reflector for projecting a beam of light toward said elliptic mirror, the central axis of the light beam from said lamp passing through the near focus of said ellipsoid of revolution and impinging on said mirror near the center thereof.
Claim 4
Dependent Claim
31 words
A follow spotlight according to claim 1, wherein said object to be imaged comprises an iris interposed in the light path between said source and said mirror at said near focus.
Claim 5
Dependent Claim
59 words
A follow spotlight according to claim 2 wherein said mirror is angularly oriented within said housing so that the peripheral point of said mirror section nearest said ellipsoid axis of revolution is in a plane including said near focus and the central axis of light reflected from said mirror, on the same side of said housing as said source.
Claim 6
Dependent Claim
31 words
A follow spotlight according to claim 2 wherein said mirror section subtends an angle of about twice the angle between said light beam central axis and said ellipsoid axis of revolution.
Claim 7
Dependent Claim
43 words
A follow spotlight according to claim 1, wherein said mirror is mounted for limited linear movement, without rotation, parallel to a normal through the center of said mirror, said limited movement permitting adjustment of the focus of said spotlight for different throw distance.
Claim 8
Dependent Claim
40 words
A follow spotlight according to claim 2, wherein said mirror is mounted for limited linear movement, without rotation, parallel to said light beam central axis, said limited movement permitting adjustment of the focus of said spotlight for different throw distance.
Claim 9
Dependent Claim
69 words
A follow spotlight according to claim 2 wherein said lamp-associated reflector is elliptic, and wherein said light source includes an annular reflector at the open end of said lamp-associated reflector for limiting the size of said light beam so that said beam is completely encompassed by said mirror, and further comprising a pattern mask interposable in said light beam adjacent the near focal plane of said ellipsoid of revolution
Claim 10
Dependent Claim
78 words
A follow spotlight according to claim 8 further comprising a mounting for said housing that permits both vertical and axial pivoting of said housing, and wherein said housing one end is open and said light source is mounted near the bottom of said housing open end, so that when the housing one end is pivoted downward, heat from said lamp will rise through said annular reflector and through said open end to accomplish draft ventilation of said lamp.
Claim 11
Dependent Claim
34 words
A follow spotlight according to claim 2 further comprising a flood or spread lens interposed in the light path between said source and said mirror to increase the effective magnification of the spotlight image.
Claim 12
Dependent Claim
121 words
A light projection system comprising: an elliptic reflector, the reflective surface of which is a section of an ellipsoid of revolution on one side of a meridian plane of said ellipsoid, and a light source situated in front of said reflector and remote from the near focus thereof for directing a beam of light onto said reflector through said near focus, said reflector thereby projecting an image, focused in the remote focal plane of said ellipsoid, of an object situated in the path of said beam at the near focal plane of said ellipsoid, said light source being offset to one side of said reflector so as to be substantially out of the path of light reflected from said elliptic reflector.
Claim 13
Dependent Claim
121 words
A light projection system comprising: an elliptic reflector, the reflective surface of which is a section of an ellipsoid of revolution on one side of a meridian plane of said ellipsoid, and a light source situated in front of said reflector and remote from the near focus thereof for directing a beam of light onto said reflector through said near focus, said reflector thereby projecting an image, focused in the remote focal plane of said ellipsoid, of an object situated in the path of said beam at the near focal plane of said ellipsoid, said light source being offset to one side of said reflector so as to be substantially out of the path of light reflected from said elliptic reflector.
Claim 14
Dependent Claim
42 words
A theatrical follow spot comprising the light projection system according to claim 11 together with a pivotally mounted housing containing said light projection system and an iris situated in the path of said beam at said near focal plane of said ellipsoid.
Claim 15
Dependent Claim
30 words
A follow spot according to claim 11 wherein said reflective surface is the front surface of said reflector, said light projecting system thus being characterized by a single reflective surface.
Claim 16
Dependent Claim
148 words
A light projection system comprising an elongated housing having one open end, an ellipsoidal mirror mounted within said housing opposite said open end, the reflecting surface of said mirror comprising a section of an ellipsoid of revolution, said section being offset to one side of a meridian plane including the axis of revolution of said ellipsoid, light source means comprising an elliptical reflector for projecting a beam of light, means for mounting said light source means within said elongated housing adjacent said open end, offset to one side thereof and remote from the near focus of said ellipsoidal mirror so as to direct said beam of light through said near focus onto said ellipsoidal mirror, and, iris means interposed in said beam of light at said near focus, whereby an image of said iris means is caused to focus in the far focal plane of said ellipsoidal mirror.
Claim 17
Dependent Claim
148 words
A light projection system comprising an elongated housing having one open end, an ellipsoidal mirror mounted within said housing opposite said open end, the reflecting surface of said mirror comprising a section of an ellipsoid of revolution, said section being offset to one side of a meridian plane including the axis of revolution of said ellipsoid, light source means comprising an elliptical reflector for projecting a beam of light, means for mounting said light source means within said elongated housing adjacent said open end, offset to one side thereof and remote from the near focus of said ellipsoidal mirror so as to direct said beam of light through said near focus onto said ellipsoidal mirror, and, iris means interposed in said beam of light at said near focus, whereby an image of said iris means is caused to focus in the far focal plane of said ellipsoidal mirror.
Claim 18
Dependent Claim
37 words
The light projection system of claim 14, further comprising means for mounting said ellipsoidal mirror for linear movement parallel to the central axis of said beam of light whereby the throw of said system may be adjusted.
Claim 19
Dependent Claim
32 words
The light projection system of claim 15, further comprising an annular reflector means mounted about the open end of said elliptical reflector for selectively limiting the size of said beam of light.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-08-18 | 1979-02-17 | 1979-08-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-08-18 | 1983-02-17 | 1983-08-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-08-18 | 1987-02-17 | 1987-08-19 | $7700.00 | Window Closed / Lapsed |