Color changer

• US 5,975,720 A
• Filed: 09/29/1997
• Issued: 11/02/1999
• Est. Priority Date: 09/29/1997
• Status: Expired due to Fees

• Current Assignee: Ricardo Lighting Company, Limited
• Original Assignee: Ricardo Lighting Company, Limited
• Inventors: Adkins, Sean
• Primary Examiner(s): HUSAR, STEPHEN F
• Application Number:
  US08/939,386
• Time in Patent Office: 764 Days
• Field of Search: 362/293, 362/322, 362/324, 362/325, 359/889, 359/890, 359/892
• US Class Current: 362/293
• CPC Class Codes: F21V 9/40 with provision for controlling spectral properties, e.g. colour, or intensity
• CPC Class Codes: F21W 2131/406 for theatres, stages or film studios
• CPC Class Codes: G02B 26/007 the movable or deformable optical element controlling the colour, i.e. a spectral characteristic, of the light

Abstract

A color changer for use with a wide angle light source which includes a frame, a plurality of planar dichroic filter strips mounted on the frame and aligned substantially parallel to each other. The filter strips have identical predetermined optical filtering characteristics with first and second sets of the filter strips movable along a common axis so as to vary the gap between them and at least alternate ones of the filter strips in each of the first and second sets set at an angle such that, when the color changer is positioned in a beam of light transmitted from the wide angle light source, a substantially constant angle of incidence is maintained with respect to light from the light source incident on the alternate ones of the dichroic filter strips.

Claims

1. A colour changer for use with a wide angle light source, comprising:

a frame;

a plurality of planar dichroic filter strips mounted on said frame and aligned substantially parallel to each other, said filter strips having identical predetermined optical filtering characteristics, first and second sets of said filter strips movable along a common axis so as to vary the gap between said first and said second set of filter strips and at least alternate ones of said filter strips in each of said first and second sets set at an angle such that when said colour changer is positioned in a beam of light transmitted from said wide angle light source a substantially constant angle of incidence is maintained with respect to light from said light source incident on said alternate ones of said dichroic filter strips.

2. A colour changer according to claim 1, wherein said colour changer is dimensioned to extend at least substantially across the width of a beam of light emerging from said wide angle light source proximate to said light source.

3. A colour changer according to claim 1, including a diffuser positioned adjacent said colour changer so as to intercept light rays passing through said colour changer and cause mixing of the light rays.

4. A colour changer according to claim 1, wherein said dichroic filters are disposed with respect to each other such that edges of adjacent filter strips adjoin and said strips form a saw tooth pattern in cross section.

5. A colour changer according to claim 1, wherein said dichroic filters comprise of elongated rectangular strips of glass covered with a dichroic coating.

6. A colour changer according to claim 1, wherein an angle of inclination of said dichroic filter strips with respect to a plane through a face of said colour changer gradually increases from a minimum inclination for filter strips nearest to a centre of said colour changer with increasing inclinations for each successive filter strip as one proceeds away from the centre in either of two opposite directions to a maximum inclination for filter strips proximate outer edges of said colour changer.

7. A colour changer according to claim 1, wherein said dichroic filter strips are moveable to provide a variable gap between alternate ones of said filter strips.

8. A colour changer according to claim 1, wherein said first and second sets of filter strips are mounted in a first and second frame set, respectively, and including a lead screw threadedly coupled to each of said frame sets operative to reversibly move said first and second frame sets away from a centre of said colour changer at an equal rate.

9. A colour changer according to claim 5, wherein said dichroic filter strips are aligned along an axis parallel to their respective long sides.

10. A colour changer for use with a wide angle light source, comprising:

a track;

a pair of frame sets having guide blocks affixed thereto along bottom edges of each of said frame sets slidable in said tracks;

a plurality of rectangular, planar dichroic filter strips rotatably mounted on each of said frame sets and aligned substantially parallel to each other along their long sides, said filter strips having identical predetermined optical filtering characteristics, said frame sets movable along said tracks so as to vary the gap between said first and said second set of filter strips and at least alternate ones of said filter strips in each of said first and second sets set at an angle such that when said colour changer is positioned in a beam of light transmitted from said wide angle light source a substantially constant angle of incidence is maintained with respect to light from said light source incident on said alternate ones of said dichroic filter strips;

a cam block contacting one of said filter strips, said cam block shaped to cause said one filter strip to rotate upon translational movement away and towards a center of said colour changer and an abutment affixed to said one filter strip and contacting an adjacent filter strip independently rotationally mounted in said frame set such that rotation of said one filter strip in a first direction causes rotation of said adjacent filter strip in the first direction and abutments on each subsequent filter strip contacting a further adjacent independently rotationally mounted filter strip so as to cause rotation of the further adjacent filter strip in the same direction as and in response to rotation of the subsequent filter strip;

a torsion spring coupled to said filter strips so as to bias said one filter strip against said cam block and said adjacent filter against said one filter strip;

a plurality of threaded nuts affixed to tops of said frame sets;

a lead screw threadedly engaging said threaded nuts with threads oriented so that said frame sets move apart and together upon rotation of said lead screw in respective first and second directions of rotation; and

a motor coupled to said lead screw operative to cause rotation of said lead screw.

11. A colour changer for use with a wide angle light source, comprising:

a frame;

a plurality of dichroic filter strips aligned with each other in a first direction and capable of transmitting light having a predetermined optical characteristic, said dichroic filters slidably coupled to said frame; and

a filter mover operative to move said dichroic filters into at least a first and second arrangement,

wherein in said first arrangement;

said dichroic filters are arranged on said frame so that when said colour changer is positioned in front of said light source, said filter intersects a beam of light emitted from said wide angle light source such that a substantially constant angle of incidence is maintained for the light falling on each of a plurality of said dichroic filter strips; and

wherein in said second arrangement;

said dichroic filters are substantially removed from the beam of light emitted from the wide angle light source.

12. A method of filtering light emitted from a wide angle light source with a colour changer having a plurality of dichroic filter strips which filter light from said light source to produce substantially uniform colour, the method comprising the steps of:

positioning said colour changer so as to intersect a beam of the light from said wide angle light source; and

orienting said dichroic filters with respect to the light such that a substantially constant angle of incidence is maintained for light incident on each of a plurality of said dichroic filter strips so as to cause a substantial amount of light transmitted through said colour changer to have a similar colour.