Illumination – Light source and modifier – Including selected wavelength modifier
Patent
1995-02-14
1998-08-18
Husar, Stephen F.
Illumination
Light source and modifier
Including selected wavelength modifier
359890, 353 84, F21V 900
Patent
active
057950580
DESCRIPTION:
BRIEF SUMMARY
This invention relates to colour pattern projection apparatus for projecting a colour pattern as part of a stage lighting scheme.
It is already known in stage lighting systems to use a so called gobo, which is effectively a partially transparent slide through which a light beam is passed. With appropriate focusing arrangements, a sharp image of the gobo can be formed on an illuminated subject. It is also known to provide a mounting arrangement allowing a gobo to be rotated, so that the image referred to rotates.
The present invention has for its object to provide an apparatus which can be used to project a bright image in a coloured light beam and the principle problem to be overcome in such an apparatus is the provision of a transparency which can withstand the high temperatures existing in the environment of a stage light projector.
In accordance with the broadest aspect of the invention there is provided a transparency comprising a glass substrate capable of withstanding high temperatures, said substrate having selected areas thereof coated with layers of dielectric material such that it acts as a dichroic filter.
Such filters absorb little heat when placed in a light beam, unlike pigment filters, and can therefore withstand the passage of a high intensity light beam therethrough.
In accordance with another aspect of the invention, there is provided a light beam projector comprising a light source, an optical system for concentrating light from said light source into a beam and a transparency as defined above situated in said light beam in such a position relative to said optical system that a focused image of the pattern on the transparency can be formed.
Preferably the transparency is mounted for rotation in the light beam.
Furthermore the projector may comprise a colour changer so that light passing through clear areas of the transparency is coloured by said colour changer and light passing through the coated areas of the transparency has a colour determined by the subtractive mixing effect of the colour changer and the coated areas of the transparency.
The transparency is preferably made by coating a dichroic filter with a layer of metal selectively removing areas of the metal coating so that the metal layer provides a mask and dry etching away the exposed dielectric layers, for example by laser etching. The remainder of the metal layer is then removed.
Conveniently, the metal layer is selectively removed by acid etching initially through a photographically formed etch resist mask formed over the metal layer. The remainder of the metal layer is similarly removed by acid etching after removal of the photo mask.
Alternatively, the transparency may be manufactured by applying a mask directly to the glass substrate and vacuum depositing the dielectric material on to the substrate through the mask. With this arrangement a series of masking and coating steps may be carried out so that different areas of the substrate have different filter properties and colour transmitted light differently.
In the accompanying drawings:
FIGS. 1 and 2 are diagrammatic sectional views illustrating the steps involved in manufacturing two different exemplary embodiments of the invention;
FIG. 3 is a diagrammatic view of a light beam projector in accordance with the invention; and
FIG. 4 is a diagrammatic perspective view of a multiple gobo wheel arrangement forming a part of the light beam projector.
FIG. 5 shows an embodiment with dichroic elements located on both sides of the glass substrate.
Referring firstly to FIG. 1, the transparency at the heart of the present invention is in the form of a disk of glass 10 which has one face selectively coated with areas of multi-layer dielectric film 11 which acts as a dichroic filter. The areas form a pattern on the glass disk.
The selective coating of the disk is effected by coating it all over with multi-layer dielectric film in known manner by sputtering on to it alternate layers of high and low refractive index dielectric materials such as titanium dioxide and silicon dioxide. Ot
REFERENCES:
patent: 3914464 (1975-10-01), Thomasson et al.
patent: 4779176 (1988-10-01), Bornhorst
patent: 4800474 (1989-01-01), Bornhorst
Husar Stephen F.
Light & Sound Design Ltd.
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