Optical: systems and elements – Single channel simultaneously to or from plural channels – By partial reflection at beam splitting or combining surface
Patent
1995-01-31
1996-05-07
Epps, Georgia Y.
Optical: systems and elements
Single channel simultaneously to or from plural channels
By partial reflection at beam splitting or combining surface
348757, 353 34, 359 73, G02B 2714, G02F 011335, G02F 100, G03B 2126
Patent
active
055152023
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to an optical projector arrangement comprising
a light source,
an optical system for forming light from the source into a parallel beam travelling along a given axis in a given direction,
a beam splitter and a beam synthesiser positioned in succession in the given direction along the given axis, the beam splitter being constructed and arranged for receiving the parallel beam travelling along the given axis, splitting it into first, second and third spectral components, and launching these components into first, second and third paths respectively to the beam synthesizer, the beam synthesizer being constructed and arranged for receiving the first, second and third spectral components travelling along the first, second and third paths respectively and combining them into a synthesized beam travelling along the given axis in the given direction, the total paths for the first and second components through the arrangement being of equal optical length, the first and second paths each having an initial portion which extends away from the given axis in a respective direction which is perpendicular to the given axis and the third path having initial and final portions which both extend along the given axis in the given direction,
a first reflector arrangement constructed and arranged for receiving the first spectral component from the initial portion of the first path and directing it into a central portion of the first path which extends in the given direction parallel to the given axis and thereafter into a final portion of the first path which extends towards the given axis in a direction perpendicular thereto,
a second reflector arrangement constructed and arranged for receiving the second spectral component from the initial portion of the second path and directing it into a central portion of the second path which extends in the given direction parallel to the given axis and thereafter into a final portion of the second path which extends towards the given axis in a direction perpendicular thereto,
first, second and third liquid crystal light modulators included in the first, second and third paths respectively, and
a projection lens for receiving the synthesized beam.
A known arrangement of this general kind is disclosed in U.S. Pat. No. 4,850,685, and is illustrated schematically in FIG. 1 of the accompanying diagrammatic drawings.
Referring to FIG. 1 it will be seen that, in the known projector arrangement, light from a light source 1 is focussed at 3 by a reflector 2 and is thereafter collimated by a condenser lens 4. The collimated light passes along an axis 5 through a polarizer 6 to a beamsplitter 8 in the form of a color separation cube prism. The constitution of such a cube prism is well known to those skilled in the art and will not be described in any great detail herein. The flat face 10 is coated with a red-reflecting dichroic layer, for example that available from the Corion company under the type number CR-600, and the flat face 12 is coated with a blue-reflecting dichroic layer, for example that available from the Corion company under the type number CR-500. The faces 10 and 12 intersect and are perpendicular to each other. They are each at 45.degree. to the axis 5. The polarization axis of polarizer 6 is chosen to be perpendicular to the incidence surface of cube prism 8 (s-polarization). Thus it will be realized that light from the light source 2 which enters the cube prism 8 will be spectrally split such that the red component is reflected up, perpendicular to the axis 5, along a path 7 toward a first mirror arrangement, in this example mirrors 14, 18, and the blue component is reflected down, again perpendicular to the axis 5, along a path 9 toward a second mirror arrangement, in this example mirrors 16, 20. The green component of light will be simply transmitted by the cube prism 8 along the axis 5 to a beam synthesizer 30.
The red light component is reflected in a direction parallel to axis 5 from 45.degree. mirror 14 to 45.degree. mirr
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Central Research Laboratories Limited
Epps Georgia Y.
Mack R.
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