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Projection displays with divergent chief rays at beam splitter
| Details |
Inventors: Sekine, Atsushi; Hattori, Tetsuo;
Assignee: Nikon Corporation (Tokyo, JP)
Primary Examiner: Parker; Kenneth
Assistant Examiner:
Attorney, Agent or Firm: Klarquist Sparkman, LLP
Projection displays are disclosed that reduce the loss of image contrast due to angle-of-incidence and color dependencies of liquid crystal display panels, polarizing beamsplitters, and dichroic reflectors. The projection displays comprise an illumination source that provides a light flux that made uniform by an integrator. A color separation system then divides the light flux into red, green, and blue color components. The color-components are directed through field lenses to polarizing beamsplitters and then to liquid crystal light valves. The color components are reflected by the light valves back through the polarizing beamsplitters to a projection lens that forms an image. The projection lens is preferably telecentric. Field lenses are provided that direct substantially collimated color components to the liquid crystal light valves. |
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DETAILED DESCRIPTION Projection displays according to the invention preferably comprise a color-separation optical system having a plurality of substantially parallel dichroic mirrors.
The color-separation system separates a light flux from a light source into multiple (e.
g.
, first, second, and third) color components.
Alternatively, the dichroic mirrors of the color-separation system are arranged to form a crossed dichroic-mirror or prism.
A separate light valve is provided for individually modulating each corresponding color component.
Multiple (e.
g.
, first, second, and third) polarizing beamsplitters are provided to polarize the color components before the color components are incident to corresponding light valves; the polarizing beamsplitters further serve to analyze the color components after modulation and reflection by the light valves.
Because each polarizing beamsplitter is used with a single color component, the polarizing beamsplitters can have performance superior to that of a polarizing beamsplitter to be used with multiple color components.
A color-combining optical system is provided to re-combine the color components after the color components are modulated and analyzed.
The color-combining optical system preferably comprises an L-shaped dichroic prism having a plurality of substantially parallel dichroic reflecting surfaces.
Alternatively, a plurality of substantially parallel dichroic mirrors can be provided or a plurality of substantially parallel dichroic films.
Similarly, crossed-dichroic mirrors can be used instead of a crossed-dichroic prism.
Because the color-combining system receives the color components after analysis by the polarizing beamsplitters, birefringence and other polarization effects in the color-combining system have little effect on image contrast.
Expensive, low-birefringence materials and mountings are unnecessary.
A projection optical system receives the combined, modulated, and analyzed color components from the color-combining optical system and forms an image
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Lighting 
