Optical system for forming a real image in space
An optical system ( 100, 200, 400, 500 ) that projects a real image ( 140, 412, 504 ) into space and includes one or more features located along the optical path that enhance the viewability of the real image. The optical system includes a converging element ( 128, 208, 416, 528 ) for converging a portion of source light ( 104, 516 ) so as to form the real image. One viewability-enhancing feature is the use of a broadband reflector-polarizer ( 124, 208, 408, 532 ) having high transmitting and reflecting efficiencies. Another viewability-enhancing feature is the use of polarizing elements ( 116, 124, 136, 408, 420, 424 ) having substantially matched bandwidth responses and/or comprising an achromatic design. An additional viewability-enhancing feature is the use of a wide-view film ( 144 ) to increase the viewing angle of the image.
1. An optical system for forming a real image from source light from a source, comprising:
(a) at least one converging element for converging a portion of the source light so as to form the real image when the optical system is in use; and
(b) a broadband reflector-polarizer located in an optical path between said at least one converging element and the real image and opposite the source when the optical system is in use;
wherein said at least one converging element comprises said broadband reflector-polarizer in a cylindrical configuration.
2. An optical system according to claim 1 , further comprising a circular polarizer located in said optical path between the source and said broadband polarizer when the optical system is in use.
3. An optical system according to claim 2 , wherein said circular polarizer comprises a linear polarizer and a quarter wave retarder.
4. An optical system according to claim 3 , wherein said broadband reflector-polarizer has a first bandwidth response and said quarter wave retarder has a second bandwidth response that is substantially matched to said first bandwidth of said broadband reflector-polarizer.
5. An optical system according to claim 3 , wherein said quarter wave retarder comprises liquid crystal polymers.
6. An optical system according to claim 1 , further comprising a beamsplitter located in said optical path between the source and the real image when the system is in use.
7. An optical system according to claim 6 , wherein said beamsplitter has a cylindrical configuration.
8. An optical system according to claim 7 , wherein said at least one converging element has a first axis of curvature and said beamsplitter has a second axis of curvature orthogonal to said first axis of curvature.
9. An optical system according to claim 1 , further comprising a direct-view light extinguisher located in said optical path between said broadband reflector-polarizer and the real image when the optical system is in use.
10. An optical system according to claim 1 , wherein said broadband reflector-polarizer comprises a cholesteric liquid crystal structure.
11. An optical system according to claim 1 , wherein said broadband reflector-polarizer has a transmissive/reflectance efficiency of at least 60%.
12. An optical system according to claim 11 , wherein said transmissive/reflectance efficiency is at least 90%.
13. An optical system according to claim 1 , further comprising a wide view film located in said optical path between said broadband reflector-polarizer and the real image when the optical system is in use.