| 摘要 |
An optical system for a visual display comprises a cathode ray tube for projecting a visual image along a central axis and a first fresnel lens for receiving the visual image. The first fresnel lens is provided with fresnel grooves facing the cathode ray tube. Second and third fresnel lenses forming a liquid doublet first fresnel lens pair are disposed in front of the first fresnel lens for receiving the visual image projected therethrough. The first fresnel lens pair is provided with fresnel grooves facing each other. The liquid disposed therebetween is provided with predetermined indexes of refraction and dispersion for color correcting the optical system. Fourth and fifth fresnel lenses are provided forming a second fresnel lens pair disposed in front of the first fresnel lens pair for receiving the visual image projected therethrough. The second fresnel lens pair is provided with fresnel grooves facing each other.
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