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Catadioptric reduction projection optical system

  • US 5,289,312 A
  • Filed: 09/22/1992
  • Issued: 02/22/1994
  • Est. Priority Date: 09/28/1991
  • Status: Expired due to Fees
First Claim
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1. A catadioptric reduction projection optical system for projecting a reduced image of a pattern of a first surface onto a second surface, including:

  • a first lens unit G1 for refracting a light beam from said first surface;

    a semi-transparent mirror having a plane parallel plate for reflecting the light beam from said first lens unit G1;

    a concave reflecting mirror for returning the light beam from said semi-transparent mirror to said semi-transparent mirror while converging said light beam;

    a second lens unit G2 of negative refractive power disposed between said semi-transparent mirror and said concave reflecting mirror;

    a third lens unit G3 of positive refractive power for converging the light beam returned to said semi-transparent mirror by the reflection on said concave reflecting mirror and transmitted through said semi-transparent mirror and forming the reduced image of the pattern of said first surface on said second surface; and

    stop means disposed between said semi-transparent mirror and said third lens unit G3.

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