| 摘要 |
Off-axis projection optics that includes first and second mirrors positioned off-axis and sharing a confocal point that are arranged to reduce linear astigmatism. If a distance between an object plane and the first mirror is l<SUB>1</SUB>, an incident angle of light coming from the object plane to the first mirror is i<SUB>1</SUB>, a distance between the first mirror and the confocal point is l<SUB>1</SUB>', a distance between the confocal point and the second mirror is l<SUB>2</SUB>, an incident angle of light coming from the first mirror to the second mirror is i<SUB>2</SUB>, and a distance between the second mirror and an image plane is l<SUB>2</SUB>', the off-axis projection optics may satisfy the following equation: <maths id="MATH-US-00001" num="1"> <MATH OVERFLOW="SCROLL"> <MROW> <MROW> <MFRAC> <MROW> <MSUBSUP> <MI>l</MI> <MN>1</MN> <MI>'</MI> </MSUBSUP> <MO>+</MO> <MSUB> <MI>l</MI> <MN>1</MN> </MSUB> </MROW> <MSUB> <MI>l</MI> <MN>1</MN> </MSUB> </MFRAC> <MO></MO> <MI>tan</MI> <MO></MO> <MSTYLE> <MTEXT> </MTEXT> </MSTYLE> <MO></MO> <MSUB> <MI>i</MI> <MN>1</MN> </MSUB> </MROW> <MO>=</MO> <MROW> <MFRAC> <MROW> <MSUBSUP> <MI>l</MI> <MN>2</MN> <MI>'</MI> </MSUBSUP> <MO>+</MO> <MSUB> <MI>l</MI> <MN>2</MN> </MSUB> </MROW> <MSUB> <MI>l</MI> <MN>2</MN> </MSUB> </MFRAC> <MO></MO> <MI>tan</MI> <MO></MO> <MSTYLE> <MTEXT> </MTEXT> </MSTYLE> <MO></MO> <MROW> <MSUB> <MI>i</MI> <MN>2</MN> </MSUB> <MO>.</MO> </MROW> </MROW> </MROW> </MATH> </MATHS>
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