| 摘要 |
PROBLEM TO BE SOLVED: To provide a strong and simple equal-magnification optical projection system for a photo-lithography device that operates at an i-line LED wavelength and has an enough area size to handle four to six dies.SOLUTION: An equal-magnification large-sized cata-dioptric lens includes, along an optical axis, an aspherical concave mirror, a convergent lens group alienated from the concave mirror, and first and second total reflection prisms arranged on both sides of the optical axis nearby the opposite side of the convergent lens group from the concave mirror. A first prism has a first surface close to an object surface, and the second prism has a second surface close to an image surface. The convergent lens group comprises three or four lens elements, one of the lens elements has a positive meniscus shape, and the lens has a numerical aperture of 0.32 in name to substantially has an equal magnification, and also has a Strehl ratio of larger than 0.95 at least on an image region. |
