| 摘要 |
A projection optical system includes, in order from a first conjugate point side of longer distance to a second conjugate point side of shorter distance, a first lens unit in which negative lenses included therein are larger in number than positive lenses included therein, and a second lens unit in which positive lenses included therein are larger in number than negative lenses included therein, wherein design parameters are determined such that an off-axial principal ray intersects an optical axis at a point between the first lens unit and the second lens unit and telecentricity is made on the second conjugate point side, and wherein the second lens unit includes, in order from the second conjugate point side, a negative lens of meniscus form convex toward the second conjugate point side and a positive lens whose both surfaces are convex.
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