ILLUMINATION OPTICAL SYSTEM AND EXPOSURE APPARATUS
An illumination optical system includes a barrel configured to house a lens having an optical axis that extends in a direction perpendicular to a gravity direction, wherein the barrel includes an inner surface that has a pair of projections each contacting an outer circumference surface of the lens, and wherein on a plane perpendicular to the optical axis, when viewed from an intersection between the optical axis and the plane perpendicular to the optical axis, an absolute value of an angular range in which each projection contacts the outer circumference surface of the lens is from 5° to 40° with respect to an axis that passes the intersection and is parallel to the gravity direction.
1 . An illumination optical system configured to illuminate a surface, the illumination optical system comprising a barrel configured to house a lens having an optical axis that extends in a direction perpendicular to a gravity direction,
wherein the barrel includes an inner surface that has a pair of projections each contacting an outer circumference surface of the lens, and
wherein on a plane perpendicular to the optical axis, when viewed from an intersection between the optical axis and the plane perpendicular to the optical axis, an absolute value of an angular range in which each projection contacts the outer circumference surface of the lens is from 5° to 40° with respect to an axis that passes the intersection and is parallel to the gravity direction.
2 . The illumination optical system according to claim 1 , wherein the pair of projections are asymmetrically arranged with respect to the axis that passes the intersection and is parallel to the gravity direction.
3 . An exposure apparatus comprising an illumination optical system that includes a barrel configured to house a lens having an optical axis that extends in a direction perpendicular to a gravity direction,
wherein the barrel includes an inner surface that has a pair of projections each contacting an outer circumference surface of the lens, and
wherein on a plane perpendicular to the optical axis, when viewed from an intersection between the optical axis and the plane perpendicular to the optical axis, an absolute value of an angular range in which each projection contacts the outer circumference surface of the lens is from 5° to 40° with respect to an axis that passes the intersection and is parallel to the gravity direction.
4 . A device manufacturing method comprising the steps of:
exposing a substrate using an exposure apparatus; and
developing the substrate that has been exposed,
wherein the exposure apparatus includes an illumination optical system that includes a barrel configured to house a lens having an optical axis that extends in a direction perpendicular to a gravity direction,
wherein the barrel includes an inner surface that has a pair of projections each contacting an outer circumference surface of the lens, and
wherein on a plane perpendicular to the optical axis, when viewed from an intersection between the optical axis and the plane perpendicular to the optical axis, an absolute value of an angular range in which each projection contacts the outer circumference surface of the lens is from 5° to 40° with respect to an axis that passes the intersection and is parallel to the gravity direction.