Patent Number: 
Section: claims

1. An extreme ultraviolet light generating device comprising:a chamber in which extreme ultraviolet light is generated from a target supplied to a generation region;a focusing mirror configured to reflect the extreme ultraviolet light, generated in the generation region, by a reflection surface, and focus the extreme ultraviolet light at a predetermined focal point, the predetermined focal point being located farther from the reflection surface than the generation region;a light source unit connected with the chamber, the light source unit being configured to output illumination light toward the target to be supplied to the generation region; anda light receiving unit connected with the chamber, the light receiving unit being configured to receive reflected light from the target, of the illumination light output toward the target, and capture an image of the target,the reflection surface of the focusing mirror having a spheroidal face that defines a first focus at the generation region and a second focus at the predetermined focal point, and the light source unit and the light receiving unit being disposed such that at least one of an optical path of the illumination light and an optical path of the reflected light is included in an internal space of the chamber located between a first limit surface and a second limit surface; assuming that a surface formed when an extended line, on the first focus side, of a line segment linking an outer peripheral edge of the reflection surface and the first focus is rotated about an axis passing through the first focus and the second focus, is the first limit surface, and assuming that a surface formed when the line segment linking the outer peripheral edge of the reflection surface and the first focus, and an extended line, on the outer peripheral side, of the line segment, are rotated about the axis passing through the first focus and the second focus, is the second limit surface. 2. The extreme ultraviolet light generating device according to claim 1, wherein,in a case of describing the internal space of the chamber with use of a polar coordinate system in which the first focus is a polar, a distance from the polar is a radius vector, and an angle of the radius vector with respect to the axis passing through the first focus and the second focus is an deflection angle θ [rad],assuming that an acute angle defined by the line segment linking the outer peripheral edge of the reflection surface and the first focus and the axis passing through the first focus and the second focus is represented by θm,assuming that a region included in the internal space satisfying a relationship of 0<θ≤θm is a first region, andassuming that a region included in the internal space satisfying a relationship of θm<θ<(π−θm) is a second region,the light source unit and the light receiving unit are disposed such that at least one of the optical path of the illumination light and the optical path of the reflected light is included in the second region. 3. The extreme ultraviolet light generating device according to claim 2, whereinthe light source unit is disposed such that the optical path of the illumination light passes through the first focus and is included in the second region, andthe light receiving unit is disposed such that the optical path of the reflected light passes through the first focus and is included in the first region. 4. The extreme ultraviolet light generating device according to claim 3, wherein,assuming that a half value of a divergence angle of the illumination light is represented by θd,assuming that a half value of a beam width of the illumination light passing through the first focus is represented by W,assuming that a distance from the outer peripheral edge of the reflection surface to the axis passing through the first focus and the second focus is represented by R, andassuming that a distance from the outer peripheral edge of the reflection surface to the first focus in a direction along the axis passing through the first focus and the second focus is represented by L,the light source unit is disposed such that the optical path of the illumination light is included in the internal space described by the deflection angle θ satisfying a relationship ofR(θd sin θ−cos θ)<L(θd cos θ+sin θ)−W.  5. The extreme ultraviolet light generating device according to claim 2, whereinthe light source unit is disposed such that the optical path of the illumination light passes through the first focus and is included in the second region, andthe light receiving unit is disposed such that the optical path of the reflected light passes through the first focus and is included in the second region. 6. The extreme ultraviolet light generating device according to claim 2, whereinthe light source unit is disposed such that the optical path of the illumination light passes through the first focus and is included in the first region, andthe light receiving unit is disposed such that the optical path of the reflected light passes through the first focus and is included in the second region.