Patent Number: 
Section: claims

1. An X-ray microscope comprising:an X-ray source;a sample holding part;a concave KB mirror which is a Kirkpatrick-Baez mirror having a reflection concave surface, and is a one-dimensional condensing mirror having curvature only in one direction;a convex KB mirror which is a Kirkpatrick-Baez mirror having a reflection convex surface, and is a one-dimensional condensing mirror having curvature only in one direction; anda light receiving part located at a position in an imaging relation to a position of the sample holding part in this order,wherein the reflection concave surface of the concave KB mirror includes an elliptical curve. 2. The X-ray microscope according to claim 1, whereinthe sample holding part is located at a focal position of the elliptical curve. 3. The X-ray microscope according to claim 1, wherein:the reflection convex surface of the convex KB mirror includes one curved line of a hyperbolic curve that is composed of the one curved line and another curved line; andthe light receiving part is located at a focal position of the other curved line side of focal positions of the hyperbolic curve. 4. The X-ray microscope according to claim 1, whereina distance between the concave KB mirror and the light receiving part is longer than a distance between the convex KB mirror and the light receiving part. 5. The X-ray microscope according to claim 1, whereina principal plane of an imaging system including the convex KB mirror and the concave KB mirror is located between the sample holding part and the concave KB mirror. 6. The X-ray microscope according to claim 1, whereina distance between the position of the sample holding part and the position of the light receiving part is 2.5 m or less. 7. The X-ray microscope according to claim 1, wherein:the convex KB mirror is one of at least two convex KB mirrors;the concave KB mirror is one of at least two concave KB mirrors;a normal of a first of the at least two convex KB mirrors and a normal of a second of the at least two convex KB mirrors are nonparallel to each other; anda normal of a first of the at least two concave KB mirrors and a normal of a second of the at least two concave KB mirrors are nonparallel to each other. 8. The X-ray microscope according to claim 1, whereina shortest distance between the sample holding part and the concave KB mirror is 6 mm or more. 9. The X-ray microscope according to claim 1, whereinat least one of the convex KB mirror and the concave KB mirror is movable in an optical axis direction. 10. The X-ray microscope according to claim 1, wherein:the concave KB mirror is a first concave KB mirror;a second concave KB mirror and a third concave KB mirror are between the sample holding part and the first concave KB mirror;a normal of the first concave KB mirror and a normal of the second concave KB mirror are nonparallel to each other; anda normal of the convex KB mirror and a normal of the third concave KB mirror are nonparallel to each other. 11. The X-ray microscope according to claim 10, wherein:the second concave KB mirror is closer to the sample holding part than the third concave KB mirror;a reflection concave surface of the second concave KB mirror includes a hyperbolic curve; anda reflection concave surface of the third concave KB mirror includes an elliptical curve. 12. The X-ray microscope according to claim 1, whereinthe X-ray source is configured to emit an X-ray having energy of 2 keV or higher. 13. The X-ray microscope according to claim 1, whereinthe concave KB mirror and the convex KB mirror are grazing incidence X-ray mirrors.