In a method for producing an optical unit having an optical element deviating from a circular shape, for an optical imaging system, in particular for a projection objective in semiconductor lithography in the EUV region, a supporting part is provided, which is provided with reference surfaces for adjustment in the optical system, in accordance with which the optical element is connected to the supporting part. Subsequently, there is fixed relative to the optical element a zero point which forms a reference point with a zero point fixed in the optical system during installation of the optical unit in the optical system.
1. An optical unit comprising an optical element deviating from a circular shape, for an optical imaging system, and a supporting part which is provided with reference surfaces for adjustment to said optical imaging system, said supporting part being connected to said optical element, and said reference surfaces being referred to a zero point relative to said optical element which forms a reference point with a zero point fixed in said optical imaging system during installation of said optical unit in the optical imaging system;
wherein the reference surfaces are provided on said supporting part and comprise at least three coplanar reference surfaces which form a reference plane;
a first locating edge, lying at an angle to the coplanar reference surfaces, of said supporting part;
a second locating position by means of which translatory displacements along the first locating edge are avoided;
wherein said supporting part is provided with an underpart on the side avert from said optical element;
wherein a basic body with a plane surface is provided via which said basic body is connected to said supporting part, and wherein said basic body has a reflecting surface as the optical element; and
wherein the supporting part, the reflecting surface and the underpart comprise individual parts, and wherein said individual parts of said optical unit are connected to one another by wringing.
2. The optical unit according to claim 1 , wherein said three reference surfaces forming a reference plane lie perpendicular to the optical axis.
3. The optical unit according to claim 1 , wherein said first locating edge lies perpendicular to the reference plane.
4. The optical unit according to claim 1 , wherein said second locating position is constructed as a locating edge.
5. The optical unit according to claim 1 , wherein said reference surfaces simultaneously form fastening surfaces to which said optical unit with the optical system is connected.
6. The optical unit according to claim 5 , wherein said reference surfaces lie adjacent to said fastening surfaces.
7. The optical unit according to claim 1 , wherein the supporting part and the underpart comprise individual parts, and wherein said individual parts are formed from the same material, in particular a material of very low thermal expansion.
8. The optical unit according to claim 1 , wherein the shape of the optical element is relative a cross-sectional plane of the optical element that is oriented perpendicularly to an optical axis of the optical element.
9. An optical unit comprising an optical element deviating from a circular shape, for an optical imaging system, and a supporting part which is provided with reference surfaces for adjustment to said optical imaging system, said supporting part being connected to said optical element, and said reference surfaces being referred to a zero point relative to said optical element which forms a reference point with a zero point fixed in said optical imaging system during installation of said optical unit in the optical imaging system; and
wherein a basic body with a plane surface is provided via which said basic body is connected to said supporting part, and wherein said basic body has a reflecting surface as the optical element.
10. The optical unit according to claim 9 , wherein said reflecting surface is formed in said basic body as a freeform numerous surface.
11. The optical unit according to claim 9 , wherein said reflecting surface is formed from a parent from which said reflecting surface is cut out.