Patent Number: 
Section: claims

1. Illumination system, particularly for microlithography with wavelengths ≦ 193 nm, comprising:a primary light source; a first optical component; a second optical component; an image plane; and an exit pupil, wherein said first optical component transforms said primary light source into a plurality of secondary light sources that are imaged by said second optical component in said exit pupil, wherein said first optical component includes a first optical element having a plurality of first raster elements, that are imaged into said image plane producing a plurality of images being superimposed at least partially on a field in said image plane, wherein said second optical component, comprises a first optical system comprising at least a field mirror with positive optical power and a second optical system comprising at least a further field mirror with positive optical power, wherein said first optical system images said plurality of secondary light sources in a plane between said first optical system and said second optical system forming a plurality of tertiary light sources, and wherein said second optical system images said plurality of tertiary light sources in said exit pupil.  2. The illumination system according to claim 1, wherein conjugated planes to the image plane in the second optical component are virtual conjugated planes. 3. The illumination system according to claim 1, wherein the field mirror and the further field mirror form an off-axis Gregorian telescope. 4. The illumination system according to claim 1, wherein said plane between said first optical system and said second optical system is freely accessible. 5. The illumination system according to claim 1, further comprising a masking unit for changing an illumination mode, wherein said masking unit is arranged at or nearby said plurality of tertiary light sources. 6. The illumination system according to claim 1, wherein a transmission filter is arranged at or nearby said plurality of tertiary light sources. 7. The illumination system according to claim 1, wherein each of a plurality of rays intersects said further field mirror with an incidence angle lower than 25° relative to surface normals. 8. The illumination system according to claim 1, wherein said further field mirror is an off-axis segment of a rotational symmetric reflective surface. 9. The illumination system according to claim 1, wherein said further field mirror is an on-axis segment of a toroidal reflective surface. 10. The illumination system according to claim 1, wherein each of a plurality of rays intersects said field mirror with an incidence angle of less than 25° relative to surface normals. 11. The illumination system according to claim 1, wherein said field mirror is an off-axis segment of a rotational symmetric reflective surface. 12. The illumination system according to claim 1, wherein said field mirror is an on-axis segment of a toroidal reflective surface. 13. The illumination system according to claim 1,wherein said plurality of first raster elements are rectangular, wherein said field is a segment of an annulus, and wherein said second optical component includes a field mirror for shaping said field to said segment of said annulus.  14. The illumination system according to claim 13, wherein said field mirror for shaping said field to said segment of said annulus has negative optical power. 15. The illumination system according to claim 13, wherein each of a plurality of rays intersects said field mirror for shaping said field to said segment of said annulus with an incidence angle greater than 70° relative to surface normals. 16. The illumination system according to claim 13, wherein said field mirror for shaping said field to said segment of said annulus is an off-axis segment of a rotational symmetric reflective surface. 17. The illumination system according to claim 13, wherein said field mirror for shaping said field to said segment of said annulus is an on-axis segment of a toroidal reflective surface. 18. The illumination system according to claim 13,wherein said first optical component further comprises a second optical element having a plurality of second raster elements, and wherein each of said plurality of first raster elements corresponds to one of said plurality of second raster elements.  19. The illumination system according to the claim 18, wherein said plurality of second raster elements and said second optical component image said corresponding plurality of first raster elements into said image plane. 20. The illumination system according to claim 18, wherein said plurality of second raster elements are concave mirrors. 21. A projection exposure apparatus for microlithography comprising:the illumination system of claim 1; a reticle being located at said image plane; a light-sensitive object on a support system; and a projection objective to image said reticle onto said light-sensitive object.