An imaging optical unit for projection lithography has a plurality of mirrors for guiding imaging light from an object field in an object plane into an image field in an image plane along an imaging light beam path. At least two of the mirrors are embodied as GI mirrors. Exactly one stop serves to predefine at least one section of an outer marginal contour of a pupil of the imaging optical unit. The stop is arranged spatially in front of a penultimate mirror in the imaging light beam path. This results in an imaging optical unit that is well defined with regard to its pupil and is optimized for projection lithography.

A five-mirror all-reflective afocal anastigmat. In one example, a five mirror afocal anastigmat includes five mirrors arranged to sequentially reflect from one another electromagnetic radiation received via a system entrance pupil to produce a collimated output beam of the electromagnetic radiation at a system exit pupil, the five mirrors consisting of three positive-powered mirrors and two negative-powered mirrors, wherein optical powers of the five mirrors are balanced to achieve a flat field condition at the system exit pupil.

An all-reflective coronagraph optical system for continuously imaging a wide field of view. The optical system can comprise a fore-optics assembly comprising a plurality of mirrors that reflect light rays, about a wide field of view centered around the Sun, to an aft-optics assembly that reflects the light rays to an image sensor. A fold mirror, having an aperture, is optically supported between the fore-optics assembly and the aft-optics assembly. The aperture defines an angular subtense (e.g., 1.0 degree) sized larger than the angular subtense of the Sun. The aperture facilitates passage of a direct solar image and a solar thermal load. A thermal control subsystem comprises a shroud radiatively coupled to each fore-optics mirror and the fold mirror. A cold radiator is thermally coupled to each shroud. Heaters adjacent fore optics mirrors and the fold mirror control temperature to provide a steady state optical system to minimize wavefront error.

There is provided a reflective image-forming optical system which is applicable to an exposure apparatus using, for example, EUV light and which is capable of increasing numerical aperture while enabling optical path separation of light fluxes. In a reflective imaging optical system (6) forming an image of a first plane (4) onto a second plane (7), the numerical aperture on a side of the second plane with respect to a first direction (X direction) on the second plane is greater than 1.1 times a numerical aperture on the side of the second plane with respect to a second direction (Y direction) crossing the first direction on the second plane. The reflecting imaging optical system has an aperture stop (AS) defining the numerical aperture on the side of the second plane, and the aperture stop has an elliptic-shaped opening of which size in a major axis direction (X direction) is greater than 1.1 times that in a minor axis direction (Y direction).

A radiation source for a lithographic apparatus uses a plurality of fiber lasers to ignite a fuel droplet at an ignition location to generate EUV radiation. The fiber lasers may be provided to emit parallel to an optical axis and a telescopic optical system is provided to focus the lasers at the ignition location, or the lasers may be directed towards the optical axis with a final focus lens being used to reduce beam waist. The lasers may be provided in two or more groups to allow them to be independently controlled and some of the lasers may be focused at a different location to provide a pre-pulse. Radiation from fiber lasers may also be combined using dichroic mirrors.

A reflective imaging optical system which forms, on a second plane, an image of a pattern arranged on a first plane and illuminated with light from an illumination optical system includes a plurality of reflecting mirrors including first and second reflecting mirrors by which the light reflected by the first plane is reflected first, second, respectively. An area on the first plane illuminated with the light from the illumination optical system is an illumination objective area, the illumination objective area is positioned on a predetermined side of an optical axis of the reflecting mirrors, and reflection areas of the first and second reflecting mirrors are positioned on the predetermined side of the optical axis of the reflecting mirrors; and the first and second reflecting mirrors are arranged so that an optical path of the light from the illumination optical system is positioned between the first and second reflecting mirrors.

A projection objective with obscurated pupil for microlithography has a first optical surface, which has a first region provided for application of useful light, and at least one second optical surface, which has a second region provided for application of useful light. A beam envelope of the useful light extends between the first region and the second region. At least one tube open on the input side and on the output side in the light propagation direction severs to screen scattered light. The at least one tube is between the first optical surface and the second optical surface. The wall of the tube is opaque in the wavelength range of the useful light. The tube extends in the propagation direction of the useful light over at least a partial length of the beam envelope and circumferentially surrounds the beam envelope.

An optical system that images a scene at two different fields of view, with switching between fields of view enabled by switchable mirrored surface is disclosed. A voltage change across the switchable mirror element generates a change in the reflection and transmission properties of the element, such that the element switches between a mirror state and a lens state. When nested in an annular reflective optic system of a given field of view, the switching element enables the opening of an additional optical path through the center of the reflective optics where a set of refractive optics are assembled into an imaging system for a second field of view. This dual field-of-view system changes field of view with no mechanical movement.

There is provided a reflective imaging optical system forming an image of a first plane onto a second plane, wherein the numerical aperture with respect to a first direction on the second plane is greater than 1.1 times a numerical aperture with respect to a second direction crossing the first direction on the second plane. The reflecting imaging optical system has an aperture stop defining the numerical aperture on the side of the second plane, and the aperture stop has an elliptic-shaped opening of which size in a major axis direction is greater than 1.1 times that in a minor axis direction. The reflective image-forming optical system is applicable to an exposure apparatus using, for example, EUV light and capable of increasing numerical aperture while enabling optical path separation of light fluxes.

An optical relay system includes four or more reflective optical elements oriented in a tilted configuration. Each of the four or more reflective optical elements is tilted about one of four or more tilt axes. Further, the four or more tilt axes are oriented to correct for aberrations induced by the tilted configuration.