An imaging optical unit includes a plurality of mirrors to guide imaging light along an imaging beam path. The plurality of mirrors includes a number of mirrors for grazing incidence (GI mirrors), which deflect a chief ray of a central object field point with an angle of incidence of more than 45°. At least two of the GI mirrors are in the imaging beam path as basic GI mirrors so that the deflection effect thereof adds up for the chief ray. At least one further GI mirror is arranged in the imaging beam path as a counter GI mirror so that the deflection effect thereof acts in subtractive fashion for the chief ray in relation to the deflection effect of the basic GI mirrors. This can yield an imaging optical unit having enhanced flexibility in relation to an installation space used for mirror bodies of the mirrors of the imaging optical unit.

A reflective imager design that is telecentric in image space, or equivalently telecentric at an image plane, or equivalently having an exit pupil located substantially at infinity, while also having an external entrance pupil and a high throughput or fast optical speed is described.

An optical system includes an incident part, a first reflective surface, a second reflective surface, a third reflective surface, and an exit part. The incident part is rotationally symmetric around a central axis. Incident light from the incident part intersects the central axis and enters the first reflective surface. Reflected light from the first reflective surface intersects the central axis and enters the second reflective surface. Reflected light from the second reflective surface enters the third reflective surface.

A telescope includes an initial telescope comprising a concave first mirror and a convex second mirror that are configured so that they form, from a light beam coming from infinity, an image called the intermediate image in a focal plane called the intermediate focal plane, the intermediate image having a largest dimension along an X-axis perpendicular to an optical axis of the telescope, a segmenting module comprising a first set of n segmenting mirrors that are placed downstream of the intermediate focal plane and that are configured to divide the intermediate image obtained from the intermediate focal plane into n sub-images, a second set of n refocusing mirrors that are configured to reimage the n sub-images into n images in a focal plane of the telescope, the images being arranged in the focal plane so as to decrease the dimension along X containing the n images, a detecting device placed in the focal plane.

An unobscured five-mirror afocal telescope includes an aperture configured to direct electromagnetic radiation to first, second, third, fourth and fifth mirrors, each configured to receive electromagnetic radiation and reflect electromagnetic radiation along a beam path. The five mirrors are arranged to sequentially reflect from one another electromagnetic radiation received via the aperture to produce a collimated output beam of the electromagnetic radiation at an exit pupil, with the five mirrors consisting of a three-element objective and a two-element eyepiece. A beam splitter may be disposed between the first mirror and the second mirror to direct short-wavelength electromagnetic radiation toward a device along a separate path.

Methods and systems for relaying an optical image using a cascade arrangement of tilted, concave mirrors are presented. An exemplary optical relay system includes a cascade arrangement of four mirrors each having concave, spherical surface figures. The first and third mirrors are configured to focus collimated wavefronts and the second and fourth mirrors re-collimate diverging wavefronts reflected from the first and third mirrors. Each mirror is tilted such that wavefronts located in the local field plane and local pupil plane of each mirror are physically separated. The magnitude and direction of each tilt angle are arranged such that off-axis aberrations introduced by each individual mirrors are largely compensated by the other mirrors. Such an optical relay system is employed to relay images of the pupil plane of a metrology system that is configured to perform accurate measurements of semiconductor structures and materials over a broad range of illumination wavelengths.

Systems and methods for providing a wider FOV for a telescope system are disclosed. In one embodiment, a telescope includes a primary mirror having an orifice, where an optical path originates from an object positioned in front of the primary mirror and reflects off the primary mirror. A secondary mirror is disposed adjacent to the primary mirror, where the optical path reflects off the secondary mirror and passes through the orifice in the primary mirror. The telescope includes a set of extended field corrector optics disposed along the optical path, the extended field corrector optics positioned to reflect light incident from the secondary mirror, where the set of extended field corrector optics includes two corrector mirrors. A tertiary mirror is disposed along the optical path and adjacent to the extended field corrector optics, the tertiary mirror positioned to reflect the light incident from the extended field corrector optics.

The disclosure provides a method and to an apparatus for determining the heating state of a mirror in an optical system, in particular in a microlithographic projection exposure apparatus. A method for determining the heating state of an optical element includes: measuring values of a first temperature that the optical element has at a first position using a temperature sensor; and estimating a second temperature that the optical element has at a second position, which is located at a distance from the first position, on the basis of the measured values, wherein estimating the second temperature is accomplished while taking into account a temporal change in the previously measured values.

Optical system includes front group, light-shielding member, and rear group that are arranged from object side toward image side. The light-shielding member is provided with opening elongated in first direction. The front group has aspherical surface, does not image the object at the opening in first section parallel to the first direction, and forms intermediate image of the object at the opening in second section perpendicular to the first direction. The rear group has diffractive surface that splits light beam that passes through the opening into light beams at different wavelengths in the second section and focuses the light beams on different locations in the second section. The curvature radius of the aspherical surface in the second section at on-axis position in the first direction differs from that at outermost off-axis position in the first direction.

In the first embodiment and the second embodiment, the case where an image is projected on the retina 52 of one of the eyes 50 has been described, but an image may be projected on the retinas 52 of both eyes 50. In addition, the scan mirror 14 has been described as an example of a scan unit, but the scan unit may be any element as long as it can scan a light beam. For example, other components such as potassium tantalate niobate (KTN) crystal that is an electro-optic material may be used as the scan unit. The case where the light beam is a laser beam has been described as an example, but the light beam may be light other than the laser beam.