An optical system includes a first optical element. The first optical element has a first transmission surface, a first reflecting surface arranged at a reduction side of the first transmission surface, and a second transmission surface arranged at the reduction side of the first reflecting surface. The first transmission surface has power. Light passing between the first transmission surface and the first reflecting surface includes peripheral light tilted in a direction of getting away from an enlargement-side conjugated plane as coming closer to the first transmission surface. The peripheral light is tilted in a direction of coming closer to the enlargement-side conjugated plane as getting away from the first transmission surface between the first transmission surface and the enlargement-side conjugated plane.

Imaging objectives and inspection systems equipped with such imaging objectives are disclosed. The imaging objective may include a front objective configured to produce a diffraction limited intermediate image. The imaging objective may also include a relay configured to receive the intermediate image produced by the front objective. The relay may include three spherical mirrors positioned to deliver a projection of the intermediate image to a fixed image plane.

An image display device according to an embodiment of the present technology includes a light source, an image generator, and a projection optical system. The image generator modulates a light beam emitted by the light source and generates image light. The projection optical system includes a first lens system, a first reflection optical system, a second lens system, and a second reflection optical system. The first lens system has a positive refractive power as a whole, and refracts the generated image light. The first reflection optical system includes two or more reflection surfaces, each reflection surface being a surface off which the image light refracted by the first lens system is reflected. The second lens system has a positive refractive power as a whole, and refracts the image light reflected off the first reflection optical system. The second reflection optical system includes a concave reflection surface off which the image light refracted by the second lens system is reflected to be directed to a projected-onto object onto which projection is performed.

A display apparatus includes a light source; an image generation unit; and a projection optical system. The image generation unit generates image light on the basis of light from the light source. The projection optical system includes a first lens system, a first reflective optical system, a second lens system, and a second reflective optical system. The first lens system refracts the generated image light. The first reflective optical system has first and second reflection surfaces that fold back and reflect the image light refracted by the first lens system. The second lens system refracts the image light reflected by the second reflection surface. The second reflective system has a recessed reflection surface for reflecting the image light refracted by the second lens system toward an object to be projected.

The present image display apparatus includes: a light source; an image generation unit; and a projection optical system. The image generation unit generates image light on the basis of light from the light source. The projection optical system includes a first lens system, a first reflective optical system, a second lens system, and a second reflective optical system. The first lens system refracts the generated image light. The first reflective optical system has first and second reflection surfaces that fold back and reflect the image light refracted by the first lens system. The second lens system refracts the image light reflected by the second reflection surface. The second reflective system has a recessed reflection surface for reflecting the image light refracted by the second lens system toward an object to be projected. Further, the image display apparatus is configured to satisfy the following relationship: 5×10.sup.−7<α1<3×10.sup.−5 where α1 represents a linear expansion coefficient of a first optical part on which the first reflection surface is formed.

Imaging objectives and inspection systems equipped with such imaging objectives are disclosed. The imaging objective may include a front objective configured to produce a diffraction limited intermediate image. The imaging objective may also include a relay configured to receive the intermediate image produced by the front objective. The relay may include three spherical mirrors positioned to deliver a projection of the intermediate image to a fixed image plane.

An image display device according to an embodiment of the present technology includes a light source, an image generator, and a projection optical system. The image generator modulates a light beam emitted by the light source and generates image light. The projection optical system includes a first lens system, a first reflection optical system, a second lens system, and a second reflection optical system. The first lens system has a positive refractive power as a whole, and refracts the generated image light. The first reflection optical system includes two or more reflection surfaces, each reflection surface being a surface off which the image light refracted by the first lens system is reflected. The second lens system has a positive refractive power as a whole, and refracts the image light reflected off the first reflection optical system. The second reflection optical system includes a concave reflection surface off which the image light refracted by the second lens system is reflected to be directed to a projected-onto object onto which projection is performed.

In a method for three-dimensionally measuring a 3D aerial image in the region around an image plane during the imaging of a lithography mask, which is arranged in an object plane, a selectable imaging scale ratio in mutually perpendicular directions (x, y) is taken into account. For this purpose, an electromagnetic wavefront of imaging light is reconstructed after interaction thereof with the lithography mask. An influencing variable that corresponds to the imaging scale ratio is included. Finally, the 3D aerial image measured with the inclusion of the influencing variable is output. This results in a measuring method with which lithography masks that are optimized for being used with an anamorphic projection optical unit during projection exposure can also be measured.

An imaging optical unit serves within a metrology system for examining a lithography mask. The lithography mask can be arranged in an object field of the imaging optical unit. The object field is defined by two mutually perpendicular object field coordinates. The imaging optical unit has an aperture stop of which the aspect ratio in the direction of the two object field coordinates differs from 1. This results in an imaging optical unit which can be used for the examination of lithography masks that are designed for projection exposure with an anamorphic projection optical unit.

An image forming optical system 1 includes, in order from an enlargement side, a first optical system 111 having a reflecting surface, and a second optical system 112 having a refracting surface. The image forming optical system 1 is configured to form an intermediate image 104 between the first optical system 111 and the second optical system 112. The first optical system 111 includes, in order from the enlargement side, a first reflecting group 113 having at least one reflecting surface having negative power, and a second reflecting group 114 having a plurality of reflecting surfaces 116 and 117 having positive power. The at least one reflecting surface having negative power includes a reflecting surface 115 closest to the enlargement side in the first reflecting group 113. An absolute value of power of the reflecting surface 115 is smallest in the first optical system 111.