An aerial display apparatus includes: a light source unit that emits light; a display device that transmits the light from the light source unit to display an image; a light control device that transmits the light from the display device to emit the light such that light intensity of the light has a peak in a direction oblique to a normal direction that is perpendicular to a first direction within a principal plane of the display device; and a mirror device that reflects the light from the light control device to display an image in air on a side opposite to the light control device. The mirror device includes a plurality of optical elements each having a hexahedron shape. Each of the plurality of optical elements includes first and second reflection surfaces that reflect light. Each of the first and second reflection surfaces is placed obliquely to the normal direction.

An aerial display apparatus includes: a light source unit that emits light; a display device that transmits the light from the light source unit to display an image; a light control device that transmits the light from the display device to emit the light such that light intensity of the light has a peak in a direction oblique to a normal direction that is perpendicular to a first direction within a principal plane of the display device; and a mirror device that reflects the light from the light control device to display an image in air on a side opposite to the light control device. The mirror device includes a plurality of optical elements each having a hexahedron shape. Each of the plurality of optical elements includes first and second reflection surfaces that reflect light. Each of the first and second reflection surfaces is placed obliquely to the normal direction.

A system for infrastructure system calibration includes a sensor configured to be mounted to an infrastructure component and configured to detect an object. A corner reflector has an optical pattern and is arranged within a field of view of the sensor. The corner reflector has three surfaces that meet at a point.

An apparatus includes a reflecting element with first, second and third reflecting surfaces, and a receiving element configured to receive a light flux from a light source reflected by the reflecting element. A value of an inner product of a unit normal vector of the first reflecting surface and a unit normal vector of the second reflecting surface, a value of an inner product of the unit normal vector of the first reflecting surface and a unit normal vector of the third reflecting surface, and a value of an inner product of the unit normal vector of the second reflecting surface and the unit normal vector of the third reflecting surface are appropriately set.

An apparatus includes a reflecting element with first, second and third reflecting surfaces, and a receiving element configured to receive a light flux from a light source reflected by the reflecting element. A value of an inner product of a unit normal vector of the first reflecting surface and a unit normal vector of the second reflecting surface, a value of an inner product of the unit normal vector of the first reflecting surface and a unit normal vector of the third reflecting surface, and a value of an inner product of the unit normal vector of the second reflecting surface and the unit normal vector of the third reflecting surface are appropriately set.

A spherically mounted retroreflector comprising an optic inlay, the optic inlay comprising a retroreflector having a vertex and an axis of symmetry, and a carrier having an at least partly spherical outer surface and a cavity, wherein the optic inlay is arranged in the cavity, and wherein the at least partly spherical outer surface has a sphere center, which sphere center coincides with the vertex, wherein the optic inlay is connected to the carrier. The optic inlay comprises a coupling portion, and the spherically mounted retroreflector comprises a coupling element arranged between the optic inlay and the carrier.

A spherically mounted retroreflector comprising an optic inlay, the optic inlay comprising a retroreflector having a vertex and an axis of symmetry, and a carrier having an at least partly spherical outer surface and a cavity, wherein the optic inlay is arranged in the cavity, and wherein the at least partly spherical outer surface has a sphere center, which sphere center coincides with the vertex, wherein the optic inlay is connected to the carrier. The optic inlay comprises a coupling portion, and the spherically mounted retroreflector comprises a coupling element arranged between the optic inlay and the carrier.

To achieve a highly accurate device for back-reflecting a beam with high accuracy over a large lateral offset, an apparatus is disclosed which reflects an incoming beam or image, allowing the reflected beam to be accurately deflected at an angle of 180 degrees over a large offset distance. The reflections inside the device are caused by an accurate 90 degrees reflection on its one end, towards opposite reflecting mirrors which will further bend the beam an additional 90 degrees, creating a total deflection of an incoming beam to be parallel and laterally deflected in respect to the original direction of the incoming beam. The two opposite transmitting and bending surfaces could be based on two mirrors on each end, and preferable at relative angles similar to existing pentaprisms. The said bending mirror surfaces on each end could be coated with anti-reflection coating or with reflection-improving metal coatings.

To achieve a highly accurate device for back-reflecting a beam with high accuracy over a large lateral offset, an apparatus is disclosed which reflects an incoming beam or image, allowing the reflected beam to be accurately deflected at an angle of 180 degrees over a large offset distance. The reflections inside the device are caused by an accurate 90 degrees reflection on its one end, towards opposite reflecting mirrors which will further bend the beam an additional 90 degrees, creating a total deflection of an incoming beam to be parallel and laterally deflected in respect to the original direction of the incoming beam. The two opposite transmitting and bending surfaces could be based on two mirrors on each end, and preferable at relative angles similar to existing pentaprisms. The said bending mirror surfaces on each end could be coated with anti-reflection coating or with reflection-improving metal coatings.

A multistage prism window includes first and second transparent plate materials, a first prism, a reflection member, a second prism, and a heat absorption member. The first prism collects, onto the reflection member, light whose angle with respect to a normal line of the first and second transparent plate materials is equal to or greater than a first predetermined angle and transmits light whose angle with respect thereto is smaller than the first predetermined angle. The second prism collects, onto the heat absorption member, light whose angle with respect to the normal line is smaller than the first predetermined angle and equal to or greater than a second predetermined angle and transmits light whose angle with respect thereto is smaller than the second predetermined angle.