An optical device includes a lightguide and a display at a top of a head mountable frame. The display is oriented toward an eye-side of the optical device. A reflector is positioned at an eye-side of the optical device and directs light into the lightguide. This orientation and arrangement of components reduces light leaking out of the optical device. The lightguide includes curved first and second surfaces. The device reflects light through the curved first surface to a user eye for augmented reality vision. A head mountable frame supports the display, the reflector, and the lightguide.

A virtual image display device includes a display element, which is an image light generating unit that generates an image light, a first mirror that reflects the image light, a second mirror that reflects the image light reflected by the first mirror, and a third mirror that transmits external light and that reflects part of the image light reflected by the second mirror to guide the image light to a position of an exit pupil, wherein the first mirror has an angular dependence on a reflective surface.

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 method for designing an imaging optical system is a point-by-point calculation method based on characteristic light rays (FLR) and characteristic data points (FDP). The basic function of the point-by-point calculation method includes the following steps: according to the given object-image relationship, based on Fermat's principle and the law of retraction and reflection, calculating the propagation path of the FLR passing through a system and the FDP on each optical surface, to obtain a surface shape equation of each optical surface by fitting; and repeating the above process, to solve the surface shape equation of each optical surface one by one, and finally complete the design and solution of the entire imaging optical system.

A projection optical system of an image display apparatus that includes a lens system and a concave reflection surface. The lens system is has a positive refractive power as a whole. The concave reflection surface reflects the image light emitted from the lens system toward an object. The projection optical system is configured such that a relationship 0<|Δθ(hmax) Δθ(0.9.Math.hmax)|/θ(hmax)<0.056 is satisfied, where a light beam height from the reference axis is h, an angle with respect to an optical axis height direction of a tangent line of a function Z(h) representing a shape of the concave reflection surface corresponding to the light beam height h is θ(h), an amount of change in the angle θ(h) is Δθ(h), and the light beam height h of a reflection point farthest from the reference axis of the concave reflection surface for reflecting the image light is hmax.

An optical system includes a first optical system having a first optical element, and a second optical system arranged at a reduction side of the first optical system. An intermediate image is formed between the first optical system and the second optical system. The first optical element has a first reflecting surface having a concave shape. The second optical system has a first relay element, a second relay element arranged at an enlargement side of the first relay element, and a correction optical element arranged at the enlargement side of the second relay element. The first relay element has a first relay reflecting surface having a concave shape. The second relay element has a second relay reflecting surface having a convex shape. The correction optical element curves the intermediate image generated by the first and second relay elements to reduce a field curvature generated by the first optical element.

A spectrograph that includes camera focusing optics with a primary mirror having a concave-shaped reflective mirror surface, a secondary mirror having a convex-shaped reflective mirror surface and positioned to receive light reflected by the primary mirror, a tertiary mirror having a concave reflective mirror surface and positioned to receive light reflected by the secondary mirror, and a field correcting lens comprising a convex lens surface in combination with a concave lens surface, wherein light received by said field correcting lens from said tertiary mirror enters said convex lens surface, traverses said field correcting lens, and exits from said concave lens surface. The optional field correcting lens is positioned such that the primary mirror, secondary mirror, tertiary mirror, and the field correcting lens share the common parent vertex axis.

This image display apparatus includes a light source, an image generation unit, and a projection optical system. The image generation unit 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 refracts the image light. The first reflection optical system has two or more reflection surfaces that fold back and reflect the refracted image light. The second lens system refracts the image light reflected by the first reflection optical system. The second reflection optical system reflects the image light refracted by the second lens system toward a projection object. The first reflection optical system includes an optical component having a principal surface on which one reflection surface of the two or more reflection surfaces is configured. The principal surface includes a transmission surface that allows the image light to pass therethrough, the transmission surface being configured in a region having a shape rotationally asymmetric to the reflection surface with respect to an optical axis of the optical component and including the optical axis.

A method for designing an imaging optical system is a point-by-point calculation method based on characteristic light rays (FLR) and characteristic data points (FDP). The basic function of the point-by-point calculation method includes the following steps: according to the given object-image relationship, based on Fermat's principle and the law of retraction and reflection, calculating the propagation path of the FLR passing through a system and the FDP on each optical surface, to obtain a surface shape equation of each optical surface by fitting; and repeating the above process, to solve the surface shape equation of each optical surface one by one, and finally complete the design and solution of the entire imaging optical system.

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.