A system (100, 300) for adapting a diameter of a photon beam (S, S) comprises: a first element (1) with a curved surface which bas a first and a second focus (F1, F2). The system may be set up such that the photon beam is focused into the first focus (F1), so that the photon beam is focused onto the second focus (F2) after reflection at the surface of the first element (1).

An aerial image display device includes a display, a convex mirror, and a concave mirror. The convex mirror reflects image light emitted from the display. The concave mirror reflects, in a direction different from a direction toward the convex mirror, the image light reflected from the convex mirror to form an aerial image as a real image. The concave mirror has a greater curvature than the convex mirror.

An inspection device for inspecting a panel, in particular a display, or a PCB, includes a first mirror, a second mirror, a third mirror, and a sensor. The first mirror, the second mirror, and the third mirror are arranged to display a section of the panel to be inspected on the sensor with a magnification factor greater than one. At least two of the group of the first mirror, the second mirror, and the third mirror, have both a first type of curvature, and a remaining mirror has a second type of curvature, opposite to the first type of curvature. The first mirror, the second mirror, and the third mirror form a telecentric system which is telecentric on a panel facing side and/or on a sensor facing side.

A head up display that utilizes a backlight Toroidal mirror to adjust the eye box is suitable for use with an imaging semi-reflector and includes a backlight source, a backlight Toroidal mirror, a display panel, and an imaging concave mirror. The backlight Toroidal mirror is rotatable and has an X-axis curvature and a Y-axis curvature different from the X-axis curvature, and can reflect the backlight beam of the backlight source. The backlight beam reflected by the backlight Toroidal mirror forms a backlight real image located in the viewer's eye after passing through the display panel, the imaging concave mirror, and the imaging semi-reflector. The backlight real image is called the eye box. The rotation of the backlight Toroidal mirror elongates or shortens the eye box, allowing the viewer's eyes to remain inside the eye box when the viewer's eyes are moving back and forth.

An aerial image display device includes a display, an optical system that forms an aerial image as a real image from image light emitted from the display, a light-transmissive screen between the aerial image and the optical system, and an image projector that emits projection image light toward the light-transmissive screen in a direction different from an optical axis direction of the image light between the aerial image and the optical system. The light-transmissive screen transmits the image light and diffuses the projection image light to display a projection image.