Abstract: A light guide includes an exit extension region including a diffraction structure dividing an image light ray propagating in a first direction intersecting a thickness direction of a body, into image light rays propagating in a second direction intersecting the first direction, in the first direction, and allowing them to emerge therefrom. At least one part of the region satisfies that when refractive indices of media on individual incident and exit sides of a ray relative to the region are assumed to be equal to each other, an exit angle ?_out of a ray emerging from the region at the highest diffraction efficiency in a plane including a normal line of the region is not smaller than 15° and is not greater than 45°, and an incident angle ?_in of a ray incident on the region in the plane is greater than ?_out by 14° or more.

Abstract: The optical system includes a light guide including: an incident region allowing an image light ray to enter a body; and an exit extension region including a diffraction structure dividing an image light ray into image light rays and allowing them to emerge from the body. The exit extension region divides the image light ray into first to third image light rays. The first and third image light rays emerge from the exit extension region at different angles to propagate inside the body. The exit extension region includes an overlap part on which the first image light ray and the third image light ray are incident under a condition where they partially overlap with each other. A difference between optical paths of the first image light ray and the third image light ray incident on the overlap part is longer than a coherence length of the image light ray.

Abstract: An optical system according to the present disclosure includes a first sub-optical system including an aperture stop and a second sub-optical system including a prism. The prism has a first transmission surface located on the reduction side, a second transmission surface located on the magnification side, and at least one reflection surface located on the optical path between the first transmission surface and the second transmission surface. A first reflection surface closest to the intermediate imaging position has a shape with a concave surface facing a direction into which a light ray incident on first the reflection surface is reflected. A curvature shape of the first reflection surface is set such that some of multiple principal rays passing through the reduction conjugate point intersect on the optical path between the first reflection surface and the second transmission surface.

Abstract: A head-up display is configured to project an image on a transparent reflection member to cause an observer to visually recognize a virtual image, and includes a display device configured to display the image, and a projection optical system configured to project the image displayed by the display device as the virtual image for the observer. The projection optical system is configured to form an image as an intermediate image, and includes a first lens configured to condense light, and a first optical element configured to diffuse light. The first lens and the first optical element are disposed in this order along an optical path from the display device. The first lens is inclined with respect to a reference beam which is defined as a beam reaching a center of a viewpoint region of the observer and corresponding to a center of the virtual image.

Abstract: An optical system includes an incidence part changing a traveling direction of the incident image light from a display part and an expansion part that divides and duplicates the image light traveling from the incidence part. The expansion part includes a first and a second expansion part. The first expansion part includes a first and a second diffraction structure part each having a diffraction structure that divides and duplicates the image light along a first direction, and a non-diffraction structure part disposed between the first and the second diffraction structure part. The second expansion part includes a third diffraction structure part that divides and duplicates image light along the first direction. The third diffraction structure part is disposed to overlap with the non-diffraction structure part of the first expansion part in a vertical direction with respect to the pupil expansion part.

Abstract: The optical system includes a light guide including a reproduction region including a dividing diffraction structure dividing an image light ray propagating in a first propagation direction intersecting a thickness direction of a body, into image light rays propagating in a second propagation direction intersecting the first propagation direction, in the first propagation direction and including first and second diffraction structure regions formed respectively at first and second surfaces in the thickness direction to face each other, and an exit diffraction structure allowing the image light rays propagating in the second propagation direction to travel toward a field of view region. When first and second field of view angles in first and second directions of the virtual image are denoted by FOV1 and FOV2, a relation of FOV2/FOV1<0.5 is satisfied. The first propagation direction in the reproduction region corresponds to the first direction in a virtual image.

Abstract: An optical system includes a first expansion region that expands a luminous flux traveling in a first direction by splitting and duplicating it into luminous fluxes traveling in a second direction intersecting the first direction to increase the number of luminous fluxes, and a second expansion region that expands the luminous fluxes traveling in the second direction by splitting and duplicating them to increase the number of luminous fluxes. The first expansion region has a central region that contains a center of the first expansion region, and an end region that lies on at least one end side of the first expansion region. The end region has a diffracted light quantity less than half the diffracted light quantity in the central region.

Abstract: A head-up display is configured to project an image on a transparent reflection member to cause an observer to visually recognize a virtual image, and includes a display device configured to display the image, and a projection optical system configured to project the image displayed by the display device as the virtual image for the observer. The projection optical system is configured to form an image as an intermediate image, and includes a first lens configured to condense light, and a first optical element configured to diffuse light. The first lens and the first optical element are disposed in this order along an optical path from the display device. The first lens is inclined with respect to a reference beam which is defined as a beam reaching a center of a viewpoint region of the observer and corresponding to a center of the virtual image.

Abstract: The optical system includes: a light guide for guiding an image light ray to a field of view region of a user as a virtual image. The light guide includes a diffraction structure region constituting a surface-relief diffraction grating dividing the image light ray propagating in a first propagation direction intersecting a thickness direction of a body into a plurality of image light rays propagating in a second propagation direction intersecting the first propagation direction, in the first propagation direction. The diffraction structure region includes a first diffraction structure, and a second diffraction structure on an opposite side of the first diffraction structure from an in-coupling region in the first propagation direction. A grating height of the first diffraction structure is greater than a grating height of the second diffraction structure. A grating width of the first diffraction structure is greater than a grating width of the second diffraction structure.

Abstract: A display device displays a virtual image by projecting an image onto a windshield provided on a vehicle and having a curved shape. The display device includes: an image generation device that generates light (image light) representing an image; and a light guide that includes an emission hologram element having a non-rectangular quadrilateral shape. The emission hologram element emits, toward the windshield, the light representing the image and propagating through the light guide.

Abstract: The present disclosure provides an optical system that includes a prism having an incident surface, an exit surface, and one or more reflecting surfaces. The optical system includes a first scanning element configured to scan in a first direction a light that enters and reflect the light in a direction of the incident surface of the prism, and a second scanning element configured to scan in a second direction the light that exits from the exit surface of the prism, the second direction being orthogonal to the first direction. The incident surface of the prism has a convex shape with respect to the first scanning element.

Abstract: A head-up display is configured to project an image on a transparent reflection member to cause an observer to visually recognize a virtual image, and includes a display device configured to display the image, and a projection optical system configured to project the image displayed by the display device as the virtual image for the observer. The projection optical system is configured to form the image as an intermediate image, and includes a first optical element configured to condense light, a first lens configured to condense light, and a second optical element configured to diffuse light. The first optical element, the first lens, and the second optical element are disposed in this order along an optical path from the display device.

Abstract: In a display device, an opening portion includes a first edge portion on a forward side and a second edge portion on a backward side of the opening portion in a traveling direction of a mobile object. When the display device is mounted on the mobile object, a line connecting an upper end of the first edge portion and a lower end of the second edge portion is taken as a reference line, and outside light that passes along the reference line and enters a light-transmissive member is taken as reference outside light, the reference outside light for the case where the opening portion is in a first position arrives at a lower position, at least partially in an optical path after the reference outside light is reflected at the light-transmissive member, than the reference outside light for the case where the opening portion is in the second position.

Abstract: The present disclosure is directed to an optical system having a reduction conjugate point on a reduction side and a magnification conjugate point on a magnification side, and internally having an intermediate imaging position having a conjugate relationship with each of the reduction conjugate point and the magnification conjugate point, the optical system including: a prism provided on the magnification side, the prism formed of a transparent medium; and a sub-optical system provided between the reduction conjugate point and the prism, the sub-optical system, wherein the prism includes a first transmission surface positioned on the reduction side, a second transmission surface positioned on the magnification side, and at least one reflection surface positioned therebetween, wherein the following Expression is satisfied: 0.40<(TN?((NI?1)/8))/PN2<0.64.

Abstract: A head-up display is configured to project an image on a transparent reflection member to cause an observer to visually recognize a virtual image, and includes a display device configured to display the image, and a projection optical system configured to project the image displayed by the display device as the virtual image for the observer. The projection optical system is configured to form the image as an intermediate image, and includes a first optical element configured to condense light, a first lens configured to condense light, and a second optical element configured to diffuse light. The first optical element, the first lens, and the second optical element are disposed in this order along an optical path from the display device.

Abstract: The optical system includes a light guide guiding an image light ray including a first light ray with a first wavelength range and a second light ray with a second wavelength range having wavelengths shorter than wavelengths in the first wavelength range, to a field of view region as a virtual image. The light guide includes a first dividing region including first dividing points dividing the incident first light ray and a second dividing region including second dividing points dividing the incident second light ray. The first dividing points include first and second points respectively corresponding to first and second peripheral regions of the field of view region. The second dividing points include third and fourth points respectively corresponding to the first and second peripheral regions. Dividing efficiencies E1 to E4 at the first to fourth points satisfy the following formula (1). ( E ? 2 E ? 1 ) ÷ ( E ? 4 E ? 3 ) × ( E ? 3 E ? 1 ) 2 < 0.

Abstract: The present disclosure provides an optical system that includes a prism having an incident surface, an exit surface, and one or more reflecting surfaces. The optical system includes a first scanning element configured to scan a light that enters and has a plurality of wavelengths in a first direction, and reflect the light in a direction of the incident surface of the prism. The optical system includes a second scanning element configured to scan in a second direction the light that exits from the exit surface of the prism, the second direction being orthogonal to the first direction. The incident surface of the prism has a concave shape with respect to the first scanning element.

Abstract: An optical system includes a display that emits a light flux visually recognized by an observer as an image, and a light guide body that replicates the light flux. The light flux is emitted from the emission surface after being expanded by being replicated in a first direction corresponding to a horizontal direction of the image visually recognized by the observer due to diffraction by a diffraction structure of an expansion region in the light guide body, a second direction corresponding to a vertical direction of the image, or both the directions. A coherence length of the light flux diffracted and emitted in the expansion region in the light guide body is smaller than twice a shorter interval between the diffraction structure and each of a front surface and a back surface of the light guide body.

Abstract: A light flux incident on the light guide body is replicated in a first direction or a second direction by a diffraction structure of an expansion region. When a normal direction with respect to the light guide body of the expansion region is defined as a Z-axis direction, and a tangential plane is defined as an XY plane, the diffraction structure of the expansion region is configured such that a light flux duplicated when the light flux incident on the expansion region is transmitted through the XY plane of the expansion region from a positive direction of the Z axis and a light flux duplicated when the light flux is transmitted through the XY plane of the expansion region from a negative direction of the Z axis are accommodated within a viewing angle at which the image is visually recognizable.

Abstract: An image display device includes a display, a light guide body, a controller, and a sensor. The light guide body includes an incident surface on which the light flux from the display is incident and an emission surface from which the light flux is emitted from the light guide body. The light flux incident on the incident surface of the light guide body is changed in a traveling direction in the light guide body, and is emitted from the emission surface so as to expand a visual field area by being replicated in a horizontal direction and a vertical direction of the virtual image visually recognized by the observer. The sensor that detects a physical quantity used to obtain a wavelength of the light flux. The controller controls a position and a shape of the image displayed by the display based on the physical quantity detected by the sensor.