Abstract: A projection substrate including: an incident region that includes a diffraction grating in which a plurality of first grooves are formed with a first period; a splitting region that includes a diffraction grating in which a plurality of second grooves are formed with a second period; and an emission region that includes a diffraction grating in which a plurality of third grooves are formed with a third period, wherein the incident region guides an incident projection light toward the splitting region, the splitting region includes a plurality of first divided regions, each having the second grooves with different depths, and guides a part of the projection light entering from the incident region toward the emission region, and the emission region guides at least a part of the projection light entering from the splitting region and emits that part of the projection light as an image light from a second surface.

Abstract: A projection optical system including: a projection substrate for projecting an image light onto a second surface while transmitting at least a part of light, that is incident from a first surface, to the second surface opposite to the first surface, the projection substrate having an optical waveguide; and a polarization reduction plate that is provided on the first surface side with an air layer between itself and the optical waveguide, covers at least a part of the optical waveguide, and reduces light with a polarization direction from the image light leaking from the first surface of the projection substrate, wherein the optical waveguide guides at least a part of projection light for projecting the image light, and emits the projection light as the image light from the second surface.

Abstract: A projection optical system includes: a projection substrate for projecting an image light onto a second surface while transmitting at least a part of light incident from a first surface to the second surface opposite to the first surface, the projection substrate having an optical waveguide; and a diffracted light reduction plate that is provided on the first surface side of the projection substrate with an air layer between itself and the optical waveguide, covers at least a part of the optical waveguide, which diffracts an input light incident from the first surface of the projection substrate at a predetermined incident angle, and reduces diffracted light that travels in an emission direction of the image light, wherein the optical waveguide guides at least a part of projection light for projecting the image light, and emits that part of the projection light as the image light from the second surface.

Abstract: A projection substrate including: an incident region that guides a projection light to a splitting region; a splitting region that includes a first diffraction grating that guides the projection light to an emission region; and the emission region that includes a second diffraction grating that emits the projection light from a second surface, wherein a ratio of the width of a convex portion to a period of a concave-convex portion of the first diffraction grating differs depending on a distance to the incident region.

Abstract: A projection substrate having an incident region into which a projection light enters, the projection substrate including: a transparent substrate that transmits light that entered from a first surface to a second surface opposite to the first surface and transmits the projection light that projects an image on the second surface; a diffraction grating that is formed on the transparent substrate and guides the projection light to an emission region; and a reflective layer that reflects the projection light on the opposite side of the diffraction grating.

Abstract: This projection substrate is for causing an image to be projected onto a second surface on the opposite side of a first surface while causing at least a portion of light of a specific wavelength range incident on the first surface to be transmitted through the second surface, the projection substrate having a transparent glass plate that is provided on the first surface side, and a diffraction grating that is provided on the second surface side with respect to the glass plate and that has a plurality of grooves formed with a resist so that light corresponding to the image propagates while being diffracted, wherein the thickness of a resist film between the bottom surface of the grooves and the glass plate is determined on the basis of the wavelength of light diffracted in the grooves.

Abstract: A projection substrate including: an incident region that includes a diffraction grating in which a plurality of first grooves are formed with a first period; a splitting region that includes a diffraction grating in which a plurality of second grooves are formed with a second period; and an emission region that includes a diffraction grating in which a plurality of third grooves are formed with a third period, wherein the incident region guides an incident projection light toward the splitting region, the splitting region includes a plurality of first divided regions, each having the second grooves with different depths, and guides a part of the projection light entering from the incident region toward the emission region, and the emission region guides at least a part of the projection light entering from the splitting region and emits that part of the projection light as an image light from a second surface.