Provided is a reflective screen and a projection image display system in which a transmittance of light can be selectively changed, a transmittance in a transparent state is sufficiently high, a voltage does not need to be applied constantly, and a voltage is applied to decrease a transmittance of light in a case where the reflective screen is irradiated with video light. The reflective screen includes: a light reflecting layer that is formed of a cholesteric liquid crystal layer and where a selective reflection wavelength at a polar angle of 60° is present in a visible range, in which senses of helix of all of cholesteric liquid crystal layers are the same and Expression (1) is satisfied; and a transparent first electrode, a transparent second electrode, and a light control layer that are provided on a rear side with respect to the light reflective layer, the light control layer being disposed between the first electrode and the second electrode, in which the light control layer includes a polymer network and liquid crystal molecules and changes between a first state where light is scattered and a second state where transmission of light is allowed by changing a magnitude of a voltage applied, the polymer network having a three-dimensional net shape having a plurality of domains, and the liquid crystal molecules being positioned in the domains.

R[−60,40](550)/R[−60,30](550)≥1.5  Expression (1)

An optical element includes a light guide plate, an incidence portion, and an emission portion, in which each of the incidence portion and the emission portion includes diffraction portions, the diffraction portion includes diffraction elements, the diffraction element includes a liquid crystal diffraction layer in which a direction of an optical axis of a liquid crystal compound changes while continuously rotating in one in-plane direction, and in a case where the direction in which the direction of the optical axis changes is set as an in-plane rotation direction and a length over which the optical axis rotates by 180° is set as an in-plane period, in-plane rotation directions of liquid crystal diffraction layers of incidence diffraction elements in at least two of a plurality of the incidence diffraction portions are different from each other.

Provide are an optical element that can improve a utilization efficiency of light while increasing an optical path length, an image display unit, and a head-mounted display. The optical element includes, in the following order: a first absorptive linearly polarizing plate; a first reflective linearly polarizing plate; a first retardation plate; a partially reflecting mirror that allows transmission of a part of incident light and reflects a part of the incident light; a second retardation plate; and a second reflective linearly polarizing plate, in which a turning direction of circularly polarized light that is reflected from the first reflective linearly polarizing plate in a case where light transmits through the first retardation plate and is incident into the first reflective linearly polarizing plate is opposite to a turning direction of circularly polarized light that is reflected from the second reflective linearly polarizing plate in a case where light transmits through the second retardation plate and is incident into the second reflective linearly polarizing plate.

Provided are an optical element and an image display apparatus that display an aerial image, in which the total volume of the apparatus is small, a reduction in size can realized, and a scenery can be recognized. The optical element includes: a light guide element including a light guide plate, an incidence diffraction element, and an emission diffraction element, the incidence diffraction element being disposed on a main surface of the light guide plate and the emission diffraction element being disposed on the main surface of the light guide plate; and a positive lens that is disposed at a position overlapping the emission diffraction element in a view from a direction perpendicular to the main surface of the light guide plate, in which the incidence diffraction element diffracts incident light such that the diffracted light is incident into the light guide plate, the emission diffraction element emits light propagating in the light guide plate from the light guide plate, and the positive lens collects the light that is emitted from the light guide plate by the emission diffraction element.

Provided are: an image display apparatus in which the utilization efficiency of a virtual image is high and the virtual image having high brightness uniformity can be displayed to be superimposed on a real image; and AR glasses including the image display apparatus. The image display apparatus includes: a display element; one or more cholesteric liquid crystal layers that reflect a display image of the display element; and a transparent reflection element that reflects the image reflected by the cholesteric liquid crystal layer to the cholesteric liquid crystal layer, in which at least one of the cholesteric liquid crystal layers has a structure having a region where a surface pitch changes in a thickness direction.

Provided are: an image display apparatus that can display augmented reality in a virtual image is superimposed on a bright real scene; and AR glasses including the image display apparatus. The image display apparatus includes: a display element; and a reflective polarization diffraction element that reflects an image displayed by the display element, in which the polarization diffraction element has a region where a period of a diffraction structure decreases in a direction away from the display element.

A device includes a light source configured to generate an image light. The device also includes a lens assembly coupled with the light source. The lens assembly includes a mirror configured to transmit a first portion of the image light and reflect a second portion of the image light. The lens assembly also includes a reflective polarizer including a birefringent medium with a chirality and configured to substantially reflect the first portion of the image light output from the mirror as a polarized light having a predetermined handedness toward the mirror. The lens assembly further includes a lens disposed between the mirror and the reflective polarizer and configured to provide an optical power to the image light.

A projection type transparent display includes a polarization modulator and a reflective layer. The polarization modulator is stacked in sequence by a linear polarizer, a liquid crystal layer and a phase retarder. The reflective layer is stacked on the phase retarder. A projection light is incident on the linear polarizer to form a linearly polarized light. The liquid crystal layer changes a polarization direction of the linearly polarized light. Two kinds of linearly polarized projection lights with polarization directions orthogonal to each other are respectively formed and pass through the phase retarder to respectively form two kinds of circularly polarized projection lights with opposite rotation directions. A background light is incident on the reflective layer. A circularly polarized background light with the same spiral direction is reflected, and the circularly polarized background light opposite to the spiral direction passes through the reflective layer and is incident on the polarization modulator.

A one-way glass with switching modes includes an absorbing layer located on a weak light side, a reflecting layer located on an intense light side, and a converting layer stacked between the absorbing layer and the reflecting layer. The absorbing layer absorbs first polarized light and allows second polarized light to pass through. The reflecting layer reflects the first polarized light and allows the second polarized light to pass through. Unpolarized light incident from the weak light side or from the intense light side is respectively converted into the polarized light. During the process of gradually adjusting the converting layer from a twisted state to a vertical state, rotated angles of polarization directions of the first polarized light and the second polarized light gradually decrease.

An optical element is provided. The optical element includes an optical film including a birefringent material having a chirality. Optically anisotropic molecules of the birefringent material disposed adjacent a first surface of the optical film are configured with a first pretilt angle in a range of greater than 10° and less than 80°, or in a range of greater than −80° and less than −10°. Optically anisotropic molecules of the birefringent material disposed adjacent a second surface of the optical film opposing the first surface are configured with a second pretilt angle in the range of greater than 10° and less than 80°, or in the range of greater than −80° and less than −10°.