Abstract: Optical apparatuses used for so-called immersive virtual reality (VR), as it is, can not be used for augmented reality (AR) that overlays external light and images. An optical apparatus to overlay image light on external light and guide resultant light in a downstream side, including: an image optical system including an optical element having lens power with respect to at least the image light; and a reflecting element to overlay, by reflecting at least part of the image light, the at least part of the image light and the at least part of the external light, wherein the image optical system has a GPH element having inverse dispersibility that is inverse to the wavelength dispersibility of the optical element.

Abstract: A projection system is provided, including: a projection unit to output a projection image; a retardation plate arranged obliquely with respect to an optical axis of the projection image, the retardation plate to modulate a polarization state of the projection image incident thereon; a reflective polarizing plate stacked on a side of the retardation plate opposite to that on which the projection image is incident, the reflective polarizing plate to reflect a first polarization component of the projection image transmitted through the retardation plate; and a retro-reflective element provided along a direction in which the projection image is reflected by the reflective polarizing plate, the retro-reflective element to output reflected light against a direction in which the light is incident, wherein the reflective polarizing plate transmits a second polarization component of the projection image reflected by the retro-reflective element and modulated by the retardation plate.

Abstract: An optical device comprises: a transmittance changing unit that is provided in front of an eye of a user, and changes transmittance for light from the outside according to a voltage being applied; and a voltage control unit that controls a voltage to be applied to the transmittance changing unit by switching cyclically between a high voltage and a low voltage, wherein the voltage control unit switches the voltage at a cycle that is shorter than the sum of time required for transmittance of the transmittance changing unit to stabilize when changing from a minimum value to a maximum value by switching a voltage and time required for transmittance of the transmittance changing unit to stabilize when changing from a maximum value to a minimum value by switching a voltage.

Abstract: Conventional optical devices cannot cope with light entering from different directions in different light amounts. An optical device comprises: a transmittance changing unit that is provided in front of an eye of a user, and changes transmittance for light from the outside according to a voltage being applied; and a voltage control unit that controls a voltage to be applied to the transmittance changing unit, wherein by controlling the voltage, the voltage control unit switches between: a first relationship between frontal transmittance that is transmittance for light entering the transmittance changing unit from a frontal direction, and peripheral transmittance that is transmittance for light entering the transmittance changing unit from a direction inclined to the vertical direction relative to an entrance direction of light to which the frontal transmittance applies; and a second relationship between the frontal transmittance and the peripheral transmittance that is different from the first relationship.

Abstract: Provided is a projection image display apparatus that can restrict crosstalk between a left eye image and a right eye image. The projection image display apparatus includes a liquid crystal element that switches polarization of the light emitted from the optical modulation element between a first polarization and a second polarization, and a waveplate that is provided between the liquid crystal element and the projection surface. The waveplate includes a plurality of areas having different slow axes or fast axes from each other.