Embodiments of the disclosure provide a projection display apparatus comprising: a light source for emitting a light beam; a first light path configured to project the light beam emitted from the light source to a first display position; a second light path configured to project the light beam emitted from the light source to a second display position; a light patch switching device configured to switch the light beam emitted from the light source between the first light path and the second light path; and a light modulation device through which both the first light path and the second light path pass, wherein the light modulation device is configured to modulate the light beam passing therethrough to generate a display image.

Embodiments of the disclosure provide a projection display apparatus comprising: a light source for emitting a light beam; a first light path configured to project the light beam emitted from the light source to a first display position; a second light path configured to project the light beam emitted from the light source to a second display position; a light patch switching device configured to switch the light beam emitted from the light source between the first light path and the second light path; and a light modulation device through which both the first light path and the second light path pass, wherein the light modulation device is configured to modulate the light beam passing therethrough to generate a display image.

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.

A system for imaging in the air including an image source, a transflector, and a retroreflective element. Light rays emitted by the image source are reflected by the transflector to irradiate on the retroreflective element, and are subjected to reflection on the retroreflective element, before being emitted along an original incident path in an opposite direction and being transmitted through the transflector to form a real image. By means of the present system, it is possible to directly present images in the air, even in vacuum, without the aid of any medium.

According to one embodiment, a display device including a display unit which emits display light, an optical element which includes a first surface on the display unit side, and a second surface on a side opposite to the first surface, and transmits and reflects incident light, and a retroreflective element provided on the first surface side or the second surface side, wherein the retroreflective element includes first and second retroreflectors which retroreflect light made incident through the optical element, and a transmissive portion located between the first retroreflector and the second retroreflector.

According to one embodiment, a display device including a display unit which emits display light, an optical element which includes a first surface on the display unit side, and a second surface on a side opposite to the first surface, and transmits and reflects incident light, and a retroreflective element provided on the first surface side or the second surface side, wherein the retroreflective element includes first and second retroreflectors which retroreflect light made incident through the optical element, and a transmissive portion located between the first retroreflector and the second retroreflector.

Chaff is provided for deployment from an aerial platform for retro-reflecting electromagnetic radiation projected to the platform. The chaff includes a plurality of retro-reflecting particles, with each particle being a retro-reflector. The plurality forms a cloud having aerial buoyancy. The particles can be a corner reflector with adjacent sides substantially perpendicular to one another, and in particular a trihedral corner reflector. Alternatively, the particles can be lens reflectors, such as a cat's eye. In addition, chaff is provided for deployment from an aerial platform for retro-reflecting electromagnetic radiation projected to the platform. The chaff includes a plurality of retro-reflecting particles and a substrate. Each particle of the plurality is a retro-reflector. The substrate attaches the plurality of particles.

A display includes a source that establishes an exit pupil of far field content, a reconvergent sheet disposed along an optical axis to receive light of the far field content, the reconvergent sheet being configured to reconverge the far field content in position space, a reflective surface disposed along the optical axis for reflection of light of the position space back through the reconvergent sheet after reflection off of the reflective surface to re-form the exit pupil of the far field content, and a splitter disposed along the optical axis between the source and the reconvergent sheet and configured to redirect light exhibiting the re-formed exit pupil in a direction offset from the optical axis.

A system for imaging in the air including an image source, a transflector, and an retroreflective element. Light rays emitted by the image source are reflected by the transflector to irradiate on the retroreflective element, and are subjected to reflection on the retroreflective element, before being emitted along an original incident path in an opposite direction and being transmitted through the transflector to form a real image. By means of the present system, it is possible to directly present images in the air, even in vacuum, without the aid of any medium.

Embodiments of the disclosure provide a projection display apparatus comprising: a light source for emitting a light beam; a first light path configured to project the light beam emitted from the light source to a first display position; a second light path configured to project the light beam emitted from the light source to a second display position; a light patch switching device configured to switch the light beam emitted from the light source between the first light path and the second light path; and a light modulation device through which both the first light path and the second light path pass, wherein the light modulation device is configured to modulate the light beam passing therethrough to generate a display image.