A retroreflecting display that enables the formation of a real image in free space includes a first light source that generates a first light output; a first beam splitter module; and a retroreflector module opposite the first light source.

A polarization modulator for stereoscopic projection comprises a polarization beam splitting prism assembly for splitting an incident beam into a transmitted beam, an upper half of reflected beam, and a lower half of reflected beam, a polarization plane rotating component for rotating the polarization plane of the transmitted beam or of the upper half of reflected beam and the lower half of reflected beam by 90 degrees, a reflective mirror for adjusting a propagation direction of the upper half of reflected beam and the lower half of reflected beam, a lens group for adjusting the range of size of the transmitted beam, a linear polarizer for filtering the beam, a polarization modulator for modulating the transmitted beam, the upper half of reflected beam and the lower half of reflected beam into counter-clockwise circularly polarized light and clockwise circularly polarized light in the order of frames, and a driving circuit.

A polarization modulator for stereoscopic projection comprises a polarization beam splitting prism assembly for splitting an incident beam into a transmitted beam, an upper half of reflected beam, and a lower half of reflected beam, a polarization plane rotating component for rotating the polarization plane of the transmitted beam or of the upper half of reflected beam and the lower half of reflected beam by 90 degrees, a reflective mirror for adjusting a propagation direction of the upper half of reflected beam and the lower half of reflected beam, a lens group for adjusting the range of size of the transmitted beam, a linear polarizer for filtering the beam, a polarization modulator for modulating the transmitted beam, the upper half of reflected beam and the lower half of reflected beam into counter-clockwise circularly polarized light and clockwise circularly polarized light in the order of frames, and a driving circuit.

A photogrammetry system includes a photogrammetry rig and a plurality of cameras. The photogrammetry rig includes a support frame and a plurality of support arms. The support frame includes a plurality of joint members and a plurality of struts each extending between two of the plurality of joint members to collectively form a spherical polyhedron shape having a center focal point. Each of the plurality of support arms extends through a different one of the plurality of joint members in a direction following a different radial ray from the center focal point. Each of the plurality of support arms is selectively, linearly slidable and securable relative to the different one of the joint members along the different radial ray between a position closest to the center focal point and a different position farthest away from the center focal point. Each camera of the plurality of cameras is secured to an end of a different one of the plurality of support arms nearest the center focal point within the spherical polyhedron shape.

A photogrammetry system includes a photogrammetry rig and a plurality of cameras. The photogrammetry rig includes a support frame and a plurality of support arms. The support frame includes a plurality of joint members and a plurality of struts each extending between two of the plurality of joint members to collectively form a spherical polyhedron shape having a center focal point. Each of the plurality of support arms extends through a different one of the plurality of joint members in a direction following a different radial ray from the center focal point. Each of the plurality of support arms is selectively, linearly slidable and securable relative to the different one of the joint members along the different radial ray between a position closest to the center focal point and a different position farthest away from the center focal point. Each camera of the plurality of cameras is secured to an end of a different one of the plurality of support arms nearest the center focal point within the spherical polyhedron shape.

A method of using a photogrammetry system to produce a three-dimensional image representation includes placing an object in the photogrammetry system, illuminating only a plurality of polarized lights, capturing a polarized image capture set of the object using a plurality of cameras while only the plurality of polarized lights are illuminated, and sending the polarized image capture set to the at least one computer processor. The method further comprises illuminating only a plurality of non-polarized lights, capturing a non-polarized image capture set of the object from the plurality of cameras while only the non-polarized lights are illuminated, and sending the non-polarized image capture set to the at least one computer processor. The method still further comprises using the at least one computer processor to generate a three-dimensional image representation of the object includes comparing the polarized image capture set and the non-polarized image capture set.

A method of using a photogrammetry system to produce a three-dimensional image representation includes placing an object in the photogrammetry system, illuminating only a plurality of polarized lights, capturing a polarized image capture set of the object using a plurality of cameras while only the plurality of polarized lights are illuminated, and sending the polarized image capture set to the at least one computer processor. The method further comprises illuminating only a plurality of non-polarized lights, capturing a non-polarized image capture set of the object from the plurality of cameras while only the non-polarized lights are illuminated, and sending the non-polarized image capture set to the at least one computer processor. The method still further comprises using the at least one computer processor to generate a three-dimensional image representation of the object includes comparing the polarized image capture set and the non-polarized image capture set.

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.