A laser beam circulator includes a first mirror and a second mirror. The first and second mirrors are symmetric with respect to an axis therebetween. The circulator also includes a sample that is substantially planar. The axis extends through the sample. The sample is oriented at an angle with respect to a plane that is perpendicular to the axis. The angle is from about 0.1° to about 10°. The circulator also includes a laser configured to emit a laser beam that circulates multiple times from the second mirror to the sample to the first mirror and back to the second mirror. The laser beam passes through the sample during each circulation. The sample absorbs a portion of the laser beam each time the laser beam passes through the sample.

A freeform imaging system with a spectrometer and telescope components optically connected and optimized to increase the spectral and spatial resolution capabilities. Many embodiments of the system are capable of producing a spectral resolution of approximately 1 nm and a spatial resolution less than 30 m such that the imaging system can be used to accurately capture and measure point source plumes of various atmospheric gases including CH.sub.4, CO.sub.2, CO, N.sub.2O, and H.sub.2O.

A method of fabricating an optical assembly includes providing a first mold having a first curved mold surface; placing a substantially flat reflective polarizer; on the first curved mold surface and applying at least one of pressure and heat to at least partially conform the reflective polarizer to the first curved mold surface; providing a second mold comprising a second mold surface, the first and second mold surfaces defining a mold cavity therebetween; substantially filling the mold cavity with a flowable material having a temperature greater than a glass transition temperature of the reflective polarizer; and solidifying the flowable material to form a solid optical element bonded to the reflective polarizer. A maximum variation of an orientation of a pass polarization state across the bonded reflective polarizer is within about 3 degrees of a maximum variation of the orientation of the pass polarization state across the substantially flat reflective polarizer.

Optical systems including a partial reflector, a reflective polarizer, and a retarder disposed between the partial reflector and the reflective polarizer are described. The reflective polarizer is curved about two orthogonal axes and includes at least one layer that is substantially optically uniaxial at at least one location. The optical system is adapted to provide an adjustable focus.

A projection device includes: a plurality of light sources arranged in a first direction; a spatial modulation element that modulates incident light into image information and emits the image information; a lens that changes an optical path of light emitted from each of the plurality of light sources such that the light emitted from each light source reaches substantially the same region of an incident surface of the spatial modulation element; and a first reflective optical member that deflects the light emitted from the lens toward the spatial modulation element, the first reflective optical member having a shape that reflects light emitted from the lens so as to be incident on an arbitrary point on the incident surface of the spatial modulation element at a predetermined reference incident angle.

An optical system includes a partial reflector having an average optical reflectance of at least 30% in a desired plurality of wavelengths, a display panel disposed to emit image light toward the partial reflector, and a multilayer reflective polarizer disposed proximate the partial reflector. The multilayer reflective polarizer is curved about two orthogonal axes and includes at least one layer substantially optically uniaxial at at least one location. The image light is transmitted by the multilayer reflective polarizer after it is first reflected by the multilayer reflective polarizer. A quarter wave retarder may be disposed between the reflective polarizer and the partial reflector.

A lens has a first transmissive surface, a reflective surface, and a second transmissive surface sequentially arranged from a demagnifying side toward a magnifying side. The first transmissive surface and the reflective surface are located at the lower side of an imaginary axis extending in an axis-Z direction, and the second transmissive surface is located at the upper side of the imaginary axis. The reflective surface has a concave shape, and the second transmissive surface has a convex shape protruding toward the magnifying side. An imaginary line that connects an upper intersection to a lower intersection inclines with respect to an imaginary vertical line perpendicular to the imaginary axis in a plane YZ.

A projection device includes: a plurality of light sources arranged in a first direction; a spatial modulation element that modulates incident light into image information and emits the image information; a lens that changes an optical path of light emitted from each of the plurality of light sources such that the light emitted from each light source reaches substantially the same region of an incident surface of the spatial modulation element; and a first reflective optical member that deflects the light emitted from the lens toward the spatial modulation element, the first reflective optical member having a shape that reflects light emitted from the lens so as to be incident on an arbitrary point on the incident surface of the spatial modulation element at a predetermined reference incident angle.

A lens assembly includes a first optical element and a second optical element. The first optical element includes a flat partially reflective layer. The second optical element includes a curved reflective polarizer layer.

An attachment optical system is detachably attached to a magnification side of a projection optical system of a projection display device, and projects light emitted from the projection optical system on an imaging plane different from a magnification side imaging plane of the projection optical system. The attachment optical system includes an optical element having a second optical axis as an extension of a first optical axis of the projection optical system. The optical element has a plane of incidence on the second optical axis, a first reflecting surface that reflects light emitted from the plane of incidence, a second reflecting surface that reflects light reflected by the first reflecting surface, and an exit surface that transmits light reflected by the second reflecting surface. The first reflecting surface and the exit surface are continuous in an axial area where light passes the second optical axis and the first optical axis.