Colorlink, Inc.

Massachusetts Institute of Technology

Reald Inc.

Jonathan R Birge

Gary Dean Sharp

Michael Geraint Robinson

Jianmin Chen

Franz Xaver Kaertner

Richard Ell

Jainmin Chen

The phase spectrum of an ultrashort pulse is measured based on two-dimensional spectral shearing interferometry with zero delay. The measurement is performed utilizing an optical source pulse from which is extracted a short pulse and from which a chirped component is generated. The chirped component is split into first and second chirped pulses. The first and second pulses are then mixed with the short pulse in a nonlinear medium to produce up-converted and spectrally sheared copies of the first and second chirped pulses, which are measured in a spectrometer. A plurality of path lengths for the first second chirped pulses is provided to shift the relative phases of the first and second chirped pulses for additional measurements. The apparatus and methods are uniquely suited for characterizing single-cycle pulses.

Two-dimensional spectral shearing interferometry for ultrafast pulse characterization

A birefringent network can be formed from a pair of beam directing elements that sandwich a birefringent filter. One of the beam director elements can be a polarizing beam splitter and the other of the beam director elements can be a reflector or polarizing beam splitter. The polarizing beam splitters can be formed by an anisotropic material sandwiched between two isotropic pieces and can include optical films to couple both polarizations of light into and out of the beam splitters. The polarizing beam splitters also can be formed by anisotropic material on either side of an isotropic bow-tie piece, all of which is sandwiched a pair of isotropic pieces. A birefringent network also can be formed by a pair of bulk birefringent beam splitters sandwiching a birefringent filter. Little or no polarization mode dispersion occurs in these birefringent networks since all of the beams travel the same distances through the same elements.

Birefringent networks

The present application describes color management architecture for a three-panel projection system that utilizes color selective polarization filters (CSPF) and polarizing beam splitting elements. An exemplary embodiment describes a color management architecture with a dichroic input beam splitter and three polarizing beam splitters. An output polarizing beam splitter is used as an analyzer. The color management system architecture can isolate any color channel from those remaining whose separation and combination are then carried out by a single beamsplitting element. The disclosed embodiments also provide an improvement in the ANSI contrast. In some embodiments, an achromatic quarter-wave plate is used in combination with a color filter to block the light reflected from projection optics.

Three-panel color management systems and methods

Disclosed are color management architectures used in video projection systems including, for example, retarder stacks sensitive to the symmetries between input and output polarizer configurations that provide the polarization transformations that will comprise for skew rays, such that normal incidence performance is maintained for all incident light. Additionally, also disclosed are systems that utilize color selective polarization (CSP) filters and polarizing beam splitting elements such that an output analyzer is not required. One exemplary CSP architecture includes two CSPs, a single polarizing beam splitting element combination for splitting and combining light between two of the three panels, and an output polarizing beam splitting element used as an analyzer such that a single CSP is in the projection path. In all such architectures, an output CSP and clean up polarizer directly in line with the projection optics need not be included, thereby increasing transmission, improving imaging crispness, and reducing cost.

Compensated color management systems and methods

Beamsplitters are frequently used in projectors based on reflective liquid crystal display for separating input and output light, and more recently for color management systems. Rather stack filters are used in such systems to orthogonally polarize primary colors, converting polarizing beamsplitters to color splitters and combiners. Geometric polarization rotations induced by beamsplitters at moderate f-numbers have the effect of significantly degrading performance. Because retarder stacks in general rely on a specific input polarization to perform properly, such skew rays are responsible for color cross-talk. Retarder stacks designed according to the present invention are sensitive to the symmetries that exist between input and output polarizer configurations. These stacks provide the polarization transformations that will compensate for skew rays, such that normal incidence performance is maintained for all incident light.

Beamsplitters are frequently used in projectors based on reflective liquid crystal displays for separating input and output light, and more recently for color management systems. Retarder stack filters are used in such systems to orthogonally polarize primary colors, converting polarizing beamsplitters to color splitters and combiners. Geometric polarization rotations induced by beamsplitters at moderate f-numbers have the effect of significantly degrading performance. Because retarder stacks in general rely on a specific input polarization to perform properly, such skew rays are responsible for color cross-talk. Retarder stacks designed according to the present invention are sensitive to the symmetries that exit between input and output polarizer configurations. These stacks provide the polarization transformations that will compensate for skew rays, such that normal incidence performance is maintained for all incident light.

An optical system divides a light source into its component color bands red, green and blue by making the light travel different physical paths, at least two of these paths use stack retardation films and a polarization beamsplitter. By creating distinct paths, each code can be independently processed and combined to form a single path using a polarization splitter and retarder stack. The system preferably includes an input retarder that aligns a first spectrum of a light from a light source, along a first polarization state, and aligns a second spectrum of the light from the light source, along a second polarization state different than the first polarization state, and a beam splitting unit, optically coupled to the input retarder, and including a first beamsplitter that transmits the first spectrum, as a transmitted spectrum, and that reflects the second spectrum, as a reflected spectrum. The system also includes a first spatial light modulator optically coupled to the beam splitting unit, that alters and reflects the transmitted spectrum, as a modulated transmitted spectrum, towards the beam splitting unit, and a second spatial light modulator optically coupled to the beam splitting unit, that alters and reflects the reflected spectrum, as a modulated reflected spectrum, towards the beam splitting unit. The beam splitting unit combines the modulated transmitted spectrum and the modulated reflected spectrum into a combined spectrum.

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Cambridge, MA, United States of America

Jonathan R Birge