Abstract: The invention is an instrument for sensing the state of polarization (SOP), and for transforming the SOP of a beam of light from an incident continuously-varying arbitrary SOP to a desired exit SOP, using a polarization compensator under feedback control. A polarization sensor uses two or three samples of a beam to sense the Poincare sphere latitude and longitude error in SOP. A polarization controller adjusts the SOP of light, which is then sensed by the polarization sensor, which develops signals to drive the polarization compensator using feedback methods. Unlike prior-art systems, the feedback seeks a mid-point rather than an extremum in the sensed signals, so there is no sign ambiguity in the feedback control. Further, the sensor signals indicate orthogonal displacements in SOP that correspond to specific elements in the polarization controller, so there is no ambiguity as to which element needs adjustment in order to correct a given error in SOP.

Abstract: A liquid crystal cell assembly is described which eliminates high-order multiple-beam interference from reflections at the interfaces between the various elements. It can incorporate fixed retarders for compensation or production of high retardances. The invention enables standard, economical methods to be used in making the liquid crystal cell, retarder elements, optical coatings, and overall assembly. Transmissive and reflective embodiments are shown.

Abstract: A method for measuring sample retardance in the presence of spurious background retardance contributed by optical components such as strained lenses in the measurement system, which is accurate where there is a retardance in excess of 15 degrees in the sample, the background, or the combination thereof. The method can be applied to imaging systems that record polarized light intensities for obtaining retardance magnitude and angular orientation values at all points in a scene simultaneously. The system first takes images that record the apparent slow axis orientation and the apparent retardance of the sample at all image points. Then the sample is removed and images are taken that record the background retardance alone. Algorithms for minimizing the effect of the background retardance on the measured sample retardance make use of the separately measured polarized light intensities of sample with background and of the background alone.

Abstract: The invention is an instrument for sensing the state of polarization (SOP), and for transforming the SOP of a beam of light from an incident continuously-varying arbitrary SOP to a desired exit SOP, using a polarization compensator under feedback control. A polarization sensor uses two or three samples of a beam to sense the Poincare sphere latitude and longitude error in SOP. A polarization controller adjusts the SOP of light, which is then sensed by the polarization sensor, which develops signals to drive the polarization compensator using feedback methods. Unlike prior-art systems, the feedback seeks a mid-point rather than an extremum in the sensed signals, so there is no sign ambiguity in the feedback control. Further, the sensor signals indicate orthogonal displacements in SOP that correspond to specific elements in the polarization controller, so there is no ambiguity as to which element needs adjustment in order to correct a given error in SOP.

Abstract: A method in which a multiplicative ratio approach is used to remove the effects of the unwanted background fluorescence when making fluoroescence polarization (FP) measurements rather than the conventional subtractive approach, thus preserving both the precision and accuracy of the FP measurements, is disclosed. The method comprises selecting an appropriate multiplicative ratio, then calculating the selected multiplicative ratio using sample measurements. The calculated multiplicative ratio is multiplied by an appropriate value in a standard FP measurement equation or an appropriate value in an equation derived from a standard FP measurement equation. After this, the corrected FP measurement is calculated. When such multiplicative ratios are applied to the appropriate value or values in an FP measurement equation, the effects of background noise can be reduced without decreasing the precision of the FP measurements.

Abstract: An instrument is disclosed for fluorescence assays which is capable of reading many independent samples at the same time. This instrument provides enhanced throughput relative to single-sample instruments, and is well-suited to use in general fluorescence, time-resolved fluorescence, multi-band fluorescence, fluorescence resonance energy transfer (FRET), and fluorescence polarization. This invention is beneficial in applications such as high-throughput drug screening, and automated clinical testing. Also disclosed are means and methods for a fluorescence polarization measurement which is highly sensitive, inherently self-calibrated, and unaffected by lamp flicker or photobleaching. This fluorescence polarization invention can be practiced on a variety of fluorescence instruments, including prior-art equipment such as microscopes and multi-well plate readers.

Abstract: A birefringent interferometer system is described which uses nematic liquid crystal cells to produce variable optical path differences (OPD) between light of different polarization states that are interfered at a polarizing analyzer. Fixed retarders may also be incorporated to extend the range of OPD. The interferometer provides wide field-of-view, continuously variable path difference over a large range, and an on-board monitor of OPD for ensuring accurate settings of path difference, and hence, an accurate wavelength scale in the spectra produced by the apparatus. The system can further incorporate additional polarizing optics so it responds equally well to light of any incident polarization state without loss of efficiency.

Abstract: An imaging system is disclosed which provides means for obtaining images with essentially diffraction-limited spatial resolution, and can distinguish between several species of probes within a sample. It may be used with fluorescent, luminescent, up-converting reporter, quantum dot, and other types of probes. Two or more exposures are taken through a filter which expresses different filter states, one of which is preferably a relatively neutral state with high transmission for all wavelengths of interest, and the others of which provide predetermined variation in transmission that are preferably sloping or periodic in wavelength. The probe species is identified by the ratio of response at the various filter settings.

Abstract: An imaging system is disclosed comprising an illuminator which produces illumination of any desired pure wavelength or of any selected mixture of pure wavelengths simultaneously, which illuminates a sample without spatio-spectral artifacts using illumination optics designed for that purpose; imaging optics, which form an image of the sample at a detector or viewing port; and a detector. This enables imaging the complete spectral image cube for a sample by taking sequential images while illuminating with a series of pure wavelengths, with greater ease and economy than by means of tunable filters, interferometers and the like. It further enables imaging while the sample is illuminated with a precisely controlled mixture of illuminant wavelengths, so that the image presented to the detector is a linear superposition of the sample properties at many wavelengths.

Abstract: The invention is an instrument for sensing the state of polarization (SOP), and for transforming the SOP of a beam of light from an incident continuously-varying arbitrary SOP to a desired exit SOP, using a polarization compensator under feedback control. A polarization sensor uses two or three samples of a beam to sense the Poincare sphere latitude and longitude error in SOP. A polarization controller adjusts the SOP of light, which is then sensed by the polarization sensor, which develops signals to drive the polarization compensator using feedback methods. Unlike prior-art systems, the feedback seeks a mid-point rather than an extremum in the sensed signals, so there is no sign ambiguity in the feedback control. Further, the sensor signals indicate orthogonal displacements in SOP that correspond to specific elements in the polarization controller, so there is no ambiguity as to which element needs adjustment in order to correct a given error in SOP.

Abstract: An imaging system is disclosed comprising an illuminator which produces illumination of any desired pure wavelength or of any selected mixture of pure wavelengths simultaneously, which illuminates a sample without spatio-spectral artifacts using illumination optics designed for that purpose; imaging optics, which form an image of the sample at a detector or viewing port; and a detector. This enables imaging the complete spectral image cube for a sample by taking sequential images while illuminating with a series of pure wavelengths, with greater ease and economy than by means of tunable filters, interferometers and the like. It further enables imaging while the sample is illuminated with a precisely controlled mixture of illuminant wavelengths, so that the image presented to the detector is a linear superposition of the sample properties at many wavelengths.

Abstract: A liquid crystal cell assembly is described which eliminates high-order multiple-beam interference from reflections at the interfaces between the various elements. It can incorporate fixed retarders for compensation or production of high retardances. The invention enables standard, economical methods to be used in making the liquid crystal cell, retarder elements, optical coatings, and overall assembly. Transmissive and reflective embodiments are shown.

Abstract: An apparatus for performing fluorescence detection of two or more biochemical probes and/or fluorescence measurement of fluorescence intensity at two or more spectral bands of light emitted from at least one sample spot is disclosed. The apparatus simultaneously directs emitted fluorescent light from multiple probes and/or at multiple spectral bands to different spots on a single pixelated detector.

Abstract: A sample having a plurality of probe molecules is illuminated with at least one beam of excitation light that is linearly polarized along a first axis, thereby effecting fluorescence emission in a plurality of spectral bands. The intensity of a first component of fluorescence emission that is polarized along the first axis, as well as the intensity of a second component of fluorescence emission that is polarized along an orthogonal second axis, is measured for each of said plurality of spectral bands. These measurements are represented as a measurement vector M. Since each probe emits some limited amount of light in the characteristic band of another probe, this results in cross-talk between probes. The measurement vector is therefore corrected using an instrument response matrix A, which is generated by measuring the flux output of control samples which each have only a single probe species.

Abstract: An improved optical polarization switch which provides a wide field-of-view and achromatic action. Two liquid crystal cells are used and are selectively operated in a preferred embodiment to provide three distinct optical states. Interposed between the two nematic liquid crystal cells is a compensating member such as an half-wave retarder or an optical rotator. Such switches are of utility in shutter applications and in high-performance field-sequential color filters.

Abstract: A liquid crystal cell is described which includes adaptive means to relieve hydrostatic pressure and means for restraining the aperture portion of the cell, and which may be assembled together with thick members such as precision windows, or may be built into optical assemblies incorporating several cells placed optically in series, such as tunable filters or multiple-cell optical switches, without defeating the pressure-relief mechanism.

Abstract: A fluorescence imaging system for epi-illumination wherein the usual dichroic beamsplitter is replaced by a polarizing beamsplitter (PBS). The sample is excited with light that is linearly polarized to a significant degree, and fluorescent emission light is collected in the orthogonal linear polarization state. Excitation light that is scattered or reflected by the sample is rejected by the PBS, while the desired emission light is captured for imaging by a detector. By eliminating the usual dichroic beamsplitter member, the imaging system removes the barriers to multi-spectral imaging that such members conventionally impose.

Abstract: A switchable optical birefringent filter for polarized light incident thereon includes first and second retarder networks in optical series and a switch associated with at least one of the first and second retarder networks for selectively altering one of the polarization state and the angular orientation of the polarization state relative to the angular orientation of the second network, of light as it is received by the second network. In one operating mode, the filter produces a spectral filtration of light passing through the filter and in another mode transmits all light within a specified range of wavelengths without significant alteration.

Abstract: A color filter having an optical switch element located between a neutral linear polarizer and a second color-selective linear polarizer, followed by one or more optical retarders and a second neutral linear polarizer. When a second optical switch element is incorporated, three color states are produced. The filter may also comprise a guest host type cell as the optical switch element. The resulting color filter exhibits high performance both for on-axis and off-axis rays and can be designed to produce a wide range of colors.

Abstract: A liquid crystal device which uses parallel transparent plates having a nematic crystal material which is free of chiral or twisting additives positioned therebetween. The device applies an AC carrier modulated signal to establish an electric field across the material, the modulation level thereof controlling the state of the directors thereof over a range from a selected partially driven state to a fully driving state. The device can be used in a system to measure and to control the retardance of the device and in systems for controlling the intensity of light being transmitted through the device. The devices can further be used in a system to provide a birefringent filter.