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 of measuring the thickness of a cell gap of a reflective type liquid crystal display. An optical system having a rotating table, an input polarizer, a beam splitter, and a output polarizer is used. A reflective type liquid crystal device is disposed on a rotating table. An incident light is reflected by the liquid crystal device. The reflective type liquid crystal device is located between the input polarizer and the output polarizer. A beta angle &bgr; is defined as the angle between the input light polarization and the front liquid crystal director. A first formula is used to express the relationship between the reflectivity R⊥ and &bgr;. The reflectivity is R⊥ then differentiated by &bgr; to obtain a second formula that express the relationship between &bgr;max and the thickness of the cell gap. The rotating table is rotated to measure the maximum value &bgr;max of the angle &bgr;. The thickness d can thus be obtained more precisely.

Abstract: A method and apparatus for characterizing and screening an array of material samples is disclosed. The apparatus includes a sample block having a plurality of regions for containing the material samples, a polarized light source to illuminate the materials, an analyzer having a polarization direction different than the polarization direction of the polarized light source, and a detector for analyzing changes in the intensity of the light beams. The light source, together with a polarizer, may include a plurality of light beams to simultaneously illuminate the entire array of materials with linearly polarized light so that characterization and screening can be performed in parallel. In addition, the materials in the sample block maybe subjected to different environmental conditions or mechanical stresses, and the detector analyzes the array as a function of the different environmental conditions or mechanical stresses.

Abstract: Disclosed are spectrophotometer, polarimeter, and ellipsometer systems which have multiple easily, sequentially, positionable detector systems therein mounted to allow easy positioning thereof, to for instance, allow sequential monitoring of ellipsometric and spectrophotometric signals, without removal of any detector system from the spectrophotometer, polarimeter, or ellipsometer system. Also disclosed are methods of use wherein-different detectors in a positionable multiple detector containing system are utilized during different electromagnetic beam detection steps.

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: A mixing apparatus for and a method of supplying a mixture having a required homogeneity, the mixing apparatus comprising: a mixing device (1; 101) for mixing a plurality of materials, the mixing device (1; 101) including a mixing vessel (7; 107) and having at least one inlet port (8, 9; 108, 109, 110) and an outlet port (11; 111); a supply line (19; 119) connected to the outlet port (11; 111) of the mixing device (1; 101); and at least one measuring device (23, 25, 27; 123, 125, 127) for measuring on-line at at least one point in the supply line (19; 119) the composition of the mixed material passing in use through the supply line (19; 119).

Abstract: A circular dichroism spectrometer eliminates linear birefringent interference by having a first polarization modulator before the sample and a second polarzation modulator after the sample. The two polarization modulators vibrate at different frequencies so the signals can be distinguished and manipulated. The addition of the second polarization modulator, an additional lock in amplifier, and software to manipulate the two signals corresponding to the two vibrational frequencies allow a real time circular dichroism spectra free from interference to be determined.

Abstract: A transparent flow channel fluidly communicates a fluid source and a collection reservoir. An interrogating light beam passes through a first polarizer having a first plane of polarization. The flow channel is orthogonal to the light beam. The light beam passes through a fluid sample as it flows through the flow channel, and is then filtered through a second polarizer having a second plane of polarization rotated 90° from the first plane of polarization. An electronic photo-detector is aligned with the light beam, and signals the presence of birefringent microcrystals in the fluid sample by generating voltage pulses.

Abstract: Tuning to maximize the isolation provided by an optical isolator to one of a predetermined plurality of wavelengths is achieved by tilting the isolator with respect to an input beam of light. Further tuning to a peak response for a given wavelength is achieved by rotation of the isolator about its longitudinal axis while or after tilting. In the manufacture of the isolator a test beam is launched into an output port end directed toward the input end. Tilting, or tiling and rotating is initiated and light at the input end is measured while tilting/rotating. When the position is determined where the minimal amount of light is measured, the optical elements are glued or secured in place, thereby providing a way to alter the response of an isolator for a given wavelength of input light.

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: Methods and devices are provided for quickly producing all possible linear polarization states of light at the output of a length of optical fiber. Linearly polarized light is input and is transmitted through a fiber. Due to the birefringence of the fiber, light at the output of the fiber is elliptically polarized irrespective of the input polarization. The elliptically polarized states of light at the output are generated as an arbitrary circle on an output Poincare sphere. This arbitrary circle is then manipulated to produce a final circle substantially coinciding with the equator of the Poincare sphere. This final circle represents all possible linear polarization states at the output of the fiber. The invention eliminates the need for determining transformation matrices and performing point-by-point calculations in order to obtain input polarization settings for polarization-based, passive optical network (“PON”) testing.

Abstract: Improvements in accuracy and sensitivity in mechanical-optical metrology apparatus are achieved through the use of a value for angle of incidence that is an average of positive and negative values for different arrangements of the metrology apparatus. In the ellipsometry type of metrology the average value for angle of incidence is established by using one of a reversal of light beam direction, the providing of a separate light beam mounting arm and the mechanical rotation of the sample.

Abstract: An optical assaying method and system having a movable sensor is described. In one aspect, the present invention is a sensing system having a rotating sensor disk coated with indicator dyes sensitized to a variety of substances. In this configuration the sensing system further includes a detector for sensing spectral changes in light received from one or more of the indicator dyes. In another aspect, the present invention is a sensing system having a surface plasmon resonance sensor disk having grooves extending radially from a center of the disk. In yet another aspect, the present invention is a sensing system including a diffraction anomaly sensor disk having a dielectric layer that varies in thickness. The present invention allows for construction of an inexpensive sensing system that is capable of easily detecting a variety of substances either in a sample or a surrounding environment.

Abstract: A micropolarimeter and ellipsometer for obtaining complete optical information of superficially illuminated specimens. A compact construction is designed to facilitate their use. To obtain the simultaneous surface measurement of all optical information from a specimen, the retarder of the micropolarimeter consists of a one-piece retarder array with at least one pixel group, in which the major axis orientations of the individual pixels are distributed over an angular range of 360°. This micropolarimeter can be integrated into the reflected light microscope of an ellipsometer. The result is a compact measurement unit.

Abstract: The invention concerns a micropolarimeter comprising an analyzer (1) and a detector (10) located past the analyzer in the direction of radiation and presenting a number of segments ND which is higher than or equal to 3 (11). The invention seeks to provide a micropolarimeter with no moving parts, with a high polarization index, for use for polychromatic light, so small that it can detect the ray of common lasers in one single measurement step without it being necessary to enlarge it, and capable of being converted in a simple manner into a complete Stokesmeter.

Abstract: The present invention allows quickly, simply, precisely and with high sensitivity to determine the presence and concentration of any biologically active substances capable to interact with linear double-stranded DNA molecules in any liquids including biological liquids.

Abstract: An in-line optical fiber polarimeter comprises a plurality of fiber gratings and a single wave plate, disposed sequentially along a length of optical fiber. The fiber gratings are precisely oriented and have a predetermined grating period such that each grating functions to out-couple a predetermined portion of the optical signal passing through the polarimeter. A separate detector is associated with each grating to measure the out-coupled signal. The four Stokes parameters can be determined from the set of measurements and then used to determine to state of polarization of an optical signal passing through the polarimeter.

Abstract: A readhead for a spectrometer for illuminating a target area and receiving light from said target area is provided with a housing adapted to be incorporated in a spectrometer, a light source mounted in a fixed position relative to the housing, a support mechanism adapted to support a biological sample to be illuminated by the light source, a light-shaping mechanism disposed between the light source and the support for increasing the diameter, intensity, and uniformity of the light beam, and a photodetector mounted in fixed position relative to the housing, the photodetector being adapted to detect light from a biological sample disposed in the target area illuminated light sources. The light sources may be in the form of a light-emitting diode that emits substantially monochromatic light having a first wavelength, and the readhead may also include a second light-emitting diode that is adapted to emit substantially monochromatic light of a second wavelength towards the target area.

Abstract: An ellipsometer for evaluating a sample includes a light generator that generates a beam of light having a known polarization for interacting with the sample. A polarimeter of the ellipsometer includes a compensator, an analyzer and a detector. The compensator is formed of an optically uniaxial material. The compensator has a planar front face, and a planar rear face that is substantially parallel to the front face. The compensator is configured such that one ordinary axis of the crystal, but not the second ordinary axis of the crystal, lies in the plane of the front face. The compensator is positioned in the path of the light beam such that the light beam is normally incident to the front face of the compensator. As such, the ordinary ray is not displaced as it passes through the compensator. The ellipsometer further includes means for rotating the compensator about an axis that is perpendicular to both the front face and to the rear face.

Abstract: A polarimeter includes a prism (32) for separating the incident light beam (21) having a Stokes vector (S) into a reflected beam (22) and a transmitted beam (23), the prism not inducing any interferential effect and the transmitted beam being subjected to at least a reflection internal to the prism. The polarimeter also include two final separators (3, 4) for separating respectively each of the reflected beam and the transmitted beam into at least two final beams (25-28), detecting means (5-8) for measuring the intensity levels of the final beams and a processing unit (9) producing the Stokes vector of the light to be measured. Preferably, the reflections internal to the prism (32) are either total reflections, or reflections on a thick absorbing layer. The invention also includes a method for measuring light beam polarization states.

Abstract: A method and apparatus for characterizing and scanning an array of material samples in a combinatorial library in parallel is disclosed. The apparatus includes a sample block having a plurality of regions for containing the material samples, a polarized light source to illuminate the materials, an analyzer having a polarization direction oriented 90.degree. relative to the polarization direction of the polarized light source so as to filter out light intensities having the same polarization direction as the incident light beams from the light source after illuminating the material samples, and a detector for analyzing changes in the intensity of the light beams. In one aspect, the light source in combination with a polarizer, includes a plurality of light beams to simultaneously illuminate the entire array of materials with linearly polarized light such that the characterization can be performed quickly.

Abstract: The object of the present invention is to measure the amount of birefringence of a target while enhancing spatial resolution. A birefringence measurement optical system is comprised of a Stabilized Transverse Zeeman Laser emitting laser beam in a predetermined polarization state toward a target, a halfwave plate (polarized light emission optical system), a linear polarizer (polarized light detection optical system) detecting information on the retardation, main axial direction and optical rotation angle of the target as a light signal which can be polarimetrically analyzed through the target, and a photo detector converting the light signal from the linear polarizer into an electric signal and detecting the electric signal. An optical fiber (light transmission path) taking out part of light fluxes of the light signal and optically transmitting the part of the light fluxes from the target toward the photo detector, is arranged between the photo detector and the target.

Abstract: An optical-fiber polarimetric sensor for measuring the displacement of an object relative to a frame, the sensor comprising a measurement optical fiber secured, over a fraction of its length, both to a central point of the object and to first and second fixed points of the frame, means disposed at one end of the measurement fiber and serving to emit a light beam of determined polarization into said measurement fiber, means for exerting twist on the measurement fiber so as to modify the polarization of the light beam, and means disposed at another end of the measurement fiber and serving firstly to detect the resulting light beam and secondly to determine the displacement of the object by analyzing the polarization modified in this way, wherein said measurement fiber is stripped, over said fraction of its length, of the covering that imparts mechanical strength thereto, and it is slid into a deformable guide sheath fixed both to the rotary object and also to the frame.

Abstract: An apparatus and a method for transfusing liquid specimen for an optical characteristic measurement, which is excellent in operability and handling, and capable of introducing a liquid specimen into a sample cell without detaching the cell from an optical characteristic measurement apparatus and without bubbling, as well as a polarimeter are disclosed. According to the present invention, the specimen can be introduced into the sample cell without detaching the sample cell from the equipment, in a way of connecting the bottom of the sample cell with a reservoir for temporarily accommodating the liquid specimen through a tubular path, then varying a difference in the levels of the sample cell and the reservoir, or a way of using a syringe arranged in the tubular path. At expelling the specimen from the sample cell, the specimen is transfused into the reservoir in a similar manner.

Abstract: An apparatus and method measures and controls crosslinking treatments on a glass surface from the measurement of reflection of polarized radiation from the surface of the glass.

Abstract: Provided is a polarization characteristic measuring method and apparatus for accurately measuring a polarization characteristic of fluorescence or Raman-scattered light emitted when a sample is exposed to light. The sample is exposed to excitation light radiated from a pulsed excitation light source and converted to p-polarized light by polarizer and half-wave plate, and photodetectors measure an intensity I.sub.pp of a p-polarized component and an intensity I.sub.ps of an s-polarized component of fluorescence emitted from the sample under irradiation with the excitation light. In similar fashion, the sample is exposed to the excitation light of s-polarized light and the detectors measure an intensity I.sub.sp of a p-polarized component and an intensity I.sub.ss of an s-polarized component of fluorescence emitted from the sample under irradiation. From these measured values, G factor is calculated according to the following equation:G=[(I.sub.pp .multidot.I.sub.sp)/(I.sub.ps .multidot.I.sub.ss)].sup.

Abstract: A device for measuring birefringence in an optical data carrier has a laser light source with a polarization modifier, a beamsplitter, a polarizer, a photodetector, and a controller operatively connected to the photodetector. The laser light source illuminates various spots on the optical data carrier by means of a laser beam. The photodetector receives a reflected laser beam, converts it into an electric signal and supplies this signal to the controller, which determines a value for the birefringence in the illuminated spot on the optical data carrier. Furthermore, the device is provided with a transparent reference element with known birefringence properties, a mirror, and for directing the laser beam towards the reference element in a first calibration position; directly towards the mirror in a second calibration position; and towards the optical data carrier during non-calibration time.

Abstract: An apparatus and method for recording spatially dependent intensity patterns of polarized light that is diffusely backscattered from highly scattering media are described. These intensity patterns can be used to differentiate different turbid media, such as polystyrene-sphere and biological-cell suspensions. Polarized light from a He-Ne laser (.lambda.=543 nm) is focused onto the surface of the scattering medium, and a surface area of approximately 4.times.4 cm centered on the light input point is imaged through polarization analysis optics onto a CCD camera. A variety of intensity patterns may be observed by varying the polarization state of the incident laser light and changing the analyzer configuration to detect different polarization components of the backscattered light.

Abstract: A method of determining a parameter of a liquid crystal cell is provided in which parameters, such as the thickness of the liquid crystal layer and the angle of the twist of liquid crystal molecule orientation in the liquid crystal cell, are accurately determined in a short time with a simple apparatus. Light from a light source 1 is transmitted through a polarizing plate 2 and incident to a liquid crystal cell 3. The light is transmitted by a polarizing plate 4 and the intensity of the transmitted light is measured by a photodetector 6.

Abstract: Disclosed is dual-polarizer based system, and method for continuously monitoring the "total film retardance" of a birefringent film, where "total film retardance" is defined as the product of the difference in the indicies of refraction in the two directions of refringence in said film, multiplied with film thickness. The preferred embodiment involves the application of Fourier analysis to signals which pass through the system and a birefringent film therein, to provide a spectrum, changes in which are indicative of changes in monitored "total film retardance". The present invention allows real time monitoring of birefringent films during manufacture thereof, and, hence, via a control system, control of film manufacturing process parameters to the end that produced films present with a relatively more consistent thickness than is the case where the present invention is not utilized.

Abstract: Methods and devices for determining the identity and concentration of constituent compounds within a test specimen. The methods are based on the principle that a specific compound in a specific concentration will modify a pattern of incident polychromatic light in a manner that is recognizable. The system includes a polychromatic light source directed first through an incident light pattern generator and then through the test specimen. Reflected and transmitted light components then pass through a pattern recognition gating device that selects portions of the light for analysis by an array of detectors. The methods include producing a modulated pattern of incident light specific for a particular compound of interest and selectively analyzing the reflected or transmitted light according to known patterns for that compound in specific concentrations.

Abstract: A system and apparatus for the measurement of absolute biaxial birefringence of plastic materials is described. The materials which must be at least partially transparent can be constituted of one or several similar or dissimilar layers. In the latter case, the birefringence of each material can be determined. The technique uses a multiwavelength white light source that provides at least two beams projected at different angles of incidence on the sample. The beams pass through first polarizers before they are incident on the sample and through second polarizers after they have passed through the sample. The beams are then directed to a detector for measuring each beam intensity or transmittance as a function of wavelength for the incident angles at different times, and are analyzed using nonlinear regressions to determine retardation. By the knowledge of the thickness of the material, the absolute biaxial birefringences are calculated for any specific wavelength.

Abstract: The circumferentially isotropic phase plate of the present invention includes (i) a plurality of first material layers which are formed by a first material on a transparent substrate and disposed in concentric circles around a predetermined axis within a plane orthogonal to an incident direction of a bundle of rays and (ii) a plurality of second material layers which are formed by a second material having a refractive index different from that of the first material and disposed in concentric circles around the predetermined axis so as to fill a space between the plurality of the first material layers, wherein the plurality of the first and second material layers are formed such that each layer thickness along the incident direction of the bundle of rays becomes uniform along a circumferential direction of the concentric circles, thereby constituting, as a whole, a form birefringent body which is isotropic in the circumferential direction of the concentric circles.

Abstract: A liquid crystal (LC) polarization modulator segment (216, 218) includes a monitoring device (220). The monitoring device (220) includes a polarized reference light source (222), located at an LC polarization monitor input, and polarized light detector (224), located at an LC polarization monitor output. If the reference light having the correct polarization is received at the detector (224), an indication of the switch state is provided. Alternatively, if the polarized detector (224) includes orthogonal polarizers (230A, 230B) provided for two separate light detectors (232A, 232B) both the desired polarization, and the opposite polarization, may be monitored to determine whether a failure exists in the segment. If the reference light is detected having the opposite polarization (instead of or in addition to the correct polarization) or no light is detected, the segment (or the monitor) is not operating correctly.

Abstract: The present invention discloses a mask defect inspection apparatus for optically detecting a defect on a mask having a circuit pattern, which comprises an illumination system for illuminating the mask with inspection light; a first light receiving optical system for receiving the inspection light reflected by the mask; a second light receiving optical system for receiving the inspection light transmitted by the mask; a first spatial filter for shielding the inspection light passing through a central region including the optical axis of the first light receiving optical system in an optical Fourier transform plane for the circuit pattern in the first light receiving optical system; a second spatial filter for shielding the inspection light passing through a central region including the optical axis of the second light receiving optical system in an optical Fourier transform plane for the circuit pattern in the second light receiving optical system; a first detector for photoelectrically converting the inspecti

Abstract: A magneto-optic characteristic measuring device which is adapted to measure a Kerr rotation angle is a kind of magneto-optic characteristic exhibited in materials used for magneto-optic recording media. Known materials exhibiting a magnetic Kerr effect have very small Kerr rotation angle ranging from about 0.1.degree. to about 0.5.degree.. As a result, it is difficult to accurately measure such a small Kerr rotation angle using known measuring devices due to an influence caused by noise components. In the magneto-optic characteristic measuring apparatus, its electronic circuit unit, which serves to magneto-optically modulate a laser beam from an optical unit introduced in a beam splitter via a polarizer and to record the modulated beam in an X-Y recorder using a detect signal from an optical detector unit, includes a lock-in amplifier,.thereby accurately measuring a small Kerr rotation angle.

Abstract: Disclosed is a system, and regression-based method utilizing optical data, for use in identifying material systems which have been cut to have an optical axis oriented as desired with respect to a alignment surface. The present invention is particularly well suited to qualification of material systems such as optical compensators and retarders, which ideally have an optical axis oriented perpendicular to, or parallel to, an alignment surface.

Abstract: An all fiber-optic in-line photopolarimeter is disclosed. This photopolarimeter replaces the conventional 1.times.2 coupler, bulk beamsplitter and accompanying optics with a single 1.times.5 star coupler. This system can measure state of polarization of light in a fiber in situ.

Abstract: The present invention is applicable generally to Spectroscopic Rotatable and Rotating Element Ellipsometers which utilize a relatively large range of wavelengths. Disclosed is a system and method for controlling the polarization state of a polarized beam of light so that it is in a range where the sensitivity of a Polarization State Detector used to measure changes in said polarized beam of light resulting from interaction with a Sample System, to noise and measurement errors etc., is reduced. Exemplified is a system, and method of use, for simultaneously setting both measured ellipsometric ALPHA, and ellipsometric BETA parameter values, (or equivalents), within ranges, in which ranges the sensitivity of transfer functions, and mathematical regressions which utilize said ellipsometric ALPHA and ellipsometric BETA values in the calculation of sample system characterizing PSI and DELTA constant values, to noise and errors in measurement etc., is found to be negligible.

Abstract: A method and system are provided for reliably detecting localized birefringence defects of an object such as an optical media substrate in a dynamic local birefringence field created during cooling of the optical media substrate at an inspection station. A birefringence digital filter filters out high frequency defect data while eliminating background birefringence data in a digital image created by a camera adapted to respond to the birefringence of the optical media substrate under control of a computer. Resulting filtered high frequency defect data is then processed to determine the localized birefringence defects in real-time. In one embodiment, the birefringence digital filter includes an addressable storage device such as a PROM which stores a lookup table which is able to produce filtered data in real-time at a data rate in excess of 8 million pixels per second.

Abstract: An ellipsometer comprising several photodetectors and an electronic processing unit (4) produces a beam of light modulated at a modulation frequency (Fm) which is reflected by a sample. The photodetectors measure fluxes from parts of the reflected luminous beam, producing measured analog signals in input channels (6), and the electronic processing unit (4) calculates physical parameters of the sample. This electronic processing unit (4) comprises a multiplexing and digitizing unit (7) successively switching to the input channels (6) at a switching frequency (Fe) and a sequencer (19). The sequencer (19) comprises means (24, 35) to allow setting the switching frequency (Fe) as a multiple of the modulation frequency (Fm). The ellipsometer takes optical measurements in real time, in particular for depositing films on substrates.

Abstract: An optical frequency shifter is provided to change the frequency of a coherent input light beam by imparting periodic increases in phase to the beam. This increase in phase is caused by ferroelectric liquid crystals (FLCs) in conjunction with quarter wave plates. The FLCs are repeatedly switched on and off by electrical signal generators, adding phase shift in steps, which in turn results in a higher output optical frequency.

Abstract: A method for determining polarization profiles of individual wavelengths hin a polychromatic source utilizes a variable filter system comprised of a retarder and a linear polarizer. Polychromatic light from the source is transmitted through the system and exits therefrom with attenuated intensities unique for each wavelength of the light. The attenuated intensities are recorded by a spectroradiometer and used to calculate Stokes parameters for each wavelength. The inherent problem of the retarder introducing a different phase differential for each individual wavelength transmitted therethrough is solved by expressing the Stokes parameters explicitly as a function of wavelength. The primary purpose of the method is to obtain the four Stokes parameters for individual bands of wavelength within a polychromatic light beam.

Abstract: A liquid crystal layer is interposed between two polarizers arranged in a parallel Nicol or crossed Nicol manner, and a phase plate is set between two polarizers so that the transmission direction of the first polarizer coincides with the optical axis. Then, a rotation angle at which optical intensity transmitted through the second polarizer has an extreme value to be determined, and the thickness of the birefringence layer is calculated according to the rotation angle of the phase plate. In a different method, a half-wave plate is used. First, the liquid crystal layer is set at a position where an optical intensity of the transmission light has an extreme value, and the half-wave plate provided between the two polarizers is set so that a transmission direction of the first polarizer coincides with the optical axis. Then, a rotation angle of the phase plate is determined at which an optical intensity of light transmitted through the second polarizer has an extreme value.

Abstract: A Voigt optical filter. Crossed polarizers are provided at the entrance and exit of a vapor cell continuing an alkali metal vapor. A magnet provides a magnetic field at 90.degree. with the axis of the cell and 45.degree. with each polarizer direction. The only light which passes through the filter is light within a narrow frequency band near the atomic transitions (absorption peaks) of the alkali metal vapor.

Abstract: An apparatus comprising an optical filter which resolves electromagnetic radiation into a sequence of resolved polarization components. The apparatus is also comprised of an imaging device having a storage device. The imaging device is disposed adjacent to the optical filter to receive the sequence of resolved polarization components from the optical filter and store them in the storage device for subsequent processing. The present invention pertains to an apparatus for viewing. The apparatus comprises a frame. The apparatus also is comprised of a first optical filter mounted on the frame to cover one eye of a viewer when the viewer wears the frame. The first optical filter resolves electromagnetic radiation into a sequence of resolved polarization components so the viewer can view the sequence of resolved polarization components. The present invention also pertains to an apparatus for viewing. The apparatus is comprised of a housing.

Abstract: A sample system investigation system, such as an ellipsometer or polarimeter system, for use in investigating sample systems with electromagnetic wavelengths in the infrared range, and a calibration method for compensating nonidealities in multi-dimensional system rotated and non-rotated component representing matricies, are disclosed. An essentially achromatic compensator of dual-rhomb construction, which introduces a (3*LAMBDA/4) phase shift, but essentially no deviation in the direction of propagation of a polarized beam of electromagnetic wavelengths caused to pass therethrough, even when said compensator is caused to continuously rotate, is also disclosed.

Abstract: A sorting system (10) propels a stream of randomly arranged PET and PVC articles (12, 14) through an inspection zone (20) including a first light polarizer/analyzer combination (24, 26), an article-detecting gap (G), and a second light polarizer/analyzer combination (28, 30). The first and second polarizer/analyzer combinations are oriented to extinguish normally incident light in the absence of articles in the inspection zone and are offset 45 degrees relative to each other such that at least one polarizer/analyzer combination detects a principal axis of birefringence of PET articles. The gap is employed to detect the presence of an article in the inspection zone. A video camera (22) includes first, second, and third CCD arrays (58, 60, 62) positioned to receive respective light rays (48, 64, 50) from the first light polarizer/analyzer combination, the gap, and the second light polarizer/analyzer combination and to generate first, second, and third video signals representative of the light each receives.

Abstract: In a photomask inspecting method, a photomask is inspected on the basis of the difference between the polarized state of elliptical light produced upon superposition of two linearly polarized light beams having orthogonal polarization directions and passing through two different optical paths and the polarized state of elliptical light produced when two linearly polarized light beams are superposed on each other after a target portion of a photomask is set in the optical path of one of the linearly polarized light beams. A photomask inspecting apparatus is also disclosed.

Abstract: A compensation polarizing plate which is superior in polarization characteristic to a polarizing filter layer of a composite layer sample is arranged on the polarization filter layer side of the composite layer sample whose polarizing filter layer has an insufficient degree of polarization, and polarization transmission axes of the polarizing filter layer and the compensation polarizing plate are kept in parallel with each other to compensate the polarization characteristics of the polarization filter layer. Measurement for obtaining the retardation value and the optical principal axis direction of the sample is carried out in the state of the compensated sample.