Showing papers on "Waveplate published in 1989"

High throughput contrast enhancement for polarized displays

Abstract: A display having a linearly polarized image source, a quarter-wave retarder for transforming the linearly polarized illumination to circularly polarized illumination, imaging elements responsive to the circularly polarized illumination for producing viewable circularly polarized imaging illumination, and a circular imaging illumination to viewable linearly polarized imaging illumination. The circular polarizer includes a quarter-wave retarder for transforming the circular light to linearly polarized light, and a linear polarizer configured to transmit the linearly polarized imaging illumination. Contrast enhancement is achieved by the circular polarizer which functions to block ambient light reflected from the front element of the imaging elements as a result of transmission through the circular polarizer.

Apparatus and process for performing ellipsometric measurements of surfaces

Abstract: A compact ellipsometric apparatus is constructed using as a building block a tri-beam ellipsometric sensor having a monochromatic source of polarized light with a diverging beam of sufficient divergence that three analyzers and associated light detectors may be placed into the beam side by side so that they each receive light reflected from a surface under study at the same angle of reflection. Pairs of these sensors are used together, with one of each pair having in the optical path a quarter wave plate matched to the monochromatic light wavelength and the other of the pair having no quarter wave plate, but with the light wavelength and angle of incidence being the same for each pair. A variety of measurements are made by constructing apparatus using one or more pairs of these basic sensors, the pairs of sensors varying from each other in the light wavelength of the source and the angle of incidence of the polarized beam of light to the surface. Various apparatus having from one to six pairs of sensors have been designed, with higher numbers of sensors providing greater generality in respect to the properties that can be measured.

Infrared achromatic retarder

Abstract: An infrared achromatic waveplate structure having a cadmium sulfide (CdS) plate and a cadmium selenide (CdSe) plate aligned with each other so that the fast axis of the plates are perpendicular to each other, this structure provides a desired retardance of a first orthogonal polarization component with respect to a second orthogonal polarization component of an incident light beam. The thickness of the plates are in a ratio between 0.8:1 and 0.9:1 (CdSe:CdS), an achromatic response with a substantially constant retardance is provided in a wavelength range from 3 to 11 microns. A desired amount of retardance is available by adjusting the thickness of the two plates as long as the ratio of the thicknesses is maintained within the recited value. In particular a quarter wave net retardance of an incident light beam operating between 3 and 11 microns is provided when the cadmium sulfide plate is 1.25 millimeters and the cadmium selenide plate is 1.0666 millimeters.

Birefringent optical fiber device for measuring of ambient pressure in a stabilized temperature environment

Abstract: OF THE DISCLOSURE: The present disclosure describes a birefringent optical fiber device for measuring of ambient pressure in a stabilized temperature environment, when connected respectively to a light source and a measuring apparatus. The device comprises a first device for receiving polarized light from the light source; a birefringent optical fiber having a solid content, the birefringent fiber being connected to the first device for receiving the polarized light which has light signal components polarized along two orthogonal polarisation axes of the birefringent fiber, the birefringent optical fiber having a preselected length determined by a range of pressures to be measured; and a second device for receiving light signals emitted from the birefringent fiber, the light signals having elliptical polarization state characterized by major and minor axes, whereby cross-talk between the light signal components along the polarization axes being responsive to the ambient pressure in the environment.

Wavelength drop-and-insert device

Abstract: The invention relates to an optical wavelength drop-and-insert device including two sets of input/output optical fibers attached to two terminals on each of a first and second polarization beam splitter. The first polarization beam splitter splits incoming light into two linearly orthogonal polarizations which are transmitted via a first and second polarization preserving fiber through a first and second quarter wave plate for changing the subject beams into circular polarization. An optical filter is included to transmit or reflect light from the quarter wave plates according to a wavelength based transmission/reflection characteristic. The second polarization beam splitter then acts as a combiner for the circularly polarized light which is received via a third and fourth polarization preserving fibers and then is transmitted via an output optical fiber. The second polarization beam splitter splits incoming light into two orthgonal polarizations via an incoming optical fiber for two way operation. A second embodiment of the invention uses a first and second optical filter which can be a Fabry Perot or Bragg diffraction grating type optical fiber.

Method and apparatus for sensing disturbance using fiber-optic polarization rotation

Abstract: A method and apparatus for sensing vibrational disturbance using fiber optic coils conducting circularly polarized light. A circularly polarized light source illuminates each of a sensing fiber optic coil in a disturbance-sensitive environment and a reference fiber optic coil in a constant environment, and light from both coils is analyzed through polarization shuttering to detect the degree of polarization rotation thereby to enable determination of frequency and amplitude of the disturbance.

Instrument for measuring solar magnetic fields

Abstract: In a solar vector magnetograph for measuring solar magnetic fields including a telescope pointable to a solar zone and relay optics mounted there-behind, including a collimating lens, a quarter wave plate, a light polarizer, a beam expanding means, a narrow bandpass blocking filter to admit a narrow spectral band of polarized light, a reimaging lens to focus the resulting beam and an image receiver, the improvement provided is a solid Fabry-Perot etalon filter which is mounted between the blocking filter and the reimaging lens, such filter being of a desired refractive index and thickness so as to select a narrow band of the so-transmitted polarized light and to transmit same to the image receiver, all in order to isolate and record the emissions of atomic species and to infer the magnetic field at the solar zone In another and preferred embodiment, the etalon filter is electrically tuneable to change its passband to select another narrow band of the transmitted polarized light and transmit it to the image receiver to record another image of the solar zone at the selected passband and compare with the image obtained at the previous passband to derive in greater detail a map of the intensity and the direction of the magnetic field in the solar zone, including the photosphere or the atmosphere thereabove so as to forecast solar flares and other disturbances based on solar magnetic field changes

Polarized wave separating optical circuit

Abstract: PURPOSE:To realize subminiaturization and stable operation by integrating a polarized wave separating circuit which uses a balanced receiver type polarization diversity reception system by using optical waveguides. CONSTITUTION:This optical circuit is equipped with an optical coupler optical waveguide, 1st and 2nd branch optical waveguides, a polarized wave separating filter 210 inserted into a groove 209, and photodetectors 211a, 211b, 212a, and 212b. Here, the phenomenon that an optical waveguide made of quartz glass holds a linear polarized wave is utilized. Further, two polarization beam splitters are formed of thin film filters in the groove formed at 45 deg. to the optical waveguides and signal light beams of a (p) wave and an (s) wave are detected by balance type photodetectors mounted on waveguide end surfaces. Consequently, the circuit is subminiaturized and the stable operation becomes possible.

Polarlizing and illuminating device and projection type display device provided therewith

Abstract: PURPOSE: To improve utilization efficiently of light by emitting either the P polarized light component or the S polarized light component of an incident luminous flux separated by a polarizing beam splitter and the other component whose plane of polarization is rotated by 90° with the aid of a λ/4 optical phase plate and a reflecting member. CONSTITUTION: The P polarized light component L p of the collimated luminous flux emitted from a condenser lens 24 is transmitted through the action surface 26a of the polarizing beam splitter 26 and the S polarized light component L s thereof is reflected at right angle on the surface 26a, so that the P polarized light component is separated from the S polarized light component. The S polarized light component L s is made incident on the λ/4 optical phase plate 27, reflected on the reflection surface of the reflector 28 and transmitted through the λ/4 optical phase plate 27 again, so that the plane of polarization thereof is rotated by 90° and converted to the P polarized light component L p . Then, the P polarized light component L p is transmitted through the action surface 26a as it is and emitted from the beam splitter 26. On the other hand, the transmitted P polarized light component L p is reflected at right angle on the total reflection surface 29a of a total reflection prism 29 and emitted from the prism 29 in parallel with the converted P polarized light component L p . Thus, the utilization efficiency of light is improved. COPYRIGHT: (C)1991,JPO&Japio

Optical design of a dual-polarization receiver for 220–280 GHz

Abstract: A 220–280 GHz dual polarization receiver has been built for the James Clerk Maxwell Telescope. Schottky diode mixers cooled to ∼15K by a closed-cycle refrigerator are used to give DSB noise temperatures of 300K and 420K in the two channels. The optical design is based on gaussian-beam optics, and is frequency independent; it allows the significant higher order gaussian modes to propagate unhindered, thus offering the prospect of very high aperture efficiency. The receiver includes a number of novel optical components, including a completely symmetric dual polarization Martin-Puplett interferometer, used as the L.O. injection diplexer; a dielectric waveplate used as an in-line variable polarization splitter; and a dual-polarization in-line tunable Fabry-Perot SSB filter. Measurements of the performance of the optical system are presented.

Stereoscopic video display device and polarization glasses used for the same

Abstract: PURPOSE: To obtain a satisfactory stereoscopic picture without changing polarization even when the phase difference of birefringence is present there on by providing an optical element between a video light source and a video synthesizing surface to lead out the two pairs of video light to be linearly polarized in polarizing directions which are mutually different at 90°. CONSTITUTION: A vertically linearly polarized light filter 25 is fitted to a video light source 4 and a horizontally linearly polarized light filter 26 is fitted to a video light source 5. The two pairs of video light 27 and 28 are reflected on a mirror 15 and synthesized on a translucent screen 14. For linear polarization glasses 29, a horizontally linearly polarized light filter 30 and a vertically polarized light filter 31 are respectively fitted for left and right eyes and the synthesized video light 27 and 28 can be observed while being splitted. Thus, even when the phase difference of the birefringence in the optical element including the video synthesizing surface such as the mirror and the transmissive screen, etc. is present there on, the video light to be emitted is still linearly polarized as it is and accordingly, the satisfactory stereoscopic picture can be observed. COPYRIGHT: (C)1991,JPO&Japio

Electro-optic modulator and modulation method

Abstract: A device and method for modulating light intensity in response to a varying electrical signal which is particularly useful with optical fiber information sensing systems. The device includes a number of components positioned in seriatim in an elongated cavity in an insulating body. Means for receiving a light signal, such as from an optical fiber, is positioned at one end of the cavity. A lens receives the light and collimates it into a narrow collimated beam directed through the cavity. The beam is polarized, retarded by a wave plate to circular polarization and passed through a modulator material which is capable of rotating beam polarization in response to varying voltage signals imposed on the modulator through electrodes thereon. A mirror at the end of the modulator reflects the beam back through the system. The beam is further rotated by electro optic material as a function of applied voltage, then further retarded by said wave plate and then attenuated by said polarizer as a function of the applied voltage. The returning attenuated beam is then focused into the optical fiber.

Polarized wave modulating device

Abstract: PURPOSE:To perform polarized wave modulation without attenuating signal light by making the polarized wave directions of 1st and 2nd exciting light beams coincident with the main axis of an optical fiber for polarized wave maintaining type amplification and specifying the angle between the polarized wave direction of the signal light and the polarized wave directions of the 1st and 2nd exciting light beams. CONSTITUTION:The exciting light E1 which is the projection light from a 1st light source 1 and the exciting light E2 which is the projection light from a 2nd light source are multiplexed by a 1st multiplexer 4 so that their polarized light directions cross each other orthogonally. The multiplexed exciting light beams E1 and E2 are multiplexed by a 2nd multiplexer 5 with signal light S which is a continuous wave. The signal light S and the exciting light beams E1 and E2 which are multiplexed by the multiplexer 5 are made incident on the optical fiber for amplification. At this time, the polarization direction of the signal light S is adjusted by a polarized wave adjuster 7 so that the exciting light beams E1 and E2 are at 45 deg.. Then the Raman amplification of the signal light S is with the exciting light beams E1 and E2. The gain at the time of the Raman amplification becomes maximum when the polarization directions of the exciting light and signal light coincide with each other and minimum when the polarization directions cross each other orthogonally.

Image formation type displacement gauge

Abstract: PURPOSE:To improve the displacement detecting accuracy of the title displacement gage by irradiating a guide beam of a visible wavelength in addition to a detecting beams of an invisible wavelength and, at the same time, separating a guide beam from reflected rays of light made incident on a photodetector for detecting displace ment. CONSTITUTION:In the first place, a changeover switch 19 is switched to a light source 10 side and the light source 10 is driven 11. Then a guide beam of a visible wavelength emitted from the light source 10 irradiates an object 20 to be measured through a collimator lens 2B, half mirror 17, and object lens 5. While the object 20 is irradiated by the guide beam, the position of the guide beam is adjusted so that the position of the image of the guide beam can become the position to be measured for displace ment. Then the switch 19 is switched to another light source 1 side and a detection beam of an invisible wavelength emitted from the light source 1 forms an image on the object 20 through a collimator lens 2A, polarization beam splitter 3, 1/4 wave plate 4, the mirror 17, and the lens 5. The detection beam reflected by the object 20 advances the same path in the opposite direction and is made incident on a photode tector 8 through the beam splitter 3, a condenser lens 3, and cylindrical lens 7. The photodetector 8 measures a displaced quantity.

Assembling method of voltage sensor

Abstract: PURPOSE: To improve a temperature characteristic and to prevent false detection in outdoor use by a method wherein the mechanical profile irregularity of an optical crystal having a Pockels effect is set to be 0.2 degrees or below in terms of an incident angle of light or a change in the quantity of output light is reduced to be within ±0.4 dB by adjustment of the direction of incidence. CONSTITUTION: The respective cut faces of each optical crystal, a polarizer 1, a 1/4 wave plate 2, an LiNbO 3 crystal 3 and an analyzer 4 are polished to improve the angle of axial deviation of an incident light to the crystal axis of the crystal 3 so that the final accuracy may be 0.2 degrees or below, and they are brought into contact with each other under pressure in a direction (a) and then bonded. In another way, fiber lenses 5A and 5B on the incidence and emission sides are rotated around optical axes respectively so that a change in the quantity of output light be within ±0.4 dB or less on the occasion when they are bonded. By this method, a change in the temperature characteristic of detection sensitivity is reduced to be ±2% or less in a temperature range of -20 to 80°C, the nonuniformity in the sensitivity of detection of voltage due to temperature is lessened and thus false judgement can be prevented. COPYRIGHT: (C)1991,JPO&Japio

Detection system for circularly polarized radiation

Abstract: A system for detecting and analyzing polarized radiation having a circular polarization component while utilizing radiation filter structures having combined wavelength and polarization sensitive characteristics. The system includes a radiation filter which comprises a plurality of different wavelength λ1 to λn interference filter coatings applied to a filter substrate as a plurality of parallel adjacent stripes, such that different wavelengths λ1 to λn are passed by the different stripes. Moreover, a plurality of different polarization filters of either parallel polarization or perpendicular polarization, are also applied as a plurality of parallel adjacent stripes to the different areas of the filter substrate. The arrangement includes first, second, third and fourth interference filter stripes for each wavelength λ1 to λn, two parallel polarization filters for each wavelength λ1 to λn, and two perpendicular polarization filters for each wavelength λ1 to λn. A complete detection and analysis of the polarization characteristics of the circularly polarized radiation is achieved by applying a quarter wave plate to each polarization component (both parallel and perpendicular) of each wavelength λn to provide two measurements, one with and one without the quarter wave plate for each measurement (both parallel and perpendicular) at each wavelength λn.

Multiplexing/demultiplexing unit and multiplexer/ demultiplexer for coherent light communication

Abstract: PURPOSE:To synthesize or separate signal light rays multiplexed at narrow inter-wavelength intervals at a low loss by using a Fabry-Perot interferometer CONSTITUTION:The wavelength multiplexed light of wavelengths lambda1-lambdan passes a splitter 11 and is polarized to circularly polarized light by a quarter wave plate 12 when this light is entered as a P wave to a polarized beam splitter 11 Of these wavelengths lambda1-lambdan, the light of, for example, the wavelength lambda1, passes the Fabry-Perot interferometer 13 The light of the other wavelengths is reflected by the interferometer 13 The light except the wavelength lambda1 is reflected by the interferometer 13 and is made by the wave plate 12 into an S wave which is reflected by the splitter 11, is separated from the incident direction and is emitted as the S wave The light of lambda2-lambdan incident in the reflection optical axis direction of the splitter 11 as the S wave is reflected by the splitter 11 and is polarized by the wave plate 12 to the circularly polarized light This light is reflected by the interferometer 13, is converted to the P wave by the wave plate 12 and is emitted through the splitter 11 The light of the wavelength lambda1 is synthesized with the light of lambda2-lambdan and is emitted

Nondestructive Mapping of Surface Film Parameters with Dynamic Imaging Microellipsometry

Abstract: Dynamic Imaging Microellipsometry (DIM) is a rapid, high resolution, full-field imaging ellipsometric technique previously described [1, 2]. Development and characterization has advanced through the construction and testing of the semi-automated, second DIM system. Several improvements in the system’s design have been implemented, but the basic approach of combining an optical system derived from conventional ellipsometry with video and image processing has been retained. The first DIM system used a Polarizer, Compensator, Specimen, and Analyzer (PCSA) optical system. The current instrument has undergone modification into a Polarizer, Half waveplate, Specimen, Compensator, and Analyzer (PHSCA) configuration. The polarization rotation is now under direct computer control enabling automated operation that greatly facilitates statistical analysis of the instrument’s response. Finally, high quality metallic and silicon samples have been studied, refining the previous estimates of the systems accuracy, noise and spatial resolution.

Polarization converting element

Abstract: PURPOSE: To efficiently convert unfixed polarized light to specific linearly polarized light with simple constitution by supplying the P polarized light or S polarized light emitted from a polarization beam splitter to which the unfixed polarized light is made incident to an optical member which converts the polarized light to the S polarized light or P polarized light. CONSTITUTION: The polarization converting element PCE is constituted of the 1st polarization beam splitter PBS 1 to which the unfixed polarized light is made incident, the 2nd polarization beam splitter PBS 2 to which the P polarized light emitted from the 1st polarization beam splitter PBS 1 is made incident and the constituting part to be used as the optical member to convert the P polarized light emitted from the 2nd polarization beam splitter PBS 2 to the S polarized light and to make this light incident to the 2nd polarization beam splitter PBS 2, i.e. the constituting part consisting of an electrode Et, an optical modulating layer member PML, a reflecting mirror M (for example, a dielectric mirror), and an electrode Er. The smaller number of the optical parts used for the constitution are necessitated in this way and the conversion of the unfixed polarized light to the specific linearly polarized light with the high eff1iciency is possible. COPYRIGHT: (C)1991,JPO&Japio

Microwave remote automatic recognizing device

Abstract: PURPOSE:To attain transmission/reception with high sensitivity even when the direction of a response device with respect to a transmission and reception antenna is comparatively rough by providing a circularly polarized plane to the transmission and reception antennas. CONSTITUTION:The transmission and reception antennas 4b, 5b have a circularly polarized face. A microwave radiated from the antenna 4b is propagated while its electric field plane is being rotated, but when a response device exists in the microwave arrival range, since a moment when the polarized wave plate of the incoming microwave and the polarized plane of the antenna of the response device are coincident exists even when the direction is not so strict, a reply wave based on a code data registered in a built-in memory of the response device is returned toward a microwave remote automatic recognition device at the moment. Moreover, even when the replied wave is a linearly polarized wave, since the reception antenna receives the wave as a circularly polarized wave, the transmission/reception with high sensitivity comparatively independently of the direction of the response device is attained.

Polarized beam splitting effect in inhomogeneously magnetized magnetooptic films.

Abstract: Linearly polarized light passing through a several micron thick magnetooptic film in the inhomogeneous magnetization state is split into a linearly polarized central beam and linearly polarized first and higher order diverging rings. The polarization of the central output beam lies in the same direction as the linearly polarized input, while the polarization of the diverging rings lies in a direction orthogonal to the input plane of polarization. The effect is described, and applications of the effect are discussed.

Reduction projection type position detection and device therefor

Abstract: PURPOSE:To detect an alignment mark on a sample in response to the change of the thickness of a resist, and to enable alignment with high accuracy by using three beams of light which have specified wavelength differences from an Ar leaser oscillator at least and light having a specified wavelength from a He-Ne laser oscillator. CONSTITUTION:An S polarized light laser from an Ar laser 51 simultaneously oscillating wavelengths 458nm, 488nm and 515nm and an S polarized light laser from an He-Ne laser 52 oscillating a wavelength of 543nm are synthesized by a dichroic mirror 53, and introduced to a polarization beam splitter 54. The splitter 54 rectangularly reflects the S polarized light laser, and transmits P polarized light. The light is reflected by the splitter 54, and 54 lights an alignment mark 58 on a wafer 57 by a reduction projection lens 56 through a quarter wave plate 55. Reflected light from the alignment mark 58 passes through the lens 56, and is changed into P polarized light by the quarter wave plate 55 again, is transmitted through the splitter 54 and rectilinearly propagates, and is divided into an x-direction mark detecting system 63 and a y-direction mark detecting system 64 by a half mirror 62. Light is converted into video signals by detectors 67, and the position of the image is sensed through specified arithmetic processing.

Differential autocollimation sensor

Abstract: PURPOSE:To measure differentially an angle formed by surface normals at two reflecting points, by projecting a light twice onto a surface to be measured every time when a detector and the surface to be measured are moved relatively, and by detecting the deflection of a reflected light from the optical axis of an incident light. CONSTITUTION:A sensor 1 comprises a light source element 2, first and second polarizing beam splitters 3 and 5, 1/4lambda wave plates 4 and 6 provided for the beam splitters respectively, and a light-sensing element 8. The light source element 2 is constituted of a light-emitting element 2a such as a laser diode, a collimator lens 2b, etc. and emits a parallel beam 2c of a necessary light flux. The parallel beam 2c is made incident in the theoretical direction of a normal of a surface 10 to be measured, through the first polarizing beam splitter 3 and the 1/4lambda wave plate 4. A reflected light is bent toward the polarizing beam splitter 5 by the beam splitter 3 and falls on the surface 10 again at another position through the 1/4 wave plate 6. A reflected light therefrom is sensed by the light-sensing element 8, a deflection angle is detected by a photoelectric element 8a, and an angle formed by surface normals at two reflecting points is measured differentially.

Method and apparatus for detecting end part of transparent film

Abstract: PURPOSE: To detect precisely the end part of a transparent film by making use of the optical activity of the transparent film rotating a plane of polarization of a linearly polarized light when the polarization is transmitted through the film. CONSTITUTION: When a light emitted from a light source 1 enters a polarizer 2, it turns to be a linearly polarized light having a plane of oscillation in one direction. When part of this linearly polarized light is transmitted through a transparent film 3, it turns to be a linearly polarized light having the direction of polarization rotated and enters an analyzer 4. Since the plane of polarization of the analyzer 4 is so disposed as to orthogonally intersect that of the polarizer 2, the linearly polarized light coming directly from the polarizer 2 without passing through the film 3 is intercepted by the analyzer 4. At this time, the linearly polarized light having a component of the same direction with that of the plane of polarization of the analyzer 4, out of the linearly polarized light rotated in the film 3, is transmitted through the analyzer 4. By detecting this transmitted light, the end part of the film 3 and the shape thereof can be detected. COPYRIGHT: (C)1991,JPO&Japio

Optical adder for optical attenuation

Abstract: There is provided an optical adder for accurately and additively specifying variable optical attenuation, which comprises a quarter wave plate disposed on an optical axis for changing an incident linearly polarized light beam emanating from a light source to a circularly polarized light beam; and one or more neutral density filter plates all disposed on the optical axis next to said quarter wave plate for attenuating the incident circularly polarized light beam respectively additively by a predetermined amount.

Novel Waveplate Designs For The IR Spectrum

Abstract: Infrared optical systems, including ellipsometers and sensors, make frequent use of traditional waveplate technology. In some cases, the limited spectral bandwidth associated with conventional IR waveplates has limited the wavelength range over which these systems can perform. The mathematical procedures for designing broadband waveplates have long been available, but suitable materials for IR applications have been limited. Recent efforts in IR crystal growth have provided a wider range of birefringent materials which can be used for novel waveplate designs. This paper examines basic waveplate theory, including the relatively unknown effects of etaloning in the presence of finite surface reflectance, and proceeds to a discussion of both conventional and novel waveplate designs. These include tunable and achromatic waveplates covering all or part of the NIR-IR wavelength spectrum. Materials such as AgGaS 2 , MgF 2 , CdS and mixed CdS x Se 1-x crystals will be discussed. Several designs specific to multiple wavelength lasers and frequency agile lasers will be covered.