Showing papers on "Beam splitter published in 1985"

Liquid crystal display device and its preparation

Abstract: PURPOSE:To achieve even and uniform display by forming a grating-shaped uneven pattern by irradiating an orienting film between a pair of electrode substrate with interference fringes formed by two fluxes of laser light and arranging a columnar spacer to the region other than a picture element and a switching element CONSTITUTION:The laser light flux from a laser light source 15 is reflected by mirrors 16, 17, passes through a condenser lens 18 and a pinhole 19, collimated 20, reflected 21, and then incident in a beam splitter 22 Isolated light flux 22 is reflected by mirrors 23, 24, and the incident light into a photosensitive resin 13 coated on an electrode substrate 2(4) forms interference fringes by the two light fluxes forming a grating pattern on a polyimide resin 12 A spacer of an electrode substrate 2(4) is provided to the region other than the picture element region and switching element region not illustrated in the Figure By this constitution, satisfactory display contg no unevenness is achieved Further, color display is made possible if a picture element is combined with color filters

All-fibre polarising beamsplitter

Abstract: The first fibre equivalent of a polarising beamsplitter is reported. The device is based on a fused-taper fibre coupler. Separation of the orthogonally polarised components of the input light can be accomplished to better than 17 dB.

Optical head device with diffraction grating for separating a light beam incident on an optical recording medium from a light beam reflected therefrom

Abstract: An optical head device comprises a light source, condensing optics for condensing a light beam emitted from the light source on an optical recording medium, a photodetector for detecting the light of the light beam reflected from the recording medium, and a beam splitter having a diffraction grating arranged in the optical path of the light beam entering the recording medium from the light source along a plane substantially perpendicular to the optical axis of the incident light beam to cause the light reflected light from the recording medium to be diffracted by the diffraction grating and directed to the photodetector.

Interferometric optical path difference scanners and FT spectrophotometers incorporating them

Abstract: In an interferometric apparatus the path of the output beam of a rotary Optical Path Difference scanning assembly leading to an electrically responsive detector is maintained substantially fixed in space for any scan angle within predetermined limits, thus obviating a serious drawback of a prior art proposal wherein the output beam translates significantly over the detector face with changes in scan angle, with the result that the detector output is vitiated by totally spurious variations of the energy reaching it. In one embodiment, the scanning assembly comprises a beam splitter having a semi-reflective layer the output face of which cooperates with the face of an output mirror normal thereto, the axis of rotation being substantially coincident with the line of intersection between the prolongation planes of the two faces. A Fourier Transform spectrophotometer embodying the assembly is also described.

All-fibre polarisation splitter/combiner

Abstract: A single-mode optical fibre polarisation beam splitter/combiner has been fabricated from standard production fibre using a fused biconical taper technique. The operation of the device relies on form birefringence in the fused coupler.

Fiber optic magnetic field sensor

Abstract: The present invention provides an improved fiber optic magnetometer having particular application for use in environments having large magnetic field ranges and gradients, such as space based applications. The magnetometer includes a laser which generates a coherent beam of light which is split by a beam splitter into first and second beams. The first beam is passed through a single mode fiber optic having a short metallic conductor attached to it. This fiber is referred to as the "sensor arm" of the magnetometer. The second beam is passed through another single mode fiber which is wrapped around a modulator that is coupled to a feedback circuit. This adjusts the magnetometer such that ambient system noise is filtered and the device is maintained at maximum sensitivity. The output of the two fibers is combined forming a Mach-Zehnder interferometer. A current I is passed through the conductor in the sensor arm. If this fiber is in the vicinity of a magnetic field, displacement of the current carrying conductor will cause the fiber to bow. The resulting stretching of the fiber increases the pathlength for the light beam traversing through the sensor arm. The subsequent phase change measured by the Mach-Zehnder is related to the force exerted by the magnetic field on the conductor. The direction in which the fiber bows is dependent upon the magnetic field direction. The present invention also discloses an improved modulator for maintaining the present invention at the point of optimum operation.

Fibre-optic polarising beam splitter employing birefringent-fibre coupler

Abstract: An in-line fibre-optic polarising beam splitter, consisting of a fused birefringent-fibre coupler, is reported. Splitting of the orthogonally polarised lights was accomplished by increasing the difference of coupling ratios for the two polarisation modes. When a light at 1.402 ?m wavelength was coupled to the input lead, each polarisation was split on to different output leads, showing extinction ratios of more than 17 dB in both leads.

Unitary body optical coupler

Abstract: A fiber optic coupler easily molded as an optically transparent body and adapted to provide bidirectional transmission, multiplexing, demultiplexing, fail safe relaying, or other functions from a single coupler. The body (12) may be molded without side actions for simplicity and accuracy of placement of critical surfaces. The body includes first and second cavities (22, 24, 44, 46) for positioning light sources, such as a solid state emitter or fiber termination, and third and fourth cavities (32. 34, 48, 50) for positioning a light receiver, such as a solid state dector or fiber in a fiber connector. Opposite each source and receiver cavity is located a reflector cavity (36, 38, 40, 42) terminating in a reflecting face formed by the air-coupler body interface and operating by total internal reflection. A slot (14) extends into the body to position a filter such as a dichroic mirror or beam splitter between the cavities. The filter, source and receiver cavities, and reflecting faces are positioned to provide light paths from one or both sources, reflected by the associated reflective face, and passing through or reflecting off the filter. The transmitted or reflected light is then reflected off one or both of the remaining reflective faces to one or both of the receiver cavities. The reflective faces may be spherical, aspheric, concave, ellipsoidal, paraboloidal or flat.

Improved Version of a Polarized Beam Heterodyne Interferometer

Abstract: The heterodyne interferometer is a very sensitive instrument with a wide dynamic range, suitable for measuring surface displacements of amplitude down to mented present some disadvantages. T heir optical mounting is space demanding and alignments are critical. In addition, some inherent instabilities have also been identified. We have constructed a new version of the instrument which considerably reduces these disadvantages. The combination of a colinear beam Bragg cell and of a polarizing beam splitter makes the optical arrangement compact (less than lOcm long) and simplifies the alignment p rocedure. Ekper*pental results show that the sensitivity, lo+ A/ &z,reaches the t heoretical value and that the instabilities a re reduced by more than one order of magnitude, down to 0.3% of the output signal. 1. However, the interferometers p resently imple

Time reversal by an interferometer with coupled phase-conjugate reflectors.

Abstract: A new type of interferometer has been constructed that uses a beam splitter and two self-pumped BaTiO3 crystals as phase-conjugate reflectors in place of the usual interferometer mirrors. Counterpropagating beams of light are spontaneously generated between the two crystals, coupling the pair of phase conjugators. This optical oscillation locks the relative phase of the two phase-conjugate reflections such that they recombine at the beam splitter to form only a single beam as though they were truly time-reversed waves.

Astronomical polarimeter with 2-D detector arrays.

Abstract: It is shown how fast (50–100 kHz) piezoelastic modulation of the full Stokes vector can be used in combination with large CCD-type detector arrays with long integration times. The technique is to use an optical demodulation system (replacing the lockin amplifiers in corresponding single-channel detector systems). This allows the CCD detectors to be used with integration times and readout rates as in ordinary photometry. Including an optical phase switch in the system, the effect of the large pixel-to-pixel sensitivity variations can be removed from the recorded polarization images. The beam splitter that suppresses atmospheric noise can be located immediately before the detectors instead of being part of the polarization analyzer.

Talbot interferometry with increased shear.

Abstract: The modification of Talbot interferometer configuration for obtaining moire fringe shearing interferograms with an increased shear amount is proposed. The problem of decrease of interferogram quality that occurs when using higher frequency gratings is significantly eliminated by rotating the beam splitter grating about the axis perpendicular to the grating lines. The theory of the interferometer and its experimental verification are presented.

Simultaneous reflection and refraction of light without change of polarization by a single-layer-coated dielectric surface.

Abstract: The reflection and refraction of light of wavelength λ at an angle of incidence ϕ by the interface between two dielectric media of refractive indices N0 and N2 can be made completely independent of polarization by introducing a thin layer of refractive index N1 = (N0N2)1/2 and thickness d = (λ/4)(N12 − N02 sin2ϕ)−1/2. This is the basis of an ideal beam splitter, whose general characteristics are presented here. A particularly simple result is that the device reflectance has an upper limit of tan4(ϕ/2), so that a 50–50% beam splitter must operate at ϕ > 80.121°. Lower reflectances, attainable at lower angles, are suited for applications such as optical feedback and monitoring the output power and state of polarization of high-power lasers.

Polarising beamsplitter from fused-taper couplers

Abstract: We give the theoretical principles for polarising beam splitters constructed from fused-taper couplers, including the role of stress and form birefringence, the interaction length and the spectral response, all as a function of the physical parameters.

Tuned-port twin biconical-taper fiber splitters: fabrication from dissimilar low-mode-number fibers.

Abstract: Fused biconical-fiber splitters have been fabricated from dissimilar low-mode-number optical fibers. Through selective etching of the cladding diameters of the two fibers forming the splitter, the amount of energy transferred between the fibers can be controlled. A tuned condition characterized by low insertion loss and strong optical coupling between modes of the fibers forming the splitter has been demonstrated. In the detuned condition an asymmetry in the coupling between fibers has been observed.

Optical information recording and reproducing system

Abstract: PURPOSE: To attain the accurate tracking by providing a pre-wobbling pit on a header sector of a disk, detecting a tracking error signal via the pit so as to correct a push-pull tracking error signal thereby eliminating the offset due to the deflection of a diffracted light. CONSTITUTION: A light irradiated from a semiconductor laser 4 forms a light spot 11 onto a track 12 of the disk 10 via a coupling lens 5, a beam splitter (BS) 6, a galvano mirror 7, a λ/4 plate 8, and an objective lens 9. Its diffracted light goes reversely and is reflected in the BS 6 and detected by a couple of photodetectors 13. The signal is recorded and reproduced by using a pre- wobbling tracking error signal without an offset detected when the light spot 11 irradiates a meandering pre-wobbling pit 20 made of a long circular it arranged at the head of a header sector while the offset correction of a push-pull error signal including the offset detected by the irradiation of the light spot 11 of a pre-group 15 of a depth of 1/8 wavelength of a data recording sector is being executed. COPYRIGHT: (C)1987,JPO&Japio

Liquid crystal optical switching device having reduced crosstalk

Abstract: A liquid crystal optical switching device having reduced crosstalk includes a liquid crystal beam splitter for splitting incident light into polarized components thereof and a liquid crystal optical switch for directing those components to either a first or a second output port.

Variable-reflectance thin-film polarization-independent beam splitters for 0.6328- and 10.6-microm laser light.

Abstract: Truly polarization-independent beam splitters for 0.6328- and 10.6-microm (He-Ne and CO(2)) laser radiation are designed using single-layer-coated (Cleartran) ZnS and Ge prisms. These devices are found to be reasonably achromatic, their reflectance (beam-splitting ratio) can be varied over a wide range with little accompanying polarization error, and they are tolerent to small film-thickness and film refractive-index errors.

Imaging optical tracker

Abstract: Apparatus and a corresponding method for its use, for detecting and tracking targets in an optical field of view. The apparatus includes conventional telescopic optics to gather light from the field of view, beam splitters to divide the resultant beam into three sub-beams, three linear arrays of detectors, and three cylindrical lens systems to focus the three beams onto the detector arrays. Two of the arrays provide azimuth-angle and elevation-angle information concerning possible target positions, and the third is oriented at an angle to the first two, to provide information to resolve any ambiguities as to the target locations. The linear arrays can be scanned much more rapidly than a rectangular array, and higher resolutions can therefore be obtained without any sacrifice in processing speed.

Double passing the Kitt Peak 1-m Fourier transform spectrometer

Abstract: Attention is given to a simple technique for performing the conversion of the Kitt Peak 1-m Fourier transform spectrometer's dual input/output optical configuration to a double pass configuration that improves spectral resolution by a factor of 2. The modification is made by placing a flat mirror in the output beam from each cat's eye, retroreflecting the beams back through the cat's eyes to the first beam splitter. A single detector is placed at the second input port, which then becomes the instrument's output.

Discrete phase conjugate technique for precompensation of laser beams transmitted through turbulence

Abstract: A process and apparatus are disclosed for aligning a laser beam from a laser transmitter with an incoming laser beam, and driving any sensed tilt differences on an aperture and subaperture basis to zero. The apparatus uses a shared aperture component to sample the outgoing laser beam and the incoming target beam, a retroreflector array to reverse the direction of the subaperture samples of the outgoing beam, a common-mode wavefront sensor to measure subaperture tilt differences between the reversed samples of the laser and the incoming target beam, and a deformable mirror to drive any sensed tilt differences to zero. A transparent beamsplitter is used as the shared aperture component and an AC shearing interferometer is used as the basis for the common-mode sensing. By forcing the outgoing beam to be then conjugate of the incoming beam it is automatically precompensated for any aberrations in the transmission path.

Temperature stable boresight module

Abstract: Laser guided weapons delivery systems are now well known. Such systems, termed laser designator/sighting devices, are optical devices. One of the major potential sources of error in optical devices is misalignment of optical elements, particularly in helicopters and tanks where operating environments are quite severe. Alignment is maintained by boresighting, using optical instruments, called boresighting modules, which can be coupled optically with the misaligned optical device. Since these modules usually include prisms, beam dividers, mirrors and lenses, vibrations and other mechanical problems have been sources of error. While vibrational and weight load errors have been considered, the problem of errors due to thermal device has not been solved. The problem is solved herein by a boresight device incorporating a zero expansion, glass ceramic, optical transfer tube.

A device for use in assessing the position of a body

Abstract: The device is in the form of a block in which are mounted two parallel quadrant detectors Q1, Q2 at right angles to a third detector Q3. Parallel light 32 from a laser 30 is split by beam splitter S1 into beam 35 going to Q1 and beam 36 going via retroreflector 37 to beam splitter S2 producing beam 39 going to Q3 and beam 38 going to Q2. Movement of the block relative to beam 32 produces signals from Q1, Q2, Q3 from which position errors can be calculated. Splitter S3 may send beam 34 to a second similar device. Three such devices can be used to provide position errors caused by movement in two orthogonal directions and by roll, pitch and yaw, relative to a datum. Errors in a third orthogonal direction are obtained using a laser interferometer.

Calibration Of Surface Roughness Transducers At Angstrom Levels Using X-Ray Interferometry

Abstract: An x-ray interferometer for calibration of microdisplacement transducers at sub nm levels is under development. Using the lattice spacing of high perfection semiconductor industry grade silicon as a reference, the objective is to produce a portable, absolute length standard with a precision of 1 part in 108 traceable to primary standards. The interferometer is of the Hart design and fabricated from a monolith of single crystal silicon. The triple-blade construction utilises Lauecase diffraction in beam splitter, mirror and analyser and is capable of an ultimate resolution of about 10 pm. The system is now operational, and the first trials, reported in this paper, have been entirely successful.

Far-infrared dichroic bandpass filters.

Abstract: Filters which serve as dichroic beam dividers are useful for certain types of far-infrared photometer. We have used inductive cross metal mesh as reflective coatings on solid dielectric Fabry-Perot etalons to produce dichroic filters with quality factors in the range 3 < Q < 10. These filters reflect strongly at frequencies below the bandpass and retain their well-defined bandpass at angles of incidence as large as 45°. They have been used to make an efficient far-infrared dichroic photometer with six frequency bands between 10 and 100 cm−1.

Dual liquid crystal light valve based visible-to-infrared dynamic image converter system

Abstract: A visible-to-infrared image converter system (10) utilizes a source of infrared light (15), a polarizing beam splitter (19) for separating the infrared light into two polarized beams having their polarity at ninety degrees to one another, and first and second image converters (12, 13) positioned at right angles to one another, each to receive one of the two polarized beams. A source of identical visible information (21) furnishes information to each of the image converters (12, 13) which modulate the infrared beams and reflect them for recombination by the polarizing beam splitter (19).

FSK laser transmitting apparatus

Abstract: In an FSK laser transmitting apparatus, a light source can change the output light frequency. A driver performs FSK of the light source with a plurality of values. A beam splitter splits the output light from the light source into two split beams. A delay circuit delays one of the two split beams with respect to the other. A beam coupler combines delayed and nondelayed beams as the two split beams from the beam splitter. A controller detects the beat frequency of combined light from the beam coupler and supplies a control signal to the driver so as to set the beat frequency to be a predetermined value.

Apparatus for imaging sections of the human eye

Abstract: A device for displaying areal, layered areas of the human eye, which works with optical scanning of the examination object in a line and column grid corresponding to a standard television standard, the scanning being carried out with laser light which is based on cross-sections of the focal spot of less than 0.5 µm diameter is focusable, a microscope lens is provided for focusing this laser light bundle, that the scanning light focuses with a small depth of field corresponding to the layer thickness of the examination area, the detection beam path being formed by part of the scanning beam path , from which a part of the light reflected in the direction of the light source can be coupled out for the intensity measurement by means of a beam splitter arrangement. In a confocal arrangement with the focal plane of the microscope objective, a pinhole is provided between the beam splitter device and the detector arrangement, through which only light that comes from the depth of field of the microscope objective can pass. An active mirror with electronically controllable refractive power is arranged in the illumination beam path, by means of which the distance of the examination field from the main plane of the microscope objective can be changed.

Erasable optical recording and reproducing device

Abstract: PURPOSE:To average the intensity distribution inside a light spot for erasion and to eliminate a local intensity fluctuation, by providing a diffracting means which diffracts the output light of a laser array which is a light source for erasion in the direction, in which the light spot scans a recording medium. CONSTITUTION:An optical beam (l) outputted from a semiconductor laser 101 for recording and reproducing which produces light having a wavelength lambda1 is transformed into an almost parallel optical beam by a condenser lens 102 and passed through an optical beam synthesizer 105 and beam splitter 106. After passing through the beam splitter 106, the optical beam is reflected by a reflecting mirror 107 and forms an almost circular light spot L on the guide track 51 of an optical recording disk after passing through a diaphragm lens 108. Another optical beam (m) outputted from a laser array 103 for erasion which produces light having a wavelength lambda2 is transformed into an almost parallel optical beam having an oval cross section by a condenser lens 104 and reflected by the synthesizer 105 after passing through a diffraction element 118. After reflection, the optical beam forms an oval light spot M, the direction of whose major axis coincides with the longitudinal direction of a groove 51, on the groove 51. The element 118 gives a diffracting effect to the beam (m) in the direction of groove 51 and the intensity fluctuation inside the light spot M for erasion can be eliminated.