Showing papers on "Beam splitter published in 1993"

Efficient radially polarized laser beam generation with a double interferometer.

Abstract: Conversion of a linearly polarized CO2 laser beam into a radially polarized beam is demonstrated with a novel double-interferometer system. The first Mach–Zehnder interferometer converts the linearly polarized input beam into two beams with sin2 θ and cos2 θ intensity profiles, where θ is the azimuthal angle. This is accomplished by using two spiral-phase-delay plates with opposite handedness in the two legs of the interferometer to impart a one-wave phase delay azimuthally across the face of the beams. After these beams are interfered with, the resulting beams are sent directly into the second Mach–Zehnder interferometer, where the polarization direction of one beam is rotated by 90°. The beams are then recombined at the output of the second interferometer with a polarization-sensitive beam splitter to generate a radially polarized beam. The output beam is ≈ 92% radially polarized and contains ≈ 85% of the input power. This system will be used in upcoming laser particle acceleration experiments.

Head-mounted projection display system featuring beam splitter and method of making same

Abstract: A head-mounted projection display system featuring a beam splitter displays a simulated environment to an observer using a light-weight, low-cost, head-mounted projector and a retro-reflective screen. The display system optically co-locates the projector with the observer's eyes for effective use of either curved or flat retro-reflective screens. High screen gain achieved by the head-mounted projection display system makes inexpensive projector sources such as a cathode ray tube feasible. An alternative head-mounted display system also incorporating beam splitters produces an unlimited horizontal field of view, but with limited binocular overlap, while using multiple head-mounted image sources for each eye. A method of providing the head-mounted display system also is disclosed.

Barcode scanner using an array of light emitting elements which are selectively activated

Abstract: A bar code scanner employs an electronic means for causing the light beam to scan a bar code symbol, rather than using a mechanical device to generate the scan. A linear array of light sources, activated one at a time in a regular sequence, may be imaged upon the bar code symbol to simulate a scanned beam. Instead of a single linear array of light sources, a multiple-line array may be employed, producing multiple scan lines. The multiple scan lines may be activated in sequence, or activated simultaneously (time-division or frequency-division multiplexed. The multiple scan lines can provide signal enhancement, noise reduction or fault correction if directed to the same bar code pattern. Multiple scan lines may be generated using a single light source and a beam splitter, with mechanical scanning, as well as by the sequentially-activated light sources. Multiple simultaneous scan lines may be employed to generate a raster scan at lower mechanical scan frequency. In another embodiment, a tunable laser may be employed to provide a scan without moving parts; a laser beam from the tunable laser is reflected from a diffraction grating that produces an angular deviation dependent upon the wavelength of the laser output. As the frequency of the tunable laser is varied in some selected pattern, the laser beam will scan accordingly.

Intimate source and detector and apparatus employing same

Abstract: There is provided a system of detecting mark-sense indicia wherein the images of a light source (26) and the region of sensitivity (122) of a light sensor are substantially coaxial, coplanar, and coextensive throughout the working depth of field (21). This system is insensitive to the laminate and the diffusion effects. A light source (26) is aimed at a beam splitter (15) that diverts a portion of the light beam (36) through optics (14) that focus the light on a reflective target (12) containing a bar code symbol (17) to be scanned. The reflected beam (38) is returned through the optics (14) and the beam splitter (15), and a portion of the reflected beam is conducted to a light sensor (24). In this manner, the light path from the source (26) to the optical sensor (24) is split twice by the beam splitter (15). The optics (14) are configured so that the light beams that define the field of illumination and the region of sensitivity and which pass between the optics (14) and the target (12) are congruent, having identical optical axes and angles of divergence (16, 18). The region of sensitivy is congruent with the field of illumination in any plane throughout the depth of field of the optics. Field stops (20, 22) may be optionally provided for the light source (26) and the light sensor (24) in order to better define the dimensions of the field of view and field of illumination.

Fiber optic monitor module

Abstract: A fiber optic connector module includes a beam splitter for directing 10 percent of a fiber optic signal to a monitor connector The input of the beam splitter is passed through a variable attenuator By monitoring at the monitor connector, the variable attenuator can be adjusted utilizing the known split ratio of the beam splitter to achieve a desired dynamic range of the optical signal leaving the module

Method and apparatus for non-invasive measurement of blood sugar level

Abstract: To intensity-modulate laser light periodically wavelength-modulated by and emitted from a wavelength-variable semiconductor laser 11. To separate the laser light into optical paths 13a, 13b with a beam splitter 14 to irradiate an examined location 17 for assessing blood sugar through path 13a. To detect the intensity of transmitted or reflected light from examined location 17 with a first detector 21 and the intensity of laser light passing through path 13b with a second detector 22 to detect the ratio of the former intensity to the latter intensity with a logarithmic ratio amplifier 25. To detect the rate of change in the ratio with respect to the change in wavelength of the wavelength modulation with a lock-in amplifier 26 to obtain a derivative spectral signal of the absorption spectrum of glucose. An arithmetic processor 27 detects blood sugar in the examined location from the derivative spectrum.

Quantum statistics of a lossless beam splitter: SU(2) symmetry in phase space.

Abstract: A lossless beam splitter (a dielectric interface, a passive interferometer, or a linear coupler) changes the quantum state of two incident modes by an SU(2) transformation. Apart from phase shifting, the argument of the quadrature wave function of the system undergoes a rotation. Quasiprobabilities are changed by the inverse mode transformation. The use of balanced beam splitting allows the simultaneous measurement of conjugate quadrature components via homodyning the emerging beams with two strong coherent reference fields that differ in their phases by \ensuremath{\pi}/2. The measured probability distribution is given by a generalized Q function. It depends on the state of the field entering the second beam-splitter port. For a vacuum, the Q function will be obtained. The use of unbalanced beam splitting allows the measurement of a squeezed Q function without using squeezed states. Dissipation in Gaussian reservoirs corresponds exactly to a heuristic beam-splitter model. As a mathematical tool, the Fokker-Planck equation of damping in phase-sensitive reservoirs and the corresponding quantum master equation were solved. The dissipative decay of a Schr\"odinger-cat state was studied as an example. The sensitivity of quantum coherence with respect to damping can be interpreted geometrically.

Improved particle sensor and method for assaying a particle

Abstract: A particle sensor (10) has a mirror cavity (79) unobstructed by masks and the like. A light detector (75) is at the mirror secondary focal point (16) and well outside the mirror cavity (79). A variation includes a beam splitter (105) and a secondary light detector (77) to improve detection of larger particles (29). A second embodiment includes a pair of elliptical mirrors (11a, 11b) offset along the light beam (31). Light reflected by the second mirror (11b) represents only changes in laser power and light scattered by gas molecules (161). The resulting signal is subtracted from that produced by the first mirror (11a) to obtain a relatively 'clean' signal useful to assay very small particles (29). Another variation involves an imaging system (209) for collecting light scattered by gas molecules (161).

Interferometers and minimum-uncertainty states

Abstract: Minimum-uncertainty states in variables which are quadratic in mode creation and annihilation operators can be used to increase the accuracy of interferometric measurements. For a general interferometer we show how to find the relevant uncertainty relation. We consider two specific examples, a Mach-Zehnder interferometer and a Mach-Zehnder interferometer in which the first beam splitter has been replaced by a four-wave mixer. For both devices su(2) squeezed minimum-uncertainty states can be used to achieve phase-measurement accuracies of 1/N, where N is the total photon number at the input. We also describe a method of producing approximate versions of these states.

Optical module for an optically based measurement system

Abstract: An optical module for an optically based measurement system, such as an electro-optic system (10) for measuring electrical characteristics of a device under test (14), has a probe arm (26), a layer of electro-optic material (27), and a first optical system for delivering a measurement beam (44) to the layer and for producing therefrom an information-carrying beam having optical characteristics indicative of the electric characteristics. The first optical system includes a first lens (128), and (optional) polarization bias adjustment (130), a dichroic beamsplitter (112), and a second lens (114). The module also has a second optical system for delivering an observation beam (66) through the layer and onto a portion (68) of the device and for forming from rays (69) stemming from the observation beam a light pattern (70) indicative of the portion. The information-carrying beam is analyzed in a polarization analysis module into component beams (136, 138) in respective linearly independent polarization states. Converters (144, 146) produce electrical signals (147, 148) indicative of the intensity of the respective component beams; alternatively, the component beams are conveyed for analysis elsewhere. Connections (46, 65, 74, 149, 150) to and from the components fixedly mounted relative to the probe arm are flexible, allowing the probe arm and the components to move freely in any direction relative to the device under test.

Speckle-free image in a laser-diode microscope by using the optical feedback effect.

Abstract: Besides its desirable power level, the use of a laser as a light source in microscopes opens the possibility of observing high signal-to-noise ratio images of dynamic phenomena that are sensitive to certain polarizations, excitation wavelengths, and phase shifts. However, the image quality is degraded by speckle noise. We propose a new fiber-illuminated laser-diode microscope that generates speckle-free images. The feedback effect in the laser diode is employed to transform a single-mode free-running laser into a multimode laser and to generate an output light whose multimode spectrum changes with time. The output of the laser diode is then passed through a multimode fiber whose exit face illuminates a conventional microscope with a continuously changing speckle pattern. These uncorrelated speckle patterns are averaged by a video detector to reduce speckle noise. The technique eliminates speckle noise without employing any moving mechanical parts and requires no additional electronics or extra optical elements except one mirror and one beam splitter. An experimental result showing excellent reduction of speckle is presented.

Design and fabrication of high-efficiency beam splitters and beam deflectors for integrated planar micro-optic systems

Abstract: High-frequency gratings with rectangular-groove profiles are used to generate high-efficiency beam splitters and beam deflectors The effects of the grating design parameters, ie, period, groove depth, duty cycle, number of phase levels, and polarization state (TE and TM) of the incoming signal, are considered The case of the binary beam splitter grating is analyzed by using rigorous electromagnetic grating analysis Fabrication techniques are presented in which three different lithographic techniques are considered (optical contact, deep-UV stepper reduction, and electron-beam direct write) Experimental results of 97% efficiency for the beam splitter grating and up to 80% for the beam deflector grating are reported

Magneto-optical beam splitter for atoms.

Abstract: We report an experimental demonstration of diffraction of ${\mathrm{He}}^{\mathrm{*}}$ atoms from a magneto-optical grating. The grating was produced by the interaction of three-level atoms with a light field of spatially varying polarization and a magnetic field. For a light shift matched to the Zeeman shift, a two-peaked diffraction pattern was observed, corresponding to a momentum splitting of 42\ensuremath{\Elzxh}k. The effect of changing the polarizations of the light field was investigated. The diffraction from the magneto-optical grating is compared directly with the diffraction of two-level atoms from a standing light wave and it is shown, that the magneto-optical interaction leads to more efficient coupling into high order momentum states.

Optical beam splitting lens

Abstract: An integrated optical system for the simultaneous viewing of scenery 40 and of informative data 38 superpositioned on said scenery, consists of a lens 30 divided into two parts by a beam splitter 36, said lens having a first surface 31 facing the viewer, and a second partially reflecting convex surface 32 on the main optical axis 33, defining a partially reflecting concave mirror 32' facing the first surface, said lens having a third surface 37 parallel to the main optical axis or at an acute angle therewith, facing the source 38, said beam splitter 36 extending from the upper part of the first surface 31 to the lower part of said concave mirror 32', so that the source of the data is at the focus of the said concave surface, so that the beam coming from the data source 38 enters through the third surface, is reflected by the beam splitter toward the said partially reflecting concave mirror and from this via the beam splitter to the first surface to the eye 39 of the viewer. Lens 30 may have zero power (Figs. 3, 4, 8) and may be a doublet (Figs. 4, 5, 8).

Importance of rotational beam alignment in the generation of second harmonic errors in laser heterodyne interferometry

Abstract: We show, using a Jones matrix analysis, that rotating the two orthogonal linearly polarized inputs of a heterodyne interferometer relative to the polarizing beam splitter axes, produces second harmonic errors in an otherwise ideal interferometer. The error undergoes two cycles as the optical pathlength difference changes from 0 to 2pi. This behaviour is distinct from previously reported periodic errors resulting from polarization leakage and frequency mixing. It is found that as the angular misalignment increases, the amplitude of the periodic errors also increases, and may reach substantial values.

Polarization conversion unit, polarization illumination apparatus provided with the unit, and projector provided with the apparatus

Abstract: A polarization conversion unit is disclosed. In the unit, a definitely polarized light emitted from a light source is divided into a pair of lights differing in polarized state and are caused to be incident on the optical components including the polarizing beam splitter. The plane of polarization of one of the paired polarized light is rotated to be coincident with the plane of polarization of the other light by the optical components, so that the paired lights with the same plane of polarization are caused to be separately emitted. The optical component has a plano-convex lens which has a positive power and which is arranged at an exit side where the paired lights are separately emitted. The lens has a focal point at a position further than the position of the surface to be illuminated.

Optical information reproducing apparatus

Abstract: An optical information reproducing apparatus of the invention includes a light emitting and receiving unit and an optical system. The optical system converges light from the light emitting and receiving unit on a recording medium and converges the light after reflected by the recording medium. The light emitting and receiving unit includes: a semiconductor laser device disposed on a substrate for generating light; a photo detector formed, integrally with the substrate, on the substrate on which the semiconductor laser device is disposed, for outputting a signal corresponding to the intensity of light incident thereon; and a beam splitter provided on an optical axis of the reflected light, the beam splitter leading part of the reflected light to the photo detector.

Compact optical head

Abstract: A compact optical head for reading or writing data on an optical disc is disclosed wherein the optical head comprises an integrated laser diode/photodetector package, a half-cube beamsplitter, and an objective lens. Light emitted from a diode laser is in transmitted to the beamsplitter and deflected towards the objective lens. The objective lens focuses the incident light on a focal point on the surface of the disc. A reflected beam travels along the same path as the incident light and is deflected by the beamsplitter toward a photodetector contained in the integrated package, wherein the photodetector is displaced from the laser diode. Other embodiments of the beamsplitter are disclosed which include a wedged plate for transmitting collimated light emitted from the laser diode, and a cylindrical lens for introducing astigmatism into the reflected beam. The present invention provides a substantial reduction in the size and volume required by the optical head, advantageously allowing the head to be easily integrated with an actuator for focussing and tracking the incident beam on the disc.

Interferometric phase measurement

Abstract: A phase measuring method and apparatus are described for determining the phase difference between two polarized light beams which, in contrast to prior phase measuring techniques, permits simultaneous signal evaluation. The orthogonally polarized light beams with the phase difference are initially split by a beam splitter into several partial beam pairs which, by means of a lens are focused as parallel beams into a phase shifter, a polarizer, and an array of light sensors. Phase differences of the light beams create intensity differences between the beams received by the different light sensors. High measuring speed and accuracy are thus provided. When combined with means for directing two spaced orthogonally polarized beams on a surface, the method and apparatus can be used to determine height differences along the surface.

Beam array generation and holographic interconnections in a free-space optical switching network.

Abstract: Free-space photonic switching systems that optically interconnect large arrays of simple processing elements have already been demonstrated [ IEEE Photon. Technol. Lett.2, 438, 600 ( 1990); Appl. Opt.31, 5431 ( 1992); Electron. Lett.27, 1869 ( 1991)]. In these system experiments, diffractive optical elements served as critical components that provided functionality not easily assumed by conventional optics. In the latest optical switching network, binary phase gratings were used to generate arrays of uniform-intensity beams to illuminate modulators in the processor array. In addition, space-invariant binary phase grating designs were integral in forming the Banyan interconnection network used to link arrays in the system. Here we discuss the function, design, and performance of these diffractive elements.

Polarization-encoded optical logic operations in photorefractive media

Abstract: We propose and demonstrate optical logic operations using polarization encoding and wave mixing in photorefractive crystals. In our approach two orthogonal polarization states of light beams are used to represent respective logic values of 1 and 0. All 16 two-input logic operations can be easily achieved by use of the recording and readout of photoinduced volume gratings in photorefractive crystals. An optical full adder is also proposed and demonstrated.

Non invasive method and instrument for measuring blood sugar level

Abstract: of EP0670143A laser beam, the wavelength of which is modulated periodically, emitted from a variable-wavelength semiconductor laser (11) is intensity-modulated periodically by an attenuator (12). This laser beam is separated into optical paths (13a, 13b) by a beam splitter (14) and applied via the optical path (13a) to a portion (17) at which a blood sugar level is to be measured. The intensity of the transmitting light through or reflected light of the object portion (17) and that of a laser beam in the optical path (13b) are detected by first and second detectors (21, 22) respectively, and a ratio of one of the intensities to the other is detected by a logarithmic ratio amplifier (25). A variation ratio of this ratio to a variation of a wavelength modulating wavelength is detected by a lock-in amplifier (26), and a differential spectrum signal of the absorption spectrum of glucose at the object portion is taken out from this variation rate. An arithmetic processing unit (27) is adapted to detect a blood sugar level of the object portion on the basis of this differential spectrum signal.

Method for performing temperature-controlled laser sintering

Abstract: A temperature-controlled laser sintering system includes a laser beam 12 which is focussed onto a sintering bed 38 by a focussing mirror 26 and a set of scanning mirrors 32,34. Thermal radiation 114 emitted from the sintering bed 38 are imaged to the scanning mirrors and to a dichroic beamsplitter 110 which reflects such radiation but passes the wavelength of the laser beam 12. The radiation 118 is focussed onto an optical detector 126 which provides a signal on a line 128 to a power control circuit 104. The power control circuit 104 controls a modulator 100 which modulates the power of the laser beam 112 so as to maintain the thermal radiation emission 114 (and thus the temperature at the sintering location) at a substantially constant level.

Wide range straightness measuring stem using a polarized multiplexed interferometer and centered shift measurement of beam polarization components

Abstract: A wide range straightness measuring system of the present invention accurately determines lateral and angular displacement of a probe carriage of a cartesian robot. The system includes a laser aligned with an x-axis rail of the cartesian robot system which generates a laser beam having two polarization components. A pentaprism beamsplitter is disposed on an x-axis carriage aligned with the laser. The beamsplitter orthogonally splits the laser beam into an x-axis reference beam and a y-axis reference beam. An x-axis interferometer receives the x-axis reference beam and determines a relative position value of the probe carriage measured along the x-axis. A y-axis interferometer receives the y-axis reference beam and determines a relative position value for the probe carriage measured along the y-axis. A beam monitor receives a polarized multiplexed output of the y-axis interferometer and monitors the lateral shift of the energy centroids of the beam polarization components. Both lateral and angular displacement values of the x and y-axis reference beams can be obtained by measuring the magnitude of the lateral shift.

Catadioptric reduction objective

Abstract: The invention is directed to a catadioptric reduction objective having a concave mirror, a beam splitter and several lens groups but without an additional lens group disposed between the concave mirror and the beam splitter. Catadioptric reduction objectives are disclosed having an image-side aperture of 0.52 and 0.58 for an imaging scale of 1:4 and are corrected for an unrestricted excimer laser for use in submicronlithography.

High repetition rate, mode locked, figure eight laser with extracavity feedback

Abstract: An optical pulse generator for producing mode-locked optical pulses comprises: a beam splitter; first and second optical loops coupled together by the beam splitter so as to define a figure eight optical path in which a light beam propagating toward the beam splitter in one of the first and second optical loops is split by the beam splitter to form two light beams propagating in opposite directions around the other one of the first and second optical loops; a direction dependent loss element disposed in the first optical loop for reducing the intensity of light propagating in a predetermined direction around the first optical loop; a nonlinear element disposed in the second optical loop and having an intensity dependent nonlinear optical transmission characteristic; an optical gain medium disposed in a selected one of the first and second optical loops; coupling apparatus for coupling pump light into the selected one of said first and second optical loops having the gain medium, and for coupling mode-locked optical pulses out of the optical pulse generator; and a feedback structure, coupled to the coupling apparatus, being responsive to light propagating therethrough for controlling the repetition rate of the mode-locked optical pulses.

Polarization-sensitive beam splitter, method of manufacturing such a beam splitter and magneto-optical scanning device including such a beam splitter

Abstract: A polarization-sensitive beam splitter comprising at least one transparent wedge-shaped element of a birefringent material is made by providing each one of two substrate plates with an orientation layer, whereafter the substrate plates are arranged with their orientation layers facing each other while forming a wedge-shaped interspace. The interspace is filled with a liquid crystalline monomer composition, which is subsequently cured while forming a wedge-shaped element of a uniaxially oriented polymer material. After possible removal of the substrate plates, two or three of such wedge-shaped elements can be joined to a Wollaston prism for use in the pick-up element of a magneto-optical recording system.

Method and apparatus for examining an object

Abstract: In order to examine an object with radiation and measure the intensity of radiation used to illuminate the object, radiation is directed onto a wavelength selective mirror (31). In a first position, the mirror (31) reflects the illuminating radiation to a beam splitter (30) which passes the radiation to a detector (34). In a second position the mirror (31) directs the radiation to an object (33), radiation of the selected wavelength emanating from the object being reflected by the mirror via beam splitter (30) to the detector (34). The mirror (31) is rotated between the first and second position. In order to classify a diamond as natural or synthetic, a first signal is derived dependent upon the intensity of ultra-violet radiation transmitted by the diamond at 254 nm, and a second signal is derived dependent upon the intensity of radiation transmitted by the diamond at 365 nm and the diamond is classified as being definitely natural if the first signal is substantially greater than the second signal.

Display system employing acoustro-optic tunable filter

Abstract: An acousto-optic tunable filter (AOTF) is employed to generate a display by driving the AOTF with an RF electrical signal comprising modulated red, green, and blue video scan line signals and scanning the AOTF with a linearly polarized, pulsed light beam, resulting in encoding of color video columns (scan lines) of an input video image into vertical columns of the AOTF output beam. The AOTF is illuminated periodically as each acoustically-encoded scan line fills the cell aperture of the AOTF. A polarizing beam splitter removes the unused first order beam component of the AOTF output and, if desired, overlays a real world scene on the output plane. Resolutions as high as 30,000 lines are possible, providing holographic display capability.

Diffraction characteristics of surface-relief gratings

Abstract: We present a theoretical and experimental study on the diffraction characteristics of gratings, with particular attention focused on the effects of polarization. The goal of our study is to develop multifunctional devices for use in a pickup head for optical storage systems. Experiments and numerical calculations are carried out systematically to determine the effects of the grating parameters of depth, period, and duty cycle and also the effects of the incident-wave parameters of incident angle, wavelength, and polarization. It is shown that, theoretically, the diffraction efficiency can reach 100% for both TE and TM polarizations that are incident at the Bragg angle. The simple dispersion characteristics of the Floquet modes are invoked to explain the different diffraction behaviors between the two polarizations. We conclude that a suitably designed grating may split an incident light beam of mixed polarizations into two beams of the opposite polarizations, each propagating in a different direction. Based on the numerical results, simple criteria are suggested for the design of the grating structures for both polarizing and nonpolarizing beam splitters.