Showing papers on "Beam splitter published in 1996"

Can Two-photon Interference be Considered the Interference of Two Photons?

Abstract: We report on a ``postponed compensation'' experiment in which the observed two-photon entangled state interference cannot be pictured in terms of the overlap of the two individual photon wave packets of a parametric down-conversion pair on a beam splitter. In the sense of a quantum eraser, the distinguishability of the different two-photon Feynman amplitudes leading to a coincidence detection is removed by delaying the compensation until after the output of an unbalanced two-photon interferometer.

Efficient optical system for a high resolution projection display employing reflection light valves

Abstract: An optical system is described consisting of reflection birefringent light valves, polarizing beam splitter, color image combining prisms, illumination system, projection lens, filters for color and contrast control, and screen placed in a configuration offering advantages for a high resolution color display. The system includes a quarter wave plate positioned to suppress stray reflection from the projection lens. The system also includes a second quarter wave plate disposed on the screen and a polarizing film disposed on the second quarter wave plate to suppress ambient light from illuminating the screen and entering the system.

Polarizing beam splitter based on the anisotropic spectral reflectivity characteristic of form-birefringent multilayer gratings.

Abstract: We introduce a novel polarizing beam splitter that uses the anisotropic spectral reflectivity (ASR) characteristic of a high-spatial-frequency multilayer binary grating. Such ASR effects allow us to design an optical element that is transparent for TM polarization and reflective for TE polarization. For normally incident light our element acts as a polarization-selective mirror. The properties of this polarizing beam splitter are investigated with rigorous coupled-wave analysis. The design results show that an ASR polarizing beam splitter can provide a high polarization extinction ratio for optical waves from a wide range of incident angles and a broad optical spectral bandwidth.

Low-cost light-weight head-mounted virtual-image projection display with low moments of inertia and low center of gravity

Abstract: A head-mounted display device (10) offers light weight, a low center of gravity, and low moments of inertia about the azimuthal and elevational axes of head movement. The display device (10) employs an angulated beam splitter mirror (16) disposed between a user's (22) eye (20) and an inner combiner surface (18a) of a visor (28). A projector (36) is carried laterally of the user's eye with a low center of gravity and a position close to the horizontal axis of elevational movement of the head. This projector (36) includes an image source (12) and a compact light-weight relay optics module (14) along with a projection fold mirror (30) disposed at eye level and laterally of the beam splitter mirror (16) to project image light to the beam splitter mirror (16). The beam splitter mirror (16) reflects the light onto the inner surface (18a) of the combiner (18) for reflection back through the beam splitter mirror (16) and to the user's eye (20). Alternative embodiments provide for color correction, or for mono-chrome image projection at even lighter weight. An alternative embodiment provides for both color correction and weight nearly as light as the monochrome version by use of diffractive lenses in the relay optics module.

Visible broadband, wide-angle,thin-film multilayer polarizing beam splitter.

Abstract: A method is described for the design of a thin-film all-dielectric polarizing beam splitter in which the transmittances for p- and s-polarized light are greater than 0.96 and less than 0.03, respectively, throughout the spectral region extending from 0.40 to 0.70 µm, and for an angular field of 12° measured in air.

Thin film polarizing device

Abstract: A thin film polarizing device has first and second light transmissive substrates in the form of prisms and a plurality of thin film layers disposed between the prisms. The thin film layers and have predetermined thicknesses and refractive indices which allow unpolarized incident light to be separated into s-polarized and p-polarized light beams. Both frustrated total internal reflection and thin film interference are simultaneously employed to allow s-polarized light to be transmitted and p-polarized light to be reflected over a wide range of wavelengths and angles of incidence. The polarizing device may be used as a polarizer or a polarizer beam splitter.

Optical scanning apparatus including an image reading section and an image printing section that share a common optical system and a method of printing and reading an image using the common optical system

Abstract: An optical scanning apparatus includes a semiconductor laser, a polygonal mirror as a deflector for scanning a light beam from the laser, a photosensitive drum for forming an electrostatic latent image, a converging lens for converging the light beam from the laser onto the photosensitive drum, and a reflection mirror located between the deflector and the photosensitive drum. The reflection mirror is adapted to reflect the light beam so that a light beam reflected by the reflection mirror is used to read a source document placed at a position that is the conjugate of the position of the photosensitive drum surface with respect to the converging device. Inside the casing of the semiconductor laser are a beam splitter for light path separation and a photosensor. The apparatus has an image reader section and a laser printer section, which share a common optical system, thus providing a compact design and cost reduction and also equalizes the accuracy of image reading and printing.

Polarization independent electro-optic modulator

Abstract: A polarization insensitive electro-optic modulator is constructed by providing a polarization beamsplitter to separate an incoming light beam into two orthogonally plane polarized beams. Each of the polarized beams passes through a separate electro-optic modulator where each beam is modulated by the same data signal. After modulation the beams are combined to yield a modulated beam having modulated components that are orthogonally polarized. Not only is this device insensitive to changes in polarization of the input beam, the final modulated beam can be detected by optical receivers without regard to polarization alignment of the modulated beam and the receiver.

Measurement of subpicosecond electron pulses.

Abstract: A bunch-length measuring method has been developed to measure the subpicosecond electron pulses generated at the Stanford University Short Intense Electron Source (SUNSHINE) facility. This method utilizes a far-infrared Michelson interferometer to measure coherent transition radiation emitted at wavelengths longer than or equal to the bunch length via optical autocorrelation. To analyze the measurement, a simple and systematic way has also been developed, which considers interference effects on the interferogram caused by the beam splitter; hence the electron bunch length can be easily obtained from the measurement. This simple, low-cost, frequency-resolved autocorrelation method demonstrates subpicosecond resolving power that cannot be achieved by existing time-resolved methods.

Reference laser beam sampling apparatus

Abstract: Apparatus for sampling a laser beam used in an analytical instrument, e.g., a clinical hematology or flow cytometer instrument, for measuring absorption by particles suspended in a stream moving through a flow cell. The laser beam is typically passed through a mask, e.g., a beam shaping aperture, to shape the beam. The shaped beam is then passed through a beam splitter, located downstream of the beam shaping aperture, so that one part of the shaped beam strikes the flow cell (e.g., is focused onto the moving stream of particles), and a second part is diverted to obtain a reference measurement of the beam about to strike the flow cell. An absorption measurement is obtained of the light passing through the flow cell, and a difference circuit is used to obtain a difference signal relating the differences between the measured absorption and the unabsorbed reference sample of the initial beam intensity. The laser source may be a laser diode and a spatial filter may be used to produce the laser beam to be passed through the beam shaping aperture.

Optical head device

Abstract: An optical head device which has: a light source for projecting laser light; a beam splitter for reflecting the laser light onto an optical disk; an objective for focusing the reflected light on an information recording surface of the optical disk to form a micro spot thereon; an optical detector for receiving a light component transmitted through the beam splitter of light reflected on the information recording surface and converting the light component into an electrical signal; a variable aperture device for varying a diameter of the micro spot according to an external input, the variable aperture device being provided between the beam splitter and the objective; and a variable rotation angle diffraction grating for varying a rotation angle of a sub-beam for tracking of the laser light according to an external input, the variable rotation angle diffraction grating being provided between the light source and the beam splitter

Design of a static Fourier-transform spectrometer with increased field of view.

Abstract: We present several novel designs of static Fourier-transform spectrometers based on Wollaston prisms. By numerical modeling we show the increased field of view that can be obtained when an achromatic half-wave plate is included between the prisms or when prisms fabricated from positive and negative birefringent materials are combined. In addition, we model how a single Wollaston prism with an inclined optic axis produces a fringe plane localized behind its exit face, thus enabling the design of a static Fourier-transform spectrometer based on a single Wollaston prism.

Optical quadrature interferometry utilizing polarization to obtain in-phase and quadrature information

Abstract: An optical quadrature interferometer is presented. The optical quadrature interferometer uses a different state of polarization in each of two arms of the interferometer. A light beam is split into two beams by a beamsplitter, each beam directed to a respective arm of the interferometer. In one arm, the measurement arm, the light beam is directed through a linear polarizer and a quarter wave plate to produce circularly polarized light, and then to a target being measured. In the other arm, the to reference arm, the light beam is not subject to any change in polarization. After the light beams have traversed their respective arms, the light beams are combined by a recombining beamsplitter. As such, upon the beams of each arm being recombined, a polarizing element is used to separate the combined light beam into two separate fields which are in quadrature with each other. An image processing algorithm can then obtain the in-phase and quadrature components of the signal in order to construct an image of the target based on the magnitude and phase of the recombined light beam.

Orthogonal-scanning microscope objective for vertical-scanning and phase-shifting interferometry

Abstract: A broad-bandwidth interferometric device is adapted for longitudinal insertion into a cylinder cavity to produce irradiance signals at multiple vertical-scanning positions as a function of optical path differences between a reference mirror incorporated in the probe and the cylinder-wall surface. The light-source beam is passed through an objective lens placed longitudinally in the cylinder and then divided by a beam splitter disposed in fixed relation to the cylinder wall to produce a test beam directed radially to the wall and a reference beam directed axially to a reference mirror disposed in fixed relation to the lens. During scanning, the objective lens and reference mirror are translated together, while the beam splitter remains stationary with respect to the cylinder wall, thereby varying the position of the focal point of the test beam and providing the vertical-scanning effect required to produce interference fringes and a corresponding map of the tested cylinder surface. In order to reduce the length of the instrument, the reference beam may be folded to the side by a reflective surface and the reference mirror may be positioned perpendicularly to the main axis of the instrument. In that case, the lens, fold mirror and reference mirror are all translated together, while the beam splitter remains stationary and fixed with the test surface.

Realization of novel monolithic free-space optical disk pickup heads by surface micromachining.

Abstract: A novel monolithic free-space optical disk pickup head has been fabricated by micromachined micro-optical bench technology. The pickup head contains a self-aligned semiconductor edge-emitting laser, a collimating lens, a beam splitter, two focusing lenses, and two 45° mirrors. All optical components are built monolithically on Si substrates. The 45° mirror directs the optical output beam in the surface-normal direction. This novel design could significantly reduce the size and the weight of the optical pickup head as well as the cost of the assembly processes. The weight reduction could also greatly increase the data access rate.

Field Commutation Relations in Optical Cavities.

Abstract: We introduce a simple quantum theory of the lossy beam splitter. When applied to describe a Fabry-P\'erot cavity this leads to apparently anomalous commutation relations for the intracavity operators. We show that these unfamiliar properties are nevertheless consistent with the fundamental canonical commutator for the vector potential and electric field operators. This result is derived as a consequence of causality as applied to the properties of mirror reflection coefficients.

Dual-wavelength optical recording head utilizing grating beam splitter and integrated laser and detectors

Abstract: In an optical system for generating a radiation beam to be applied to a data track of an optical storage medium is disclosed. The system includes first and second optical light sources producing light at different wavelengths and optics for receiving light from the first and second sources and including a selective beam splitter for selectively applying light from each optical light source to the data track of the optical storage medium and defining an optical axis for each optical light source along which light is projected to the data track.

Integrated controlled intensity laser-based light source using diffraction, scattering and transmission

Abstract: An integrated laser-based light source that generates an output light beam having a controlled intensity. The light source comprises a package, a laser, a light sensor, and a beam splitter. The beam splitter is mounted in the package, together with the laser and the light sensor. The laser has one and only one light-emitting face from which it radiates a light beam as a radiated light beam. The light sensor generates an electrical signal representing the intensity of light energy falling on it. The beam splitter divides the radiated light beam into a fraction and a remainder, the remainder being the output light beam. The beam splitter operates by diffraction, scattering, or transmission to direct the fraction of the radiated light beam towards the light sensor.

Photon statistics of conditional output states of lossless beam splitter

Abstract: When an observation is carried out at one of the two output ports of a lossless beam splitter, photon statistics of a conditional output state in the unobserved output port are investigated for several input states. Observations at the output port are carried out by means of photon counting, heterodyne detection and homodyne detection. The dependence of the average value of the photon number and the Q factor of the conditional output state on the measurement outcome are investigated in detail. The statistical distance between the input and conditional output states is also considered. Furthermore, it is shown that the relationship between the input and conditional output states of the beam splitter is characterized as a conditional isometric process.

High efficiency homogeneous polarization converter

Abstract: A polarization converter for polarizing a light beam by converting all light waves to the same orientation comprises: 1) a first beam dividing matrix (32) of refractory material for dividing a single, large light beam (34) into smaller sub-beams (36), 2) a second beam focusing matrix (37) for polarizing select portions of the sub-beams, and 3) a series of narrow and shallow polarizing cells. The second beam focusing matrix further comprises a plurality of concave lenses (48) for redirecting each sub-beam and quarter wave retarders (54) disposed in alignment with, and adjacent to, the reflective side of an equal plurality of mirror segments. The polarizing cells include either a first beamsplitter or a second beamsplitter, where the first beamsplitters and second beamsplitters are disposed in opposing diagonal fashion and in an alternating manner. Lightwaves of a selected polarization pass directly through the first beamsplitter and out of the polarizing cell, while all other lightwaves are horizontally reflected by the first beamsplitter and directed onto the second beamsplitter where they are redirected toward the quarter wave retarder. The reflected light passes through the quarter wave retarder, reflects off of the mirror and again passes through the quarter wave retarder.

Tunable optical filter having beam splitter and movable film filter

Abstract: A tunable filter module which can automatically make the center wavelength in the passband coincident with the center wavelength of a signal light beam according to variations in wavelength of the signal light beam. The tunable filter module includes a beam splitting mechanism for splitting an incident signal light beam into a first beam undeviated, a second beam deflected to one side of the first beam; and a third beam deflected to another side of the first beam, and a multilayer film filter located so as to transmit the first, second, and third beams. A first photodetector is located so as to detect the second beam, and a second photodetector is located so as to detect the third beam. A comparator is connected to the first and second photodetectors to compare outputs from the first and second photodetectors and output a differential signal indicative of the difference between these outputs. A tilt angle of the multilayer film filter is changed according to the differential signal so that the center wavelength in the passband of the multilayer film filter comes into coincidence with the center wavelength of the signal light beam.

Narrow wavelength polarizing beamsplitter

Abstract: A polarizing beamsplitter includes a gradient index film, such as a rugate filter, embedded in an optical medium. The rugate filter is comprises a thin film having a sinusoidal variation in refractive index through its thickness. The embedding medium may include a pair of prisms with the rugate filter between joining faces of the prisms. The rugate filter is embedded so that an incident beam in the embedding medium forms an angle with respect to a normal from the plane of the rugate filter. Embedded at a non-orthogonal angle, the rugate filter is highly transmissive for both the p- and s-polarized broadband components of the incident beam. The beamsplitter is highly reflective, however, at an s-polarization narrow wavelength reflection band determined by the refractive index variations of the rugate filter. Polarizing beamsplitters may be fabricated with multiple reflection bands, including reflection bands in spectral regions other than the visible spectrum. The polarizing beamsplitter can function as a polarizer, a beamsplitter, or a polarizing beamsplitter. An advantage of the invention is efficient reflection of s-polarized light at specific narrow wavelengths with high transmission of s-polarizations at all other wavelengths and p-polarizations at all wavelengths.

Optical pickup having two objective lenses

Abstract: An optical pickup (1) for irradiating a first recording medium and a second recording medium with light, at least one of the substrate thickness and the refractive index of the first recording medium being different from that of the second recording medium, where the optical pickup includes: a light source (23) for emitting the light; a polarized beam splitter (22) for receiving the light and for transmitting at least a portion of the light while reflecting the remaining portion of the light depending on the polarization direction of the light; a first objective (5) lens for focusing the portion of the light reflected by the polarized beam splitter (22) onto the first recording medium; and a second objective lens (4) for focusing the portion of the light transmitted through the polarized beam splitter (22) onto the second recording medium.

Electro-optical device wherein orientation layers have grating structure and comprises birefringent material with refractive indices equal to electro-optic medium

Abstract: Switchable electro-optic medium (2) between two substrates (3, 4) at least one of which carries a grating structure (7, 8) at the side of the electro-optic medium, which grating structure has refractive indices which are substantially identical to those of the medium in the non-isotropic state. In the isotropic state diffraction occurs at the grating structure due to a difference in refractive index so that the central beam (11) decreases in intensity. Based on this principle, light shutters for, for example projection display but also beam splitters, colour selectors and beam deflectors may be realized.

Polarization mode dispersion-free circulator

Abstract: A high performance optical circulator is formed by a polarization beam splitter and optical port assemblies. The polarization beam splitter is formed by two prisms with an interface between the prisms. The interface transmits linearly polarized light directed at the interface in directions responsive to a polarization orientation of linearly polarized light. The optical port assemblies are arranged with respect to the polarization beam splitter so that light from one port assembly is transmitted by the polarization beam splitter interface to another optical port assembly and light from this optical port assembly is transmitted by the beam splitter interface to still another optical port assembly.

Dual mode illumination system for optical inspection

Abstract: A dual mode illumination system for optical inspection of products for surface defects and defects in holes in the product includes a first light source for providing illumination along an axis of one or more holes in the product to be inspected, the first light source being positioned on a first side of the product, a second light source providing illumination of the surface of the second side of the product to be inspected, a beam splitter for redirecting light from the second light source to a light sensor while passing light from the first light source to the light sensor. The second light source may be located adjacent to a second side of the product to be tested with the axis of illumination parallel to a major plane of the product. The light sensor may be a video camera connected to a data processing and display system.