Showing papers on "Beam splitter published in 1987"

Design Of A Long Trace Surface Profiler

Abstract: The design of a long-trace surface profiler for the non-contact measurement of surface profile, slope error and curvature on cylindrical synchrotron radiation (SR) mirror is pre-sented here. The optical system is based upon the concept of a pencil-beam interferometer with an inherent large depth-of-field. The key feature of the optical system is the zero-path-difference beam splitter, which separates the laser beam into two colinear, variable-separation probe beams. A linear array detector is used to record the interference fringe in the image, and analysis of the fringe location as a function of scan position allows one to reconstruct the surface profile. The optical head is mounted on an air bearing slide with the capability to measure 38" long aspheric optics, typical of those encountered in SR applications. A novel feature of the optical system is the use of a transverse "outrigger" beam which provides information on the relative alignment of the scan axis to the cylinder optic symmetry axis.

Composite visible/thermal-infrared imaging apparatus

Abstract: Multispectral imaging apparatus for producing a composite dual wavelength visible/infrared image includes a wavelength independent focus reflective optical system for receiving a visible and infrared radiation from a scene and for providing a focused beam of radiation, a beam splitter for splitting the beam into a beam of visible radiation and a beam of infrared radiation, a visible radiation detector for receiving the visible radiation and for producing a first signal, and infrared radiation detector for receiving the infrared radiation and for producing a second signal, and a signal processing and display system for converting the first and second signals into video signals corresponding to a visible black and white image of the scene and a step-tone or false color infrared image of the scene. The images are combined in exact spatial registration to produce a composite image comprising a black and white visible image with portions of the image highlighted in color in accordance with the infrared radiation received from corresponding portions of the scene.

Color corrector for embedded prisms

Abstract: An embedded polarizing beamsplitter employed in a liquid crystal light valve color projector introduces lateral chromatic aberration of complex distribution that degrades contrast and resolution of the projected image. Color correction is provided to substantially eliminate any noticeable lateral chromatic aberration by replacing the output window of the prism with an optical wedge made of the same material as the embedded prism plate of the beamsplitter.

Transmission and reception module for a bidirectional communication network

Abstract: A transmission and reception module for a bidirectional optical communication network characterized by a housing containing a laser diode, a first spherical lens for focussing the output of the laser diode on a first beam path, a second spherical lens arranged on the first beam path for focussing the light from the first lens at a focal point at which an end face of an optical fiber is positioned, a beam splitter which is at least partially transmissive to light of a first wavelength from the laser diode and partially reflective of light of a second wavelength being emitted from the fiber into a second beam path on which a detector is positioned. To improve the positioning, the first lens and the laser diode are mounted on a carrier member in a fixed relationship which enables assembling the device with less problems with maladjustment.

Wigner-function Description of Quantum Noise in Interferometers

Abstract: A quantum-statistical description of noise in interferometers is given in terms of the Wigner distribution function. The interferometer may contain an amplifier in one of its arms. The input field can be in a variety of states such as a Fock state, a coherent state or a squeezed coherent state. The Wigner function of the output field at the detector is shown to have a general Gaussian form with non-zero complex field amplitude and with other parameters related to the characteristics of the input field, amplifier and beam splitters, etc. An explicit form of the photon-number distribution is given. Higher-order correlations of the output field can be obtained from the Gaussian property of the Wigner function.

Optical micropressure transducer

Abstract: A thin diaphragm (22) receives pressure across one side and faces a beam splitter (25) on the other side. The beam splitter (25) is integrally attached to the diaphragm (22) and serves as a local optical reference plane for the entire assembly. A small cavity (40) is formed between the diaphragm (22) and beam splitter (25). Coherent light from a light source (49) is partially reflected at the beam splitter (25). The remainder of the light is reflected from the diaphragm (22). The reflected beams recombine at a detection point and form an interference pattern. The phase difference between the reflected beams is a function of the amount of deflection of the diaphragm (22). The interference pattern being indicative of the deflection of the diaphragm is received by a light detector (34). Optical calibration of the assembly is a function of the distance between the diaphragm (22) and beam splitter (25) which remains as predefined because the beam splitter (25) is integral with the diaphragm. A vent (28) in the small cavity enables the diaphragm (22) to sense small pressures with increased sensitivity. Fiber optics enable use of the assembly in high temperatures.

Wide tolerance, modulated blue laser source

Abstract: A process and apparatus are disclosed for producing a beam of coherent radiation at essentially 459 nm by mixing, in a nonlinear crystal consisting essentially of KTP, two laser beams, one at essentially 1064 nm and the other at essentially 808 nm. The 1064 nm radiation is derived from a Nd:YAG laser that consists of an input mirror, an output mirror and a Nd:YAG crystal, and contains also the KTP crystal. The Nd:YAG laser is pumped by an essentially 808 nm semiconductor diode laser beam, which passes through the input mirror and through the KTP crystal into the Nd:YAG laser crystal where it is absorbed. The 1064 nm radiation oscillating inside the Nd:YAG laser resonator is mixed either with the said 808 nm pump beam or with 808 nm radiation provided by a second semiconductor diode laser whose light is coupled with the 1064 nm beam using a beamsplitter. The essentially 459 nm beam passes through the output mirror to a utilization device.

Differential plane mirror having beamsplitter/beam folder assembly

Abstract: A differential plane mirror interferometer comprises a source (10) which emits a light beam containing two linear orthogonally polarized components; a beamsplitter/beam folder assembly (16, 16A) for converting the input beam into two separated, parallel, orthogonally polarized beams; a half-wave retardation plate (29A, 29) located in one of the separated beams to produce two separated parallel beams with the same polarization; means including a polarizing beamsplitter (44), for causing each of the separated parallel beams with the same polarization to be reflected twice by one of two plane mirrors (71, 70) to produce two parallel output beams with the same polarization; a half-wave retardation plate (29B, 29) located in one of the separated parallel output beams, with the beamsplitter/beam folder assembly (16, 16B) converting the two separated parallel orthogonally polarized output beams into a single output beam in which the phase difference between the two polarization components of the single output beam is directly proportional to the optical path length between the two plane mirrors (70, 71); a polarizer (81) for mixing the orthogonal components of the output beam; a photoelectric detector (83) to produce the measurement signal; and an electronic module (90) to indicate the phase difference which is directly proportional to the changes in the optical path length between the two plane mirrors.

Angle measuring interferometer

Abstract: An angle measuring interferometer comprises a source (10) which emits a light beam containing two orthogonally polarized components of different frequencies; a source of a stabilized electrical reference signal (11) of a frequency corresponding to a difference frequency between the two components of the light beam; means, such as a tilted shear plate (16) or a beamsplitter/beam folder assembly (116, 116A) for converting the input beam into two separated, parallel, orthogonally polarized beams; a half-wave retardation plate (29A, 29) located in one of the separated beams for converting the two separated parallel orthogonally polarized beams into two separated parallel beams with the same polarization and frequency difference; means including a polarizing beamsplitter (44), for causing each of the separated different frequency parallel beams with the same polarization to be reflected once by each of two plane mirrors (71, 70) to produce two parallel output beams with the same polarization; a half-wave retardation plate (29B, 29) located in one of the separated parallel output beams, for converting the two separated parallel output beams of the same polarization into two separated parallel output beams with orthogonal polarization, with means, such as the tilted shear plate (16) or the beamsplitter/beam folder assembly (116, 116B), converting the two separated parallel orthogonally polarized output beams into a single output beam in which the phase difference, "δ", between the two frequency components of the single output beam is directly proportional to the angle, "θ", between the two plane mirrors (70, 71); a polarizer (81) for mixing the orthogonal components of the output beam; a photoelectric detector (83) to produce the measurement signal; and a phase/meter accumulator (90) to indicate the phase difference, "Δδ", between the reference and measurement signals which is directly proportional to the changes in the angular orientation, "Δθ", between the two plane mirrors (70, 71).

Optical position sensor using coherent detection and polarization preserving optical fiber

Abstract: A precision optical distance measuring device utilizes coherent optical detection for extreme precision, and polarization preserving fiber to enable its use in limited access environments. A laser diode provides a linearly polarized source light beam which is directed to a polarizing beam splitter. The source beam passes through the beam splitter and is focused by a lens into a polarization preserving fiber where it travels along one optical axis toward a probe head disposed at the target location. In the probe head, the source beam is focused by a lens onto the target. After focusing, the source beam is passed through a quarter-wave plate. The interface between ambient air and the target-side of the quarter-wave plate reflects a local oscillator beam back through the quarter-wave plate. Meanwhile, the source beam is reflected from the target as a return beam. Mixing of the two beams occurs at the interface and the mixed beam is focused back into the polarization preserving fiber where it is transmitted along a second transmission axis of the fiber. The mixed beam emerges from the fiber and is reflected by the polarizing beam splitter along a second optical axis. The mixed beam is then focused by a detection lens onto a photo detector which coherently detects the mixed beam. The source laser beam is frequency swept so that the photo detector provides an output signal regarding the precise distance between the probe head and the target.

Liquid crystal image projection with multicolor prepolarizing system

Abstract: An optical system for a full color liquid crystal light valve image projector is provided. The invention includes a first prepolarizer for separating from a first beam light of first and second colors and a first polarization state and a second prepolarizer for separating from the first beam light of a third color and a second polarization state. The resultant first beam contains light of a third color and first polarization state and light of first and second colors and second polarization state. A polarization selective beamsplitter is provided in the optical path of the first beam for transmitting, in a second beam, light in the first beam having the first polarization state and reflecting, in a third beam, light in the first beam having the second polarization state. A color selective beamsplitter is included for transmitting, in a fourth beam, light in the third beam having a first color and for reflecting, in a fifth beam, light in the third beam having a second color. In the illustrative embodiments, the invention includes first and second reflective surfaces for reflecting the second and fifth beams respectively into a parallel coplanar relation with the fourth beam. The invention permits the light valves and associated CRT assemblies to be located in a parallel coplanar relation. The present invention thereby provides a compact design for a liquid crystal light valve image projection systems.

Laser alignment system

Abstract: A system for monitoring changes in shape of a structure employs a laser source attached to the structure and a set of beam splitters mounted at various locations on the structure and arranged to route portions of a laser beam produced by the laser source into various video cameras also mounted on the structure. Each video camera includes a photodetector array and produces an output signal indicating the intensity of light detected by each photodetector of the array, thereby indicating the beam intensity distribution in a corresponding plane of interest. The video output signal of each camera is digitized and stored as an intensity data array in the memory of a digital computer. The computer calculates from the intensity data array the position of the centroid of the beam with respect to a reference point on the plane of interest using a least squares fit of the intensity data to a two-dimensional Gaussian intensity distribution. Any deviation of the calculated beam centroid position from the reference point indicates a change in jig shape in the plane of interest. The reference point in each plane of interest is determined by a least squares fit of the computed beam centroids in several planes to a line.

Wave-particle duality for single photons

Abstract: By use of an atomic radiative cascade, we have been able to produce single photon states of the light. This light has been submitted to two different experiments. The first one shows an anticorrelation on both sides of a beam splitter (corpuscle-like behaviour). The second one yields interferences (wave-like behaviour).

Four-channel polarimeter for time-resolved ellipsometry

Abstract: A new four-channel partial polarimeter was designed for use in time-resolved ellipsometry measurements. The device outputs four parallel, equispaced beams from a single input beam. By detecting and digitizing the intensities of these four beams, the intensity, as well as two of the three elements of the reduced Stokes vector can be determined. Since there are no moving parts to the polarimeter, time resolution is limited only by the response time of the photodetectors and the digitizers. The linear array of output beams is ideal for streak-camera detection, yielding a potential time resolution of ~1 psec. A beam splitter is described that separates the input beam into two beams, which are parallel to the input beam and whose polarizations are nearly the same as the input beam. In addition, the polarimeter is achromatic, operating in the wavelength region from 220 to 1100 nm.

Monolithic optical pick-up using an optical waveguide

Abstract: An optical pick-up for use in an optically information recording and reproducing apparatus is provided. The pick-up includes a substrate on which an optical waveguide layer is formed and a grating coupler is formed on the optical waveguide layer. Photosensors are also provided to receive light travelling along the waveguide from the grating coupler. A beam splitter is also formed on the substrate for splitting the light from the grating coupler into two separate light beams before reception by the photosensors. If the substrate is opaque, the substrate is formed with an opening through which light emitted from a light source passes. An objective lens is also provided for focusing the light emitted from the light source onto the information recording surface of an optical disc. A quarter wavelength plate may also be provided to change the nature of polarization of the light used.

Multi-beam scanning optical system

Abstract: A multi-beam scanning optical system of the present invention comprises a plurality of laser beam producing means, the producing means producing laser beams with their polarization directions parallel to one another, means for rotating the polarizing direction of at least one of the plurality of laser beams by 90 degrees, and a beam splitter means for superposing the plurality of laser beams on one another.

Optical head and optical information processor using the same

Abstract: An optical head and an optical information processor using the optical head include a light source, focusing device for focusing a light beam which is emitted from the light source, on an information medium, beam separator for isolating at least part of a light beam which is reflected from the information medium, from the light beam emitted from the light source, a beam splitter including a first polarized-light separating film which is illuminated with about a half of a light beam isolated by the beam separator, and a light detecting device having a first photodetector which receives a first light beam reflected from the first polarized-light separating film, and a second photodetector which receives a second light beam passing through the first polarized-light separating film, in a state that at least one of the first and second photodetectors is separated into a pair of light detecting elements, to make it possible to detect a magneto-optical signal and a focal error signal by the same optical system.

Magneto-optical data recording device using a wavelength and polarization-sensitive splitter

Abstract: An optical mass storage device for use in data processing systems. Two or more lasers provide separate read and write laser beams having different wavelengths. The read and write laser beams can be orthogonally polarized. A polarizing beam splitter combines the read and write beams along a common optical path to an optical head. The head directs the combined beam to a magneto-optic storage medium. A read beam is reflected back by the medium to the common path through the head. A dichroic beam splitter disposed in the common path between the head and the polarizing splitter reflects the read beam to an optical detector. If more than one write laser is necessary, a second dichroic splitter can be used to combine the multiple write beams and the read beam.

Fiber-optic gyro

Abstract: A fibre optic gyroscope for use in detecting the movement and position of aeroplanes and space vehicles, uses a laser diode(LD) at its light source, projecting through a first polariser(P1) to a beam splitter(BS1). One light path leads from the beam splitter to the polarised light separating prism (Pd1) associated with a first light detector(DET1). The second light path is via a second polariser(P2) and control portion (PC1) to the optical fibre(F1) and the optical fibre directional coupler(DCO1) in which four single-mode fibres(F1,F2,F3,F4) are coupled by two ball lenses (L3,L4) and the half mirror(HF) between them.

Optical head utilizing diffraction grating

Abstract: In an optical type head device comprising a light source for emitting a light beam, a beam splitter, a condensor lens and a light detector for receiving said light beam for photoelectric conversion wherein a diffraction grating is provided to separate the light beam into a plurality of subbeams consisting of a zero-order subbeam and other subbeams so that a focussing error of the spot of the zero-order subbeam on an optical type data storing medium is detected by the fact that the light spot of the zero-order subbeam is deformed on the light detector, and a positional error of the spot of the zero-order subbeam with respect to a data track on the optical type data storing medium is detected depending on the position of the spots of the other subbeams.

Beam splitter having a partial semitransparent layer assigned to a plurality of outgoing light beams

Abstract: In a beam splitter for splitting a single input light beam into a plurality of outgoing light beams, a transparent block has first and second planar surfaces substantially parallel to each other. Antireflection and reflection layers are laid on incident and reflection areas defined on the first planar surface while a plurality of partial semitransparent layers are attached to an outgoing area defined on the second planar surface. The incident light beam enters through the antireflection layer into the block and exits as the outgoing light beams through the partial semitransparent layers. At least one of the partial semitransparent layers has a width wide enough to at least two of the outgoing light beams. The partial semitransparent layers may be deposited on the first planar surface in the vicinity of the antireflection layer. In this event, the reflection layer is deposited on the second planar surface.

Miniature integrated optical beam-splitter in AlGaAs/GaAs ridge waveguides

Abstract: Typical directional couplers in semiconductor waveguides require long (several millimetre) interaction lengths, potentially limiting their use in future optoelectronic integrated circuits (OEICs). We report the fabrication and operation of a newly designed integratable waveguide beam-splitter device only micrometres in size, consisting of a groove at the intersection of two perpendicular AlGaAs/GaAs ridge waveguides which was milled with a microfocused gallium ion beam. Single-mode propagation of both transmitted and reflected beams was observed, and the power ratio between both beams was adjustable by varying the groove depth.

Measuring instrument for movement quantity

Abstract: PURPOSE: To reduce the size and cost of a measuring instrument by arranging a fixed diffraction grating in parallel to a moving diffraction grating and thus constituting a retroreflection optical system. CONSTITUTION: Light emitted by a light source 1 is transmitted through a beam splitter 2 and made incident on the moving diffraction grating 10. The light which is diffracted by an transmitted through the moving diffraction grating 10 travels to the fixed diffraction grating 20. The fixed diffraction grating 20 is arranged and fixed in parallel to the moving diffraction grating 10. The light diffracted by the fixed diffraction grating 20 returns to the diffraction position of the moving diffraction grating 10 and is diffracted again. The diffracted light travels through the same optical path with the incident light and returns to the beam splitter 2 and is polarized there and made incident on a photoelectric detector 3. Variation of the output electric signal of the photoelectric detector 3 is counted to determine the movement quantity of the moving diffraction grating 10. COPYRIGHT: (C)1988,JPO&Japio

Optical device for rotating the polarization of a light beam

Abstract: An optical device is disclosed for rotating the polarization of a light beam, in particular a laser beam. In one embodiment of the invention, the device comprises a prism which is adapted to rotate the polarization of a linearly-polarized beam of radiation by 90° and to change the direction of the beam. In a second embodiment, an optical device comprising a plurality of prismatic surfaces is adapted to receive a linearly-polarized input beam and to produce a linearly-polarized output beam which is collinear with the input beam and which is polarized orthogonally to the polarization of the input beam.

Straightness of travel interferometer

Abstract: An interferometer system capable of measuring accurately the deviations from straightness of travel comprises a source (10) of a frequency stabilized input beam (12) with two linear orthogonally polarized components which may or may not be of the same frequency; a tilted parallel plate or shear plate (16) with regions of reflection, antireflection, and polarizing coatings, for converting the input beam into two separated, parallel, orthogonally polarized beams (30, 31); a half-wave retardation plate (24), located in one of the separated beams (31), for converting the two separated, orthogonally polarized beams into first and second beams which are spatially separated, parallel, and have the same polarization (30, 33); a polarizing beamsplitter (40) and quarter-wave retardation plate (44) for transmitting the first and second beams (34, 35) to a prism assembly (45), attached to the mechanical apparatus whose straightness of travel is to be measured, for refracting the parallel first and second beams (36, 37) into diverging third and fourth beams (38, 39); a mirror assembly (70) with its surfaces (70 A, 70B) perpendicular to the third and fourth beams (38, 39) for producing converging fifth and sixth beams (38A, 39A) which are refracted by the prism assembly (45A, 45B) to produce parallel seventh and eighth beams (36A, 37A); the quarter-wave retardation plate (44), the polarizing beamsplitter (40), a split retroreflector (47) for producing parallel ninth and tenth beams which are converted into eleventh and twelfth diverging beams by the prism assembly (45); the mirror assembly (70) producing converging thirteenth and fourteenth beams which are refracted by the prism assembly (45) to produce parallel fifteenth and sixteenth beams which are transmitted by the quarter-wave retardation plate (44) and the polarizing beamsplitter (40); a beam switch (72), for transposing the fifteenth and sixteenth beams (60, 61) so that one (62) passes through the half-wave retardation plate (29) and both (62, 63) pass through the tilted parallel or shear plate (16) where the fifteenth and sixteenth beams (63, 64) are recombined into a single output beam (80) having two orthogonally polarized components in which the phase difference between the two components of the output beam (80) is related to the deviation from straightness of travel; a polarizer (81), for mixing the orthogonal components of the output beam (80); a photoelectric detector (83) for producing an electrical measurement signal (85); and a phase meter/accumulator (90), for indicating the measured phase, the measured phase being related to the deviation from straightness of travel.

Detection of squeezed states by cross correlation

Abstract: A new method for detecting a squeezed state by coincidence counting or cross correlation of the signals from two photodetectors is proposed. The two light beams falling on the two detectors are obtained from the two outputs of a homodyne beam splitter, whose inputs are the squeezed light and the local oscillator beam. With fast detectors the squeezing gives rise to excess photon coincidence counts. When a spectral analysis of the photoelectric currents is made, squeezing shows up as a positive cross correlation between the two signals, whereas unsqueezed light always produces negative correlations. Although the technique does not always cause the effects of local oscillator fluctuations to cancel out, as does the method of Yuen and Chan [Opt. Lett. B8R, 177 (1983)], they cancel in special cases, and the method has the advantage of being largely unaffected by detector after-pulsing. A simple combination of autocorrelation and cross-correlation measurements yields the degree of squeezing.

Length measuring instrument

Abstract: PURPOSE: To improve the reliability of a light source to wavelength variation and to improve the measurement accuracy by providing two gratings, i.e. fixed grating and moving grating, and refracting the (±1)th-order light of the fixed grating by the moving grating again and guiding the diffracted light to a photosensor. CONSTITUTION: Luminous flux which is emitted by the light source LD and made into parallel light by a collimator lens CL is split into two by a beam splitter HM1; and one is incident on an objective LN and the other is incident on a diffraction grating GS through a beam splitter HM2. The (±1)th-order light beams which are diffracted by the diffraction grating GS are incident on the diffraction grating GS again through phase difference plates EP1 and EP2 and corner cubes CC1 and CC2. The light which is diffracted by the diffraction grating GS again is incident on photodetectors PD1 and PD2 through the polarization beam splitter BS. Output pulses of the photodetectors PD1 and PD2 are counted to measure the relative movement quantity between a length measurement head MH and the diffraction grating GS. COPYRIGHT: (C)1988,JPO&Japio