Showing papers on "Beam splitter published in 1988"

New type of Einstein-Podolsky-Rosen-Bohm experiment using pairs of light quanta produced by optical parametric down conversion.

Abstract: A pair of correlated light quanta of 532-nm wavelength with the same linear polarization but divergent directions of propagation was produced by nonlinear optical parametric down conversion. Each light quantum was converted to a definite polarization eigenstate and was reflected by a turning mirror to superpose with the other at a beam splitter. For coincident detection at separated detectors, polarization correlations of the Einstein-Podolsky-Rosen-Bohm type were observed. We also observed a violation of Bell's inequality by 3 standard deviations.

Optical space switch

Abstract: A bidirectional optical space switch for selectively coupling an input signal to a selected output comprises two arrays of inputs (1, 8), two arrays of outputs (5, 9), polarising beam splitters (2, 4), and a matrix of cells (3) each of which is selectively capable of varying the polarisation state of light passing through it in response to an applied control signal. A first optical system (6) couples each of inputs (1) and a corresponding one of outputs (9) with a corresponding column of cells while a second optical system (7) couples each of inputs (8) and a corresponding one of outputs (5) with a corresponding row of cells. One of inputs (1) is switched to one of outputs (5) by activating the appropriate cell so that it rotates the polarisation of light passing through it by 90°. This also couples one of inputs 8 to one of outputs (9) thereby providing bidirectional switching. Use of combined beam splitters and polarisers (2, 4) provides bidirectionalily at substantially no loss of light additional to that lost on discrimination of the polarisation states.

Optical interconnection network using polarization-based ferroelectric liquid crystal gates

Abstract: A polarization-based 4 x 4 optical interconnection network using surface stabilized ferroelectric liquid crystal (SSFLC) gates is demonstrated. The SSFLC gates are comprised of an SSFLC device sandwiched between two polarizing beam splitters. Optical crosstalk using these fast switching programmable devices can be limited to ~-20 dB/gate, which would allow 2-D interconnection networks to be fabricated with thirty-one input channels and 3-D interconnection networks with approximately 225 input channels.

3-dimensional vision system utilizing coherent optical detection

Abstract: A three-dimensional optical scanning vision system capable of producing high-resolution images in real-time includes an optical source for producing a source light beam. The source light beam is directed to a beam splitter which splits it into a local oscillator beam and a signal beam. The local oscillator beam is directed toward a photodetector, while the signal light beam is directed toward a target. Light reflected from the target is received by the beam splitter and directed toward a retroreflector which returns the beam to the beam splitter interface. Quarter wave plates and the retroreflector insure that the return light beam and the local oscillator beam are collimated and have the same polarization state. Mixing of the local oscillator beam and the return light beam occurs at the beam splitter interface, thus providing coherent optical detection by the photodetector. The photodetector thus provides an output signal providing a high degree of information about the target. The system also includes scanner optics to scan the signal light beam across the target. A processor is also included for outputting a three-dimensional image of the target, and for controlling the scanner optics.

Tapered-fiber interferometric wavelength response: the achromatic fringe.

Abstract: In considering the wavelength-dependent transmission of tapered fibers we provide an observation of the fringe that shows the least response to variations in wavelength and that is, by definition, the achromatic fringe. This is a manifestation of the equalization of the HE11–HE12 group velocity occurring at V = 4.4. The fact that it was observed in a tapered single-mode fiber confers some particular features that are discussed and compared with those of other two-mode guides with regard to sensor applications.

Laser drilling of components

Abstract: A method and apparatus for drilling holes through a component (16) from a first surface to a second surface The method includes the step of applying a thixotropic water soluble medium to the second surface The medium contains material to disperse the laser light and light emitting material (which could be fluorescent, phosphorescent or luminescent) Monitoring means and beam splitter are provided for monitoring light emitted, or reflected, by the component 16, along the length of the hole drilled by the laser and for monitoring light emitted by the medium In this way one can detect when the laser breaks through the second surface and also produce an image indicative of the size and shape of the hole

Linear and angular displacement measuring interferometer

Abstract: A single interferomter system capable of measuring accurately linear displacement and angular displacement simultaneously of a movable plane mirror (90) comprises a source (10) of a frequency stabilized input beam (12), a polarization beamsplitter (80), two quarter-wave plates (88, 108), a mirror (89), and a retroreflector (81), to reflect one polarization component of the input beam (12) twice from the movable mirror (90) to produce a first output beam and to reflect the other polarization component of the input beam (12) twice from the stationary mirror (89) to produce a second output beam. The beamsplitter (80) recombines the output beams into a third output beam having two orthogonally polarized components related to the linear displacement of the movable mirror (90) at the first position. The third output beam is divided into a fourth output beam and a fifth beam parallel to, spatially displaced from, and traveling in the same direction as the input beam (12) and has its polarization components rotated by 90 degrees from the third output beam. The interference between the components of the fourth beam is detected by photodetector (94) and the phase change is extracted from the resultant signal (96, 99) with the measured phase being related to the linear displacement of the mirror (90) at the first position. A second photoelectric detector (194) produces a signal from which the phase change is extracted from the resultant signal (97, 109) with the second measured phase related to the angular displacement of the movable plane mirror (90).

Laser catheter feedback system

Abstract: A control system for a laser catheter device wherein the control system is provided with means for determining the intensity of laser beam energy at two points, one of which is at the distal tip end thereof, and with the other being interposed along a transmitting column remote from both the source of laser beam energy and the distal tip. A beam splitter means(dichroic filter) is provided for diverting a first portion of the laser beam energy onto a first detector means. Energy passing through the beam splitter is ultimately directed onto a fluorescent member or device disposed adjacent the distal tip, with the fluorescent member or means being capable of emitting or generating radiant energy at a wavelength significantly different from that of the incident laser beam energy. The radiant energy generated by the fluorescent means is directed onto a second surface of the beam splitter means, and ultimately onto a second detector means. First and second signal processing means responsive to the first and second detector means are utilized to control a shutter, such as a dual shutter, which is arranged to interrupt the passage of laser beam energy through the catheter system upon the occurrence of anomalous levels of laser beam energy at either the first or second detector means.

Method and apparatus to determine the size and velocity of particles using light scatter detection from confocal beams

Abstract: An apparatus for sizing particles, droplets, bubbles, or the like employing laser light scattering is disclosed. A laser is used for generating two beams of light having different wavelengths or polarizations. The beams with different wavelengths may be generated by an argon ion laser or by two different lasers (e.g., Helium Neon and Helium Cadmium). Two beams with orthogonal polarizations may be produced by partitioning a single linearly polarized beam and rotating the polarization of one by 90°. One of the beams is then expanded using a conventional beam expander and then redirected to be coaxial with the first beam. The beams are then focused to a common focal region. One beam is from two to four times larger in diameter than the other. An optical collection apparatus for sensing the light scattered caused by the particles, droplets, bubbles or the like passing through the focused beams has an axis extending into the focused beams. The axis of the collection apparatus may be aligned with the transmitted beams in the forward or backward direction (on-axis detection) or at some suitable angle to the beams (off-axis detection). The collection apparatus includes receiver lenses which focuses the scattered light through the beam splitter onto a first photo-detector, and light reflected from the beam splitter is directed onto a second photo-detector. The photo-detectors sense the scattered light from the beams with separate wavelengths or polarizations and produce proportionate voltage amplitudes. The peak voltages are determined from the information sensed by the light collection apparatus. A mathematical formulation is used with the known beam diameters and intensities along with the two measured signal voltage amplitudes to determine the particle trajectory through the beams and hence, particle size. The technique also allows for the determination of the sample volume cross-section and particle speed, thus allowing the determination of particle number density and volume flux.

Linear and angular displacement measuring interferometer

Abstract: An interferometer system capable of measuring linear displacement and angular displacement simultaneously of a movable plane mirror (90) comprises a source (10) of a frequency stabilized input beam (12) and includes an optical system which reflects one polarization component of the input beam (12) twice from a first position on the movable plane mirror (90) to produce beams (30) and reflects the other polarization component of the input beam twice from a stationary plane mirror (89) to produce beam (28). A polarization beamsplitter (80) recombines these beams (30, 28) into a beam (66) in which the phase difference between the two components of the third output beam (66) is related to four times the linear displacement of the movable plane mirror (90) at the first position. Beam (66) is divided into beams (119) and (121), with the interference between the two polarization components detected by photodetector (94) to produce a signal (96) from which the phase change is extracted (99) to produce a measured phase which is related to four times the linear displacement of the movable plane mirror (90) at the first position. The polarization beamsplitter (80) and a retroreflector (81) reflect one polarization component of the other beam (121) twice from a second position on the movable plane mirror (90) and reflect the other polarization component of this beam (121) twice from the stationary plane mirror (89) with the beamsplitter (80) recombining the resultant beams into a beam (67) having two orthogonally polarized components in which the phase difference between the two components of the beam is related to four times the sum of the linear displacements of the movable plane mirror (90) at the first and second positions. The interference between the two components of beam (67) is detected by second photo detector (194) to produce a signal (97) for indicating a second measured phase, which is related to four times the sum of the linear displacement of the movable plane mirror (90) at the first and second positions. Electronic module (124) provides the difference between one-half of the second measured phase (101) and the first measured phase (100) to produce a signal (126) related to angular displacement (91) of the movable plane mirror (90).

Method and apparatus for measuring blood oxygen levels in selected areas of the eye fundus

Abstract: This invention provides for the measurement of relative oxygen saturation of the choriodal blood of the fundus of the eye of a subject by directing into the eye a source beam of light including incandescent, red and infrared light, the combined beam penetrating the choroid and impinging on the sclera of the eye, the beam then being reflected back out of the eye as a collimated beam of light. The collimated beam of light is directed to a dichroic beam splitter where the red and infrared light are separated from the beam and are subject to the measurement of their respective intensities. The measured intensities of the red and infrared light components of the collimated beam reflected from the eye are compared with the measured intensities of the red and infrared light components of the separated portion of the source beam of light to determine the ratio of oxyhemoglobin to reduced hemoglobin.

Method and apparatus for two-wavelength interferometry with optical heterodyne processes and use for position or range finding

Abstract: An apparatus for measuring changes in a variable interference section of an interferometer comprises a laser source for producing beams of the frequency n 1 and the frequency n 2 , polarizing beam splitters for producing cross-polarized partial beams of frequency n 1 or n 2 , modulators for displacing the frequency of one of the partial beams by frequency f 1 or f 2 , a pair of deflecting mirrors in each case and polarizing beam splitters for combining the partial beam n 1 , n 1 +f 1 , n 2 , n 2 +f 2 . The apparatus further includes two photodetectors, upstream of which are arranged a polarizer, a Michelson interferometer, a non-polarizing beam splitter for splitting the partial beams in each case into a measuring light beam or a reference light beam. The reference light beam passes to an associated photodetector. The measuring light beam passes into the Michelson interferometer and then to the associated photodetector. The signals of the photodetectors are demodulated according to the amplitude and the phase difference between the two demodulated signals is determined. This phase difference is only dependent on the position of a measurement object and the equivalent wavelength of the difference n 1 -n 2 . A method for measuring changes by determining positions or distances is performed by the apparatus.

Interferometric surface profiler for spherical surfaces

Abstract: An interferometric profiler for measuring the topography of a spherical test surface (48), comprises a linearly polarized light source (10), a rotating diffuser disc (18, 20); an optical system (26, 30, 31) for collecting and directing light from the extended light source; a first quarter-wave phase retardation plate (38); a lens (34) for focusing the resultant circularly polarized light beam onto a spherical test surface (48and a spherical reference surface (45), the surface (45) having a reflective coating (46) and an anti-reflection coating; a piezoelectric transducer (80) for varying the relative distance between the spherical test surface (48) and the spherical reference surface (45); means for recombining the test and reference wavefronts (53T,53R) to produce an interference pattern (74); a lens (65) for imaging the spherical test surface (48) and the spherical reference surface (45) onto the photosensitive elements (58) of an imaging device (56); means for optically isolating the imaged spherical test surface (48) and the spherical reference surface (45) and the interference pattern (74); means (38) for converting the test wavefront (53T) and reference wavefront (53R) into a third linearly polarized light beam which has its polarization vector rotated 90 degrees relative to the first linearly polarized light beam; the polarizing beamsplitter (30, 31) directing the third linearly polarized light beam to the imaging device (56); the imaging device (56) sensing the interference pattern (74), a CCTV monitor (72) for viewing the imaged spherical test surface (48) and the spherical reference surface (45) and the interference pattern (74); and means (76) for processing the output of the imaging device (56) to profile the topography of the test surface (48).

Influence of a beam splitter on photon statistics.

Abstract: The quantum analysis of the influence of a beam splitter on photodetection statistics is discussed. The link between second-order correlation functions and various experimental quantities obtained in photon counting and spectrum analysis is clarified. The introduction of a ``vacuum field'' is interpreted as a mathematical transformation between two sets of creation-annihilation operators, which can be used as a mathematical device for simplifying the calculations. However, its physical interpretation as a real field is shown to be potentially confusing. The present theoretical approach is used in the interpretation and the analysis of heterodyning experiments of a squeezed signal with a much stronger local oscillator in a coherent state.

Optical switch having birefringent element

Abstract: An electrically controlled optical switch employs an electro-optical crystal of the kind exhibiting birefringence in each of two different light paths when the crystal is disposed in orthogonally oriented electric fields, with each light path being sensitive to a different one of the two electric fields and each path having its own set of fast and slow axes. A crystal of bismuth germanium oxide has those properties. Electrodes are provided for separately establishing each of the two electric fields and control circuitry allows only one field at a time to be established. Polarizers are situated at opposite ends of the electro-optical crystal in alignment with each of the two paths. Adjacent one end of the crystal are disposed a beam splitter and a right angle prism. The prism is arranged to receive some of the light entering the beam splitter and reflect that light along one of the paths of the crystal while another portion of the entering light proceeds through the beam splitter into the other path of the crystal. The polarizers block the light in one path while enabling light to emerge from the other path.

Normal incidence optical switches using ferroelectric liquid crystals

Abstract: This invention comprises a new group of fiber optic switching devices that use layers of surface-established ferroelectric liquid crystals (FLCs) as the switching media. In each of the devices light impinges upon the ferroelectric liquid crystal at an angle of 90° (normal incidence) with the surface plane. Each FLC gives 0° or π° optical rotation, depending upon the polarity of the electric voltage applied. A series of polarizing beam splitters are used to separate unpolarized light into its s and p polarization components. After ferroelectric liquid crystal switching, other polarizing beam splitters are used to direct the s and p light to output optical paths. The switches discussed below are voltage controlled 2×2, 1×4, 1×6, 1×8, 4×4, or N×N devices that use one or more layers of surface stabilized ferroelectric liquid crystals.

Surface profiling interferometer

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) mirrors. 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 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.

Polarization selective holographic optical element

Abstract: A polarization-selective holographic element having first and second holographic layers, each holographic layer including holograms comprising a plurality of fringes. The holographic optical element transmits a first component of light without diffraction and diffracts a second component of the light by a selected angle. The holographic optical element diffracts the second component into only one beam. The holographic optical element can be utilized as a beam splitter which is provided with optical power, for use in an optical head, by storing holograms for cylindrical and other powers and for auto-focusing and tracking capabilities.

Programmable detector configuration for Fraunhofer diffraction particle sizing instruments

Abstract: An intelligent laser diffraction particle sizing system is disclosed. A portion of the primary laser beam is directed by beam splitter into a calibration leg, modulated, and passed through a diffraction reticle. The known diffraction signature of the reticle is then recombined with the primary beam to pass through the particle field. Both the modulated calibration diffraction signature and the portion of the primary beam scattered by the particles are collected by the transform lens and detected at the back focal plane using an X-Y photodiode array. The detector array elements are grouped into variable geometry annular rings. The ring detectors are continuously centered around the beam using feedback from the X-Y position detector which monitors beam deflection.

Embedded fiber optic beam displacement sensor

Abstract: A method and apparatus for the two dimensional measurement of displacements of sample materials using a photodetector grid array and optical fiber embedded in the test specimen The system consists of a light source which is passed into one end of an optical fiber which has been embedded a beam specimen, so that when the beam is placed in motion, the light traverses through the fiber and emerges from the opposite end where its projected image traces a pattern simulating that of the beam In a preferred embodiment, the collimated exiting light is incident upon a light beam splitter which directs equal portions of the light toward a quadrant photovoltaic cell device and toward a charge couple device (CCD) The CCD is connected to an optoelectronic viewing device for initial calibration, display and monitoring The photodetector array is connected to a translator/amplifier which increases the photocells' source currents and converts them to equivalent voltages for output to a digital data processing terminal The processing terminal integrates all simultaneous measurements by vectorial resolution of the voltage related deflections' magnitude and direction

Electron holography apparatus

Abstract: An electron holography apparatus includes an electron microscope which is provided with an electron source, a beam splitter for dividing an electron beam emitted from the electron source into first and second electron beams, and a phase controller for controllably changing a phase difference between the first and second electron beams, and further includes an image detector for detecting an electron interference fringe pattern which varies in accordance with the phase difference between the first and second electron beams, as a picture image, and an image data processor for determining the phase distribution of one of the first and second electron beams from detected image data.

Phase sensitive optical monitor for thin film deposition

Abstract: The thickness of growing thin film layer is monitored by directing a beam of circularly polarized monochromatic monitoring light into the layer and detecting the portion of the monitoring light reflected from the layer. The difference in phase between the s and p polarized components of the reflected light is measured and those thicknesses of the layer at which the difference in phase between the s and p components is zero are related to thicknesses which are an integral multiple of one fourth of the wavelength of the monitoring light in the layer. An apparatus for monitoring the thickness of a growing layer during the fabrication of an optical thin film includes a source of light for directing a beam of light at the growing layer and a polarizer between the source and the layer for converting the light beam to a linearly polarized beam. A quarterwave plate between the polarizer and the layer converts the linearly polarized beam to a circularly polarized beam, while a polarizing beam splitter receives the portion of the beam reflected from the layer and divides the portion into a +45° polarized component and a -45° polarized component. A first detector detects the intensity of the +45° polarized component and a second detector detects the intensity of the -45° polarized component.

Optical correlator system

Abstract: An optical correlator system, comprising a laser to generate a signal beam, an image means located in the path of the signal beam to spatially modulate the signal beam, and first and second matched filters. A multiple beam generating holographic lens is located in the path of the modulated signal beam to partially transmit the signal beam and to deflect a first matrix of replicas of the signal beam onto the first matched filter. A mirror is located in the path of the partially transmitted signal beam to reflect that transmitted beam back to the holographic lens, which deflects a second matrix of replicas of the signal beam onto the second matched filter. With an alternate embodiment, a series of holographic lenses and beam splitters are alternatively arranged along the path of the signal beam. Each holographic lens generates two matrices of beams, with each matrix of beams being focused on an associated matched filter. Each beam splitter partially reflects the signal beam back to the preceding holographic lens, and partially transmits the signal beam to the following holographic lens.

Frequency doubled, cavity dumped feedback laser

Abstract: Higher efficiency in cavity dumping and frequency doubling in a laser used to produce modulated output beam pulses is achieved by deflecting light out of the resonant cavity to a third mirror through a frequency doubler using an electro-optic modulator and a polarizing beamsplitter in the resonant cavity, or using just an acousto-optic modulator to deflect light out of the laser cavity in response to a control signal (electric or acoustic). The frequency doubler in front of the third mirror rotates the frequency doubled light so that it will pass out of the laser cavity through the polarizing beamsplitter, while undoubled frequency light is reflected by the polarizing beamsplitter back into the gain medium of the laser. In the case of using a type-II frequency doubler, a dichroic beamsplitter deflects out the frequency doubled light and passes the undoubled frequency light to the polarizing beamsplitter for return to the laser gain medium. If an acousto-optic modulator is used, it deflects light out of the primary laser cavity, so a polarizing beamsplitter is not needed, and only a dichroic beamsplitter is needed to separate frequency doubled light out of the path from the third mirror.

Switched holograms for reconfigurable optical interconnection: demonstration of a prototype device.

Abstract: We report the construction of a device intended for programmable optical interconnection of multiple processors in a highly parallel computer. This device, the Holoswitch, is based on an array of optical switches (liquid crystal polarization switches and polarizing beam splitters), which direct a set of optical beams toward any of a selection of holograms. Each hologram, when selected, deflects the input beams toward an output array with any desired prerecorded permutation. The prototype device has nine different interconnection patterns recorded on a single 10- × 12.7-cm DCG hologram. We have recorded permutation patterns with up to 64 optical channels in an area of 4 cm2.

Thin film beamsplitter optical element for use in an image-forming lens system

Abstract: A beamsplitter optical element, including a triangular substrate, such as a prism, having a plane face corresponding to the hypotenuse of the prism which is coated with a thin film structure having materials and thicknesses, which effect a division of each light beam such as into a reflected and a transmitted portion, in such a way that the beams suffer no net aberration as a result of multiple reflections within the thin film structure, and a second triangular substrate, such as a prism having a plane face, corresponding to the hypotenuse, optically bonded to the thin film structure deposited on the hypotenuse of the first prism.

Patterned wafer inspection using laser holography and spatial frequency filtering

Abstract: An automatic patterned wafer inspection system for use in integrated circuit fabrication is described. The system is based on the techniques of optical spatial frequency filtering and laser holography. The system can locate defects as small as 0.5 μm over a 150 mm patterned silicon wafer in ∼30 min. The wafer under inspection is placed in front of a lens and is flood illuminated through beam splitting optics with a collimated laser beam. The light reflected and diffracted from the wafer is collected by the lens through the beam splitter. In the back focal plane of the lens, the Fourier transform (spatial frequency) pattern of the wafer circuit is formed. A spatial filter placed in this plane effectively blocks the transmission of the light from the repetitive circuit features of all dies of the wafer. The wave front transmitted through the filter is then recorded in a hologram. The conjugate to the recorded wave front is later reconstructed from the hologram. The reconstructed wave front thus reverse ray ...

Bidirectional optical space switch

Abstract: A bidirectional optical space switch for selectively coupling an input signal to a selected output comprises two arrays of inputs (1, 8), two arrays of outputs (5, 9), polarizing beam splitters (2, 4), and a matrix of cells (3) each of which is selectively capable of varying the polarization state of light passing through it in response to an applied control signal. A first optical system (6) couples each of inputs (1) and a corresponding one of outputs (9) with a corresponding column of cells while a second optical system (7) couples each of inputs (8) and a corresponding one of outputs (5) with a corresponding row of cells. One of inputs (1) is switched to one of outputs (5) by activating the appropriate cell so that it rotates the polarization of light passing through it by 90°. This also couples one of inputs (8) to one of outputs (9) thereby providing bidirectional switching. Use of combined beam splitters and polarizers (2, 4) provides bidirectionally at substantially no loss of light additional to that lost on discrimination of the polarization states.

Optical apparatus for use with inteferometric measuring devices

Abstract: A laser inteferometer system is disclosed which is able to make measurements of any deviations in the movement of a machine component which is moving along a main movement axis. The system can measure roll, pitch, yaw, straightness, and parallelism of two tracks using a single laser beam. FIG. 1 shows an arrangement for measuring roll of a vertical machine column (2) during movement of the column along the x-axis of a machine. A straight mirror (6) is positioned on the machine bed with its longitudinal axis aligned with the x-axis, and its reflecting surface normal to the x-axis. An optical component including a polarizing beam splitter is mounted for movement with the machine column and generates from a laser beam (A), a measuring beam (B1) and a reference beam (B2) both directed at the mirror, but laterally separated in the direction of the Z axis. The reflected beams from the mirror are re-combined in the optical device to form a return beam (C) directed towwards a detector adjacent the laser (9). Any change in relative length of the beams (B1) and (B2) give a meausre of roll. Yaw can be measured by producing beams (B1) and (B2) laterally separated in the direction of movement, i.e. along the x-axis. Straightness is measure using a fixed length reference arm within the optical device. Parallelism is meausured by taking straightness measurements of both pillars (2) and (2a). Pitch can be measured by producing four beams.