Showing papers on "Beam splitter published in 1977"

Synchronizing signal generator

Abstract: In a device wherein a scanning beam from a light source is deflected by a light deflector, especially a rotatable polygonal mirror or a vibratory mirror and focused by an optical element such as a lens or the like to optically scan a surface to be scanned, thereby effecting writing and display of information, a synchronizing signal generator includes an optical system for taking out part of the scanning beam as a synchronizing beam for providing synchronism of signals in scanning In this device, a diffraction element such as a diffraction grating or the like serving as a beam splitter for splitting the deflected beam to obtain the synchronizing beam is disposed within the deviation range of the deflected beam, and the diffracted beam exiting from the diffraction element is directed to a photodetector so as to provide a synchronizing signal In this device, the use of the diffraction element as the beam splitter permits a wide area of the scanning beam to be split by a relatively thin member

Holographic memory with fringe stabilizing compensation for recording medium motion

Abstract: The holographic recording system comprises a pair of aligned first and second Fourier transforming lenses, a holographic beam splitter having a series of random phase illumination holograms at a front focal plane of the first lens and arranged to move in a given direction to successively receive a light beam for deffracting it into a zero-order diffracted beam and a first-order diffracted array of sampled, phase shifted beams, and a mask having a first and second apertures disposed at the Fourier transform plane of the first lens. A page composer having electrooptical transducers is positioned in the second aperture to receive the first-order diffracted array of beams to spatially optically modulate the incident beams in accordance with one of successive groups of binary signals. The zero-order diffracted beam is allowed to pass through the first aperture and the first-order diffracted array of spatially modulated beams are focused by the second lens to produce interference fringes between the wavefronts of zero- and first-order beams on a Fourier transform plane of the second lens on which a recording medium is positioned. The holographic beam splitter and the recording medium are conjugate to each other relative to the lens system and moved in opposite directions at equal speeds in synchronism with the occurrence of each group of binary signals, a series of two-dimensional holograms of the binary information is recorded.

Optical subtraction of images in real time

Abstract: There is disclosed a system capable of subtracting in real time the intensities of two incoherently illuminated scenes and providing the sign of the subtracted information. The system utilizes two birefringent devices such as liquid crystal light valves, onto which the two images to be subtracted are projected. One valve is analyzed in between crossed polarizers, or equivalent, while the other one is in between parallel polarizers or equivalent. Both polarizer arrangements, for example, may be implemented with a polarizing beam splitter and a quarter wave plate. The common output image plane, onto which both images are superposed, displays an intensity proportional to the difference between the two inputs. This intensity "rides" on a constant background intensity thus displaying the difference signal as well as its polarity. The read-in and read-out beams could be coherent as well as incoherent, the latter being more desirable due to its speckle-free image. No other system is presently known which can perform incoherent subtraction. Experimental results obtained with incoherent illumination are given.

Interferometric method and apparatus for sensing surface deformation of a workpiece subjected to acoustic energy

Abstract: 1488536 Measuring deflection by optical interference KRAUTKRAMER GmbH 24 Nov 1975 [4 Dec 1974] 48172/75 Heading G1A Apparatus for sensing the deflection of a workpiece surface 5 resulting from accoustic energy applied thereto comprises laser 1 whose beam 9 after reflection from surface 5 is split by beamsplitter 2 into portions 9a, 9b which positionally coincideon sensor 7, portion 9b being delayed due to the distance 11 Surface 5 is subjected to accoustic energy at 1 to 10 Hz The strength of the signal from photo-cell 7 depends on the phase difference of 9a to 9b, which varies according to the deflection of surface 9 during the delay time For the phase difference over the photo-cell of diameter d to be constant, the angle between portions 9a and 9b at the photo-cells <#/2/d For this the distance from surface 5 to splitter 2 is at least 5S for a diameter of 1 cm, or a telescope lens system with an aperture at the common focal point is interposed between 5 and 2 or mirror 10 and 2 The delay path may be folded by a pair of facing mirrors Length S may be modualted Piezoelectrically at a frequency f 1 higher than the accoustic frequency f 2 , so that the optimum path period occurs several times within the vibration period and the photo-cell output is at frequency f 1 modulated by f 2 The broken lines of Fig 6 show the light beam of a second interferometer used to maintain a constant length S If the distance of the delay path S via mirrors 2a, 18a, 18b and 2b alters, illumination at photo-cell 19 alters, giving a signal via amplifier 20 and filter 21 to Piezo-electric element 24a causing the motion of mirrors 24b to restore the illumination of photo-cell 19 Alternatively S may be kept constant by the Piezo-electric means moving mirror 18 relative to a fixed reference

Apparatus for reading a radiation-reflecting record carrier

Abstract: An apparatus is described for reading a record carrier with an optical information structure, in which apparatus errors in the focussing of a read beam on the information plane are detected with an astigmatic focussing-error detection system. By including a beam splitter in the path of a beam which has been reflected by the record carrier and by including an astigmatic focussing-error detection system in each of the paths of the two sub-beams thus obtained, the astigmatism of the one detection system being opposed to that of the other detection system, a focussing-error signal can be derived which is independent of optical faults in the read apparatus.

Three dimensional laser Doppler velocimeter

Abstract: A laser Doppler velocimeter which can measure fluid flow in three dimensions, employing a laser beam projected through a rotating diffraction grating and spaced lenses, with a beam splitter in the major optical path between two lenses ahead of the flow channel through which the fluid passes. Selected pairs of laser-derived beams are directed through the fluid and intersect at a predetermined point in the fluid. The movement of the particles through interference patterns formed by the intersecting laser-derived beams generates further-modulated scattered light, which is focused on a photomultiplier tube, from the output of which a fluid velocity directional component signal is derived for each pair. There are four laser-divided beams, and different pairs of these beams can be selected, to provide measurements from which the components of the fluid velocity along three mutually orthogonal directions can be derived.

Interferometric apparatus and process

Abstract: Disclosed is an interferometric apparatus and method for the inspection and detection of overlay errors characterized in that two plane polarized laser beams are directed onto the surface to be inspected, the angle included by these two beams being dimensioned in such a way that the radiation generating the plus or minus first order of the diffraction pattern of one beam is parallel to the other beam, thus generating an interference field which in the absence of overlay errors consists of an homogeneous fringe pattern while in the presence of such errors the fringe pattern is locally distorted. In a first embodiment, a first component of a laser beam is deflected onto a viewing screen by a beam splitter while a second component passes through the beam splitter to a mirror. The position and angle of the mirror is determined by the first order diffraction characteristics of the grating (object). The second component provides a first order of diffraction which interferes with the first component, producing an interference pattern on the viewing screen.

Dual beam fourier spectrometer

Abstract: A dual beam Fourier-type spectrometer is disclosed incorporating distinct sample and reference beams which enter the Michelson-type interferometer on the same side of the beam splitter and propagate at slightly different angles through the interferometer. The portions of both beams which emerge from the side of the beam splitter opposite the input side are directed to two separate optical detectors, the outputs of which are electronically subtracted. In a preferred embodiment, the interferometer is of the refractively scanned type, wherein the increased field-of-view facilitates the use of beams having different propagation angles.

On-axis film scanner with reflected illumination

Abstract: A scanner for reading binary digit spots on a transparent film includes a laser light beam which is directed through a beam splitter and through the film to a mirror, from which it is reflected back through the film to illuminate a small area on the film. Light which is not blocked by a recorded spot on the film continues back to the beam splitter, from which the beam is directed to a photodetector. The photodetector is positioned to receive light from solely a portion of the illuminated area of the film, to provide high definition scanning not adversely affected by distortion of the illuminating light beam by imperfections in the film and mirror.

Optical inspection system employing spherical mirror

Abstract: An optical system having a spherical mirror is used to collect light from the surface of a turbine blade or the like which is to be contoured. The spherical mirror is located at an equal optical distance from both the test specimen and the linear diode array so that it operates at a one-to-one magnification ratio. The linear diode array is positioned behind the spherical mirror and it receives light focused by the mirror and reflected by a beam splitter through an opening in the center of the mirror. None of the optical elements of the inspection system are located in the plane of movement of the test specimen so that even particularly long items such as a helicopter rotor blade can be contoured. Indentical upper and lower optical systems allows both surfaces of the test specimen to be contoured simultaneously and each system is independently operable and oriented to prevent optical interference. An automatic gain control is provided to adjust the optical modulator so that the effective intensity of the spot presented to the diode array is maintained within predetermined limits.

Laser gyroscope output optics structure

Abstract: A four frequency laser gyroscope system having a rugged and compact output structure for producing output signals representing the frequency differences between counter-circulating wave pairs circulating as two beams within the gyroscope cavity. A partially transmitting dielectric mirror forms both one of the cavity reflectors and the means for extracting a small portion of each beam. The two extracted beams are combined on a beam splitter. Both the transmitted and reflected beams from the output of the beam splitter, each containing waves of all four frequencies, are utilized. Each resultant beam is then polarization discriminated to extract the desired signal content. The entire structure is adapted for rigid mechanical coupling and may be constructed to have a small size.

Beam splitter coupled CDSE optical parametric oscillator

Abstract: An optical parametric oscillator is disclosed in which the resonant radiation is separated from the pump and output radiation so that it can be manipulated without interfering with them. Thus, for example, very narrow band output may readily be achieved by passing the resonant radiation through a line narrowing device which does not in itself interfere with either the pump radiation or the output radiation.

Photometric sphere for optical analysis and colorimetry - has fibre optic cables connecting sphere to measuring unit to give mobility

Abstract: Photometric sphere is esp. for reflection and transmission analysis and colorimetry of light-scattering objects in the visible and near-infrated ranges. The sphere (9) is connected by two flexible fibre optic cables (8a, b) to the rest of the measuring system to provide mobility. Light from a source (1) is focused by a reflector (2) and a condenser (3) onto a monochromator (4). The monochromatic light from the latter is divided by a beam splitter (5) into two partial beams which are introduced by a focusing unit (7a, b) into the fibre optic cables. The light in one cable is directed onto a sample (12a) and that in the other onto a control (13a) and the reflected light is sensed by a common photodetector (14a) and amplified by a preamplifier (15). Pref. the sample and control signals are subsequently separated by means of two lock-in amplifiers (16a, b).

Fiber‐optical interferometer

Abstract: A rectangular optical waveguide of homogeneous refractive index (dimensions 0.10×0.14×100 mm3) is designed to provide double self‐imaging of either end face upon the opposite one. We show how to use this guide as a fiber‐optical beamsplitter and, with the addition of a mirror, as a two‐beam interferometer. The operation of the interferometer demonstrates the mutual coherence of the split images. Applications are possible for in‐line fiber‐optical interferometric devices.

Practical Thin-film Polarizing Beam-splitters

Abstract: Polarizing beam-splitters of the cemented cube form are considered and the designs of a number of multilayer thin-film coatings of ZnS and cryolite giving polarizing efficiencies at the design wavelength of greater than 99·8 per cent are discussed. The refractive index of the cube is chosen to match that of the optical cement, so that wedge fringes due to the cement layer are eliminated.

Optical inspection system employing dual path pickup system with single spherical mirror

Abstract: An optical system having a single spherical mirror for collecting light from two directions combined by a beam splitter after the light has been scattered from the surface of a turbine blade or the like. The spherical mirror is located at an equal optical distance from both the surface of the test specimen and a linear detector array so that it operates at a one-to-one magnification ratio. The linear detector array receives light focused by the mirror along a path folded by the beam splitter. This arrangement is helpful in contouring the surface of a turbine blade near a vertical obstruction such as a shroud of a turbine blade since the collection axes of the pickup legs view the incident spot from different directions. None of the optical elements of the inspection system are located in the plane of movement of the test specimen so that even particularly long items such as a helicopter rotor blade can be contoured. Identical upper and lower optical systems allow both surfaces of the test specimen to be contoured simultaneously. An automatic gain control is provided to adjust the optical modulator so that the effective intensity of the beam incident on the detector array is maintained within predetermined limits.

Stabilizer for laser output

Abstract: PURPOSE:By selecting thickness of beam splitter, output of laser oscillator can highly be stabilized for a long period.

Method and apparatus for fabricating optical waveguide grating resonators

Abstract: A helium cadmium laser generates an output beam of radiation which is coupled through a spatial filter and beam expander to a beam splitter which in turn provides two enlarged beams of coherent radiation of approximately equal power. Two highly reflective mirrors are used to direct the two beams such that the two beams interfere and create the usual interference pattern in a positive photoresist layer covering an optical substrate. A thin sheet of high index glass is held by two blocks of quartz in a position adjacent to the photoresist layer and oriented such that a part of each beam of coherent radiation is caused to pass through the high index glass before interfering with the other beam on the photoresist layer. As a result, a grating having a quarter wavelength step or discontinuity in the middle of the grating is fabricated in the photoresist. The photoresist pattern is then transferred to the optical waveguide by ion-beam milling. Several high index sheets can be positioned so as to create more than a single quarter wavelength step.

Self-supporting thin-film beam splitter for far-infrared interferometers

Abstract: Commercially available plastic films have been examined, in the spectral range up to 1200 cm−1, for use as a beam splitter in far-infrared Michelson interferometers. The materials reported include polyethylene terephthalate, polycarbonate, polyvinylchloride, polypropylene, cellulose and polyethylene.

Interference optical sensing device for a centrifuge

Abstract: The specification describes an interference optical measuring or sensing device, comprising a light source, a beam splitter, two component light paths and a radiation sensor for a multiple hole centrifuge rotor. When the rotor is in motion sample cells and the counter-weight move successively through the component light paths and at a particular position have both light paths extending through them. There is furthermore an arrangement for producing a position signal indicating that a selected hole is in a certain position in which it has both component light paths extending through it. A control arrangement ensures that the measuring device is activated briefly in the predetermined position of the selected hole. The light source continuously supplies light between the periods of activation of the measuring device. The component beam paths are respectively coupled with a control light sensor at positions, which in terms of the direction of light from the light source lie behind the multiple hole rotor and the control light sensor produces a component beam output signal when the respective component beam path is completed by a hole in the rotor. The position signal and the two component beam path signals are supplied to a coincidence circuit, which activates the measuring or sensing device on the simultaneous arrival of all three signals.

Semiconductor laser light source unit

Abstract: PURPOSE: to perform powerful light synthesis by providing focal anamorphic optical systems between lasers and a splitter at the time of letting the light emitting faces of a plurality of semiconductor lasers optically intersect perpendicularly, disposing a polarizing beam splitter at the point of their interections and superposing the plural luminous fluxes. CONSTITUTION: The beams from mutually perpendicularly intersecting semiconductor laser 4, 5 are collimated with colimator lenses 6, 7 and the widths in one direction of the beams are expaneded by anamorphic aocal converters 8, 9 composed of cylindrical beam expanders 8, 9. Next, the beams ar entered to a polarizing beam splitter 10, by which the beam of the laser 5 is perfectly transmitted and the beam of the laser 4 is reflected, whereby the combined light beam A is provided. Thereafter the beam A is deflected with a deflector 11, and is imaged on a recording face 13 by an imaging lens 12. In this way, the light spot is converged, and the resolving power to the recofring face 13 is enhanced COPYRIGHT: (C)1979,JPO&Japio

Device for automatically focusing image

Abstract: Behind an objective which is axially movable, is provided a beam splitter to divide the light path passing through the objective into two light paths. In one of the light paths on the image plane of the objective is located a prism. Behind the prism is provided a photodetector in the optical path includng the prism. In the optical path which does not have the prism also is provided a photodetector at a position which is optically conjugate with the other photodetector. The output of the photodetectors are connected to an output comparing circuit which is connected to a servomotor for controlling the position of the objective. When the outputs of the two photodetectors are equal to each other, the servomotor is stopped.

High-Speed Holocinematography Of Cavitation Bubbles

Abstract: Two methods of high speed holocinematography are described using spatial or_spatial fre-quency multiplexing for image separation. The experimental devices operate in the range oflo 000 to 20 00o holograms per second with a total number of holographic frames of four toeight. Spatial multiplexing is achieved by a rotating disk with apertures placed directly infront of the holographic plate. Spatial frequency multiplexing is obtained with the aid ofa special acousto -optic beam splitter and deflector unit. Objects investigated by both meth-ods are bubbles moving in acoustically generated cavitation bubble fields as well as bubblesformed after laser- induced breakdown in water.IntroductionFast moving objects like bullets or cavitation bubbles are usually studied by means ofhigh speed cinematography(1,2). Several devices like rotating drum, rotating mirror or imageconverter cameras are commercially available for this purpose. An essential drawback of allphotographic methods lies in their limited depth of focus. This becomes quite obvious whenmany tiny objects distributed in a large volume are to be recorded.A method to overcome the problems connected with the limited depth of field is hologra-phy. Whereas holography with continuous wave lasers is a familiar technique used in manylaboratories, pulsed -laser holography and especially multiple pulsed -laser holography as re-quired for high speed holocinematography is still a field of research. Until now a real ho-lographic equivalent to the rotating drum or rotating mirror camera has not yet been deve-loped because of the great technical difficulties involved.The present paper, as others in this field(3,4), is a step towards this final aim. Twoholographic recording techniques and experimental devices are described capable to take se-quences of four to eight holograms with a hologram framing rate of lo to 2o kHz. The deviceshave been developed in connection with problems in cavitation physics where the knowledgeof the dynamics of bubble fields in three dimensioiis is of considerable interest.The performance of both experimental arrangements is demonstrated by reconstructions ofhologram sequences taken of laser -generated and acoustically generated bubbles.General ConsiderationsIn holocinematography several holograms are taken successively in short time intervals.To expose the holographic plate a series of intense coherent light pulses is required, usu-ally delivered by a multiply Q- switched solid state laser. If high framing rates of say 10to 20 kHz are needed it is almost impossible to change or even move the holographic platebetween successive exposures because the interference pattern would be blurred. Thus theinformation from all single exposures has to be stored on the same plate. There are two dif-ferent methods of multiplexing which provide separation of reconstructed images. Each singlehologram can either be recorded on different portions of the holographic plate (spatial mul-tiplexing) or on the whole plate but with different directions of the reference beam (spa-tial frequency multiplexing). The speed with which the area of exposure (one holographicframe) can be changed on the plate or the reference beam can be switched into a new direc-tion limits the framing rate of the actual device.Multiplexing by spatial division is very simple. A common holographic set -up can be used,where object and reference beam cover the whole holographic plate. Different areas of theplate are exposed by placing a rotating disk with apertures directly in front of it. Whenthe speed of revolution of the disk is properly chosen each light pulse of the series illu-minates a separate portion of the holographic plate. If a sequence of n holograms is to betaken, the fraction 1/n of the whole area of the plate is available for each pulse. In this

Interferometric optical phase discrimination apparatus

Abstract: Film of a known refractive index whose thickness is to be measured is illuminated by a white light beam. Two wave fronts from both sides of the film are directed to an interferometer. The wave fronts are out of phase in accordance with the thickness of the film. The two wave fronts are amplitude-split, respectively, by the beam splitter of the interferometer. Two of the split wave fronts are tilted by tilting means in the interferometer. The other two split wave fronts, as well as the two tilted wave fronts, are directed to an interference surface. Thus, there is formed a white interference pattern on the interference surface. The white interference pattern has a middle peak and two side peaks. The space interval between these peaks is measured by a scanner. By knowing the peak-to-peak interval, it is possible to discriminate the space interval between both sides of the film.

Appts. altering refractive index of interferometer arm - has second or comparison beam passed to reference mirror while first beam returns to splitter

Abstract: The optical length of path of an interferometer arm is changed in interference measurements of relatively short lengths or length changes, by changing the refractive index of the light guiding medium. The refractive index is changed by changing the pressure of this medium. The path of light to be regulated in a recipient is transferred and the internal pressure is changed. Monochromatic light (1) is divided by the beam splitter (2). The first or measuring beam (3) is passed to a mirror (5) and returned to the beam splitter (2). The second or comparison beam (4) is passed to a reference mirror (6) and returned.

Optical video playback apparatus with tracking control and tbc

Abstract: In apparatus for optically reproducing information signals from a record carrier, such as a video disc, and in which a light beam from a source, such as a laser is incident through an objective lens onto the surface of the record carrier and a tracking servo control is provided for adjusting the position of the incident light beam on the record carrier; a time base correction mirror operates on the light beams both incident onto, and reflected from the record carrier, and a tracking servo mirror operates only on the light beam incident onto the record carrier. A beam splitter and quarter wave plate are preferably positioned in the optical path between the tracking control mirror and the time base correction mirror. The apparatus may also include a lens with opposed spherical and cylindrical surfaces in the path of the reflected beam between the objective lens and a signal detection photodiode.

Apparatus for laser anemometry

Abstract: Apparatus for laser anemometry comprises a device for producing coherent radiation, a beam splitter device adapted to divide the beam from this device into two beam portions, focussing means adapted to focus these two beam portions on to two adjacent spots, and two photodetector means each adapted to measure the scattered illumination from one said spot. In order to enable the direction of the path between the two spots to be altered without moving the entire apparatus, an image rotation device is provided and mounted to effect both the beam portions and the scattered radiation from the spots which falls on the photo-detector means.

Thin-film beam splitter for integrated optics

Abstract: A simple thin-film beam splitter has been made by sputtering techniques. The device is similar in principle to beam splitters in bulk optics based on frustrated total reflection. It depends on a slow variation of guide thickness that permits the existence of an evanescent wave by which light is transferred from one side of the beam splitter to the other. The tunneling region has a variable index profile and there are no discontinuities. Fabrication techniques, theory, and experimental results are presented.

A Spectrum Scanning Stokes Polarimeter

Abstract: A photoelectric polarimeter for measuring solar spectral line profiles in all four Stokes parameters has been built and operates on a 40 cm coronagraph in a joint project with Sacramento Peak Observatory. A description of the optical and electronic systems and the calibration scheme is presented. Performance parameters determined from observations are also given. The polarimeter package consisting of a pair of KDP's, a quarter wave plate, and a polarizing beam splitter is located at the prime focus of the coronograph. Modulation of the KDP's encodes polarization information into intensity signals that are electronically detected. The scanning of the spectrum, accomplished by rotating the grating, permits Stokes line profiles to be recorded on magnetic tape for processing. The instrument can be used to scan any line from 3900 to 7000A with a spectral resolution of .01A. Polarizations as small as .001 percent are detectable. The polarimeter and observing system are computer controlled.