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Showing papers on "Beam splitter published in 1989"


Journal ArticleDOI
TL;DR: It is shown that homodyning quantum fluctuations can be reduced by using a balanced photomixer for arbitrary input states.
Abstract: For optical homodyning, the matrix representation of a lossless beam splitter belongs to the SU(2) group of unimodular second-order unitary matrices. The connection between this group and the rotation group in three dimensions permits the field density operators at the input and output ports of the beam splitter to be related by means of well-known angular-momentum transformations. This, in turn, provides the joint output photon-number distribution, which may be written as a Fourier series in the relative phase shift imparted by the beam splitter, for a general joint state at its inputs. The series collapses to a single term if one of the input fields is diagonal in the number-state representation. If the inputs to both ports are further restricted to be pure number states, the joint, as well as the marginal photon-number distributions, turn out to be directly proportional to the square of Jacobi polynomials in the beam-splitter transmittance. These photon-number probabilities are invariant to a set of physical and time-reversal symmetries. When one of the input photon-number states is the vacuum, the beam splitter simply deletes photons from the other port in Bernoulli fashion, as if they were classical particles. The output photon number is then described by the binomial distribution. If the inputs at the two ports are different number states, neither of which is the vacuum, the photon-number distribution is expressible in terms of summed and weighted products of the results for photomixing with the vacuum. If the inputs at the two ports are identical number states, and a beam splitter of transmittance \ensuremath{\tau}=(1/2 is used, the photon-number distribution assumes a simple but interesting form. It vanishes for odd photon numbers, indicating that the photons assemble in pairs at each output port. Finally, it is shown that homodyning quantum fluctuations can be reduced by using a balanced photomixer for arbitrary input states.

449 citations


Journal ArticleDOI
Jürgen Jahns1, Alan Huang1
TL;DR: This work proposes to integrate free-space optical components using planar technologies for their fabrication to solve the problem of precise mechanical alignment in complex optical systems comprising many individual components.
Abstract: In complex optical systems comprising many individual components, precise mechanical alignment becomes a difficult problem. We propose to integrate free-space optical components using planar technologies for their fabrication.

278 citations


Journal ArticleDOI
TL;DR: In this paper, the interference effects that can be observed in the two output arms of a lossless beam splitter are calculated for incident light in the form of a photon-pair excitation in two input arms.
Abstract: The interference effects that can be observed in the two output arms of a lossless beam splitter are calculated for incident light in the form of a photon-pair excitation in the two input arms. The output state that occurs when the photon pair is excited in a single input arm resembles that expected for independent classical particles, whereas quantum interference effects occur when the photon pair is divided between the two input arms. Detailed output photocount correlation functions are calculated for two-photon input states produced by a two-atom light source, a degenerate or nondegenerate parametric oscillator in a high-Q cavity, and an atomic cascade emission light source.

101 citations


Patent
20 Dec 1989
TL;DR: In this paper, a polarizing beam splitter is used to split a beam of light from a light source into two orthogonally polarized beams, and the recombined beam may be thereafter directed towards the light modulation system.
Abstract: An illumination system for an LCD projection display system to increase the brightness of the system. The system includes a polarizing beam splitter which splits a beam of light from a light source into two orthogonally polarized beams. The beam of the desired polarization direction is directed through a first face of a prism so that it reflects off of a second face of the prism and exists through a third face. The other beam of the non-desired polarization direction is passed through a device for rotating its polarization 90° and towards the underside of the second face of the prism at an angle such that it is refracted into the prism. Both beams then exit the prism through its third face, have the same polarization direction, and are only slightly divergent. The recombined beam may be thereafter directed towards the light modulation system. The illumination system minimizes the number of air-glass interfaces and the number of reflecting surfaces.

93 citations


Proceedings ArticleDOI
29 Jan 1989
TL;DR: A long-trace optical profiling instrument is now in operation at Brookhaven National Laboratory measuring surface figure and macro-roughness on large optical components, principally long cylindrical mirrors for use in synchrotron radiation beam lines as discussed by the authors.
Abstract: A new long-trace optical profiling instrument is now in operation at Brookhaven National Laboratory measuring surface figure and macro-roughness on large optical components, principally long cylindrical mirrors for use in synchrotron radiation beam lines. The non-contact measurement technique is based upon a pencil-beam interferometer system. The optical head is mounted on a linear air bearing slide and has a free travel range of nearly one meter. We are able to sample surface spatial periods between 1 mm (the laser beam diameter) and 1 m. The input slope data is converted to surface height by a Fourier filtering technique which distributes the random noise error contributions evenly over the entire trace length. A number of optical components have been measured with the instrument. Results are presented for fused silica cylinders 900 mm and 600 mm in length and for a fused silica toroid and several electroless nickel-plated paraboloids. 9 refs., 8 figs.

85 citations


Journal ArticleDOI
TL;DR: This experiment could be used to look for locality violations along the lines recently proposed by Grangier, Potasek, and Yurke, but without the need for a coherent reference beam for homodyning.
Abstract: A proposed experiment is analyzed theoretically. In the proposed experiment two coherent pump waves fall on two identical nonlinear crystals, down-converted signal and idler beams from the two crystals are mixed by two beam splitters, and the coincidence counting rate for photons leaving the beam splitters is measured. We show that this counting rate depends on the phase difference between the two coherent pump waves, and results from the interference of the vacuum with the down-converted photons. The experiment could be used to look for locality violations along the lines recently proposed by Grangier, Potasek, and Yurke [Phys. Rev. A 38, 3132 (1988)], but without the need for a coherent reference beam for homodyning.

81 citations


Patent
04 Apr 1989
TL;DR: The trichromatic beamsplitter as discussed by the authors consists of composited dichroic plates that separate a projected image into its three color components with spatial as well as spectral precision.
Abstract: The trichromatic beamsplitter consists of composited dichroic beamsplitter plates that separate a projected image into its three color components with spatial as well as spectral precision. The three linear array photosensor comprises a monolithic sensor having three parallel photodiode arrays spaced precisely to accept the color component images of the trichromatic beamsplitter. The present invention also employs a spectral and spatial combiner that is capable of maintaining equal optical path lengths of each spectral beam so that a single combined beam can be produced and can be employed in a number of different applications such as a color camera device, a color recording device, a graphics presentation device, an electronic color filter device, a color projector device and a multi-channel optical communication device.

72 citations


Journal ArticleDOI
TL;DR: In this article, the authors demonstrate a reduction in the coincidence-count rate when pairs of photons are combined in a beam splitter and show that this reduction occurs only when photon wave functions overlap and can permit accurate (sub-picosecond) relative timing measurements.
Abstract: A two-photon state can be selected by coincidence detection of photon pairs created in parametric downconversion. We demonstrate a reduction in the coincidence-count rate when pairs of photons are combined in a beam splitter. This reduction occurs only when photon wave functions overlap and can permit accurate (subpicosecond) relative timing measurements. We relate the width of the coincidence reduction to the bandwidth of the downconverted light and thence to the detailed phase-matching conditions in the parametric downconversion crystal. We also demonstrate that the loss of coincidences is associated with an increased probability of detection of photon pairs in each output of the beam splitter.

68 citations


Patent
15 Feb 1989
TL;DR: In this article, a new group of fiber optic switching devices that use layers of surface-established ferroelectric liquid crystals (FLCs) as the switching media are described. But the switches are not suitable for direct optical signals.
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 a an angle of 90 degrees (normal incidence) with the surface plane. Each FLC gives 0 degrees or 90 degree 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 include voltage controlled 2×2, 1×4, 1×6, 1×8, 4×4 and dual plane devices that use one or more layers of surface stabilized ferroelectric liquid crystals to direct optical signals.

67 citations


Patent
21 Apr 1989
TL;DR: In this article, a pair of transparent trapezoidal prisms each having angled end faces with the larger bases in juxtaposition with respect to each other forming an interface therebetween are provided with at least one optical input and output coupled to the angled endfaces of the prisms.
Abstract: A pair of transparent trapezoidal prisms each having angled endfaces with the larger bases in juxtaposition with respect to each other forming an interface therebetween are provided with at least one optical input and output coupled to the angled endfaces of the prisms. Optical radiation is applied to the input and normal to the angled endface at an angle greater than the critical angle with respect to the interface between the prisms. A liquid crystal beam splitter is positioned in the interface for splitting the radiation between the prisms each of which has a liquid crystal optical shutter positioned in the respective prisms to receive optical radiation which has been transmitted or reflected from the beam splitter at an angle normal to the optical shutter. Each of the shutters is provided with a variable biasing voltage of a continuous nature which is selectively variable for controlling the radiation passing therethrough thereby forming a controllable optical switch.

55 citations


Journal ArticleDOI
TL;DR: Theoretical analysis indicates that the optical characteristics of reflection Fresnel lenses can be improved compared with a conventional transmission micro-Fresnel lens and their use in an integrated focus sensor is proposed.
Abstract: Blazed reflection micro-Fresnel lenses and their use in an integrated focus sensor are proposed. Theoretical analysis indicates that the optical characteristics of reflection Fresnel lenses can be improved compared with a conventional transmission micro-Fresnel lens. These reflection Fresnel lenses were fabricated using electron-beam lithography and exhibited the diffraction-limited focusing characteristics with 71% high efficiency. The focus sensor has a folded optical path and includes a beam splitter integrated with thin film components, such as a reflection elliptical Fresnel lens and a quadrant photodetector. The reflection elliptical Fresnel lens in the focus sensor exhibiting excellent astigmatic characteristics agreed with the theoretical results, and the focus error signal was detected. This sensor can be developed as the optical head of an optical disk system.

Journal ArticleDOI
TL;DR: In this article, the usual amplitude and phase relations connecting the reflectance and transmittance of a beam splitter can be derived by a simple energy balance argument relating to a Michelson interferometer.
Abstract: It is shown that the usual amplitude and phase relations connecting the reflectance and transmittance of a stratified or continuous, nonabsorbing beam splitter can be derived by a simple energy balance argument relating to a Michelson interferometer.

Journal ArticleDOI
TL;DR: In this paper, a new experimental procedure for determining the second-order coherence time of a light beam is described that is based on a combination of conventional interferometry with an intensity correlation technique.
Abstract: A new experimental procedure for determining the (second-order) coherence time of a light beam is described that is based on a combination of conventional interferometry with an intensity-correlation technique. It permits measurements of coherence times that are several orders of magnitude shorter than the resolving times of the detectors, which ordinarily limit correlation measurements. The validity of the method is demonstrated by an experiment in which the transverse fluorescent light from a dye laser is measured.

Patent
Tomio Sonehara1
06 Sep 1989
TL;DR: In this paper, a dichroic optical element disposed on at least one surface of each of four right angled prisms for transmitting and reflecting different wavelengths of polarized light was used for image projection.
Abstract: A dichroic optical element disposed on at least one surface of each of four right angled prisms for transmitting and reflecting different wavelengths of polarized light. Each of the dichroic layers is characterized by wavelength selection properties which vary in response to the polarization of the light received by the dichroic layers. A projection type display device includes a first optical device characterized by at least one first wavelength transition region and a second optical device characterized by at least one second wavelength transition period. The first wavelength transition region does not effectively overlap the second wavelength transition region. Efficient utilization of the light source for projecting an image results.

Journal ArticleDOI
TL;DR: The diffraction by two planar slanted fringe gratings superposed in the same volume of an anisotropic medium is treated using rigorous 3-D vector coupled wave analysis using the various Bragg conditions identified and quantified.
Abstract: The diffraction by two planar slanted fringe gratings superposed in the same volume of an anisotropic medium is treated using rigorous 3-D vector coupled wave analysis. Arbitrary angle of incidence and polarization are included. Both phase and/or amplitude slanted gratings in anisotropic media are treated in the analysis. The external boundary regions can be either isotropic (for bulk applications) or uniaxial anisotropic (for integrated applications). Both forward- and backward-diffracted orders are characterized by a number pair (i1,i2), where i1 and i2 are integers. The Floquet condition is discussed for the case of two superposed gratings. When the external regions are anisotropic, each diffracted order has an ordinary (O), and an extraordinary (E) component. The analysis is also generalized for an arbitrary number of superposed gratings. The numerical complexity is discussed. In the case of equal grating periodicities along the boundaries, the diffracted orders become degenerate in the external regions. In this case, an alternative analysis that utilizes a cascaded stack of unslanted gratings can be used. Limiting cases are also presented. The various Bragg conditions are identified and quantified. Sample calculations presented include the quantification of the crosstalk between two superposed gratings, the evaluation of the effects of coupled Bragg conditions in beam combining applications, design and analysis of a beam splitter and a beam combiner, demonstration of the use of a cascaded stack of unslanted gratings of constant modulation to represent two superposed gratings that have the same periodicity along the boundaries, and finally evaluation of the effect of the phase difference between two gratings. The same analysis applies in the limiting cases of isotropic materials, single slanted gratings, etc. Applications of this analysis include optical storage, optical digital truth table look-up processing, neural nets, optical interconnects, beam splitting, and beam combining.

Patent
16 Jun 1989
TL;DR: In this article, a tilt servo mechanism using photodetectors for detecting rays of light reflected from the recording surface of an optical disk is described. But the tilt signal is obtained as the differential output of the two detector cells.
Abstract: An optical head device includes a tilt servo mechanism using photodetectors for detecting rays of light reflected from the recording surface of an optical disk. The rays of light are obtained from a laser diode used as a light source for information reproduction. According to one aspect; prisms are formed on the flange of a converging lens to refract peripheral portions of the light emitted from the laser diode for tilt detection. According to another aspect, secondary diffraction grating domains at the sides of the primary diffraction domain of a diffraction grating diffract peripheral portions of the emitted rays of light for tilt detection. According to another aspect, a mirror reflects peripheral portions of the emitted rays from the laser diode. According to a further aspect a mirror reflects the light from the laser diode passing through a beam splitter. Each photodetector receiving the light reflected from the recording surface of the disk may be partitioned into two detector cells, and a tilt signal is obtained as the differential output of the two cells.

Patent
11 Jul 1989
TL;DR: In this article, a beam splitter is used to divide a ray from a light source into a plurality of light beams which are detected by a set of cameras and then used to determine authorized use of the key when one or more cameras produce electrical outputs.
Abstract: A new optical theft deterrent device is disclosed wherein a ray from a light source (22) is divided by a beam splitter (13) mounted on a key (10) into a plurality of light beams which are detected by photosensors (14-17) to determine authorized use of the key (10) only when predetermined one or ones of the photosensors (14-17) produce electrical outputs. The beam splitter (13) serves to uniformly divide the ray from the light source (22) into the light beams and also to accurately guide these beams toward the photosensors (14-17). The key (10) may be utilized to mechanically and electrically unlock a locking device (19, 20). The new system may preferably be applied to a steering column shaft locking device (19) to prevent theft of an automotive vehicle on which the system is equipped.

Patent
20 Dec 1989
TL;DR: In this paper, a beam splitter separates light pulses from a single source diode to supply light pulses for both internal and external passages, which are processed in a CPU for calculating distance with reduced errors due to frequency drift.
Abstract: A light wave distance measuring instrument uses a light receiving diode for receiving both light from a light source diode coupled via an internal light passage and light from the light source diode coupled via an external light passage. A beam splitter separates light pulses from a single source diode to supply light pulses for both internal and external passages. A reference signal is sampled using detected signals representing the timing of received internal reference light pulses and external measurement light pulses to provide first and second signals with phase difference representing measured distance. These signals are processed in a CPU for calculating distance with reduced errors due to frequency drift. By introducing an optical fiber delay medium, reflected light pulses are separated in time from the internal reference pulses so that these pulses can be used directly for differential time determination purposes and the measurement of distances to objects close to the measuring instrument is made possible.

Patent
28 Jun 1989
TL;DR: An optical scanning system has a deflector for deflecting a beam emitted from a light source, a telecentric scanning lens for focusing the deflected beam onto a scanning surface, a beam splitter for splitting a beam reflected by the scanning surface on an optical path between the deflector and the light source portion from an outgoing optical path.
Abstract: An optical scanning system has a deflector for deflecting a beam emitted from a light source portion, a telecentric scanning lens for focusing the deflected beam onto a scanning surface, a beam splitter for splitting a beam reflected by the scanning surface on an optical path between the deflector and the light source portion from an outgoing optical path, and a focus point detector for receiving the beam split by the beam splitter and detecting a focused state of the beam on the scanning surface.

Journal ArticleDOI
TL;DR: The critical power is reduced significantly by "freezing" a nonsinusoidal refractive index into the basic linear structure that mimics the non linear index above the critical power, thus biasing the nonlinear coupler.
Abstract: Propagation in a nonlinear coupler at a specified input power is like that in a linear coupler with a specified but nonsinusoidal periodic refractive index. This suggests novel schemes for reducing the switching power and leads to simple analytical expressions for ideal switches and for power-sensitive polarization beam splitters. Most importantly, we show that the critical power is reduced significantly by "freezing" a nonsinusoidal refractive index into the basic linear structure that mimics the nonlinear index above the critical power, thus biasing the nonlinear coupler.

Patent
25 Jul 1989
TL;DR: In this paper, an optical routing module for sample inspection in a light microscope was proposed. But the primary light source was not considered. And it was not shown that the secondary light output from the sample is subjected to a different one of transmission and reflection from that to which the primary beam is subjected at each of the first and second polarizing beam splitters, which are further formed and arranged for defining a secondary light beam pathway from the inlet to the outlet.
Abstract: The present invention relates to an optical routing module (2) suitable for use in a light microscope (1) for sample inspection simultaneously with a primary light source (10) and a secondary light source (7) of different wavelength. The module (2) comprises a housing mounting first and second polarizing beam splitters PBS1, PBS2 along a primary light beam pathway through the module and having secondary light beam inlet and outlet means (5,6) opposite different ones of the polarizing beam splitters PBS1, PBS2, which have a narrow predetermined operating wavelength range, defined between s- and p-plane transitional wavelengths, which substantially excludes the primary light source wave length band and such that at least one polarizing plane component of each of the secondary light source and a secondary light output from the sample is subjected to a different one of transmission and reflection from that to which the primary light source is subjected at each of the first and second polarizing beam splitters PBS1, PBS2, which are further formed and arranged for defining a secondary light beam pathway from the inlet (5) to the outlet (6) so that the secondary light beam pathway is brought substantially into alignment with an outward leg of said primary beam pathway upstream of the sample by said first polarizing beam splitter PBS1 and is separated back out from a return leg of said primary light beam pathway downstream of the sample by said second polarizing beam splitter PBS2 whereby in use of the module (2) in a light microscope (1), the area of incidence of the secondary light beam with the sample may be monitored via the primary light beam.

Patent
24 Aug 1989
TL;DR: In this article, a beam splitter is used to split a light beam into two components which are then processed to produce an output indicating the AC and DC components of the current flowing in the conductor.
Abstract: A sensor (1) for sensing the magnitude of current flowing in a conductor (12) based upon the Faraday effect. The sensor (10) includes a light source (14) for emitting a beam of light which is transmitted through the magneto-optic material (28) with one or more layers which causes a rotation of the plane of polarization of the light beam in proportion to the current flowing in the conductor (12). The beam of light with the rotated plane of polarization is split by a beam splitter (38) into two components which are then processed to produce an outputs (62, 63) indicative of the AC and DC components of the current flowing in the conductor. The outputs (62, 63) produced are independent of system losses.

Patent
01 Mar 1989
TL;DR: In this paper, a dual high stability interferometer system capable of measuring linear and angular displacement simultaneously of a movable plane mirror (90) comprises a frequency stabilized laser input beam (10) which is divided into two parallel spatially displaced beams by a beamsplitter.
Abstract: A dual high stability interferometer system capable of measuring linear and angular displacement simultaneously of a movable plane mirror (90) comprises a frequency stabilized laser input beam (10) which is divided into two parallel spatially displaced beams by a beamsplitter (14). An optical system (20) is disposed to produce a first output beam having two orthogonally polarized components in which the phase difference between the two components of the third output beam is related to four times the linear displacement of the movable plane mirror (90) at a first position. A polarizer (93) mixes the orthogonal components of the third output beam with the interference between the two polarization components being detected by a photodetector (94) which produces an electrical signal (96) from which a phase meter/accumulator (99) extracts the phase change, with this phase change being related to four times the linear displacement of the movable mirror (90) at the first position. The optical system (20) also produce a second output beam whose orthogonally polarized components have a phase difference related to four times the linear displacement of the movable mirror (90) at a second position. Another polarizer (95) mixes these orthogonal components and a photoelectric detector (194) and another phase meter/accumulator (109) cooperate to provide a second measured phase which is related to four times the linear displacement of the movable mirror (90) at the second position.

Patent
18 Sep 1989
TL;DR: In this article, the beam splitter is arranged in series on the laser beam path of a laser oscillator and a total reflection mirror is provided on the extension line thereof, so that the branching ratio of the reflection and transmission rates of the splitters is adequately set to uniformize the beam output to each laser head 4a-4d.
Abstract: PURPOSE:To uniformize working and to reduce the device cost by arranging in series the beam splitter transmitting one part of a beam and reflecting one part on the optical path of a laser beam and providing a stopping means on a refracted beam path. CONSTITUTION:Beam splitters 9a-9c are arranged in series on the laser beam path of a laser oscillator 6 and a total reflection mirror 10 is provided on the extension line thereof. In this case, the branching ratio of the reflection and transmission rates of the splitters 9a-9c is adequately set to uniformize the beam output to each laser head 4a-4d. The beam output is finely adjusted by providing a beam stopping device A on each head. The beam output of the laser head 4a-4d is thus equalized correctly and surely and the simultaneous machining of each head for a work W is uniformized. The device cost is reduced because the device structure is simplified.

Patent
Karl-Ulrich Stein1
18 Sep 1989
TL;DR: In this article, an optoelectronic transmission and reception device includes an optical transmitter inserted into a silicon wafer as a laser chip composed of III/V compound semiconductor material.
Abstract: An optoelectronic transmission and reception device includes an optical transmitter inserted into a silicon wafer as a laser chip composed of III/V compound semiconductor material, an optical receiver inserted into the silicon wafer as a reception diode chip composed of III/V compound semiconductor material or which is monolithically integrated into the silicon wafer as a metal-semiconductor diode. A coupling optics for connection to an optical fiber is monolithically integrated into the silicon wafer, as is a controller that includes a drive circuit for the transmitter and a pre-amplifier circuit for the receiver, a wavelength selective beam splitter and light wave guides for light guidance. The device is particularly useful as a bi-directional transmission and reception module.

Patent
03 Apr 1989
TL;DR: An optical pickup device for optically reproducing an information recorded on a recording medium of a magneto-optical disc or a write-only-read-many optical disc, which includes a semiconductor laser, an objective lens for converging the laser light emitted by the laser on the recording medium, a photo-detector for detecting a light reflected from the record medium, and a beam splitter for leading the emitted light from the laser to the objective lens and for leading said light reflected by the record to the photodetector, a first phase plate disposed between the beam
Abstract: An optical pickup device for optically reproducing an information recorded on a recording medium of a magneto-optical disc or a write-only-read-many optical disc, includes a semiconductor laser, an objective lens for converging the laser light emitted by the laser on the recording medium, a photo-detector for detecting a light reflected from the recording medium, a beam splitter for leading the emitted light from the laser to the objective lens and for leading said light reflected by the recording medium to the photodetector, a first phase plate disposed between the beam splitter and the objective lens, a second phase plate disposed between the beam splitter and the photo-detector, and a rotator for rotate the first phase plate in such a manner than the beam splitter forbids to transmit the light reflected by the recording medium into the laser in a case where the recording medium is said write-only-read-many optical disc, and that the beam splitter allows to transmit the light reflected by the recording medium into the laser in a case where the recording medium is the magneto-optical disc.

Journal ArticleDOI
TL;DR: In this paper, a beam splitter which can split one beam of a laser into an array of 25x25 uniform intense beams has been designed and fabricated, which shows uniformity better than 96% and diffraction efficiency over 60%.

Patent
11 Apr 1989
TL;DR: In this article, a spatial heterodyne spectrometer has a two-beam dispersive interferometer which includes a diffraction grating as a beam splitter/combiner.
Abstract: A spatial heterodyne spectrometer has a two beam dispersive interferometer which includes a diffraction grating as a beam splitter/combiner. An incoming beam is collimated and passed to the grating in the interferometer where it is split into two beams which are recombined such that the angle between the wavefronts in the recombined beam at a particular wavelength is directly related to the deviation of that wavelength from a null wavelength at which the wavefronts are parallel. The recombined output beam is focused and imaged to produce Fizeau fringes across the output aperture, with these fringes being recorded on an imaging detector. The spatially varying intensity output of the imaging detector is Fourier transformed to yield an output indicative of the spectral frequency content of the image which is related to the wavelength content of the incoming beam from the source.

Patent
05 Dec 1989
TL;DR: The differential interference microscope (DIM) as mentioned in this paper is a beam splitter and a compensator, either one being made of a positive birefringent substance and the other being made by a negative birelating substance, which are arranged in such a way that the optic axes of both the prisms are located substantially on the same plane.
Abstract: The differential interference microscope comprises a beam splitter and a compensator, either one being made of a positive birefringent substance and the other being made of a negative birefringent substance, which are arranged in such a manner that the optic axes of both the prisms are located substantially on the same plane, or a polarizing optical element composed by combining a wedge-shaped prism made of a positive birefringent substance with another wedge-shaped prism made of a negative birefringent substance in such a manner that the optic axes of both the prisms are located substantially on the same plane. The differential interference microscope is capable of providing a uniform visual field without enhancing manufacturing cost therefor nor enlarging the space to be occupied thereby.

Patent
23 Jun 1989
TL;DR: In this paper, the authors proposed a method for enhancing the accuracy of laser optical measuring instruments using fringe pattern spacing, in which the emitted beams are automatically deflected in response to wavelength changes of the laser beam 16 such that variations in the fringe spacing, due to variations in laser beam16 wavelength, are compensated by variations of the closing angle of the emitted, deflected beams.
Abstract: Methods and apparatus for enhancing the accuracy of laser optical measuring instruments using fringe pattern spacing are disclosed. The apparatus in one embodiment includes a laser beam source 10, a beam splitter 14, and mirrors 22 to deflect the beams 18, 20 emitted from the beam splitter 14 to a sensing volume. Alternative embodiments include prisms 42, 44, gratings 62 or other optical devices in lieu of mirrors 22. Objects passing through the sensing volume scatter light which is detected by the instrument to determine, among other things, the velocity of the object. The emitted beams 18, 20 are automatically deflected in response to wavelength changes of the laser beam 16 such that variations in the fringe spacing, due to variations in laser beam 16 wavelength, are compensated by variations in the closing angle K of the emitted, deflected beams. The fringe pattern spacing is thereby held more nearly constant enhancing the accuracy of the instrument. Methods of enhancing the accuracy of measurements taken with laser optical measuring instruments are also disclosed.