Showing papers on "Beam splitter published in 1981"

General properties of lossless beam splitters in interferometry

Abstract: The author uses spinor algebra to investigate general properties of lossless beam splitters in interferometry.(AIP)

Optical fiber interferometers with [3×3] directional couplers: Analysis

Abstract: All‐guided wave interferometers using [3×3] directional couplers as beam splitters are analyzed in detail The characteristics of such interferometers are compared with those of conventional interferometers using [2×2] beam splitters It is shown that there are advantages in using [3×3] couplers instead of [2×2] couplers in the Mach‐Zehnder interferometric sensors and the Sagnac rotation sensors (gyroscopes)

Optical information reading device

Abstract: An optical information reading device adapted to apply a light beam from a light source to an information carrier having information recorded thereon as convexities and concavities or variations in a light reflecting factor, and to receive the light reflected from the information carrier, thereby to read the information. A specific arrangement of optical elements such as a beam splitter, lens, and reflecting mirror enables the information reading device as a whole to be reduced in size particularly in length in the direction perpendicular to the plane of the information carrier.

High efficiency optical tank for three color liquid crystal light valve image projection with color selective prepolarization and single projection lens

Abstract: A full color high contrast image projection system with oil coupled dichroics and a single projection lens is disclosed. The invention includes a unitary optical tank in which a prepolarizer and dichroic separators are mounted in fixed alignment relative to a main polarizing prism. The prepolarizer acts on the incident light from a source to polarize the green light and reflect the S component out of the system. The red and blue components are transmitted unchanged. The main polarizer is mounted at a 90° twist relative to the prepolarizer so that it reflects the green light to a first light valve via a first dichroic separator. The polarized red and blue components are transmitted to second and third light valves via a second dichroic separator. The light valves modulate the polarization state of incident light before returning it to the second beamsplitter. The second beamsplitter then recombines the individual beams into a single output beam. This beam is projected by a telecentric projection lens to provide a full color high contrast image.

Analysis of a Polarizing Michelson Interferometer for Dual Beam Fourier Transform Infrared, Circular Dichroism Infrared, and Reflectance Ellipsometric Infrared Spectroscopies

Abstract: The properties of a Fourier transform infrared (FT-IR) spectrometer designed around a polarizing Michelson interferometer (PMI) are analyzed with respect to applications in both conventional absorption as well as polarization spectroscopies. The PMI design is that of Martin and Puplett and consists of a metal grid polarizing beam splitter combined with rooftop retromirrors set to rotate the polarization direction in each beam by 90°. If used in conjunction with additional grid polarizers, positioned according to application, the result is an FT-IR instrument that can function both as a dual beam absorption spectrometer and as a polarization spectrometer. Operating in the former mode, the instrument is predicted to achieve speeds comparable to those achievable using a nonpolarizing dual beam Michelson interferometer but to cover a much wider spectral range due to the achromatic nature of metal grid polarizing beam splitters. In the latter mode, it is predicted to give at least double the effective throughput achievable with conventional instruments equipped with external polarization modulating optics, and again to cover a much wider spectral range. It would extend the capability of determining circular dichroism spectra into the far IR (down to ∼3 cm−1) for the first time. With the development of a process for forming a metal grid polarizer of fine spacing (∼0.1 μm) on a KBr substrate, the instrument would be capable of covering the spectral range 25 000 to 3 cm−1 or lower using only two beam splitters, i.e., in two ranges: 25 000 to 450 cm−1 using a KBr-supported metal grid, and 600 to 3 cm−1 or less using an unsupported wire grid.

Tandem multipass Fabry-Perot interferometer for Brillouin scattering.

Abstract: A new design of a plane mirror Fabry-Perot interferometer with the mirror blanks freely supported by horizontal rings is described. Special attention is paid to the surface flatness and dielectric coatings of the mirrors. It is shown that any two piezoelectrically scanned Fabry-Perot interferometers can be synchronized in tandem operation using simple optics and standard electronic driving and stabilization equipment. Applications of the tandem system to Brillouin scattering are given. The observation of Brillouin spectra of supported thin plastic films and of a clamped metal surface is reported.

Optical fiber gyroscope with (3×3) directional coupler

Abstract: A Sagnac rotation sensing interferometer disposed on a rotating platform for use as a gyrsocope comprising a closed optical light path and a beam splitter for splitting an input light beam into two beams directed to transverse the closed optical path in opposite directions wherein the beam splitter is composed of a directional coupler with three input ports and three output ports. The first of the three input ports receives optical input and the second and third of the input ports are disposed symmetrically with respect to the first input port. Optical output from two output ports corresponding to the second and third input ports are directed to both ends of the closed optical fiber light path. A gyroscope according to this arrangement provides light output from the beam splitter which operates automatically near quadrature without a nonreciprocal π/2 phase bias applied in the fiber loop as required in conventional optical fiber gyroscopes.

Optical fiber transmission system and dichroic beam splitter therefor

Abstract: A dichroic beamsplitter includes two glass prisms, each having an isosceles right triangular cross section, with a multilayer dielectric coating sandwiched therebetween Each layer of the coating is tuned for quarter-wave operation with 45° incidence of light at 083 μm The coating comprises 53 layers of three different materials arranged in a specific order The materials have refractive indexes of 145, 1625, and 225 and can be, for example, silicon dioxide, aluminum oxide, and titanium oxide An optical fiber transmission system includes an optical fiber and a beamsplitter at opposite ends thereof One of the beamsplitters is oriented with respect to the fiber at 43° incidence and has a high nonpolarizing reflectance at a wavelength λ2 and a low loss transmission at a wavelength λ1 The other beamsplitter is oriented with respect to the fiber at a 47° incidence and has a high nonpolarizing reflectance at the wavelength λ1 and a low loss transmission at the wavelength λ2 The value of the wavelength λ1 is 081 μm and the value of the wavelength λ2 is 085 μm A combination, including a dichroic beamsplitter having a high nonpolarizing reflectance at the wavelength λ2 and low loss transmission at the wavelength λ1, has a signal at the wavelength λ1 to one side thereof An optic fiber receives the signal to the wavelength λ1 at an opposite side of the beamsplitter A signal at the wavelength λ2 is provided to the beamsplitter at a third side thereof, perpendicular to both aforesaid sides, so that the signal at the wavelength λ2 is reflected to the optic fiber for transmission therethrough A detector for power monitoring is coupled to a fourth side of the beamsplitter, the fourth side being directly opposite to the third side thereof

Alignment stabilization prism

Abstract: Apparatus (20) provides a stable optical reference in the presence of optical source jitter. It comprises a beamsplitter cube (21) having an input surface 22, an output surface 23, a totally reflecting surface (24), and a partially reflecting diagonal surface (26) with a corner cube 27 disposed on a surface (25) opposite to the input surface. An input beam (30) applied to the beamsplitter cube results in two output beams (33, 33'), coplanar with an output optical axis (31), if the input beam deviates at 32 from an input optical axis. The two output beams deviate equally but oppositely from the output axis. This provides signals from which a stable output optical axis may be determined. A polarization-sensitive embodiment is also disclosed which eliminates problems associated with the use of coherent light sources.

Liquid crystal light valve image projection system with color selective prepolarization and blue mirror

Abstract: An optical system is disclosed which incorporates a color selective prepolarizer to improve contrast and reduce stress induced birefringence while allowing a blue mirror to be used to enhance the projected image. The invention includes a source lamp for providing a first beam of unpolarized white light energy; a prepolarizing beam splitter which extracts from the first beam, second and third beams. The second beam contains undesirable color components of a first polarization state, which are removed from the system by reflection to an optical dump. The third beam includes prepolarized light of one color and the first polarization and white light of the second polarization. A main polarizing prism is provided for splitting the third beam into fourth and fifth beams having the first and second polarizing states respectively. The main prism effectively directs the white light to the light valve where it is modulated and returned to the main prism for projection in the conventional manner. The fifth beam being monochromatic and of the first polarization state is directed to the blue mirror where it is filtered to remove residual red and green components, altered in polarization state from the first state to the second state and altered in intensity by a preselected gradient operator before being returned to the main prism for superimposition on the light valve image. The invention includes projection optics for displaying the composite image.

Photon probe fault locator for single-mode optical fiber using an acoustooptical light deflector

Abstract: A new backscattering technique for diagnosing the attenuation characteristics, spatial imperfections with length (fault location), and splice loss in a single-mode optical fiber has been developed by using a TeO 2 acoustooptical light deflector operating at 120 MHz. Due to the small insertion loss and high extinction ratio of the deflector, the dynamic range of the backscattered signal has been increased by at least 10 dB, which corresponds to the extension of 5 km in measurable length for fiber loss of 1 dB/km, compared with the conventional back-scattering technique in which the beam splitter and polarizer-analyzer combination are utilized. Another advantage of this technique is in that the saturation of the amplifier is avoided by arbitrarily cutting off a large power in the early stage of the Rayleigh scattering signal. A single-mode fiber of 19.2 km in length has been examined, and the distance for fault location up to 18.4 km was obtained.

Laser doppler velocimeter

Abstract: Reflections, having positive and negative Doppler frequency shifts, from a laser beam directed at a moving surface are passed through spatial filters, combined by a beam splitter, and focussed on an observation plane of a photodetector to provide a fringe pattern having an amplitude variation frequency responsive to the velocity of the moving surface. The laser beam may be a single beam directed substantially perpendicularly to the moving surface, or the laser beam may be divided into two beams angled toward the surface, one beam impinging with the direction of motion of the surface and the other beam impinging against the direction of motion. When two impinging beams, split from a common beam, are utilized, different polarizations and beam impingement points on the surface may be used to provide beam isolation between the beam signals. Homodyne detection with single frequency lasers is used. With multi-mode lasers emitting two separate frequencies of radiation, heterodyne detection may be used to provide better resolution at low surface velocities.

Helmet mounted eye tracker using a position sensing detector

Abstract: A helmet mounted eye tracker is disclosed for monitoring the position of cornea of a human eye which includes an infrared light source for projecting a pulsed infrared light beam along a first optical path, a mirror for redirecting the pulsed infrared light beam along a second optical path, and a beam splitter for redirecting the pulsed infrared light beam onto the cornea of the eye such that within the eye a virtual image is formed which changes position with movement of the cornea of the eye The virtual image formed within the eye is then redirected along the second optical path by the beam splitter to the mirror which, in turn, redirects the virtual image to a collecting lens positioned along the first optical path The collecting lens will then focus the virtual image upon the active area of an infrared light detector which will provide at its output square wave signals indicative of the X and Y coordinate positions of the cornea of the eye within the active area of the infrared light detector

Optical scanning apparatus with beam splitter to provide plural light beams

Abstract: A scanning apparatus for obtaining plural scanning beams, wherein plural stationary light beams are incident upon a deflecting reflection surface in different directions, but they are superposed with each other on the reflection surface Plural scanning beams are provided from the deflecting reflection surface Since the plural beams are superposed on the reflection surface, the center of deflection is the same for all of the light beams, so that the scanning beams are easily processed by a single optical system

Method and apparatus for the interferometric wavelength measurement of frequency tunable C.W. lasers

Abstract: The invention relates to a method and an apparatus for measuring the wavelength of an object beam of electromagnetic radiation generated from a first source by comparing with a reference of known wavelength generated from a second source A fringe-counting Michelson-type interferometer is used, having a stationary arm and a variable arm and includes a planar beam splitter a planar beam mixer, a planar reflector in the stationary arm, and a movable retroreflector in the variable arm. Prior to moving the retroreflector the reference and object beams are aligned to provide a flat interference pattern. The portions of the reference and object beams in the moveable arm are directed to and reflected by the retroreflector off center thereof. The portions of the reference and object beams in the stationary arm have an angle of reflection α at the reflector. The beam mixer is situated relative to the beam splitter such that the plane of the beam mixer is angularly inclined with respect to the plane of the beam splitter by an angle equal to α. Parallelism of the second beam portions with one another in the variable arm of the interferometer is automatically provided as a result of the alignment of the reference and object beams to a flat interference pattern, without optical feedback of the beams to their respective source and parasitic diffraction effects by the retroreflector.

Dispersionless refractor for use with high-power lasers

Abstract: A beam splitter or combiner suitable for use with high-power laser beams employs matched dispersive elements to correct for dispersion of a separated beam.

Wide Angle, Color, Holographic Infinity Optics Display.

Abstract: : This project demonstrates the feasibility of producing a holographic compound spherical beamsplitter mirror with full color response. Furthermore, this holographic beamsplitter was incorporated into a Pancake Window display system as a replacement for the classical glass spherical beamsplitter and its performance and color capabilities have been demonstrated. (Author)

Beam splitter optical system of signal pickup device

Abstract: An optical system for use in a signal pickup device of, for example, an optical video and/or audio disc player, comprising a beam splitter prism composed of two component segments forming therebetween a light polarization or semi-reflective mirror plane inclined at the angle of 45 degrees to a predetermined path of light through the prism, each of the component segments having an outwardly curved surface portion through which the path of light extends.

Scanning laser radar

Abstract: In an optical radar system a coherent signal is transmitted at a variable position and the return signal, that is, the reflected portion of the coherent signal is received and coherently detected. The transmitter utilizes a scanning laser having an electron beam that impinges upon a variable reflectance mirror that terminates one end of an optical cavity. An oscillating mode is generated within the resonant cavity when the electron beam locally heats the surface of the variable reflectance mirror to create a pixel that reflects light in a diffracted pattern. The receiver utilizes a stable single mode laser to illuminate a variable reflectance surface. A receiver electron beam generates a plurality of receiver pixels at various positions. The diffracted light from each pixel generates a plurality of variable angle local oscillator beams that are summed with the return signal at a beamsplitter. The output of the beamsplitter is applied to the surface of a detector array. One of the local oscillator beams is positioned such that the return signal and the local oscillator beam overlap at one of the detectors in the array to provide coherent detection. The frequency of the first coherent signal and the second coherent signal are sampled by a first and second partially reflecting mirror. A frequency detector detects the output of the first and second partially reflecting mirror to detect the frequency difference between the first and second coherent signal and generate a control signal that adjusts the frequency of the first coherent signal. For heterodyne operation a selected frequency difference is generated whereas for homodyne detection a zero frequency difference is generated. An electronic computer coordinates the position of the scanning laser of the transmitter and the position of the local oscillator beams of the receiver such that one of the local oscillator beams will overlap with each of the corresponding return signals at the detector array. A second electronic computer processes the output of the detector array to provide information about the return signal.

Agile receiver for a scanning laser radar

Abstract: In an optical radar system a coherent signal is transmitted at a variable position and the return signal, that is, the reflected portion of the coherent signal is received and coherently detected. The transmitter utilizes a scanning laser having an electron beam that impinges upon a variable reflectance mirror that terminates one end of an optical cavity. An oscillating mode is generated within the resonant cavity when the electron beam locally heats the surface of the variable reflectance mirror to create a pixel that reflects light in a diffracted pattern. The receiver utilizes a stable single mode laser to illuminate a variable reflectance surface. A receiver electron beam generates a plurality of receiver pixels at various positions. The diffracted light from each pixel generates a plurality of variable angle local oscillator beams that are summed with the return signal at a beamsplitter. The output of the beamsplitter is applied to the surface of a detector array. One of the local oscillator beams is positioned such that the return signal and the local oscillator beam overlap at one of the detectors in the array to provide coherent detection. The frequency of the first coherent signal and the second coherent signal are sampled by a first and second partially reflecting mirror. A frequency detector detects the output of the first and second partially reflecting mirror to detect the frequency difference between the first and second coherent signal and generate a control signal that adjusts the frequency of the first coherent signal. For heterodyne operation a selected frequency difference is generated whereas for homodyne detection a zero frequency difference is generated. An electronic computer coordinates the position of the scanning laser of the transmitter and the position of the local oscillator beams of the receiver such that one of the local oscillator beams will overlap with each of the corresponding return signals at the detector array. A second electronic computer processes the output of the detector array to provide information about the return signal.

Tilt head camera for interferometric analysis of tires

Abstract: An adjustable camera is operative to perform interferometric analysis of areas on the surface of an object such as a vehicle tire using light from a coherent source. The camera mechanism includes vertical guides projecting upwardly from a support moveable in the horizontal plane along the base. A slide is adjustable vertically along the guides and carries a camera housing that is adjustable relative to the slide about a horizontal pivot axis. A coherent light source is fixed relative to the base and projects its beam parallel to the adjustment of the guide support. An optical element on the guide support projects the beam upwardly parallel to the guides to a mirror which reflects the beam horizontally about the pivot axis of the housing. A beam splitter divides the beams into an object beam and a reference beam. The object beam is projected out of the housing to illuminate a surface of the tire and cause light to be reflected to a film section supported in the housing. The camera housing may be moved horizontally and vertically and tilted to various angles to analyze various sections of the tire, without impairing the required positional relationship to the coherent light source.

Angular alignment sensor

Abstract: A sensor for measuring angular deviations of a radiation beam relative to a reference plane. The sensor comprises a shearing interferometer block formed of a beamsplitter cube having a first reflecting device on one face of the cube for forming a first exit beam and a second reflecting device on the opposite face of the cube for forming a second exit beam. The first device can be a corner cube or a flat block mirror. The second device can be a right angle prism for one dimensional measurements and a 90° pyramid prism for two-dimensional measurements. A photo-detector unit is adjacent to and spaced from the beam splitter cube and has a number of detector members across the path of travel of the wavefronts of the exit beams. The detector members provide output signals which can be used to calculate the angular deviation of the incoming beam from a normal to the reference plane. The optical path difference between the two arms of the interferometer block are equal substantially to odd multiples of one-fourth the wavelength of the incoming radiation. The sensor is accurate to better than 0.001 arc seconds of angular measurements for a photodetector unit whose maximum transverse dimension is 2.5 cm.

Optical memory system for a reading/writing, verifying and tracking module

Abstract: A single semiconductor laser (10) is utilized in an optical system (2) to record and readback from a recording media such as a spinning disk (24). By means of a retro-reflecting light and optical system, the same optical path can be used not only for recording, but for readback of the recorded data on the recording media (24). A polarizing beam splitter (16) causes the light beam (8) to pass through an optical system whereby both focus error and tracking error as well as the data signal can be generated. By dithering the light beam across the recorded track in accordance with data signal, a tracking error signal is generated to cause the dithering motion of the galvanometer (20) to maintain its center tracking of the recorded information. By the use of a separate beam splitter (30), a focus error signal can be detected by means of error signals from complementary detectors S1, S2 to maintain accurate focus of the applied light beam on the recording media.

Electronic camera employing a solid-state image sensor.

Abstract: An electronic camera which focuses images of an object on the image plane by means of suitable lenses (14) such as those employed in 35 mm cameras. The optical system is held stationary while a self-scanning linear array (34), comprised of a row of light-sensitive devices, is moved a measured distance in the image plane. The linear array is continuously clocked as it is moved along the image plane. The resulting video signal output is a train of pulses, each proportional in magnitude to the light intensity falling on the corresponding light-sensitive device. An internal line-filament light source moves in synchronism with the linear array so that only the image slice being viewed by the array at any instant of time as it traverses the image field is being illuminated. The light source is directed onto the object plane through a beam splitter so that the light shines through the optical axis of the lens for maximum efficiency.

Surface profiling technique

Abstract: A narrow beam of light (26) is directed at a beamsplitter (12) at an incident angle (θ) thereto. A portion (28) of the beam (26) passes through the beamsplitter (12) and is reflected from a first mirror (22) while a portion (29) of the beam (26) is reflected from the beamsplitter (12) and directed onto and reflected by a second mirror (24). The beams (28, 29) reflected from the first and second mirrors (22, 24) intersect at a reference plane (R). The incident angle θ of the light beam (26) is then varied until the reflected beams intersect on the surface of an object (32) along the plane of symmetry of the system. The known variation of the incident angle, Δθ, provides sufficient information to determine the distance of the surface of the object (32) from the reference plane (R). The object 32 is then moved in an incremental fashion and Δθ determined for each step to ascertain the surface profile of the object.

Output coupler for laser resonator

Abstract: A laser output coupler utilizes a birefrigent lens which has one side thereof curved so as to present a non-uniform polarization distribution across the face of the lens. A polarized beam splitter is employed to separate the output beam from the feedback beam; the feedback beam having a non uniform distribution across the laser aperture enhances mode discrimination of a pulsed resonator.

Twoowavelength laser surface treating apparatus

Abstract: PURPOSE:To execute treatment of multilayer and highly complicate surface by imparting a delay longer than at least pulse time of an optical pulse to the space between a fundamental optical pulse and harmonic optical pulse. CONSTITUTION:The fundamental optical pulse output of a Q-switch solid laser 1 is divided by a beam splitter BS1 to be supplied to an optical frequency harmonic multiplier 2 and an optical pulse delay variable optical system 3. The harmonic multiplier 2 converts incident pulse into harmonic pulse to produce its ouput. The delay optical system 3 delays the propagating time of the fundamental optical pulse by a value longer than the time duration of the optical pulse at least to products its output. The outputs from the harmonic multiplier 2 and the delay optical system 3 are synthesized by the beam splitter BS2, and are irradiated through a collimating optical system 4 to a material 5 to be irradiated. In this manner there can be obtained a two-wavelength laser surface treating apparatus which can treat multilayer and highly complicate surface in various surface treating capabilities.

Optical apparatus and method for reproducing information recorded in a magnetic recording medium

Abstract: An optical apparatus to reproduce information recorded by a magnetic recording medium in utilization of the interaction between light and magnetism, the apparatus being constructed with a light source to supply a light beam for reproduction; a polarizing beam splitter, the transmission and reflection factors of which are dependent on the polarizing direction of the light beam, and which leads the light beam for reproduction from the light source to the magnetic recording medium, and, in interaction with the magnetism in the magnetic recording medium, receives again the emitting light beam for reproduction to lead it to a direction different from the direction of the light source; and a rotatory polarizing device disposed in a light path of the light beam for reproduction between the polarizing beam splitter and the magnetic recording medium, and to rotate the polarized plane of the light beam for reproduction.