Showing papers on "Beam splitter published in 1980"

Fiber‐optic gyroscope with [3×3] directional coupler

Abstract: It is proposed and experimentally demonstrated that a fiber‐optic gyroscope using a [3×3] evanescent field‐directional coupler as a beam splitter operates automatically at quadrature without the 1/2 π phase bias required by conventional gyroscopes with [2×2] beam splitters.

Electrically controlled optical switch for multimode fiber applications

Abstract: An electrically controlled optical switch based on polarization principles is described. It uses a liquid crystal twist cell that rotates polarization by 90°, and it operates on an ac voltage that switches between 0.8 and 2.5 V rms. The switch has a loss of ~0.4 dB, neglecting reflections, in an unpolarized incoherent beam and a cross-talk ratio of ~−20 dB. It operates in collimated light, but it can be applied to multimode fibers using collimating lenses, which are expected to add <0.8 dB to the loss.

Optical fiber beam splitter couplers employing coatings with dichroic properties

Abstract: A single fiber of any glass type is cut at a suitable angle and both halves are then polished at the end surfaces. A layer of material having dichroic properties or multiple layers are then deposited on one coupler half and the two halves are rejoinded with the angular faces in alignment. Each of the cut fibers are supported in a potting compound. A third fiber is added relatively transverse to the original fibers in order to receive light from the deposited layer. This fiber is associated with one port, while the other fibers are associated with two other ports, thus providing a three port coupler device.

An optical TE‐TM mode splitter using a LiNbO3 branching waveguide

Abstract: A novel optical TE‐TM mode splitter using a Ti‐diffused branching waveguide in Y‐cut LiNbO3 is proposed and demonstrated. Mode splitting has been confirmed experimentally at an applied voltage V0=−20 V.

Improvements in birefringent filters. 6: Analog birefringent elements

Abstract: A 100-mA analog birefringent element has been built from a polarizing wide field solid Michelson interferometer. The analog element behaves on-axis identically to a crystal element but has the field characteristics of a wide field Michelson. It is demonstrated that by proper choice of glasses for the arms of the Michelson the wide field condition can hold over a large spectral and large temperature range. Most important, proper choice of arm materials allows minimization of the wavelength sensitivity to temperature. A reduction of a factor of 10(2)-10(3) compared to birefringent crystals can be achieved.

Field test unit for windscreen optical evaluation

Abstract: An apparatus for analyzing the deleterious characteristics of optically transparent bodies, including distortion, multiple imaging and birefringence. A beam of light is projected along an optical axis onto a beam splitter. The reflected segment passes through the transparent body and is then reflected back along nearly the same path toward the beam splitter by a retro-reflective screen lying at the image plane of the beam. The portion of the reflected beam passing directly through the beam splitter is detected by an optical sensor in substantial orientation with the axis of the beam reaching it. Distortions and multiple imaging are detected by shape changes and images, respectively, in a pattern of opaque areas superimposed on the originating beam. Birefringence is analyzed by polarizing the originating beam and observing the color pattern and intensity reaching the sensor.

Theory of Crossed Gratings

Abstract: In this chapter we will consider the theoretical analysis and the properties of doubly periodic diffraction gratings (“bigratings”). Our interest in these structures has been stimulated by two factors. Firstly, their theoretical study represents a natural extension of previous work on mono-periodic structures. Secondly, HORWITZ [7.1] suggested the use of metallic grids as selective filters (heat mirrors) in solar energy absorption. Of course such devices have application in far infrared spectroscopy as beam splitters [7.2], filters [7.3–5] and the reflecting elements in Fabry-Perot interferometers [7.5–10]. Similar applications exist in the field of microwave engineering [7.11.13].

A spectrum scanning Stokes polarimeter.

Abstract: A photoelectric polarimeter for measuring line profiles in all four Stokes parameters has been built and operates on the SPO 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 coronagraph. 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 7000 A with a spectral resolution of 0.01 A. Polarizations as small as 0.001% are detectable. The polarimeter and observing system are computer controlled.

Method and arrangement for the measurement of rotations

Abstract: In order to measure the rotation rate of a rotating light path by the Sag effect, a pair of phase modulated coherent light beams are passed in opposite directions along the light path. After the beams have emerged from respective ends of the light path, the intensity of one of them is detected as a measurement of the phase shift which occurs between the beams along the light path. The detected output is then passed through a synchronous rectifier to produce an error signal for a control loop for the system. In a preferred embodiment, the control loop is formed by a solenoid wound around a portion of an optical fiber located along said light path. By processing the current through the solenoid, a continuous update of a scale factor for the phase shift can be achieved. Also, interference with the phase shift in the rotating object is prevented by the structural interconnection between an input/output branching device and a beam splitter for the system utilizing the combination of a monomode wave guide and a polarizer.

Fiber-optic rotation sensor technology

Abstract: A concept for an all-waveguide fiber-optic rotation sensor is discussed, and the results of preliminary tests of key elements are described. A single channel waveguide coupler design provides the functions of an optical switch, a 3-dB beam splitter, a phase retarder, and a signal modulator, all of which may be formed on the same chip and interconnected by channel single-mode waveguides. Preliminary test results for the waveguide coupler and for a rotation sensor without the coupler are presented. Signal processing, polarization control, and interconnection of the waveguide components are discussed.

Refractively scanned interferometer

Abstract: An interference spectrometer in which a wedge-shaped prism (32) is moved across one arm (22) of an interferometer for variation of the path difference, and where the beam splitter substrate (36) and prism (32) are optically compensated for by elements substantially identical to the substrate and prism (38, 40) in the other arm of the interferometer. In a first embodiment two refractive elements are in each arm of the interferometer (40, 36, 38, 32). In the preferred embodiment, only one prism is used in each arm, (46, 44) with the beam splitter surface (12) being located on a fixed prism (46), in one arm, adjacent a movable prism (44) in the other arm.

Collimated beam manifold with the number of output beams variable at a given output angle

Abstract: An optical manifold transforms a collimated beam, such as a laser beam, into a plurality of parallel beams having uniform intensity or having a desired intensity ratio. The manifold (10) comprises an optical substrate (12) coated on its rear surface (13) with a fully reflective layer (14) and on its front surface (15) with a partially reflecting layer (20) having a reflectivity gradient. An input collimated beam (30) entering the rear surface (13) and impinging on the front surface (14) will be reflected, multiple (32-40) between the front and rear surfaces producing a plurality of parallel beams (42, 44, 46, 48) that emerge from the front surface. The intensities of the emerging beams will have a relationship that depends on the reflectivity (R1, R2, R3, R4, and R5) of the front surface at the points where the beams emerge. By properly selecting the reflectivity gradient, the emerging beams will have uniform intensity or a desired intensity ratio.

Interferometer apparatus for microtopography

Abstract: Interferometer apparatus for measuring the microtopography of surfaces in two dimensions (surface roughness) uses monochromatic light from a laser. A beam splitter divides the light and directs a beam to the surface being measured and another beam to a reflector. The phase of the reflected beam is varied linearly by means which applies a saw tooth wave to an electromechanical transducer on which the reflector is mounted. The beam is focused onto a spot on the surface by a lens which is translated along the surface in two dimensions. The beams from the reflector and the surface are recombined by the beam splitter and the interference fringe detected thus producing an alternating current signal. The waveform is tracked during the rising portion of the waveform and sampled and held during the retrace portion of the saw tooth. Finally, the resulting waveform is filtered to provide an alternating current (AC) output, the phase change of which is a measure of the topography of the surface to a high degree of accuracy, for example, less than one Angstrom (A) vertical resolution and one micron (um) horizontal resolution. The apparatus provides a low cost profile measurement device which is highly accurate.

Retro-reflective electro-optical angle measuring system

Abstract: A scanning angle tracker which includes a laser beam and a beamsplitter for developing two beams which intersect on a scanning mirror. The scanning mirror sweeps the two beams across a retro-reflective tape on the object. Return signals are generated for processing to provide the desired angular information.

Phase-conjugate interferometer

Abstract: A speckle interferometer including a beam splitter, a mirror in the object beam arm, a phase-conjugate mirror in the reference beam arm, a converging lens and a photographic film. Laser light scattered retro-reflectively from a rough surface under investigation and passed through an imaging lens illuminates the interferometer. Fringes occur upon sandwiching a pair of exposures of the interference pattern made before and after deformation of the rough surface. The relative magnitude of the displacements from the original position at different points of the surface can be determined from the position of the fringes.

Method and device for quantitative determination of optically active substances

Abstract: 1. A process for the quantitative determiantion of a dissolved optically active substance in aqueous or non-aqueous solutions by means of polarimetry by splitting the light beam after the sample by means of a beam splitter, thereby producing a measuring beam and a reference beam, and forming a difference or quotient signal of the signals of the measuring and the reference beam detected by corresponding detectors, whereby the polarized light of the light source prior to passing through of the sample is eventually subjected to frequency, phase, or amplitude modulation, and the difference or quotient signal formed of the signals of the measuring and the reference beam is demodulated correspondingly, characterized in that for simultaneously obtaining beam splitting and an analyzing effect the light beam after the sample is directed to an optical interface at an incidence angle (alpha) between the polarization angle and the limit angle of total reflection.

Photolithographic projection apparatus using light in the far ultraviolet

Abstract: A lens design for submicron photolithography images a mask (21) onto a semiconductor wafer (23) using light in the far ultraviolet. Illustratively, the lens design is a modified Dyson imaging system comprising a thick plano-convex lens (31), a beam splitter, adjacent to the planar surface of the plano-convex lens comprising two right angle prisms (34, 35) separated by a dielectric interface (36), and an aspherical mirror (32) located on the convex side of the lens. Stress-induced birefringence is used to rotate the plane of polarization of the object radiation.

Low polarization beam splitter

Abstract: A beam splitter is disclosed which comprises a transparent substrate plate, a first dielectric thin film layer laid on the substrate, a metallic thin film layer laid on the first dielectric layer and a second dielectric thin film layer laid on the metallic layer. At least one of the first and second dielectric layers is composed of a plural number of dielectric substance layers having different refractive indexes. At least one of the dielectric substance layers is of a dielectric substance having a refractive index less than 1.80.

Automatic detector for microscopic dust on large-area, optically unpolished surfaces

Abstract: A system for automatically detecting dust or other minute particles on a large-area, optically unpolished surface such as a face of a glass reticle plate used in the production of microelectronic circuits. The system irradiates the surface with a narrow, high intensity beam of monochromatic radiation at a grazing angle, typically 1/2 degree with respect to the surface. An oscillating mirror scans the beam across the moving surface in a direction generally perpendicular to the direction of plate advance. A beam splitter provides separate inspecting beams for each surface of the plate. Optical systems characterized by a high numerical aperture are positioned on opposite sides of the plate to collect radiation which is scattered from the particles. The optical systems are oriented to accept scattered radiation, and typically have their optical axes at an angle in the range of 60° to 160° measured from the direction of advance. They each utilize a multiplet of cylindrical lenses characterized by excellent resolution and a large numerical aperture, preferably in the range of 0.15 to 0.20. A fiber optic concentrator transmits the scattered radiation from the image plane of the lenses to a detector which generates an electrical signal proportional to the size of the particle. In the preferred form, a comparator circuit with an adjustable threshold level generates a digital signal only when the size of the particle exceeds a predetermined value. Also, the oscillation of the scanning mirror and the advance of the plate provide a timing reference for the particle detection signal to locate the particle on the plate.

Optical modulators and apparatus including such modulators

Abstract: An optical modulator which is capable of passing the greatest intensity of light incident upon it when the light incident upon it is either unpolarized or has a partial or variable state of polarization, comprises a beam splitter (1) to resolve the light beam incident upon it into two plane polarized components having mutually perpendicular polarization states, one or more electro-optic cell or cells (2,18,19,22,23) which is or are arranged to receive both components of the light beam and, in use change the state of polarization of both of the components to a corresponding extent in dependence upon an electrical modulation signal applied to it or them. The optical modulator also includes analyzer means (1,17) arranged to receive the output from the electro-optic cell or cells (2,18,19,22,23) the arrangement being such that the intensity of the light output from the analyzer means (1,17) is a function of the change of the state of polarization generated in both components during their passage through the electro-optic cell or cells (2,18,19,22,23). The beam splitter and the analyzer means may be formed by the same piece of apparatus (1) and in this case the modulator preferably includes a half wave plate in the light path of both components to change their polarization states.

A Novel Polarization-Independent Beam Splitter

Abstract: This paper presents the design and experimental results of a novel broad-band quasi-optical polarization-independent beam splitter. The novel beam splitter consists of parallel metallic strips formed on a dielectric sheet. The width and spacing of the metallic strips and thickness of the dielectric sheet are optimized. This experimentally manufactured 3-dB beam splitter has a frequency bandwidth from 80 to 110 GHz, and the transmission and reflection coefficients for mutually orthogonal polarisation are within 3/spl plusmn/0.5 dB over this entire frequency band. The insertion losses are 0.2 dB over the abovementioned frequency band. The obtained insertion losses are less than that obtained with any other quasi-optical polarisation-independent beam splitter presented in the literature to date. This type of beam splitter holds great promise as a device for constructing signal-multiplexing and demultiplexing circuits in the millimeter-wave region and above.

Focus detector for an optical disc playback system

Abstract: Electro-optical focus detection apparatus for providing a signal indicative of the magnitude and polarity of focus error in a light beam impinging on a surface, such as a recording surface in a recording or playback system. The detector includes a beam splitter for dividing the beam reflected from the recording surface into two reflected beams of equal power, and includes an aperture placed in the path of the two reflected beams. The first reflected beam converges at a focal point before encountering the aperture and the second reflected beam converges at a focal point after encountering the aperture, both beams thereafter impinging upon separate photodetector elements. The aperture reduces the light incident on the photodetectors from both reflected beams, and the apparatus is so configured that the powers of the reflected beams incident on the photodetector elements are identical when the original beam is in focus on the recording surface. When the original beam moves out of focus with the recording surface, both focal points of the reflected beams move in the same direction, to provide an increase in the light falling on one of the photodetector elements and a decrease in light falling on the other, such that the differential output derived from the photodetector elements provides a signal indicative of the magnitude and polarity of the focus error.

Wavelength multiplexer-demultiplexer

Abstract: A multiwavelength multiplexer-demultiplexer constructed from units each cble of multiplexing or demultiplexing two wavelengths. As many such units as required can be interconnected to form multiplexer-demultiplexers of any number of wavelengths. Each two-wavelength multiplexer-demultiplexer unit includes a four-port power divider, a four-port phase shifter having two ports connected to two ports of the power divider, and another four-port power divider having two ports connected to two ports of the phase shifter. The power divider may be a single-mode optical fiber directional coupler, or a half-silvered mirror beam splitter. The phase shifter may include a pair of single mode optical fibers or a pair of oppositely disposed mirrors.

Fiber dichroic coupler

Abstract: An assembly for a bidirectional wavelength dependent beam splitter is disclosed together with a method of fabricating a thin film dichroic element. A dichroic material is applied to the surface of a suitable substrate. The substrate with this applied coating is then immersed in a solvent bath such that the dichroic thin film is either lifted off the substrate or the substrate is dissolved in the solvent bath, thus leaving an extremely thin film comprising the dichroic coating. The dichroic coating is positioned over the end face of a polished fiber beam splitter half and secured thereto by a thin layer of an optical grade epoxy. In the beam splitter configuration, a second polished fiber is secured in a similar manner to the opposite side of the thin film to form a beam splitter structure and hence, to provide a bidirectional wavelength dependent optical coupling device.

Dual-input fiber-optic gyroscope

Abstract: A fiber-optic gyroscope is operated at maximum sensitivity by supplying two equal-intensity inputs with a specific phase difference to the gyroscope beam splitter. When the beam-splitter outputs have equal intensity, reciprocity requires the Sagnac interferometer to be at quadrature. A sensitivity of ∼0.93 rad−1 is demonstrated with a minimum-detectable rotation rate of 0.4 deg/sec.

Wide angle display device

Abstract: In order to widen the field-of-view, two display devices are abutted. A first display device has a concave mirror (10), a 45° beam splitter (12) and a CRT positioned on an axis (16). To minimize any gap tending to develop between adjacent images, a second display device is rotated 90° about its viewing axis (24), the second display device having a concave mirror (20), a beam splitter (22) and a CRT (21). The CRT axis (26) is tilted towards the mirror (20) to provide image continuity where the devices abut, so that eye movement within a range to an observer's right of the center of curvature (18) is possible without any gap developing between two displayed images. In a modification, the mirror (20) has a larger radius of curvature and overlaps the mirror (10). In an alternative arrangement, there is no 90° rotation of the second display device, but the CRT axes are tilted towards each other.

Minimum resolvable contrast measurement device

Abstract: An apparatus for creating images of nonperiodic patterns, which patterns are variable in contrast with respect to a uniform and constant level of background luminance. Two beams of uniform luminance are projected through individual, orthogonally oriented linear polarizers, and then into a common cube beam splitter to be divided and interlaced. One combined output beam from the splitter is projected through a rotatable linear polarizer onto the image sensing optical detector undergoing test. The second beam is projected toward a detection system. The patterned region of the second beam passes through a second rotatable linear polarizer, synchronized to the first rotatable polarizer, and onto a CCD array detector system. Contrast between the pattern and the background is represented by the two electrical voltage levels in the array output, irrespective of the spatial frequencies in the pattern. Two unpatterned background regions from either of the interlaced beams are projected through individual and orthogonal linears polarizers to individual luminance detectors. Each detector, in turn, regulates its corresponding beam intensity to compensate for drift in the beam generating elements.

Apparatus for determining the refractive-index profile of optical fibers

Abstract: Light from a laser, converted into pulses by a chopper, is trained upon an end of an optical fiber--whose refractive-index profile is to be determined--through a first polarizer, a beam splitter, a focusing objective and a 90° phase shifter, the space between the objective and the fiber end being occupied by a fluid whose refractive index is close to that of the fiber. Light reflected from the fiber end, having passed twice through the phase shifter, has a plane of polarization orthogonal to that of the incident light and is passed by a second polarizer, to which it is directed by the beam splitter, onto a photodiode feeding a calculator that also receives a reference signal from another photodiode to which part of the polarized laser pulses are directly reflected by the beam splitter. Spurious reflections from the objective surface, which do not pass through the phase shifter, retain the original polarization and are rejected by the second polarizer.

Holography photographing unit

Abstract: PURPOSE:To improve the limit of amplitude which can be measured by holography by roughening intervals of stripes appearing on a produced picture, by making a reference beam interfere with a reflected beam obtained by irradiating a doby with body beams differing in incident angle. CONSTITUTION:Laser beam 2 emitted by laser unit 1 is passed through shutter 3 and then by split by beam splitter 4 into reference beam 6 and body beam 5, which is further separated into body beams 15 and 16 through half mirror 7 and mirror 8. Respective body beams 15 and 16, after passing through spatial filters 9 and 10, light up body 12 to be amplitude-analyzed. Reference beam 6, on the other hand, is reflected by mirror 14 and then interferes on hologram dry plate 11 with reflected beams of body beams 15 and 16 from the body. In this case, the body irradiation angle of each body beam differs according to positions of spatial filters 9 and 10.

Dynamic binary fourier filtered imaging system

Abstract: An apparatus for altering the spatial frequency content of recorded patterns by selectively filtering the patterns after they are transformed into the Fourier domain The filter characteristics are spatially and temporally variable while the real space image of the altered pattern is being observed A laser beam is projected through a transparency containing the pattern The patterned beam, with diffraction interference effects, is transformed to the Fourier domain at the surface of a liquid crystal light valve responsive to a spatially and temporally varying light projector The projector activated regions reflect areas of the Fourier domain beam, while other areas are absorbed or incoherently reflected A beam splitter redirects a portion of the reflected beam to a continuously observable image plane after transformation back into real space