Showing papers on "Beam splitter published in 1971"

Shearing interferometer using the grating as the beam splitter.

Abstract: The theoretical interpretation of the shearing interferometer based on the moire method using the fourier image of the grating is described. To obtain a pattern with good contrast, the observing plane must coincide with the normal fourier image plane of the grating or with the reversed fourier image plane. The information obtained by this method is the first partial derivative and under certain conditions the second partial derivative of the distortion from the reference wavefront, which is planar or spherical. Applications to measurement of the phase gradient and lens aberration are shown.

Laser system for microsurgery

Abstract: A beam of infrared energy from a CO2 laser operating in its lowest order spatial mode is passed through a converging lens and directed to an operating site by a mirror or beam splitter. In order to locate the invisible focused spot of infrared energy a beam of visible light from a He-Ne laser is introduced coaxially into the path of the CO2 laser beam by a removable mirror. In another embodiment the He-Ne beam is passed through a beam splitter to form two parallel channels focused by microscope objectives on the input ends of respective fiber optic light guides. A rotating chopper disc is positioned in front of the light guides to alternately block and pass light in each channel. The other ends of the light guides are connected to marker projectors located above the beam splitter for the CO2 beam, but just out of the field of view of an overhead operating microscope. A lens and mirror system in each projector focuses the visible light through the beam splitter onto the focal point of the CO2 beam at the operating site. If the intended site is above or below the CO2 beam focal point, spaced red dots alternating at the frequency of the chopper disc will appear to the viewer through the microscope, indicating the need for further adjustment. Perfect adjustment is indicated by a single non-flashing dot.

Jones's Matrix Representation of Optical Instruments. I: Beam Splitters.

Abstract: A general method is provided for constructing Jones’s reflection and transmission matrices of any beam splitter. Derivations are presented for the various known configurations. The method uses Abeles’s matrices and pays special consideration to the different expressions of Jones’s matrices relative to the various beams in an interferometric arrangement. The reversibility of the beam splitter in its action on the amplitude or phase, or both, of an incident light is studied. It is finally suggested that, even for an asymmetric beam splitter configuration, the symmetry of the interferogram can still be preserved by adjusting the thickness of the beam splitter in a prescribed manner.

Shearing interferometer using the grating as the beam splitter. Part 2.

Abstract: In the previous paper, a Ronchi-type shearing interferometer was proposed, and the theoretical interpretation of the interferom­ eter and several experimental results were given. In this method, the distance between the grating and the observing plane (z = zp) is chosen so that a fourier image of the grating is formed in the observing plane and the distortion of the fourier image given by a phase object is detected by the moiré method. ' The optical ar­ rangement for this method is shown in Fig. 1. The purpose of

Optical device for determining the position of a point on a surface

Abstract: The optical device comprises a luminous source and an optical system for forming a primary image of the source on the surface whose position is to be determined. The optical system returns some of the light back from the primary image. A beam splitter is provided for splitting the returning light into two beams directed towards two secondary image points. Two optical elements are disposed respectively in these two beams, each optical element controlling the amount of light passing therethrough, and two photoelectric detectors are provided respectively behind the two optical elements to receive the light passing through. Preferably one of the optical elements is a field lens having a central screen, and the other optical element is a diaphragm having a central aperture of the same diameter as the screen. Alternatively both the optical elements can be constituted by field lenses each having a central screen.

Apparatus for determining a substance by an optical radiation

Abstract: A laser produces a beam of optical radiation. The substance to be determined may be CO2, and in this case the laser is a CO2laser. Alternatively, the laser may be a tunable laser, and the beam is split by a beam splitter into sample and reference beams, the sample beam being relatively modified by said substance. The modified beam and the reference beam are united and the united beam is sensed by a detector. The optical lengths of the paths transversed by the reference and sample beams are exactly the same save the influence of said substance. A preferred sensing system indicates both the phase shift and attenuation of the sample beam by the substance to be determined.

Spectrophotometer utilizing memory storage calibration techniques

Abstract: A spectrophotometer having no moving parts in the monochromator or the optical beam paths through the reference material and the sample material is disclosed. A preferred form of monochromator utilized is an acousto-optical filter tuned over the desired spectrum electronically by variation of the radio frequency producing the acoustical wave in the filter. A single beam spectrophotometer employs a memory device for storing the detected transmitted optical radiation in a first calibration run with the sample absent from the path, a divider circuit producing a ratio signal output responsive to one input comprising the detected transmitted optical radiation in a second measurement run with the sample in place and a second input comprising the absorption signal stored in the memory. A double beam spectrophotometer utilizes an optical beam splitter to split the radiation into two separate paths, one path extending through a reference material and the other path through the sample, the transmitted light detected in the two paths being transmitted to a divider circuit to produce an output dependent on the ratio of the two detected radiation beams. A calibration run with reference and sample absent may be made and stored in a memory, followed by a measurement run with reference and sample in place, and the two output ratios then compared to give a final ratio signal output. In a further embodiment, two optical sources and two associated monochromators are provided, the radiation from each being directed through the beam splitter into the two separate reference and sample paths to the detector circuitry.

Holographic system forming images in real time by use of non-coherent visible light reconstruction

Abstract: A holographic system is described for forming visible images in real time using holograms sensed with microwave or acoustic waves. Coherent waves are received together with a coherent reference wave at a set of detectors in an antenna array to develop an interference fringe pattern. A visible luminous display of the fringes is produced on a reduced scale by light bulbs driven by the detectors; the light bulbs producing monochromatic, spatially non-coherent visible light. The light from the bulbs is passed through a beam splitter with a portion going through an inverting prism so as to produce an axially symmetric pair of the fringe patterns. A lens delivers the Fourier transform of the double fringes in its focal plane so as to produce a transform which provides the image.

Laser polarizing beam splitter

Abstract: The beam splitter comprises first and second prisms having diagonal surfaces placed together in juxtaposed relationship with means on the opposing edge portions of the surfaces holding the surfaces in spaced relationship to define a thin chamber therebetween. A fluorinated hydro-carbon liquid fills this chamber and one diagonal surface is provided with a multi-layered di-electric coating. High reflectance is provided for the S component of a laser beam and high transmittance for the P component for both ruby and neodymium laser wave lengths of 0.694 and 1.06 microns respectively. The use of the liquid interface avoids the necessity of cement or glue to hold the prisms together so that the beam splitter may be used with high power laser beams without the risk of deterioration.

Variable amplitude polarizing beam splitter

Abstract: A birefringence polarizer divides incident light into two emergent, mutually perpendicularly polarized beams. The incident light is linearly polarized, its azimuth of polarization being rotatable by a rotatable half-wave retardation plate. A similar plate in the path of one of the emergent beams controls its azimuth of polarization. The emergent light beams are thus controllable as to relative intensity and directions of polarization.

Rapid scan identifier for use in infrared absorption spectroscopy

Abstract: A rapid scan spectrum identifier fur use in identifying infrared spectrum of the output of a gas chromatograph to identify its absorption characteristics and includes an infrared source and beam splitter, a double beam chopper for alternately sending the infrared beam through a sample or reference gas cell mounted in a suitable furnace, the output of which is recombined and analyzed by a monochromator having a narrow output passband of energy detected by a rapid response detector, the output of which is processed by suitable electronic circuitry to provide a readout. The monochromator is of the scanning type in which a grating is synchronously scanned with a circular variable filter so that the first order output of the grating is selectively passed and higher orders rejected by the filter. The sample and reference gas cell furnace assembly utilizes specially constructed sample and reference gas cells symmetrically mounted in a furnace arrangement for maintaining input gas streams at equal temperatures within each cell and above the temperature of condensation of the sample under investigation. The beam chopper contains associated photoelectronics for physically determining the location of a chopping blade to thereby provide gating signals for indicating the presence at the detector of a sample, reference, or a background signals. These grating signals are used in sample and hold circuits to convert an essentially digitally sampled output into a relatively smooth continuous curve indicative of the absorption of the sample so that the readout represents the sample absorption characteristics corrected for reference for the carrier gas and background effects. The instrument is designed to operate with scan rates of approximately 6 and 30 seconds.

Jones's Matrix Representation of Optical Instruments. 2: Fourier Interferometers (Spectrometers and Spectropolarimeters).

Abstract: Our method of matrix synthesis of optical components and instruments is applied to the derivation of Jones's matrices appropriate for Fourier interferometers (spectrometers and spectropolarimeters). These matrices are obtained for both the source beam and the detector beam. In the course of synthesis, Jones's matrices of the various reflectors (plane mirrors; retroreflectors: roofed mirror, trihedral and prism cube corner, cat's eye) used by these interferometers are also obtained.

Electro-optical measuring apparatus

Abstract: An electro-optical measuring apparatus includes a magneto-optical element around which is wound an electrical conductor carrying a current to be measured The plane of polarization of a linearly polarized light beam in passing through the magneto-optical element is rotated by an amount which varies with the magnitude of the current, the beam is then passed through a beam splitter to establish two beam components which are then shifted in phase to establish a phase quadrature relationship, and these phase-shifted beam components are then passed to evaluating circuits for comparison These evaluating circuits include an arrangement wherein any variations in the values of certain constants in the circuits are compensated out thus to improve the accuracy of the measurements

Optical intensity matching means for two light beams

Abstract: A partially-reflecting surface of a beam splitter is made of a dielectric reflecting coating which at large incident angles of light is quite sensitive to the direction of polarization of the incident light. Thus two beams divided by the beam splitter and selectively directed to a common point, in parallel directions, etc., may be matched in intensity by placing a half-wave plate in the entrant beam and rotating same to change the polarization direction to alter the proportion of light that is transmitted and/or reflected by the beam splitter.

Split-field microscope

Abstract: The split-field microscope of the present invention has a polarizer in the illuminator, a polarizing beam splitter for simultaneous or alternative illumination of both object fields, equal optical path lengths for the polarized split partial beams between splitting and reunion, means for deflecting the polarized partial beams in the direction toward parallel-disposed objectives and a quarter-wave plate disposed in each illuminating beam path. The imaging ray beams are passed backwards through the aforementioned components up to the central prism and a tube lens system and an ocular, connected after the central prism, are transited by the combined imaging beams.

Interferometric rotation sensor

Abstract: An interferometric rotation sensor and control system is provided which includes a compound prism interferometer and an associated direction control system. Light entering the interferometer is split into two paths with the light in the respective paths being reflected an unequal number of times and then being recombined at an exit aperture in phase differing relationship. Incoming light deviating from the optical axis of the device by an angle alpha causes a similar displacement of the two component images at the exit aperture with the result being that a fringe pattern is developed with the number of fringes being directly related to the angle alpha . Various control systems incorporating the interferometer are also disclosed.

Apparatus for optical investigations and measurements with the aid of several coherent light beams

Abstract: In an apparatus for optical investigations and measurements in which a laser and a beam splitter produce coherent beams of monochromatic light, the beam splitter is a hologram that is a photographic reproduction of the intersection of corresponding coherent beams of monochromatic light. The superposition of a plurality of such holograms in different positions results in a multiple beam splitter that provides a plurality of coherent beams. These beams are used for the three-dimensional determination of the speed of a moving effluvium and for the elimination of noise in the output signals.

Device for gas analysis with a rotatable cylindrically shaped chopper

Abstract: A device for gas analysis by measurement of absorption of electromagnetic, especially optic, radiation comprises a radiation source emitting a beam of electromagnetic radiation which is splitted by a beam splitter into a sensing beam and a reference beam passing through a sensing chamber and a reference chamber, respectively to radiation sensitive means responding to the difference in intensity of the sensing and reference rays and providing a corresponding electric output signal. A rotary shutter is arranged between the radiation source and the beam splitter to chop up the emitted beam before it enters into the beam splitter. The rotary shutter or chopper comprises preferably strip-shaped elements which form parts of a cylinder, the elements having edges parallel to the axis of the cylinder and rotating around the axis of the cylinder in a circular path which includes or encompasses the radiation source.

Rear view optical system

Abstract: A rear view optical system adaptable to a vehicle having a top wall provided with an opening therein. A first mirror is supported above the opening and is adapted to direct the image downwardly to a one-way or beam splitter mirror which in turn directs the image forwardly to a second mirror. The second mirror in turn redirects the image through the one-way mirror rearwardly to the eyes of the observer in the vehicle.

Balanced Detection for the Dual Scatter Laser Doppler Velocimeter

Abstract: : Single particles traversing the region of interest produce both a DC term and an AC term as seen by a photomultiplier. The AC term is directly proportional to the particle velocity. In order to accurately determine the frequency of this burst of information, the DC term is rejected by electronic filtering technique. At higher particle velocities the DC rejection becomes difficult, if not impossible, and an alternate technique is necessary. This report describes a balanced detection method to reject the DC term optically without electronic filters. Balanced detection rotates one of the laser beams in a dual scatter laser Doppler velocimeter such that light scattering from the probe volume has the two scattering components 90 degrees apart. A polarization- sensitive beam splitter is employed to split the scattered light into two components with one beam undergoing a 90-degree phase shift. Two photomultipliers are used to detect each signal.

Manufacturing an optical shaft encoder having a holagraphic code disk

Abstract: A constant laser beam is directed toward a photosensitive code disk A beam splitter diverts some light from the laser beam to drive first inputs of light modulators The shaft of a standard reference shaft encoder is concentrically fixed to the disk and the encoder output bit lines are individually connected to second inputs of respective light modulators for selectively modulating the passage of light thereby generating light bit equivalents The light bits are individually transmitted through fiber optics to projecting positions near the opposite side of the disk By subjecting the disk to constant laser light on one side and changing bit light on the other side as the shaft turns, a diffraction grating is formed on the disk as a latent image The photosensitive disk is developed and forms a permanent optical encoder disk for future use

Freestanding polarizers for submillimeter interferometry.

Abstract: Michelson interferometers for spectroscopy in the extreme infrared and submillimeter wavelength range have been described by Gebbie, and their applications have since been discussed by many other workers. More recently Martin and Puplett have discussed the advantages of using polarizing beam splitters in such interferometers. There are severe difficulties with conventional thin film dielectric or lamellar beam splitters, if spectra over several octaves are to be obtained, starting in the low-frequency, millimeter wavelength region. The efficiencies of these vary with frequency (i.e., hooping), as best illustrated by reference to Fig. 3 of the article by Richards. These variations need not arise if a polarizing film is used as the beam splitter necessitating also the use of similar films as polarizer and analyzer. The purpose of this Letter is to describe a technique for manufacturing the polarizing film which allows the most compact and elegant optical configurations for polarizing interferometers. Polarizers comprising wiregrids can have reflection and transmission coefficients close to 100% for their respective planes of polarization, from frequencies close to zero, up to 1/(2d) c m 1 where 1/d is the spatial frequency of the wires. Grids for this purpose deposited on dielectric substrates, e.g., polyethylene and Mylar (Melinex), can be obtained with a maximum spatial frequency of 500 cm 1 . The film of dielectric substrate would give rise to hooping, however, unless a configuration such as tha t in Fig. 1 is adopted, in which each of the plane polarized beams is given the same pathlength in dielectric. This provides a working interferometer without hooping but with two drawbacks: the reflection and absorption losses in the dielectric films, and the noncompactness of the expanded beam splitter. A method of producing freestanding wire grids which we have found easy to employ, and which gives excellent polarizing film,

Q-switched lasers

Abstract: 1,248,405. Lasers. DEFENCE, SECRETARY OF. 30 Oct., 1969 [4 Nov., 1968], No. 52188/68. Heading H1C. Laser Q-switching is effected by periodically varying the optical spacing between the plates of a Fabry Perot etalon forming one of the resonator mirrors. As shown in Fig. 1, a neodymium-doped yttrium aluminium garnet laser rod 1 is located in a resonator comprising a dielectric mirror 3 and a Fabry Perot etalon 6 formed by dielectric mirrors 7a, 7b, the optical spacing of the etalon being determined by a hollow piezo-electric cylindrical transducer 9. The optical spacing is varied periodically by a pulse generator 27 and the mean spacing is determined by a D.C. bias from an amplifier 25. This bias is adjusted to maintain the etalon optical spacing constant by superimposing a 70 Hz. modulation from an oscillator 23, the modulated laser output being detected by using a beam splitter 13 and a photo-diode 15 so as to produce a feedback signal which passes through a pulse stretcher 17 and a tuned amplifier 19 to a phase-sensitive detector 21. If the phase of the feedback signal differs from that of the oscillator 23, the detector 21 adjusts the D.C. bias to a compensating level. A modified laser is described, Fig. 2, in which two Fabry Perot etalons are used, one etalon 33 having a fixed optical spacing and being located within the resonator, while the other etalon 35 functions as a variable resonator mirror and consists of dielectric mirrors 37a, 37b on flats 34, 36 adjustably spaced by a transducer 41. Etalon 33 is inclined with respect to the optical axis to reflect light of certain frequencies out of the system which might otherwise give rise to laser action at those times when etalon 35 is non- reflective. The combination of two etalons 33, 35 effects laser action by the change of optical spacing of one etalon relative to the other, a laser pulse being produced each time a spacing relationship is obtained in which etalon 33 is transmissive and etalon 35 reflective. Continuous pumping may be used. Instead of altering the physical distance between etalon mirrors, the optical spacing may be varied by change of refractive index using the electrooptic effect.

Laser heterodyne communication system

Abstract: 1,234,997. Lasers. HUGHES AIRCRAFT CO. 31 Oct., 1968 [1 Nov., 1967], No. 51645/68. Heading H1C. An infra-red laser communication system comprises two similar transmitter-receiver laser devices tuned to slightly different frequencies, each of which may be as shown in Fig. 1, both devices generating an output beam simultaneously which is directed at the other device, with the beam of the device then transmitting being modulated by an information signal, the two beams-local and distant-at each device being combined by a beam splitter 14 and applied to a respective photo-electric detector 16 for subsequent demodulation. Beam modulation of the device then transmitting is effected by an electro-optic crystal 30 located between the laser resonator mirrors 12, 13, as shown, by a capacitor transducer having one electrode serving as a resonator mirror, Fig. 1b (not shown), or by a piezo-electro transducer controlling the resonator length, these arrangements producing frequency modulation. For amplituce modulation an electro-optic crystal is positioned outside the resonator and in the path of the incoming and outgoing beams, Fig. 1c (not shown). The output of the photoelectric detector 16 is amplified at 20 and is demodulated by an f.m. limiter discriminator 24 for frequency modulation, or by an a.m. detector (23), Fig. 1c (not shown), for amplitude modulation, the resulting demodulated signal being applied to a "signal out" terminal. In addition, automatic frequency control of the beam generated by the device is obtained by applying the demodulated signal through a low-pass filter 26 and amplifier 28 to either a piezo-electric crystal 31 controlling the axial position of mirror 12 or to the capacitor transducer, Fig. 1b (not shown). The beams may be generated by an He-Ne or CO 2 active medium 11 and are transmitted and received through a telescope 32. In a modification, Fig. 2, the resonator is formed by three mirrors 212, 213, 214, the intermediate one 214 of which is partially transmitting and serves as the beamsplitter. In a further modification, Fig. 3, the incoming and outgoing beams 40, 38 are transmitted along different parallel paths and are combined in the beam-splitter by mirrors 36, 42. A single path and a plurality of beamsplitters are used in Fig. 4, the outgoing beam 50 having a portion 60 deflected by a beamsplitter 414a and the incoming beam 54 having a portion 56 deflected by a beam-splitter 414b, the two portions being combined in a beam-splitter by a mirror 48.

Off-axis alignment device

Abstract: A device for making a surface parallel with and centered on a fixed reference surface without the necessity of placing an alignment scope on the axis between the two surfaces. A beam splitter is supported by parallel bars from the base of the device. These bars position the beam splitter at a preset angular setting with respect to an alignment mirror of the device. In case the beam splitter is inadvertently moved the support bars will control the repositioning of the beam splitter through a torsion and/or cantilever movement.

Television signal to photographic film recording system

Abstract: An apparatus and method for recording television scenes onto photographic film in a format suitable for use in conventional optical motion picture projectors. A beam splitter is used to simultaneously record the scanning spots of a TV signal onto two adjacent frames of an intermediate, continuously running film such that two fully interlaced TV fields are recorded on every frame of the intermediate film. Selected frames from the intermediate film are then printed onto conventional photographic motion picture film in a format which can then be used in conventional optical motion picture projectors.