Showing papers on "Beam splitter published in 1969"

Thin-film optical filters

Abstract: Introduction. Basic theory. Antireflection coating. Neutral mirrors and beam splitters. Multilayer high-reflectance coatings. Edge filters. Band-pass filters. Tilted coatings. Production methods and thin-film materials. Factors affecting layer and coating properties. Layer uniformity and thickness monitoring. Specification of filters and environmental effects. System considerations: applications of filters and coatings. Other topics. Characteristics of thin-film dielectric materials.

Some applications of thin films to polarization devices.

Abstract: In the first application of thin films discussed, a multilayer stack is enclosed in a cemented cube to form a polarizing beam splitter. Polarizing efficiencies exceeding 99.8% have been achieved in both reflected and transmitted beams at the design wavelength. In the second application, the deposition of thin films on the totally reflecting surfaces of silica phase retarding systems has resulted in a substantial improvement in achromatism of these devices. Measured phase retardations of one of the two devices described were within 0.5° of 90° over the visible and uv to wavelengths down to 200 nm.

Investigation of low power laser signals with picosecond resolution

Abstract: A device is described that employs second harmonic generation to analyze the output from low‐power lasers. It consists of a calcite beam splitter and a KDP second‐harmonic generator. Its high sensitivity and resolution are demonstrated by investigating the output from several free‐running cw GaAs lasers.

Holographic optical polarizers and beam splitters

Abstract: Holographic optical components such as polarizers and beam splitters are made by the interference of a pair of coherent light beams polarized at 90* to their plane of incidence on a transparent thick holographic medium, and intersecting each other at 90* within the medium.

A double beam interferometer for the middle infrared.

Abstract: A versatile, double beam Michelson interferometer for the middle ir has been constructed. The moving mirror operates in a constant velocity mode. In contrast to instruments of a similar nature, the same area of the beam splitter is used for separation and recombination of all interacting beams, but the beams occupy different parts of the permissible solid angle. Calibration and ratio recording techniques were applied to atmospheric emission spectra shown between 750 cm(-1) and 1250 cm(-1) with a resolution better than one wavenumber.

Optical frequency waveguide and transmission system

Abstract: A METHOD AND SYSTEM OF TRANSMITTING AND DISTRIBUTING OPTICAL FREQUENCY RADIATION ARE DISCLOSED. THE POWER LEVEL OF THE RADIATION BEAM IS MAINTAINED AT A LEVEL WHICH IS A FUNCTION OF THE PRESSURE AND DIELECTRIC CONSTANT OF A GAS THROUGH WHICH THE BEAM IS TRANSMITTED. THE BEAM THROUGH THE GAS GENERATES ITS OWN WAVEGUIDE TO PREVENT BEAM DIVERGENCE THROUGH THE GAS.

Variable reference phase holocamera to compensate for object motion

Abstract: A variable reference phased holographic system for recording holograms of objects having some movement with respect to the photographic plate which has the conventional signal beam and reference beam provided by a beam splitter having a phase shifter in the reference beam path to adjust the phase of the reference beam to correspond to phase shifts in the signal beam at the center of the hologram recording plate due to the movement of the object. The reference beam is brought to a focus and passed through an aperture between the phase shifter and hologram recording plate. The aperture is moved to adjust the reference beam for phase shifts in the signal beam at points not at the center of the hologram recording plate. In one embodiment the phase corrections are made by sensing means which sense movement of interference fringes at the center and one edge of the hologram recording plate with the output of the sensing means being applied to phase shifters in the reference beam.

Diffraction grating interferometer

Abstract: An interferometer, and preferably an infrared laser interferometer, employing a single, reflecting diffraction grating operating as both the beam splitter and the reference surface. A collimated beam from the radiation source is directed onto a surface of the diffraction grating and is diffracted into two separate beams, namely a test beam and a reference beam. The test beam is directed to the test optical system and is then reflected back, as a return beam, from the test optical system to the diffraction grating, at an angle such that a diffracted return beam is produced by the diffraction grating that coincides with the reference beam. An interference pattern is produced between the reference beam and the diffracted return beam, that can be observed, at the plane of observation, visually or recorded with an image recording device.

Method and apparatus for aligning a laser beam projector

Abstract: A method and apparatus particularly suited for use in aligning an optic system, such as an astronomical telescope, employed as a laser beam projector for projecting a beam of laser light against a celestial target and including therein an arrangement of optically related lenses and mirrors by which light emanating from a celestial target is brought in focus to form an image of the target within the focal plane of the optic system, and characterized by the utilization of a beam splitter having a reflecting surface including a microscopic opening disposed within the path of a projected laser beam, as well as within the path of the light being brought in focus, whereby the laser beam is projected through the optic system toward the target, while the light emanating from the target is brought in focus in the focal plane of the system and then redirected by the reflecting surface of the beam splitter to a second optic system for imaging both the target and the opening formed in the beam splitter for thereby accommodating a visual detection of optical alignment of the system for assuring alignment of the system relative to the target.

Radar system with beam splitter and synthetic stabilization

Abstract: A multifunction radar system generating a vertical fan beam of radiant energy continuously movable in azimuth for terrain mapping with a plan position indicator-type display screen and including antenna means having a fan beam energy-response pattern generally normal to the vertical fan beam and movable in elevation to intersect the vertical fan beam at selected elevation angles for detecting reflected energy and generating a range marker on the display screen defining an elevation-aiming angle for performing various target-tracking functions including establishing glide slopes, clearance planes and direction-control information. The generated range marker is stabilized relative to pitching motion of the vehicle as well as referenced to the antenna boresight axis by special processing of composite return signals.

Ir-optical image reproducing system and method

Abstract: An IR-optical image reproduction system which comprises an objective, a field lens and collimator arranged in optical series. The objective focuses the incoming image at an image plane and the field lens is positioned at this plane. The collimator forms a parallel beam path of smaller diameter than that of the image entering the objective. A stop is positioned in the path and is provided with an aperture which permits the passage of the parallel beam while blocking heat rays which might be generated upstream of the stop. A second objective receives the parallel beam and focuses an image at a receiver all which responds to the IR content thereof. This cell has a determinable operating temperature and a cooling apparatus is provided which cools the system between the collimator and the cell to a temperature which is close to that of the cell. A beam splitter can be provided which operates on the parallel beam and with this beam splitter is associated another objective and receiver cell. A cooling apparatus is also provided to operate with this additional structure.

Scanning scattered light photometer

Abstract: A scanning scattered light photometer system having a rotor with a beamsplitter-polarizer and a nozzle for directing an aerosol flow along the axis of the rotor toward an exhaust outlet The aerosol flow is illuminated by a collimated monochromatic unpolarized light A polarizing beamsplitter on the rotor separates the scattered light into two perpendicular components A first mirror on the rotor directs a first polarized component of light in the plane of rotation of the rotor toward a first photomultiplier A second mirror on the rotor directs light polarized perpendicular to the plane of rotation toward a second photomultiplier A fixed mirror directs undispersed light toward a photoconductive device to provide a synchronizing output pulse when the polarizer beamsplitter passes through the beam between the light source and the aerosol flow The outputs of the photomultipliers and photoconductive device are fed to a ratio and averaging circuit and then to a recorder

Improvements in or relating to Vibration Responsive Apparatus

Abstract: 1,173,772. Optical detection of movement; light modulators. DECCA Ltd. 3 Feb., 1967 [16 Feb., 1966], No. 6902/66. Headings H4D and H4F. [Also in Divisions G1, G2 and H1] The characteristics of vibrations, such as of a machine or a distant window vibrated by speech within a room, are determined by comparing a laser beam, Doppler shifted by the vibrations, with a second beam derived from the same laser, the second beam being shifted in frequency, or alternatively the first beam being further shifted in frequency, by an amount greater than the Doppler shift introduced by the vibrating element, vibratory movement towards and away from the laser can thereby be distinguished. In the embodiment a laser beam is split into two orthogonally polarized beams by prisms 14 having a polarizing dielectric interface. One beam is directed by a telescope 17 to a vibrating element 10 of interest and the second, a reference beam to a mirror 16 vibrating at a frequency much higher than the element 10. Both beams are returned and combined at prisms 14 and are directed via a half-wave plate 19 and a second beam splitter 20 on to photo-electric detectors 21 and 22. The outputs of the detectors are passed to a differential amplifier, whose output comprises a signal representative of the vibrations of the element 10 and modulated at the frequency of the mirror 16. Demodulation occurs at 24 and a receiver such as a loud-speaker or audio recorder indicates the vibrations of the element 10. If the frequency of the vibrating mirror is low, but the speed of the mirror high enough to sufficiently shift the second beam, synchronous switching of the amplifier output is necessary. Instead of a vibrating mirror 16 a Kerr cell or Pockel's effect modulator could be used.

Influence of interference fringes of equal inclination on the reflection of laser beams from plane parallel plates.

Abstract: The coefficient of reflection of plane parallel plate beam splitters is very often taken as twice that of a single surface reflection. It is shown that this introduces appreciable errors in the majority of cases, because of the interference fringes of equal inclination. Formulas are derived for the angular dependence of the coefficient of reflection as well as for its average value. The angular distance between adjacent fringes has been evaluated and represented graphically. It is finally demonstrated that the influence of incomplete interference due to the lateral displacement of the reflected beam can be neglected if the beam splitter is followed by an integrating sphere or a similar element.

System for focusing laser energy

Abstract: 1,143,138. Optical apparatus. HUGHES AIRCRAFT CO. Oct. 10, 1966 [Nov. 1, 1965], No. 45108/66. Heading G2J. [Also in Division H1] A laser is associated with an alignment microscope and means are provided for determining respective focal planes for the laser beam and for the microscope light path, the relative displacement between the focal planes being adjustable by controlling an optical system in the light path of the microscope and not in that of the laser beam. An enclosure 49 is mounted on a housing for vertical movement in response to rotation of a lead screw. The housing contains a laser, the output beam from which is deflected by a dichroic mirror beam splitter 51 to pass through an objective lens 72. The mirror 51 is transparent to radiation at wavelengths other than that of the laser beam and so transmits light from object 76 through optical system 86 Fig.5 to microscope eye-pieces 82. The optical system includes a reticle 92, lens system 96 and a movable lens holder 98. The lens holder is mounted for vertical non-rotary movement in response to rotation of a focusing cam having adjustable cam surfaces 111, 112, and is biased downwards by a spring 103. If the lens holder is adjusted so that the focal plane for the microscope is above or below that for the laser beam, when the microscope is focused on object 76 the laser beam is focused to a point such as 75 and the laser energy is directed on to a spot of known diameter on the object. If the focal planes coincide the laser beam impinges on the object with minimum spread and maximum energy.

Optical label reading systems

Abstract: 1,245,472. Track apparatus. G.T.E. SYLVANIA Inc. 16 July, 1968 [19 July, 1967], No. 33897/68. Heading B7N. [Also in Division G1] In an arrangement of the kind described in Specification 964,570 in which a coded label formed of a vertical stack of horizontal, coloured, retro-reflecting stripes on an object, e.g. a railway vehicle, is scanned vertically by a light beam to read the coded information, improper operation due to foreign matter, e.g. dirt on the label is largely eliminated by operating the arrangement with polarized light. Light from source 18 is polarized by polarizer 19 and scans the label 1 via mirror 30 and mirrors 32 on rotating drum 34. Polarized light reflected from a stripe and unpolarized light scattered by the foreign matter present on the stripe is directed via the mirrors 32 through apertures in mirror 30 and mask 48 to a dichroic mirror 35. Assuming the stripe colour is blue, the polarized light and the blue component of the unpolarized light is passed via blue pass filter 54 to a beam splitter 65. The polarizer 71 is similar to polarizer 19 and passes the polarized blue light and that part of the unpolarized blue light having a similar plane of polarization to a detector 73, e.g. a photo multiplier. Polarizer 70 passes light polarized at 90 degrees to that passed by polarizer 71 and hence only passes the portion of the unpolarized blue light having that plane of polarization to a similar detector 72. The portions of the unpolarized signal passed by the polarizers 70, 71 are similar in amplitude and that passed by polarizer 70 is subtracted from the signal developed by detector 73 in a subtract circuit 74 which provides an output which is a function only of the reflected polarized blue light. Similarly, light converting means 56 provide an output when an orange stripe is scanned. Fig. 2 (not shown) shows a simpler arrangement for use when the stripes are of a single colour.

Method of testing transparent materials

Abstract: 1,145,353. Photo-electric measurement. INSTITUT NATIONAL DU VERRE. March 15, 1966[March 31, 1965], No.11346/66. Heading G1A. Angularity (non-parallelism of opposed surfaces) and local distortions (e. g. lens effects due to chemical or physical heterogeneities) in sheet material 12 (e. g. a lens or windscreen) are detected and measured using a detector 24 located to receive light transmitted through the sheet and distorted thereby, but in such a position as to be on the same axis as the light beam 10 incident on the sheet. In the described embodiment, the basic optical system comprises lenses 6 and 15, focusing the image of an opaque disc-shaped mask illuminated by source 2, on to the opaque centre portion 22 of an annular aperture 21 on a screen 20 located in front of photo-cell 24. When no sheet is present in the light path, the image is superimposed exactly on the centre portion 22. The presence of a sheet having a degree of angularity causes and angular displacement (refraction) of the light and the image overlaps on to the open part of the annular aperture, cutting down the amount of light reaching detector 24. The output signal of the detector is thus representative of the presence and the degree of angularity of the sheet. In order to avoid measurement inaccuracies due to changes in light source intensity and transparency or clearness &c. of the sheet, a beam splitter 17 is provided to direct light to a second (reference) photo-cell 28, which may be connected in a Wheatstone bridge circuit with cell 24, or some other suitable circuit. A visual (e. g. meter) or audio indication may be taken, or a record (photographic, magnetic, &c. made. The record can be a continuous one taken as a particular line across the sheet is moved through the light path or as the sheet is rotated. From this record, thickness variations may be determinable. The effect of a change in light flux on the reference cell 28 due to angularity changes, is reduced by having a diffusing screen and large adjustable aperture in front of the cell. Instead of the opaque mask 8, an attenuator, or colour or polaroid filter may be used, an appropriate attenuator or filter being provided instead of the opaque portion 22 in front of cell 24. The mask may be of semicircular or quadrant form and the screen aperture 21 circular or partly obturated by a segment, Figs. 2, 3 (not shown). Such masks may be rotated instead of moving the sheet, when angularity variations in all directions are required.

A Narrow Band Far Infrared Interferometer for Electron Density Measurements

Abstract: An interferometer has been constructed with reflection optics and lamellar gratings to operate in the wavelength range of 175–400 μ. The gratings serve not only as beam splitters and recombiners but also as filters to separate out a narrow band of radiation. In this way a simple wide band Hg arc lamp can be used as the source. Because of the required response time for afterglow plasmas, a Putley detector measures the radiation. An application of the interferometer has been made to measure electron densities in repetitively pulsed plasma with λ = 200 μ and a time response of 3 μsec. The electron line density sensitivity is 3×1013 cm−2 and line densities have been measured up to 1015 cm−2, still substantially below the instrumental limit.