Showing papers on "Beam splitter published in 1973"

Method of hologram recording with reduced speckle noise

Abstract: A sampling mask having a regular array of light transmitting areas is superimposed by a phase mask having a random array of phase shifting areas. The superimposed sampling and phase masks are holographically recorded for producing a hologram which later acts as a beam splitter to provide object and reference beams. The hologram so prepared is illuminated with a spatially incoherent broad source of light and imaged through an optical system. The zero order diffracted wave serves as the reference beam and the first order diffracted wave is used to illuminate an object transparency which is placed in the focused beam of the first order wave. Each point source of light from the spatially incoherent broad light source produces a corresponding interference fringe pattern, and it is shown that the interference pattersn exactly overlaps one upon another so that sharply defined fringe contrast results. The size of the light source is determined only by the required degree of resolution which in turn is dependent on the sampling spacing. The use of the incoherent broad light source enables uniform illumination of the object transparency, resulting in high-quality holograms with reduced speckle noise.

Self-compensating interferometer

Abstract: A self-compensating multi-channel laser system of a type having at least two substantially parallel optical channels, each channel having a first optical extremity comprising an optical aperture of said system and further having a second extremity including a photoelectric detector responsive to optical energy propogated toward the second extremity. The system includes mutually oppositely and coaxially disposed first and second laser generators having a common optical axis, the common axis being arranged perpendicular to the mutually parallel optical channels. First and second beam splitters are each disposed substantially along the common optical axis of the coaxial generators and within the optical path of a mutually exclusive one of the two channels. Phase-sensitive feedback modulation means responsive to the time-phase difference between the outputs of said photoelectric detectors compensatorily modulates one of the channels in such sense as to reduce the phase difference.

Combination of birefringent elements for polarizing interferential systems

Abstract: Polarizing interferential systems having a light source, a compensator element, an object, and a beam splitter element in optical alignment which utilize only a single birefringent wedge in the compensator element and only a single birefringent wedge in the beam splitter element are useful for the study of objects exhibiting light amplitude and/or phase properties. By tilting either the optic axis with respect to the light system, the entire wedge or both, it is possible to eliminate the dual wedge elements of the prior art and have greater versitility in instrument design.

Laser system with an antiresonant optical ring

Abstract: Various applications of an antiresonant ring, consisting of a beam splitter and a number of optical reflectors, are disclosed. With a beam splitter having a transmission coefficient t1 and a reflection coefficient r1 where t1 = r1, an optical beam incident on the beam splitter along a first axis is split into two components which circulate around the ring in opposite directions and are recombined to reflect back the beam along the first axis, with none of the beam power being directed along a second axis. The ring can be used as part of the cavity of two otherwise independent lasers, with two separate laser mediums external to the ring, or with a multi-wavelength laser medium in the ring. The ring together with a second-harmonic generation crystal and a dispersive phase shifter in the ring can be used to generate the second harmonic of an optical beam. By proper incorporation of phase shifting means in the ring, optical pulse switching, laser mode locking, and/or laser cavity dumping can be achieved.

Catadioptric beamsplitter system

Abstract: Optical systems especially suitable for tracking an object which emits infrared energy and directing a laser beam thereto are disclosed each including a lens and a first reflector for reflecting infrared energy to a first focal point and an interference filter being selectively reflective of laser energy and having a second focal point for directing laser energy to the target. The interference filter may be transmissive to infrared wavelengths of 3 to 5 microns and reflective to laser wavelengths of 10.6 microns.

Heterodyne Detection of Arcturus at 10.6 µm

Abstract: Heterodyne detection is the best technique for aperture synthesis in the infrared range. In the optical range the technique seems very hard and becomes of great interest only in the infrared, the limitation being the photon noise of the local oscillator1–3. We have achieved the heterodyne detection of Arcturus (α Bootis) at 10.6 µm in April 1973 during observations at St Michel l'Observatoire (France). The experimental arrangement is shown in Fig 1. It is based on the superimposition of coherent and incoherent beams which is achieved using a servomechanism working at 2.2 µm. The incoherent beam coming from the star is divided by the beam splitter No. 1 into two parts, the first with λ µm is detected by heterodyning. The position of the star image is controlled by a PbS cell working at 2.2 µm and the correction signal is sent to the piezo-electric quartz shown in Fig. 1. The mixing of coherent and incoherent beams is by the beam splitter No. 2. This beam splitter is coated so as to reflect 95% of the star beam and to transmit 5% of the laser beam.

Projection masking system

Abstract: In the system disclosed, illuminating means form an optical path. An imaging system in the optical path includes a support for a mask, an imaging lens that focuses the image of the mask onto an optical plane, and a support that holds a component having a radiation-sensitive surface at the plane. A filter in the illuminating system blocks out light capable of affecting the radiation-sensitive material but allows passage of some visible light so that the image of the mask can be seen on the component. A half-mirror or beam splitter allows light from the imaging lens to focus on the component but deflects a portion of the light coming from the component toward an analyzer that detects the alignment between the image of the mask and the component. A second half-mirror or beam splitter near the first half-mirror compensates for radial shift of the image relative to the axis of the light path caused by the first half-mirror. The analyzer as well as the half-mirrors and the filter may be removed simultaneously after alignment to allow projection masking.

Method and apparatus for focusing an objective

Abstract: In a method for focusing a reproducing objective, such as may be used for measuring distances, wherein multiplication of the image of the entrance pupil is achieved by image-splitting optical elements mounted in the plane of the object image, the improvement comprising: Projecting the light fluxes from different parts of the pupil image plane on separate sets or groups of photoelectric receivers, deriving a signal from the comparison of the output signals from these receiver groups and using this signal as a criterion for focusing as a function of magnitude and sign. Apparatus for performing the method includes a grid of prisms or pyramids, and a beam splitter for directing light through two separate photoelectric receiver masks.

Asymmetric michelson interferometer for solid state infra-red spectroscopy

Abstract: An asymmetric Michelson interferometer for infra-red solid state spectroscopy includes two concave mirrors of short focal length positioned in reference and sample beam paths leading respectively from a beam splitter to a retro-reflector and sample holder located close together in a low-temperature sample chamber at the focal points of the respective concave mirrors. The reference and sample beams have a "folded" geometry afforded by respective right angled mirrors, corner-cube reflectors or the like.

Interferometer apparatus incorporating a spherical element of index of refraction of two

Abstract: An interferometer arrangement of either the transmission or reflection type incorporating at least a pair of partially spherical or spherical elements having an index of refraction of approximately two is disclosed. In a preferred embodiment, the spherical or radiation directing elements are glass spheres having an index of refraction of approximately two at the wavelength of a light source being utilized. In a transmission type interferometer, both the spherical or radiation directing elements are utilized as beam splitters and collimators while, in the reflection type interferometer, one of these spheres is used as a beam splitter and collimator while the other is utilized as a retroreflector. The complete spherical symmetry of such radiation directing elements permits them to function with any orientation relative to the optical path between them. Mechanisms in which desired motions are controlled with high precision by applying mechanical feedback to position a movable body relative to a fixed reference body, using the above described interferometer arrangement are also disclosed. The same mechanisms are capable of being controlled from a programmed computer causing the movable body to exhibit a desired motion using interference fringe detection schemes to both monitor and accurately position the movable body relative to a reference body. Also disclosed is an actuator based on a hollow hydraulic cylinder having a given longitudinal axis which includes an interferometer arrangement incorporating at least a pair of spherical elements which have an optical axis substantially coincident with the longitudinal axis of the actuator. Also disclosed are transducer arrangements disposed in series with the actuator which are utilized to meet high frequency stability requirements.

Method and means for determining fatigue damage and surface stress

Abstract: The test specimen is mounted on a movable table, ultrasonic surface waves are caused to travel across the specimen by a transducer fed from a CW signal source, a laser beam is passed through a beam splitter, one portion being reflected onto a photo-detector measuring signal amplitude, an output signal is compared with the output of the CW signal and the CW signal shifted in phase by 90 DEG , these outputs measure ultrasonic phase difference, at points along the specimen; the second portion of laser beam is reflected from a mirror attached to the specimen table and back to a screen where an interference pattern is formed as the table is moved, photo detectors sense the changes in interference pattern and determine specimen displacement.

Operator viewing optics for a slide classification system

Abstract: In a system producing an electrical output representing the characteristics of a blood smeared slide, an optical system permits an operator to comfortably view the slide while it is being intensely illuminated. A television type detector produces the electrical output representing the optical characteristics of the blood on the slide. This detector requires that a very intense source of light be applied to the slide. In order for the operator to simultaneously view the slide a duplex beam splitter is inserted in the light path. A first prism in the beam splitter diverts a small percentage of the intense light to the operators viewing eye pieces. The first prism is a 30* -60*- 90* prism having an index of refracton such that the reflection from the second surface is directed out of the prims and away from the viewing eye piece to avoid ghost images. A second prism having the same geometry and index of refraction re-establishes proper direction of the light beam between the slide and the detector. The small portion of light directed from the first prism to the viewing eye piece is predominantly polarized in one direction. The degree of polarization is easily calculated by Fresnell''s law. A linear polarizer between the first prism and the eye piece is adjustable to provide continuously variable light attenuation. Adjustment of the linear polarizer through 90* rotation is sufficient to achieve the full light attenuation range.

Optical contour scanner

Abstract: A knife-edge type optical testing instrument including a pinhole source and a knife-edge device superimposed into space by means of a beam splitter. A pinhole source is conducted to the beam splitter from a remote source by means of a light conductor tube so that the bulk of the source is not disposed in the beam. The knife-edge shadow pattern is viewed remote from the operational region of the pinhole and knife-edge by means of a fiber bundle image conductor which transmits the pattern from the operational region of the knife-edge to the viewing apparatus. A triple slide mounting means maintains the pinhole source and knife-edge device in fixed relation but permits translation of the source and device accurately in three orthogonal degrees of freedom relative to a fixed reference. A triple slide base may be manually operable by means of micrometer screws having dial readouts for locating the knife-edge position. The viewing apparatus may include a microscope to provide pinhole demagnification to provide sharper shadows.

Optical ammunition inspection system and method

Abstract: A mortar projectile, having a long narrow flash passage leading to an ignition cartridge, is inspected for obstructions at the junction between the cartridge and the passage by reflecting an ultraviolet beam, by means of a dichroic beamslitter, through the flash passage to a photo-luminescent coating on the adjacent end of the cartridge. The ultraviolet beam excites the coating to produce visible light which passes back through the flash passage and the same beamsplitter to a detector, such as a photocell or photomultiplier tube. The ultraviolet radiation source includes a broad-band glow lamp or xenon flash tube and an ultraviolet filter and a second dichroic beamsplitter for filtering out most of the visible light. The inspection apparatus also includes a converging quartz lens and a plurality of lens stop apertures for focusing and collimating the ultraviolet beam to a small diameter at the photo-luminescent coating, a green light filter in front of the photomultiplier, and an automatic shutter for shielding the photomultiplier when not in use.

Design of nonpolarizing reflectors.

Abstract: In a number of different situations it would be desirable to remove some portion of the light from a beam in such a manner that neither the reflected nor transmitted por­ tions are different in their states of polarization from that of the incident beam. Examples are the use of a beam splitter as in a Michelson or Twyman-Green interferome­ ter, for sampling a beam to determine or monitor its in­ tensity or state of polarization, or to utilize only a portion of abeam. Baumeister et al. have discussed the use of quarterwave layers of nonabsorbing dielectrics to produce beam splitters such as required in an interferometer. Our in­ terest arose in connection with giant pulse systems for which it was interesting to determine to what extent the beam was linearly polarized, to determine if the adjust­ ment of a λ/4 plate or Kerr cell was properly made to pro­ duce circularly polarized light, or to monitor the beam power without affecting the polarization. In these cases it is useful to have a low reflectance so that the detecting equipment is not damaged and also so that the main beam is not seriously depleted. It is necessary in this case to use nonabsorbing materials. It is possible to construct a nonpolarizing reflector with a single dielectric layer on a substrate which has an index larger than that of the dielectric layer. However, the re­ flectance is less than 1% except at large angles of inci­ dence. Therefore, we have chosen to use two nonabsorb­ ing isotropic dielectric layers on a nonabsorbing substrate. Using standard matrix methods and assuming a very thick substrate, it can be shown that the reflectance R is given by

Signal-to-noise ratio for magnetooptic readout from MnBi films

Abstract: The signal-to-noise ratio in an optical memory has been analyzed and examined experimentally. A solid-state detector can be used with MnBi as the storage media, but for media with smaller magnetooptic rotation, a photomultiplier is considered necessary. Analyzer orientation and light beam intensity have been included in the analysis. Results with experimental apparatus employing a crystal beam splitter at 45° angle and solid-state detectors compares well with analysis.

Optical contour scanner

Abstract: A knife-edge type optical testing instrument including a pinhole source and a knife-edge device superimposed into space by means of a beam splitter A pinhole source is conducted to the beam splitter from a remote source by means of a light conductor tube so that the bulk of the source is not disposed in the beam The knife-edge shadow pattern is viewed remote from the operational region of the pinhole and knife-edge by means of a fiber bundle image conductor which transmits the pattern from the operational region of the knife-edge to the viewing apparatus A triple slide mounting means maintains the pinhole source and knife-edge device in fixed relation but permits translation of the source and device accurately in three orthogonal degrees of freedom relative to a fixed reference A triple slide base may be manually operable by means of micrometer screws having dial readouts for locating the knife-edge position The viewing apparatus may include a microscope to provide pinhole demagnification to provide sharper shadows

Doppler-shift velocity measurement system using a two-frequency laser

Abstract: A system for determining the velocity of a moving object, including a laser that emits light at two original frequencies to impinge on a reflector included on the object; a beam splitter and a mirror for directing the light emitted from the laser and the light reflected from the object to a photodiode; and a device for displaying an electrical signal generated in the diode that is the difference between one original frequency and the dopplershifted frequency of the other original frequency, the difference in frequency being a function of the velocity of the object and being in a range of values that are conveniently measured.

Document retrieval system

Abstract: An automatic retrieval system for locating desired frames of microfilm wherein each frame may be randomly located along a strip of microfilm. The coding employed is the use of humanly readable symbols, such as alpha-numeric characters, deployed along the margin of each side of each frame. The symbols are transparent against an opaque background and are small enough so that they will significantly diffract light. First and second rectangular beams of laser light scan first and second margins to provide a Fraunhofer diffraction pattern for each symbol. The Fraunhofer diffraction pattern is projected onto an array of photocells to provide a unique set of signals to indicate each symbol. Thus, each symbol is a byte, rather than a bit. A unique center symbol is used. A rectangular beam is developed from a circular laser generator output by compression in one direction through two cylindrical lenses to provide an elliptical beam. The elliptical beam impinges on a plate having a central slit to form a rectangular beam. The light on the slit is further processed and transmitted onto the film margin. A beam splitter splits the transmitted light into two beams, one for each margin on the film. The center symbols on opposite margins are orthogonally read to provide output signals which are nominally displaced 90* from one another so that direction of movement of film can be sensed and controlled. The code along each margin is replicated to improve signal to noise, reduce ambiguity and reduce erroneous readings.

Lens axis detection using an interferometer

Abstract: In the detection of the position of the axis of a lens, a coherent beam of light is divided, by a beam splitter, into two beams which are bent to intersect at a line and in the paths of which is positioned the lens to be examined at a location such that the center of curvature of a front surface coincides with the point of intersection of the two beams so that the two beams illuminate two portions on the curved surface of the lens. The two coherent beams strike the curved surface perpendicularly, after which they are returned along the same paths to the beam splitter and are superimposed thereby, at a line, to produce a pattern of interference fringes. During the detection, an axis of rotation, about which the lens to be examined is rotated, is selected so as to satisfy the condition that the pattern of interference fringes does not vary with rotation of the lens. When this condition is obtained, the position of the lens axis is determined.

Multi-layer beam splitter - for unpolarized electromagnetic rays in ultra-violet, visible or infra-red region

Abstract: The non-polarising beam splitter consists of a substrate with the refractive index ns and at least two vapour-deposited layers of alternating material of high and low refractive indices. All layers feature the same effective optical thickness which equals an odd multiple of LAMBDA o/4. Relations for two structures of refractive indices are given. The reflected and the transmitted beam portions contain the same s and p components which refer to the oscillation directions of the light waves directed vertically or parallel to the plane of incidence. The back of the substrate carries a heat-treated layer. Such non-polarising beam splitters are required for special combinations with lasers and in laser devices.

Polarizing effect of beam-splitter in two-beam interferometry

Abstract: Reflection and transmission at and through a metallic film change the polarization parameters of a beam of light. This implies that the two interfering beams of two-beam interferometers using such film as beam-splitter are different so far as the state of polarization is concerned. It is shown that in the resultant interference pattern there is a periodic variation of the state of polarization along with the periodic variation of intensity. Actual numerical calculations have been made to study the nature and extent of variation of polarization parameters due to the polarizing effect of an aluminium film coated on a glass-plate.

Optical apparatus for establishing logical relationships and for storing

Abstract: The arrangement includes a component made of a Pockels-effect crystal, for example a KDP crystal, one major face of which is coated with a dielectric mirror. In front of this mirror a photocathode and an image-forming electron-optical system may be provided or the mirror may be directly coated with a photosemiconductor, whilst the signals which are to be stored or between which logical relationships are to be established and which contain a plurality of binary elements in a two-dimensional intensity distribution are directed onto the said photosensitive layer, causing a corresponding charges image to be produced on the dielectric mirror. This charge rotates the plane pf polarization of a plane-polarized light signal which impinges on the crystal, passes through it and is reflected at the dielectric mirror so as to emerge again from the crystal. When the emerging light signal passes through an analyser, an intensity-modulated image is produced again. The analyser preferably is a polarizing beam splitter. According to operational conditions, in particular to the bias voltage set up between the photosemiconductor and the crystal, an OR function or an exclusive-OR function may thus be realized. A negation also may be achieved by a suitable choice of the operating conditions or by inserting a component which rotates light passing through it through 45* at a point of the ray path preceding the crystal. When the light signal which emerges from the crystal is directed onto the crystal of another component, an AND function may be achieved. By making combinations more elaborate logic functions also may be formed.

A simple beam-splitter attachment for physiological oscilloscopes.

Abstract: A COMMON REQUIREMENT in physiological experiments is the simultaneous display of several time-dependent variables. Although expensive oscilloscopes are available which can display four or more traces, many laboratories use a dual-beam instrument, which is normally limited to two traces. The simple and easily constructed device described below extends the display to four signals (with single-sided inputs) or three (with differential inputs). The device is inexpensive and requires no power supply. the two inputs alternately. In the 4-trace application, four separate signals are applied to the inputs. For differential operation, the two differential inputs are applied to terminals 1A and 2A and 1B and 2B, respectively. Outputs 1 and 2 are taken to the differential input of one channel of the oscilloscope.