Showing papers on "Waveplate published in 1987"

Four waveplate dual tuner for birefringent filters and multiplexers

Abstract: A Solc-type birefringent filter with five crystal elements in a wavelength multiplexer configuration is tuned with a minimum number of waveplates by means of a new four waveplate dual tuner that adds equal retardations to two elements simultaneously.

Beam splitter for multibeam A/O modulators and printer systems

Abstract: A scanning system with unpolarized laser, a birefringent beam splitter to split the unpolarized beam into dual orthogonally polarized beams, a polarization insensitive unitary dual beam modulator for separately modulating the beams in accordance with discrete image signal inputs, and a control for operating the modulator at optimum acoustic power levels. In an alternate embodiment, a quarter wave plate is inserted in the optical path between laser and beam splitter.

Apparatus for measuring photoelasticity

Abstract: An apparatus for measuring photoelasticity permitting to control mechanical stress applied to an elastic body, by visualizing phase differences of polarized light transmitted by the elastic body is disclosed. In such a prior art apparatus a quarter wavelength plate was used in order to obtain circularly polarized light. However, the precision of the circularly polarized light is worsened, when it works in a wide wavelength region. To the contrary, in an apparatus according to this invention, circularly polarized light is obtained by means of Fresnel's rhombic body. As the result good circularly polarized light can be obtained for a wide wavelength region from the visible region to the near infrared region and control of products including thin films and semiconductor substrates can be effected by visualizing mechanical stress therein.

Multioscillator ring laser gyro beam combining optics

Abstract: Multioscillator beam-combining optics having prisms for processing both clockwise and anticlockwise elliptically polarized beams having both helicities transmitted through a partly transmissive corner mirror. The optical structure uses a thin-film polarizer with a waveplate which is not necessarily a quarter wave plate. Further, the waveplate thickness is determined so that one component of elliptically polarized light is converted into a linearly polarized beam. A thin film polarizer then blocks the linearly polarized beam. The waveplate principal crystal axes form a nominally forty five degree angle with the s and p polarization axes. Techniques are used to keep extraneous birefringence of the beams to a minimum.

Bi12SiO20 crystal application for voltage sensor in optical fibers

Abstract: A voltate sensor for optical fibers using a transversal BSO (Bi12SiO20) modulator is presented. The sensitivity of the sensor depends on the BSO crystal shape and the polarization states of the polarizer and the analyzer. The crystal shape is designed to reduce the insertion loss in the optical fibers. We optimized the polarizer and the analyzer to maximize the sensitivity by establishing a method to calculate the sensitivity. We found that one of the best solutions is to set the polarizer for circular polarization and the analyzer for linear polarization rotated by half of the optical rotatory power to the normal of the electrodes. To minimize the insertion loss, we used a polarizer which consists of a TiO2 single crystal (rutile) plate with a quarter wave plate and an analyzer which consists of a rutile plate with a half wave plate. By using these components, we obtained 0.28%/V sensitivity at 0.85 μm wavelength.

Optical displacement measuring apparatus

Abstract: PURPOSE:To enable the measurement of the displacement of a rotating shaft affected little by noise by an inexpensive construction wherein a single frequency laser is used, a wave plate and others are provided on the opposite end faces of the rotating shaft, two AC signals having informations on the displacement are taken out, and a phase difference between them is determined. CONSTITUTION:A light of a single frequency emitted from a laser 1 is split onto the right and left sides by a beam splitter 2. The light on the left side is split in two by a beam splitter 3, and a reflected light reaches a photodetector 10 as a reference light. A transmitted light passes, as a measured light, through a rotary 1/4 wave plate 6 fitted to the left end of the rotating shaft of a motor 23, is reflected by a mirror 7 and deflected at an angle of 90 deg. in the direction by a beam splitter 4, and reaches the detector 10. Herein a sine wave signal obtained by the addition of the reference light and the measured light is detected. The light on the right side is subjected to the same operations as the above in similar devices provided at the right end of the rotating shaft, and a sine wave signal is detected in a photodetector 20. The two sine wave signals are sent to a phase difference detector circuit 20 and a phase difference between them is detected therein. The signal obtained from the detection is sent to a displacement operation circuit 22, and an amount of the displacement in the axial direction of the rotating shaft is thereby calculated.

Light source device in two-beam scanning system

Abstract: PURPOSE:To obtain recording pictures with high density by providing two semiconductor lasers, a polarizing beam splitter, an adjusting means, and a quarter- wave plate. CONSTITUTION:Though the beam emitted from a semiconductor laser 10A is an S-polarized light until it is transmitted through a cylindrical lens 14A, it is converted to a P-polarized light by the action of a half-wave plate 15A when it is transmitted through this plate 15A. Consequently, the beam from the semiconductor laser 10A is made incident on a polarizing beam splitter 16 as the P-polarized light and is transmitted through this splitter 16 to join with the beam from a semiconductor laser 10B. Two joined beams are transmitted through a quarter-wave plate 18 and are converted to circularly polarized light beams and are made incident on a rotary polygonal mirror 20. Since each beam is converted to the circularly polarized light, reflectivities due to the rotary polygonal mirror 20 are made equal to each other even if an angle thetaof incidence is changed, and two lines are scanned optically on the same exposure condition. Thus, recording pictures with high density are obtained.

Some Recent Developments in Laser Interferometry

Abstract: An account is given of some new interferometric developments which can be used to improve the performance of the laser interferometer as a position sensing device. The first of these developments, termed the double pass attachment, is an optical accessory which doubles the resolution of the Hewlett-Packard linear and plane mirror interferometers. Unlike previous attempts to extend resolution optically, this device does not fold one of the two interfering beams and hence does not introduce error due to its own motion. The simple addition of a quarter wave plate to the attachment can be used to give a differential version of the plane mirror interferometer. Various configurations of this differential interferometer, and their application to machine tool and integrated circuit lithographic and inspection equipment, are discussed. A new “wavelength tracking” device, based on differential interferometry, is described. This device directly and precisely monitors changes in laser wavelength inside a highly stable mechanical cavity. It can be easily incorporated, as an additional interferometer axis, into precision machines to give superior compensation for changes in laser wavelength.

High-Sensitivity Photoelastic Pressure Sensor

Abstract: By selecting the proper geometry for the reactive element of a photoelastic sensor a considerable improvement in sensitivity over conventional intensity-modulated sensors can be achieved. Other recent photoelastic sensors have consisted of an essentially rectangular prismatic bar of transpqrnt material which is stressed uniformly by a strut connected to a force-summing diaphragml,L. Our alternative is to fabricate the diaphragm itself of a transparent material and use it for both the reactive and force-summing functions. In the basic form reported here the diaphragm consists of a thin glass plate mounted and sealed with zero residual stress on a circular support and subjected to varying differential pressure. Polarized light is directed into one edge of the plate along a diameter and received through an analyzer at the opposite edge. Analysis of the,resulting modulation in received optical power with crossed polarizers shows it to be a sin 4 function of applied differential pressure. The photoelastic phase delay is a linear function of pressure and parameters related to the geometry and material of the plate. For thin plates with maximum sen-sitivity the phase delay is proportional to the cube of the support radius and inversely proportional to the square of the plate thickness. An essentially linear response at zero pressure can be achieved with a quarter wave plate (thick sensor plates) or prestressing (thin sensor plates). Tests on experimental models have shown performance consistent with theory, with a response of 3.68 x 10-4 rad/pbar obtained with a 0.023 cm thick glass plate sealed on a 2.32 cm radius support. Extensive theoretical formulae and experimental data are presented.

Optical heterodyne measurement of phase retardation of wave plate

Abstract: This paper discusses an optical heterodyne technique for the measurement of phase retardation of a wave plate. The accuracy of the measurement of the optical pathe difference of the wave plate is roughly equal to the wavelength devided by 6000, better than other methods.

Optical image read-out and recordal scanning apparatus using a polarization beam splitter

Abstract: An optical image read-out and recordal apparatus comprises generating means for generating linearly polarized image read-out 101B', and image recordal 101A', light beams, means for scanning 107 said image read-out beam 101B' over an image 206 and for scanning said image recordal beam 101A' over image recording means 204 and a polarization beam splitter 108 for separating said image read-out and image recordal beams, characterised in that said apparatus further comprises at least one wave plate 104 disposed to rotate the planes of polarization of said read-out and recordal beams whereby the plane of polarization of one is perpendicular to that of the other and to the face of said beam splitter on the impingement of said read-out and recordal beams on said beam splitter 108. The correction or rotation of the planes of polarization may be conducted before or after two polarized light beams 101A and 101B are combined together by the first beam splitter 103.

Signal-to-noise ratio analysis of one- and two-channel halfwave plate polarimeters

Abstract: The theoretical shot-noise-limited signal-to-noise ratio (SNR) is compared for one- and two-channel half-wave plate polarimeters, where rotation of the halfwave plate within the system causes a corresponding rotation in the incident linear polarization. This analysis estimates the smallest possible waveplate rotation that may be resolved by each polarimeter. It is shown that, at least theoretically, the differentially amplified two-channel polarimeter provides a superior SNR and thus correspondingly greater angular resolution. The degradation of the SNR as a result of polarization imperfections that might be introduced by less than ideal optical components is also considered.

Switchable Infrared Waveplates and Shutters

Abstract: Artificial birefringence in a silicon slit structure has been demonstrated using 10·6 µm radiation. The 4 µm period grating of slits, 2 µm wide and up to 50 µm deep, was formed by an anistropic etching technique. The birefringence was investigated as a function of temperature and found to agree with theory. The possibility of electronic control of devices based on the birefringent properties, such as waveplates and shutters, is discussed.

Polarization variable device

Abstract: PURPOSE:To shorten the time for measurement by providing a Glan-Thompson prism, halfwave plate and quarter-wave plate supported rotatably with respect to the plane orthogonal with an optical axis between input side and output side optical fibers coupled to a lens. CONSTITUTION:The input side optical fiber 11 of a single mode is connected to a semiconductor laser and the output side optical fiber 21 of a single mode is connected to an optical power meter via a device to be measured (not shown in the figure). The Glan-Thompson prism 4 is formed by sticking two calcite prisms and is so adjusted that linearly polarized light is obtd. in the state of the largest optical power by aligning the main polarization axis and transmission polarization axis of a semiconductor laser. The halfwave plate 5 is capable of arbitrarily setting the main axis of polarization and projects the polarized light at the necessary polarization axis on the device to be measured when said plate is rotated. The quarter-wave plate 6 cancels the elliptical polarization of the polarized light by the double refraction which is generated by the local stress of the optical fiber 21. The P or S polarized light is thereby polarized to the linearly polarized light and is projected to a coupler which is the device to be measured.