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  • 1
    ISSN: 1349-9432
    Keywords: homogeneous nematic liquid crystal ; phase retardation ; birefringence ; homodyne interferometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We describe herein a method to measure quickly (in less than 2 min) and accurately the phase retardation between the extraordinary and ordinary axis of homogeneous or 0° twisted nematic liquid crystal panels. Owing to the homodyne detection scheme, the setup allows us to probe liquid crystal (LC) panels with an optical power down to a fraction of 1 nW and, hence makes it possible to focus the light beam to a spot of only a few wavelengths in diameter without heating or inducing observable variations in the liquid crystal. The dependence of the phase retardation on the LC driver frequency and the temperature are presented and compared with the theoretical prediction.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Optical review 1 (1994), S. 121-124 
    ISSN: 1349-9432
    Keywords: particle sizing ; phase Doppler anemometry ; velocity measurements ; trajectory ambiguity ; generalized Lorenz-Mie theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Conventional phase Doppler systems are useful for sizing particles in the order of microns, but sensitive to the Gaussian beam defect which can cause sizing errors. The defect can be significant when a large size is measured. In this paper, we present a new phase Doppler system using a planar optical layout which permits large particles to be measured in a forward scattering scheme without the Gaussian beam errors. The optical system design is discussed by numerical simulation based on the Mie theory.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1349-9432
    Keywords: optical information processing ; Fourier optics ; fractional Fourier transforms ; spatial filtering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Fractional Fourier transforms, which are related to chirp and wavelet transforms, lead to the notion of fractional Fourier domains. The concept of filtering of signals in fractional domains is developed, revealing that under certain conditions one can improve upon the special cases of these operations in the conventional space and frequency domains. Because of the ease of performing the fractional Fourier transform optically, these operations are relevant for optical information processing.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Optical review 1 (1994), S. 27-29 
    ISSN: 1349-9432
    Keywords: optical disk ; dual focus ; optical head ; 0.6 mm disk ; 1.2 mm disk ; holographic optical element ; spherical aberration ; large numerical aperture ; high density optical storage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We propose a dual focus optical head with a holographic optical element (HOE) which corrects spherical aberrations in order to read both 0.6 mm disks and 1.2 mm disks. The thin disks are read using transmitted light and the thick disks are read using +1st order diffracted light of the blazed HOE. The good quality of the focused spots and the focusing error signals was experimentally confirmed. No influence of unnecessary diffracted light was observed.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1349-9432
    Keywords: optical computing ; planar optical device ; reading light supplier ; spatial light modulator ; fiber plate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A readout function of a reading light supplier (RLS) is demonstrated by reading out images from an optical addressable spatial light modulator (SLM). The RLS supplies reading light to the reading side of the SLM and transmits readout images from the SLM. The RLS consists of a fiber plate and a redirector which has micro conical-hollows. The RLS contrast, which is the intensity ratio of the reading light to the stray light, is 9.2 and the power efficiency of the reading light supply is about 5%. A writing pattern on the SLM is a checkered pattern of 5 mm×5 mm cells, and it is read out successfully using the RLS. The maximum contrast of the readout image is 1.9.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1349-9432
    Keywords: optical head ; molded glass ; asphere ; toric ; focus error ; lens design ; spot diagram
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An astigmatic method for focus error detection has been integrated into a singlet. The first convex and the second concave surfaces compose a telephoto system with a telephoto ratio of about 0.4. The first surface of the lens is rotationally symmetrical asphere and the second surface is a toric shape whose aspherical profiles correct spherical aberration. We implemented our optical design using a molded glass process. Its performance was confirmed using the optical head of a magneto-optical disk system.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Optical review 1 (1994), S. 1-2 
    ISSN: 1349-9432
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1349-9432
    Keywords: unconventional lens ; axially asymmetrical lens ; lens testing ; moire technique ; focusing power ; focal length
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Most lenses composed of spherical or aspherical surfaces have symmetrical focusing properties about an optical axis. On the other hand, unconventional optical systems such as cylindrical lenses, astigmatic or progressive power glasses have axially asymmetrical focusing properties. In this study, the method of measuring focusing properties by the moire technique is extended to asymmetrical lenses. Some unconventional lenses were experimentally tested, and the focusing power in the interesting region and azimuthal direction of the aperture was evaluated.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1349-9432
    Keywords: wideband optical heterodyne interferometry ; impulse response ; transfer function ; correlation processing ; lithium tantalate phase modulator
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In this paper, we describe a novel optical heterodyne interferometer for characterizing phase modulation systems including a lithium tantalate phase modulator. A wideband random signal is imposed on the modulator so that the resultant beat photocurrent is modulated in phase at random. The cross-power spectrum of the fluctuating phase with the wideband random signal driving the modulator is computed to give the transfer function and the impulse response of the phase modulation system. The frequency and time response of the phase modulation are measured up to 15 MHz in a practical experiment.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Optical review 1 (1994), S. 70-72 
    ISSN: 1349-9432
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A novel non-contact fiber optic accelerometer is presented. Two laser beams that have passed through two different lengths of feed fibers are launched to the same moving target. The frequency of each beam is Doppler shifted by movement of the target. The frequency shift of the laser beam corresponds to the velocity of the target at the time of launch. The difference in launching time due to the difference in feed fiber lengths samples the velocities of the target at times spaced by the differential arrival times of the laser beams. Two return passes of the reflected light are also made different so that the light passed through the shorter feed fiber is steered to the longer return fiber by means of a combination of A/4 plate and polarization beam splitter (PBS). This arrangement of equalizing the total paths relieved a stringent requirement of the coherency of the laser. Two reflected light beams are mixed and the beat frequency corresponds to the difference in the Doppler shift frequency at two different times of arrival of the launcher. An accelerometer based upon this principle was constructed and its performance was examined using a sinusoidally vibrating hydrophone as a target. Features of such an accelerometer are reduction in the coherency requirements of the light source and simpler amplification of the signal using heterodyne detection.
    Type of Medium: Electronic Resource
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