Showing papers in "Optics and Laser Technology in 1975"
606 citations
TL;DR: In this paper, a new optical technique for displaying both small surface displacements and the absolute shape of large objects is described, based on recording fine detail appearing in random patterns applied to the surface.
Abstract: This describes a new optical technique for displaying both small surface displacements and the absolute shape of large objects. The method is based on recording fine detail appearing in random patterns applied to the surface. The detail is recorded at a high spatial frequency using a modified 35 mm camera and fine grain film. Information concerning relative and absolute displacements is contained in light diffracted by the processed negative.
47 citations
44 citations
TL;DR: The techniques of temporal and spatial modulation to overcome the inevitable dc bias are described and a wide but not exhaustive range of examples of applications are given.
Abstract: The basic principles of non-coherent optical processing are first described. These include the diffuse source, redundancy, and parallel processing. The techniques of temporal and spatial modulation to overcome the inevitable dc bias are next described. A final section on applications gives a wide but not exhaustive range of examples.
34 citations
TL;DR: In this article, the mechanisms by which laser-induced damage occurs and summarizes the forms of such damage which are seen in practice are reviewed and experimental conditions for making accurate damage threshold measurements are set out, and the apparatus and procedures used in the present work are described.
Abstract: The high power and energy densities in a Q-switched laser beam modify the optical characteristics of a transmitting material and may ultimately cause damage. This paper reviews the mechanisms by which laser-induced damage occurs and summarizes the forms of such damage which are seen in practice. The experimental conditions for making accurate damage threshold measurements are set out, and the apparatus and procedures used in the present work are described. A summary of the laser-induced damage threshold measurements at 1.06 μm on a wide range of materials under the same conditions are presented and compared with other published data.
26 citations
TL;DR: In this article, a photographic rotating-film technique was used to fabricate apodized apertures from photo-sensitive glass plates, which can be constructed in various ways.
Abstract: To obtain maximum energy output from a high-power laser system it is necessary to carefully shape the input beam's cross-sectional intensity profile This avoids diffraction-produced hot spots which can cause damage to the amplifier components The intensity should be at a maximum in the central part of the beam and fall of gradually at the edges to avoid hard-edge diffraction effects This kind of beam profile can be produced using an apodized aperture — a soft-edged aperture that may be constructed in various ways This report describes a photographic rotating-film technique for fabricating apodized apertures from photo-sensitive glass plates
23 citations
TL;DR: In this article, the Lissajous figures traced by each speckle were interpreted in terms of the LISSajous figure traced out by each point on its trajectory, taking into account the time-of-dwell of a specular point at any point on the trajectory.
Abstract: Speckle photographs of a laser-illuminated surface vibrating in its own plane give characteristic diffraction spectra. These have been investigated for a surface vibrating sinusoidally along two mutually orthogonal directions with equal amplitudes but differing frequencies. The diffraction patterns obtained are interpreted in terms of the Lissajous figures traced out by each speckle, taking into account the time-of-dwell of a speckle at any point on its trajectory. Results are given for frequency ratios of the two vibrations of 1:1, 2:1, 3:1. 4:1, and for non-integrally related frequencies.
23 citations
TL;DR: In this article, a simple method for characterizing the effect of light at 633 nm on the layers, in terms of refractive index changes and surface relief formation, is described.
Abstract: Stable red-sensitive layers consisting of methylene blue, acrylamide, and a reducing agent have been prepared. The reducing agent can be a sodium salt of p-toluene-sulphinic acid or dimedone, dissolved in the polymers gelatin or polyvinyl alcohol. A simple method for characterizing the effect of light at 633 nm on the layers, in terms of refractive index changes and of surface relief formation, is described. The application of the layers in spatial filtering is proposed.
22 citations
TL;DR: In this paper, a photographic study of areas of damage which occurred on a number of germanium etalons used as output mirrors of a pulsed CO 2 TEA laser is presented.
Abstract: We present a photographic study of areas of damage which occurred on a number of germanium etalons used as output mirrors of a pulsed CO 2 TEA laser. A search of the damage revealed certain characteristics which appeared at many locations on any particular etalon face, and on each of the several etalons used. The damage on the inside cavity face was always greater, both in extent and in depth, than that on the outside or exit face of the etalon. However, the patterns observed showed similar characteristics on both faces. A detailed description of the topographical features of the damage is given followed by an account of the proposed damage mechanisms.
20 citations
TL;DR: An opto-electronic system that allows a stable accurate frequency shift, variable from 10 kHz to 50 MHz, to be introduced in a laser Doppler velocimeter (LDV) has been developed.
Abstract: An opto-electronic system that allows a stable accurate frequency shift, variable from 10 kHz to 50 MHz, to be introduced in a laser Doppler velocimeter (LDV) has been developed. The system combines a fixed optical-frequency shift obtained using a Bragg cell with an electronic shift which results from mixing the detector signal with a variable local oscillator frequency phase locked to the Bragg cell driver. This paper discusses the advantages of the system in both a tracker and a counter based LDV.
19 citations
TL;DR: To circumvent the inherent inaccuracy of optical analogue computers an optical digital computer is proposed, Boolean algebra is performed using polarization properties of light.
Abstract: To circumvent the inherent inaccuracy of optical analogue computers an optical digital computer is proposed. Boolean algebra is performed using polarization properties of light. Some practical devices for implementation are mentioned.
TL;DR: In this paper, the first lensless in vivo hologram of a rabbit eye was presented, in which a fibre optic bundle was used to transmit the 514.5 nm light of a cw argon laser to the fundus.
Abstract: The first lensless in vivo hologram of a rabbit eye is presented in this paper. A new, highly adaptable method of fundus illumination for holography is discussed, in which a fibre optic bundle is used to transmit the 514.5 nm light of a cw argon laser to the fundus. The virtual image formed by the hologram may be viewed through the opthalmic lenses normally used with the indirect opthalmoscope.1,2 Except for laser speckle, which may be minimized, viewing is much the same as that in monochromatic fundus examination.
TL;DR: In this article, a relatively simple semi-sealed-off CO laser which operates near room temperature is described and an intra-cavity grating is used to select single-line output powers of about 2W.
Abstract: A relatively simple semi-sealed-off CO laser which operates near room temperature is described. An intra-cavity grating is used to select single- line output powers of about 2W.
TL;DR: The various biomedical problems which could possibly be solved by using holography are reviewed and ways of overcoming them are suggested.
Abstract: This paper reviews the various biomedical problems which could possibly be solved by using holography. The practical problems are outlined and ways of overcoming them are suggested.
TL;DR: A review of the fundamental concepts associated with passive displays based on liquid crystals and other liquid media is presented in this article, where the operation of dynamic scattering and field effect type liquid crystal displays is discussed in detail.
Abstract: A review of the fundamental concepts associated with passive displays based on liquid crystals and other liquid media is presented. The operation of dynamic scattering and field-effect type liquid crystal displays is discussed in detail. Electrophoretic, electrochromic, rotatable dipole, and liquid vapour displays are also described.
TL;DR: In this article, optical transmission measurements with bulk plastic materials and plastic fibres regarding the possible application as a transmission media for high optical powers were performed with a light source available and a transmitted cw output power of 2.1 W with a 1.5 m long fibre.
Abstract: Optical transmission measurements were performed with bulk plastic materials and plastic fibres regarding the possible application as a transmission media for high optical powers. Transmission losses of PMMA bulk material and PS/PMMA core-cladding combination optical fibres were determined to be 0.757 dB m-1 and 1.41 dB m-1 at 514.5 nm, respectively. The core material of the investigated fibres withstands a power density of 3.8 x 103 W mm-2 when the light is suitably launched. With the light source available a transmitted cw output power of 2.1 W could be attained with a 1.5 m long fibre.
TL;DR: In this article, a technique for remote measurement of profiles, vibrating targets, and for the measurement of range is described, which employs an intensity modulated laser beam which forms part of a closed loop control system.
Abstract: A description is given of a technique which can be used for the remote measurement of profiles, vibrating targets, and for the measurement of range. This technique employs an intensity modulated laser beam which forms part of a closed loop control system. The modulation frequency is automatically varied as the range changes so that the phases of transmitted and received signals always differ by π/2 rad; A theoretical analysis of the measurement technique is given, together with results from a practical system.
TL;DR: In this paper, the self-imaging property of a circular grating is applied to centring error detection and to alignment in space, which is easy and comfortable to make visual observations.
Abstract: Optical alignment operations and Fourier imaging phenomena have the common property that both occur in space along a straight line. The self-imaging property of a circular grating is applied to centring-error detection and to alignment in space. Moire fringes due to the interaction of Fourier (or Fresnel) images with a detecting grating provide an indicator of the alignment state. The merit of this approach is that it is easy and comfortable to make visual observations. Various applications of the method depending on the choice of the reference points used are discussed and some experimental data are presented.
TL;DR: In this article, an economic solution was achieved by simultaneously using the acousto-optic modulator already included in the setup as a compensating deflector, which was used to compensate axial deflection errors of a polygon mirror.
Abstract: In laser beam recording systems, axial deflection errors of a polygon mirror give rise to banding patterns which recur with each scanner rotation. Experiments for compensating such errors by an additional deflection of the light beam are discussed. An economic solution was achieved by simultaneously using the acousto-optic modulator already included in the setup as a compensating deflector.
TL;DR: In this article, the coded image of a simple three-dimensional x-ray object is deconvoluted by means of three different decoding systems: by an optical projection system using spatially incoherent light, by an on-line optical set-up with information input using an electro-optic relay tube, and by a quasi-on-line electronic system using an electronic storage-tube.
Abstract: A non-redundant distribution of ten point sources is used for coded aperture imaging. The coded image of a simple three-dimensional x-ray object is deconvoluted by means of three different decoding systems: by an optical projection system using spatially incoherent light, by an on-line optical set-up with information input using an electro-optic relay tube, and by a quasi-on-line electronic system using an electronic storage-tube. The three methods are compared with respect to signal-to-noise ratio, resolution, and convenience of handling.
TL;DR: The authors reviewed areas in which the laser has potential clinical applications in dentistry, such as caries inhibition, pulpal cautery, and laser welding, and the advantages of using a laser are given.
Abstract: Areas in which the laser has potential clinical applications in dentistry are reviewed; caries inhibition, pulpal cautery, and laser welding. Results of preliminary investigations into these applications are described and the advantages of using a laser are given
TL;DR: In this article, material and structural properties of the waveguide are related to measurements made on present experimental waveguides, and the conclusions drawn from this work are that intermodal dispersion provides the dominant pulse broadening contribution but this has been reduced to the nanosecond region by radial index gradient control.
Abstract: As a result of research, the propagation characteristics of optical waveguides are becoming well enough understood for system evaluation. In this paper material and structural properties of the waveguide are related to measurements made on present experimental waveguides. Among the conclusions drawn from this work are that intermodal dispersion provides the dominant pulse broadening contribution but that this has been reduced to the nanosecond region by radial index gradient control. For present source spectral bandwidths, material dispersion is not a major contribution to pulse broadening. Waveguides up to 3 km long can be made with negligible intrinsic mode coupling. This gives rise to the possibility of either internal or external control to increase the information carrying capacity of the waveguide. External control has already been demonstrated. However, additional work is required to make this practical.
TL;DR: In this paper, the detection of loose contacts in relays presents several problems, such as: the contacts are small, the relays are small and the communication links are short.
Abstract: The detection of loose contacts in relays presents several problems. The contacts are small,
TL;DR: In this article, the basic theory of the avalanche photo-diodes was briefly reviewed, followed by a few examples of the possible performance compared to that of a PIN photodiode.
Abstract: The aim of this paper is to encourage the use of avalanche photo-diodes in optical communication systems, especially if high speeds are required. The basic theory of the device is first briefly reviewed. This is followed by a few examples of the possible performance compared to that of a PIN photodiode. Some frequency response measurements of recent avalanche photodiodes are then presented.
TL;DR: In this paper, a comparison between internal and external amplitude modulation of a laser using electro-optic modulators is presented. And the results show that for a high ratio of laser gain to modulator loss, internal phase modulation can give a higher signal output power and a better signal-to-noise ratio, with greater efficiency.
Abstract: This paper presents a comparison between internal and external amplitude modulation of a laser using electro-optic modulators. For a high ratio of laser gain to modulator loss, internal phase modulation can give a higher signal output power and a better signal-to-noise ratio, with greater efficiency.