Showing papers in "Optics and Laser Technology in 1988"
TL;DR: Improved techniques of collimation testing based on Talbot imaging and shearing interferometry are presented in this paper, which carry their own reference pattern to indicate collimation of the light beam.
Abstract: Improved techniques of collimation testing based on Talbot imaging and shearing interferometry are presented. The proposed techniques carry their own reference pattern to indicate collimation of the light beam. Detailed analysis is also given.
48 citations
TL;DR: In this article, the authors examined four materials, nickel, tantalum, EN58B and titanium, and obtained information about the drilling speed, and a statistical analysis of the results for drilling speed is undertaken, and the significance of each factor examined is determined.
Abstract: In the present study, four materials, nickel, tantalum, EN58B and titanium are examined, and information about the drilling speed is obtained. A statistical analysis of the results for drilling speed is undertaken, and the significance of each factor examined is determined. It is found that to obtain good holes it is not merely a matter of optimizing the surface power intensity, but adjusting all factors so that the process of transferring energy into the workpiece produces the desired effects.
44 citations
TL;DR: In this paper, an electro-optical device is described which allows the non-contact determination of the skin blood flow and its temporal course, which can be described in terms of the dynamic laser speckle effect.
Abstract: An electro-optical device is described which allows the non-contact determination of the skin blood flow and its temporal course. As the laser light penetrates the skin, it is not only scattered from the epidermis but also from the moving red blood cells in the capillaries. The scattered light is time dependent and can be described in terms of the dynamic laser speckle effect. Measurements at the skin demonstrate that there is a so-called ‘involuntary body movement’ which must be taken into account when the measurement of the blood flow is determined. Theoretical considerations show a way to reduce the influence of this movement. Some measurements demonstrate the response of the device to blood flow variations.
26 citations
TL;DR: In this paper, the properties of gas lenses are briefly reviewed and a continuous focus for a horizontal beam is obtained by injecting compressed air into a hot spinning pipe, which can be used to obtain a pulsed focus at any inclination.
Abstract: The properties of gas lenses are briefly reviewed. By spinning the lens a pulsed focus is produced at any inclination. A continuous focus for a horizontal beam is obtained by injecting compressed air into a hot spinning pipe. Holes can be drilled in metal foil with a ruby laser beam focused by a gas lens.
22 citations
TL;DR: In this paper, the phase match parameters of a KTP crystal at 1.064 μm were calculated, and from these they obtained the optimum phase match parameter, θ = 90°, φ = 23.6°, with an effective nonlinear coefficient 1.75 × 10-8 esu.
Abstract: Precise values of refractive indices, measured by the auto-collimation method, are presented in this paper. The phase match parameters of a KTP crystal at 1.064 μm were calculated, and from these we obtained the optimum phase match parameters, θ = 90°, φ = 23.6°, with an effective non-linear coefficient 1.75 × 10-8 esu. This is the best agreement with an experimental result ever reported.
15 citations
TL;DR: In this article, a spatial averaging technique to improve depth ranging resolution by projecting an astigmatic light beam and imaging through a wide-aperture linear array detector is described, and theoretical computations and experimental results are presented and discussed.
Abstract: A spatial averaging technique to improve depth ranging resolution by projecting an astigmatic light beam and imaging through a wide-aperture linear array detector, is described. Theoretical computations and experimental results are presented and discussed.
14 citations
9 citations
TL;DR: In this paper, a variable wavelength interferometric (VAWI) method was proposed for testing birefringent retarders using a double-refracting interferometer.
Abstract: A variable wavelength interferometric (VAWI) method was previously proposed for testing birefringent retarders using a double-refracting interferometer If the spectral dispersion of double refraction of the interferometer is identical with, or similar to, that of the birefringence of the retarder under study, then the VAWI method takes a specific form, referred to as object-adapted (or adaptive) variable wavelength interferometry (AVAWI), which enables the phase retardation (δ) and/or the thickness ( t ) of the birefringent retarders to be measured very precisely by using relatively simple means This new approach is quite simple in its mode of operation and gives results (δ and/or t ) with the relative error as low as 001%
9 citations
TL;DR: The underlying principles of the design, its operational features and its implementation in the Microdome is described, which results in a projection system with greater optical simplicity, higher reliability and reduced power and cooling requirements over similar laser projectors.
Abstract: A novel laser TV projection display has been developed by PA Technology employing the Scophony system with acousto-optic modulators and pulsed lasers. This results in a projection system with greater optical simplicity, higher reliability and reduced power and cooling requirements over similar laser projectors. The technique has been successfully implemented in British Aerospace's Microdome missile training simulator. This paper describes the underlying principles of the design, its operational features and its implementation in the Microdome.
9 citations
TL;DR: In this paper, a new signal processing device with a microprocessor has been designed, which can be used for measurements in which the vibrating body cannot be loaded or is at a long distance.
Abstract: This paper introduces a heterodyne vibration measuring method: a new signal processing device with a microprocessor has been designed. The most important advantages of this method are that the vibrating amplitude and frequency of the object can be measured simultaneously, with a measuring accuracy of 1% and 0.5% respectively. Better heterodyne signals can be seen by using glass microspheres as scatterers. By using their strong backward scattering, the vibrations in non-optic axis directions can be measured. This method can be used for measurements in which the vibrating body cannot be loaded or is at a long distance.
8 citations
TL;DR: In this paper, two transparencies which are placed in the two arms of a Mach-Zehnder interferometer with two orthogonal polarizers are subsequently added or subtracted by rotating an analyser inserted in the output beam.
Abstract: The present article reports a new optical method for real time addition or subtraction of two photographic images. Two transparencies which are placed in the two arms of a Mach-Zehnder interferometer with two orthogonal polarizers are subsequently added or subtracted by rotating an analyser inserted in the output beam. A linear combination of the amplitudes of the two images can also be observed for different orientations of the transmission axis of the analyser. Some experimental results are presented.
TL;DR: In this paper, the authors used holographic interferometry as a quantitative optical diagnostic of the soundboard of a harpsichord and obtained an accuracy of better than 170 nm.
Abstract: This paper presents an original piece of research using holographic interferometry as a quantitative optical diagnostic. The object under investigation was the soundboard of a harpsichord. The results obtained show that it is possible to measure the spatial vibrational behaviour of the whole soundboard with an accuracy of better than 170 nm. Several features which characterize the vibration behaviour of the soundboard have been visualized including a discontinuity created by a crack which has resulted in a phase change of the interferometric fringes. Finally, the theoretical model response of the harpsichord soundboard is determined and compared to our holographic measurement.
TL;DR: In this paper, a system based on a glass fluorescer was described, which writes the beam profile of a single shot KrF laser directly into computer memory and hence permits many powerful image processing routines.
Abstract: The properties of various glasses used as ultra-violet to visible image converters are investigated. A system is described, based on a glass fluorescer, which writes the beam profile of a single shot KrF laser directly into computer memory and hence permits many powerful image processing routines.
TL;DR: In this article, the optimum number and type of observation directions correspond to counting in the four semi-diagonals of the holographic plate and the associated errors range from 0.1-0.3 μm, for a counting inaccuracy of 1 8 − 1 4 of a fringe and increments of traction of 100 g to 1 kg of force.
Abstract: The use of a fringe-counting holographic interferometric technique for measuring small superficial displacements can present difficulties in determining the measurement inaccuracy. A useful general method is given here for the analysis of errors in displacement measurements. The optimum number and type of observation directions are determined and correspond to counting in the four semi-diagonals of the holographic plate. The technique, as applied to skull experiments, makes it possible to measure directly displacements of up to 20 μm, in the object plane parallel to the holographic plate. The associated errors range from 0.1–0.3 μm, for a counting inaccuracy of 1 8 – 1 4 of a fringe and increments of traction of 100 g to 1 kg of force.
TL;DR: An easy and accurate method to detect the kind of disarrangement and its magnitude in the adjustment process of a Mach-Zehnder interfermeter by means of an equilateral hyperbolic zone plate is explained in this paper.
Abstract: An easy and accurate method to detect the kind of disarrangement and its magnitude in the adjustment process of a Mach-Zehnder interfermeter by means of an equilateral hyperbolic zone plate is explained.
TL;DR: A generalized analysis of the building block optical system comprising a single holographic optical element for achieving simultaneous display of the spectrum and the image of an object in a single plane using the Vander Lugt operational notation is carried out.
Abstract: A generalized analysis, using the Vander Lugt operational notation, of the building block optical system comprising a single holographic optical element (HOE) for achieving simultaneous display of the spectrum and the image of an object in a single plane, has been carried out. The salient features of this analysis are: (1) it allows comprehensive characterization of the HOE, (2) it provides insights into the many possible configurations for the system, and (3) it explains the existing results in a consistent manner.
TL;DR: In this article, the authors analyzed the mode structure of a wideband radiofrequency excited waveguide CO 2 laser by using different waveguide diameters and optical cavities, and observed the phase shift of some linear polarized waveguide modes in the transition region between the guided and the free Gaussian propagation.
Abstract: We have analysed the mode structure of a wideband radiofrequency excited waveguide CO 2 laser by using different waveguide diameters and optical cavities. In particular we have observed the phase shift of some linear polarized waveguide modes in the transition region between the guided and the free Gaussian propagation.
TL;DR: In this paper, a method of measuring gas flow parameters, based on testing the gas flow by shock waves, is described, where the shock waves in the examined flow were produced by a pulsed laser beam focused on to the surface of an object.
Abstract: A method of measuring gas flow parameters, based on testing the gas flow by shock waves, is described. The shock waves in the examined flow were produced by a pulsed laser beam focused on to the surface of an object. To illustrate the method, experimental data are presented dealing with gas parameters on the surface of a free-flying object.
TL;DR: The concept of optical information processing is reviewed, the development of SLMs from their early beginnings is discussed, and a discussion of where the field is now, and where it is going in the next few years is discussed.
Abstract: Spatial light modulators (SLM) developed to date have fallen into one of two categories, optically addressed or electronically addressed. Each approach has its advantages and disadvantages, and successful implementation of optical processing in real world applications may depend upon a combination of the two. This article briefly reviews the concept of optical information processing, discusses the development of SLMs from their early beginnings, and concludes with a discussion of where the field is now, and where it is going in the next few years.
TL;DR: In this paper, a new speckle carrier technique is presented, which can solve the problem that the direction of the displacement vector is ambiguously determined when the point-wise method is used.
Abstract: A new speckle carrier technique is presented, which can solve the problem in one-beam laser speckle interferometry, that the direction of the displacement vector is ambiguously determined when the point-wise method is used. The method is very easy and convenient and the results are good. Some discussion about the relationship between the carrier frequency and the displacements is given.
TL;DR: Some prisms have been devised that use light incident at the polarizing angle and total internal reflection (TIR) to produce angular or lateral displacements on a p-type monochromatic collimated beam of polarized light, with minimum reflection losses.
Abstract: Some prisms have been devised that use light incident at the polarizing angle and total internal reflection (TIR) to produce angular or lateral displacements on a p-type monochromatic collimated beam of polarized light, with minimum reflection losses.
TL;DR: In this paper, a solution based on the difference amplification method, which uses the higher diffraction orders of a non-linearly recorded hologram, was proposed to evaluate aberrations caused by movement of the photographic emulsion.
Abstract: A real-time holographic interferometry technique is typically used in the evaluation of aberrations caused by movement of the photographic emulsion. However, this technique is insufficiently accurate when an emulsion, with strain which has been released prior to exposure, is used. A proposed solution is based on the difference amplification method, which uses the higher diffraction orders of a non-linearly recorded hologram.
TL;DR: In this paper, an alignment technique for a ring laser cavity is presented which is suitable for a resonator into which auxillary laser beams cannot pass, and the alignment technique is shown to be suitable for any resonator.
Abstract: An alignment technique for a ring laser cavity is presented which is suitable for a resonator into which auxillary laser beams cannot pass.
TL;DR: In this paper, the surface layer of a base material is melted and hard wear resistant carbide particles are injected into the melted pool to improve the wear resistance of the base material.
Abstract: Wear resistance can be improved by laser impregnation — the surface layer of a base material is melted and hard wear resistant carbide particles are injected into the melted pool. Previously, experiments were mainly performed in a vacuum chamber at a laser power of 10 kW. In this paper, results are presented of experiments carried out with 1.5 and 2.5 kW lasers at ambient atmospheric pressure. Laser impregnated layers show increased wear resistance of the order of 20–40 times for impregnated compared to untreated aluminium, and 5–20 times for impregnated compared to hardened carbon steels.
TL;DR: In this article, a possible configuration for the optical computer is outlined together with the current drawbacks associated with system elements, and consideration is given to devices and subsystems which are under investigation to provide building blocks for a future digital optical computer.
Abstract: In Part one recent developments in integrated optics and optoelectronic integration, which have been largely stimulated by the widespread implementation of glass fibre communication systems employing a lightwave carrier, were reviewed. In Part two, consideration is given to devices and subsystems which are under investigation to provide building blocks for a future digital optical computer. A possible configuration for the optical computer is outlined together with the current drawbacks associated with system elements.
TL;DR: In this paper, a variable area slit and photodetector combination was used to measure the thermal expansion of a mirror on a probe, which is positioned on both sample and reference rods, by uneven thermal expansions of the two materials.
Abstract: The light reflected from a mirror on a probe, which is positioned on both sample and reference rods, is rotated by uneven thermal expansions of the two materials. A simple method is described to measure this rotation and hence the thermal expansion using a variable area slit and photodetector combination. The method is capable of determining very low thermal expansions of ceramic materials with high precision and accuracy. A measurement sensitivity of 10 -6 for Δ L / L can easily be obtained.
TL;DR: In this paper, the usefulness of different monitor screen patterns for visualization and measurement of surface shapes is demonstrated, and some of the effects on drop shape production by the shape of the film on which the drop is held, the volume of the drop, and the type of liquid, wetting or nonwetting, are studied.
Abstract: Liquid drops may be used as lenses of short focal length, particularly in the ‘cleaning’ and shaping of low-power laser beams. The drops are small but usually have large surface slopes which can give large ray deflection angles. A study of their shapes requires an optical system which can cope with deflection angles of 45° or more. This can be achieved in a convenient and versatile manner by the use of a computer monitor screen as the light source. The usefulness of different monitor screen patterns for visualization and measurement of surface shapes is demonstrated. Some of the effects on drop shape production by the shape of the film on which the drop is held, the volume of the drop, and the type of liquid, wetting or non-wetting, are studied. For more spectacular effects, a colour monitor could be used.
TL;DR: In this article, the influence of the molecular weight of the far infra-red gas on the absorption of the pump energy is discussed, and the results show that the heavy molecules are most convenient for long pulse far infRA-red lasers.
Abstract: A high power, far infra-red laser, pumped by a long pulse high energy CO2 laser, has been developed to produce 8 μs pulses at 447 μm. The influence of the molecular weight of the far infra-red gas on the absorption of the pump energy is discussed. The results show that the heavy molecules are most convenient for long pulse far infra-red lasers.