Showing papers in "Optics and Laser Technology in 1976"
TL;DR: In this article, the authors describe the basic physical principles of defocused speckle photography, and how tilt (differential) topology variations on a scatter surface may be separated from linear displacements.
Abstract: This paper describes the basic physical principles of defocused speckle photography, and how tilt (differential) topology variations on a scatter surface may be separated from linear displacements. Several rather special features about the scattering process have been revealed, such as the laser source distance from the scatter surface must be considered as well as the light incidence angle. Also, the surface must be treated as mirror facet discontinuities for linear displacements using ray and intensity analogies, and surface topology must be treated in terms of phase and pathlength changes, and a continuous smooth surface. The complementary relationship between focused speckle photography and defocused (topological) speckle photography is shown using specially developed separation techniques. This demanded a detailed look at the ‘speckle process’. The basic physical principles, together with an appropriate analysis technique for the developed speckle photographs, have enabled very small faults and indentations on engineering structures to be detected and measured.
84 citations
TL;DR: In this paper, the specular and diffuse reflection from ground and lapped surfaces using helium-neon laser light is analyzed. But the authors focus on the surface finish of metals.
Abstract: Optical methods are available for evaluating the surface finish of metals. This paper covers measurements of the specular and diffuse reflection from ground and lapped surfaces using helium-neon laser light. The specular reflection gives information on the probability distribution of roughness height, while the diffuse reflection depends on the roughness slope distribution.
35 citations
33 citations
TL;DR: In this article, the basic principles of plane strain measurement using speckle pattern interferometry are summarized and a detailed description of a new design of interferometer which provides the required geometries is presented.
Abstract: The basic principles of plane strain measurement using speckle pattern interferometry are summarized. In the general case it is shown that the determination of the total plane strain field requires a minimum of two object illumination goemetries. A detailed description of a new design of interferometer which provides the required geometries is presented. Interferograms which demonstrate typical applications of the interferometer are interpreted.
33 citations
TL;DR: In this paper, a simple and accurate technique for measuring the spot size of Gaussian laser beams by scanning the beam with an opaque ribbon is proposed, and the usefulness of this technique is verified experimentally.
Abstract: A simple and accurate technique for measuring the spot size of Gaussian laser beams by scanning the beam with an opaque ribbon is proposed. The usefulness of this technique is verified experimentally.
31 citations
TL;DR: The state of the art of holographic interferometry in medicine is reviewed and areas in which the technique may find applications in the future are indicated.
Abstract: This paper reviews the state of the art of holographic interferometry in medicine. Areas in which the technique may find applications in the future are indicated.
24 citations
TL;DR: In this paper, the fundamental methods for producing holograms suitable for automatic analysis are given, with particular emphasis on exposure control, and in-line holography is demonstrated to be a powerful tool in the assessment of aerosols and two dissimilar applications are described.
Abstract: Basic requirements for any apparatus designed to measure aerosol particles are reviewed. In-line holography is demonstrated to be a powerful tool in the assessment of aerosols and two dissimilar applications are described. The fundamental methods for producing holograms suitable for automatic analysis are given, with particular emphasis on exposure control.
22 citations
TL;DR: In this paper, a scan converter memory has been used for real-time and double-exposure tv-speckle interferometry, and some of the features of the memory have been tested experimentally.
Abstract: A scan converter memory has been used for real-time and double-exposure tv-speckle interferometry. Some of the features of the memory have been tested experimentally.
16 citations
TL;DR: In this article, a laser Doppler microscope, consisting of optical and signal-analysing systems, has been developed for measuring flow velocities, both in a small square cell in a venule, and in a capillary over the web of a frog's foot.
Abstract: A laser Doppler microscope, consisting of optical and signal-analysing systems, has been developed. Flow velocity can be measured with an extremely high spatial resolution over an area of up to 10μm in diameter. The optical system consists of a microscope having two types of penetrative and reflective systems. On the basis of the characteristic analysis of Doppler beat signals from the laser Doppler microscope, the signal-analysing system, which uses a tracking filter together with a digital-hold element and a time-to-pulse height converter, has been found to be the most suitable for analysing beat signals. Some experimental results obtained using the laser Dopller microscope for measuring flow velocities, both in a small square cell in a venule, and in a capillary over the web of a frog's foot are presented.
13 citations
TL;DR: In this article, the display of sequences of holographic records of an event developing in time may be facilitated by transforming the original holographic record into a single multiplex hologram, which results in a reflecting phase element located at a plane near the reconstructed images.
Abstract: Some work with scatter plate holographic systems is reviewed, proceeding from single exposure recordings of transilluminated amplitude distributions to time resolved recordings of three-dimensional phase distributions. The display of sequences of holographic records of an event developing in time may be facilitated by transforming the original holographic records into a single multiplex hologram. An effective form of this techniquw is described, it results in a single reflecting phase element located at a plane near the reconstructed images. Reconstructions belonging to separate instants of time are recovered by selection in the pupil plane.
TL;DR: A new, small and safe, high intensity illuminator is described together with possibilities of improved light transmission and the first results obtained using a small lightweight 35 mm full frame camera with motorized film transport, as well as with a small 16 mm movie camera.
Abstract: Various light sources (illuminators), light transmitters, and recording apparatus are listed, and the shortcomings or inefficiencies of each group are analysed. A new, small and safe, high intensity illuminator is described together with possibilities of improved light transmission. The first results obtained using a small lightweight 35 mm full frame camera, with motorized film transport, as well as with a small 16 mm movie camera are mentioned. Finally, a miniature colour vidicon tv camera for endoscopic purposes is described.
TL;DR: In this article, the importance of several pertinent parameters are discussed in specifying metal mirrors for high energy laser systems and the typical and the state-of-the-art characteristics presently available.
Abstract: Several pertinent parameters are frequently overlooked in specifying metal mirrors for high energy laser systems. This report outlines the importance of those parameters and describes both the typical and the state-of-the-art characteristics presently available.
TL;DR: In this article, a method of holographic interferometry which uses an amplitude-modulated reference wave is proposed for investigating vibration phases, which are characterized by a function J 2 1 (α cos 2 Δ, where α and Δ are related to vibration amplitudes and phases on object points, respectively.
Abstract: A method of holographic interferometry which uses an amplitude-modulated reference wave is proposed for investigating vibration phases. Sinusoidal amplitude modulation of a reference wave yields hologram fringes which are characterized by a function J 2 1 ( α ) cos 2 Δ , where α and Δ are related to vibration amplitudes and phases on object points, respectively. The resultant fringes indicate that vibration amplitude information and phase information are stored separately. The phase information of the vibration is easily obtained as brightness variations of the fringes, independently of the amplitude information.
TL;DR: In this paper, a model of the production of the laser hole has been developed which is simple to understand, easy to apply, and sufficiently accurate for most practical purposes, leading to the development of an alternative explanation for the occurence of molten droplets which are spattered in all directions when the laser is fired.
Abstract: This paper is based upon experience gained with an instrument which has been developed at Marchwood Engineering Laboratories for measuring the thickness of magnetite layers on mild steel surfaces in hostile (hot and highly radioactive) environments. It is thought that the understanding of the interaction of powerful pulses of laser light with magnetite which has been gained in this work could have applications to a much wider field. A model of the production of the laser hole has been developed which is simple to understand, easy to apply, and sufficiently accurate for most practical purposes. The model differs substantially from the generally accepted form and has led to the development of an alternative explanation for the occurence of molten droplets which are spattered in all directions when the laser is fired. A technique for measuring the sulphur content of steels using mass spectrometry is also described.
TL;DR: In this article, a system for simultaneously measuring the three orthogonal components of a velocity vector is described, which uses a laser beam passing twice through the region of flow under investigation.
Abstract: A device for simultaneously measuring the three orthogonal components of a velocity vector is described. The system uses a laser beam passing twice through the region of flow under investigation. This allows one to determine the third component using only forward scattering. Vector diagrams which explain the mode of operation and experimental signals are given.
TL;DR: In this article, the use of a scanning Fabry-Perot interferometer of variable length (variable resolution) for investigating the output of a cw CO laser was reported.
Abstract: The use of a scanning Fabry-Perot interferometer of variable length (variable resolution) for investigating the output of a cw CO laser is reported. Under experimental conditions required to achieve maximum power it was found that the laser output consisted of two or more simultaneously occuring transitions due to the overlapping nature of the vibration- rotation bands. The frequency differences between these transitions were measured to an accuracy of ≲ 0.01 cm -1 . Operation of the CO laser on a single vibration-rotation transition was obtained by controlling the laser gain with the experimental variables of discharge pressure, gas temperature, and optical alignment. An alternative approach of obtaining monochromatic radiation, by using a Fabry-Perot interferometer as a frequency selective filter external to the CO laser, is reported.
TL;DR: In this article, the authors discuss sealing glasses, their properties, and their applications in the manufacturing of electronic displays. But their focus is on the sealing glass and its relationship to other components in the device.
Abstract: A key element in the manufacture of virtually any kind of electronic display is the sealing glass and its relationship to other components in the device. This paper discusses sealing glasses, their properties, and their applications.
TL;DR: In this article, the properties and main features of a cataphoretic He-Cd laser are presented, and several important details of laser tube design, eg measures to achieve a long lifetime, are reported.
Abstract: The properties and main features of construction of a cataphoretic He-Cd laser are presented. Several important details of laser tube design, eg measures to achieve a long lifetime, are reported. Due to its short wavelength and reliability the He-Cd laser proved to be useful for testing and evaluating the single exposure technique, compared or combined with the double exposure technique. The single exposure technique provides information of instabilities or vortexes in gaseous flows, examples of which are given.
TL;DR: A pyroelectric video tube which transforms a thermal image into a CRO display is useful in a number of experiments as discussed by the authors, and a few applications in usually difficult areas have been selected as examples.
Abstract: A pyroelectric video tube which transforms a thermal image into a CRO display is useful in a number of experiments. A few applications in usually difficult areas have been selected as examples. Text-book demonstrations in either optics or thermodynamics are often easier to do in the infra-red than in the visible. Applications include recording mode patterns of lasers with cw powers as low as 1 mW. The tubes are also useful in controlling the thickness and parallelism of infra-red flats which are apaque in the visible but transparent in parts of the infra-red spectrum.
TL;DR: In this article, the variation of the light scattered by mixtures of liquid crystals under pressure variations has been studied and the best results were obtained with a mixture of cholesterics and nematics.
Abstract: The variation of the light scattered by mixtures of liquid crystals under pressure variations has been studied. The best results are obtained with a mixture of cholesterics and nematics. The application of the phenomena to blood pressure measurement is considered.
TL;DR: In this article, two types of achromatic Schmidt corrector plate are described; both give an on-axis Strehl number S ⪆ 0.8 over an extended wavelength region.
Abstract: Two types of achromatic Schmidt corrector plate are described; both give an on-axis Strehl number S ⪆ 0.8 over an extended wavelength region. It is found that this specification can only be achieved by combining a positive and a negative plate and by restricting the speed ratio D/N3 of the system. The theory is illustrated by numerical examples.
TL;DR: In this paper, the effect of fiber bending on the passage of a laser beam through a cladded plastic optical fiber has been investigated and it was shown that the additional loss is determined by the bending radius, the locus of a bend, and the aperture angle of the applied launching system.
Abstract: The effect of fibre bending on the passage of a laser beam through a cladded plastic optical fibre has been investigated. Results indicate that the additional loss is determined by the bending radius, the locus of a bend, and the aperture angle of the applied launching system.
TL;DR: In this paper, a multiple laser beam probe for sizing and velocity measurements in turbulent media is presented in the case of thermal turbulent convection in a model buble chamber, where the probe is used to measure the size and velocity of the media.
Abstract: Deatils are given of a multiple laser beam probe for sizing and velocity measurements in turbulent media. Sample results are presented in the case of thermal turbulent convection in a model buble chamber.
TL;DR: In this paper, the Fourier transform method is used to calculate the electric field of the astigmatic gaussian beam which appears when an incident stigmatic Gaussian beam is refracted at the interface between media with different refractive indices.
Abstract: The Fourier transform method is used to calculate the electric field of the astigmatic gaussian beam which appears when an incident stigmatic gaussian beam is refracted at the interface between media with different refractive indices. A beam parameter transformation law is derived which shows that the beam parameters of the refracted astigmatic beam can be calculated from the beam parameters of the incident stigmatic beam and the angles of incidence and refraction. An heuristic derivation of the transformation law based on geometrical optics is also given. The application of the law is illustrated by determining the plane parallel plate astigmatism.