Showing papers in "Journal of Modern Optics in 1982"
TL;DR: In this article, the reflection and transmission properties of moth eye antireflection surfaces are described, and are shown to be equal to those of the best multilayer antire-flection coatings.
Abstract: A ‘moth eye’ antireflection surface is a very fine array of protuberances which behaves as a gradation of refractive index, and which substantially reduces the reflectance. The reflection and transmission properties of such surfaces are described, and are shown to be equal to those of the best multilayer antireflection coatings.
676 citations
TL;DR: Results of the fitting of a conicoid equation to corneal shape data derived from a precision photokeratoscope show that the cornea is significantly asymmetric in both radius of curvature and asphericity.
Abstract: The anterior surface of the cornea is the major refracting element in the human eye. Knowledge of its shape and the variation of this shape throughout the population are important in calculations of the corneal contribution to ocular aberrations. Since the cornea is the surface on which the contact lens rests, the corneal shape is also of importance in contact lens design. this paper presents results of the fitting of a conicoid equation to corneal shape data derived from a precision photokeratoscope. Both rotationally symmetric and non rotationally symmetric form of the conicoid equation were developed. The results show that if the cornea is regarded as a rotationally symmetric conicoid, the conicoid is ellipsoidal but with insufficient asphericity to eliminate spherical aberration for distance vision. More importantly, the results show that the cornea is significantly asymmetric in both radius of curvature and asphericity
293 citations
TL;DR: The division-of-amplitude photopolarimeter (DOAP) as discussed by the authors is a light beam divided into four separate beams using a beamsplitter and two Wollaston prisms.
Abstract: To measure all four Stokes parameters of a light beam simultaneously, the beam is divided into four separate beams using a beamsplitter and two Wollaston prisms. Linear detection of the light fluxes of the four component beams gives four signals that determine the four Stokes parameters. This division-of-amplitude photopolarimeter (DOAP) is completely characterized by a wavelength-dependent 4 2 4 matrix that can be determined directly by calibration. The instrument has a fast response (that is limited only by the photodetectors) as it has no moving parts or modulation.
200 citations
TL;DR: In this article, the singular functions and singular values for coherent imaging are computed numerically and by means of these results it is shown that super-resolution, in the sense of improving on previous criteria in the presence of noise, can be achieved.
Abstract: In a previous paper, methods of singular function expansions have been applied to the analysis of coherent imaging when the object and image domains are allowed to differ. In this paper the method is extended to incoherent illumination, restricting the analysis to the aberration-free case. While singular functions and singular values for coherent imaging are related in a simple way to the prolate spheroidal functions and their eigenvalues, such relations do not exist for the incoherent imaging case. In spite of this difficulty many properties of singular functions and singular values are derived in this paper and asymptotic estimates are obtained in the limit of large space-bandwidth product. For small values of the space-bandwidth product, the singular values are computed numerically and by means of these results it is shown that super-resolution, in the sense of improving on previous criteria in the presence of noise, can be achieved.
113 citations
TL;DR: The conventional concept of OTF cannot be applied to sampled imaging systems which exhibit aliasing effects, but the concept can be extended to this class of systems if the condition of isoplanatism is redefined, and if only a limited range of spatial frequencies is considered.
Abstract: The conventional concept of OTF cannot be applied to sampled imaging systems which exhibit aliasing effects. This paper shows that the concept can, however, be extended to this class of systems if the condition of isoplanatism is redefined, and if only a limited range of spatial frequencies is considered. Parameters to quantify the amount of aliasing are also suggested, and these can be easily measured at the same time as the OTF, and used with the OTF to give a full description of the image transfer characteristics of aliased, sampled systems.
88 citations
TL;DR: In this article, the authors use a rigorous formalism for lossy lamellar gratings to establish the validity of the quasistatic approximation for this structure in the limit as its period d becomes much finer than the wavelength u of incident light.
Abstract: We use a rigorous formalism for lossy lamellar gratings to establish the validity of the quasistatic approximation for this structure in the limit as its period d becomes much finer than the wavelength u of incident light. In the quasistatic limit, the grating behaves like a uniaxial film in its interaction light, its principal refractive indices being given by simple formulae. We show numerically that the quasistatic model of the grating is accurate to better than an absolute tolerance of 0·005 if u/d>40. In the case of perfectly conducting lamellar gratings, we show that the model of a uniaxial film cannot be used in the quasistatic limit. This invalidates the optical model of Yeh for wire-grid polarizers.
75 citations
TL;DR: In this paper, an experiment in narrow spectral band speckle interferometry is described, which uses variations in the spectrum across the astronomical object under study, to obtain information of the object on the millisecond of arc scale.
Abstract: This paper describes an experiment in narrow spectral band speckle interferometry, which uses variations in the spectrum across the astronomical object under study, to obtain information of the object on the millisecond of arc scale. We plan to apply this experiment to the study of spectroscopic double stars, stellar rotation, spectroscopic and magnetic variable stars and other astronomical objects.
66 citations
TL;DR: In this article, a new technique for recording stress patterns called thermoelastic stress analysis (TSA) is described, which measures the distribution of stress on the surface of a structure under load, and the connection between stress concentration, mechanical design and safety.
Abstract: After discussions on the need to measure the distribution of stress on the surface of a structure under load, and the connection between stress concentration, mechanical design and safety, a new technique for recording stress patterns called thermoelastic stress analysis (TSA) is described. For given material constants, the change in temperature on the surface of a structure, subject to dynamic loading, is directly proportional to the change in stress at that point. A specially designed, high-sensitivity I.R. camera is described which can present a colour display of the distribution of stress which could arise from temperature variations as small as 0·001 K resulting from a few units of microstrain in metals. A selection of typical results obtained by recording the stress concentration on the surface of a model pedestal structure are given to illustrate how TSA could be used as an aid to design. The likely useful areas of application of TSA can be identified with the help of a list of the principal charac...
60 citations
TL;DR: In this paper, the statistical theory of coherent speckle patterns is compared to classical coherence theory, and it is shown that the Hanbury Brown and Twiss effect is directly analogous to the Coherence effect.
Abstract: The statistical theory of fully developed, coherent speckle patterns is compared to classical coherence theory. It is shown that speckle correlations are directly analogous to the Hanbury Brown and Twiss effect. On that background a unified description is given for a number of measurement techniques based on intensity correlation measurements in scattered laser light: holographic interferometry, speckle pattern interferometry, speckle photography, stellar speckle interferometry, laser Doppler velocimetry and intensity correlation spectroscopy.
58 citations
TL;DR: Gabor's expansion of a signal into a discrete set of properly shifted and modulated versions of an elementary signal is introduced, and a way to determine the expansion coefficients is derived.
Abstract: Gabor's expansion of a signal into a discrete set of properly shifted and modulated versions of an elementary signal is introduced, and a way to determine the expansion coefficients is derived. The way in which the expansion coefficients are transformed when the signal propagates through a linear system, is described; in particular, the basic coherent-optical system consisting of a 4f-arrangement with rectangular apertures in the input and the Fourier plane, is considered. As a result, the well-known property that a signal which is roughly limited both in space and in spatial frequency has a number of complex degrees of freedom which is equal to the space-bandwidth product, is re-established.
53 citations
TL;DR: An interference version of the confocal microscope, which has several advantages over a conventional interference microscope, is described in this article, and comparative results from different modes of operation are presented.
Abstract: An interference version of the confocal microscope, which has several advantages over a conventional interference microscope, is described, and comparative results from different modes of operation are presented.
TL;DR: In this paper, the authors answer Mandel's comments on a model of photon counting which they proposed earlier, by showing how it may be applied to some typical open systems, and clarify the circumstances under which Man...
Abstract: We answer Mandel's comments on a model of photon counting which we proposed earlier, by showing how it may be applied to some typical open systems. We also clarify the circumstances under which Man...
TL;DR: In this article, the authors present a volume of holography and volume gratings for the International Journal of Optics: Vol. 29, No. 5, pp. 592-592.
Abstract: (1982). Volume Holography and Volume Gratings. Optica Acta: International Journal of Optics: Vol. 29, No. 5, pp. 592-592.
TL;DR: For gratings having an arbitrary symmetric profile, it was shown in this article that when the period becomes much finer than the wavelength, the grating becomes equivalent to a graded uniaxial layer.
Abstract: For gratings having an arbitrary symmetric profile, we prove that when the period becomes much finer than the wavelength the grating becomes equivalent to a graded uniaxial layer. We show for one p...
TL;DR: In this article, the authors considered second-harmonic generation by a nonlinear crystal placed in an empty resonant cavity and pumped by an external coherent field and showed that the stationary state loses its stability through a Hopf bifurcation when the input intensity reaches a critical value.
Abstract: We consider second-harmonic generation by a non-linear crystal placed in an empty resonant cavity and pumped by an external coherent field. It was recently predicted that the stationary state loses its stability through a Hopf bifurcation when the input intensity reaches a critical value. A new amplitude self-modulated state then arises. We construct explicitly this new time-periodic solution and prove its stability in the vicinity of the transition point. As the input intensity is further increased, numerical investigations indicate a new transition to another time-periodic solution; this transition involves an hysteresis cycle. The two periodic solutions differ by the number of maxima in one period: at low input intensity, there is one maximum per period, whereas at high input intensity there are two.
TL;DR: In this article, anomalous-diffraction (AD) light-scattering approximation is used to calculate the small-angle light scattering (SALS) by a spherulite placed between two linear polarizers.
Abstract: Using the anomalous-diffraction (AD) light-scattering approximation, a relationship is derived between the scattering matrix of an object and its full Jones' matrix. This allows scattering to be calculated for dielectric objects having any kind of optical anisotropy, e.g. birefringent or optically active particles. The theory is used to calculate the small-angle light scattering (SALS) by a spherulite placed between two linear polarizers. Serious disagreements are found between the AD theory and the currently accepted theory of SALS based on the Rayleigh-Gans-Debye approximation.
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TL;DR: Pinspeck images are visible during a solar eclipse, when the shadows of objects appear crescent-shaped as mentioned in this paper, demonstrating unlimited depth of field, freedom from distortion and large angular field.
Abstract: By complementing a pinhole to produce an isolated opaque spot, the light ordinarily blocked from the pinhole image is transmitted, and the light ordinarily transmitted is blocked. A negative geometrical image is formed, distinct from the familiar 'bright-spot' diffraction image. Anti-pinhole, or 'pinspeck' images are visible during a solar eclipse, when the shadows of objects appear crescent-shaped. Pinspecks demonstrate unlimited depth of field, freedom from distortion and large angular field. Images of different magnification may be formed simultaneously. Contrast is poor, but is improvable by averaging to remove noise and subtraction of a d.c. bias. Pinspecks may have application in X-ray space optics, and might be employed in the eyes of simple organisms.
TL;DR: In this paper, the path differences between wave-groups of white light are introduced at the emission stage by using a set of birefringent quartz plates and transverse electro-optic modulators acting as delay lines.
Abstract: Communication by spectral modulation of white light was proposed a few years ago and has been demonstrated via electro-optic techniques. Compared with conventional modulation intensity systems, the present method takes advantage of simultaneous transmission and reception of analogue signals without any electronic coding of the information. The information is carried along the chosen channel in the form of time-varying path differences between wave-groups of white light. In the device proposed here, these path-differences are introduced at the emission stage by using a set of birefringent quartz plates and transverse electro-optic modulators acting as delay lines. The propagation medium is the atmosphere (steady or turbulent) or any type of light pipe (e.g. a fibre bundle). At the reception stage, the signals are led to a detector PIN array after decoding via Fourier transform spectroscopy; another set of birefringent quartz plates introduces path-differences tuned on and matched with the various carriers....
TL;DR: The results of a preliminary theoretical investigation of the statistical properties of electromagnetic radiation scattered by a randomly grooved surface are presented in this article, where the contrast of the intensity pattern is calculated for both near and far-field geometries, and it is shown that the full probability density of intensity fluctuations can be obtained exactly in the far field specular direction.
Abstract: The results of a preliminary theoretical investigation of the statistical properties of electromagnetic radiation scattered by a randomly grooved surface are presented. The contrast of the intensity pattern is calculated for both near-and far-field geometries, and it is shown that the full probability density of intensity fluctuations can be obtained exactly in the far-field specular direction.
TL;DR: In this article, the phenomenological theory of nonlinear optical activity and nonlinear circular dichroism is developed and exact analytical solutions are found in the planewave approximation which make it possible to analyse conditions for observation of contributions of the aforementioned effects.
Abstract: The phenomenological theory of nonlinear optical activity and nonlinear circular dichroism is developed. Exact analytical solutions are found in the planewave approximation which make it possible to analyse conditions for observation of contributions of the aforementioned effects.
TL;DR: In this paper, a comprehensive survey of the chromatic correction, imaging quality, and spherochromatic aberrations of imaging systems consisting of two or three holographic optical elements (HOE) is presented.
Abstract: This paper gives a comprehensive survey of the chromatic correction, imaging quality, and spherochromatic aberrations of imaging systems consisting of two or three holographic optical elements (HOE...
TL;DR: In this article, techniques and applications of image understanding are discussed. But the authors focus on image understanding in the context of image recognition, and do not consider image recognition in the field of image analysis.
Abstract: (1982). Techniques and Applications of Image Understanding. Optica Acta: International Journal of Optics: Vol. 29, No. 11, pp. 1456-1456.
TL;DR: In this paper, double-exposure techniques and time average exposure were presented for real-time deformation displacement and vibration analysis and for contour line holography using a two-wavelengths method.
Abstract: Electro-optical crystals are used for real-time holography, optical data storage, optical information processing and more recently for speckle applications. Many ferro-electric materials were investigated, the Bi12 SiO20 (BSO), a cubic, para-electric and electro-optic material was found to be very useful for real-time holographic interferometry and speckle applications. For the application of the BSO in real-time metrology, the crystals is usually biased with a transverse electric field in the 110 or 100 crystallographic direction. Illuminating the crystal with spatially structured information in the 110 direction as a result of a hologram or speckle pattern, a space charge field is built up, leading to a refractive index variation in the crystal. Double-exposure techniques and time average exposure will be presented for real-time deformation displacement and vibration analysis and for contour line holography using a two-wavelengths method. Young's fringes of double-exposed, or in the time-average recorde...
TL;DR: In this paper, the authors present a model of the lattice dynamics and models of interatomic forces, which they call Phonons: Theory and Experiments I (Phonons).
Abstract: (1982). Phonons: Theory and Experiments I. Lattice Dynamics and Models of Interatomic Forces. Optica Acta: International Journal of Optics: Vol. 29, No. 12, pp. 1586-1586.
TL;DR: In this article, the time-dependent spectrum of non-stationary radiation is characterized by the timedependent input spectrum and the spectral coordinate (output spectrum) is calculated as a function of the input spectrum.
Abstract: The measurement of the time-dependent spectrum of non-stationary radiation is of interest, for instance, in the field of ultrashort-time spectroscopy using picosecond lasers The incident non-stationary radiation is characterized by the time-dependent input spectrum The electric field strength of the radiation in the exit plane of a grating spectrometer and of a prism spectrometer is analysed in terms of its dependence on time and on the spectral coordinate The action of the grating spectrometer is regarded as a special case of diffraction at an arbitrary diaphragm The intensity registered by a square-law detector as a function of time and the spectral coordinate (output spectrum) is calculated as a function of the input spectrum The input spectrum can be determined from the output spectrum by mathematical operations for cases important in practise (very short light-pulses, intrinsically stationary radiation) Moreover, the conditions are investigated under which the output spectrum resembles the inpu
TL;DR: Three- and four-dimensional signals can be replaced by two-dimensional sequences of sectional images if sampling in one or two dimensions is practicable, and higher-dimensional filter operations can be performed by means of two- dimensional filter methods, e.g. coherent optics.
Abstract: Three- and four-dimensional signals can be replaced by two-dimensional sequences of sectional images if sampling in one or two dimensions is practicable. The convolution of such sequences yields, under certain conditions, the sequence representation of the three- or four-dimensional convolution result. Thus higher-dimensional filter operations can be performed by means of two-dimensional filter methods, e.g. coherent optics, whose parallel computing power matches the usually high space-bandwidth products (SBP) of such sequences. The possible throughput of coherent-optical setups is estimated. Experimental results for three-dimensional filter operations are shown.
TL;DR: In this article, a detuned interference filter is placed between the diffracting object and the holographic plate, which allows the relative amplitudes of the reference and the object beam to be controlled.
Abstract: As an application of Fourier filtering in the object space, an in-line far-field holography configuration is considered where a detuned interference filter is placed between the diffracting object and the holographic plate. With suitable adjustment of the parameters, such a technique allows the relative amplitudes of the reference and the object beam to be controlled. This results in a modified visibility distribution of the interference fringes, and finally in a faster aperture that better defines the position in depth of the diffracting object during reconstruction. Theoretical computations and preliminary experimental results are presented.
TL;DR: A new type of filter called the optimum circular symmetrical filter is presented and its uses in optical pattern recognition are described, which makes the recognition process fully parallel, without input scanning or coordinate transformation, no matter where and in what orientation the patterns to be recognized are located in the input plane.
Abstract: A new type of filter called the optimum circular symmetrical filter is presented and its uses in optical pattern recognition are described. The filters can be realized by optical or computer-generated holography. They are space-invariant and rotation-invariant, and are optimized in the mean-square sense. This makes the recognition process fully parallel, without input scanning or coordinate transformation, no matter where and in what orientation the patterns to be recognized are located in the input plane. Multiple use of those filters can further improve system recognition ability. By using them jointly with other methods of linear combinations of matched filters, more advanced systems can be obtained.