Showing papers in "Applied Optics in 1967"
IBM1
TL;DR: A theory for binary holograms is developed that is equivalent in terms of image reconstruction with ordinary holograms, proven theoretically and verified experimentally.
Abstract: When a hologram is desired from an object which does not exist physically but is known in mathematical terms, one can compute the hologram. An automatic plotter will make a drawing at a large scale which is then reduced photographically. Since the drawing can contain only black and white areas, we have developed a theory for binary holograms. They are equivalent in terms of image reconstruction with ordinary holograms. This has been proven theoretically and verified experimentally.
834 citations
TL;DR: In supplement to Edlén's recently revised formula for relative refractivity, the density dependence of refractive index is re analyzed and new formulas are presented which are more useful over a wide range of pressure, temperature, and composition than any presently available.
Abstract: The theoretical background and present status of formulas for the refractive index of air are reviewed. In supplement to Edlen's recently revised formula for relative refractivity, the density dependence of refractive index is reanalyzed. New formulas are presented for both phase and group refractive index which are more useful over a wide range of pressure, temperature, and composition than any presently available. The application of the new formulas to optical distance measuring is briefly discussed.
543 citations
TL;DR: In this analysis, the effects of possible excited state absorption at the irradiating wavelength are considered and are shown to give rise to a nonsaturable component of the absorption coefficient.
Abstract: This paper contains an analysis of the behavior of saturable filters, based on models with simple energy level structures. In this analysis, the effects of possible excited state absorption at the irradiating wavelength are considered and are shown to give rise to a nonsaturable component of the absorption coefficient. Expressions for the steady-state transmission of an optically thick saturable absorber, and for the temporal response of an optically thin absorber, are derived. The question of homogeneous vs inhomogeneous broadening of the absorption line is discussed, and it is suggested that spectral hole burning may occur in a thermally broadened line at a sufficiently high irradiance level. The desirable features of a saturable absorber for use in a Q-switched laser system are briefly described, and it is shown how the usual rate equations for a laser system may be amended to include the effects of an intracavity saturable filter.
323 citations
TL;DR: Three special cases of the general equation for the efficiency of an integrating sphere with a nonuniform coating are examined for the basic applications of integrating spheres as mixing mechanisms in hemispherical reflectance measurements and in absolute reflectance techniques.
Abstract: A general equation is developed for the efficiency of an integrating sphere with a nonuniform coating. The only assumptions are that the interior is a perfect sphere and that all areas reflect perfectly diffusely. Three special cases of the general equation are examined for the basic applications of integrating spheres as mixing mechanisms in hemispherical reflectance measurements and in absolute reflectance techniques.
206 citations
TL;DR: In this paper, photoionization yield and absorption coefficient of nitric oxide were measured at many wavelengths in the region 580-1350 A. H2 emission and helium continuum sources were used with a 1-m monochromator.
Abstract: Photoionization yield and absorption coefficient of nitric oxide were measured at many wavelengths in the region 580–1350 A. H2 emission and helium continuum sources were used with a 1-m monochromator. Absolute intensity measurements were based on a calibrated thermocouple.
161 citations
TL;DR: The basic principles of the use of the Fraunhofer (far field) hologram are described for both the recording of the hologram and the reconstruction of the particle distribution.
Abstract: The basic principles of applying hologram techniques to the problem of particle size determination have received considerable attention over the past year. In this paper the basic principles of the use of the Fraunhofer (far field) hologram are described for both the recording of the hologram and the reconstruction of the particle distribution. Factors affecting the sample volume depth and particle size range are discussed. Typical results are shown.
151 citations
Journal Article•
TL;DR: H emission and helium continuum sources were used with a 1-m monochromator and absolute intensity measurements were based on a calibrated thermocouple.
Abstract: Photoionization yield and absorption coefficient of nitric oxide at various wavelengths in 580-1350 angstrom region, using H sub 2 emission sources
146 citations
TL;DR: A very efficient method for the calculation of Mie cross sections for absorbing particles is discussed and the value of Q(sca) is found to be proportional to n(2) over a considerable range of values which are specified.
Abstract: A very efficient method for the calculation of Mie cross sections for absorbing particles is discussed It is used to calculate an extensive set of curves which illustrate the dependence of the efficiency factors Q for absorption and scattering on the size parameter x and on n1 and n2 (the real and imaginary parts of the index of refraction) The value of Qabs is found to be proportional to n2 over a considerable range of values which are specified As n2 increases, Qsca first decreases to a minimum value and then passes through a maximum, when x ≫ 1 and for most values of n1 The half-width of the angular intensity function is calculated over a range of values of n1 and n2 This half-width varies as x−1 and x ≥ 10 and is relatively insensitive to the values of n1 and n2
139 citations
TL;DR: A method of making such a grid polarizer by photolithographic techniques is described, and measurements on a device suitable for use at wavelengths between 20 micro and several hundred microns are presented.
Abstract: The design of a grid polarizer is discussed and the effect of supporting it on various substrates is evaluated using a transmission line analogy. A method of making such a grid polarizer by photolithographic techniques is described, and measurements on a device suitable for use at wavelengths between 20 micro and several hundred microns are presented. Their performance compares favorably with polarizers made by other methods.
135 citations
TL;DR: A dynamic volumetric display technique is described in which a vibrating membrane mirror is used in conjunction with an appropriate two-dimensional pattern generator to generatevolumetric figures which include a simulated air traffic control situation display and a mathematical surface.
Abstract: A dynamic volumetric display technique is described in which a vibrating membrane mirror is used in conjunction with an appropriate two-dimensional pattern generator. The mirror can be driven electrostatically or by a loudspeaker and causes the virtual image of the pattern surface to sweep out a volume of image space. The two-dimensional pattern is a repetitively time-varying one and can be generated by stroboscopic optical projection, by a computer, or other means. The volumetric figures which were generated include a simulated air traffic control situation display and a mathematical surface.
134 citations
TL;DR: A relative method, where, with the aid of fringes of superposition, the fringe separation is subdivided equidistantly thus achieving an increase of measuring precision, and an absolute method which determines the deviations of a surface from ideal planeness along arbitrary central sections, without a liquid surface.
Abstract: Interference methods are reviewed-particularly those developed at the German Academy of Sciences in Berlin-with which the deviations of an optically flat surface from the ideal plane can be measured with a high degree of exactness One aid to achieve this is the relative methods which measure the differences in planeness between two surfaces These are then used in the absolute methods which determine the absolute planeness of a surface This absolute determination can be effected in connection with a liquid surface, or (as done by the authors) only by suitable evaluation of relative measurements between unknown plates in various positional combinations Experimentally, one uses two- or multiple-beam interference fringes of equal thickness(1) or of equal inclination The fringes are observed visually, scanned, or photographed, and in part several wavelengths or curves of equal density (Aquidensiten) are employed The survey also brings the following new methods: a relative method, where, with the aid of fringes of superposition, the fringe separation is subdivided equidistantly thus achieving an increase of measuring precision, and an absolute method which determines the deviations of a surface from ideal planeness along arbitrary central sections, without a liquid surface, from four relative interference photographs
TL;DR: Experimental refractive indices of silicon, germanium, and fused quartz are presented, determined by these methods from data obtained with the Aerospace lamellar grating interferometer.
Abstract: For many years channel spectra, caused by multiple reflections of light between the faces of flat samples of optical material, have been used to determine refractive indices. Interferometers are excellent for this measurement, particularly in the far ir spectral region where their superior sensitivity and spectral resolution are required. The theory of the method is developed and the limitations are discussed. Experimentally determined refractive indices of silicon, germanium, and fused quartz are presented. These indices have been determined by these methods from data obtained with the Aerospace lamellar grating interferometer.
TL;DR: This report presents a brief resume of the underwater visibility problem and explains the circular polarization approach for improving contrast and shows that use of the polarization technique increased the visibility range in turbid water by at least a factor of two.
Abstract: This report presents a brief resume of the underwater visibility problem and explains the circular polarization approach for improving contrast. Experimental apparatus was set up at the Morris Dam facility of the U.S. Naval Ordnance Test Station, Pasadena Annex, and tests were conducted both with and without polarization. Results show that use of the polarization technique increased the visibility range in turbid water by at least a factor of two.
TL;DR: In this paper, the authors considered the effect of shot noise in photodetectors and showed that in the absence of a signal, the noise is mainly of (amplified) shot noise nature.
Abstract: The first part of this paper deals with general concepts of noise and response in photodetectors. The noise in photodetectors is of a fivefold nature: (i) noise produced by the blackbody photon field, J(b); (ii) noise produced by the ambient photon field J(a); (iii) noise associated with the signal J(s); (iv) spontaneous noise characteristic for the device and not associated with J(a); (v) noise associated with the circuitry or amplifiers. Concepts for the characterization of the noise are-the noise equivalent powers P'(eq.)lambda[lambda,f,Deltaf,A], P'(eq).lambda[lambda,f,Deltaf, A], P'(eq).T[T,f,Deltaf,A], and P(eg).T[T,f,Deltaf,A]; the photon limited noise equivalent powers P(eq).lambda[lambda,f,Deltaf,A], P(eg).T[T,f,Deltaf,A]; various detectivities Dlambda*[lambda,f], D(T)*[T,f]; the photon limited detectivities D(T)*{T(s), Omega(s)}, D(lambda)*{T(e), Omega(s)}, D(lambda)*{T(e), Omega(e)}, and Dlambda; dagger giving the ultimate limit attainable with a detector in radiative equilibrium; the noise figure F and the signal-to-noise ratio sigma/N. The merits and limitations of photon limited behavior are discussed and the theoretical detectivitis are calculated for various circumstances. If, in the absence of a signal, the noise stems mainly from the circuitry (class B), a characterization by P(eq) or D is largely arbitrary. Such is the case for photoemissive detectors and photoconductive insulators in the absence of bias light. In the event that the device operates and produces the main noise in the absence of a signal (class A), concepts like P(eq), D, F, are meaningful (semiconductors, p-n junctions, bolometers, PEM cells, etc.). Special attention has been given to introducing a consistent notation. In the second part of this paper we discuss two topics: some aspects of the photodetective conversion processes and the fluctuations of the photon field. The photodetective processes in emission diodes, junction diodes, photovoltaic cells, and avalanche diodes are simple. The noise is mainly of (amplified) shot noise nature. In photoconductors and PEM cells we must consider the collective carrier processes (unless the electrodes are blocking as in etectors in the thirties). Such processes do not fit too well a gain mechanism as has often been suggested as is testified by ambipolar sweep out and by the non-Poisson nature of generation-recombination (g-r) and transport fluctuations. The noise in a blackbody field is stated and the effect of imperfect absorbers is considered, involving stimulated emission. The commonly applied variance theorem leads to a degrading of the Boson factor. The noise of nonthermal photon fields is discussed following Mandel-Wolf, Alkemade, and Enns. In a nonthermal equilibrium state the effects of coherence and wave-interaction noise are manifest in the detector-output noise. In the final part the detectivity is derived for various devices. We first consider briefly photoemission devices, junction photodiodes, both in short-circuited and photovoltaic operation, and avalanche diodes. Avalanche multiplication decreases the detectivity by a factor G((1/2)), where G is the gain. A new derivation of Mclntyre's fomula-including the effect of a non-Poissonian Boson field is presented. The remainder is devoted to photoconductive detectors. Four classes are distinguished: intrinsic, minority trapping models (like PbS), two center models (like CdS), extrinsic semiconductors (like Ge: Au). The main theoretical results are stated and illustrative experimental results are discussed. Some remarks are made on hot electron photoconductivity and Landau level transitions in magnetically tuned InSb detectors.
TL;DR: Following Gerry but including electron impact mixing of laser levels, rate equations, coupled to the circuit equation, were solved under saturation approximations yielding excellent agreement with the saturation method and indicating the existence of an early oscillation which is not predicted by the saturation approximation method.
Abstract: It is shown that laser action at 3371 A terminates in times t < (τ32−1 + Y3)−1, where τ32 is the lifetime of the transition of C3πu → B3πg and Y3 is the electron depopulation rate of the upper laser level. Following Gerry but including electron impact mixing of laser levels, rate equations, coupled to the circuit equation, were solved under saturation approximations. Assuming a Seaton excitation cross section between laser levels, with an effective Gaunt factor of 0.25, power and pulse width were in good agreement with Shipman’s values. The rate equations were also solved without recourse to the saturation approximation yielding excellent agreement with the saturation method during most of the pulse and indicating the existence of an early oscillation which is not predicted by the saturation approximation method. Finally, the inclusion of the electron impact ionization of the nitrogen molecule from the excited state C3πu brings the pulse width to still better agreement with Shipman’s values.
TL;DR: Analysis of the kernel functions in the integral equation relating physical measurements to the drop size distribution reveals the number of useful independent inferences which can be made, with a specified error in measurement and from a given number of observations.
Abstract: Indirect measurement of parameters related to the drop size distribution in fog and cloud is discussed. Analysis of the kernel functions in the integral equation relating physical measurements (of transmission, forward scattering, and back scattering, respectively) to the drop size distribution reveals the number of useful independent inferences which can be made, with a specified error in measurement and from a given number of observations.
TL;DR: The characteristics of luminescence, excited by long wavelength radiation, in various solid systems (ionic crystals, activated by rare earth elements; semiconducting crystals with absorbed layers of sensitizer dye; green leaves of plants) have been investigated and it was found that in all cases studied the emission arises as a result of cooperative processes.
Abstract: The characteristics of luminescence, excited by long wavelength radiation, in various solid systems (ionic crystals, activated by rare earth elements; semiconducting crystals with absorbed layers of sensitizer dye; green leaves of plants) have been investigated. It was found that in all cases studied the emission arises as a result of cooperative processes, owing to interactions of two or more excited states. The role of cooperative excitation in the phenomenon of sensitization of various photochemical and photophysical processes is pointed out.
TL;DR: A study of the effects of photographic nonlinearities in recording coherent wavefronts is reported, with particular emphasis on holography using the two-beam interferometry technique.
Abstract: A study of the effects of photographic nonlinearities in recording coherent wavefronts is reported. Particular emphasis is placed on holography using the two-beam interferometry technique. A phenomenological model which provides the mathematical formulation for describing the effects of nonlinearities is described. The model includes a zero-memory nonlinearity which represents experimentally derived transmittance–exposure curves for various photographic emulsions. An analysis of this model reveals many interesting phenomena which are supported experimentally. In particular, the nonlinearity of the film generates false targets, causes weak signal suppression, and can introduce additional noise as a result of spectral folding. Experimental results, verifying the analysis, are presented.
IBM1
TL;DR: Four ways of creating a FZP pattern as a moiré effect by superposing pairs of suitable masks are described, sufficiently general to allow the synthesis of patterns other than the FzP by means of a variable moirÉ effect.
Abstract: Among the conceivable uses of Fresnel Zone Plates (FZP) are image formation, synthesis of holograms, coherence measurements, spectrometry, optical analog computation, and optical testing. Sometimes it is desirable to change the scale of the FZP continuously, for example to give a zoom lens effect when the FZP is used for image formation. Here we describe four ways of creating a FZP pattern as a moire effect by superposing pairs of suitable masks. The relative position of the two masks determines the FZP scale. The theory presented here is sufficiently general to allow the synthesis of patterns other than the FZP by means of a variable moire effect.
TL;DR: Techniques useful to the solutions of these problems are presented, such as increasing the coherence length of a laser with little sacrifice in power, improving the signal-to-noise ratio in the reconstruction, controlling the shrinkage of the emulsion to eliminate color shift, and increasing the speed of Kodak 649F emulsion.
Abstract: Because of the characteristics of the available white light sources, lasers and photographic emulsions, as well as the environmental condition of a laboratory, many practical problems are often encountered in making high quality multicolor holograms reconstructed in white light. The nature of the difficulties is discussed. Techniques useful to the solutions of these problems are presented, such as increasing the coherence length of a laser with little sacrifice in power, improving the signal-to-noise ratio in the reconstruction, controlling the shrinkage of the emulsion to eliminate color shift, and increasing the speed of Kodak 649F emulsion.
TL;DR: Volume backscattering functions and optical extinction coefficients are computed for eight suggested major cloud models using the Mie theory and results show that there is no clear advantage of one wavelength over another for improving cloud transmission; however, backscatter is significantly reduced at the longer wavelengths.
Abstract: Volume backscattering functions and optical extinction coefficients are computed for eight suggested major cloud models using the Mie theory for optical wavelengths of 0.488 micro, 0.694 micro, 1.06 micro, 4.0 micro, and 10.6 micro. Results show that there is no clear advantage of one wavelength over another for improving cloud transmission; however, backscattering is significantly reduced at the longer wavelengths. Variations in the optical properties of clouds are also discussed and calculations summarized to indicate the effects of cloud thickness, inhomogeneity, and geographical location on the backscatter function and extinction coefficient.
TL;DR: A modified laser probe for spectrochemical analysis is described, and modifications were made to the instrument to alleviate some of the problems encountered.
Abstract: A modified laser probe for spectrochemical analysis is described. A high energy laser beam is focused onto a specimen to vaporize a sample from a small area, and the vapor thus formed is further excited by a spark discharge. The characteristics of emission spectra with and without auxiliary spark excitation are compared. Spectrograph illuminating systems for qualitative and quantitative analysis were investigated. Some difficulties were encountered with the laser probe, and modifications were made to the instrument to alleviate some of these problems. Some typical analytical applications are discussed.
TL;DR: From data, the optimum bias level and the ratio of the signal beam to the reference beam for recording interference patterns are determined, and the modulation transfer function of the film can also be determined.
Abstract: Various parameters of recording spatially modulated coherent light have been studied, with particular emphasis on the parameters related to constructing holograms These include the ratio of the reference beam's intensity to that of the signal beam, the offset angle, the film's transfer characteristic, and the recording wavelength Experimental results were obtained by recording interference patterns on highresolution film using the 6328-a line of the He-Ne laser The bias level of the interference pattern was varied so as to vary the operating point on the curve representing the film's amplitude transmittance vs exposure characteristics The percent modulation and the spatial frequency were also varied at each of the operating points Interference patterns were recorded, using the 4880-aand 5145-a lines from the argon laser From these data, the optimum bias level and the ratio of the signal beam to the reference beam for recording interference patterns are determined The modulation transfer function of the film can also be determined
TL;DR: It is shown that geometrical optics based on the effects of large scale atmospheric irregularities does not adequately account for signal intensity fluctuations and may be helpful in predicting the capability of specific communications systems and in understanding better the nature of atmospheric turbulence.
Abstract: An experimental study of horizontal laser beam propagation over paths up to 145 km long was made in which beam diameter and shape, intensity fluctuations, and optical phase distortion were measured. It was found that (1) received beam diameter decreases (on-axis power density increases) with increasing transmitter aperture to a limit reached at an aperture of about 11 cm, (2) beam diameter varies as the 1.2 power of path length, (3) the amplitude of intensity fluctuations decreases with increasing receiver aperture and is nearly independent of path length for paths longer than 0.55 km, (4) the fluctuation spectrum shows a decrease in spectral power with increasing frequency, this negative slope becoming steeper with increasing receiver aperture and remaining constant with path length, and (5) rms fluctuation in phase path length was observed to be 0.25 μ over a 48.8-m path. In addition, it is shown that geometrical optics based on the effects of large scale atmospheric irregularities does not adequately account for signal intensity fluctuations. These results may be helpful in predicting the capability of specific communications systems and in understanding better the nature of atmospheric turbulence.
TL;DR: It is speculated that more advanced designs may stabilize interference fringes even with larger phase perturbations such as large doppler shifts, optical frequency differences, motion of the scene, and holographic interferometry.
Abstract: A feedback control system has been designed to stabilize the position of interference fringes, particularly those which occur in holography. The result of closed loop operation of the system is that rather severe phase perturbations may occur in either of the beams, and yet be compensated for such that the fringes in the holographic recording medium are essentially stabilized. This paper discusses the design and analysis of an experimental model and its performance for phase perturbations due to acoustic and mechanical vibration, thermal drift, large perturbations, warm air turbulence, and small doppler shifts. The authors then speculate that more advanced designs may stabilize interference fringes even with larger phase perturbations such as large doppler shifts, optical frequency differences, motion of the scene, and holographic interferometry.
TL;DR: Holographic interferometry can be applied to plasmas whose density results in shifts of less than one fringe by superposing the small shifts on an arbitrarily shaped and positioned background fringe pattern.
Abstract: Holographic interferometry can be applied to plasmas whose density results in shifts of less than one fringe by superposing the small shifts on an arbitrarily shaped and positioned background fringe pattern. The sensitivity of holographic interferometry is thereby increased to that of conventional interferometry, while the inherent advantages of holography are retained. The background fringes also simplify detection of the spurious phase changes that can arise in holography from motions of the apparatus.
TL;DR: In the measurements, small isosceles K T N prisms, 1 mm thick with the refracting edge parallel to the [001] direction, were used, and the two slit images corresponding to the ordinary and extraordinary rays are rather fuzzy; this is attributed to internal refractive index changes related to the domain structure.
Abstract: Potassium tantalate niobate (KTN) crystals of the composition KTa0.65Nb0.35O3 are known to have a large quadratic electrooptic effect (Kerr) above the Curie point . 4 This communication deals with a linear electrooptic effect (Pockels) observable below the Curie point when the crystal is tetragonal, 4 mm. In the measurements, small isosceles K T N prisms, 1 mm thick with the refracting edge parallel to the [001] direction, were used. The prisms were mounted on the table of a L114 Gaertner spec trometer equipped with a special substrate to permit application of electric fields. The large prism faces [001] were electroded with aquadag so that the field direction was parallel to [001], Fig. 1. The Curie point of the crystals used was 28°C and 88°C, which, according to an interpolation of Triebwasser's data, corresponds to compositions of KTa0.62Nb0.38O3 and KTa0.52Nb0.48O3, respec tively. Measurements were carried out using monochromatic light of wavelength 546 mμ from a mercury arc lamp. I t was not possible to check directly if the prisms used in the measurements were completely single domain. If observed below the Curie point, without any field applied, the two slit images corresponding to the ordinary and extraordinary rays are rather fuzzy; we attribute this to internal refractive index changes related to the domain structure. If the crystals are heated above the Curie point, the two slit images fuse into one, and the image is sharp. If the crystal is now slowly cooled with a field applied, the single image splits into two sharp images which, even after
TL;DR: A series representation developed from holography theory is used to determine the image distances and relative image intensities for three types of zone plates.
Abstract: A series representation developed from holography theory is used to determine the image distances and relative image intensities for three types of zone plates. The effect of nonlinearity in film reproduction on the hologram of a point object and the images produced by this hologram are discussed.
TL;DR: The theory of moiré fringes is extended to this case of grossly dissimilar grating frequencies and the combination of a symmetrical double-order blazed reference grating with a coarse bar-and-space active grating appears most attractive for many metrological applications.
Abstract: Sensitivity and accuracy of measurements made by the moire effect can be increased by a fringe multiplication factor. For a given displacement or deformation, the number of fringes that cross the field is increased by this factor. Multiplications as high as thirty are demonstrated. High sensitivity measurements are possible with coarse active gratings. With two amplitude gratings of equal nominal frequencies multiplication patterns exhibiting pure two-beam interference are produced when transmittance is 0.5. With gratings in which frequencies are dissimilar by integral factor β, multiplication by bβ is achieved, where b is an integer. Guild’s theory of moire fringes is extended to this case of grossly dissimilar grating frequencies. The combination of a symmetrical double-order blazed reference grating with a coarse bar-and-space active grating appears most attractive for many metrological applications.
TL;DR: This paper presents the results of a theoretical and experimental study of the properties of real-time electrooptical spectrum analyzers with coherent detection, and concludes that the construction of such devices is feasible.
Abstract: In conventional real-time electrooptical signal processors, the variation of the output intensity with time is directly detected with a photodetector. As a result of this, any information carried in the phase of the light is lost. However, if the light is detected coherently, i.e., it is heterodyned with another coherent local oscillator light source on the detector surface, the phase associated with the amplitude of the light may be preserved. This paper presents the results of a theoretical and experimental study of the properties of real-time electrooptical spectrum analyzers with coherent detection. Basic equations of operation are presented and discussed, and confirmed by experiment, and it is concluded that the construction of such devices is feasible.