Showing papers in "Journal of the Optical Society of America in 1967"
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TL;DR: In this paper, the directional distribution of radiant flux reflected from roughened surfaces is analyzed on the basis of geometrical optics, and the analysis successfully predicts the off-specular maxima in the reflection distribution which are observed experimentally and which emerge as the incidence angle increases.
Abstract: The directional distribution of radiant flux reflected from roughened surfaces is analyzed on the basis of geometrical optics. The analytical model assumes that the surface consists of small, randomly disposed, mirror-like facets. Specular reflection from these facets plus a diffuse component due to multiple reflections and/or internal scattering are postulated as the basic mechanisms of the reflection process. The effects of shadowing and masking of facets by adjacent facets are included in the analysis. The angular distributions of reflected flux predicted by the analysis are in very good agreement with experiment for both metallic and nonmetallic surfaces. Moreover, the analysis successfully predicts the off-specular maxima in the reflection distribution which are observed experimentally and which emerge as the incidence angle increases. The model thus affords a rational explanation for the off-specular peak phenomenon in terms of mutual masking and shadowing of mirror-like, specularly reflecting surface facets.
1,673 citations
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TL;DR: The contrast sensitivity of the human eye for sinusoidal illuminance changes was measured as a function of spatial frequency, for monochromatic light with wavelengths of 450, 525, and 650 nm as discussed by the authors.
Abstract: The contrast sensitivity of the human eye for sinusoidal illuminance changes was measured as a function of spatial frequency, for monochromatic light with wavelengths of 450, 525, and 650 nm. At each wavelength, data were obtained for a number of illuminance levels. All observations were taken at equal accommodation, and corrected for chromatic aberration. If the wavelength-dependent effects of diffraction on the modulation transfer are taken into account, no difference is found between the photopic contrast-sensitivity functions for red, green, or blue. For mean retinal illuminances B0 smaller than 300 td, threshold modulation M at a given frequency is found to increase in proportion to B0-12 (de Vries–Rose law). For B0 greater than 300 td M remains a constant fraction of it (Weber–Fechner law). After separation of the optical modulation transfer of the eye media from the measured psychophysical data, the remaining function can be considered as composed of a neural and a light-diffusion transfer function. The latter can be compared with the analytic transfer function of photographic film.
679 citations
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TL;DR: The standard displacement-step stimulus often used to produce lateral saccadic eye movements is considered in terms of the effects of its components: termination of stimulation at an initial fixation point, and onset of stimulating at a new, laterally displaced fixation point.
Abstract: The standard displacement-step stimulus often used to produce lateral saccadic eye movements is considered in terms of the effects of its components: termination of stimulation at an initial fixation point, and onset of stimulation at a new, laterally displaced fixation point. If the termination and onset are simultaneous, saccade latency is about 200 msec. If there is a gap of 200 msec or more between these events, latency decreases to about 150 msec. If the termination follows the onset by 100 msec or more, latency increases to about 250 msec.
657 citations
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TL;DR: In this paper, the restoration of optical images, as well as the unfolding of spectroscopic and other data that have been convolved with a window function or an instrumental impulse response, can be viewed as the solution of an integral equation, which is treated as the problem of finding an estimate that is a linear functional of the data and minimizes the mean squared error between the true solution and itself.
Abstract: The restoration of optical images, as well as the unfolding of spectroscopic and other data that have been convolved with a window function or an instrumental impulse response, can be viewed as the solution of an integral equation. Solution of such an integral equation when the data are corrupted by noise or experimental error is treated as the problem of finding an estimate that is a linear functional of the data and minimizes the mean squared error between the true solution and itself. The estimate depends on assumptions about the spectral densities of the images and the noise, the choice of which is discussed. Coherent optical processing and digital processing are described.
442 citations
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TL;DR: In this article, the growth curves calculated for Lorentz lines were used for molecular spectra representation using growth curves for the 1.1/s line intensity distribution function, and the growth curve was calculated for the 2.5/2.
Abstract: 1/s line intensity distribution function for molecular spectra representation using growth curves calculated for Lorentz lines
416 citations
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TL;DR: Under carefully controlled conditions, in blocks of trials in which the stimulus displacement on any given trial is randomly selected from a group of two, four, or eight possible displacements, latency for lateral saccadic eye movement does not change, and previous estimates of saccade latency using single stimulus displacements were underestimates.
Abstract: Under carefully controlled conditions, in blocks of trials in which the stimulus displacement on any given trial is randomly selected from a group of two, four, or eight possible displacements, latency for lateral saccadic eye movement does not change. Moreover, a subject trained on such a disjunctive latency task, and then presented with blocks of trials in which there is only one possible stimulus displacement, of probability 1.00, 0.75, 0.50, or 0.25, displays the same latency to that displacement as when it was embedded in one of the disjunctive sets. These results conflict with reports that knowledge of stimulus location determines saccade latency. When the saccade on each trial is under the control of the stimulus on that trial, the size of the set of possible stimulus displacements does not affect latency to a particular displacement. These results also suggest that previous estimates of saccade latency using single stimulus displacements were underestimates, because subjects were not trained to follow stimulus displacement in a disjunctive task. Care is required if saccade latencies are to be entirely attributed to control by stimulus factors.
348 citations
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TL;DR: In this article, the necessary and sufficient conditions for self-imaging were derived in order that an infinite plane object, illuminated by a plane monochromatic wave of normal incidence, images itself without the aid of lenses or other optical accessories.
Abstract: The necessary and sufficient conditions are derived in order that an infinite plane object, illuminated by a plane monochromatic wave of normal incidence, images itself without the aid of lenses or other optical accessories. This involves a solution of the reduced wave equation which does not satisfy the Sommerfeld radiation condition. The solution is obtained by requiring a geometrical-optics limiting condition as the wavelength λ goes to zero. Two cases of self-imaging are considered. The first case, called weak, deals with the faithful imaging of objects whose spatial frequencies are all much smaller than the (1/λ) value of the illuminating source. The conditions for this case demand that the two-dimensional Fourier spectrum of the object lies on the circles of a Fresnel zone plate. The second case, called strong, deals with the faithful imaging of objects for spatial frequencies up to the natural cutoff of 1/λ. Both doubly- and singly-periodic and nonperiodic objects are considered. For periodic objects the results are shown to agree well with the experimental and theoretical work to date, the latter of which has always employed the Fresnel–Kirchhoff diffraction integral with the parabolic approximation appropriate to Fresnel diffraction.
347 citations
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TL;DR: The findings indicate that stereopsis and the classically conceived corresponding points greatly depend both on the class of stimulus used and on the recent history of the stimulation.
Abstract: A novel phenomenon in stereopsis can be observed when viewing binocularly stabilized retinal images. This phenomenon is particularly impressive for random-dot stereoscopic images in foveal vision. If initially the left and right images are brought within Panum’s fusional area (6-min arc alignment), fusion and stereopsis are perceived; the images can then be pulled apart symmetrically by about 2 deg in the horizontal direction without loss of stereopsis or fusion. The images are actually pulled apart on the retinae, since the binocular retinal stabilization compensates for the convergence-divergence motions of the eyes; hence a supra-retinal function must be responsible for this type of fusion. If the pulling proceeds too fast, or exceeds the 2-deg limit, or if the stimulus is occluded briefly, the fusional mechanism fails and the fused image abruptly breaks apart into two separate images which have to be brought within Panum’s area again to re-establish fusion. For line stimuli, the maximum disparity without loss of fusion is much less than for random-dot patterns; it is always largest for disparity in the horizontal direction and is less in the vertical direction. These findings indicate that stereopsis and the classically conceived corresponding points greatly depend both on the class of stimulus used and on the recent history of the stimulation.
298 citations
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TL;DR: The threshold modulation for perception of a moving grating is generally higher than that for detection of brightness changes, in space and/or time, that give rise to flicker phenomena, which suggests a photon-noise-dependent threshold mechanism which is operative in a wider illuminance range than that found with contrast-sensitivity measurements for periodic illuminances variations only in space or only in time.
Abstract: The contrast sensitivity of the human eye for sinusoidal illuminance changes in space and time, obtained by means of traveling-wave stimuli, was measured as a function of spatial and temporal frequency for white light. The average retinal illuminance was varied between 0.85 and 850 trolands. The threshold modulation for perception of a moving grating is generally higher than that for detection of brightness changes, in space and/or time, that give rise to flicker phenomena. Flicker-fusion characteristics, as determined from the thresholds for the flicker phenomenon, are found to lose their band-pass-filter resemblance for spatial frequencies of more than 5 cycles per degree of visual angle. The thresholds at flicker fusion for spatial- and temporal-frequency combinations in which not both frequencies are very low, appear to be proportional to the inverse of the square root of mean retinal illuminance, in the investigated range. This suggests a photon-noise-dependent threshold mechanism which is operative in a wider illuminance range than that found with contrast-sensitivity measurements for periodic illuminance variations only in space or only in time.
295 citations
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TL;DR: In this paper, the imaging, magnification, and aberration properties of the images formed from holograms were extended to the non-paraxial case, which can be used to locate accurately the position of an image point in cases where the paraxial theory fails.
Abstract: This study extends the imaging, magnification, and aberration properties of the images formed from holograms to the nonparaxial case. This extension yields expressions which can be used to locate accurately the position of an image point in those cases where the paraxial theory fails. The readout-illumination critical angles for image formation are predicted and related to the critical angles of a diffraction grating. The ratio of readout wavelength to recording wavelength is limited, and consequently wavelength-change magnification is limited, for certain types of holograms. The expressions developed are kept in the same form as those developed for the paraxial case so that the reduction to the paraxial case is obvious, and the many prior comments made on aberration reduction are applicable by a simple change of variable.
294 citations
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TL;DR: In this article, the relationship between the statistics of log-amplitude fluctuations and irradiance fluctuations due to atmospheric turbulence is derived and the effect of use of a large aperture diameter in reducing the variance of a fluctuating signal is evaluated.
Abstract: The relationship between the statistics of log-amplitude fluctuations and irradiance fluctuations due to atmospheric turbulence is derived This is used to evaluate the effect of use of a large aperture diameter in reducing the variance of a fluctuating signal Curves for the reduction factor are presented From these, an irradiance-fluctuation correlation distance is evaluated This distance, unlike the correlation distance for log-amplitude fluctuations, is found to be a function of the log-amplitude variance A particular example of the application of these results to a space-to-ground communications systems performance is worked out
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TL;DR: In this article, two methods for obtaining three-dimensional holographic images containing superimposed constant-range contours for accurate cross-section tracing or contour mapping are described, and the positions of the reference sources may be optimized so that contours will appear over a maximum object angle.
Abstract: This paper describes two methods for obtaining three-dimensional holographic images containing superimposed constant-range contours for accurate cross-section tracing or contour mapping. The first and simplest method requires two illuminating sources with identical wavelength but at slightly different positions. This method has the drawback of requiring the hologram to be made at right-angles to the illumination direction. This results in shadowed areas on the object. The second method requires an illuminating source containing two wavelengths. This method also requires precise positioning of two reference sources, one for each wavelength. The positions of the reference sources may be optimized so that contours will appear over a maximum object angle. Experimental results that prove the principle are shown.
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TL;DR: A family of brightness functions has been computed from the data for complex stimuli such as photographic reproductions viewed with both illuminated and dark surrounds, which exhibit exponential decay from the power form as a function of both screen luminance and surround luminance.
Abstract: Results of brightness-scaling experiments with complex stimulus fields are reported. A family of brightness functions has been computed from the data for complex stimuli such as photographic reproductions viewed with both illuminated and dark surrounds. The resulting brightness vs luminance functions are not simple power functions. They exhibit exponential decay from the power form as a function of both screen luminance and surround luminance; i.e., they are nonlinear in log–log coordinates.
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TL;DR: In this paper, a transfer theory is developed that determines the image space and three-dimensional image spectrum of a 3D object, based on the existence of volumes of stationarity, termed "isotomes;" into which the object must be partitioned.
Abstract: A transfer theory is developed that determines the image space, and three-dimensional image spectrum, of a 3–D object. For both incoherent and coherent illumination, the image is found to obey convolution, transfer, and sampling theorems that resemble the familiar results of ordinary 2-D theory. A 3-D transfer function is related to the pupil function of the image-forming optical system. One result of the theory is that with incoherent illumination, the object image space contains no more than 1/(λ3f/no.4) degrees of freedom/unit volume, where λ is the wavelength of light. The transfer theory is based on the existence of volumes of stationarity, termed “isotomes;” into which the object must be partitioned. Isotomicity is shown to be approximated, over sufficiently small volumes, in the diffraction-limited case.
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TL;DR: Contrast sensitivity for square-wave gratings of spatial frequencies between 0.44 and 33.2 cycles/deg was determined for exposure durations between 11 and 500 msec as mentioned in this paper.
Abstract: Contrast sensitivity for square-wave gratings of spatial frequencies between 0.44 and 33.2 cycles/deg was determined for exposure durations between 11 and 500 msec. The space-average luminance of the targets was kept constant at 10 mL, regardless of contrast, and equal to that of the pre- and post-exposure fields, which contained a cross-hair reticle to help maintain accommodation and fixation. At the longest exposure duration (500 msec) the contrast sensitivity function exhibited both the high- and the low-frequency declines described by previous investigators. At the briefest exposure duration tested (11 msec), the low-frequency decline of contrast sensitivity was virtually absent. Log contrast sensitivity improves with increasing exposure duration, but more for high-frequency than for low-frequency gratings. These results are compatible with the assumption that there is a time delay in the occurrence of inhibitory interactions in the retina.
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TL;DR: The modulation sensitivity for vertical and horizontal orientations of the fringes was greater than for oblique orientations for a wide range of spatial frequencies and a similar orientation preference was found for the cut-off spatial frequencies.
Abstract: It is now well established that, for many test targets, vertical and horizontal orientations yield higher visual acuities than oblique orientations. In order to assess the role of the optics of the eye in this effect, focusing errors of the eye were bypassed by using as the measure of resolving capacity the modulation sensitivity for sinusoidal interference fringes formed on the retina. The modulation sensitivity for vertical and horizontal orientations of the fringes was greater than for oblique orientations for a wide range of spatial frequencies. A similar orientation preference was found for the cut-off spatial frequencies. Measurements of the modulation sensitivity at 15° orientation intervals indicated that maxima in sensitivity were spaced at 90° intervals. Since the effects of the optics of the eye have been eliminated, the origin of meridional variations in acuity must lie in the retina and/or higher visual pathways.
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TL;DR: In this article, photoionization-efficiency curves are obtained for the molecule and fragment ions of the subject molecules in the wavelength region extending from onset of ionization to 600 A. Autoionization in the continuum is correlated with various progressions of Rydberg series.
Abstract: Photoionization-efficiency curves are obtained for the molecule and fragment ions of the subject molecules in the wavelength region extending from onset of ionization to 600 A. The initial onset of O2+ is observed at 12.072 eV. Autoionization in the continuum is correlated with various progressions of Rydberg series. Curves for both O+ and O− ions formed by the ion–pair process from O2 are obtained and 1.48 eV is derived for the electron affinity of oxygen atoms. The shape of the CO2+ curve including structure ascribed to autoionization is discussed. The unresolved 2Пg-doublet threshold is observed at 13.77 eV with the first vibrational level at 13.93 eV. The onset of the O+-fragment ion indicates about 0.04 eV excess energy in the dissociation process. It is suggested that dissociative ionization occurs from the autoionizing Rydberg level just above the calculated threshold value. Partially resolved doublet components of COS+ are observed at 11.18 and 11.22 eV, respectively. Intense autoionization is observed. Various thermochemical values are calculated from the fragment-ion thresholds. The doublet components of the ion ground state of CS2+ are observed at 10.059 and 10.112 eV, respectively. Intense autoionization is observed at wavelengths which are in excellent agreement with known Rydberg levels for the molecule. Although the S+ ion is formed with excess energy, the CS+ ion gives a value of 11.71 eV for the ionization energy of the CS radical. This is in agreement with but more precise than a directly measured electron-impact value.
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TL;DR: In this paper, the disagreement between physical and psychophysical estimates of human optical performance is discussed, and several simple fundal-image profiles are derived from the measured modulation transfer functions, and the importance of these profiles to psychophysical measurements is discussed.
Abstract: The disagreement between physical and psychophysical estimates of human optical performance is discussed. Recent measurements of the eye’s modulation transfer functions in white light for several pupil sizes are used to compare the eye with an ideal optical system in terms of normalized modulation transfer functions, point image profiles, and Strehl ratios. Several simple fundal-image profiles are derived from the measured modulation transfer functions, and the importance of these profiles to psychophysical measurements is discussed. Glare is considered as the extension of point spread functions to large angles; experimental measurements are compared with theories for the special case of an annular target.
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TL;DR: It is suggested that the blue-blindness of the fixation area is a final step in the general withdrawal of image vision from the short wavelengths of the spectrum, for which the chromatic aberration of the eye is greatest.
Abstract: An area at the center of the human fovea, subtending a visual angle of only 7–8 min and hence hardly larger than the fixation area, is blue-blind in the sense of almost or entirely lacking blue-sensitive cones. This is a matter of foveal topography, not size of field, for in fields of this size elsewhere in the fovea or in the parafovea, blue-sensitive cones are well represented. The blue-cone system falls in sensitivity from the border of the photopic zone—the functionally all-cone area—to a minimum, usually to extinction, at its center. Other features of foveal topography oppose this trend: the density of cones rises and the macular pigmentation thins out toward the center of the fovea. Also the red- and green-cone systems display the opposite gradient; their sensitivities decline regularly from the center toward the borders of the fovea and beyond.Tritanopia, though the rarest form of congenital color-blindness, is thus a regular feature of the center of the normal fovea. The existence of two neutral points in this condition, in the yellow and violet, has its basis in the observation that the luminosity curves of the red- and green-sensitive cones, drawn so as to cross in the yellow, cross again or fuse in the violet region. It is suggested that the blue-blindness of the fixation area is a final step in the general withdrawal of image vision from the short wavelengths of the spectrum, for which the chromatic aberration of the eye is greatest. The blue-blindness of the fixation area, taken together with the red-green blindness of more-or-less concentric zones of the near periphery, and the total colorblindness of the far periphery, raises the possibility that various zones of the normal retina display all the major forms of colorblindness. Trichromic vision is normal only in the broad, central annulus of the retina, which alone is ordinarily tested. Some instances of defective color vision may be similarly localized. The problems of both normal and defective color vision involve not only the presence or absence of certain visual pigments and types of cone, but their spatial distributions on the retinal surface, and their neural connections.
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TL;DR: It is now well established in principle that superresolving optical systems can be made, but can detail smaller than one half the wavelength of light really be made visible?
Abstract: It is now well established in principle that superresolving optical systems can be made. Such systems, when viewing objects of finite extent, can resolve detail finer than the normal diffraction limit. This has obvious attractions for microscopy, but we may wonder whether the ultimate diffraction limit for a lens of large numerical aperture, the limit which counts in microscopy, can be beaten. Can detail smaller than one half the wavelength of light really be made visible? It can be, but only in specialized and probably limited applications.
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TL;DR: In this article, measurements of the scintillation of a laser beam after propagating over an 8 km path near the ground were made with collection apertures ranging from 1 mm to 1 m in diameter.
Abstract: Measurements have been made of the scintillation of a laser beam after propagating over an 8-km path near the ground. The measurements were made with collection apertures ranging from 1 mm to 1 m in diameter. The probability distribution of the scintillation was found to be log-normal for all collector diameters. The log-normal variance decreased smoothly for diameters from 1 mm to about 10 cm, but showed no decrease between 10 cm and 1 m. A hypothesis is offered which explains those results which are anomalous in terms of present theories. Measurements of the log-normal variance were made over extensive periods on three days, during winter, spring, and summer. From these the atmosphere’s refractive-index structure constant, CN2, was computed. Values of CN2 were found to be fairly constant over the full range of measurements, falling between 3 and 6×10−15m−23, except near sunrise and sunset, when values of about 1×10−15m−23 were more typical.
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TL;DR: In this article, the optical constants of crystal quartz in the far infrared (10−400 cm−1) were presented along with the dispersion parameters for the two ordinary-ray bands measured in this study.
Abstract: The optical constants of crystal quartz in the far infrared (10–400 cm−1) are presented along with the dispersion parameters for the two ordinary-ray bands measured in this study. The asymmetric Fourier-transform method was used for the quantitative measurement of the refractive indices of quartz. The advantages of this method as compared with the channeled-spectrum method usually employed for refractive-index measurements in the far infrared are discussed. The extrapolated, zero-frequency refractive indices of quartz are n0(0)=2.106±0.001 and ne(0)=2.154±0.001. A pseudocoherence effect is described which permits the measurement of the difference of the principle refractive indices in a birefringent sample without the use of a polarizer.
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TL;DR: In this paper, the amplitude and phase coefficients of the two-dimensional Fourier series representing the degraded images were corrected by applying corrections to the optical transfer function of the turbulence measured at the time the images were photographed.
Abstract: Turbulence-degraded images have been processed to obtain an improvement of their visual image quality. The initial objects were photographed through laboratory-generated turbulence. The resulting transparencies of the degraded images were digitized by a photoelectric scanner and processed on a digital computer. The processing consisted of applying corrections to the amplitude and phase coefficients of the two-dimensional Fourier series representing the degraded images. The correction factors were obtained from the optical transfer function of the turbulence measured at the time the images were photographed. The experiment was done for 5-msec and 1-min exposure times. The processed data were used to generate photographs. The processed images were found to have significantly more visual detail than the original degraded images; the 5-msec-exposure restorations were superior to the 1-min-exposure restorations.
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TL;DR: In this article, the illuminance f of a distorted image is assumed to be the sum of a spatially stationary noise process and the result of a convolution of the illumnance g of the undistorted image with an optical point spread function k.
Abstract: In the model studied here, the illuminance f of a distorted image is assumed to be the sum of a spatially stationary noise process and the result of a convolution of the illuminance g of the undistorted image with an optical point spread function k. The illuminance ĝ of a restored image is obtained by a linear filtering operation on f. We determine the filter that minimizes the mean squared error between ĝ and g. The case in which k is stochastic (e.g., observations made through a turbulent atmosphere) is our main concern.
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TL;DR: In this article, a comparison of the relative efficiency when the scattering gas is located inside and outside the laser cavity is given for the pure rotational Raman scattering of O2, CO2 and H3CC≡CH (methylacetylene).
Abstract: Several techniques of exciting Raman spectra of low-pressure gases and vapors with cw laser radiation are described. Both the He–Ne laser with output at 6328 a and the Ar+ ion laser with output at 4880 and 5145 a have been used. The use of the He–Ne laser with a multiple-pass Raman tube inside the laser cavity yields Raman spectra which can be photographed in exposure times that are equivalent to those required with the classical Hg-arc and large-volume Raman tube as the source of scattered radiation. The Ar+-ion laser allows the photoelectric recording of rotational Raman spectra at atmospheric pressure with a signal/noise ratio of 10:1 when the Raman tube is located outside the laser cavity, and about 100:1 when the Raman tube is inside the laser cavity. A comparison is given for the relative efficiency when the scattering gas is located inside and outside the laser cavity. Pure rotational Raman spectra for N2, O2, CO2, and H3CC≡CH (methylacetylene) are presented. The depolarization ratios of both the Rayleigh and Raman lines of N2, O2, and CO2 have been determined and relative scattering cross section for the pure rotational Raman scattering of oxygen has been obtained.
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TL;DR: In this article, a detailed analysis of the behavior of the Poynting vector in the focal region of a coherent beam is presented, where diagrams showing the flow lines and the contours of constant amplitude of the time-averaged PoyNTing vector are given.
Abstract: In a previous paper [ Phys. Rev.138, B1561 ( 1965)] some new results were presented relating to the structure of the electromagnetic field near the focus of a coherent beam emerging from an aplanatic optical system. The present paper supplements the previous one by providing detailed analysis of the behavior of the Poynting vector in the focal region of such a beam. In particular, diagrams showing the flow lines and the contours of constant amplitude of the time-averaged Poynting vector are given. The energy flow is found to have vortices near certain points of the focal plane. Two diagrams showing the behavior of the flow near a typical vortex are also included.
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TL;DR: In this paper, the variance of the log-amplitude of a laser beam is evaluated for a horizontal propagation path through the atmosphere, based on results obtained by Schmeltzer.
Abstract: The variance of the log-amplitude of a laser beam is evaluated for a horizontal propagation path through the atmosphere. The treatment is based upon results obtained by Schmeltzer. It is found that the log-amplitude variance can be separated into two factors, one of which is simply the log-amplitude variance of a spherical wave, as derived by Tatarski. The second factor, which contains the dependence upon the size α0 of the transmitted beam, can be written as a function of kα02/z, where k is the wave number and z is the path length. This second factor shows a significant oscillation around kα02/z = 1 when the transmitted beam is collimated, and starts to roll off strongly for kα02/z>1 when the transmitted beam is focused at a range z.
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TL;DR: The quantum limit to signal-to-noise ratio is approachable only with a judicious choice of reference exposure and a recording medium free of other classical noise sources.
Abstract: A fundamental limitation to the quality of wavefront reconstruction images is noise generated by the granular structure of the recording medium. Predictions of the signal-to-noise ratios that can be achieved in wavefront-reconstruction imaging are based on the checkerboard and overlapping circular-grain models of the recording medium. When the object consists of a multitude of resolvable point sources, the signal-to-noise ratio is found to be proportional to the space-bandwidth product of the recording medium; when the object is a diffuse surface, the signal-to-noise ratio is found to be independent of that space-bandwidth product. The quantum limit to signal-to-noise ratio is approachable only with a judicious choice of reference exposure and a recording medium free of other classical noise sources.
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TL;DR: It is inferred that spatial interactions are different in the chromaticness and brightness channels of the visual system and a decrease of the luminance level causes an increase of the neural integrative interaction of the color signals.
Abstract: Color-discrimination data are compared with the predictions of a generalized fluctuation theory for visual threshold behavior. Our observations for the tritanopic component of vision at low luminances are in good agreement with the expectations from this theory. We measured just-noticeable differences of hue with equiluminous square-wave test objects, which were modulated only in chromaticity. A chromaticity-contrast sensitivity function was introduced for the description of these results, in analogy of the luminance-contrast sensitivity function. Observations were made for different spatial frequencies at four reference wavelengths and at several luminance levels. The results do not show an attenuation of the low frequencies such as appears in the luminance-threshold contrast modulation. We infer from this that spatial interactions are different in the chromaticness and brightness channels of the visual system. Furthermore a decrease of the luminance level causes an increase of the neural integrative interaction of the color signals. We divided the measured chromaticity-contrast sensitivity function into an optical and a nervous component. A calculation for the optical part is given.