bluuebunny/crossref_metadata_2025 huggingface dataset:
Frequency discrimination, channels, and size constancy
Authors: Burbeck Christina A.
Published: February 2023

Spatial frequency discrimination has been gaining popularity as a tool for uncovering properties of early spatial visual processing. The assumption underlying the use of this paradigm is that frequency discrimination is based simply and exclusively on the outputs of frequency- (or size-) tuned channels, and therefore that it can reveal basic properties of those channels. The research reported here suggests that this assumption is not valid. When the gratings to be compared are presented at different distances from the observer (so that their retinal spatial frequencies, measured in cycles/degree, and objective spatial frequencies, measured in cycles/cm of the display, can be manipulated independently), discrimination is made on the basis of the objective, not the retinal, spatial frequencies. Furthermore, even with feedback and considerable practice, observers cannot learn to use the relationship between the retinal spatial frequencies as a cue. I argue that if the observer cannot learn to use the retinal frequency relationship when it conflicts with size constancy, then he is also not using it in the standard single-screen paradigm when it is consistent with size constancy. Thus, frequency discrimination cannot be accounted for simply in terms of the outputs of spatial frequency channels.
Phase pulling effects in Raman amplifiers
Authors: Ackerhalt J. R. , Kurnit N. A.
Published: February 2023

We have numerically studied transient forward and crossed-beam Raman scattering by varying both the Raman linewidth and gain. We have found the phase of the output Stokes beam in both space and time is primarily dependent on the Raman linewidth and nearly independent of the gain, i.e., the Stokes output phase does not depend on the conversion efficiency. The narrower the Raman linewidth or the longer the relaxation time, the more the output Stokes phase is pulled by the input pump phase. Conversely, the broader the Raman linewidth or the shorter the relaxation time, the more the output Stokes phase is controlled by the input Stokes phase. If the input pump and Stokes phases are correlated, their phases remain unchanged.
Beam cleanup in efficient high-gain Raman amplifiers
Authors: Komine Hiroshi , Long William H. , Stappaerts Eddy A. , Brosnan Stephen J.
Published: February 2023

We have carried out experimental and theoretical investigations of beam quality improvement in forward Raman amplifiers. In appropriate conditions, efficient conversion of laser beams of poor spatial quality into Stokes beams with nearly diffraction-limited wave fronts can be realized. The results were obtained using a configuration with parallel copropagating pump and Stokes beams. A discharge-pumped XeCl laser with an output of 0.5 J in a 60-ns pulse was used to carry out the experiments. In the present experiments, a near diffraction-limited low-energy Stokes beam was generated in a superfluorescent oscillator. The first Stokes order output of this oscillator was injected with the pump beam in a Raman amplifier with a Fresnel number as high as 150. The wave front of the pump was distorted using aberrators of variable strength and spatial frequency content. In conditions of amplifier Fresnel number and pump beam distortion where phase distortions on the pump did not lead to significant intensity distortions in the amplifier, the Stokes beam quality was not affected by the saturated amplification process. Pulse shapes and phase front interferograms were obtained for the pump and Stokes. The results are in good agreement with 3-D wave-optics code simulations.
Limitations on Stokes beam coherence for broadband pumping
Authors: Drühl KAI J.
Published: February 2023

We address the problem of pumping Stokes radiation by broadband incoherent laser beams in contrast to aberrated beams. While for aberrated beams the transversal phase variations in any given plane of reference are constant in time, they will fluctuate in time for incoherent beams. As is well known for Raman scattering by broadband lasers, the frequency mode structure of the amplified Stokes beam will be modified by the pump laser, leading to an increase in temporal correlation between pump and Stokes. For collinear pumping by an incoherent pump this implies that the amplified Stokes beam will also be incoherent, even if seeded initially with a coherent beam. For transversal pumping geometries Stokes beam coherence will be affected by the reduced temporal correlation between the pump fields at different transversal locations. In the case of resonant scattering (linewidth much smaller than mode spacing), we show that the transversal Stokes coherence length is limited by the longitudinal coherence length of the pump. In addition, a reduction in gain occurs. We present analytical and numerical results which indicate corresponding limitations for intermediate scattering (linewidth comparable to mode spacing), which is the case of practical interest in gases.
Perceptual organization and the representation of natural form
Authors: Pentland Alex P.
Published: February 2023

Most vision research is based on pointwise image formation physics. People, however, require more than such local information and are strikingly insensitive to reflectance function, etc. People depend on large-scale structure to guide their perceptual interpretation; general-purpose vision seems, therefore, to require a representation capable of describing such structure. We present a representation that has proved competent to accurately describe natural and man-made forms in a succinct and psychologically natural manner. Superquadrics, a superset of traditional modeling primitives, are the basic element in this representation. These primitives are then deformed by stretching, bending, or tapering and combined using Boolean operations to recursively form new, complex primitives that may again be deformed and combined. This representation has great power and efficiency: the human body (including face and hands) requires combination of only 40 primitives, fewer than 300 bytes of information. Fractallike forms (e.g., clouds, mountains) may be described in a perceptually natural manner as the recursive sum of primitives of decreasing size. Such descriptions must be recoverable from image data, which is primarily a function of the surface's normal vector. Because the vector function describing a superquadric’s surface shape is dual to that of its surface normal we can, given only the tilt component of a few surface normals, recover the desired shape description.
Phase object microscopy using moire deflectometry
Authors: Krasinski J. , Heller D. F. , Kafri O.
Published: February 2023

We have developed a new and useful technique for the quantitative optical analysis of microscopic phase objects and specular surfaces. This technique, based on recent developments in moire deflectometry, provides quantitative ray deflection maps of microscopic objects as well as contrast enhancement. The apparatus and its use are extremely simple and are readily adapted to most optical microscopes by the insertion of a recollimating lens and a matched grating pair external to the eyepiece. The dynamic range (i.e., the sensitivity to ray deflection) of the instrument is (continuously) varied merely by adjusting the spacing between the gratings. The ray deflection map of a microscopic sample can be interpreted straightforwardly to provide a slope map of specular objects or a refractive-index gradient map (or optical thickness gradient map) of phase objects. We compare this technique to interferometric, schlieren, and phase contrast methods now in common use and present some illustrative applications.
Evaluation of color differences
Authors: MacAdam David L.
Published: February 2023

In 1886, Arthur König suggested that some perspective view of the chromaticity diagram might represent equally noticably different pairs of colors by equally spaced points. Judd published the first diagram on which that was attempted. A diagram based on Judd’s was recommended in 1960 by the International Commission on Illumination (CIE). The ratio of maximum-to-minimum radii of ellipses of equal noticeability was reduced on it from ~30:1 to ~7:1. In its 1976 recommendation, the CIE increased the vertical dimension by 50%. The ratio of maximum-to-minimum radii is still ~7:1. To do much better, it would be necessary to use a diagram that is not flat. Such a diagram is unusable. We can only hope to find a formula that will express every color difference in terms of differences of locations of points in the chromaticity diagram. Chickering published a formula (FMC1) that closely approximates the ellipses. The greatest ratio of corresponding radii is ~1.4:1. A formula to replace all previous formulas should be similarly derived from color-difference ellipsoids that represent observations by at least three observers who have normal color vision. Those ellipsoids should be obtained around at least twenty-five well-distributed chromaticities. At least ten should be obtained at three or more luminancefactor levels.
Predictive formulas for color differences
Authors: Robertson A. R.
Published: February 2023

Both vision scientists and industrial colorimetrists have proposed mathematical formulas that will predict the perceptibility of the difference between two color stimuli when each stimulus is defined by its CIE color coordinates. In 1976, in an attempt to unify practice, the international Commission on Illumination (CIE) recommended the use of two such color-difference formulas, known as CIELAB and CIELUV. Since then several new formulas have been proposed, some based on color-vision theories and some on industrial color-matching data. With enough free parameters, any set of data can be described fairly accurately, but it is becoming increasingly clear that the various published sets of data on color discrimination are incompatible with each other for reasons that are not yet understood.
Systematic variations in color matching among normal humans
Authors: Neitz Jay , Jacobs Gerald H.
Published: February 2023

There is evidence suggesting that the spectral positioning of cone photopigments varies among individuals with normal color vision. To examine this we obtained Rayleigh matches from 200 young (mean age = 20.6 yrs) color-normal individuals using large field substitution, a method which enhances color discrimination. The results reveal a discrete variation in color matches between individuals and a striking difference between males and females. The color matches made by males fall into two distributions nearly equal in size. The color matches of the females are trimodally distributed: two modes correspond to the male matches, but a majority of females match in a position intermediate to the male modes. The modal nature of the distributions indicates a stepwise variation in the spectral positioning of the cone mechanisms while the male bimodality indicates that among normals only one cone mechanism varies. The distribution of matches made by females can be accounted for by assuming that this polymorphism is X-chromosome linked. Analysis of the color matches reveals that (a) it is the long-wavelength cone mechanism that varies among normal humans and (b) the difference in λmax between the two types of long-wavelength mechanisms is ~3 nm. These results may provide insights into the mechanisms that produce inherited color vision defects.
Self-organized feature maps
Authors: Kohonen Teuvo
Published: February 2023

The biological brain is able to form various feature maps and abstractions of sensory signals. For a characteristic sensory stimulus, a response is obtained from such a map at a location which corresponds to some quantitative feature value of the stimulus. This paper offers an explanation for this ability, using an idealized model of a self-organizing collective system. The model consists of a 2-D array of identical processing elements which receive a set of sensory signals in parallel and change their sensitivity or tuning to these signals, controlled by the input signals and also by the reactions from the neighboring elements. As a result, the various elements in the array become automatically adjusted in a continuous 2-D order. The coordinates on the array then correspond to some feature dimensions that are present in the input signals. For example, such a map may represent optical features, colors, spatial frequencies, acoustical frequencies, phonemes, taxonomic classifications, depending on the signal detectors used and stimuli presented at the input. This paper describes in what conditions a collective system starts to organize itself in this way and also gives several examples of maps already produced in computer simulations.
Shape representation using scale-space
Authors: Saund Eric
Published: February 2023

A major goal of shape analysis is to derive discrete qualitative descriptions of binary data which may assume a continuum of distributions in space—witness the range of 2-D silhouettes that may be called hammer. We address the question, when during information processing should a representation proceed from a continuous, iconic data structure (i.e., in the format of the image array) to more abstract, discrete symbolic descriptors? Conventional approaches to shape representation immediately describe shape in terms of the spatial relationships among instantiations of a small number of shape primitives. Depending on the primitives chosen and the rules for assigning primitives to portions of the image, this strategy can lead to unnatural and unstable descriptions. We argue that at an early level of shape analysis the quantity of interest is the continuous-valued location and density of matter in space, across all scales of resolution. A natural data structure is scale-space, the original signal smoothed at all scales.1 Shape information is manipulated via operations for moving matter around in the scale-space image. Different shapes can be compared through comparison and alignment of their scale-space images under these operations.
Characteristics of the Lau interferometer
Authors: Cartwright Steven , Lightman Allan , Murphy John P.
Published: February 2023

The Lau interferometer uses an incoherently illuminated grating to produce a periodic coherence function which illuminates a phase object. A second grating following the phase object causes multiple sheared images that are coherent with respect to each other. If the first grating is imaged onto the second grating the shearing is wavelength independent, so a broadband incoherent source (for example, a tungsten lamp) may be used as a source. Bias fringes may be introduced by defocusing the gratings with respect to each other. The introduction of bias fringes also makes the interferometer sensitive to the position of the phase disturbance between the two gratings. Interference patterns are formed for only a thin section within a thick phase disturbance.
Real-time measurement of large surface deformation using a holographic shearing interferometer
Authors: Matsuda Kiyofumi , Aiju Tomoaki , Watanabe Shinya
Published: February 2023

Determination of the shape of a liquid surface is an accurate method of measuring the coefficient of surface tension. Françon was the first to show that a shearing interferometer provides a convenient method for the measurement of such liquid surface deformations. Hinsh measured these deformations by holographic real-time interferometry. However water surface deformation has a sharp curvature, so that small f/No. lenses must be used to avoid shadows. Then interferograms of the lens aberration distort the correct evaluation of the deformation. Moreover with large deformations of the liquid surface, too many fringes occur. We therefore need a method that cancels the aberration of the lenses and reduces the number of fringes. A new method to satisfy these conditions is proposed for the real-time measurement of large liquid surface deformation. In this method, a holographic lateral shear interferometer with two three-beam holograms is used. In the experiment, for example, the shearing interferogram was produced when a water strider floated. From the experimental results, it is shown that we can cancel the aberration of the optical system and can change the amount of shear by movement of the hologram.
Thermal waves visualized by holographic interferometry
Authors: Kaufmann Guillermo H. , Vest Charles M.
Published: February 2023

The propagation of long thermal waves through metal objects was investigated. These waves are created when the surface of an absorbing medium is subjected to a slowly modulated heat source. In this manner surface deformations large enough to be observed by holographic interferometry were induced in thin, flat aluminum plates. The oscillatory, wavelike deformations of interest are superimposed on a monotonically increasing deformation. Stroboscopic and otherwise modified forms of holographic interferometry are used to display only the wavelike portion. Predicted variations of fringe properties such as visibility and density are verified experimentally. The interaction of the long thermal waves with slots and holes in the plates is observed. The possible application of long thermal waves to holographic interferometry is noted.
Multiple components in photopic dark adaptation
Authors: Eisner Alvin
Published: February 2023

The rate of decrease of the logarithm of visual threshold at the fovea to a long-wavelength test after extinction of a 580-nm bleach is not described by an exponentially shaped function. Instead, there is a period of time during dark adaptation about midway between extinction of the bleach and complete recovery of sensitivity when threshold does not continue to decrease. The duration of this period can be up to ~1 a min depending on the illuminance of the bleach. The departure from an exponential time course of recovery is greater when the test stimulus is a disk which is defocused on the retina and sinusoidally modulated at 1 Hz than when the test stimulus is a disk which is focused on the retina and either flashed for 160 msec or sinusoidally modulated at 1 Hz. Losses of sensitivity with time are sometimes apparent about midway through recovery when the test is a defocused disk which is modulated sinusoidally at 1 Hz. When the test stimulus is a disk which is focused on the retina and flashed for 160 msec, sensitivity to test stimuli >580 nm may be described as changing successively from subtractive to additive to subtractive types of combination of L and M cone sensitivities.
Measurement of first-passage-time distributions for a Q-switched laser
Authors: Young Marvin R. , Singh Surendra
Published: February 2023

The distributions of first-passage times for the build up of laser radiation from zero intensity to some predetermined value are measured for a Q-switched laser. Experiments were performed on a single-mode He–Ne laser operating near threshold. Q-switching was performed by applying a voltage pulse to an intracavity acoustooptic modulator. Results are compared to theoretical calculations.
Theory of two-photon Doppler-free saturation spectroscopy
Authors: Marathay A. S. , Capron B. A. , Sargent M.
Published: February 2023

Reference 1 derives the two-photon probe-absorption coefficient for a homogeneously broadened medium subjected to an arbitrarily intense saturator wave. We have generalized this theory to allow for Doppler broadening with a counterrunning probe and saturator waves. We have carried out integrals over a Lorentzian Doppler distribution analytically and have specialized to a number of limits, such as extreme Doppler broadening. In this limit, we find the simple probe absorption coefficient

α
1

≃
2

α
0

(

γ

D
1

I
2

−
i

ω
s

T
1

)

, where α0 is the unsaturated two-photon absorption coefficient, I2 is the saturator intensity, γ is the two-photon coherence decay rate constant, ω
s
is the Stark shift parameter, T1 is the population difference decay time, and

D
1

=
1
/

[

γ+
i

(

ω+ω

s

I
2

−

ν
2

−

ν
1

)

]

. For vanishing Stark shifts (ω
s
= 0), this is the standard two-photon probe absorption coefficient, but for large ω
s
, the complex Lorentzian

D
1

becomes detuned. In the homogeneously broadened limit, the absorption spectrum resembles the one-photon case. In this paper we show the transition between these two limits.
Some operating principles and primary functions of cones
Authors: McLeod Roger D.
Published: February 2023

Radially outward-flowing, positively charged ionic current flowing through their bilayer double membrane side can enable cones or the rods they bias to distinguish electric vectors in opposed directions. This acts like a semicylindrical, out-ward-directed diode. Ionic current modulation is proportional to the membrane-rectified electric field. A positive reference direction and its radially reversed sense serve to complete an opposition pair for positive-negative purposes that is the opposition pair which is the physical basis of all the psychophysical data from color opponency. Two separate sets of receptors register the focal diffraction fields of a color-opponency pattern. Cones and rods separately register the two spatial diffraction patterns required for full color naming. This is the physical basis and the theoretical prediction for the experimental results of Edwin Land in the late 1950s. Three variables account for the accumulated psychophysical data of trichromacy; one for each diffraction pattern and the third variable is physiologically conditioned by lens accommodation. The brain operates by acting on its interpretation of the information that is in a spatial Fourier transformation mode retinally encoded by synoptic discharge proportional to an object's spatial frequency.1
Single-crystal fiber devices
Authors: Stone J. , Burrus C. A.
Published: February 2023

Single-crystal fibers of Nd:YAG, Nd:Y2O3, ruby, sapphire, LiNbO3, and LiTaO3 were pulled (in diameters from 15 to 100 µm) from a tiny melt obtained by heating the tip of a thin rod of the parent crystal in air with the focused beam of a CO2 laser. Short Nd:YAG fibers, some with a fused-glass cladding, were made into lasers by attaching suitable dielectric mirrors to the ends and end pumping with a single 0.8-µm wavelength AIGaAs LED. Laser output was obtained at 1.06-µm and 1.318-1.338-µm wavelength. Up to 1 mW of single-mode output power, limited primarily by imperfect coupling between the LED pump and the fiber laser, was measured. Similar laser structures made with Nd:Y2O3 and ruby were pumped with a krypton gas laser. The thermal efficiency of the fiber geometry both promoted homogeneous crystal growth and permitted cw laser operation, and all devices could be operated cw at room temperature. LiNbO3 and LiTaO3 fibers were grown for possible use as modulators. The crystalline orientation of any of the fibers could be predetermined by selecting the seed orientation, and some resultant growth habits are shown. In general, since the growth process inherently involves zone refining, single-crystal fibers are of very high purity and optical quality.
Survey of phase-matchable fibers for nonlinear optics
Authors: DeShazer LARRY G.
Published: February 2023

A variety of methods have emerged to fabricate single-crystal nonlinear optical fibers. As a class of crystals, nonlinear materials encompass the entire range of thermal behavior possible in compounds. Therefore, it has become increasingly clear that no one method of single-crystal fiber growth can accommodate the disparities of all the nonlinear crystals. Traveling-zone, Bridgman, and Czochralski methods of crystal growth have all been successfully adopted in producing single-crystal fibers. The traveling-zone method converted polycrystalline fibers to single-crystal fibers by using a submillimeter melt zone produced by a small electrical heater. Crystal fibers of CuCI were grown by this method. A Bridgman method produced single-crystal fibers in which the melt is vapor-pressure stabilized. This method was applicable to nearly congruent melting materials such as KDP-isomorph crystals. A capillary-fed Czochralski method was developed to grow fibers of congruently melting materials such as NaNO3. Capillary designs overcame the thermal steady-state limitations of the conventional Czochralski technique applied to fiber growth. All these methods of growing nonlinear optical fibers showed dimensional irregularities of the crystal fibers, to varying degrees. Because the efficiency of phase-matched processes in nonlinear fibers is sharply reduced by surface imperfections, an alternative hybrid approach was developed. This approach combined the desirable uniformity of glass fibers with bulk nonlinear crystals. The evanescent portion of guided waves in the glass core can be coupled to the nonlinear polarization of the crystal clad.
Continuous-wave and Q-switched Nd:YAG fiber lasers
Authors: Gaeta C. , Digonnet M. , Shaw H. J.
Published: February 2023

Single-crystal fibers offer a great potential as low threshold miniature laser sources. This paper illustrates this potential by reporting the characteristics of Nd:YAG fiber oscillators. Fibers were grown by the laser-heated pedestal growth technique. They were made into lasers by (1) mounting several 60-250-µm diam, 5-15-mm sections in a holder for polishing purposes, (2) polishing and AR coating the ends, (3) placing the fibers in a flat mirror external cavity, and (4) end pumping a fiber through the back mirror with the focused beam of a cw Ar-ion laser (λ = 514.5 nm). Continuous-wave oscillation at 1.06 and 1.32 µm is demonstrated in over forty fibers, either in a guided or unguided mode. Thresholds as low as 3.5 mW and conversion efficiencies up to 31 % are observed, with output powers as high as 30 mW. Q-switched 1.06-µm fiber lasers are also demonstrated by mechanically vibrating the back mirror. A typical device output is 70-ns, 50-mW pulses at a 4-kHz rate. The mechanism responsible for residual fiber loss is scattering induced by fiber diameter variations (1-10%). Future devices made of fibers with improved diameter control (-“0.1%) should yield further reduction in threshold and the possibility of monolithic devices.
Review of coherent XUV sources: lasers and nonlinear optics
Authors: Bokor J.
Published: February 2023

Over the past several years, great progress has been made in the generation of coherent radiation in the extreme ultraviolet (XUV) spectral region. Several demonstrations of laser action have been reported as well as a wide variety of coherent sources based on nonlinear optical techniques such as harmonic generation, sum frequency generation, and anti-Stokes Raman scattering. Each type of source has a different combination of the following characteristics: wavelength, tunability, intensity, spectral width, efficiency, and repetition rate. The strengths and weaknesses of any particular generation technique depend on the application envisioned. A review of these developments is presented and comparisons among various sources are drawn with a selection of applications in mind.
Nonlinear channel waveguide devices
Authors: Gibbons Wayne M. , Pasternak A , Sarid Dror
Published: February 2023

Devices that perform all-optical signal processing are of interest in optical computing and optical communications. Two devices that have demonstrated such capabilities are the nonlinear directional coupler (NLDC) and the nonlinear Mach-Zehnder interferometer (NLMZ). In these devices the output intensity depends on the input intensity via the intensity-dependent refractive indices of the substrate and guide region, and the interference between the two channel waveguides. The reported performance of these devices to date has been rather inefficient. To optimize these devices, we have developed a theoretical model of the behavior when the substrate or the guide region is nonlinear, including both the reactive and dissipative terms as well as resonance effects. The software has been written using these models such that the user can vary guide and material parameters and achieve an optimum performance. We discuss and compare various materials and guide parameters that lead to optimized NLDC and NLMZ.
Analysis of strong light-matter interaction using a dressed propagator approach
Authors: Fujimoto James G. , Yee Ting K.
Published: February 2023

A diagrammatic density matrix technique is developed and applied to study nonlinear optical processes involving responses from weak probe fields interacting with a system under strong excitation. These diagrams consist of lowest-order double-Feynman diagrams which represent the density matrix perturbation terms describing the system response to the weak probe fields1,2 combined with dressed propagators which represent the density matrix elements of the system under strong excitation. The dressed propagators are described by a set of linear equations which, in most cases, may be derived in inspection. The methodology is similar to the bare-atom approach.2 The advantages of using this diagrammatic technique are that (1) it allows one to select and express analytically the dominant and appropriate density matrix elements (diagrams and dressed propagators); (2) analytical expressions may be constructed directly from the diagrams and thus lengthy calculations needed to obtain closed-form solutions are greatly reduced; (3) it provides a physical interpretation for the density matrix solutions and nonlinear optical processes; and (4) it may be generalized to more complicated, multilevel systems. We demonstrate the application of this technique to describe gain saturation, Stark splitting, and Raman scattering.
Spatial frequency influence on the perception of depth
Authors: Brown James M. , Weisstein Naomi
Published: February 2023

A close relationship has been shown between the spatial frequency of sine waves filling adjacent regions of 2-D figure/ground ambiguous pictures and the organization of those pictures into figure and ground (Wong and Weisstein, 1985; Klymenko and Weisstein, 1985). Areas filled with the relatively higher spatial frequency were predominantly perceived as figure in front of the lower spatial frequency filled ground areas. We report a similar spatial frequency effect on the organization of regions in depth that continued to dominate the perception even when conflicting disparity information was present. Our stimulus was a 3.3 (h) × 2.6 (1) degree rectangular region divided into four 0.825 × 2.6 degree sections. Alternate sections contained sinusoidal gratings of different spatial frequencies. Each spatial frequency was viewed in combination with every other spatial frequency, with one of the spatial frequencies always having disparity information present. Observers’ judgments of which sections were in front were significantly related to spatial frequency but not to disparity. Sections containing the relatively higher spatial frequency were seen in front even when the lower spatial frequency sections had disparity information designating them as nearer the observer. These results are interpreted in terms of a spatial frequency basis for figure/ground formation.
New stereo illusion induced by binocularly presented gratings: effects of orientation and spatial frequency
Authors: Chao Gung-Mei , Odom J. Vernon
Published: February 2023

We have investigated the parameters under which a new stereo illusion may be observed. If a single grating is viewed with both eyes, the grating appears to have several levels of depth. The levels of depth are simultaneously visible but are discontinuous with sharp borders at their boundaries. Photographic prints of square-wave gratings were viewed binocularly. The prints had a mean luminance of 150 cd/m2 and a contrast of 75%. The subject's task was to state the number of levels of depth seen. One (1) indicating a single surface, regardless of its appearance, was reported even if the surface appeared wavy, individual bars tilted in depth, or one level could be seen through a transparent second level without discontinuities. The sensation of several levels of depth disappeared if one (1) closed one eye and viewed the pattern monocularly, (2) oriented the pattern horizontally, or (3) increased or decreased the spatial frequency from an optimum of 3–4 cpd. Although the illusion is observed when a single grating is viewed binocularly, it can be accounted for, in part, by the same mechanisms which cause the illusion of a plane tilted in depth when two gratings of differing spatial frequencies are presented dichoptically.
Short-term adaptation does not null long-term visual aftereffects
Authors: Wolfe Jeremy
Published: February 2023

Four minutes of adaptation produces a tilt aftereffect (TAE) that can last for 2 weeks. One minute of adaptation can produce a large TAE but it disappears within minutes. TAE was measured using a tracking staircase method. Six naive subjects were tested during four minutes of adaptation in one direction, 1 min of adaptation in the opposite direction, and 5 min of recovery from adaptation. Four minutes of adaptation produced TAEs that reached an asymptote at 4.5° (avg). One minute of counteradaptation reversed the sign of the TAE, producing a significant −1.5° TAE. During recovery, the TAE reversed sign again, yielding a longterm TAE attributable to the initial adaptation (1.0°, p < 0.05). Two minutes of adaptation yields a 4.5° (avg) TAE but no long-term TAE. In a second experiment, 2 min adaptation was followed by 1 min counteradaptation. No TAE was seen during the recovery. There are two mechanisms and two sites of adaptation in the visual system: At the first site, fatigue of broadly tuned channels produces short-term aftereffects. At the second site, structural change in units that identify stimuli produces long-term aftereffects.
Comparative study of optical systems with various amplitude filters
Authors: Mondal P. K. , Murthy P. V. V. S.
Published: February 2023

It is now well known that a modification of the diffraction-limited point-spread function is possible by using various types of amplitude apodization filter. A comparative study of the performance of optical systems apodized with a few commonly used amplitude filters has been made. The comparison has been made from the considerations of the diffracted field characteristics, namely, point-spread function, encircled energy factor, Strehl ratio, second-order moment, mean apodization ratio, two-point resolution, etc. The imaging characteristics of extended objects, both periodic and nonperiodic in various conditions of coherence, have also been compared with special reference to optical transfer function, generalized frequency response function, image contrast, etc. Attempts have been made to correlate the functional form of the pupil function to the performance of the apodized optical system in terms of the various diffracted fields and the imaging characteristic parameters considered. Finally, experimental methods to fabricate a few of these filters for superresolution, image processing, etc. are described.
Rayleigh and other resolution criteria
Authors: Bennett H. E. , Elson J. M.
Published: February 2023

The Rayleigh resolution criterion, which states that two objects are just resolved when the maximum in the focal plane of one Airy pattern falls on the first minimum of the other, is described in nearly all optics books. The minimum between the two maxima is said to be 0.81 of the peak intensity. This value actually holds only for slit images such as are formed in spectroscopy or Fabry-Perot interferometry. For point sources such as stars, the minimum is 0.74, for example. Although mathematically elegant, the Rayleigh resolution is exceeded experimentally for some low-scatter optical systems, a result which has given rise to the less pessimistic Abbe and Sparrow criteria. On the other hand, if significant near-angle scattering exists and this background is not suppressed electronically, Rayleigh resolution may be unobtainable even for perfectly figured optical systems. As a working standard, the concept of diffraction-limited optics based on the Rayleigh criterion is thus useful provided that the values are not taken too seriously.
Halos, Sun Dogs, and Science
Authors: Greenler Robert G.
Published: February 2023

Many beautiful sky effects result from the interaction of sunlight with minute ice crystals falling through the air. Both familiar and unfamiliar, they can be seen by any interested person, with no special equipment. The origins of several sky effects will be discussed. Slides and demonstrations will illustrate the wealth of interesting things that can be seen in the sky.
Halley’s Comet
Authors: Maran Stephen P.
Published: February 2023

Halley’s Comet has been under surveillance since it was spotted with an advanced detector on the 200-in. telescope in October 1982. It has since shown unexpected variations. We want to know the nature of the frozen nucleus of the comet and the mostly unidentified parent molecules that compose it. When the comet is near perihelion in February, viewing conditions will be unfavorable from the ground, due to the comet’s proximity to the sun, but the Solar Maximum Mission and Pioneer Venus Orbiter will provide needed observations. In March, as the comet crosses the plane of the earth’s orbit, it will be explored by European, Japanese, and Soviet space probes as the Astro 1 battery of telescopes and cameras, operated by astronomers flying aboard the Space Shuttle, makes sophisticated analytical measurements from earth orbit. In late 1986, 1987, and afterward, as Halley’s Comet heads back toward the far reaches of the solar system, to return in 2061, the Hubble Space Telescope will follow the receding object as it passes beyond the reach of detectors on the ground. These modern studies are summarized in the context of the rich lore (artistic, historic, social, and scientific) of ancient and modern observations of Halley’s Comet, including the recent discovery of Babylonian observations from 164 B.C. that enable astronomers to refine the orbital calculations. Finally, viewing conditions for observers at various latitudes on the earth are summarized.
The individual contribution: what OSA members can do
Authors: Snyder Susan P.
Published: February 2023

As individuals, there are many ways in which we can become involved in improving the science education experiences of our children and community. This talk includes specific examples of how outside experts can influence the educational system.
Temperature dependence of a multimode biconical fiber coupler
Authors: Li YI-Fan , Lit John W. Y.
Published: February 2023

Based on the results of the coupling process in a multimode biconical fiber coupler,1 we have analyzed Its temperature dependence. We find that there are two cases which are dependent on both the geometry of the fiber and the material parameters. One is the temperature-sensitive area where the coupling efficiency of the coupler is very sensitive to the temperature, another is the temperature-nonsensitive area where the coupling efficiency of the coupler is almost independent of the temperature. So it is possible, in theory, to design fiber-optical temperature sensors as well as temperature-independent couplers, with a wide range of characteristics, by controlling the geometry of the fiber and also the material parameters such as refractive indices and temperature coefficients of refractive indices.
Laser-generated ripple patterns on dielectrics and intermediate band-gap semiconductors
Authors: Mansour Nastaran , Reali Giancarlo , Soileau M. J.
Published: February 2023

We report the results of studies of laser-generated ripple patterns on intermediate gap semiconductors (e.g., ZnS, ZnSe) and dielectrics of various indices of refraction. The experiment has been carried out at normal incidence using mainly a CO2 TEA laser which produced TEM00 pulses of 150-ns duration. Preliminary results of irradiation with 1.06 µm, 15-ns pulses have also been produced. The results confirmed the formation of coherent structures on the front or rear surface of a damaged material. In particular, for a variety of transparent dielectrics, we carefully determined the ripple spacing (X/n) through microscopic observation and by diffraction pattern measurements. The ripple spacing and direction are in gross agreement with prior observations by other workers. Similar measurements on front and rear surfaces of ZnS and ZnSe revealed the presence of domains of regularly spaced ripple formations and fine structure superimposed parallel to the main pattern. Such fine structures are also present in the damaged dielectric samples although to a much less extent. Furthermore, a wrong orientation (parallel to the applied electric field) of the induced gratings was sometimes observed. The observed ripple spacings and orientation for ZnSe and ZnS cannot be completely explained with existing models.
Measurements of beam fanning in barium titanate
Authors: Tobin M. S. , Stead M. R.
Published: February 2023

Asymmetric self-defocusing in barium titanate (BaTiO3) was first reported by Feinberg.1 Similar effects have been observed in SBN and other photorefractive materials.2 Cronin-Golomb and Yariv have demonstrated the use of this effect as an optical limiter.3 We present measurements of beam fanning in BaTiO3 at a number of wavelengths using cw lasers and a frequency-doubled Nd:YAG laser. We observe that the time dependence of fanning is approximately I
−
0.5 at the higher intensities of the pulsed laser. The efficiency of the fanning improved, particularly in the pulsed case, as the crystal was cooled to near 10°C.
Optical enhancement of degraded fingerprints
Authors: Olimb Hal E. , Krile Thomas F. , Walkup John F.
Published: February 2023

The identifying features of degraded fingerprints are optically enhanced with a coherent optical processor. The spatial and spatial frequency information contained in a fingerprint and its Fourier transform are located and characterized. A spectral model is developed for each of the basic ridge pattern types. The ridges and the ridge pattern details are enhanced by filters generated from these spectral models. Experimental results are shown.
Psychophysical measurement of diurnal variation in human visual sensitivity
Authors: O’Keefe Lawrence P. , Baker Howard D.
Published: February 2023

Circadian rhythms of physiological processes in the retina such as disk shedding, dopamine levels, and melatonin levels have been a topic of recent research interest. These physiological rhythms suggest the possibility of corresponding rhythms in visual sensitivity. To examine this possibility, we obtained psychophysical dark adaptation curves using a digitally controlled two-channel Maxwellian view adaptometer at 2-h intervals around the clock. One curve was obtained at a randomly selected time per day, and at least 24 h elapsed between test sessions. Cone and rod terminal thresholds as well as time constants for recovery of sensitivity were compared for different times of day. Preliminary results indicate an increase in threshold for both cones and rods in the middle of the night (2-4 a.m.) compared with all other times, with no apparent change in time constant of recovery. These results confirm a recent report1 but contradict an earlier report2 which showed a decrease in threshold in the middle of the night. Methodological differences which may contribute to the discrepant results will be discussed. Further testing includes the use of a two-alternative forced choice procedure intended to give a measure of observer criterion changes over time of day.
Cylindrical lenses radius of curvature measurements
Authors: Pedraza J. , Diaz R. , Cordero A. , Cardona O. , Cornejo A.
Published: February 2023

Using the principle that for a spherical surface the nodal points coincide with the center of curvature,1 a technique was previously developed2 for measuring the radius of curvature r of such surfaces. The basic equipment required is a low-power He-Ne laser and a nodal bench. In this paper this technique is extended for cylindrical and toric lenses. For these types of lens, the measurements are taken along one or two perpendicular directions, depending on the type of lens. The present method also allows the measurement of decenterings and wedges in the lenses. If modest equipment is used, the accuracy for r is ±0.05 mm, and for wedges it is ±0.7′.
X-ray microscopy with synchrotron radiation
Authors: Rarback Harvey , Jacobsen Christopher , Kenney John , Kirz Janos , Rosser Roy
Published: February 2023

Soft x rays are an excellent probe for high spatial resolution detection of low atomic number specimens. We have developed a scanning microscope at the National Synchrotron Light Source (NSLS) which uses a small (~0.2-μm) spot of x rays in the 24-44-Å wavelength range. The microscope can form transmission images in real time at a fixed wavelength, or, by making an image of the difference in transmission on either side of an element's absorption edge, it can make a high resolution map of that element’s concentration. We have used the microscope primarily for imaging and microanalysis of biological specimens. However, with minor modifications the instrument can be used for high resolution material science studies of surfaces or bulk specimens without the requirements of excessive specimen thinning or vacuum compatibility presently required by electron probe instruments. The x-ray probe is presently formed by a Fresnel zone plate fabricated at IBM using electron-beam lithography. We will improve the resolution considerably with higher resolution zone plates fabricated by a variety of techniques. We will also increase the throughput of the instrument several orders of magnitude by moving from a bending magnet source of synchrotron radiation to the soft x-ray undulator soon to be installed on the x-ray storage ring at the NSLS. With these improvements we plan to make high resolution (< 1000-Å) scanned images in <1 min.
Ultrahigh vacuum reflectometer for use with synchrotron radiation
Authors: Hunter W. R. , Rife J. C.
Published: February 2023

An ultrahigh vacuum reflectometer has been built for the Naval Research Laboratory beamline at the National Synchrotron Light Source at Brookhaven National Laboratory. This beamline contains the grating/crystal monochromator1 that has a wavelength range of 2000-5 Å. The combination of these facilities permits reflectometry over a very wide spectral range for studies of optical constants, reflectance measurements of multilayer coatings, scattering, and simple diffraction grating efficiency measurements. The samples can be rotated about their normals to allow measurements on anisotropic samples at different orientations of a selected surface direction with respect to the polarized radiation. The detector rotates around the sample center in the plane of incidence for specular and in-plane scattering measurements. In addition, its altitude can be changed with respect to the incidence plane so that out-of-plane measurements can also be made. A variety of detectors can be used and the detector mount can accommodate more than one detector at a time if desired. An ultrahigh vacuum sample preparation and transfer station is under construction so that atomically clean surfaces can be prepared and a number of samples can be measured in succession without venting the reflectometer to air.