bluuebunny/crossref_metadata_2025 huggingface dataset:
Correlation experiments with a binary phase-only filter
Authors: Flavin Mary A. , Horner Joseph L.
Published: February 2023

Computer simulations of optical correlations have shown that binary phase-only filters (BPOF) produce large narrow correlation peaks with good target discriminations, high optical efficiency, and virtually no sidelobes. A 256- × 256-element BPOF was fabricated in etched quartz from the binarized phase of the Fourier transform of an input image. The filter was fabricated by reactive ion etching techniques in a VLSI foundry. Initial experimental results produced an intense narrow correlation peak 6.2 times higher than the secondary peak with the full width at half-maximum corresponding to three pixels. Additional experimental data are presented and compared to computer simulations.
Effects of SLM pixel dead zone on correlator performance
Authors: Horner Joseph L. , Gianino Peter D.
Published: February 2023

Spatial light modulators (SLMs) are generally pixeled structures with less than the full area of the pixel responding to the input signal. This inactive area, or dead zone, leads to distortions in optical correlator performance due to increased noise when the correlator uses SLMs in the input and filter planes. The problem is studied through computer simulation and by a closed form mathematical analysis. Three different correlation filter types are analyzed. Results are presented in the form of output SNR as a function of percent dead zone area.
Coherence determines speed discrimination of plaids
Authors: Bowne Samuel F. , Welch Leslie
Published: February 2023

Adelson and Movshon [Nature London 300, 523 (1982)] have proposed a two-stage model to solve the aperture problem; the velocities of the components of a complex target are separately extracted and then combined to form the percept of a rigidly moving object. Welch [ARVO (1988)] has presented data that support their model by illustrating two separate stages that can limit speed discrimination thresholds. What rules are used to combine motion information at the object-motion stage? We used plaids composed of two sinusoidal gratings: a mask grating which varied randomly in contrast, orientation, or speed and a test grating. Speed discrimination for the test grating was unaffected by contrast variations but was strongly impaired by speed or orientation variations of the masking grating. Since contrast does not affect the speed of the plaid pattern and speed and angle both do, speed discrimination must be based on the plaid pattern speed even when better information is available in the test grating alone. The degree of masking depends on how well the two gratings cohere to make a rigid plaid; the less they cohere the less masking is seen, with the paradoxical result that a high-contrast mask has less effect than a mask of moderate contrast.
Spatial frequency affects perceived direction of a moving plaid
Authors: Kooi Frank L. , Grosof David H. , De Valois Karen K. , De Valois Russell L.
Published: February 2023

When a plaid made by superimposing two orthogonal sine wave gratings is moved, the apparent direction of motion is dependent on the contrasts and the relative spatial frequencies of the component gratings. We measured the apparent direction of plaids with 1 and 1.5-cycle/deg components. Because these patterns partially slide (i.e., are not completely coherent) the task was to respond to the main direction of motion. When scaled for equal multiples of threshold (equal visibility), the lower-spatial-frequency component dominates the direction of motion, indicating a disproportionally larger influence of low spatial frequencies on the motion system. The directional shift can be eliminated or even reversed by increasing the contrast of the high-spatial-frequency component relative to the low. However, the addition of contrast to the high-spatial-frequency component has less effect when the average contrast of the plaid is increased, suggesting a compressive contrast nonlinearity in the motion system. The movement characteristics of a red-green color plaid are similar to those of a low- contrast luminance plaid. The motion of the color plaid may be determined primarily by the small luminance distortions that are inevitably present due to chromatic aberrations.
Two combined lateral correlation-enhancing techniques to Improve Image transmission using phase conjugation through a phasedistorting medium
Authors: Ikeda Osamu
Published: February 2023

A phase-conjugated wave can reconstruct the original field even through a phase-distorting medium. Making use of this characteristic, the author and others have proposed superimposing the transmitting field from a phase conjugator onto the phase-disorting medium region to obtain a good transmitted image quality regardless of the position of the distorted region. The method, however, is effective only when the phase-distorting region is represented by a single phase-distorting layer. A novel method is proposed to apply the image transmission system even for a general class of phase-distorting medium. The method consists of (1) imaging the transmitting field onto a plane in the middle of the phase-distorting medium region and (2) maximizing the factor of magnification of the imaging. The latter operation can further reduce the effects of the phase distortions through enhancing the lateral correlation. The principle is explained analytically with basic experimental results.
Competition and cooperation in optical neural networks using gain, loss, and feedback
Authors: Lininger Diana M. , Anderson Dana M.
Published: February 2023

The notion of competition and cooperation among patterns of activity is common to many models of neural networks, for example, those employing lateral inhibition. We show how these can be implemented using a combination of saturable gain and loss in a feedback configuration. Patterns compete for the energy supplied by the gain medium, but they cooperate in saturating the loss mechanism. Feedback provides the necessary iteration so that a winner can prevail. By judicious choice of optical geometry, one can tailor the balance of the two interactions. For associative memory, small signal loss magnitude is chosen to exceed small signal gain, but the loss is made to saturate at a lower intensity. Gain is placed in an image plane while loss is placed in a Fourier plane. This gives a dynamic indicative of multistability among the patterns.
Novel squeezed-state detection method
Authors: Yurke B.
Published: February 2023

As an alternative to homodyne detection, a particle scattering technique is described by which squeezing can be detected. The particle scattering off of the squeezed boson field need not be a photon and the boson field need not be the electromagnetic field. This detection method may thus be particularly useful for systems for which high-efficiency quantum counters such as photodetectors are not available (squeezed phonons, for example). The detection method takes advantage of a coherence that can be established between a scattering process which involves the emission of a boson into the squeezed boson field and that which involves the absorption of a boson from the squeezed boson field. Such a coherence is established by first preparing the particle in a superposition of two energy eigenstates whose energies differ by 2ħω2, where ω
q
is the oscillation frequency of the mode of the boson field which has been squeezed. When the coherence between the two scattering processes gives rise to destructive interference, the scattering rate can be greatly inhibited below that when the boson field is in its vacuum state. Squeezing thus can manifest itself as a reduction in a scattering rate.
Properties of 3-D imaging systems
Authors: Hudson Scott , Brady David , Psaltis Demetri
Published: February 2023

We discuss the problem of specifying and reconstructing 3-D objects using electromagnetic fields. This problem is of interest in volume holographic optical information processing and in 3-D imaging systems such as synthetic aperture radars. In systems, such as optical neural computers, which make efficient use of large scale holographic transformations, volume holographic optical elements offer the potential for information storage at very high spatial densities. To realize this potential it is necessary to overcome the bottleneck on the recording and reconstruction of volume holograms created by the limited space–bandwidth product of the entrance aperture of a volume medium. Only N2 of the N3 degrees of freedom of the volume may be recorded or read out by a single monochromatic exposure. In general, at least N monochromatic exposures are necessary to specify or reconstruct fully a volume hologram. Under polychromatic illumination, a volume hologram may be recorded in a single exposure if the recording beam contains at least N independently controllable frequency components. By decomposing the 3-D field into the eigenfunctions of an imaging system we demonstrate specific limitations on the recording and reconstruction of 3-D information using optical fields. We present a method for writing volume holograms based on eigenmode decomposition of the desired field. Finally, we discuss the amount of information needed to reconstruct targets with fractal dimension between 2 and 3.
Layered synthetic microstructures with graded layer boundaries for the VUV and soft x-ray spectral regions
Authors: Hunter W. R.
Published: February 2023

Until recently abrupt boundaries between layers were considered to be a requirement tor the proper operation of multilayer interference filters. This requirement has changed with the introduction of rugate filters which have graded-index boundaries between layers. Although the rugate filter has heretofore been confined to the spectral regions where nonabsorbing layers are available, the idea can also be applied to LSMs for the VUV and soft x rays where the layers are absorbing. For this application both the index of refraction and extinction coefficient must be graded. Calculations made using profiles employed in rugate filter design as well as other profiles have shown good suppression of higher-order interference but somewhat reduced first-order reflections. Results of the calculations are shown and some speculations made as to how such a filter can be constructed.
Narcissus reduction techniques used in the optical design of FLIR systems
Authors: Spencer Harvey M.
Published: February 2023

A ray tracing method was developed to quantify the relationship between narcissus and lens bending for lenses in an IR optical system. Low narcissus solutions are automatically predicted.
Irreducible aberrations of a lens used for a range of magnifications
Authors: Walther Adriaan
Published: February 2023

Maxwell has proved that a lens cannot be free from aberrations at more than one magnification. Yet many lenses, with SLR macrolenses and photographic enlarger lenses as obvious examples, are used over a wide range of magnifications. What are the theoretical limitations on the performance of these lenses? We use eikonal function theory to examine this question and obtain practical results by using numerical techniques rather than conventional series developments. The lens is represented by an eikonal not fully determined by the external constraints and, therefore, depending on a number of parameters freely at our disposal. The aberrations for various magnifications are determined by an iterative ray tracing process,1 and, using a suitable merit function, the eikonal is optimized by variation of the free parameters. The resulting ray trace curves show the best image quality possible in the conditions imposed, no matter how complicated we make the lens. We show detailed results for a 50-mm f/2.8 SLR macrolens.
Ray tracing on a spreadsheet
Authors: Toomey T. J. , Zavislan J. M.
Published: February 2023

In today’s workplace, the personal computer and spreadsheet have become commonplace, while lens design software, often costing more than the computer, is not. Any one of the generic spreadsheet programs can be an effective ray tracing tool. Anyone who has developed ray tracing software has found that the input/output problem can often be more difficult than the algorithms for ray tracing. The advancement in today’s spreadsheets has eliminated the need for sophisticated programming skills to produce usable ray tracing functions. The worksheet developed combines third-order ray tracing with aproximate polarization equations. Useful graphic functions can be developed for displaying the third-order surface contributions and the polarization change for each surface. Examples of the macros developed are shown. A demonstration of a double Gauss ray trace is given. These macros can also be a useful tool for those with high powered lens design software. The macros are designed so that a lens can be set up in the spreadsheet and used as the input to commercially available lens design software.
The triplet: an embarrassment of riches
Authors: Shafer David
Published: February 2023

The well-known Cooke triplet design has been around for a long time. It has just enough degrees of freedom to correct all five third-order aberrations, as well as longitudinal and lateral color. In practice, third-order residuals are introduced to balance fifth-order aberrations, which are quite bad. In a system this simple, one would not expect there to be multiple solutions. This paper is about a very large number of discrete new triplet types, most of which do not look anything like the traditional Cooke design. This is achieved by giving up color correlation and using at least one thick element, ususlly a strongly curved shell.
Resolution as dipole and quadrupole detection
Authors: Carney Thom , Klein Stanley , Levi Dennis
Published: February 2023

We measured resolution of edge (the line) blur as a function of edge (and line) contrast. Previous attempts to predict resolution thresholds involved many modeling assumptions concerning the visual system’s sensitivity and/or the retinal sampling density. Our goal is to avoid assumptions by measuring the visibility of those multipoles that are used in the resolution task. The task of discriminating edge (or line) blur is equivalent to the task of detecting a dipole (or quadrupole) test pattern in the presence of the edge (or line) pedestal. The multipole test threshold can be related to the variance of the blur by using the relationship

P

v
+
ε

(
x
)
=

P
v

(
x
)
+
0.5
ε

P
v

′
′

(
x
)
+
O

(

ε
2

)

, where P
v
(x) is an edge or line with a blur of variance v and where ϵ (with units of min2) is the ratio of test threshold to pedestal strength. A sample result is that a dipole of 4 % min2 strength was visible on a 100 % contrast edge pedestal, corresponding to a blur variance of 0.04 min2 (equal to a standard deviation of 0.2 min or a 0.28-min separation between a pair of lines). This small resolution threshold would be surprising in terms of the retinal sampling density but is not surprising in terms of our test-pedestal approach.
Spatial uncertainty and spatial resolution
Authors: Lasley David J. , Cohn Theodore E.
Published: February 2023

An observer’s ability to detect a threshold visual target depends on his knowledge of stimulus parameters, such as the target’s color, and its spatial and temporal locus. Withholding knowledge of the spatial locus of a visual acuity target should depress visual resolution because of the close theoretical relationship between spatial resolving power and contrast sensitivity. We have examined the effects of several spatial target parameters in a visual resolution task where spatial uncertainty was present. Twelve closed E patterns (which resembled rectangular figure eights) were continuously displayed on a video monitor in a 1° diam clockface pattern. The stimulus was a 200-ms removal of the left or right vertical bar that closed the E, and the task of subjects was to identify which. Our results suggest that left and right facing E values are equally detectable. E values on-axis (3, 12, 9, and 6 o’clock positions) were more visible than E values presented off-axis (1, 4, 5, etc. o’clock). Controlling for the factor of position, sensitivity d' for randomly presented E values, in one of twelve loci, was depressed by a factor just less than the square root of the number 12 of stimulus alternatives, which is the prediction of signal detection theory for the ideal observer.
Optical switching and limiting in a polymer dispersed liquid crystal film
Authors: Sutherland Richard L. , Orbits George C.
Published: February 2023

We have investigated optical switching and limiting by electrooptically controlled light scattering in a medium consisting of nematic liquid crystal (NLC) droplets embedded in a thin polymer matrix sandwiched between transparent electrodes. With no applied field, the medium is highly scattering. At sufficiently high voltages, the medium becomes optically clear. In our experiments, an unpolarized 0.5-mW He-Ne laser irradiates the composite film. A bias voltage is applied to select an initial film transmittance. The transmitted light is detected, amplified, and added to the bias voltage. With positive feedback, this device exhibits optical bistability. The hysteresis curves are characterized by very sharp thresholds for both on and off switching and a high contrast between these states. At higher bias voltages, the device exhibits self-pulsations, which we believe are related to noise-induced switching. The frequency of the self-pulsations decreases with increasing optical power. A distinct optical bounce appears in the switch oFF portion of the pulsations, which may be related to electrical polarization or NLC shear flow effects. When the device is configured with negative feedback, it functions as an optical power limiter. Limiting powers are functions of bias voltage and feedback gain.
Squeezed states in the context of Langevin equations and nonpositive-definite diffusion coefficients
Authors: Davis Nolan R. , Cantrell C. D.
Published: February 2023

We consider a vector c-number Langevin equation describing a single mode of the radiation field under the influence of a quadratic nonlinear interaction. The nonlinearity of the interaction is found to give rise to a nonzero diffusion matrix which may be nonpositive-definite. Using this diffusion matrix, we derive and solve an equation for the variance matrix of the system. An analysis of the solution then yields information about the production and properties of squeezing. In particular, we find that pulsed pumping of the medium, compared to continuous pumping, can significantly enhance the maximum level of squeezing. Finally, we delineate the role of the nonpositive-definite diffusion matrix through a discussion of the physical source of squeezing.
Ten percent efficient anti-Stokes generation of 225-nm light
Authors: Reiser C. , Raymond T. D. , Michie Robert B.
Published: February 2023

Although considerable interest has been paid recently to Raman Stokes shifting in hydrogen, very little attention has been paid to nonlinear upconversion via anti-Stokes shifting. This disinterest is due largely to low experimental yields (typically <2%) caused by Stokes-anti-Stokes gain suppression when the laser beam is focused into the hydrogen cell. The fact that the anti-Stokes light emerges from the cell in a cone also detracts from its usefulness. By contrast, our anti-Stokes work uses collimated input light so that the emerging anti-Stokes wave is a filled-in propagatable beam. By choosing the conditions at the input of the Raman cell appropriately, we have demonstrated 10% conversion of KrF laser light at 248 nm to an anti-Stokes beam at 225 nm. We found that the single most important condition to obtaining good efficiency is to coinject into the hydrogen cell a phase-matched Stokes beam that has ~5 % of the energy of the 248-nm pump beam. This technique should be applicable to pumping with other lasers as well. The effects of beam quality, transient response, and other experimental conditions are discussed.
Numerical experiments for stimulated rotational Raman scattering in N2
Authors: Parazzoli C. G. , Capps D. M.
Published: February 2023

Rotational Raman scattering involves simultaneous transitions from a number of molecular levels. The rotational Raman in N2 is complex due to the following effects:

(1) simultaneous Raman transitions coupled through pump and rotational level populations;

(2) multiphoton processes;

(3) Stokes-anti-Stokes gain competition;

(4)degeneracy of the rotational lines.
Ferroelectric liquid crystal electrooptic devices
Authors: Johnson Kristina M.
Published: February 2023

Meyer et al. showed in 1975 that in certain conditions smectic c liquid crystals will be ferroelectric with a macroscopic polarization p lying in the (x, y) plane of the molecular layers. In 1980, Clark and Lagerwall demonstrated a submicrosecond liquid crystal switch by inducing ferroelectricity in 2 [cf9]m[cf341]m of LC material surface stabilized between two glass plates. This tutorial discusses the present and fundamental operating characteristics of ferroelectric LCs including response time, contrast ratio, switching energy, resolution, and size in optical interconnection, neurocomputing, switching, and displays.
Electrooptic application of ferroelectric liquid crystals
Authors: Clark Noel A.
Published: February 2023

Ferroelectric liquid crystals (FLCs) exhibit electrooptic switching resulting in significant reorientation (Δθ ~ 20–45°) of the optic axis of a medium with a large-index anisotropy (Δn ~ 0.2). The resulting effects make possible a variety of novel electrooptic devices with applications in displays, optical computing, integrated optics, and research electrooptics. I review recent FLC developments including basic cell physics, switching devices employing birefringence, total internal reflection, and waveguide geometries. Various applications are discussed.
Conical emission and coherent sideband generation in laser propagation
Authors: Crenshaw M. E. , Cantrell C. D.
Published: February 2023

Computational results show that the conical emission and Rabi sidebands observed when a nearly resonant laser pulse propagates through an atomic vapor are the result of the breakup of the pulse into solitary waves. For an incident pulse with a transverse as well as a temporal profile, the crests and troughs of the 2-D solitary waves are curved in a time-radius plane. The temporal modulation associated with pulse breakup appears as Rabi sidebands in the spectrum, while the curvature of the solitary waves in the time-radius plane results in a transverse spatial modulation, resulting in conical emission in the far field. These results were obtained by performing detailed numerical calculations of the time-dependent paraxial propagation of a cylindrically symmetric laser pulse through a vapor of two-level atoms. Our results can be interpreted readily in terms of optical nutation on the Bloch sphere and in terms of noncollinear phase matching through the curvature of the solitary waves rather than through additional parametrically generated waves. The cone opening angle depends on the initial transverse profile of the pulse and the process of beam breakup as well as self-focusing.
New geometrical model for the fundamental mode of a Gaussian beam in oblate spherical coordinates
Authors: Landesman B. Tehan
Published: February 2023

This paper provides a simple but precise geometrical interpretation for the mathematical description of the zero-order mode of a Gaussian beam, which is an exact solution to the scalar wave equation. The geometrical model is expressed in the oblate spheroidal coordinate system where the beam wavefront is a section of an oblate ellipse, and a contour of constant amplitude is a hyperboloid of one sheet. The model employs the concept of a skew-line generator of a hyperboloid of one sheet as a real raylike element. The geometrical properties of an individual skew line and families of skew lines are discussed in detail and are compared to real rays. The model enables a simple interpretation of the presence in the beam description of a pure phase term, which has an arctangent dependence. Specifically, it represents the sag of an oblate ellipse as measured along a skew line. Finally, we use the skew line to build a nonorthogonal coordinate system, which provides the unambiguous framework necessary for studying the straight-line propagation of Gaussian beams in various media.
Mode switching and quantum fluctuations in multimode dye lasers
Authors: McMackin I. , Beck M. , Raymer M. G.
Published: February 2023

We present the results of numerical and experimental investigations into the behavior of multi-mode dye lasers. In an experimental investigation of a two-mirror concentric-cavity dye laser, we find that the individual-mode-intensity fluctuations are qualitatively different from those in a three-mirror laser. The fluctuations in the two-mirror laser display a switching behavior in which the average time that each mode is off can exceed the average time that it is on. The time-averaged optical spectrum is found to contain many modes at all pump powers, which is in contrast to results from a three-mirror laser. The rf spectum of the total intensity indicates that spatial hole burning significantly affects which modes lase simultaneously. The fluctuation behavior of the mode amplitudes in an ideal three-mirror dye laser near threshold is investigated numerically. We have determined how near to threshold the laser must be operated so that quantum noise is the dominant cause of the intensity fluctuations of the individual modes. Higher above threshold the fluctuations caused by four-wave mixing of the laser modes in the gain medium dominate quantum fluctuations.
Model for contrast perception: relationship between response pooling and the contrast transducer function
Authors: Cannon Mark W.
Published: February 2023

A 2-D model consisting of an array of self-similar Gabor filters (bandwidth = 1 octave) followed by a power function contrast transducer (exponent = 0.5) and response pooling across spatial frequency and orientation using the Quick summation rule (exponent Q = 2.5) was shown to simulate accurately human estimates of apparent contrast [ARVO (1988)]. However, magnitude estimation experiments indicate that the contrast transducer exponent could be anywhere between 0.3 and 0.7. To test the robustness of the original estimates of filter bandwidth and Q, model estimates were compared to contrast matching data when contrast transducer function exponents ranged from 0.1 to 0.7. Results demonstrated that filter bandwidth estimates remained constant, but the Q value required to give the best fit between model and data was found to be a function of the contrast transducer exponent. Further tests of the model when the Gabor filters were replaced by different of Gaussians or a difference of three Gaussians showed that model performance was still better for bandwidths near 1 octave and showed exactly the same functional relationship between Q and the contrast transducer exponent. Thus, while model performance is relatively independent of the exact mathematical form of the filters, the final specification of Q for response pooling requires a more accurate description of the contrast transducer function.
Immersed beamdivider that transmits s polarization
Authors: Baumeister Phillip W.
Published: February 2023

The goal is a coating composed of nonabsorbing layers that manifests relatively high reflectance at a wavelength λ0 for the p polarization and low reflectance for s polarization, where the incident medium and substrate have an index of 1.52 and the incidence angle is 45°. In other words, the coating is in a cemented cube. Its design is where p is the number of times the basic period is repeated. H and L represent layers of optical thickness λ0/4 (matched at 45°) and refractive indices n
h
and n
L
, respectively. The single layer in AR1 dereflects at a wavelength λ0 the interface between glass and a massive medium of index n
H
for s polarization. The single layer in AR2 dereflects at a wavelength λ0 the interface between a massive medium of index n
H
and a massive medium of index n
L
for s polarization.
Dispersion curve gaps observed in optical emission
Authors: Gruhlke R. W. , Hall Dennis G.
Published: February 2023

Coupled surface plasmon as well as waveguide excitations are supported in corrugated photoresist-metal-photoresist geometries. At particular wavelengths, forward and backward propagating excitations are phase matched via the sinusoidal corrugation. This results in second-order Bragg scattering of these excitations into the far-field radiation zone of a sample. Detection of the radiation reveals momentum as well as energy gaps in the dispersion curves of the excitations. These gaps are investigated for different combinations of interacting excitations and for two different detection techniques: fixed angle scan in wavelength or fixed wavelength scan in angle.
Computer-generated holograms of three-dimensional objects
Authors: Leseberg Detlef
Published: February 2023

In a variety of applications computers acquire or generate the data which represent 3-D objects, e.g., tomography and computer graphics. holography could be an adequate display technique, and it is possible to generate holograms using computers. The most important step to be considered is calculation of the complex amplitude. Suitable techniques and special schemes are reviewed. Several techniques simulate the wave propagation from the 3-D object to the hologram plane: (a) analytic solutions of the wave equation, especially conical waves which achieve segments of line foci; (b) diffracted fields are determined by a Fresnel transformation, and tilted input planes require an additional coordinate transformation. The boundary conditions of an optical recording step do not apply to a generation by computer, but there remain the boundary conditions of the optical reconstruction step. Synthetic techniques are possible: (c) the complex amplitude distributions are modified for each plane in-depth individually to reduce the computing time some orders of magnitude; (d) the assumption of a slitlike exit pupil leads to a separation of the calculation in 1-D Fresnel transforms and makes it possible to reconstruct in white light.
Removing the common signal: a unifying principle for color constancy and color induction
Authors: Blackwell K. Tiplitz , Buchsbaum G.
Published: February 2023

A principle of color image processing by the visual system is presented which accounts for both color constancy and chromatic induction. The principle proposes that color constancy and chromatic induction are mediated by the removal of a signal common to all subfields of a scene. Color constancy results because most of the common signal is due to the illuminant. Chromatic induction results because part of the common signal is due to the similarity in reflectances. A model of visual color image processing is presented which incorporates the common signal principle and accounts for color constancy and chromatic induction. A major difference from earlier models of color constancy is that the present model does not require the separation of the incoming signal into an illuminant and reflectance. The model is tested with data collected from experiments which quantified color constancy and chromatic induction. The possible physiological correlate of the model suggests that the operations involved in removing the common signal can be implemented by the retina.
Brightness contrast from adjacent and nonadjacent lights
Authors: Shevell Steven K. , Holliday Ian E. , Whittle Paul
Published: February 2023

The brightness of a small patch of light depends on the luminance of the light itself and other lights nearby. We examine the neural level within the visual system at which a remote noncontiguous light in the visual field affects the brightness of a test patch. Consider a 20′ test, a 3° surround, and a 3-5.4° outer ring adjacent to the surround. Initially we quantified the change of brightness caused by the remote outer ring by directly matching a comparison standard to the brightness of the test-with-surround, first with and then without the outer ring. As expected, the outer ring affected the brightness matches. In the next experiment, the test and comparison standard were presented haploscopically: in each eye, an outer ring enclosed a circular field surrounding a small patch, as before. The patch in the left eye was the comparison patch and was presented to the left of center (although still well within the circular surround); the patch in the right eye was the test patch, presented to the right of center. The fused percept was a single outer ring, a single surround, and two small separated patches. The outer ring had little or no effect on the haploscopic brightness matches. The results can be accounted for by adjacent surrounds affecting neural signals at the retinal level and more remote lights affecting signals after binocular combination. A necessary condition of the outer rings disturbing a brightness match may be that the two surrounds are seen as different in brightness.
Characterization of garnet films for magnetostatic wave modulation of light
Authors: Butler John C. , Kramer John J. , Craig Alan E. , Lee John N.
Published: February 2023

The goal of the present work at the laboratory is the construction of a magnetostatic wave optical modulator. To accomplish said goal, material must be found that permits guided optical modes to propagate with low attenuation, possesses high Faraday rotation (to produce high diffraction efficiencies), and has a narrow ferrimagnetic linewidth to allow the magnetostatic waves to operate at high frequencies with little attenuation. Presently the material of choice is yttrium iron garnet (YIG) but Bi-substituted YIG offers improved Faraday rotation with little or no increase in optical absorption, as indicated by the magnetooptic figure of merit (Faraday rotation divided by the optical absorption). The Faraday rotation of Bi-containing film and an unsubstituted YIG film was measured at a wavelength of 1.3 μm. The technique employs the extinction method utilizing a rotatable analyzer and uses a curve fitting scheme to calculate the total rotation of the saturated samples. The optical absorption coefficient of both Bi substituted and unsubstituted YIG films was measured using a guided wave technique. This technique scans the surface of the waveguide, collecting scattered light using a fiber-optic bundle. Additionally ferrimagnetic resonance linewidth measurements were carried out on thin films of Bi-substituted YIG using a modified cavity technique.
Rhomb gratings for sideband suppression in free-electron lasers
Authors: Wantuck Paul J. , Appert Quentin D. , Pistoresi Denis J. , Tong Kwok-On
Published: February 2023

A diffraction grating rhomb remains the most viable candidate for sideband suppression and optical beam outcoupling in rf-driven free-electron lasers. A pefect rhomb is defined by the positioning of two equal period diffraction gratings so that the grating surfaces and grooves are parallel. The sideband light components, generated in the wiggler section of the laser, interfere with the energy extracted from the electron beam and reduce laser efficiency. Since the group travel time of light in free space through the rhomb is an increasing function of wavelength, the transmit time of the sideband components will differ from the fundamental and thus eliminate the temporal (and spatial) overlap between these components and the electron beam pulse in the wiggler.
Reciprocity in the propagation of wave fields
Authors: Carter William H.
Published: February 2023

A reciprocity theorem1 widely used in the design of antennas treats antennas as part of an electronic circuit and relates the input and output currents and voltages. Some limited work has been done to obtain reciprocity theorems for the electromagnetic fields themselves,2 but this work does not provide explicit mathematical expressions relating to the propagation of reciprocal fields. We give a proof for the following theorem. If two wave fields taken one at a time within a source-free, isotropic, and homogeneous medium are composed only of homogeneous plane waves so that their angular spectra are related by they are defined to be reciprocal so that the forward propagator in a diffraction integral for one field is the complex conjugate for the inverse propagator in a similar inverse diffraction integral for the other field.
Reciprocity relations for a beam splitter
Authors: Ou Z. Y. , Mandel Leonard
Published: February 2023

By considering the beam splitter as part of a Michelson interferometer and applying a simple energy balance argument to the input and output, we obtain reciprocity relations connecting the complex reflectivities and transmittivities on both sides of the beam splitter. The results hold for any nonabsorbing beam splitter whose refractive index varies only in one direction, whether the medium is stratified or continuous. The corresponding results for a quantum field falling on the beam splitter are discussed.
Direction cosine space diagram
Authors: Goodman Douglas S. , Watson IBM T. J.
Published: February 2023

The direction cosine space representation of angles relates more directly to fundamental physics than the more common θ and ϕ specifications. Consequently, geometrical optics, radiometry, diffraction, and interference can be better unified. Directions and ranges of directions can be displayed with a simple diagram. If (α, β, γ) are the direction cosines, points in an (α, β) coordinate system represent directions and areas show ranges of direction. Many basic results can be obtained trivially with this diagram. For example, it is easily seen that brightness is conserved by refraction at plane surfaces and single-order diffraction by gratings. In addition, many quantities are actually in direction cosine space without this being realized. For example, the pupil function is properly represented in this space, as are computations involving it, for example, the evaluation of the OTF. The fundamental radiometric quantity ∫dΩ cosθ is an area in the cosine space diagram, as is π sin2θ, a radiometric quantity associated with imaging systems. The direction-cosine space diagram also facilitates understanding of multidimensional phase space, which can be represented by a diagram of diagrams involving both position and direction.
Propagation of the spectral correlation function in a homogeneous medium
Authors: McKechnie T. S. , Carniglia Charles K.
Published: February 2023

When two infinitely extensive electromagnetic waves of wavelengths λ1, and λ2propagate in the Fresnel region of a homogeneous medium, the spectral correlation function,

〈

A

(

x
′

,

y
′

;

λ
1

)

A
*

(

x
,
y
;

λ
2

)

〉

, gradually changes with increasing propagation distance. An exact expression is developed which describes these changes. The changes are exhibited in terms of both modulus and phase. In the special case where the two wavelengths are identical, the spectral correlation function reduces to the autocorrelation function. In this case, the function, as expected, is found to conserve during propagation. The paper considers two spectrally well-separated plane waves from the visible part of the spectrum at 450 and 650 nm. Numerical evaluations are given for a typical spectral correlation function that might arise from these waves in conditions of good seeing. It is shown that this spectral correlation function is capable of propagating with a high degree of conservation over distances of the order of the atmospheric depth. It is inferred from this that the spectral correlation function that arises when visible waves pass through the atmosphere is determined only by the accumulated effect of the local atmospheric turbulence; the propagation distance itself makes no significant contribution to the final value attained by the function. This result simplifies the task of describing the statistical properties of polychromatic images formed by large astronomical telescopes. It also offers insights and tools for dealing with the problems associated with laser beam propagation through the atmosphere.
Lightness contrast and lightness constancy
Authors: Sewall Laura , Wooten Bill R.
Published: February 2023

Previous studies of lightness contrast and constancy have used matching procedures to assess perceptual effects. Many experiments indicate that constant luminance ratios give constant lightness matches, suggesting lightness contrast as an explanation of lightness constancy. Other studies fail to support this conclusion. We felt that the contradictory results might be due to the difficulty of making lightness matches in the face of large brightness differences. Thus we had observers make absolute lightness judgments of center-surround targets over a large range of contrast ratios and luminance. We first used brief (300-ms) flashes to keep the eye in a fixed state of light adaptation. The results surprised us. We found that lightness constancy failed for every subject: generally low and high luminances were judged to be blacker than middle luminances for a wide range of contrast ratios. When longer (7-s) flashes were used, however, we obtained good constancy. We then tried brief flashes following light-adapting fields to ascertain if the constancy found for longer flashes could be attributed to adaptation. The results were negative. Our tentative conclusion is that constancy fails for brief flashes due to their transient nature, not to the lack of adaptation. Apparently, sustained viewing is necessary for lightness constancy.
Effect of background orientation on simultaneous contrast
Authors: Polichar Valerie E. , MacLeod Donald I. A.
Published: February 2023

The effect of background orientation, as well as stimulus alignment, background spatial frequency, and background contrast on simultaneous contrast effects, was observed in achromatic displays of plus-sign-shaped test stimuli against square-wave gratings. Results indicated that the axis along which lightness information most influences contrast induction varies depending on background orientation and spatial frequency. When background spatial frequency was higher than that of the test pattern, contrast induction was influenced most by neighboring elements on the axis perpendicular to the background orientation. When spatial frequency was equivalent to that of the test stimulus and test stimulus arms were aligned with similar-luminance background stripes, induction was influenced more by information along the same axis as the background orientation. When test stimulus arms were aligned with most-dissimilar background stripes, judgments were again most influenced along the axis perpendicular to the background orientation. Bias of judgment in each direction increased as the background contrast approached that of the test stimulus arms. Traditional explanations of simultaneous contrast based on lateral inhibition at the retina are found to be incomplete. Accounts for the observed effects based on local surrounding luminance and on the nature of orientation-specific cell connections are outlined.
Additivity of induced blackness
Authors: Volbrecht Vicki J. , Werner John S.
Published: February 2023

The additivity of induced blackness was tested in conditions of temporal contrast. Two adult observers foveally viewed an inducing field composed of either one of seven variable wavelengths (430-670 nm, 40-nm steps), one of two addend wavelengths (510 and 630 nm), or a combination of one variable wavelength and one addend wavelength for 5 s followed immediately by a broadband (5500-K) reference stimulus of the same size (0.75°) and spatial location as the inducing field. The observers increased the radiance of the inducing field until the reference stimulus appeared completely black. Additivity tests were also obtained with the same wavelength combinations for each observer using heterochromatic flicker photometry (HFP) and direct brightness matching. The additivity results from blackness induction resembled those from HFP, whereas the results from brightness matching showed clear additivity failures of the cancellation type. These findings were also corroborated by additivity tests performed on spatially induced blackness. These data indicate that the perception of blackness is mediated by neural mechanisms that additively combine the input of middle- and long-wave photoreceptors.
Reflectance ensembles with illuminant-Invariant chromaticity ordering
Authors: Brill Michael H.
Published: February 2023

In a color atlas, the uniformity of color spacing between reflectances is disturbed by changes in the spectral power distribution (SPD) of the illumination. Because the atlas may still be useful under different lights, we introduce a new metric of color order that is less sensitive to change of illumination. Three reflectances with labels 1, 2, 3 map to points in chromaticity space (under a particular light) that, if not collinear, are ordered either clockwise or counterclockwise. The ordering parameter P of the reflectances is –1 for clockwise ordering, +1 for counterclockwise ordering, and 0 for collinear points. The perceptual significance of P can be tested via a dichotomous color-blindness test (such as the Farnsworth D-15 test). It has been shown mathematically1 that the P of three reflectances depends on illumination only if, when the reflectances are treated formally as color-matching functions, the chromaticity space that results has a spectrum locus that is not everywhere convex. Illuminants affect P when one or more reflectances is purple—a vindication of the model because purples are known not to be color-constant. A color atlas is called statistically consistent if its first three principal components form a chromaticity space that is convex and well ordered in wavelength. The Munsell atlas is statistically consistent. Convexity of the spectrum locus also insures that no linear combination of the reflectances (or reflectance principal components) has more than two zero crossings. Implications of these theorems for color technology and robotic vision are noted.
High-order optical nonlinearities in semiconductors
Authors: Canto E. , Young J. , Miesak E. , Van Stryland Eric W. , Soileau M. J. , Hagan David J.
Published: February 2023

A rigorous study of degenerate four-wave mixing in two- and three-photon absorbing semiconductors with picosecond pulses has been performed. In the two-photon absorbing regions, we found two different nonlinearities to be present. The first is due to excitation of a free-carrier grating by two-photon absorption which scatters a third beam to produce a phase conjugate. Thus this is a sequential

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process which appears as a fifth-order nonlinearity. The second nonlinearity is found to be fast, independent of grating period, and described by a third-order susceptibility which in ZnSe at 532 nm is 2 orders of magnitude greater than that of CS2. These results were replicated at 1.06μm in CdTe and thus seem to be generally applicable to two-photon absorbing semiconductors. Polarization selection has shown that this nonlinearity is of the grating type. Despite the two-photon resonance, the two-photon coherence term was found to be absent. This behavior was found to be replicated in ZnSe at 1.06μm, now in the three-photon absorption regime. Here a fast χ(5)process is accompanied by a slow χ(7)process [explained by sequential three-photon absorption followed by linear refraction

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. The fast nonlinearities seem to be intimately linked to the two- and three-photon absorption. By variation of pump-probe angles and input irradiances, the density dependence of the effective diffusion coefficient has also been determined.