bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of Optical Distances Using Coherent Multi-Mode Laser Light
Authors: Ichimura Tsutomu , Andou Naoki , Odagiri Yoshiki , Funaba Tadayuki , Tan-no Naohiro
Published: February 2023

A novel technique based on an optical multi-mode frequency domain reflectometer, is used for measuring the optical distances. The proposed system comprises of a free-running multi-mode laser diode, an optical spectrometer and a computing system. The proposed highly sensitive reflectometer is capable of measuring distances with high resolution and does not contain moving parts as in low coherence interferometry based on the Michclson's interferometer.
Microscopy through Scattering Media
Authors: Kempe M. , Thon A. , Rudolph W.
Published: February 2023

The combination of confocal microscopy and coherent broad-band illumination is shown to enable imaging with micrometer resolution through scattering media with potential applications in biology and medicine. A linear and a nonlinear correlation technique based on the detection of interference and second harmonic generation, respectively, which provide a time gate and a k-space filter are discussed. Experimental and theoretical investigations are presented describing fundamental limits of this imaging technique.
Locating Objects with Diffuse Light
Authors: den Outer P. N. , van Rossum M. C. W. , Nieuwenhuizen Th. M. , Lagendijk Ad
Published: February 2023

A small object hidden in a multiple scattering medium is accurately located using a continuous light source. Good agreement between theory and experiment is found.
Efficient Numerical Method for Quantifying Photon Distributions in the Interior of Thick Scattering Media
Authors: Koo P. C. , Schlereth F. H. , Barbour R. L. , Graber H. L.
Published: February 2023

In this report we present preliminary results towards developing an efficient numerical scheme for computing photon migration in complex scattering media such as body tissues. Our motivation for these studies is the appreciation that development of practical imaging schemes will require that solutions to the forward problem be computationally tractable, physically accurate and have a format that maps well to the inverse problem. The object here is to optimize the tradeoffs and still obtain an acceptable answer. It is known, for example, that Monte Carlo methods can provide accurate estimates of photon distributions, even for complex media, but the computing times can be unacceptable long. Numerical solutions to the diffusion are computationally much more efficient, but of course, the physically accuracy of these solutions are subject to the constraints of the diffusion approximation (i.e., away from boundaries and source and the absence of strong discontinuities). We further recognize that for iterative inversion methods, solution of the forward problem on a uniform grid is desirable, as it permits use of global instead of local interpolation functions. Solutions to the forward problem that employ nonuniform grids certainly can be considered, but add to computing times for the inverse problem.
Image Reconstruction of Targets in Random Media from Continuous Wave Laser Measurements and Simulated Data
Authors: Chang J. , Graber H. L. , Barbour R. L. , Chang J. , Barbour R. L , Graber H. L. , Barbour R. L.
Published: February 2023

Four algorithms - POCS, CGD, SART and a SART-type method with regularization, were used to reconstruct images of targets in dense scattering media. The convergence rates and image quality are evaluated.
Time Gated Imaging Through Scattering Materials with Nonlinear Optical Raman Interactions
Authors: Reintjes J. , Duncan M. D. , Bashkansky M. , Moon J. A. , Mahon R. , Tankersley L. L. , Prewitt J. M. S.
Published: February 2023

We have developed several time-gated imaging techniques that allow the viewing of objects through dense scattering material. These techniques are based on nonlinear optical Raman interactions and include pulse gating using stimulated Raman amplification and correlation gating using both coherent anti-Stokes Raman scattering and stimulated Raman scattering. In the ballistic imaging regime, images with resolution better than 125 μm have been obtained after scattering attenuations of up to e−33. We have performed theoretical studies to determine image resolution in the diffuse and quasi-diffuse scattering regimes. In the fully diffuse regime the spatial resolution is found to be approximately one-fifth of the length of the scatterer. We have verified this result experimentally. We have also used the above techniques to perform range-gated imaging of objects embedded in scattering and non-scattering material.
Destruction of Optical Coherent Backscattering by Magnetic Faraday Rotation
Authors: Lenke Ralf , Maret Georg
Published: February 2023

Measurements of optical coherent backscattering cones from magneto-optically active multiple scattering media in magnetic fields up to 23 T are reported. The observed field induced lowering of the backscattering enhancement and change of the cone shape compare well with a realistic simple model.
Propagation of Coherent Radiation in Disordered Media: Mesoscopic Effects
Authors: Kaveh Moshe
Published: February 2023

Important mesoscopic phenomena accompanying the propagation of classical waves in a random medium are considered. The long range spatial and spectral correlations are analyzed and it is shown that the presence of absorption modifies qualitatively the spectral correlation function. The influence of mesoscopic fluctuations on the intensity distribution function is considered. It is shown that only for small values of intensity is the distribution function a simple exponent, as predicted by Rayleigh statistics. For larger values of intensity, the distribution function differs drastically from a simple exponential and the asymptotic behavior is a stretched exponential. Also considered is the slowing down of the diffusion in the medium with resonance scatterers.
Speckle Spectroscopy under Atmospheric Turbulence
Authors: Baba Naoshi , Kuwamura Susumu , Miura Noriaki , Norimoto Yuji
Published: February 2023

A method for speckle spectroscopy under atmospheric turbulence is described. A stellar speckle image and its dispersed speckle image are observed simultaneously. An object is reconstructed from speckle images, and its spectrum is reconstructed from dispersed speckle images referring to their speckle images. The shift-and-add reconstruction method is discussed in comparison with ballistic light imaging. Several observational results show that stellar spectroscopy with high-spatial resolution is feasible even under atmospheric turbulence.
Optical Coherence Tomography and Microscopy in Gastrointestinal Tissues
Authors: Izatt Joseph A. , Wang Hsing-Wen , Kulkami Manish , Kobayashi Kenji , Canto Marcia I. , Sivak Michael V.
Published: February 2023

Novel technology and preliminary results are presented for micron-resolution noninvasive sub-surface optical tomographic imaging in gastrointestinal tissues with potential applications in diagnostic endoscopy.
Laser Computed Tomographic Images of Bones and Teeth by Coherent Detection Imaging in the Visible and Near-IR Regions
Authors: Devaraj B. , Fukuchi K. , Watanabe Y. , Ishihata H. , Kobayashi M. , Yuasa T. , Endo H. , Takeda M. , Usa M. , Horiuchi H. , Akatsuka T. , Inaba H.
Published: February 2023

The coherent detection imaging method that is based on the optical heterodyne detection technique is used to obtain laser computed tomographic images of animal bones and human teeth in the visible and near-IR regions. The image contrast is shown to be wavelength dependent. Laser tomographic images of a tooth pathological condition also confirms a wavelength dependent difference in structure and contrast. Use of green light along with red or near-IR light is suggested as a potential for hard tissues imaging in vivo.
High Speed Optical Coherence Tomography
Authors: Tearney G. J. , Bouma B. E. , Boppart S. A. , Golubovic B. , Swanson E. A. , Fujimoto J. G.
Published: February 2023

We present an Optical Coherence Tomography system capable of high speed imaging using a piezoelectric optical fiber stretcher to produce the reference arm optical delay and a KLM Cr: Forsterite 1300 nm solid state laser as the optical source. The OCT system produces 3 × 2.2 mm images at four frames per second with an axial resolution of 15 µm and a signal to noise ratio of 112 dB.
Optical Heterodyne Imaging Through Turbid Media at 1.3 µm Wavelength
Authors: Wang Xiaomei , Rediker Robert H.
Published: February 2023

Using a frequency-shifted CW optical homodyne technique with a 1.3 µm diode laser source, we have imaged through 50 mm thick 0.33% intralipid solutions with millimeter resolution. These results, achieved with a useful single-mode power of 0.5 mW, can be further improved by using higher power and enhanced detection sensitivity. The projected capabilities of this technique show promising potential for high-resolution, subsurface optical imaging for medical applications.
Practical Limits for the Detection and Characterization of Optical Inhomogeneities using Diffuse Photon Density Waves
Authors: Boas D. A. , O’Leary M. A. , Chance B. , Yodh A. G.
Published: February 2023

Diffusing photons can provide information about the spatially dependent optical properties of turbid media. In biological tissues these optical properties may be correlated to physiological parameters, enabling one to effectively probe the physiological states of tissue for abnormalities such as tumors and hemorrhages. In this paper, we show that positional uncertainty in the source and detector lead to significant random errors which degrade the optical information available from diffusing photons. We investigate the limits for the detection, localization, and characterization of optical inhomogeneities using diffusing photons as a probe. While detection is sufficient for tumor screening, full characterization of the optical properties is desirable for specification of the tumor. Our findings in model breast systems with realistic signal-to-noise indicate tumors as small as 0.3 cm in diameter can be unambiguously detected and located; however the size and optical properties of the tumor can only be simultaneously determined if the diameter is of the order of 1.0 cm. On the other hand if a priori information is available then the optical properties (size) of tumors as small as 0.3 cm in diameter can be determined.
Frequency-Domain Optical Image Reconstruction: Initial Experimental Studies on Contrast and Resolution Limits
Authors: Jiang Huabei , Paulsen Keith D. , Österberg Ulf L.
Published: February 2023

Recent progress in near infrared frequency-domain optical image reconstruction based on laboratory data is reported. Particular attention is given to the important issues of imaging contrast and resolution.
Imaging on Brain Model by a Novel Optical Probe - Fiber Hairbrush
Authors: Luo Qingming , Nioka Shoko , Chance Britton
Published: February 2023

The continuous light method like RunMan hemoglobinometer was successfully used to record hemoglobin desaturation of the brain in comatose patients and the detection of brain bleeds. In this paper, a new optical probe for brain oxygenation detection-fiber hairbrush is presented. This novel probe can replace the usual RunMan probe and make the RunMan device more flexible when measuring the brain deoxygenation and desaturation. To seek the possibility of functional imaging on human brain by the hairbrush, several tests have been taken. It is shown that (1) fiber hairbrush can detect the same signal through the hair as the usual RunMan probe do from the direct contact measurement. (2) Object hidden in the brain model can be detected and imaged by the hairbrush. (3) Oxygenation changes of the human brain due to motor activity can be indicated. Further experimental results on human brain activity by a computer controlled continuous wave optical imaging probe were presented. The functional image from the imaging probe can localize the relative concentration in Oxy-Hb changes of brain which corresponds anatomically to the motor cortex.
Influence of Clear Cerebrospinal Fluid on NIR Brain Imaging and Cerebral Oxygenation Monitoring
Authors: Liu Hanli , Boas David A. , Yodh Arjun G. , Chance Britton
Published: February 2023

Experimentally and theoretically we show significant influence of clear cerebrospinal fluid on NIR brain scattering determination but small influence on brain oxygenation imaging and monitoring.
Angular Dependence of The Intensity Temporal Profiles of Scattered Pulses in Diffusive Regime
Authors: Zevallos M. E. , Liu F. , Das B. B. , Polishchuck A. Ya. , Alfano R. R.
Published: February 2023

In this paper, the angular dependence of intensity temporal profiles for three sample media of different scatterer size are described. Detection angles around a fixed point are varied. Similar detection points in each media have been chosen along two directions: forward - along the light source launching direction, x-axis; and lateral or perpendicular direction, y-axis, for comparison. Measurements show the existence of a strong angular dependence of light traveling in a highly scattering media even for distances as large as 20 transport mean free path. More light is observed in the forward direction than in the lateral direction. The strong angular and spatial dependence indicates the existence of an anisotropic behavior of photons from the source directionality. To describe the high degree of anisotropy of photon migration in the medium, two new anisotropy parameters are introduced.
Laser Doppler measurements and Monte Carlo simulations for determination of the scattering properties of fluids including blood
Authors: Kienle Alwin , Patterson Michael S. , Ott Lutz , Steiner Rudolf
Published: February 2023

In this study we describe laser Doppler measurements on scattering liquids flowing through a highly scattering static medium to determine the scattering coefficient and the anisotropy factor of the liquids. Monte Carlo simulations of light propagation in the static and moving media were used to calculate the Doppler spectra. We show that the scattering coefficient of liquids can be derived from the integration of the Doppler spectrum provided that the absorption coefficient of the liquid is much smaller than the scattering coefficient. The anisotropy factor was deduced by applying an iterative nonlinear regression method to fit the measured Doppler spectra. The experimental setup was tested by comparing laser Doppler measurements on polystyrene spheres with Monte Carlo simulations. Finally, the scattering properties of dilute Intralipid20% and those of blood were determined at λ = 820 nm.
Sensitivity of Boundary Walls in Photon Migration and Optical Imaging
Authors: Das B. B. , Liu Feng , Alfano R. R.
Published: February 2023

Time-resolved light scattering measurements around a cell containing intrahpid suspension were performed with transparent, absorbing, reflecting and water boundaries. In case of the reflecting boundary walls the collection of early light as well as diffuse signal was highly enhanced. When an absorber was introduced into the scattering medium the relative change in intensity profiles was found to be maximum for the reflecting walls suggesting that such a choice of boundary may be used to improve time-resolved shadowgrams as well inverse image reconstruction.
Depolarization behavior of multiple scattered light from an optically dense random medium
Authors: Brosseau C. , Bicout D. , Martinez A. S. , Schmitt J. M.
Published: February 2023

We study numerically, using the Mie theory, light transmission through a multiply scattering medium composed of a collection of uncorrelated, optically inactive spherical particles. The characteristic length over which a plane wave field is depolarized depends on whether it is initially linearly or circularly polarized and of the size of the particles. In a medium containing particles small compared to the wavelength (Rayleigh regime), the characteristic length of depolarization for incident linearly polarized light is found to exceed that for incident circularly polarized light, while the opposite is true in a medium composed of particles large compared to the wavelength (Mie regime). Comparison of numerical results with data from measurements on suspensions of polystyrene latex spheres in water is made. Agreement between these simulations and experiment is good for the range of sizes considered in this paper. We also discuss the relevance of the helicity flip model to the analysis of these data.
Time Resolved Diffusion Tomographic Image Reconstruction in Highly Scattering Turbid Media
Authors: Cai W. , Das B. B. , Liu F. , Zevallos M. , Lax M. , Alfano R. R.
Published: February 2023

Image of objects hidden in highly scattering media was reconstructed using a new fast and noise-resistant algorithm applied to the optical diffusion tomography. Temporal intensities slices at multiple times of scattered profiles from multiple source-detector pairs are used as experimental input data to form an image.
Optical BackProjection Tomography in Heterogeneous Diffusive Media
Authors: Colak S.B. , Schomberg H. , Hooft G.W.’t , van der Mark M.B.
Published: February 2023

A modified backprojection image reconstruction method including corrections for blurring and refraction is described for medical optical tomography. This method is illustrated using cylindrical phantoms containing simple objects.
Reconstructing absorber images in a three-dimensional scattering medium by using photon-path data
Authors: Maki Atsushi , Koizumi Hideaki
Published: February 2023

The proposed averaged photon-path imaging (APPI) method uses Monte Carlo data to reconstruct the images being scanned by optical tomography. To confirm its effectiveness, simulated continuous-wave measurements of one or two absorbers located in a cubic scattering medium were performed. The three-dimensional locations of the absorbers were accurately reconstructed using the APPI method. Combining time-resolved measurement with the APPI method improved the accuracy of the reconstructed images. The APPI method can thus be applied to various measuring situation for practical image reconstruction.
Tomographic Detection of Fluorophores Embedded in Tissue-Like Phantom
Authors: Wu Jun , Perelman Lev , Dasari Ramachandra R. , Feld Michael S.
Published: February 2023

We present a prototype tomographic system and a simple inverse algorithm to detect fluorescent objects embedded in thick tissue-like phantoms using early arriving fluorescence photons.
Recent Results of Visible Laser Guide Star Tests Using a 500-Channel Adaptive Optics System
Authors: Sandler D. G. , Arnold R. , Cuellar L. , Lefebvre M. , Barrett T. K. , Rego A. , Smith G. , Trissel R. , Fairchild P.
Published: February 2023

We have recently finished development of an adaptive optics system intended to be a versatile instrument for imaging and beamforming from visible to infrared wavelengths. In particular, it can be used to perform broadband imaging using a visible laser guide star for astronomical applications. For the purpose of testing, the system is currently integrated with a 1-meter telescope in San Diego. However, the adaptive optics hardware is designed to operate under atmospheric conditions up to D/r0=30, making the system suitable for correcting a 3-meter telescope at visible wavelengths (assuming 1 arcsec seeing) or a 6-meter class telescope in the infrared. We point out, however, that the probe lasers we are using for our tests would have to be upgraded for large aperture correction.
Resolution Limits for Ground-based Astronomical Imaging
Authors: Olivier Scot S.
Published: February 2023

The resolution of ground based astronomical images is limited by atmospheric turbulence to angular sizes that are much larger than the theoretical diffraction limit of large telescopes. Adaptive optics systems offer the possibility of correcting the turbulence induced image degradation and producing near diffraction limited images; however, in general, the achievable long-exposure resolution will be somewhere between the atmospheric seeing and the telescope diffraction limit.
Evaluation of a Concept for Widening the Useful Field-of-View of an Adaptive Optics System
Authors: Fried David L.
Published: February 2023

It is well known the useful field-of-view of an adaptive optics system is quite small. For astronomical observation in the visible the size of the isoplanatic patch, θ0, is of the order of 10 μrad. After adaptive optics compensation of turbulence induced wavefront distortion, the mean-square residual wavefront distortion for the imaging of a point source that is an angular distance θ from the direction to the adaptive optics beacon, will have a value of (θ/θ0)5/3 rad2. This suggests that the useful field-of-view is limited by anisoplanatism to a diameter of about 2θ0.
Atmospheric Characterization for the Air Force-Maui 4 m Telescope
Authors: Walters D. L. , Gast V. J. , Mattingly T. S. , Galarowicz D.
Published: February 2023

The 1.6 and 1.2 m telescopes used by the US Air Force on Mt. Haleakala have averaged 7-9 cm atmospheric coherence lengths with occasional peaks of 15 to 20 cm over the last two decades. In comparison, the 4 m California, France, Hawaii, Telescope on Mauna Kea has improved from 4 cm to 15 cm average coherence length over the last decade. The source of the optical degradation found on Mt. Haleakala was not clear. Since a 4 m telescope was being considered for Maui, it was essential to determine the source of the turbulent degradation.
Sensing horizontal wind and refractive-turbulence profiles ( C n 2 ) using wave front slope measurements from two reference sources
Authors: Welsh Byron , Koeffler Steven
Published: February 2023

In the theory of atmospheric turbulence, the strength of the spatial variations of the index of refraction n is characterized by the power spectral density (psd)

Φ
n

(

K
→

)

where

K
→

is the wavenumber vector. The magnitude of

Φ
n

(

K
→

)

is proportional to a parameter known as the atmospheric structure constant of the refractive index fluctuations. The atmospheric structure constant is denoted

C
n
2

and is a function of position along the optical path. In addition to spatial variations, n is also characterized by temporal variations. The strength of these temporal variations is directly related to the transverse velocity of the turbulence along the optical path, v.
Mirror and dome seeing measurements at AMOS
Authors: Oldenettel Jerry R.
Published: February 2023

While the effect of mirror and dome temperatures on seeing quality has been the subject of several recent laboratory experiments (1,2,3), no data from working telescope systems has been published. In this paper, I present data collected on telescopes of two different designs located at the Maui Space Surveillance Site located near the 10,000 foot summit of Haleakala Volcano on Maui, HI. The 1.6 meter aperture AMOS telescope is a closed tube Cassegrain design which tends to trap mirror generated turbulence and channel it along the telescope line of site. The 1.2 meter aperture MOTIF telescope is an open truss Cassegrain design with a short tube which extends about 1 meter above the mirror. The telescopes are housed in separate 15 meter domes located about 50 meters apart.
Atmospheric Pathlength Fluctuations in the Infrared Spatial Interferometer
Authors: Bester M. , Danchi W. C. , Degiacomi C. G. , Greenhill L. J. , Townes C. H.
Published: February 2023

Generally, turbulence in the atmosphere has been described by a Kolmogorov-Taylor (K-T) model. In some cases deviations from this simple theoretical model have been found. Measurements of phase fluctuations in light paths through the atmosphere presented here indicate that under typical astronomical observing conditions these deviations can be significant. This result is particularly important for prediction of the performance of large filled-aperture telescopes or long-baseline interferometers at infrared wavelengths. Analysis of the statistics of these pathlength fluctuations shows that they often appear to follow a non-Gaussian distribution.
Mirror, dome, and local seeing effects at the CFHT
Authors: Salmon Derrick
Published: February 2023

The study of causes of image quality degradation at the CFHT and related solutions have lead to a reduction of the median observed image size from 2.5 arcseconds to 0.7 arcseconds.
The UH prototype adaptive optics system.
Authors: Graves J.E. , McKenna D.L. , Northcott M.J. , Roddier F.
Published: February 2023

A prototype adaptive optics (AO) system optimized for astronomical applications is currently being built at the University of Hawaii. The system will use natural stars in the vicinity of the object of interest to sense the wavefront. Owing to the extreme sensitivity of the wavefront sensor, it will be possible to observe improved images over most of the sky. Fig. 1 shows the expected reference star limiting magnitude and the compensated field-of-view for a 2, 5, and 9 Zernike conpensation (+) on a 3.6-m telescope. The contour plot shows the percentage of sky coverage at 90° of Galactic latitude. The dotted contour is the 50% coverage at the Galactic pole. Fig. 1 shows that tip-tilt compensation (2 Zernike terms) will be achieved over the whole sky, as already demonstrated by HR Cam at the CFH telescope. A 5-Zernike compensation, equivalent to that of most current systems, will be achieved over 30% of the sky. In addition a 9-Zernike compensation, will be possible over 10% of the sky.
Wavefront Sensing for Solar Imaging
Authors: Radick Richard R. , Restaino Sergio R. , Conan Jean-Marc
Published: February 2023

The Sun presents unusual problems for wavefront sensing. Unlike the nighttime sky, the Sun does not provide natural, high-contrast point sources, and creation of artificial beacons bright enough to be visible against the solar disk remains problematic with current technology. Small sunspots and pores can provide satisfactory substitutes for point sources, but these are available for only a tiny fraction of the solar disk. To measure wavefronts at arbitrary locations on the Sun, we must develop wavefront sensors capable of using the ubiquitous solar granulation as a target. Solar granulation is extended (its characteristic angular scale is about one arcsecond), unbounded (the angular extent of the composite pattern greatly exceeds the isoplanatic angle), low contrast (a few percent), and both spatially and temporally variable (the typical evolution time scale is minutes). A wavefront sensor must successfully contend with all these characteristics of solar granulation to be well-suited for general solar imaging.
Atmospheric wavefront measurements and evaluation of adaptive optics efficiency
Authors: Madec P.Y. , Rousset G. , Séchaud M.
Published: February 2023

Wavefront measurements have been made with the COME-ON adaptive optics prototype system on the ESO 3.6 m telescope at La Silla (Chile). Two types of data have been recorded : the atmospheric wavefronts and the residual wavefront errors after correction by the adaptive optics system.

A spatial and temporal characterization is performed through both angle-of-arrival fluctuation analysis and wavefront modal expansion. Correlation times and atmospheric cut-off frequencies are deduced for different seeing conditions. The outer scale of the turbulence is also determined.

The servoloop transfer function is analysed. The adaptive optics gain is expressed in terms of wavefront fluctuation attenuation. Different types of servoloop control are compared. During these experiments, the maximum servoloop bandwidth has reached 25 Hz for a 100 Hz sampling frequency.
"Wavefront Control of a Wide Field of View System Using Adaptive Optics"
Authors: Shen Gon-Yen , Kaplan Leonard
Published: February 2023

There are a number of unique technical challenges in applying adaptive optical wavefront control in wide field of view systems. Aside from the fact that the wavefront characteristics can vary from field to field, the pupil mapping between the aperture of the telescope and the corrective element (deformable mirror) also distorts, causing varying influence functions over the field of the view. In addition, the technique for sampling the outgoing wavefront using holographic gratings is significantly complicated because of the large field. In the past few years, techniques to address these issues have been developed and successfully implemented through a hardware experiment, Integrated Beam Control Demonstration (IBCD), at Hughes Danbury Optical Systems, Inc.
Towards Lower Cost Adaptive Optics Systems
Authors: Roddier François
Published: February 2023

An adaptive optics system consists of a wavefront sensor, a wavefront compensator and a control computer. The wavefront sensor produces M wavefront measurements which are given as input signals to a control computer. The computer delivers P output voltage values to be applied to the wavefront compensator. Wavefront compensators generally consist of a deformable mirror with P actuators. Usually the figure of the deformable mirror at rest is not perfect but corrects itself in a closed loop. In order to do that the number M of wavefront measurements has to be higher or equal to the number P of actuators.
First-order performance evaluation of adaptive optics systems for turbulence compensation in extended field-of-view astronomical telescopes
Authors: Ellerbroek Brent L.
Published: February 2023

A general approach is presented for evaluating and optimizing the degree of atmospheric turbulence compensation achieved by an adaptive optics system employed as part of a extended field-of-view astronomical telescope. This method applies to an adaptive optics system incorporating either one or multiple natural and/or laser guide stars sensed by wave-front slope sensors, a wave-front reconstruction algorithm equivalent to a matrix multiply, a servo control law to temporally filter the output of the wave-front reconstructor, and one or several deformable mirrors optically conjugate to different ranges along the telescope’s line-of-sight. The degree of atmospheric turbulence compensation achieved by such a configuration is evaluated in terms of the residual mean-square phase distortion and turbulence-induced optical transfer function at each point in the telescope’s field-of-view. This evaluation accounts for the combined, interacting effects of the atmospheric turbulence

C
n
2

(
h
)

profile and wind velocity profile, wave-front sensor and deformable mirror fitting error, wave-front sensor noise, finite control system bandwidth, and the net anisoplanatism associated with a given constellation of natural and/or laser guide stars. Optimal wave-front reconstruction algorithms are derived which minimize the telescope’s field-of-view-averaged residual mean-square phase distortion. These evaluation and optimization results are first-order in the sense that they neglect diffraction effects and assume that all adaptive optics components are strictly linear. Results for the case of a finite servo bandwidth also require the wave-front reconstruction algorithm coefficients to satisfy a set of linear constraints; the reconstructor must precisely predict the deformable mirror actuator command vector in the absense of sensor noise and atmospheric turbulence. Numerical results are presented for a variety of adaptive optics configurations incorporating either a single guide star, multiple guide stars and a single deformable mirror, or multiple guide stars and two deformable mirrors.
Characteristics of Ground-Based Adaptive Telescope
Authors: Lukin Vladimir , Fortes Boris
Published: February 2023

It is known that atmospheric turbulence limits an angular resolution of ground-based astronomical imaging systems of the order of λ/ro in size, where ro is the coherent radius of the wavefront distorted by the atmosphere, typically values for visible spectral range Cλ= 0.55μm) under the good seeing conditions vary in 20 to 40 cm. Many designs of the ground-based telescopes provide using the system for adaptive (or active) correction of distortions of radiation wavefront of object observed. Here the need for modeling the operation of such systems arises.
Stellar Phase Shifting Interferometer
Authors: Colucci D. , Angel R.
Published: February 2023

Wavefront measuring systems currently in use in adaptive optics (AO) indirectly measure wavefront distortions. The wavefront is then reconstructed using various estimation methods. The advantages of these wavefront sensors are light efficiency and speed, however systematic errors and error propagation pose real concerns over their performance on large aperture telescopes. A new instrument which uses phase shifting interferometry on a bright star to directly map the wavefront phase errors in the pupil plane is intended not as a system component but as a calibration tool for the more efficient wavefront sensors actually used in AO systems.
SPICE-100: A Turn-key Adaptive Optics System for Ground-Based Imaging
Authors: Stopher Ronald W. , Wormell Dean
Published: February 2023

The SPICE-100 (Special Purpose Image Compensation Equipment) system offers unique wavefront sensing and correction capabilities for compensation of optical aberrations due to atmospheric turbulence, manufacturing errors, environmental effects, and misalignments. The SPICE-100 adaptive optics system combines state-of-the-art components and processing technologies providing a complete turn-key operation. Substantial performance improvements are achievable for direct imaging, spectroscopy, and interferometry applications by minimizing or eliminating optical aberrations.
Large Active Mirror in Aluminium (LAMA) A status report
Authors: Leblanc Jean-Marc , Lhenry Bernard , Séchaud Marc , Madec Pierre-Yves , Michau Vincent
Published: February 2023

Large mirrors in aluminium clearly appear as an alternative to conventionnal glass mirror in terms of shorter manufacturing time, reduced brittleness and lower cost. Such mirrors require active support allowing diffraction limited imaging. They are well suited for both ground-based and spaceborne large telescopes.

The purpose of this paper is to present the status of the LAMA project and to emphasize the recent progress in manufacturing process of the aluminium blank, in coating and polishing, and in active control strategy.
Recent results of the UH adaptive optics system.
Authors: Graves J.E. , McKenna D.L. , Northcott M.J. , Roddier F.
Published: February 2023

The adaptive optics system currently developed at the University of Hawaii, has already been described in this meeting. The deformable mirror, a piezo bimorph, is controlled by a wavefront curvature sensor. The sensor signals are modulated at a 7 kHz rate. Analog electronics is used to demodulate the sensor signals and provide tip/tilt error signals. Higher order compensation is performed digitally through a PC-type computer. At the time of this writing only a sample mirror of low optical quality has been available. We describe here results obtained on tip/tilt compensation and preliminary results obtained with the sample mirror. We plan to present results obtained with a good quality mirror at the meeting.
Adaptive Optics System Approach For Astronomical Use
Authors: Grub R. , in den Bäumen J. Schulte
Published: February 2023

Future application of adaptive optics technologies in large optical systems for atmospheric compensation and short wavelength correction requires wavefront sensing and wavefront control systems with high density of channels. Therefore the design and development of modular structure and cost-effective components are of great interest.
Wide Field Integrated Beam Control Demonstration Status: (Advanced Beam Control System Program)
Authors: Kaplan Leonard , Shen Gon-Yen
Published: February 2023

An integrated beam control demonstration (IBCD) has been fabricated and tested under the direction of the Naval Surface Warfare Center for the Strategic Defense Initiative Organization. The IBCD demonstrates the key technologies required for implementing a three mirror, wide field of view (WFOV), Advanced Beam Control System for a space-based laser.

This paper describes an overview of the IBCD and reviews the development and test of the WFOV beam expander, outgoing wavefront sensor (OWS), deformable mirror, dynamic steering mirrors, wavefront control subsystem and high speed diagnostic interferometer. The results include photos of the IBCD and hardware assemblies and evaluation of wavefront control performance.
Recent test results of a deformable bimorph mirror
Authors: Jagourel Pascal , Graves J. E. , Northcott M. J.
Published: February 2023

A 13 electrodes bimorph mirror has been developped by Laserdot in cooperation with the university of Hawaii. Such a mirror is a very simple device2 roughly consisting in 2 PZT plates bonded together. We present in this summary the mirror as well as its main optical and mechanical characteristics.
Simulation of Multi-Boacon, Multi-Conjugate Adaptive Optics
Authors: Link D. J.
Published: February 2023

A time-domain, wave-optics simulation of astronomical adaptive-optics systems has been developed. The simulation includes digital controls for the deformable mirror and steering mirror; atmospheric turbulence phase screens; wind; slewing; multiple three-dimensional beacons at various ranges, wavelengths, and offset angles; shearing and Hartmann wavefront sensors; Gaussian and Wiener reconstructors; radiometrics; and one or two deformable mirrors imaged at different altitudes with various actuator influence functions. The simulation has been used to investigate actuator spacing and bandwidth requirements, beacon combination algorithms and multi-conjugate DM algorithms.
CFHT Adaptive Optics System study
Authors: Gaffard Jean-Paul , Jagourel Pascal , Arsenault Robin
Published: February 2023

The CFHT adaptive optics design study has been carried out. The main components are presented in this paper as well as the expected optical performances.
Optical measurements of the outer scale of the atmospheric turbulence
Authors: Lukin Vladimir P.
Published: February 2023

The light scattering on the turbulence inhomogeneities of the atmosphere is the one of the main mechanism of distortion of the received optical signal. The random space-time changes of the atmospheric refractive index lead to distortion of the optical beam structure, the fluctuations of the intensity and phase of the optical wave are manifested, in particular, in blurring, shivering and flickering of the source images, as well as in the turbulent extinction of the mean received power of the signal.
The Effect of Laser Temporal Coherence on Active Speckle Imaging
Authors: Sherman G. , Holmes R.
Published: February 2023

Speckle imaging denotes a class of high-resolution astronomical imaging techniques; this class includes speckle interferometry, Knox-Thompson imaging, and the bispectrum technique.1,2,3 These methods are typically used under conditions of natural illumination, in which the light emanating from the object is temporally incoherent in the sense that the spread of the wavelength of the radiated light is on the order the mean wavelength. On the other hand, these techniques may be applied to conditions in which the object is laser-illuminated. Laser radiation is characterized by its intense spectral brightness and directionality. The directionality of laser radiation is especially useful for illumination of distant objects for which the high resolution offered by speckle imaging is most needed. However, the spectral brightness of lasers, i.e., temporal coherence, may result in laser speckle. This laser speckle can interefere with the speckle imaging process. Laser speckle appears most prominently in the pupil plane of the telescope, unlike the atmospherically-induced speckle evident in the focal plane; this latter speckle is that for which the speckle imaging techniques are named. Atmospherically-induced speckle appears in the focal plane of the telescope, but nonetheless may be affected by laser speckle. Natural questions then arise as to whether the laser speckle causes degradation, and if so, what can be done to mitigate its effect.
One-Way Holographic Image Correction For Turbulent Boundary Layer Distortion
Authors: Guthals D. , Sox D. , Noblett P. , Mann E. , Ma S. , Hu P.
Published: February 2023

Laboratory test results of the All Optical Imaging Brassboard employing real-time holographic turbulence correction will be presented. Dynamic bandwidths greater than 10KHz have been achieved.
Diode-pumped, High-Power CW and Modelocked Nd:YLF Lasers
Authors: Snell Kevin J. , Lee Dicky , Wall Kevin F. , Moulton Peter F.
Published: February 2023

Using a side-pumped, Nd:YLF slab laser design, we have obtained a TEM00-mode output power > 25 W with > 43% optical efficiency. As an amplifier of a SESAM-mode-locked laser, the same design has allowed us to generate, with 4.5-ps pulses at a 100-MHz rate, > 15 W of average power.
1W continuous-wave laser generation and excited state absorption measurements in Cr2+:ZnSe
Authors: Podlipensky A.V. , Shcherbitsky V. G. , Kuleshov N. V. , Levchenko V. I. , Yakimovich V. N. , Diening A. , Mond M. , Kück S. , Huber G.
Published: February 2023

Cr2+-doped chalcogenide crystals were shown recently to be promising materials for highly efficient and broadly tunable mid-IR (2-3 μm) lasers [1]. Possible applications of these lasers include medicine, remote sensing and trace gas analysis. Pulsed [2], continuous wave (cw) [3, 4], gain-switched [5] and diode-side-pumped laser operation [6] has been demonstrated with Cr2+:ZnSe, which exhibit slope efficiency as high as 63% and tunability between 2138 nm and 2760 nm. However, one of the problems encountered with this kind of materials is their relatively high level of passive losses at the laser wavelength. Thus both detailed spectroscopic studies including ESA measurements and synthesis of materials by using various crystal-growth techniques are necessary to estimate the amount of intrinsic optical losses and reduce as much as possible what is due to extrinsic reasons such as unwanted impurities and lattice defects. In this paper we report for the first time to our knowledge on the results of ESA measurements in Cr2+:ZnSe as well as on the realization of 1W efficient cw laser with Cr2+:ZnSe crystals.
Interaction Between Saturation and Lightness of Pigmented Samples
Authors: de Mattiello M.L.F.
Published: February 2023

It is known that saturation and lightness are interdependent dimensions
of colored surfaces. In the present study we are attempting to
describe the interaction between those two variables in quantitative
terms. We have noticed before (1,2) that when comparing samples of the
same hue and colorimetric purity (Pc) but different reflectance (R),
the observers (Os) assigned different values of saturation whether the
hue were mixed with white or black. Also the discrimination of
chromatic lightness varied in a different manner for high levels of
reflectance as compared with lower levels. Our main concern in this
work is to examine more closely these effects by dividing each
chromatic continuum in two ranges of reflectance: one where samples
move from pigment to white (P+W) and the other, ranging from pigment
to black (P+B).
The Fry Uniform Chromaticity Scale Diagram
Authors: Fry Glenn A.
Published: February 2023

In 1945 I1 formulated a theory of the retinal mechanisms for generating signals in the optic nerve fibers that would provide a basis for my modulation theory of color vision. In the process I developed a uniform chromaticity scale diagram.
Color Approximation by Relative Groups
Authors: Albert-Vanel Michel
Published: February 2023

Basic principles : 1 - In order to capture color in everyday life, it is necessary to take into account everything that globelly falls within the observer's field of vision.
Color Space of Coloroid Color System
Authors: Nemcsios Antal
Published: February 2023

The Coloroid colour space has been developed relying on results of harmony threshold tests on over 70 thousand subjects. Comparison of the Coloroid colour atlas representing its colour space, and of the colour sortiment of the Munsell colour atlas points out theoretically describable differences between both colour spaces.
Facilitation of Red-Green Perception by Luminance Pedestals
Authors: Stromeyer C.F.
Published: February 2023

My colleagues (G.R. Cole, R.T. Eskew, Jr. and R.E. Kronauer) and I have been studying how luminance information may aid perception of red-green color changes. Related work has been done by Hilz et al, (1974), Boynton et al. (1977) and Nick and Larimer (1983).
Retinal Chromaticity Co-ordinates and Color Appearance
Authors: Eisner A. E.
Published: February 2023

Color appearance and color constancy depend upon the chromaticity co-ordinates of light falling on the retina, not on the cornea. Many factors can change retinal chromaticity co-ordinates of a given test patch, including viewing conditions, spatial frequency of the stimulus, pupil size, and aging of the lens and other eye pathology. The visibility of white or monochromatic stimuli has long been modeled by the modulation transfer function. Dupuy1 has described a model in which the retinal image is treated as a series of transformations of the physical image. The modulation transfer function of each ocular element is determined, then all elements are combined linearly. Similarly, a simple way to approximate the retinal chromaticity co-ordinates is to compute the contrast of the stimulus at each wavelength, with each factor contributing to a contrast reduction or filter, and with the contribution of factors combined linearly2. For stimuli in maximal (laboratory) viewing conditions, of a moderate range of wavelengths, less than 10 cpd, and viewed with a pupil 2 mm or smaller and a healthy eye, there is usually an insignificant amount of contrast reduction2,3 for an "average" observer. Often these conditions are not met; this paper adds to our previous work a description of the effects of variations in macular pigment and lens densities for observers using color monitors. Determining the change in retinal chromaticity co-ordinates is important for several reasons. First, given the wide range of intra-observer differences in ocular pigmentation and scatter, as well as refractive error, it should be determined whether a given stimulus has chromaticity co-ordinates similar enough across observers to ensure similar color appearance. Second, with the widespread use of color monitors and displays, it is important to know whether information intended to appear a given color will, in fact, appear as intended for all the likely combinations of spatial parameters and adjacent colors. Third, to understand the neural factors involved in color appearance and color contrast, the retinal stimulus must first be determined.
Seventy Percent Conversion Efficiency for Frequency-Doubling of a Diode-Pumped Continuous-Wave Single-Frequency Nd:YAG Laser
Authors: Gerstenberger D.C. , Olson T.E. , Tye G.E. , Wallace R.W.
Published: February 2023

The combination of diode-pumped cw single-frequency Nd:YAG lasers and monolithic resonant frequency-doublers has lead to highly efficient and compact 532nm sources [1,2]. Using a diode-pumped 700 mW Nd:YAG laser, we have generated 500 mW of 532nm second harmonic with a monolithic magnesium-oxide-doped lithium niobate frequency-doubler. This corresponds to a conversion efficiency from 1064nm to 532nm of 72% and a conversion efficiency from the 2 W of 808.5nm diode pump light to the green of 25%.
HeCd Lasers Present and Future
Authors: Dowley Mark W.
Published: February 2023

The helium cadmium (HeCd) laser is a gas laser in which the active species is ionized cadmium metal vapor in helium buffer gas. It is similar in some respects to the HeNe laser. Continuous wave emission occurs in the deep blue at 441.6nm and in the near uv at 325nm. Short wavelength output of high spectral purity and excellent mode quality makes the HeCd laser uniquely useful in many applications.
Optically Pumped Blue Lasing in ZnSe/ZnMgSSe Double Heterostructures
Authors: Okuyama H. , Hiei F. , Akimoto K.
Published: February 2023

Photopumped blue laser oscillation has been achieved at room temperature in a ZnSe/ZnMgSSe double heterostructure. ZnMgSSe is a promising material for the cladding layer of blue laser diodes.