bluuebunny/crossref_metadata_2025 huggingface dataset:
Detection and adaptation within a long-wavelength cone pathway
Authors: Finkelstein Marcia A.
Published: February 2023

Recently Finkelstein et al.1 proposed a model of sensitivity control within a long- wavelength-sensitive cone pathway. The model, illustrated in Fig. 1, includes two nonlinear sites. The first is located at the long- and middle-wavelength (L- and M-) cones. The second is a red/green opponent stage that receives antagonistic inputs from the L- and M-cone pathways.
New model for brightness perception
Authors: Nakano Yasuhisa
Published: February 2023

Brightness-luminance discrepancy is the well known issue in color vision. To overcome this discrepancy, several models of brightness perception are proposed1),2) based on color vision model. Common idea of these models is that the brightness-luminance discrepancy yield from contributions of red-green and yellow-blue color opponent channels to the brightness perception. Recently, however, Nakano, Ikeda and Kaiser (1988)3) proposed another type of model. They explained the brightness perception using L-M and M-L type opponent mechanisms in stead of luminance and color opponent channels. They also showed that individual difference of brightness matching was explained by adjusting opponency of these two types of opponent mechanisms. In this paper, I modified their model so that it could explain individual data of spectral luminous efficiency function obtained by heterochromatic brightness matching. The data of twelve subjects were used in this analysis. The new model explains brightness matching data of composite lights as well as spectral data.
Saturation and Color Constancy
Authors: Brown Richard O. , MacLeod Donald I. A.
Published: February 2023

Color constancy is the phenomenon in which the colors of surfaces remain approximately constant despite considerable variations in the physical signals reaching the eyes from those surfaces. The analysis of color constancy is commonly restricted to changes in the intensity and chromaticity of the illuminant. We have been exploring aspects of color constancy which occur in the absence of shifts in the mean intensity or chromaticity of the stimulus, but depend instead on changes in the variance of the tristimulus values of the set of visible surfaces. (In natural settings, such effects may be due either to desaturation by haze, or to changes in the bandwidth of the illuminant.) The effects we consider are inconsistent with most previously published theories of color constancy.
Adaptation and Color Discrimination
Authors: Krauskopf John
Published: February 2023

That adaptation state of the observer has an important influence on color discrimination was revealed in MacAdam’s classical experiments. MacAdam represented his results on the CIE diagram with equal discriminability ellipses. The ellipses, which showed how discrimination varied in different color directions when the observer is adapted at various points in color space, varied in a complex way.
Chromatic Discrimination and the Boynton-Kambe formulation
Authors: Smith Vivianne C. , Pokorny Joel
Published: February 2023

Boynton & Kambe (Boynton and Kambe 1980) measured chromatic discrimination along critical axes in color space. These axes were lines of constant L/L+M excitation and lines of constant S-cone excitation, which are respectively vertical and horizontal lines in the MacLeod- Boynton (MacLeod and Boynton 1979) chromaticity space. Discrimination along constant L/L+M lines depended on S-cone excitation and showed no effect of L/L+M excitation. Discrimination along constant S-cone excitation lines showed a minimum near the L/L+M chromaticity of 570nm and additionally showed a small effect of the level of SWS cone excitation.
Color Appearance and Color Reproduction for Mesopic Vision
Authors: Momma C. , Honma S. , Yaguchi H. , Haneishi H. , Miyake Y.
Published: February 2023

Color vision at an intermediate luminance or illuminance level between photopic and scotopic range is called mesopic vision. The color of objects in mesopic vision is differently perceived from that in photopic vision, because not only cones but also rods contribute to the visual response. In general, red becomes dimmer than blue with decreasing illuminance level, which is known as the Purkinje phenomenon. Although many studies concerning the brightness in mesopic vision have been reported, there are very few experimental data dealing with color appearance at the mesopic level.
How Much Information is Available at the Retinal Concerning Color Perception- Comparison of Psychophysical and Model-Generated Data
Authors: Siminoff Robert
Published: February 2023

A model of the human retina has been developed that incorporates human and other primate data. At the retinal level, C- and L-type cells are simulated. The simulated midget C-type cells can be considered the origin of information for the paracellular pathways, while the midget L-type cells are the origin of information for the inagnocellular pathway. The question is how much of color perception can be explained in terms of the parameters at the retinal level.
Dynamic Response of the Human Pupil to Monochromatic Flash Light in Dim-adapted Condition — A Preliminary Examination
Authors: Watanabe Takeru Ken
Published: February 2023

IT has been recognized that, in the scotopic range, the spectral sensitivity of static pupil size demonstrates a curve similar to the CIE scotopic efficiency curve, and as does the pupil's dynamic threshold (1-2). On the other hand, in eyes adapted to light, Bouma measured the spectral energy from 425 to 660 nm, that evoked a 4 to 5 mm pupil contraction, and depicted that pupillary spectral sensitivity is enhanced in the blue wavelength region with a peak at 490 nm, a result quite different from the CIE photopic visibility function (3). To determine whether a blue-cone mediated contribution in the pupillary light reflex pathway is more dominant than in the luminance channel to the visual cortex, it will be of importance to re-investigate the static and dynamic pupillary behaviors in photopic, mesopic, and scotopic ranges.
Measurements of afterimages and minimum grating
Authors: Martinez-Uriegas Eugenio
Published: February 2023

Zone theories of the Muller type are major frameworks for psychophysical data on color vision. According to quantitative opponent-color models derived from zone theories, three degrees of freedom given by trichromacy of human photopigments translate into three visual channels. One achromatic or broad-band channel and two color-opponent or chromatic channels. One of the limitations of these models is the absence of explicit spatiotemporal variables in their formulation, in consequence they apply only to data obtained with steady-state aperture colors. Fortunately, a very active area of research is characterized by measurements of spatial and temporal properties of chromatic and achromatic mechanisms and the development of the corresponding theoretical concepts. Within that context, here I summarize two psychophysical studies recently completed: the minimum grating match and measurements of chromatic and achromatic afterimages. Data from the first indicate that the spectral sensitivity of the broad-band channel varies with spatial frequency which is consistent with the current notion that this channel encompasses more than one subsystem; data from the second study are consistent with another current notion: that the r-g color-opponent channel and one of the achromatic subsystems branch out from a common processing stage other than photoabsorption.
Experimental Results of a Low-Order Adaptive Optics Experiment on the Starfire 3.5m Telescope
Authors: Gonglewski John D. , Dayton David , Sandven Steven , Laughlin Darren , Rogers Sam , McDermott Scot , Browne Stephen , Babnick Robert , Rae Joe , Gallegos Joe , Highland Ron
Published: February 2023

An experiment with a nasmyth adaptive optics system mounted on the SOR 3.5m telescope is described. The 183 actuator mirror allows only partial compensation in the near IR, and the imagery is enhanced by postprocessing methods. We describe the system design, and evaluate the performance based on long-to-short exposure SNR ratio metrics.
United Kingdom Adaptive Optics Programs
Authors: Gilmore Gerry
Published: February 2023

The UK has a funded, national program underway to design and construct facility (common user) natural guide star (NGS) adaptive optics systems for two telescopes: • The 4.2m William Hershel Telescope (WHT) on La Palma, Canary Islands. • The 3.8m United Kingdom Infrared Telesope (UKIRT) on Mauna Kea, Hawaii. These will be locally-supported systems, capable of feeding a number of science instruments, including dedicated AO-optimised imagers and spectrographs. They will be optimised for operation in the near infrared, ~ 2 μm.
The Adaptive Optics system for the Telescopio Nazionale Galileo (TNG)
Authors: Ragazzoni R. , Bonaccini D.
Published: February 2023

The Telescopio Nazionale Galileo (namely the Italian National Telescope “Galileo”) is a national 3.5m facility under construction at the Roque de Los Muchachos in Canary Islands. It consists into a classical Ritchey-Chretien optical configuration with two nasmith foci available. Of the two foci one is devoted to imaging, both in the InfraRed and in the visible, the other is mainly devoted to spectroscopy.
Keck Observatory Adaptive Optics Program
Authors: Wizinowich Peter L. , Gleckler Anthony D.
Published: February 2023

The Keck Observatory, in collaboration with Lawrence Livermore National Laboratory (LLNL), is currently in the design phase of a natural guide star and single laser beacon adaptive optics (AO) facility for the Nasmyth platform of the Keck II telescope. Two science instruments will accompany the AO system: a near infrared camera (NIRC-2) being built at Caltech and a near infrared spectrometer (NIRSPEC) being built at UCLA. The goal is to make use of the diffraction-limited resolution (0.02 arcsec at 1 μm) and collecting aperture (10 m) of the Keck telescope, at an excellent site, to produce a new era in ground-based astronomical science.
The GEMINI Adaptive Optics System
Authors: Racine René
Published: February 2023

The GEMINI telescopes project in an international partnership between the United States of America, the United Kingdom, Canada, Chile, Brazil and Argentina to built two eight-meter astronomical telescopes, one on Mauna Kea, Hawaii and one on Cerro Pachon, Chile. The top science requirement of these instruments is superb image quality. It is intended that, in the absence of atmospheric seeing, the telescopes would deliver fully diffraction limited long exposure images in the K-band (2.2 μm). Accordingly, the telescopes and their enclosures have been designed and are being constructed with exacting attention to optical quality, thermal equilibrium and servo control accuracy. This, and the excellent natural seeing at the sites - FWHM = 0.45 arcsec (median), 0.25 arcsec (best 10th percentile) - will make the GEMINI telescopes performances well suited for further improvement by adaptive optics (AO). The Mauna Kea telescope will be highly optimized for performance in the thermal infrared, with an emissivity specification of <4% (2% goal).
Fast Centroiding Algorithms for CCD based Shack-Hartmann Sensors
Authors: Vick Andrew J. A.
Published: February 2023

Preliminary results from simulations of slope estimation algorithms for CCD-based Shack Hartmann wavefront sensors.
Adaptive Optics NIR Imaging of R136 in 30 Doradus: The Stellar Population of a Nearby Starburst
Authors: Brandl B. , Sams B.J. , Bertoldi F. , Eckart A. , Genzel R. , Drapatz S. , Hofmann R. , Loewe M. , Quirrenbach A.
Published: February 2023

We report 0.″15 resolution near infrared imaging of the starburst cluster R136. Our 12.″8 × 12.″8 images were recorded with the MPE camera SHARP II at the 3.6m ESO telescope, using the adaptive optics system COMEON +. The diffraction-limited spatial resolution and high sensitivity (20th magnitude in K) of our observations allow our H and K band images to be compared and combined with recent HST WFPC2 data of R136. Fitting theoretical models to the observed magnitudes we derive the stellar population, age and dynamics of this starburst region. The radial variation of the mass function and the dependence of the derived core radius on the observed stellar mass range reveal strong mass segregation that is probably due to the cluster’s dynamical evolution.
High Quality Liquid Crystal Spatial Light Modulators for Adaptive Optics
Authors: Love Gordon D. , Restaino Sergio R. , Carreras Richard A. , Loos Gary C. , Sharpies Ray M. , Morrison Rob V.
Published: February 2023

Our work involves investigating adaptive wavefront correctors which may be used as alternatives to the deformable mirror in an adaptive optics system. Liquid crystal spatial light modulators (LC–SLMs) have several advantages over deformable mirrors, and also some problems of their own, as discussed in ref [1]. Much of the past work on LCs has centered around using modified LG displays which were not designed as high quality optical elements. In this paper we describe results produced using a LC-SLM which was designed specifically for wavefront correction and shaping.
Atmospheric Compensation using non-linear optical phase conjugation
Authors: Cook G , Jones D C , Ridley K D , Scott A M
Published: February 2023

Conventional adaptive optics have been developed over many years for the purpose of imaging and for directing laser beams through atmospheric turbulence. In this application light from a known point source is collected and a mirror or phase shifting array is modified until the collected light can be focused to form a point image. When this goal is achieved then a collimated laser beam can be directed back through the optical system and will retrace the path of the incident light back to the source. The limitations of conventional adaptive optics are determined by the time taken to measure the wave-front and move actuators, the number of actuators available and hence the degree of compensation which can be achieved, and the degree of computation required to get effective compensation.
Status of the first generation adaptive optics system for the Starfire Optical Range 3.5 m telescope
Authors: Fugate Robert Q.
Published: February 2023

The Starfire Optical Range is currently in the process of commissioning a 3.5 m telescope for adaptive optics research. The optical configuration of the telescope allows two large and one small experimental packages to be mounted in the nasmyth area of the coude path. It is feasible to put low order adaptive optics instruments at these locations for maximum light throughput.
Advanced Electro-Optical System (AEOS) and Starfire Optical Range (SOR) Adaptive Optics
Authors: Kenemuth John R. , Fender Janet S. , Ellerbroek Brent L. , Passaro James R. , Pennington Tim , Meline Michael E. , Berger Paul J. , Ealey Mark A. , Neufeld Conrad , Abreu Rene , Zmek William P.
Published: February 2023

The purpose of the Advanced Electro-Optical System (AEOS) Adaptive Optical (A/O) System is to dynamically correct for atmospheric turbulence, so that a vastly improved image quality is achieved. The AEOS adaptive optical system is located directly beneath the new 3.6 meter telescope. Coude optics in the telescope transfer the ± 150 urad telescope FOV in the waveband from 0.5 to 5 µm to the A/O system.
High Accuracy Capacitive Displacement Transducer for the Position Local Control Loops at the Adaptive Secondary
Authors: Biliotti Valdemaro , Biasi Roberto , Brusa Guido , Gallieni Daniele , Spairani Roberto , Aiello Roberto
Published: February 2023

The thin faceplate adaptive secondary mirrors are controlled by means of electromagnetic force actuators, which seem to be a suitable choice in terms of stroke, accuracy and cost [Del Vecchio, Gallieni et al.; Biasi, Gallieni et al. in this Conference]. Those actuators need a local control loop to achieve a linear position response. The position sensor is definitely a crucial component of this control loop: both high sensitivity and high speed have to be achieved at same time.
Gemini 8-Meter Telescopes Active and Adaptive Optics Update
Authors: Oschmann Jim , Simons Doug , Robertson Dave , Mountain Matt , Kurz Dick , Jenkins Charles , Herriot Glen
Published: February 2023

The Gemini 8-Meter Telescopes are being designed to deliver near diffraction limited images at infrared wavelengths to the focal plane. This will be achieved with a combination of innovative telescope design, a fully active control system and a natural guide star adaptive optics (AO) system for the Mauna Kea Telescope. An overview of how the Gemini Adaptive Optics System works in concert with the active systems employed on the Gemini telescopes is given. Extensive trades have been made in determining the mix of sensors to support both active and adaptive operation. The current concept of how the systems will work in concert is presented here.
Gemini 8 Meter Telescopes Active Guiding System Considerations
Authors: Jenkins Charles , Dillon Nick , Burns Mike , McGonegal Rick , Oschmann Jim , Robertson David
Published: February 2023

The GEMINI telescopes are intended to deliver very good image quality with only tip-tilt correction at the secondary mirror. Designing the guiding systems for these telescopes has made use of simple yet accurate models of the image size. These are described here, with illustrations of the complex tradeoffs that are necessary to achieve the best images. The current design of the guiders is given. These also serve as active optics wavefront sensors to provide closed loop control of the telescope alignment and figure at slow rates.
Deformable Mirrors: A Commercial Product?
Authors: Ealey Mark A.
Published: February 2023

Xinetics originally announced a line of cost-effective deformable mirrors in March 1994. The mirrors featured repairable construction at one quarter the cost of previous products. We report on 37, 97, and 349 channel mirrors in terms of application, customer, and performance. Application range from the use of a 37 channel DM used to better image the human retina to the 97 channel upgradeable DM built for the Max Planck Institute fur Astronomie, to the 349 channel DM built for JPL Palomar Adaptive Optics. A summary will also be given on the role of the USAF Cooperative Research Development Agreements (CRDA) in giving small business the opportunity to compete on a global scale.
Results from the MMT Adaptive Optics Infrared Imager FASTTRAC II
Authors: Close L. M. , Lloyd-Hart M. , Angel J. R. P. , McCarthy D. W. , Brusa G. , McLeod B. A. , Groesbeck T. D. , Wittman D. M. , Ryan P. T. , Martinez T. , Gray P. , Hughes J. M. , Cheselka M. , Jacobsen B. , Bruns D. G. , Sandler D. G.
Published: February 2023

The mission of the Center for Astronomical Adaptive Optics (CAAO) at Steward Observatory is to develop a diffraction-limited laser guide star adaptive optics system. This system is targeted for the new 6.5m mirror MMT upgrade. This single mirror will be installed in the existing Multiple Mirror Telescope (MMT) mount in late 1996 (to replace the existing six individual 1.8m primaries). Presently CAAO has focused on implementing a simpler instrument which tip-tilt corrects all six beams from the existing MMT. The major features of this instrument (called FASTTRAC II) will be used in the 6.5m system with minimal changes. In addition, FASTTRAC II fully addresses all the major optical, electrical, mechanical and computational challenges of having a common user instrument on a ALT-AZ mount utilizing a sodium laser guide star.
Approaches for Image Processing Supporting Adaptive Optics
Authors: Currie Douglas G. , Avizonis Petras V. , Dowling Daniel M. , O'Leary Dianne P. , Nagy James G. , Fugate Robert Q.
Published: February 2023

Image processing methods, highlighting specific hardware systems, will be demonstrated. Correcting spatial dependence and instrumental artifacts of the Point-Spread-Function significantly improves image guality.
Dynamic Adaptive Mirror in the Algorithm of Phase Conjugation
Authors: Kanev F. Yu. , Lukin V.P. , Lavrinova L.N.
Published: February 2023

Considering numerically the problem of adaptive compensation of intensive laser beam atmospheric aberrations we demonstrated the influence of transient processes that occur in adaptive systems on the effectiveness and rate of control.
WaveLab - Hartmann Sensor Data Analysis Software
Authors: Wirth Allan
Published: February 2023

WaveLab is a Hartmann wavefront sensor data analysis system that permits virtually any Hartmann test data to be quickly converted to wavefronts and all derivative types of information such as point spread functions, OTFs, and encircled energies. It uses a graphical interface that makes standard data reduction straightforward and also provides a command line interface for customized data handling. It is user customizable in two ways: WaveLab is an extension to the tcl scripting language and all of the high level reduction routines are in the form of tcl scripts. The user may add their own scripts to handle data in specialized ways. Secondly, the user may add c language functions to the WaveLab / tcl system. This allows the inclusion of more esoteric or complex routines than maybe easily coded at the tcl script level. All the data files used or generated by WaveLab are in an extension of the FITS format.
Astronomy With Adaptive Optics
Authors: Léna P.
Published: February 2023

The operation of the ESO ComeOn adaptive optics system, under its successive improved versions at La Silla on the 3.6 m telescope since 1991, has produced a great number of new scientific results. In addition, it has started a learning process for an efficient use of adaptive optics in diffraction-limited imaging from the ground with large telescopes. Finally, it suggests new, original applications of adaptive optics, some of them being implemented or on the way to be implemented.
Compensated Imaging System (CIS) Observations of the Circumstellar Envelope of P-Cygni
Authors: Morossi C. , Franchini M. , Ragazzoni R. , Sedmak G. , Suzuki A. , Albetski J. , Africano J. , Nishimoto D. , Restaino S.
Published: February 2023

This project is a direct result from OSA and the ESO's first adaptive optics conference. The objective for the Air Force Maui Optical Station (AMOS) was to collaborate and present to the astronomical community the benefits and advantages of using an adaptive optics system for astronomical imaging research.
Observational Results from the University of Hawaii Adaptive Optics System
Authors: Graves J.E. , Roddier F. , Roddier C. , Northcott M.
Published: February 2023

Summary not available.
High Resolution Spectroscopy with an Adaptive Optics Telescope
Authors: Woolf N. , Angel J.R.P. , Black J. , Ge J. , Jacobsen B. , Lloyd-Hart M. , Fugate R.
Published: February 2023

High resolution spectroscopy of stars has been rarely used because at visible wavelengths, the atmosphere produces a star image typically 10-20 times the diffraction limit of the telescope. Either the grating must be used at a far poorer resolution than its diffraction limit, or much light must be lost at the slit.
Experimental Study of Compensation for Laser Thermal Blooming
Authors: Youkuan Li , Xinwei Zhang , Yi Su , Kai Zhang
Published: February 2023

Using 19-element adaptive optics system, real-time correction for laser thermal blooming was realized; far field energy was 2.7 times higher without correction.
Methods of Adaptive Optics for Control the Output Radiation of Industrial Lasers
Authors: Kudryashov A. V.
Published: February 2023

The application of lasers in technological processes and medicine needs the creation of special systems of control and formation of given radiation characteristics on the developed object. Such tasks could be solved by use of elements and methods of adaptive optics.
Adaptive Secondary Development
Authors: Bruns Donald , Barrett Todd , Brusa Guido , Biasi Roberto , Gallieni Daniele
Published: February 2023

The MMT will be converted to a single 6.5 m primary mirror in 1997. The new telescope will be equipped with adaptive optics for high-resolution infrared astronomy at wavelengths between 1.6 microns and 5 microns. Atmospheric distortions will be corrected using an adaptive secondary mirror which directly feeds a high-resolution infrared detector. The use of an adaptive secondary maximizes emissivity, which provides high throughput to the imaging detector and efficient wavefront sensing by eliminating many optical elements normally needed in Coudé systems.
Lick Observatory Laser Guide Star Adaptive Optics System Commissioning
Authors: Olivier Scot S. , An Jong , Avicola Kenneth , Bissinger Horst D. , Brase James M. , Friedman Herbert W. , Gavel Donald T. , Macintosh Bruce , Max Claire E. , Waltjen Kenneth E.
Published: February 2023

A sodium-layer laser guide star adaptive optics system has been developed at Lawrence Livermore National Laboratory (LLNL) for use on the 3 meter Shane Telescope at Lick Observatory located on Mount Hamilton, near San Jose, California. The system is based on a 127-actuator continuous-surface deformable mirror, a Hartmann wavefront sensor equipped with a fast-framing low-noise CCD camera, and a pulsed solid-state-pumped dye laser tuned to the atomic sodium resonance line at 589 nm. Figure 1 shows a picture of the laser beam being projected from the dome of the Shane Telescope.
The Palomar Adaptive Optics System
Authors: Dekany Richard G.
Published: February 2023

Currently under construction at the Jet Propulsion Laboratory, the Palomar Adaptive Optics System (PALAO) is a Cassegrain-mounted system for infrared astronomy incorporating active laser metrology to minimize the effects of mechanical flexure.
Future Directions for the University of Hawaii Adaptive Optics Program
Authors: Graves J. Elon
Published: February 2023

The highly successful AO program at the UH is now planning to expand the curvature technology into higher order correction systems with a unique Vis/IR WFS concept.. Computer simulation have been carried out scaling the current 13 element system now being used at the CFHT on Mauna Kea to a 36 element design. The Vis-IR WFS sensor is expected to increase the performance overall, all as it is used to study young stellar objects that are at many times deeply reddened. An example is HL Tau, in the visible it is around magnitude 14 and at the H band it magnitude 9 or 100 times brighter!
Optimization of the Starfire Optical Range 3.5 M adaptive optics for astronomical imaging
Authors: Link Donald J. , Vernon Russell G.
Published: February 2023

SAIC has developed a wave-optics, time domain, engineering simulation of adaptive optics systems. The Atmospheric Compensation Simulation (ACS) includes both physics effects (e.g., inner and outer scale, various turbulence profiles, wind, anisoplanatism, time of flight, scattering, absorption, sodium layer saturation) and engineering effects (e.g. jitter, misregistration, latency, digital controls, control surface electro-mechanical response, gain variation, shot and detector noise, quantization, aberrations). The code includes the ability to model multiple three-dimensional laser guidestars, propagating the lasers up from the ground and imaging the irradiance from multiple atmospheric layers onto the detector plane using multiple optical transfer functions or speckle imaging. This simulation has been used to support engineering development on a number of programs and has been validated against theory, experiments, and other codes.
Mechanically-Induced Line-of-Sight Jitter in the Starfire Optical Range 1.5 Meter Telescope
Authors: Brown James M. , Goodding James C.
Published: February 2023

Prior to the use of adaptive optics, many sources of line-of-sight jitter were masked by atmospheric effects. That is, we cannot observe small jitter in the optical data while wave-front distortions dominate the error in our images. However, we have seen that seemingly negligible error sources become significant as we conquer the atmospheric problems.
Keck Adaptive Optics: Optical Bench Subsystem
Authors: Gregory T. , Wizinowich P. , Acton D. S. , Gleckler A. , Stomski P. , Radau S. , Maute J. , Sirota M.
Published: February 2023

The W. M. Keck Observatory and Lawrence Livermore National Labs are currently developing an adaptive optics (AO) system for use on the 10-meter Keck II telescope. This paper will review the Optical Bench Subsystem, placing emphasis on the requirements that led to the current design.
Five-order adaptive optics for meter-class telescopes
Authors: Bruns Donald G.
Published: February 2023

A low order adaptive optics system for astronomical telescopes based on simple optics and commercially available key components can serve as more than an introduction to adaptive optics hardware and testing. For a one meter telescope, in the case of (D/r0) between about five and eight, only five correction orders are required to produce significantly improved images. Such a low order system has been designed and built, using translating lenses to produce smooth aberration corrections. The system, called the AO-5, is meant to correct atmospheric turbulence in the visible and near infrared spectral regions. This paper reports on measurements of the corrections applied to synthesized atmospheric aberrations created by a turbulence generator. The AO-5 will installed in the summer of 1996 on one of the Meyer Foundation's dual 0.72 m Ritchey-Cretién telescopes on the 4300 meter level of Mount Evans, Colorado.
Natural Guide Star Adaptive Optics for the 4.2m William Herschel Telescope
Authors: Buscher David , Doel Peter , Humphreys Ron , Myers Richard , Wells Martyn , Longmore Andy , Gentles Bruce , Jones Gareth , Worswick Sue
Published: February 2023

The William Herschel Telescope (WHT) is a 4.2m telescope on La Palma, one of the Canary Islands. The University of Durham (UK) ELECTRA AO system and WHT Natural Guide Star (NGS) AO projects have entered a close collaboration to build a series of AO systems culminating in the WHT NGS system which is specified for common-user (facility) astronomical operation. The collaboration is intended to reduce technical risk through a staged development and to deliver various performance enhancements, based on the ELECTRA segmented mirror design, to the final system. The ELECTRA system, its performance and the project stages are described. The final NGS stage has an opto- mechanical design which permits AO correction to be performed at variable conjugate heights and to dither the science camera field without changing the science pupil. This system and its projected performance are described.
A Low Cost, High Performance, Self-Scanning Correlating White Light Fringe Tracker System
Authors: Baker Jeffrey T. , Percheron Isabelle , Sanchez Darryl
Published: February 2023

The concept of using a phased array of small, inexpensive telescopes to achieve high angular resolution of faint, distant objects is nothing new, but the practical considerations of alignment and cophasing has always limited its implementation. To be effective, the coupling of white light from these telescopes must be done in such a way as to achieve zero optical path difference (OPD) between the object being studied, the telescopes, and the point of beam recombination. In practice, this has always been very difficult due to (1.) static and time varying OPD errors from mechanical sources, (2.) large but predictable OPD shifts due to geometrical aspects of the telescopic array, and, (3.) rapid atmospheric turbulence based OPD modulations. In addition to phase errors, one must also deal with time varying mechanical and turbulence based angular misalignments of the beams.
Analysis of Sodium Layer Scattering Physics
Authors: Milonni Peter W. , Telle John M.
Published: February 2023

We describe calculations of the photon return signals from mesospheric sodium fluorescence excited by laser pulse trains. The theory combines a full density–matrix treatment of the sodium D2 line, including Doppler broadening and polarization–dependent optical pumping effects, with the Fried model of optical propagation through the turbulent atmosphere.
Modal wavefront correlations in laser guide star adaptive optics
Authors: Rousset Gérard , Molodij Guillaume , Laurent Sylvain
Published: February 2023

Because the sky is insufficiently populated with bright natural guide stars to cover all high angular resolution programs using adaptive optics, the concept of artificial guide star was proposed to overcome this difficulty1,2: A laser guide star (LGS) is created by the atmospherically scattered light of a laser beam directed towards the object of interest. Successful results have been recently reported by Fugate et al.3 and Primmerman et al.4. Two types of backscattering effect are considered:

1) Rayleigh and Mie scattering from molecules and dust generating LGS at altitude between 5 and 18 km.

2) Resonance scattering from the sodium atoms around 90 km altitude.
Performance of Keck Adaptive Optics with Sodium Laser Guide Stars
Authors: Gavel Don , Olivier Scot , Brase Jim
Published: February 2023

The Keck telescope adaptive optics system is designed to optimize performance in the 1 to 3 micron region of observation wavelengths (J, H, and K astronomical bands). The system uses a 349 degree of freedom deformable mirror, so that the interactuator spacing is 56 cm as mapped onto the 10 meter aperture. 56 cm is roughly equal to r0 at 1.4 microns, which implies the wavefront fitting error is 0.52 (λ/2π)(d/r0)5/6 = 118 nm rms. This is sufficient to produce a system Strehl of 0.74 at 1.4 microns if all other sources of error are negligible, which would be the case with a bright natural guidestar and very high control bandwidth. Other errors associated with the adaptive optics system will however contribute to Strehl degradation, namely, servo bandwidth error due to inability to reject all temporal frequencies of the aberrated wavefront, wavefront measurement error due to finite signal-to-noise ratio in the wavefront sensor, and, in the case of a laser guidestar, the so-called cone effect where rays from the guidestar beacon fail to sample some of the upper atmosphere turbulence. Cone effect is mitigated considerably by the use of the very high altitude sodium layer guidestar (90 km altitude), as opposed to Rayleigh beacons at 20 km. However, considering the Keck telescope’s large aperture, this is still the dominating wavefront error contributor in the current adaptive optics system design.
Progress Toward the 6.5-m MMT Infrared Adaptive Optics System
Authors: Lloyd-Hart M. , Angel J. R. P. , Sandler D. G. , Salinari P. , Bruns D. , Barrett T. K.
Published: February 2023

In late 1996, the existing six mirrors of the Multiple Mirror Telescope (MMT) will be replaced by a single 6.5-m mirror, which is now being polished at the Steward Observatory Mirror Lab. Earlier work [1, 2] has shown that an adaptive optics system using a single sodium laser projected co-axially with the telescope can provide imaging at the diffraction limit in the H and K photometric bands over most of the sky. In the design of the system for the 6.5-m, we will project a 4-W beam from a continuous-wave dye laser from a refractive launch telescope [3] located behind the secondary mirror. Returning light will be corrected for the effects of atmospheric turbulence at the secondary mirror, which will be a 2-mm thick continuous facesheet whose shape can be modified at 1 kHz update rate by 300 voice-coil actuators. The major components of the system are shown in the schematic of Figure 1.
Exploring High Altitude Beacon Concepts Other Than Sodium
Authors: Telle John M.
Published: February 2023

Na and most other mesospheric species suffer from two major shortcomings, low density and low saturation intensity. The Na density in the mesosphere is typically 103 - 104 atoms per cm3. Moreover this density is spread over about 100 velocity classes with a natural width of 10 MHz giving a total Doppler width of 1 GHz for each line. The D2 line is split by 1.772 GHz into a doublet ignoring other hyperfine splittings of the order of 10 MHz. The doublet is often treated as a single line with 3 GHz FWHM. The Doppler-broadened Na cross section is about 2.7 (-12) cm2 but the low density results in only about 1.5% unsaturated absorption across the entire mesosphere (depth ≈ 10 km).
The sensing of tip-tilt in Laser Guide Star Adaptive Optical Systems
Authors: Bonaccini Domenico
Published: February 2023

Second generation Adaptive Optical (AO) systems are being built or planned at many astronomical sites, which use Laser Guide Stars (LGS) as reference object in the wavefront sensor for the determination of wavefront aberrations. This is going to increase dramatically the sky coverage and the science throughput of AO systems used at astrophysical sites.
Comparison of Adaptive-Optics Technologies for Large Astronomical Telescopes
Authors: Ellerbroek Brent L. , Northcott Malcolm J. , Rigaut François , Simons Doug
Published: February 2023

The emergence of new wavefront sensing techniques, such as wavefront curvature sensing, opens new pathways for astronomical adaptive optics. Even though the advantages and drawbacks of Shack-Hartmann and curvature wavefront sensing are known [1,2], no direct comparison of complete systems has yet been presented. The goal of this paper is to investigate and compare the performance of Shack-Hartmann and curvature based systems for an eight-meter telescope, evaluated at a 1.6 µm wavelength under median Mauna Kea seeing conditions. This work was made at the request of the Gemini adaptive optics working group, who asked three independant parties to perform adaptive optics system simulations using both technologies. To make the comparison simple enough, a set of conditions was imposed on seeing, telescope size, and wavefront sensor detectors, as summarized in Table 1. Independant simulation codes were used. A common atmospheric turbulence generator provided consistant inputs for all packages.
Tip-Tilt Control Loop Optimization
Authors: Fini L. , Esposito S.
Published: February 2023

We address problems of control loop parameters optimization for tip-tilt correction system based on the approach followed for the T.N.G. tracking system.
Optimization of Bimorph Mirror Electrode Pattern for SUBARU AO System
Authors: Otsubo Masashi , Takami Hideki , Iye Masanori
Published: February 2023

NAOJ has been developing an adaptive optics(AO) system for SUBARU 8.2m telescope. The AO system is composed of a curvature wavefront sensor and a bimorph mirror with 36 elements.
Wavefront Control Optimization using Adaptive Filters
Authors: Lloyd-Hart M. , Rhoadarmer T.
Published: February 2023

A key component in any close-loop adaptive optics (AO) system is the algorithm which converts signals from the wavefront sensor into commands to the correcting element. Much work has recently been devoted to the study of the optimal implementation of this algorithm, both in the theoretical [1, 2] and practical [3] domains.
Active and Adaptive Bimorph Optics: Mirrors, Technology and Design Principles
Authors: Safronov Andrey G.
Published: February 2023

Simplicity and low cost of a so-called "small” adaptive optics or the adaptive optics for low order correction make it more preferable for use than a traditional techniques. Adaptive bimorph mirrors appear to be the optimum wavefront corrector for such systems. The existing bimorph mirrors have some disadvantages, namely, a limited size of the aperture under control and low sensitivity.
The liquid crystal glassess with local modulation
Authors: Tomilin Maxim G. , Onokhov Arkadi P. , Isaev Michail V. , Reznichenko Vladimir V. , Kogan Vladimir I.
Published: February 2023

A mack-up of a nematic liquid crystal (LC) glassess with local modulation has developed for wide application. Both design features of the LC sell and requirements to its are concedered. The processing technology is investigated for preperation new princple of local modulation . The modulator electro-optical responses obtained show the wider potentialities of the device application.
Searching for Brown Dwarfs and Extra-Solar Planets from the Ground Using Adaptive Optics
Authors: Sandler David , Stahl Steven , Angel Roger
Published: February 2023

The adaptive optics system under development for the new 6.5 m MMT, using an adaptive secondary mirror, will allow direct detection of cool brown dwarfs much closer in than Gliese 229B. An advanced system with 10,000 actuators will allow direct detection of Jupiter-like planets around bright stars within 10 pc. Requirements and detection limits will be discussed.
Focault-like Wave-Front Sensor
Authors: Riccardi A. , Esposito S. , Ragazzoni R. , Fini L. , Ranfagni P.
Published: February 2023

We present first laboratory results for a focault-like wave-front sensor suitable for adaptive optics systems based on a squared-based refractive pyramid.
Sparse aperture phasing with phase diversity: Experimental Results
Authors: Kendrick Rick , Bell Ray , Duncan Alan
Published: February 2023

Phasing the sub apertures of a multiple aperture telescope is a difficult problem that has been addressed in various ways. Hartmann sensors and knife edge tests are techniques that work well for point source objects such as stars. Null fringe tracking is also suitable for point sources. However, none of these techniques are adequate for extended object imaging. Radial shearing white-light interferometers have been proposed and tested but are complicated to implement and have a strong object dependence. Laser metrology systems are extremely accurate but do not give a direct measurement of the phase errors and can be difficult to implement. Phase diversity is a very simple phasing technique that is suitable for extended objects and has developed into a mature technology over the past five years.
Keck Adaptive Optics: Error Budget
Authors: Wizinowich Peter
Published: February 2023

The optics error budgets for the W.M. Keck Observatory natural guide star (NGS) and laser guide star (LGS) adaptive optics (AO) facilities' are presented. The purpose of generating this error budget2 is three-fold: (1) to summarize the error sources which will contribute to the degradation of images on a science instrument fed by the AO facilities, (2) to compare the predicted performance with the requirements, and (3) to provide a tool for evaluating potential engineering, and observing, trade-offs.
AO Based Spectroscopy: Prospects and Pitfalls
Authors: Monnet Guy
Published: February 2023

Summary not available.
Speckle techniques for adaptive optics in the partial correction regime
Authors: Tessier E. , Perrier C.
Published: February 2023

Adaptive optics (AO) works in many cases in the partial correction regime, i.e. with a Strehl ratio lower than 0.8. In this regime, seeing variations induce some variations in the correction (see Tessier 95), as shown on Fig. 1 which plots the Strehl ratio for continuous frames taken with the Come-On Plus instrument (see Beuzit et al. 94 for a description of this instrument).
Adaptive Optics for the Human Eye
Authors: Williams David R. , Liang Junzhong , Miller Donald T.
Published: February 2023

Aberrations limit the optical quality of the normal human eye, particularly when the pupil is large. These aberrations reduce the eye's contrast sensitivity to high spatial frequencies in the visual environment. They also limit the resolution of cameras designed to image the living human retina, a critical tool in the diagnosis and treatment of retinal disease. The eye's aberrations generally prohibit imaging structures in the living retina the size of single cells. Though it is possible to correct defocus and astigmatism with spectacle lenses, additional aberrations such as coma, spherical, and higher order aberrations remain. Moreover, the pattern of aberrations is highly variable from eye to eye, so that each eye must be independently corrected.
Focal anisoplanatism and conjugation of the correcting surface to turbulence
Authors: Wells Martyn , Klückers Vince , Adcock Miles
Published: February 2023

When using a laser guide star (LGS) as the reference object in an adaptive optics system the accuracy of the correction is limited by the so-called 'cone-effect' or focal anisoplanatisism (FA). There are two effects

a) the footprint of the LGS wavefront at the turbulent layer is smaller than that for the wavefront from the science object and

b) the LGS wavefront expands by a factor of (1+hturb/hNa) when it reaches the telescope pupil. For example - with the height of turbulence hturb =6.5 km and the height of laser guide star hNa=90km at the edge of an 8m pupil there is a displacement of ≈30cm between the actual and measured wavefront from a science object
Focal Spot in the Presence of Phase Dislocations
Authors: Tartakovski V. A. , Mayer N. N.
Published: February 2023

At present the Hartmann wavefront sensor design has not been sufficiently supported by necessary researches. The motion and structure of focal spots in the region of strong intensity fluctuations and in the presence of phase dislocations of wave function have not been adequately explored.
Coronagraphic Spectrometer
Authors: IYE Masanori , MURAKAWA Kouji , ITO Youichi , EBIZUKA Noboru , TAMURA Motohide
Published: February 2023

Observations of faint diffuse and/or unresolved objects in the vicinity of bright objects are of importance in the studies of protoplanetary disks, circumstellar envelope of red supergiants, quasar host galaxies, emission line regions of AGNs, and gravitational lensed objects.
Phase Diversity Wavefront Sensing and Image Reconstruction on the MDI instrument at L1
Authors: Tarbell T. D. , Acton D.S. , Frank Z. A.
Published: February 2023

The Michelson Doppler Imager (MDI) is a spectral imaging experiment on the ESA-NASA Solar and Heliospheric Observatory spacecraft (SOHO-see Domingo et al., 1995). SOHO was launched in December, 1995, and reached its final orbit about the Earth-Sun Lagrangian point L1 in mid-February, 1996. This point, about 1.5×l06 km towards the Sun, is where the Earth’s and Sun’s gravity balance, allowing a nearly stable orbit ideal for continuous observations of the Sun and solar wind. MDI is collecting the observational data for the Solar Oscillations Investigation (SOI), a study of the interior structure of the Sun as inferred from the normal modes of oscillation seen on its surface (“heliosesmology”). Since launch, MDI has been collecting images showing the Doppler velocity, continuum intensity, and magnetic field on the solar surface with high spatial and temporal resolution. SOI/MDI were developed jointly by Stanford University and Lockheed Martin Advanced Technology Center, supported by NASA (see Scherrer et al., 1995). The Principal Investigator is Prof. P. Scherrer of Stanford.
Properties of Resonant Two-Photon Processes in Photorefractive Media
Authors: Paraschis L. , Bashaw M. C. , Liu A. , Hesselink L.
Published: February 2023

Summary

Holographic data storage systems [1] require sensitive
optical materials that provide some means of nondestrective readout
[2]. Among the number of techniques for nonvolatile
readout available [2]. the sensitazation of a
photorefractive medium by illumination at one wavelength, called
gating, for writing at a second using a resonant two-photon process,
constitutes the most versatile all-optical nondestructive method.
Typically, this process consists of absorption of a photon at
frequency ω1 to generate an
intermediate excited state, followed by absorption of a second at
ω2 to generate a free carrier
[3, 4, 5]. Gating occurs for absorption of two photons
at two different wavelengths. In the present work, we identify the
critical physical characteristics of the processes that provide the
simultaneous realization of true gating and writing sensitivity at a
variety of frequencies, evaluate the refractive index perturbation and
the response rate, and investigate the significance of the the
intermediate state occupancy and the arisining nonlinear
photorefractive behavior at its saturation regime.