Glenn Tyler - Academia.edu (original) (raw)

Papers by Glenn Tyler

Research paper thumbnail of Image coding with far-field holograms (A)

Journal of the Optical Society of America, 1977

Title: Image coding with far-field holograms (A). Authors: Tyler, Glenn A. Publication: J. Opt. S... more Title: Image coding with far-field holograms (A). Authors: Tyler, Glenn A. Publication: J. Opt. Soc. Am., vol. 67, page 1381. Publication Date: 00/1977. Origin: OSA. Keywords: HOLOGRAPHY, INFORMATION PROCESSING. Bibliographic Code: 1977OSAJ...67Q1381T. Abstract. ...

Research paper thumbnail of Target-based coherent beam combining of an optical phased array fed by a broadband laser source

Journal of Modern Optics, Jul 18, 2017

The target-based phasing of an optical phased array (OPA) fed by a broadband master oscillator la... more The target-based phasing of an optical phased array (OPA) fed by a broadband master oscillator laser source is investigated. The specific scenario examined here considers an OPA phasing through atmospheric turbulence on a rough curved object. An analytical expression for the detected or received intensity is derived. Gleaned from this expression are the conditions under which targetbased phasing is possible. A detailed OPA wave optics simulation is performed to validate the theoretical findings. Key aspects of the simulation setup as well as the results are thoroughly discussed.

Research paper thumbnail of <title>Turbulence Induced Adaptive Optics Performance Degradation: Evaluation In The Time Domain</title>

Proceedings of SPIE, Jul 12, 1983

Normally one of the two approaches is used to evaluate the performance of an adaptive optics syst... more Normally one of the two approaches is used to evaluate the performance of an adaptive optics system. In the first approach the normalized antenna gain (or Strehl ratio) associated with a variety of degrading effects acting alone is evaluated. The normalized antenna gain of the system when degraded by a combination of these effects is then found by forming the product of the individual antenna gains involved. The second approach is to evaluate system performance by simulation on a large mainframe computer. In the work presented here, physical optics formulas and elementary statistical concepts are used to develop an approach that shares some of the advantages of both of these previous approaches. By working in the time domain, relatively simple formulas are developed that shed insight into the factors that degrade adaptive optics system performance. In addition, the impact of several degrading factors acting simultaneously can be evaluated. In this study the normalized antenna gain is evaluated for a system degraded by turbulence, anisoplanatism, a finite servo bandwidth and a combination of anisoplanatism and a finite servo bandwidth. In the finite servo bandwidth study, system performance is evaluated as a function of diameter illustrating that the resulting antenna gain decays from the diffraction limited antenna gain to the large diameter asymptotic limit antenna gain first predicted by Greenwood. The diameter dependence of this effect is similar to that due to anisoplanatism but not as severe at intermediate diameters. The last study evaluating the combined degradation associated with anisoplanatism and a finite servo bandwidth illustrates the important role played by high temporal frequency phase information. Introducing a finite bandwidth to a system already degraded by anisoplanatism can actually improve performance slightly, in certain cases, because highly distorted high frequency information is lost.

Research paper thumbnail of Characteristics Of Turbulence Measured On A Large Aperture

Proceedings of SPIE, Aug 10, 1988

An experiment to collect data on atmospheric turbulence has been conducted on the 107-in telescop... more An experiment to collect data on atmospheric turbulence has been conducted on the 107-in telescope located at the McDonald Observatory in Texas. The phase and the intensity of aberrated starlight have been measured over the aperture of the telescope. Simultaneous measurements of free-atmosphere seeing and local temperature differences have been made to gauge the strength of turbulence within the dome vs. turbulence in the free atmosphere.

Research paper thumbnail of Spatial–temporal-covariance-based modeling, analysis, and simulation of aero-optics wavefront aberrations

Journal of the Optical Society of America, Jun 30, 2014

We introduce a framework for modeling, analysis, and simulation of aero-optics wavefront aberrati... more We introduce a framework for modeling, analysis, and simulation of aero-optics wavefront aberrations that is based on spatial-temporal covariance matrices extracted from wavefront sensor measurements. Within this framework, we present a quasi-homogeneous structure function to analyze nonhomogeneous, mildly anisotropic spatial random processes, and we use this structure function to show that phase aberrations arising in aero-optics are, for an important range of operating parameters, locally Kolmogorov. This strongly suggests that the d 5∕3 power law for adaptive optics (AO) deformable mirror fitting error, where d denotes actuator separation, holds for certain important aero-optics scenarios. This framework also allows us to compute bounds on AO servo lag error and predictive control error. In addition, it provides us with the means to accurately simulate AO systems for the mitigation of aero-effects, and it may provide insight into underlying physical processes associated with turbulent flow. The techniques introduced here are demonstrated using data obtained from the Airborne Aero-Optics Laboratory.

Research paper thumbnail of Accommodation of speckle in object-based phasing

Journal of the Optical Society of America, Apr 19, 2012

This work addresses the physical basis of the measurement process for object-based phasing of an ... more This work addresses the physical basis of the measurement process for object-based phasing of an array of telescopes. In this regard an enhanced least-squares estimator that is capable of differentiating among three families of array aberrations in an object-based phasing system is developed. In a system of this nature the system to be phased illuminates the object of interest and the return radiation is detected. Telescope aberrations, atmospheric aberrations, and speckle-induced aberrations are all reported by the estimator to facilitate correction of telescope and atmospheric aberrations. This is accomplished by proper handling of the unobservable modes and recognizing that the five global aberrations-telescope array piston, atmospheric array piston and tilt, and speckle array piston and tilt-cannot be measured accurately so they need to be projected out of the estimated piston commands. Except for these relatively benign array aberrations, the disturbances for all three families of array aberrations are estimated exactly. An interesting feature of the speckle array aberrations is that a synthetic aperture is developed that is almost twice as large as the array of telescopes under consideration.

Research paper thumbnail of Influence of atmospheric turbulence on the propagation of quantum states of light carrying orbital angular momentum

Optics Letters, Jan 12, 2009

We analyze the influence of atmospheric turbulence on the propagation of an optical vortex beam h... more We analyze the influence of atmospheric turbulence on the propagation of an optical vortex beam having the form V͑r , ͒ = A 0 e im. The probability that a detected photon after propagating through the atmosphere has the same value of the orbital angular momentum as the launched photon is found to be given by ͗s 0 ͘ = ͓1 + ͑1.845D / r 0 ͒ 2 ͔ −1/2 , where D is the aperture diameter and r 0 is the Fried coherence diameter. These vortex beams behave very similarly to Laguerre-Gauss beams under the influence of atmospheric turbulence. These results have important implications for atmospheric laser communication systems that employ quantum encryption.

Research paper thumbnail of Target-in-the-loop phasing of a fiber laser array fed by a linewidth-broadened master oscillator

Proceedings of SPIE, May 1, 2017

In a recent paper [J. Opt. Soc. Am. A 33, 1931–1937 (2016)], the target-in-the-loop (TIL) phasing... more In a recent paper [J. Opt. Soc. Am. A 33, 1931–1937 (2016)], the target-in-the-loop (TIL) phasing of an RF-modulated or multi-phase-dithered fiber laser array, fed by a linewidth-broadened master oscillator (MO) source, was investigated. It was found that TIL phasing was possible even on a target with scattering features separated by more than the MO’s coherence length as long as the received, backscattered irradiance changed with the array’s modulation or phase dither. To simplify the problem and gain insight into how temporal coherence affects TIL phasing, speckle and atmospheric turbulence were omitted from the analysis. Here, the scenario analyzed in the prior work is generalized by including speckle and turbulence. First, the key analytical result from the prior paper is reviewed. Simulations, including speckle and turbulence, are then performed to test whether the conclusions derived from that result hold under more realistic conditions.

Research paper thumbnail of Zernike-polynomial expansion of turbulence-induced centroid anisoplanatism

Optics Letters, Jun 1, 1985

An expansion of image centroid position after propagation through atmospheric turbulence in terms... more An expansion of image centroid position after propagation through atmospheric turbulence in terms of Zernikepolynomial coefficients is shown to consist of a tilt term plus coma terms. Centroid anisoplanatism therefore arises from turbulence-induced coma distortions. By correcting for coma effects to a sufficiently high order, the deleterious effects of centroid anisoplanatism can be reduced to any desired level. The Strehl ratio is given by the asymptotic formula [1 + A (Diro) 5 / 3 1 ', where A = 0.018(1 + I)-7/3 and I is the number of coma terms corrected. Centroid anisoplanatism, described by Yura and Tavis, 1 can be a serious source of performance degradation in adaptive-optics systems designed to overcome

Research paper thumbnail of Wave-front compensation for imaging with off-axis guide stars

Journal of the Optical Society of America, 1994

Received October 1, 1992; accepted October 20, 1992 The impact of using an off-axis pulsed laser ... more Received October 1, 1992; accepted October 20, 1992 The impact of using an off-axis pulsed laser backscatter reference for compensation of an imaging system is evaluated. For low backscatter altitudes imaging is only weakly affected when the beacon is not in the same direction as ...

Research paper thumbnail of Performance of wavefront sensors in strong scintillation

Proceedings of SPIE, Feb 1, 2003

The estimation accuracy of wavefront sensors in strong scintillation is examined. Wave optical si... more The estimation accuracy of wavefront sensors in strong scintillation is examined. Wave optical simulation is used to characterize the performance of several wavefront sensors in the absence of measurement noise. The estimation accuracy of a Schack-Hartmann sensor is shown ...

Research paper thumbnail of Image-position error associated with a quadrant detector

Journal of the Optical Society of America, Jun 1, 1982

An exact expression is obtained that evaluates the error associated with angular-position measure... more An exact expression is obtained that evaluates the error associated with angular-position measurement of an incoherently illuminated object when a quadrant detector is used in the image plane of an optical system. The accuracy of such a measurement is inversely proportional to the signal-to-noise voltage ratio associated with the four quadrants summed to act as a single detector. In the particular case of a circular object, the rms angular measurement error is given by the expression os = 4r[(3/16)2 + (n/8) 2 ]" 2 (X/D)/SNRu, where n is the angular subtense of the object divided by the diffraction angle X/D, SNRU is the signal-to-noise voltage ratio, X is the wavelength of the light used, and D is the diameter of the limiting aperture in the optical system under consideration.

Research paper thumbnail of Fraunhofer Holography Applied to Particle Size Analysis a Reassessment

Optica acta, Sep 1, 1976

... results are I1=Az exp[ i 2], (4) I2= -Az exp[i2]A*(µ,v)• (5) The evaluation of I3 can be acco... more ... results are I1=Az exp[ i 2], (4) I2= -Az exp[i2]A*(µ,v)• (5) The evaluation of I3 can be accomplished by noting that °° Z k a k , as Azz ak(p - e)2l f exp[ (x - ) 2Iexp o(µ-x) 2 1 dx=exp ] ( exPI o J •(6) 2z I ) 2z 4 z+z 2(z +z)} Thus, the ...

Research paper thumbnail of Adaptive optics compensation for propagation through deep turbulence: a study of some interesting approaches

Optical Engineering, Nov 15, 2012

ABSTRACT Scintillation and anisoplanatism significantly degrade a laser transmitter system or an ... more ABSTRACT Scintillation and anisoplanatism significantly degrade a laser transmitter system or an imaging system when the optical field is required to propagate through deep turbulence. Here turbulence is defined as deep turbulence when the Rytov number is very much greater than 1 and the isoplanatic patch size is much smaller than λ/D, the diffraction limit. In this region a point beacon is of little use for imaging applications and a finite-sized beacon limits performance for both transmission and imaging because almost any finite-sized beacon is many isoplanatic patch sizes across and exhibits a significant level of beacon anisoplanatism. As a consequence, conventional adaptive optics techniques are of little value. To address this situation, five approaches are considered. These approaches include beacon deconvolution, Zernike tomography, gradient descent tomography (GDT), irradiance redistribution branch cut multiconjugate adaptive optics compensation, and minimum energy loss eigenfield propagation. GDT appears to have the most promise as it does not require a conventional wavefront sensor.

Research paper thumbnail of Synthesis of the vector resonator modes from scalar results

Optics Letters, Feb 1, 1980

A technique is presented in which the full vector solution for resonator modes is synthesized fro... more A technique is presented in which the full vector solution for resonator modes is synthesized from the known scalar solution. Second-order perturbation theory is utilized to predict the behavior of a resonator when an imperfect coating on the rear cone results in a phase shift between the s and p polarizations. The theoretical results agree well with a numerical example.

Research paper thumbnail of Rapid evaluation of d_0: the effective diameter of a laser-guide-star adaptive-optics system

Journal of the Optical Society of America, 1994

ABSTRACT

Research paper thumbnail of Turbulence-induced adaptive-optics performance degradation: evaluation in the time domain

Journal of the Optical Society of America, Mar 1, 1984

A time-domain approach has been developed that is capable of evaluating the performance of an ada... more A time-domain approach has been developed that is capable of evaluating the performance of an adaptive-optics system degraded by a wide variety of effects acting together or alone. In the study conducted here the normalized antenna gain (or Strehl ratio) is evaluated for a system degraded by turbulence, anisoplanatism, a finite servo bandwidth, and a combination of anisoplanatism and a finite servo bandwidth. A diameter dependence of these effects is established, illustrating that the degrading influence associated with a finite servo bandwidth is less severe than the degrading influence associated with anisoplanatism over a wide range of diameters. For the case of a small-diameter system degraded by anisoplanatism, system performance improves slightly when a finite servo bandwidth is introduced. correction can provide significant performance improvement. The work presented here concerning anisoplanatism is in exact agreement with Ref. 1 (although obtained by a different procedure) and illustrates the degrading influence of this effect. The last two cases studied contain new results and consider the evaluation of an adaptive-optics system degraded by a finite servo bandwidth or by a combination of aniso

Research paper thumbnail of Reconstruction and assessment of the least-squares and slope discrepancy components of the phase

Journal of the Optical Society of America, Oct 1, 2000

The concept of slope discrepancy developed in the mid-1980&amp;amp;#39;s to assess measuremen... more The concept of slope discrepancy developed in the mid-1980&amp;amp;#39;s to assess measurement noise in a wave-front sensor system is shown to have additional contributions that are due to fitting error and branch points. This understanding is facilitated by the development of a new formulation that employs Fourier techniques to decompose the measured gradient field (i.e., wave-front sensor measurements) into two components, one that is expressed as the gradient of a scalar potential and the other that is expressed as the curl of a vector potential. A key feature of the theory presented here is the fact that both components of the phase (one corresponding to each component of the gradient field) are easily reconstructable from the measured gradients. In addition, the scalar and vector potentials are both easily expressible in terms of the measured gradient field. The work concludes with a wave optics simulation example that illustrates the ease with which both components of the phase can be obtained. The results obtained illustrate that branch point effects are not significant until the Rytov number is greater than 0.2. In addition, the branch point contribution to the phase not only is reconstructed from the gradient data but is used to illustrate the significant performance improvement that results when this contribution is included in the correction applied by an adaptive optics system.

Research paper thumbnail of Holographic simulation of phase contrast (A)

Journal of the Optical Society of America, 1978

Title: Holographic simulation of phase contrast (A). Authors: Tyler, Glenn A. Publication: J. Opt... more Title: Holographic simulation of phase contrast (A). Authors: Tyler, Glenn A. Publication: J. Opt. Soc. Am., vol. 68, page 1382. Publication Date: 00/1978. Origin: OSA. Keywords: HOLOGRAPHY, MICROSCOPY. Bibliographic Code: 1978JOSA...68R1382T. Abstract. Not Available

Research paper thumbnail of Simplified anomalous dispersion model for HF chemical lasers (A)

Journal of the Optical Society of America, 1979

Title: Simplified anomalous dispersion model for HF chemical lasers (A). Authors: Tyler, Glenn A.... more Title: Simplified anomalous dispersion model for HF chemical lasers (A). Authors: Tyler, Glenn A.; Chan, Gilbert. Publication: J. Opt. Soc. Am., vol. 69, page 1458. Publication Date: 00/1979. Origin: OSA. Keywords: LASERS: HF. Bibliographic Code: 1979JOSA...69.1458T. Abstract ...

Research paper thumbnail of Image coding with far-field holograms (A)

Journal of the Optical Society of America, 1977

Title: Image coding with far-field holograms (A). Authors: Tyler, Glenn A. Publication: J. Opt. S... more Title: Image coding with far-field holograms (A). Authors: Tyler, Glenn A. Publication: J. Opt. Soc. Am., vol. 67, page 1381. Publication Date: 00/1977. Origin: OSA. Keywords: HOLOGRAPHY, INFORMATION PROCESSING. Bibliographic Code: 1977OSAJ...67Q1381T. Abstract. ...

Research paper thumbnail of Target-based coherent beam combining of an optical phased array fed by a broadband laser source

Journal of Modern Optics, Jul 18, 2017

The target-based phasing of an optical phased array (OPA) fed by a broadband master oscillator la... more The target-based phasing of an optical phased array (OPA) fed by a broadband master oscillator laser source is investigated. The specific scenario examined here considers an OPA phasing through atmospheric turbulence on a rough curved object. An analytical expression for the detected or received intensity is derived. Gleaned from this expression are the conditions under which targetbased phasing is possible. A detailed OPA wave optics simulation is performed to validate the theoretical findings. Key aspects of the simulation setup as well as the results are thoroughly discussed.

Research paper thumbnail of <title>Turbulence Induced Adaptive Optics Performance Degradation: Evaluation In The Time Domain</title>

Proceedings of SPIE, Jul 12, 1983

Normally one of the two approaches is used to evaluate the performance of an adaptive optics syst... more Normally one of the two approaches is used to evaluate the performance of an adaptive optics system. In the first approach the normalized antenna gain (or Strehl ratio) associated with a variety of degrading effects acting alone is evaluated. The normalized antenna gain of the system when degraded by a combination of these effects is then found by forming the product of the individual antenna gains involved. The second approach is to evaluate system performance by simulation on a large mainframe computer. In the work presented here, physical optics formulas and elementary statistical concepts are used to develop an approach that shares some of the advantages of both of these previous approaches. By working in the time domain, relatively simple formulas are developed that shed insight into the factors that degrade adaptive optics system performance. In addition, the impact of several degrading factors acting simultaneously can be evaluated. In this study the normalized antenna gain is evaluated for a system degraded by turbulence, anisoplanatism, a finite servo bandwidth and a combination of anisoplanatism and a finite servo bandwidth. In the finite servo bandwidth study, system performance is evaluated as a function of diameter illustrating that the resulting antenna gain decays from the diffraction limited antenna gain to the large diameter asymptotic limit antenna gain first predicted by Greenwood. The diameter dependence of this effect is similar to that due to anisoplanatism but not as severe at intermediate diameters. The last study evaluating the combined degradation associated with anisoplanatism and a finite servo bandwidth illustrates the important role played by high temporal frequency phase information. Introducing a finite bandwidth to a system already degraded by anisoplanatism can actually improve performance slightly, in certain cases, because highly distorted high frequency information is lost.

Research paper thumbnail of Characteristics Of Turbulence Measured On A Large Aperture

Proceedings of SPIE, Aug 10, 1988

An experiment to collect data on atmospheric turbulence has been conducted on the 107-in telescop... more An experiment to collect data on atmospheric turbulence has been conducted on the 107-in telescope located at the McDonald Observatory in Texas. The phase and the intensity of aberrated starlight have been measured over the aperture of the telescope. Simultaneous measurements of free-atmosphere seeing and local temperature differences have been made to gauge the strength of turbulence within the dome vs. turbulence in the free atmosphere.

Research paper thumbnail of Spatial–temporal-covariance-based modeling, analysis, and simulation of aero-optics wavefront aberrations

Journal of the Optical Society of America, Jun 30, 2014

We introduce a framework for modeling, analysis, and simulation of aero-optics wavefront aberrati... more We introduce a framework for modeling, analysis, and simulation of aero-optics wavefront aberrations that is based on spatial-temporal covariance matrices extracted from wavefront sensor measurements. Within this framework, we present a quasi-homogeneous structure function to analyze nonhomogeneous, mildly anisotropic spatial random processes, and we use this structure function to show that phase aberrations arising in aero-optics are, for an important range of operating parameters, locally Kolmogorov. This strongly suggests that the d 5∕3 power law for adaptive optics (AO) deformable mirror fitting error, where d denotes actuator separation, holds for certain important aero-optics scenarios. This framework also allows us to compute bounds on AO servo lag error and predictive control error. In addition, it provides us with the means to accurately simulate AO systems for the mitigation of aero-effects, and it may provide insight into underlying physical processes associated with turbulent flow. The techniques introduced here are demonstrated using data obtained from the Airborne Aero-Optics Laboratory.

Research paper thumbnail of Accommodation of speckle in object-based phasing

Journal of the Optical Society of America, Apr 19, 2012

This work addresses the physical basis of the measurement process for object-based phasing of an ... more This work addresses the physical basis of the measurement process for object-based phasing of an array of telescopes. In this regard an enhanced least-squares estimator that is capable of differentiating among three families of array aberrations in an object-based phasing system is developed. In a system of this nature the system to be phased illuminates the object of interest and the return radiation is detected. Telescope aberrations, atmospheric aberrations, and speckle-induced aberrations are all reported by the estimator to facilitate correction of telescope and atmospheric aberrations. This is accomplished by proper handling of the unobservable modes and recognizing that the five global aberrations-telescope array piston, atmospheric array piston and tilt, and speckle array piston and tilt-cannot be measured accurately so they need to be projected out of the estimated piston commands. Except for these relatively benign array aberrations, the disturbances for all three families of array aberrations are estimated exactly. An interesting feature of the speckle array aberrations is that a synthetic aperture is developed that is almost twice as large as the array of telescopes under consideration.

Research paper thumbnail of Influence of atmospheric turbulence on the propagation of quantum states of light carrying orbital angular momentum

Optics Letters, Jan 12, 2009

We analyze the influence of atmospheric turbulence on the propagation of an optical vortex beam h... more We analyze the influence of atmospheric turbulence on the propagation of an optical vortex beam having the form V͑r , ͒ = A 0 e im. The probability that a detected photon after propagating through the atmosphere has the same value of the orbital angular momentum as the launched photon is found to be given by ͗s 0 ͘ = ͓1 + ͑1.845D / r 0 ͒ 2 ͔ −1/2 , where D is the aperture diameter and r 0 is the Fried coherence diameter. These vortex beams behave very similarly to Laguerre-Gauss beams under the influence of atmospheric turbulence. These results have important implications for atmospheric laser communication systems that employ quantum encryption.

Research paper thumbnail of Target-in-the-loop phasing of a fiber laser array fed by a linewidth-broadened master oscillator

Proceedings of SPIE, May 1, 2017

In a recent paper [J. Opt. Soc. Am. A 33, 1931–1937 (2016)], the target-in-the-loop (TIL) phasing... more In a recent paper [J. Opt. Soc. Am. A 33, 1931–1937 (2016)], the target-in-the-loop (TIL) phasing of an RF-modulated or multi-phase-dithered fiber laser array, fed by a linewidth-broadened master oscillator (MO) source, was investigated. It was found that TIL phasing was possible even on a target with scattering features separated by more than the MO’s coherence length as long as the received, backscattered irradiance changed with the array’s modulation or phase dither. To simplify the problem and gain insight into how temporal coherence affects TIL phasing, speckle and atmospheric turbulence were omitted from the analysis. Here, the scenario analyzed in the prior work is generalized by including speckle and turbulence. First, the key analytical result from the prior paper is reviewed. Simulations, including speckle and turbulence, are then performed to test whether the conclusions derived from that result hold under more realistic conditions.

Research paper thumbnail of Zernike-polynomial expansion of turbulence-induced centroid anisoplanatism

Optics Letters, Jun 1, 1985

An expansion of image centroid position after propagation through atmospheric turbulence in terms... more An expansion of image centroid position after propagation through atmospheric turbulence in terms of Zernikepolynomial coefficients is shown to consist of a tilt term plus coma terms. Centroid anisoplanatism therefore arises from turbulence-induced coma distortions. By correcting for coma effects to a sufficiently high order, the deleterious effects of centroid anisoplanatism can be reduced to any desired level. The Strehl ratio is given by the asymptotic formula [1 + A (Diro) 5 / 3 1 ', where A = 0.018(1 + I)-7/3 and I is the number of coma terms corrected. Centroid anisoplanatism, described by Yura and Tavis, 1 can be a serious source of performance degradation in adaptive-optics systems designed to overcome

Research paper thumbnail of Wave-front compensation for imaging with off-axis guide stars

Journal of the Optical Society of America, 1994

Received October 1, 1992; accepted October 20, 1992 The impact of using an off-axis pulsed laser ... more Received October 1, 1992; accepted October 20, 1992 The impact of using an off-axis pulsed laser backscatter reference for compensation of an imaging system is evaluated. For low backscatter altitudes imaging is only weakly affected when the beacon is not in the same direction as ...

Research paper thumbnail of Performance of wavefront sensors in strong scintillation

Proceedings of SPIE, Feb 1, 2003

The estimation accuracy of wavefront sensors in strong scintillation is examined. Wave optical si... more The estimation accuracy of wavefront sensors in strong scintillation is examined. Wave optical simulation is used to characterize the performance of several wavefront sensors in the absence of measurement noise. The estimation accuracy of a Schack-Hartmann sensor is shown ...

Research paper thumbnail of Image-position error associated with a quadrant detector

Journal of the Optical Society of America, Jun 1, 1982

An exact expression is obtained that evaluates the error associated with angular-position measure... more An exact expression is obtained that evaluates the error associated with angular-position measurement of an incoherently illuminated object when a quadrant detector is used in the image plane of an optical system. The accuracy of such a measurement is inversely proportional to the signal-to-noise voltage ratio associated with the four quadrants summed to act as a single detector. In the particular case of a circular object, the rms angular measurement error is given by the expression os = 4r[(3/16)2 + (n/8) 2 ]" 2 (X/D)/SNRu, where n is the angular subtense of the object divided by the diffraction angle X/D, SNRU is the signal-to-noise voltage ratio, X is the wavelength of the light used, and D is the diameter of the limiting aperture in the optical system under consideration.

Research paper thumbnail of Fraunhofer Holography Applied to Particle Size Analysis a Reassessment

Optica acta, Sep 1, 1976

... results are I1=Az exp[ i 2], (4) I2= -Az exp[i2]A*(µ,v)• (5) The evaluation of I3 can be acco... more ... results are I1=Az exp[ i 2], (4) I2= -Az exp[i2]A*(µ,v)• (5) The evaluation of I3 can be accomplished by noting that °° Z k a k , as Azz ak(p - e)2l f exp[ (x - ) 2Iexp o(µ-x) 2 1 dx=exp ] ( exPI o J •(6) 2z I ) 2z 4 z+z 2(z +z)} Thus, the ...

Research paper thumbnail of Adaptive optics compensation for propagation through deep turbulence: a study of some interesting approaches

Optical Engineering, Nov 15, 2012

ABSTRACT Scintillation and anisoplanatism significantly degrade a laser transmitter system or an ... more ABSTRACT Scintillation and anisoplanatism significantly degrade a laser transmitter system or an imaging system when the optical field is required to propagate through deep turbulence. Here turbulence is defined as deep turbulence when the Rytov number is very much greater than 1 and the isoplanatic patch size is much smaller than λ/D, the diffraction limit. In this region a point beacon is of little use for imaging applications and a finite-sized beacon limits performance for both transmission and imaging because almost any finite-sized beacon is many isoplanatic patch sizes across and exhibits a significant level of beacon anisoplanatism. As a consequence, conventional adaptive optics techniques are of little value. To address this situation, five approaches are considered. These approaches include beacon deconvolution, Zernike tomography, gradient descent tomography (GDT), irradiance redistribution branch cut multiconjugate adaptive optics compensation, and minimum energy loss eigenfield propagation. GDT appears to have the most promise as it does not require a conventional wavefront sensor.

Research paper thumbnail of Synthesis of the vector resonator modes from scalar results

Optics Letters, Feb 1, 1980

A technique is presented in which the full vector solution for resonator modes is synthesized fro... more A technique is presented in which the full vector solution for resonator modes is synthesized from the known scalar solution. Second-order perturbation theory is utilized to predict the behavior of a resonator when an imperfect coating on the rear cone results in a phase shift between the s and p polarizations. The theoretical results agree well with a numerical example.

Research paper thumbnail of Rapid evaluation of d_0: the effective diameter of a laser-guide-star adaptive-optics system

Journal of the Optical Society of America, 1994

ABSTRACT

Research paper thumbnail of Turbulence-induced adaptive-optics performance degradation: evaluation in the time domain

Journal of the Optical Society of America, Mar 1, 1984

A time-domain approach has been developed that is capable of evaluating the performance of an ada... more A time-domain approach has been developed that is capable of evaluating the performance of an adaptive-optics system degraded by a wide variety of effects acting together or alone. In the study conducted here the normalized antenna gain (or Strehl ratio) is evaluated for a system degraded by turbulence, anisoplanatism, a finite servo bandwidth, and a combination of anisoplanatism and a finite servo bandwidth. A diameter dependence of these effects is established, illustrating that the degrading influence associated with a finite servo bandwidth is less severe than the degrading influence associated with anisoplanatism over a wide range of diameters. For the case of a small-diameter system degraded by anisoplanatism, system performance improves slightly when a finite servo bandwidth is introduced. correction can provide significant performance improvement. The work presented here concerning anisoplanatism is in exact agreement with Ref. 1 (although obtained by a different procedure) and illustrates the degrading influence of this effect. The last two cases studied contain new results and consider the evaluation of an adaptive-optics system degraded by a finite servo bandwidth or by a combination of aniso

Research paper thumbnail of Reconstruction and assessment of the least-squares and slope discrepancy components of the phase

Journal of the Optical Society of America, Oct 1, 2000

The concept of slope discrepancy developed in the mid-1980&amp;amp;#39;s to assess measuremen... more The concept of slope discrepancy developed in the mid-1980&amp;amp;#39;s to assess measurement noise in a wave-front sensor system is shown to have additional contributions that are due to fitting error and branch points. This understanding is facilitated by the development of a new formulation that employs Fourier techniques to decompose the measured gradient field (i.e., wave-front sensor measurements) into two components, one that is expressed as the gradient of a scalar potential and the other that is expressed as the curl of a vector potential. A key feature of the theory presented here is the fact that both components of the phase (one corresponding to each component of the gradient field) are easily reconstructable from the measured gradients. In addition, the scalar and vector potentials are both easily expressible in terms of the measured gradient field. The work concludes with a wave optics simulation example that illustrates the ease with which both components of the phase can be obtained. The results obtained illustrate that branch point effects are not significant until the Rytov number is greater than 0.2. In addition, the branch point contribution to the phase not only is reconstructed from the gradient data but is used to illustrate the significant performance improvement that results when this contribution is included in the correction applied by an adaptive optics system.

Research paper thumbnail of Holographic simulation of phase contrast (A)

Journal of the Optical Society of America, 1978

Title: Holographic simulation of phase contrast (A). Authors: Tyler, Glenn A. Publication: J. Opt... more Title: Holographic simulation of phase contrast (A). Authors: Tyler, Glenn A. Publication: J. Opt. Soc. Am., vol. 68, page 1382. Publication Date: 00/1978. Origin: OSA. Keywords: HOLOGRAPHY, MICROSCOPY. Bibliographic Code: 1978JOSA...68R1382T. Abstract. Not Available

Research paper thumbnail of Simplified anomalous dispersion model for HF chemical lasers (A)

Journal of the Optical Society of America, 1979

Title: Simplified anomalous dispersion model for HF chemical lasers (A). Authors: Tyler, Glenn A.... more Title: Simplified anomalous dispersion model for HF chemical lasers (A). Authors: Tyler, Glenn A.; Chan, Gilbert. Publication: J. Opt. Soc. Am., vol. 69, page 1458. Publication Date: 00/1979. Origin: OSA. Keywords: LASERS: HF. Bibliographic Code: 1979JOSA...69.1458T. Abstract ...