The phase diversity wavefront sensor is one of the tools used to estimate wavefront aberration, and it is often used as a wavefront sensor in adaptive optics systems. However, the performance of the traditional phase ...The phase diversity wavefront sensor is one of the tools used to estimate wavefront aberration, and it is often used as a wavefront sensor in adaptive optics systems. However, the performance of the traditional phase diversity wavefront sensor is limited by the accuracy and dynamic ranges of the intensity distribution at the focus and defocus positions of the CCD camera. In this paper, a modified phase diversity wavefront sensor based on a diffraction grating is proposed to improve the ability to measure the wavefront aberration with larger amplitude and higher spatial frequency. The basic principle and the optics construction of the proposed method are also described in detail. The noise propagation property of the proposed method is also analysed by using the numerical simulation method, and comparison between the diffraction grating phase diversity wavefront sensor and the traditional phase diversity wavefront sensor is also made. The simulation results show that the diffraction grating phase diversity wavefront sensor can obviously improve the ability to measure the wavefront aberration, especially the wavefront aberration with larger amplitude and higher spatial frequency.展开更多
A simple method to objectively and simultaneously measure eye's longitudinal and transverse chromatic aberrations was proposed.A dual-wavelength wavefront measurement system using two Hartmann-Shack wavefront sens...A simple method to objectively and simultaneously measure eye's longitudinal and transverse chromatic aberrations was proposed.A dual-wavelength wavefront measurement system using two Hartmann-Shack wavefront sensors was developed.The wavefronts of the red(639.1 nm)and near-infrared(786.0 nm)lights were measured simultaneously for different positions in the model eye.The chromatic wavefronts were converted into Zernike polynomials.The Zernike tilt cofficient(irst term)was used to calculate the transverse chromatic aberration along the ax-direction,while the Zernike defocus coefficient(fourth term)was used to calculate the longi-tudinal chromatic aberration.The measurement and simulation data were consistent.展开更多
High signal-to-noise ratio can be achieved with the electron multiplying charge-coupled-device（EMCCD） applied in the Shack–Hartmann wavefront sensor（S–H WFS） in adaptive optics（AO）.However,when the brightness ...High signal-to-noise ratio can be achieved with the electron multiplying charge-coupled-device（EMCCD） applied in the Shack–Hartmann wavefront sensor（S–H WFS） in adaptive optics（AO）.However,when the brightness of the target changes in a large scale,the fixed electron multiplying（EM） gain will not be suited to the sensing limitation.Therefore an auto-gain-control method based on the brightness of light-spots array in S–H WFS is proposed in this paper.The control value is the average of the maximum signals of every light spot in an array,which has been demonstrated to be kept stable even under the influence of some noise and turbulence,and sensitive enough to the change of target brightness.A goal value is needed in the control process and it is predetermined based on the characters of EMCCD.Simulations and experiments have demonstrated that this auto-gain-control method is valid and robust,the sensing SNR reaches the maximum for the corresponding signal level,and especially is greatly improved for those dim targets from 6 to 4 magnitude in the visual band.展开更多
Our adaptive optics system based on a non-modulation pyramid wavefront sensor is integrated into a 1.8 m astronomical telescope installed at the Yunnan Observatory in LiJiang, and the first light with high-resolution ...Our adaptive optics system based on a non-modulation pyramid wavefront sensor is integrated into a 1.8 m astronomical telescope installed at the Yunnan Observatory in LiJiang, and the first light with high-resolution imaging of an astronomical star is successfully achieved. In this Letter, the structure and performance of this system are introduced briefly, and then the observation results of star imaging are reported to show that the angular resolution of an adaptive optics system using a non-modulation pyramid wavefront sensor can approach the diffraction limit quality of a 1.8 m telescope.展开更多
Adaptive optics systems are used to compensate for wavefront distortions introduced by atmospheric turbulence.The distortions are corrected by an adaptable device,normally a deformable mirror.The control signal of the...Adaptive optics systems are used to compensate for wavefront distortions introduced by atmospheric turbulence.The distortions are corrected by an adaptable device,normally a deformable mirror.The control signal of the mirror is based on the measurement delivered by a wavefront sensor.Relevant characteristics of the wavefront sensor are the measurement accuracy,the achievable measurement speed and the robustness against scintillation.The modal holographic wavefront sensor can theoretically provide the highest bandwidth compared to other state of the art wavefront sensors and it is robust against scintillation effects.However,the measurement accuracy suffers from crosstalk effects between different aberration modes that are present in the wavefront.In this paper we evaluate whether the sensor can be used effectively in a closed-loop AO system under realistic turbulence conditions.We simulate realistic optical turbulence represented by more than 2500 aberration modes and take different signal-to-noise ratios into account.We determine the performance of a closed-loop AO system based on the holographic sensor.To counter the crosstalk effects,careful choice of the key design parameters of the sensor is necessary.Therefore,we apply an optimization method to find the best sensor design for maximizing the measurement accuracy.By modifying this method to take the changing effective turbulence conditions during closed-loop operation into account,we can improve the performance of the system,especially for demanding signal-to-noise-ratios,even more.Finally,we propose to implement multiple holographic wavefront sensors without the use of additional hardware,to perform multiple measurement at the same time.We show that the measurement accuracy of the sensor and with this the wavefront flatness can be increased significantly without reducing the bandwidth of the adaptive optics system.展开更多
In order to detect the aberration from a wide field of view（FOV） on the retina with adaptive optics, we present a multiple-object Shack-Hartmann wavefront sensor（MOSHWFS） design. The simulated results indicate tha...In order to detect the aberration from a wide field of view（FOV） on the retina with adaptive optics, we present a multiple-object Shack-Hartmann wavefront sensor（MOSHWFS） design. The simulated results indicate that the wavefront from our MOSHWFS can be reconstructed for multiple objects, and the measurement error can be less than λ∕7 with an MOSHWFS with an FOV of 6.7°, for maximum eye aberration. The experimental result with two objects indicates that the measurement error can be less than λ∕14, with the root mean square of the reference wavefront as 0.798λ and 0.895λ, respectively.展开更多
A numerical simulation model of plenoptic sensor aberration wavefront detection is established to simulate and analyze the detection performance of plenoptic sensor aberration wavefront for different turbulence intens...A numerical simulation model of plenoptic sensor aberration wavefront detection is established to simulate and analyze the detection performance of plenoptic sensor aberration wavefront for different turbulence intensities.The results show that the plenoptic sensor can achieve better distortion wavefront detection,and its wavefront detection accuracy improves with turbulence intensity.The unique optical structure design of the plenoptic sensor makes it more suitable for aberration wavefront detection in strong turbulent conditions.The wavefront detection performance of the plenoptic sensor is not only related to its wavefront reconstruction algorithm but also closely related to its structural parameter settings.The influence of structural parameters on the wavefront detection accuracy of plenoptic sensors under different turbulence intensities is simulated and analyzed.The variation law of wavefront detection accuracy and structural parameters under different turbulence intensities is summarized to provide a reference for the structural design and parameter optimization of plenoptic sensors.展开更多
A cross-scale composite wavefront measurement method based on deep learning is proposed to address local large gradient wavefront distortions from aero-optical effects.Since dynamic range and spatial resolution are us...A cross-scale composite wavefront measurement method based on deep learning is proposed to address local large gradient wavefront distortions from aero-optical effects.Since dynamic range and spatial resolution are usually a trade-off for most wavefront sensors,we propose a hybrid Shack-Hartmann-digital holographic wavefront sensing mechanism that includes a Shack-Hartmann wavefront sensor(SHWFS)and off-axis digital holography(OADH).Using the hybrid wavefront sensing mechanism and the data processing method,the reconstructed wavefront of SHWFS and the wrapped phase of OADH are obtained separately.A multi-input efficient network cal ed the multi-system wavefront measurement-net(MSWM-Net)with an attention mechanism is introduced to map the reconstructed wavefront of SHWFS and the wrapped phase of the OADH to the precise wavefront.Numerical simulations and comparisons with the deep learning phase unwrapping(DLPU)-model-based phase unwrapping method and classical phase unwrapping technique demonstrate that this method resolves the chal enge of mismatched data scales across the two measurement systems,enabling rapid and high-precision wavefront sensing.展开更多
Objective The widespread adoption of portable fundus cameras for primary care and community screening is hindered by limitations in current autofocus(AF)technologies.Image-based methods relying on sharpness evaluation...Objective The widespread adoption of portable fundus cameras for primary care and community screening is hindered by limitations in current autofocus(AF)technologies.Image-based methods relying on sharpness evaluation require iterative searches,resulting in slow convergence,while projection-based techniques are susceptible to optical artifacts and calibration errors.To address these challenges,this study introduces a novel AF system based on direct wavefront sensing,designed to deliver simultaneous high speed,high precision,and operational robustness within the compact form factor essential for portable ophthalmic devices.Methods Our approach fundamentally reimagines the AF process by directly measuring the ocular wavefront aberration.We developed a custom portable fundus camera integrating a miniaturized Shack-Hartmann wavefront sensor(SHWS)into the optical path.An 850 nm laser diode projects a point source onto the retina via oblique illumination to minimize corneal reflections.Light scattered from this spot carries the eye’s refractive error through the imaging optics and is directed to the SHWS,positioned at a plane optically conjugate to the primary color CMOS imaging sensor.A microlens array within the SHWS samples the incident wavefront,generating a pattern of focal spots on a CCD.Real-time centroid analysis of these spots provides a map of local wavefront slopes.These measurements are processed through a singular value decomposition(SVD)algorithm to fit a Zernike polynomial basis set,enabling real-time reconstruction of the wavefront phase.The defocus component(S)is extracted from the second-order Zernike coefficients,providing a direct,quantitative measure of the refractive error in diopters.This value serves as a precise error signal in a closed-loop control system,which commands a voice-coil actuated focusing lens to its null position in a single,deterministic step,eliminating the need for iterative search algorithms.Results Comprehensive evaluation demonstrated the system’s high performance.Testing on a calibrated model eye(OEMI-7)established a highly linear relationship between the computed defocus S and the focusing lens position across a±20 Diopter(D)compensation range,achievable within a 5 mm mechanical travel.The system achieved a focusing precision of 0.08 D,corresponding to an 18-fold improvement over a conventional projection spot-size method tested under identical conditions.The total focus acquisition time,encompassing wavefront measurement,computation,and lens actuation,averaged under 0.5 s.Clinical validation with 25 human volunteers(50 eyes,refractive range-15 D to+10 D)confirmed practical efficacy.The wavefront-sensing AF succeeded in 92%of attempts with a mean time of 0.5 s,substantially outperforming a projection-based benchmark which achieved only a 32%success rate with an average time of 4.25 s.The system provided instantaneous directional guidance and maintained stability during minor ocular movements.Objective assessment of image quality,via amplitude contrast of retinal vasculature,showed consistent and significant enhancement following AF correction across the entire tested diopter range.Conclusion This work successfully implements and validates a direct wavefront-sensing autofocus paradigm for portable fundus cameras.By directly quantifying and compensating for the optical defocus aberration,this method bypasses the fundamental limitations of image-processing and projection-based techniques,enabling rapid,precise,and deterministic diopter compensation.The developed system delivers an exceptional combination of a wide operational range(±20 D),high accuracy(0.08 D),fast convergence(0.5 s),and a compact physical footprint.This technology provides a practical and highperformance focusing solution capable of enhancing the reliability,throughput,and diagnostic utility of portable retinal imaging in large-scale screening applications.Future efforts will be directed towards system cost optimization and performance adaptation for diverse ocular conditions.展开更多
文摘The phase diversity wavefront sensor is one of the tools used to estimate wavefront aberration, and it is often used as a wavefront sensor in adaptive optics systems. However, the performance of the traditional phase diversity wavefront sensor is limited by the accuracy and dynamic ranges of the intensity distribution at the focus and defocus positions of the CCD camera. In this paper, a modified phase diversity wavefront sensor based on a diffraction grating is proposed to improve the ability to measure the wavefront aberration with larger amplitude and higher spatial frequency. The basic principle and the optics construction of the proposed method are also described in detail. The noise propagation property of the proposed method is also analysed by using the numerical simulation method, and comparison between the diffraction grating phase diversity wavefront sensor and the traditional phase diversity wavefront sensor is also made. The simulation results show that the diffraction grating phase diversity wavefront sensor can obviously improve the ability to measure the wavefront aberration, especially the wavefront aberration with larger amplitude and higher spatial frequency.
基金National Science Foundation of China(NSFC)(61378064)the National High Technology Research and Development Program of China(2015AA020510).
文摘A simple method to objectively and simultaneously measure eye's longitudinal and transverse chromatic aberrations was proposed.A dual-wavelength wavefront measurement system using two Hartmann-Shack wavefront sensors was developed.The wavefronts of the red(639.1 nm)and near-infrared(786.0 nm)lights were measured simultaneously for different positions in the model eye.The chromatic wavefronts were converted into Zernike polynomials.The Zernike tilt cofficient(irst term)was used to calculate the transverse chromatic aberration along the ax-direction,while the Zernike defocus coefficient(fourth term)was used to calculate the longi-tudinal chromatic aberration.The measurement and simulation data were consistent.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11174274,61205021,and 61405194)the State Key Laboratory of Applied Optics,Changchun Institute of Optics,Fine Mechanics and Physics,Chinese Academy of Sciences
文摘High signal-to-noise ratio can be achieved with the electron multiplying charge-coupled-device（EMCCD） applied in the Shack–Hartmann wavefront sensor（S–H WFS） in adaptive optics（AO）.However,when the brightness of the target changes in a large scale,the fixed electron multiplying（EM） gain will not be suited to the sensing limitation.Therefore an auto-gain-control method based on the brightness of light-spots array in S–H WFS is proposed in this paper.The control value is the average of the maximum signals of every light spot in an array,which has been demonstrated to be kept stable even under the influence of some noise and turbulence,and sensitive enough to the change of target brightness.A goal value is needed in the control process and it is predetermined based on the characters of EMCCD.Simulations and experiments have demonstrated that this auto-gain-control method is valid and robust,the sensing SNR reaches the maximum for the corresponding signal level,and especially is greatly improved for those dim targets from 6 to 4 magnitude in the visual band.
基金supported by the National Natural Science Foundation of China under Grant No.61008038
文摘Our adaptive optics system based on a non-modulation pyramid wavefront sensor is integrated into a 1.8 m astronomical telescope installed at the Yunnan Observatory in LiJiang, and the first light with high-resolution imaging of an astronomical star is successfully achieved. In this Letter, the structure and performance of this system are introduced briefly, and then the observation results of star imaging are reported to show that the angular resolution of an adaptive optics system using a non-modulation pyramid wavefront sensor can approach the diffraction limit quality of a 1.8 m telescope.
基金This work was sponsored by WTD 91(Technical Center of Weapons and Ammunition)of the Federal Defence Forces of Germany-Bundeswehr in the project ABU-SLSby the Office of Naval Research Global under award no.N62909-17-1-2037.
文摘Adaptive optics systems are used to compensate for wavefront distortions introduced by atmospheric turbulence.The distortions are corrected by an adaptable device,normally a deformable mirror.The control signal of the mirror is based on the measurement delivered by a wavefront sensor.Relevant characteristics of the wavefront sensor are the measurement accuracy,the achievable measurement speed and the robustness against scintillation.The modal holographic wavefront sensor can theoretically provide the highest bandwidth compared to other state of the art wavefront sensors and it is robust against scintillation effects.However,the measurement accuracy suffers from crosstalk effects between different aberration modes that are present in the wavefront.In this paper we evaluate whether the sensor can be used effectively in a closed-loop AO system under realistic turbulence conditions.We simulate realistic optical turbulence represented by more than 2500 aberration modes and take different signal-to-noise ratios into account.We determine the performance of a closed-loop AO system based on the holographic sensor.To counter the crosstalk effects,careful choice of the key design parameters of the sensor is necessary.Therefore,we apply an optimization method to find the best sensor design for maximizing the measurement accuracy.By modifying this method to take the changing effective turbulence conditions during closed-loop operation into account,we can improve the performance of the system,especially for demanding signal-to-noise-ratios,even more.Finally,we propose to implement multiple holographic wavefront sensors without the use of additional hardware,to perform multiple measurement at the same time.We show that the measurement accuracy of the sensor and with this the wavefront flatness can be increased significantly without reducing the bandwidth of the adaptive optics system.
基金supported by the National Natural Science Foundation of China(Nos.11174274,11174279,61205021,11204299,61475152,and 61405194)the State Key Laboratory of Applied Optics,Changchun Institute of Optics,Fine Mechanics and Physics,Chinese Academy of Sciences
文摘In order to detect the aberration from a wide field of view（FOV） on the retina with adaptive optics, we present a multiple-object Shack-Hartmann wavefront sensor（MOSHWFS） design. The simulated results indicate that the wavefront from our MOSHWFS can be reconstructed for multiple objects, and the measurement error can be less than λ∕7 with an MOSHWFS with an FOV of 6.7°, for maximum eye aberration. The experimental result with two objects indicates that the measurement error can be less than λ∕14, with the root mean square of the reference wavefront as 0.798λ and 0.895λ, respectively.
基金the National Natural Science Foundation of China(No.61605223)the Strategic Priority Research Program of Chinese Academy of Sciences(No.614A010717)the Director Fund of Advanced Laser Technology Laboratory of Anhui Province(No.AHL2021ZR06)。
文摘A numerical simulation model of plenoptic sensor aberration wavefront detection is established to simulate and analyze the detection performance of plenoptic sensor aberration wavefront for different turbulence intensities.The results show that the plenoptic sensor can achieve better distortion wavefront detection,and its wavefront detection accuracy improves with turbulence intensity.The unique optical structure design of the plenoptic sensor makes it more suitable for aberration wavefront detection in strong turbulent conditions.The wavefront detection performance of the plenoptic sensor is not only related to its wavefront reconstruction algorithm but also closely related to its structural parameter settings.The influence of structural parameters on the wavefront detection accuracy of plenoptic sensors under different turbulence intensities is simulated and analyzed.The variation law of wavefront detection accuracy and structural parameters under different turbulence intensities is summarized to provide a reference for the structural design and parameter optimization of plenoptic sensors.
基金supported by the National Natural Science Foundation of China(No.62305343)the Fund of the National Key Laboratory of Adaptive Optics(No.FNLAO-24-MS-S07)。
文摘A cross-scale composite wavefront measurement method based on deep learning is proposed to address local large gradient wavefront distortions from aero-optical effects.Since dynamic range and spatial resolution are usually a trade-off for most wavefront sensors,we propose a hybrid Shack-Hartmann-digital holographic wavefront sensing mechanism that includes a Shack-Hartmann wavefront sensor(SHWFS)and off-axis digital holography(OADH).Using the hybrid wavefront sensing mechanism and the data processing method,the reconstructed wavefront of SHWFS and the wrapped phase of OADH are obtained separately.A multi-input efficient network cal ed the multi-system wavefront measurement-net(MSWM-Net)with an attention mechanism is introduced to map the reconstructed wavefront of SHWFS and the wrapped phase of the OADH to the precise wavefront.Numerical simulations and comparisons with the deep learning phase unwrapping(DLPU)-model-based phase unwrapping method and classical phase unwrapping technique demonstrate that this method resolves the chal enge of mismatched data scales across the two measurement systems,enabling rapid and high-precision wavefront sensing.
文摘Objective The widespread adoption of portable fundus cameras for primary care and community screening is hindered by limitations in current autofocus(AF)technologies.Image-based methods relying on sharpness evaluation require iterative searches,resulting in slow convergence,while projection-based techniques are susceptible to optical artifacts and calibration errors.To address these challenges,this study introduces a novel AF system based on direct wavefront sensing,designed to deliver simultaneous high speed,high precision,and operational robustness within the compact form factor essential for portable ophthalmic devices.Methods Our approach fundamentally reimagines the AF process by directly measuring the ocular wavefront aberration.We developed a custom portable fundus camera integrating a miniaturized Shack-Hartmann wavefront sensor(SHWS)into the optical path.An 850 nm laser diode projects a point source onto the retina via oblique illumination to minimize corneal reflections.Light scattered from this spot carries the eye’s refractive error through the imaging optics and is directed to the SHWS,positioned at a plane optically conjugate to the primary color CMOS imaging sensor.A microlens array within the SHWS samples the incident wavefront,generating a pattern of focal spots on a CCD.Real-time centroid analysis of these spots provides a map of local wavefront slopes.These measurements are processed through a singular value decomposition(SVD)algorithm to fit a Zernike polynomial basis set,enabling real-time reconstruction of the wavefront phase.The defocus component(S)is extracted from the second-order Zernike coefficients,providing a direct,quantitative measure of the refractive error in diopters.This value serves as a precise error signal in a closed-loop control system,which commands a voice-coil actuated focusing lens to its null position in a single,deterministic step,eliminating the need for iterative search algorithms.Results Comprehensive evaluation demonstrated the system’s high performance.Testing on a calibrated model eye(OEMI-7)established a highly linear relationship between the computed defocus S and the focusing lens position across a±20 Diopter(D)compensation range,achievable within a 5 mm mechanical travel.The system achieved a focusing precision of 0.08 D,corresponding to an 18-fold improvement over a conventional projection spot-size method tested under identical conditions.The total focus acquisition time,encompassing wavefront measurement,computation,and lens actuation,averaged under 0.5 s.Clinical validation with 25 human volunteers(50 eyes,refractive range-15 D to+10 D)confirmed practical efficacy.The wavefront-sensing AF succeeded in 92%of attempts with a mean time of 0.5 s,substantially outperforming a projection-based benchmark which achieved only a 32%success rate with an average time of 4.25 s.The system provided instantaneous directional guidance and maintained stability during minor ocular movements.Objective assessment of image quality,via amplitude contrast of retinal vasculature,showed consistent and significant enhancement following AF correction across the entire tested diopter range.Conclusion This work successfully implements and validates a direct wavefront-sensing autofocus paradigm for portable fundus cameras.By directly quantifying and compensating for the optical defocus aberration,this method bypasses the fundamental limitations of image-processing and projection-based techniques,enabling rapid,precise,and deterministic diopter compensation.The developed system delivers an exceptional combination of a wide operational range(±20 D),high accuracy(0.08 D),fast convergence(0.5 s),and a compact physical footprint.This technology provides a practical and highperformance focusing solution capable of enhancing the reliability,throughput,and diagnostic utility of portable retinal imaging in large-scale screening applications.Future efforts will be directed towards system cost optimization and performance adaptation for diverse ocular conditions.
