Aberration Measurement Method Research Articles

Frequency-multiplexed aberration measurement for confocal microscopy

In single-photon confocal fluorescence microscopy, optical aberration affects both excitation and detection light paths, thus can severely degrade image quality. We incorporated an adaptive optics (AO) module into a confocal microscope and used a frequency-multiplexed aberration measurement method to measure and correct sample-induced aberration. We demonstrated that this method can measure aberration using signals from features of different sizes and recover diffraction-limited imaging performance. Applying our AO confocal microscope to imaging through and within living zebrafish larvae, as well as in the mouse brain in vivo, we showed that aberration correction can substantially improve confocal image brightness, resolution, and contrast.

Hartmanngram structural information-assisted aberration measurement for a 4-meter-thin primary mirror with a large dynamic range

Deformations of the primary mirror will significantly reduce the capability of a large telescope. Moreover, the aberration introduced by the deformations usually exceeds the dynamic range of a traditional wavefront sensor such as a classical Shack–Hartmann wavefront sensor (SHWFS). Although some methods have been proposed to improve the dynamic range of an SHWFS, these methods have their own limitations for the 4-meter-thin primary mirror (FMTPM) platform. In this paper, we introduce an aberration measurement method based on Hartmanngram structural information for the FMTPM. The simulation results show that the proposed method can significantly increase the dynamic range of an SHWFS compared with traditional methods and be robust to noise and spot missing situations for large aberration conditions. In addition, experiments with the FMTPM showed that for Beta Aurigae (HIP28360), active compensation based on the estimated aberration significantly improved the far-field spot-encircled energy. The peak value of the spot also increased about three times, indicating the aberration measurement accuracy of the proposed method.

基于差分空间像主成分分析的偏振像差检测方法

基于差分空间像主成分分析的偏振像差检测方法

High-order wavefront aberration measurement method for hyper-NA lithographic projection lens based on a binary target and rotated regression matrix

Abstract A high-order wavefront aberration (HWA) measurement method for a hyper-NA lithographic projection lens based on a binary target with eight directions and rotated regression matrix is proposed. A linear model between the aerial image intensity distribution of the hyper-NA lithographic projection lens and HWAs is built by principal component analysis and regression matrix rotation. Compared to the conventional method using a binary target with six directions, the proposed method improves the efficiency of pupil sampling, increases the modeling speed, extends the measuring range of the wavefront aberrations, and detects the HWAs of the hyper-NA lithographic projection lens accurately. The lithographic simulator PROLITH is used to validate the accuracies of the HWA measurement and analyze the impact of the illumination types of source on the accuracy of the HWA measurement, as well as the polarization rotation of illumination, the sample interval of the aerial images, and the manufacturing error of the test target. The results show that the proposed method retrieves 60 terms of Zernike coefficients ( Z 5 – Z 64 ) with measurement accuracy greater than 1.03 × 10−3 λ .

Wavefront aberration measurement method for a hyper-NA lithographic projection lens based on principal component analysis of an aerial image.

A wavefront aberration measurement method for a hyper-NA lithographic projection lens by use of an aerial image based on principal component analysis is proposed. Aerial images of the hyper-NA lithographic projection lens are expressed accurately by using polarized light and a vector imaging model, as well as by considering the polarization properties. As a result, the wavefront aberrations of the hyper-NA lithographic projection lens are measured accurately. The lithographic simulator PROLITH is used to validate the accuracies of the wavefront aberration measurement and analyze the impact of the polarization rotation of illumination on the accuracy of the wavefront aberration measurement, as well as the degree of polarized light and the sample interval of aerial images. The result shows that the proposed method can retrieve 33 terms of Zernike coefficients (Z5-Z37) with a maximum error of less than 0.00085λ.

In situaberration measurement method using a phase-shift ring mask

An in situ aberration measurement method using a phase-shift ring mask is proposed for a lithographic projection lens whose numerical aperture is below 0.8. In this method, two-dimensional phase-shift rings are designed as the measurement mask. A linear relationship model between the intensity distribution of the lateral aerial image and the aberrations is built by principal component analysis and multivariate linear regression analyses. Compared with the principal component analysis of the aerial images (AMAI-PCA) method, in which a binary mask and through-focus aerial images are used for aberration extraction, the aerial images of the phase-shift ring mask contain more useful information, providing the possibility to eliminate the crosstalk between different kinds of aberrations. Therefore, the accuracy of the aberration measurement is improved. Simulations with the lithography simulator Dr.LiTHO showed that the accuracy is improved by 15% and five more Zernike aberrations can be measured compared with the standard AMAI-PCA. Moreover, the proposed method requires less measured aerial images and is faster than the AMAI-PCA.

Multiplexed aberration measurement for deep tissue imaging in vivo.

We describe a multiplexed aberration measurement method that modulates the intensity or phase of light rays at multiple pupil segments in parallel to determine their phase gradients. Applicable to fluorescent-protein-labeled structures of arbitrary complexity, it allows us to obtain diffraction-limited resolution in various samples in vivo. For the strongly scattering mouse brain, a single aberration correction improves structural and functional imaging of fine neuronal processes over a large imaging volume.

Measurement of lens aberration based on vector imaging theory

Current aerial image based aberration measurement methods are all derived from the scalar imaging theory which is not applicable to hyper-NA lithography. Here we propose an aberration measurement method for the lithography system with an arbitrary NA based on the rigorous vector imaging theory. The retrieval error of the proposed method is clearly demonstrated by comparing with the method based on the scalar imaging theory for an immersion NA 1.35 projector using numerical results. The results show that the maximal retrieval error of our method is below 0:5mλ, while that of previous method is above 4mλ. In addition, the effect of practical aerial image metrology accuracy on the retrieval accuracy of proposed technique is analyzed. The results obtained demonstrate that the retrieval accuracy of our method is greatly improved, and the proposed technique is applicable to the retrieval of the wavefront aberration of a projector with hyper-NA.

Information fusion method for ocular aberrations measurement based on subjective visual compensation

The human eye is an imperfect refractive system which not only has defocus and astigmatism, but also has spherical aberration, coma and anomalistic high-order aberrations, all of which have certain influence on the imaging quality of retina. What's worse, aberration is further enlarged as a result of mydriasis in dark field and weak light, thus making the vision performance of human eyes far below diffraction limitation. Further research revealed that human eye visual imaging is not only connected with refractive system, but also is closely related to the subjective judgment of human brain and the process of neural system. In order to overcome the deficiencies, wave-front aberration measurement method and system that has subjective visual compensation is proposed and conducted in combination with objective measurement, which ensures more accurate and realistic measuring results. The experimental data revealed that wave-front aberration obtained from subjective visual compensation measuring method is smaller than objective measurement, which is the result of subjects’ adaptive correction when watching sighting targets. In addition, when subjects are watching different sighting targets, the fluctuation value of wavefront aberration is small. Therefore, it is concluded that subjective visual compensation measuring method contributes to aberration measuring improvement and obtains results match with the realistic state by taking into consideration the actual condition of human eyes when watching targets. Hopefully, these discoveries will be of positive and beneficial value to the determination of human eye aberration treatment.

Ocular Aberrations Measurement Combined with Subjective Visual Compensation

Objective: The human eye is an imperfect refractive system which not only has defocus and astigmatism, but also spherical aberration, coma and anomalistic high-order aberrations, all of which have influence on the imaging quality of retina. Further research revealed that human eye visual imaging is not only connected with refractive system, but also is closely related to the subjective judgment of human brain and the process of neural system. Method: Wave-front aberration measurement method and its measuring system which have subjective visual compensation are proposed and conducted in combination with objective measurement, which ensure more accurate and realistic measuring results. Result: Wave-front aberration obtained from subjective visual compensation measuring method turned out to be smaller than objective measurement, which is the result of subjects’ adaptive correction when watching sighting targets. In addition, when subjects are watching different sighting targets, the fluctuation value of wave front aberration is small. Conclusion: Subjective visual compensation measuring method takes into consideration the actual condition of human eyes when watching targets which contributes to aberration measuring improvement and obtains results that match realistic state, all of which are of positive and beneficial value to the determination of human eye aberration treatment.