Modulation Transfer Function Values Research Articles

The Impact of Back Optic Zone Design in Orthokeratology on Visual Performance.

To evaluate the visual performance in adolescents undergoing orthokeratology (OrthoK) treatment with two different optical zone diameters (OZDs). This randomized, double-masked, self-controlled prospective study was conducted at Tianjin Eye Hospital (Tianjin, China) in June 2022. Thirty-six eligible schoolchildren were enrolled and fitted with corneal refractive therapy lenses with two sizes of OZDs (5 mm [5OZ] and 6 mm [6OZ]). Each participant was randomized to wear the 5OZ in one eye and the 6OZ in the contralateral eye. Subjective visual quality was assessed using visual acuity, refraction, contrast sensitivity function, and visual symptoms, and the objective optical quality was assessed using ocular higher order aberrations (HOAs) and modulation transfer function (MTF). Thirty-five myopic children completed a 1-month follow-up visit. The 5OZ lens induced significantly smaller treatment zone diameters than the 6OZ lens (P < 0.001). Subjective visual quality did not differ significantly between the two groups. Compared to baseline, aberrations of Z40, coma-like, spherical-like, and total HOAs in both groups increased significantly (P < 0.05). For the 3-mm pupils, spherical aberration in the 5OZ group was significantly higher than that in the 6OZ group (P < 0.05). The MTF value of the 6OZ group was significantly higher than that of 5OZ group for 0.3 and 1.5 cycles per degree for the 3-mm pupils (P = 0.006 and P = 0.026, respectively). However, HOAs or MTF did not differ significantly between the two groups for the 5-mm pupils. The difference induced by varying OZD was significant only in the smaller pupil condition. The selection of OZD in OrthoK designs in real-world patient management should be done while considering individual pupil size. This study revealed that the objective visual quality of small OZD lenses was only slightly affected for the small pupil size.

Long-term assessment and analysis of the radiometric quality of standard data products for Chinese Gaofen-1/2/6/7 optical remote sensing satellites

The first Chinese Gaofen (GF) remote sensing satellite was launched in August 2013 and has been in orbit for more than 10 years, providing a rich variety of image product data for remote sensing applications in various industries, with other remote sensing satellites of the GF series. To ensure the reliability of the information generated via remote sensing applications, all remote sensing images must undergo systematic quality evaluation. The quality of GF satellites is evaluated almost comprehensively during in-orbit testing at the early stage after launch; however, the remaining evaluations of product quality including geometric or radiometric calibrations are performed only annually. Thus, long-term systematic image quality evaluations are lacking, and the quality level and long-term change trends of the image products are unknown. These deficits have introduced uncertainty in the application of these products. This study aimed to establish a radiometric quality evaluation index framework for GF satellites to comprehensively measure the radiometric quality of GF image products. Multiple types of sample data, such as uniform field, knife-edge target, and radiometric calibration field data with different reflectance features, were acquired globally. Four core indexes, namely, the relative radiometric correction accuracy (RRCA), absolute radiometric correction accuracy (ARCA), modulation transfer function (MTF), and signal-to-noise ratio (SNR), were used to analyze and evaluate the long-term radiometric quality of the images from four GF optical remote sensing satellites: GF1, GF2, GF6, and GF7. The four GF satellites had high SNR and RRCA but low dynamic MTF and variable ARCA for different reflectance features. For example, the average SNRs for the four satellites reached 42.66, 43.91, 44.33, and 47.46 dB; the average RRCA (@root-mean-square errors) values reached 1.6%, 1.0%, 1.6%, and 0.1%; the average MTF values (at Nyquist frequency) of the panchromatic bands were only 0.15, 0.12, 0.07 and 0.04; and the difference in ARCA for different reflectance targets was approximately 10%. In the long time series, the SNRs for each sensor of the four GF satellites were high and stable for high-reflectance features, whereas the RCA and SNR values for low-reflectance features and the MTF of the sensors fluctuated in a cyclic manner. Meanwhile, large dynamic fluctuations and episodic image quality problems occurred at certain local time points, which must be considered during practical applications. The findings presented here will lay a foundation for the in-depth application of GF images.

Comparative visual outcomes of the first versus second eye following small-incision lenticule extraction (SMILE)

BackgroundThis study aimed to compare the visual outcomes of the first operated eyes with those of the second operated eyes following small-incision lenticule extraction (SMILE).MethodsA total of 202 patients (404 eyes) underwent SMILE using the tear film mark centration method for myopia and myopic astigmatism correction. Baseline characteristics, objective optical quality, decentered displacement, induced corneal aberrations, and modulation transfer function (MTF) values were assessed. Linear regression analyzed the relationship between decentration and visual quality parameters, including corneal aberrations and MTF values.ResultsNo significant difference was observed in objective visual quality, efficacy, and safety indexes between the two groups (all P > 0.05). The average decentered displacement for the first and second surgical eyes was 0.278 ± 0.17 mm and 0.315 ± 0.15 mm, respectively (P = 0.002). The horizontal coma in the first surgical eyes were notably lower than in the second (P = 0.000). MTF values at spatial frequencies of 5, 10, 15, and 20 cycles/degree (c/d) were higher in the first surgical eyes compared to the second (all P < 0.05). Linear regression indicated that high-order aberrations (HOAs), root mean square (RMS) coma, spherical aberration, horizontal coma, vertical coma, and eccentric displacement were all linearly correlated. Furthermore, MTF values exhibited a linear relationship with eccentric displacement across these spatial frequencies.ConclusionsThere was no discernible difference in visual acuity, efficacy, or safety between the two operated eyes. Nonetheless, the first operated eyes exhibited reduced decentered displacement and demonstrated superior outcomes in terms of horizontal coma and MTF values compared to the second operated eyes following SMILE. The variations in visual quality parameters were linearly correlated with decentered displacement.

Performance evaluation of six digital mammography systems

The strong advance in digital mammography as a tool for breast cancer screening requires that the new systems be characterized. Quality control protocols describe the methodology to evaluate systems performance. Detective quantum efficiency (DQE) is the most suitable parameter for describing the imaging performance of an X-ray imaging device. The objective of this study was to characterize in terms of DQE six digital mammography systems, at different detector air kerma (DAK) levels for a variety of beam qualities. A Carestream EHR-M3 CR detector, a small field digital mammography system Siemens Opdima, and full field digital mammography systems Planmed Clarity, GE Essential, GE Pristina and GE Crystal Nova were characterized using the European Guidelines protocol. Modulation transfer function (MTF), normalized noise power spectrum (NNPS) and DQE were determined, for an extended detector air kerma range. Attenuated beam qualities (obtained by adding 2 mm Al to the corresponding beam qualities) used were 28 kV with anode/filter combination Mo/Mo for the EHR-M3, Opdima, Essential and Pristina systems; 28 kV W/Ag for the Clarity; 28 kV W/Rh for the Crystal Nova; 28 kV Mo/Rh for the EHR-M3; and 34 kV Rh/Ag for the Pristina. Two groups were identified in MTF analysis, and the group composed of Clarity, Opdima and Essential presented the highest MTF values. In NNPS analysis, three main groups were identified, in which the systems Crystal Nova and Essential presented lower and higher NNPS, respectively. Crystal Nova system also exhibited higher DQE values for low spatial frequencies, while Opdima and Clarity presented higher DQE values for medium to high spatial frequency. Agreement with data from literature indicates that the systems evaluated are operating under typical conditions. Evidence of improvement in detectors performance was found.

Blue-Light Filtering Monofocal Intraocular Lenses: A Study on Optical Function and Tolerance to Misalignment.

To investigate the optical performance and tolerance to misalignment of blue-light filtering monofocal intraocular lenses (IOLs). The optical properties of two monofocal IOLs featuring yellow chromophores, CT Lucia 621 PY (Carl Zeiss Meditec AG) and Clareon CNA0T0 (Alcon Laboratories, Inc), were assessed in monochromatic and polychromatic light while introducing spherical aberration (SA). Optical quality metrics derived from the modulation transfer function were assessed after optimal IOL centration at 3- and 4.5-mm pupils. In addition, each IOL's tolerance to misalignment was examined by inducing up to 1 mm of decentration and the effect of tilting it by 5 degrees at 3 mm. The IOLs' resolution and contrast, while tested using a 3-mm aperture and an SA-neutral corneal model, indicated the CT Lucia 621 PY had a slightly higher modulation transfer function (MTF) at 50 lp/mm than the CNA0T0 under monochromatic conditions (0.77 vs 0.69). On introducing SA with (0.49 vs 0.40) and without (0.75 vs. 0.70) chromatic aberration, the CT Lucia 621 PY maintained its minimally better performance. When assessed with a 4.5-mm aperture in monochromatic light, the CT Lucia 621 PY displayed improved MTF with aberration-free cornea (0.71 vs 0.40) but performed worse after introducing SA (0.44 vs 0.62). However, both lenses achieved comparable MTF values under spherical and chromatic aberrations (0.28 vs 0.27). The IOL misalignment test revealed a better tolerance to tilt and decentration of the CT Lucia 621 PY across all conditions. The CT Lucia 621 PY and CNA0T0 showed similar optical quality in different situations, with equal simulated distance visual acuity for both models. However, the CT Lucia 621 PY's aspheric design offers an advantage when dealing with often imperfect physiological conditions, displaying a more robust performance under tilt and decentration. [J Refract Surg. 2024;40(2):e79-e88.].

Performance evaluation of a zoom iris recognition system using Q-type aspherical design.

Based on a Q-type aspheric surface, a wide working distance zoom iris recognition lens is designed. The lens has an aperture of 2.0 and a working distance of 200-1200mm. The design results show that the modulation transfer function values of each field at the cutoff frequency are greater than 0.3 and the optical distortion is less than 1.1%. With the same structure and parameters, the performance of two optical systems using Q-type aspherical and even power series aspherical are analyzed. The Q-type non-spherical aberration correction is better.

In-vitro assessment of a novel intraocular lens made of crosslinked polyisobutylene

PurposeTo describe and analyse the particularities of the material and the optical quality of the first intraocular lens (IOL) (Eyedeal® lens) made of crosslinked polyisobutylene (xPIB). MethodsWe assessed the material quality using an accelerated ageing process (to provoke glistenings) and compared values with a control, AcrySof® lens. Using the sessile drop method, the contact angle of the new IOL was measured. Images of the lens surface were recorded by scanning electron microscopy (SEM). Optical quality was assessed by measuring the labeled power and modulation transfer function (MTF) using standard metrology equipment (OptiSpheric IOL PRO2). ResultsThe Eyedeal® lens had an average glistening density result of 7.46 ± 3.78 MV/mm2 compared to the control AcrySof® whose glistenings number was 142.42 ± 72.47 MV/mm2. The contact angle was 97.2° whereas the angle of AcrySof material is between 73.3 ± 2.4° and 84.4 ± 0.1°. Using SEM, Eyedeal® lenses were examined and all appeared to be comparable to modern IOLs made of acrylic materials. The power and MTF values were normal and conformed to ISO standards. ConclusionsIn the laboratory, the new Eyedeal® lens showed equivalence to current hydrophobic- or hydrophilic-acrylic lens models. It showed superiority in its glistening density result compared to the control lens.

AUTOMATED DESIGN OF KORSCH ORTHOSCOPIC ASPHERICAL MIRROR TELESCOPES FOR NANOSATELLITES

This study presents the results of an automated parametric synthesis of a series of orthoscopic aspheric optical systems of mirror telescopes with different focal lengths, built according to the Korsch scheme. In order to ensure compactness of the design, these systems consist of three second-order aspheric mirrors and three folded flat mirrors. The obtained optical systems have a focal length ranging from 480 mm to 960 mm, an angular field of view ranging from 1.2° to 2.4°, an aperture number ranging from 6 to 12, an entrance aperture with a diameter of 80 mm, and an axial length of no more than 170 mm, which is within the dimensions of a 2U CubeSat. The maximum linear size of the image detector's sensitive area is 20 mm in all considered systems. The mirror telescopes do not have chromatic aberrations, enabling the capture of images within the visible spectrum and multiple infrared sub-bands. The provided aberration analysis demonstrates the high image quality of the considered optical systems. Specifically, for a wavelength of 0.546 μm, thediffraction modulation transfer function values both in the meridional and sagittal planes across the entire field exceed 0.53 for a spatial frequency of 30 mm-1, and 0.3 for a spatial frequency of 50 mm-1. The maximum relative distortion in the designed systems is 0.005%, corresponding to an absolute displacement of 0.5 μm. The presented telescopes are capable of covering an observation band of Earth's surface with linear dimensions ranging from 12.6 km to 25.1 km when a satellite track height is 600 km. By applying multi-element image detectors with a pixel size of 5 μm and achieving diffraction-limited image quality in the optical systems, both the geometric and diffraction resolution limits on Earth's surface will not exceed 10 m.

Longitudinal spatial coherence of computational ghost imaging through atmospheric turbulence

The resolution and imaging quality of ghost imaging is determined by the longitudinal spatial coherence (LSC) of speckle beams on the signal and reference arms. Based on the cross-correlation function, long-exposure and short-exposure computational ghost imaging through turbulent atmosphere is investigated analytically and numerically in the framework of the traditional imaging theory. According to the point spread function (PSF), the modulation transfer function (MTF) is derived, both of which are utilized to evaluate imaging resolution and imaging quality of computational ghost imaging (CGI), respectively. By simulating long-exposure and short-exposure ghost imaging through atmospheric turbulence, the comprehensive effects of atmospheric turbulence and beam initial parameters on the complex degree of coherence (CDC), PSF, and MTF are studied, respectively. It is found that the degradation of LSC between the two planes on the reference and signal path implies a narrower PSF and increased MTF values, which represent the better resolution and imaging quality. Thus, reducing the atmospheric turbulence strength, the speckle particle size, the wavelength and the propagation distance, and increasing the source size contribute to improving resolution and image quality of CGI because of the degradation of LSC. Furthermore, short-exposure CGI can provide imaging performance superior to long-exposure CGI in terms of resolution and imaging quality due to the decrease of LSC.

Athermal panoramic annular lens design with a thermal analysis method

An athermal 360∘×(30∘−100∘) and F/3.5 panoramic annular lens (PAL) system is designed. Through the optical mechanical thermal analysis results based on finite element analysis (FEA), it is expected that the system will have excellent performance under extreme temperature fluctuations. Simulation shows that the system is thermally insensitive in the temperature range from −40∘C to 60°C, consistently providing great imaging capability with the modulation transfer function (MTF) value at 133 lp/mm greater than 0.3. The proposed design and analysis workflow contains an evaluation of thermal optical performance with a higher accuracy, thus having significance in future athermal optical design. We expect the designed PAL system to have a broad application prospect in the field of outdoor applications, including automatic navigation of vehicles and all-weather surveillance systems.

Design of Dual-Focal-Plane AR-HUD Optical System Based on a Single Picture Generation Unit and Two Freeform Mirrors

Augmented reality heads-up displays (AR-HUDs) have a much richer display than traditional heads-up displays. An ideal AR-HUD requires two or more focal planes to display basic and interactive driving information to the car driver separately. We present an off-axis reflective optical structure for dual-focal-plane displays using a single projection-type picture generation unit (PGU) and two freeform mirrors. The dual-focal-plane AR-HUD system designed in this paper can simultaneously generate high-quality far-field image (13° × 4°, 10 m) and near-field images (13° × 1.4°, 3.5 m) in a 130 mm × 60 mm eyebox. A fully automated analysis program is written to analyze the modulation transfer function (MTF) and distortion values of the optical system over the entire eyebox range. The analysis results show that the maximum distortion values of the far-field image and near-field image in the eyebox range are 3.15% and 3.58%, respectively. The MTF was greater than 0.3 at 7.2 lp/mm for both near-field images and far-field images. We also designed a projection lens for the projection-type PGU used in this system. The projection lens uses three plane mirrors to fold the image plane of the projection system into different positions to serve as the image source for the AR-HUD. This research provides a new solution for realizing the dual-focal-plane AR-HUD, which not only satisfies the need for simultaneous display of near-field basic information and far-field interactive information, but also has a larger display screen.

PENGARUH PARAMETER CT UNTUK OPTIMISASI DOSIS RADIASI DAN KUALITAS CITRA CT SCAN PADA PEMERIKSAAN KEPALA DAN ABDOMEN DI RS SENTRA MEDIKA CIBINONG

Radiation dose optimization in head and abdomen examinations is an effort to ensure safety and minimize the risks of exposure to CT Scan radiation. Therefore, various efforts are necessary to reduce radiation doses. This study aims to obtain an optimal radiation dose while maintaining image quality. The optimization efforts were carried out by the radiology team at RS Sentra Medika Cibinong using the CT Scan GE OPTIMA 660. The method involved scanning head and abdomen phantoms using optimization factors (Noise Index, Slice Thickness, Pitch, and Rotation Time) and then analyzing the images for noise uniformity, MTF (Modulation Transfer Function), and NPS (Noise Power Spectrum) while recording radiation dose in terms of CTDIvol and DLP. Based on the research data using GE standard Head protocol and respective optimizations, the radiation dose values obtained were CTDIVol = 68 mGy; DLP = 2042 mGy.cm and CTDIVol = 48 mGy; DLP = 1662 mGy.cm. Furthermore, the image quality produced by the GE standard Head protocol and respective optimizations resulted in MTF values of 0.55 (1/mm) and 0.91 (1/mm), noise uniformity of 0.6 HU and 1.6 HU, and NPS deviation of 8.7%. Regarding the Abdomen protocol, using GE standard and respective optimizations, the radiation dose values obtained were CTDIVol = 32 mGy; DLP = 1025 mGy.cm and CTDIVol = 22 mGy; DLP = 955 mGy.cm. Additionally, the image quality produced by the GE standard Abdomen protocol and respective optimizations resulted in MTF values of 0.58 (1/mm) and 0.6 (1/mm), noise uniformity of 0.6 HU and 1.6 HU, and NPS deviation of 7.6%. Thus, the protocols using optimization factors were proven to reduce radiation dose by approximately 41.6-45.4% while maintaining image quality compared to the GE standard protocol, which focuses more on improving image quality rather than optimizing the radiation dose received by patients. Keywords: CT Scan, Optimization Factors, Image Quality, CTDIvol, DLP.

Design method of freeform off-axis three-mirror reflective imaging systems.

In this paper, a novel, to the best of our knowledge, method is proposed to design a freeform off-axis three-mirror reflective imaging system. A special algorithm is demonstrated to calculate the data points on the unknown freeform surface using the rays from the pupil of the center field. Then the three-dimensional shape of the freeform surface is solved by these characteristic points, which serves as a good starting point for further optimization. The benefit of this design method is demonstrated by designing a freeform off-axis three mirror imaging system with high performance. The final system operates at F/2 with an entrance pupil diameter of 400mm and a field of view of 2.4∘×2.4∘. The modulation transfer function (MTF) value of the system reaches 0.6 at 100lp/mm or higher at all fields of view.

Comparison of cataract patients with regular corneal astigmatism after implantation of extended range-of-vision and bifocal toric intraocular lenses.

To compare the postoperative visual acuity and visual quality between extended range-of-vision and multifocal toric intraocular lens (IOLs) after implantation in cataract patients with regular corneal astigmatism. Department of Ophthalmology, the Second Hospital of Jilin University, Changchun, Jilin Province, China. Retrospective and single-center study. The study involved implanting the Tecnis Symphony (ZXR00IOL) or the bifocal toric (ZMTIOL) in patients undergoing cataract surgery. Three months after surgery, lens performance was evaluated using distance, intermediate, and near visual acuity tests, defocus curves, the modulation transfer function (MTF), a visual function index questionnaire (VF-14), and the adverse optical interference phenomena. The 3-month postoperative follow-up found that both groups had good corrected distance vision. The ZMT group had better-uncorrected distance visual acuity and near visual acuity (p < 0.05). However, the ZXR group showed better uncorrected intermediate visual acuity (p < 0.05) and visual continuity. Overall astigmatism in the postoperative ZMT group was significantly lower than that in the pre-operative group (p < 0.05). The ZMT group had lower total high-order aberrations (tHOs), higher MTF values, and higher VF-14 scores (p < 0.05). Finally, the ZXR group exhibited reduced halo and glare phenomena (p < 0.05). We found that ZMT can effectively correct a corneal astigmatism of 1.0-1.5 D and ZXR can improve patient outcomes regarding subjective optical quality and range of vision. These findings have the potential to improve future astigmatism treatment options.

Transparent 0D Antimony Halides Glassy Wafer with Near‐Unity Photoluminescence Quantum Yield for High Spatial Resolution X‐Ray Imaging

AbstractLarge‐sized transparent scintillators with a high photoluminescent quantum yield (PLQY) and self‐absorption‐free properties are highly desired to achieve high spatial resolution X‐ray imaging. In this research, a transparent 0D organic–inorganic (ETP)2SbCl5 (ETP = Ethyl triphenylphosphine) amorphous wafer is developed by melting the ETPCl and SbCl3 mixture and then undergoing a quenching process. The obtained amorphous wafer exhibits a high light transmittance of 86% in the range of 450–800 nm. It also shows a light emission peak at 624 nm, a Stokes shift of 259 nm, and PLQY approaching unity (99.3%). These properties enable it to produce X‐ray images with a high spatial resolution of 19.0 lp mm−1 at a modulation transfer function (MTF) value of 0.2, among the best values reported. Additionally, it also shows remarkable stability under continuous X‐ray illumination. Its unique optical properties and ability to be processed in large sizes make the organic–inorganic metal halide transparent wafer a promising scintillator. This also demonstrates the potential application of the melt‐quenching method in fabricating highly luminescent, low‐electronic‐dimensional metal halide wafers.

Analysis of the precision of modulation transfer function measurements with a circular edge: influence of object circularity.

To measure the modulation transfer function (MTF) using a circular edge, we generate a synthesized edge spread function from multiple profiles radiating from the center, assuming that the circular object is perfectly round. Therefore, this study aimed to quantify the influence of the shape change of the circular edge on the measurement precision of the MTF. To examine this relationship, we generated simulated images with intentionally distorted circular edges and analyzed the correlation between circularity and the calculated MTF. This simulation was designed to replicate the MTF properties of an actual computed tomography image and was applied to isolate the effect of shape distortion on MTF measurements. MTF measurements were conducted on 11 different circularity images to determine the spatial frequencies at which the MTF values are 50% () and 10% (), and the error rates to the true value were calculated. Our findings revealed a correlation between circularity and the measured MTF value. Specifically, an 1% decrease in circularity from the perfect circle condition resulted in an approximately change in . This decrease in MTF values was attributed to the presence of rectangular spatial blurring, which occurs when a distorted circular image is used to generate the synthetic edge profile. This study provided insights into the influence of the shape changes in the circular edge on MTF measurements. The present findings contribute to a better understanding of the evaluation results and measurement errors when describing the image quality characteristics modalities using the circular edge technique.

Initial Structure Design and Optimization of an Automotive Remote Head-Up Display

Aiming at the problems of difficult construction and occlusion of the initial structure of an automotive augmented reality head-up display (AR-HUD), a method to quickly build the initial structure of an automotive AR-HUD is proposed. Firstly, the position of the mirrors in the initial structure is calculated based on the Rodrigues rotation formula. Secondly, the position of the mirrors is restricted by constraints during optimization to prevent the problem of structural occlusion. Finally, a virtual image display system with a visual distance of 7.5 m and a field of view angle of 10° × 5° is designed. The image quality analysis of the optimized system shows that the light spots in each field of view are all within Airy spots. At the spatial cutoff frequency of the virtual image plane of the optical system, the modulation transfer function (MTF) value of the full field of view is basically greater than 0.5, and the distortion is less than 1%. Finally, using the image for simulation, the results of the simulation image are satisfying, which proves the validity and feasibility of the structural design. It provides a useful reference for the structural design of the remote head-up display system.

Improved On-Orbit MTF Measurement Method Based on Point Source Arrays

The modulation transfer function (MTF) is a key characteristic used to assess the performance of optical remote sensing satellite sensors. MTF detection can directly measure a sensor’s two-dimensional (2D) point spread function (PSF); therefore, it has been applied to various high-resolution remote sensing satellites (e.g., Pleiades) using point sources. However, current point source methods mainly use 2D Gaussian functions to fit the discrete digital number (DN) of the point source on the image to extract the center of the point source and fit the PSF after encrypting multiple point sources; thus, noise robustness is poor and measurement accuracy varies widely. In this study, we developed a noise-resistant on-orbit MTF detection method based on the object space constraint among point source arrays. Utilizing object space constraint relationships among points in a point source array, a homography transformation model was established, enabling accurate extraction of sub-pixel coordinates for each point source response. Subsequently, aligning the luminosity distribution of all point sources concerning a reference point source, the encrypted PSF was obtained and then fitted to obtain the MTF. To validate the method, Gaofen-2 (GF-2) satellite images were used to conduct an in-orbit imaging experiment on the point source array of the Chinese Zhongwei remote sensing satellite calibration site. Compared with the Gaussian model methods, the proposed method yielded more accurate peak positions for each point source. Standard deviations of peak position constant ratios in along- and cross-track directions improved by 2.8 and 4.8 times, respectively. The root-mean-square error (RMSE) of the collinearity test results increased by 92%, and the noise resistance of the MTF curve improved by two times. Dynamic MTF values at the Nyquist frequency for the GF-2 panchromatic band in along- and cross-track directions were 0.0476 and 0.0705, respectively, and MTF values in different directions were well distinguished.

Rectangular and radial region of interests on the edge of cylindrical phantom for spatial resolution measurement

&lt;span lang="EN-US"&gt;The purpose of this study was to evaluate the effect of rectangular region of interest (ROI) size on modulation transfer function (MTF), to develop the radial ROI, and to compare both ROIs performances for MTF measurement using a cylindrical polymethyl methacrylate (PMMA) phantom. The PMMA phantom used in this study was rotated 45°. Four rectangular ROIs and a radial ROI were created to measure the MTF value. The rectangular ROI sizes were 3×41, 21×41, 41×41, and 61×41 pixels; each was placed at upper phantom edge. The radial ROI’s length was 41 pixels and placed at several points in phantom edge. The MTF calculation was automatically conducted using MATLAB. The MTFs from rectangular ROIs and radial ROI were then compared. The comparison of the MTF measurement was also conducted using three different filters. The MTF which used radial ROI was smoother than those of rectangular ROI for all filters. This indicated that radial ROI was more resistant to noise than rectangular ROI. Rectangular ROI with the 41×41 pixels had similar 50% and 10% MTF values with the radial ROI. The MTF value which was obtained using radial ROI is more accurate and robust than those obtained using rectangular ROI.&lt;/span&gt;

The tolerance of refractive errors of extended depth of focus intraocular lens in patients with previous corneal refractive surgery.

To evaluate the tolerance for refractive errors and visual outcomes of extended depth of focus intraocular lens (EDOF IOLs) in patients with previous corneal refractive surgery for myopia. Patients from Aier Eye Hospital of Wuhan University with previous myopia excimer laser correction underwent cataract surgery and implantation of an EDOF IOL. The follow-up period was three months. The uncorrected distance, intermediate, and near visual acuities (UDVA, UIVA, UNVA), corrected distance visual acuity (CDVA), spherical equivalent (SE), defocus curve, optical quality, including modulation transfer functions (MTF) and Strehl ratio (SR), National Eye Institute Visual Functioning Questionnaire-14 for Chinese people (VF-14-CN), spectacle independence, and dysphotopsia were assessed. At the final visit, UDVA, CDVA, UIVA, and UNVA (LogMAR) were 0.06 ± 0.09, 0.01 ± 0.06, 0.11 ± 0.08, 0.20 ± 0.10, respectively. The mean spherical equivalent (SE) was - 0.57 ± 0.58D, sphere and cylinder were - 0.24 ± 0.60D, - 0.70 ± 0.58D respectively. No statistical difference in UDVA between eyes with SE in ± 0.50 D and in ± 1.0 D (p > 0.05). Corneal astigmatism > 1.00D has no significant effect on postoperative visual acuity (p > 0.05). The defocus curve showed that visual acuity could reach 0.2 in the refractive range of + 0.50D ~ - 1.50D. SR and MTF values were all higher than before the surgery. In bilateral implantation patients, the VF-14-CN questionnaire score and visual quality were quite excellent. The EDOF IOL have a certain tolerance for refractive errors and corneal astigmatism, and it's recommended for patients with prior myopia excimer laser surgery to achieve satisfactory visual performance.