Pupil Radius Research Articles

Fluorescence emission difference microscopy by superoscillation excitation.

A superresolution fluorescence emission difference (FED) microscopy based on superoscillation excitation is investigated. The solid superoscillation excitation spot is produced by the radially polarised Laguerre-Gaussian beam (LG), and the donut superoscillation excitation spot is produced by the same LG beam with spiral phase modulation. We show that the superoscillation excitation can enhance the spatial resolution of FED microscopy. When the ratio of the pupil radius and the second moment radius of the LG3,1 beam is 0.85 and the subtractive factor is 0.3, the resolution can be enhanced about 2 times than the general confocal microscopy. Compared with the general FED microscopy, the resolution can be enhanced about 1.1 times. Our simulations also demonstrate that two-view Richardson-Lucy (RL) deconvolution method can reduce the effect of side lobes, which is related to subtractive factor and pinhole. LAY DESCRIPTION: The fluorescence emission difference (FED) microscopy is a high-resolution light microscopy, which is based on the subtraction of images produced by two different confocal imaging modes. Here, the solid excitation spot is used in one imaging mode, and the donut excitation spot is in another imaging mode. There are various ways that the solid and donut excitation spots can be structured, but superoscillation excitation spots are still not used in the FED microscopy. Considering that the main lobe of superoscillation can be arbitrarily small in principle, we exploit the radially polarised Laguerre-Gaussian beam (LG) and spiral phase plate to produce superoscillation solid and donut spots. We present a detailed analysis about the performance of FED microscopy via superoscillation excitation. Our analysis is based on vector diffraction theory and supported by simulations of imaging. We find the proposed FED microscopy has better resolution than the confocal microscopy or the general FED microscopy excited by Gaussian beam. Especially, two-view Richardson-Lucy (RL) deconvolution method can reduce the negative impact of strong side lobes, which is related to the subtractive factor and the size of pinhole located at the detector.

Effectiveness evaluation of iris segmentation by using geodesic active contour (GAC)

A novel iris segmentation technique based on active contour is proposed in this paper. Our approach uses innovative algorithms, including two important ones, pupil segmentation and iris circle calculation. With our algorithms, we are able to find the center position and radius of pupil correctly and segment the iris precisely. The accuracy of our proposed method for ICE dataset is around 92% and also reached high accuracy level of 79% for UBIRIS. Our results demonstrate that the proposed iris segmentation method can perform well with high accuracy and better efficacy for Iris segmentation in images. Through a relatively high-performance algorithm to further cut up the round out the picture of the pupil conversion cutting growth square picture in order to make the judgment for biometric applications.

ACCURACY ESTIMATION OF THE OPTICAL FLOWMETHODS IN THE IRIS STRUCTURE MOTION ANALYSIS VIA CONTROLLED DEFORMATIONS

Abstract. The iris structure motion is analyzed. Extension and compression of the iris structural elements are nonlinear with respect to the pupil radius change. To reveal this nonlinearity the Lucas-Kanade, Horn-Schunck and modified Horn-Chunck optical flow methods are used. To aim is to estimate the accuracies of these methods. To solve the problem an implementation of the methods on the synthetic data is proposed. The data are obtained by applying deformations, which correspond to the certain models, to the eye images. The results of the methods implementation are compared with the used models and the accuracies are estimated on the basis of this comparison. The dataset of N eye images is used to generate the synthetic videos.

Atypical pupillary light reflex in 2-6-year-old children with autism spectrum disorders.

The purpose of this study was to investigate pupillary light reflex (PLR) in 2-6-years-old children with autism spectrum disorders (ASD). A total of 117 medication-free 2-6-year-old boys participated in this study. Sixty participants were diagnosed with ASD (the "ASD group") and the other 57 were in the control group of typical development (the "TD group"). A questionnaire was completed by the parent/guardian for assessing potential dysfunctions in the autonomic nervous system (ANS). The base pupil radius, PLR latency, and constriction time showed a significant age-related trend in both the ASD and TD groups. The base pupil size increased with age in the typically developing children, but not in the ASD group. The ASD group showed more symptoms related to ANS dysfunctions. An association between abnormal sweating with base pupil radius and PLR constriction was observed in the TD group but not the ASD group. The different association of PLR parameters with ANS dysfunction may suggest disrupted autonomic controls in children with ASD. Autism Res 2017, 10: 829-838. © 2017 International Society for Autism Research, Wiley Periodicals, Inc.

Efficient iris localization and recognition

Iris localization is an important step in iris recognition systems; all the subsequent steps, iris normalization, feature extraction and matching, depend on its accuracy. Traditional iris localization methods often involve an exhaustive search of a three-dimensional parameter space, which is a time consuming process. This paper presents a coarse-to-fine algorithm to address the computational cost problem, while achieving an acceptable accuracy. The iris gray image is transformed to a binary image using an adaptive threshold obtained from analyzing the image intensity histogram. Morphological processing is then used to extract an initial center point, which is considered as the initial center for both pupil and iris boundaries. Finally, a refinement step is made using an integro-differential operator to get the final iris and pupil centers and radii. This system proves to be robust against occlusions and intensity variations.

New Objective Refraction Metric Based on Sphere Fitting to the Wavefront.

Purpose To develop an objective refraction formula based on the ocular wavefront error (WFE) expressed in terms of Zernike coefficients and pupil radius, which would be an accurate predictor of subjective spherical equivalent (SE) for different pupil sizes. Methods A sphere is fitted to the ocular wavefront at the center and at a variable distance, t. The optimal fitting distance, topt, is obtained empirically from a dataset of 308 eyes as a function of objective refraction pupil radius, r0, and used to define the formula of a new wavefront refraction metric (MTR). The metric is tested in another, independent dataset of 200 eyes. Results For pupil radii r0 ≤ 2 mm, the new metric predicts the equivalent sphere with similar accuracy (<0.1D), however, for r0 > 2 mm, the mean error of traditional metrics can increase beyond 0.25D, and the MTR remains accurate. The proposed metric allows clinicians to obtain an accurate clinical spherical equivalent value without rescaling/refitting of the wavefront coefficients. It has the potential to be developed into a metric which will be able to predict full spherocylindrical refraction for the desired illumination conditions and corresponding pupil size.

Establishing Age-Adjusted Reference Ranges for Iris-Related Parameters in Open Angle Eyes with Anterior Segment Optical Coherence Tomography.

PurposeDefine criteria for iris-related parameters in an adult open angle population as measured with swept source Fourier domain anterior segment optical coherence tomography (ASOCT).MethodsNinety-eight eyes of 98 participants with open angles were included and stratified into 5 age groups (18–35, 36–45, 46–55, 56–65, and 66–79 years). ASOCT scans with 3D mode angle analysis were taken with the CASIA SS-1000 (Tomey Corporation, Nagoya, Japan) and analyzed using the Anterior Chamber Analysis and Interpretation software. Anterior iris surface length (AISL), length of scleral spur landmark (SSL) to pupillary margin (SSL-to-PM), iris contour ratio (ICR = AISL/SSL-to-PM), pupil radius, radius of iris centroid (RICe), and iris volume were measured. Outcome variables were summarized for all eyes and age groups, and mean values among age groups were compared using one-way analysis of variance. Stepwise regression analysis was used to investigate demographic and ocular characteristic factors that affected each iris-related parameter.ResultsMean (±SD) values were 2.24 mm (±0.46), 4.06 mm (±0.27), 3.65 mm (±0.48), 4.16 mm (±0.47), 1.14 (±0.04), 1.51 mm2 (±0.23), and 38.42 μL (±4.91) for pupillary radius, RICe, SSL-to-PM, AISL, ICR, iris cross-sectional area, and iris volume, respectively. Both pupillary radius (P = 0.002) and RICe (P = 0.027) decreased with age, while SSL-to-PM (P = 0.002) and AISL increased with age (P = 0.001). ICR (P = 0.54) and iris volume (P = 0.49) were not affected by age.ConclusionThis study establishes reference values for iris-related parameters in an adult open angle population, which will be useful for future studies examining the role of iris changes in pathologic states.

Individual Differences in Emotional Reactivity and Academic Achievement: A Psychophysiological Study

ABSTRACTFactors related to grade point average (GPA) are of great importance for students' success. Yet, little is known about the impact of individual differences in emotional reactivity on students' academic performance. We aimed to examine the emotional reactivity–GPA link and to assess whether self‐esteem and psychological distress moderate this relationship.Eighty undergraduate students reported on their GPA, self‐esteem, and psychological distress. Students' pupil radius was monitored during affective picture viewing to assess sympathetic activation in response to emotional stimuli. Cluster analysis on pupil reactivity to pictures identified low, average, and high emotionally reactive students. Regression analyses indicated that profiles of emotional reactivity were associated with GPA. This relationship was moderated by self‐esteem, but not psychological distress. Among students with higher emotional reactivity, those with lower self‐esteem reported poorer GPA. Findings document the importance of differences in students' emotional reactivity and self‐esteem in relation to academic success.

Influence of pupil on the laser beam shaping system by pure phase modulation

In this paper, we propose a quantitative approach to analyze the influence of pupil truncation on the phase-only modulation laser beam shaping system, based on the near-field phase and the far-field metric functions. First, the relationship between near-field phase and pupil radius is studied by Lagrange multiplier method. Result indicates that both the peak-to-valley and the root-mean-square of the near-field phase increase approximately linearly with the pupil radius. Second, the influence of pupil radius on a beam shaping system is investigated. To quantify the performance of the beam shaping system, the correlation coefficient (C) and the mean square difference (MSD) are introduced as the metric functions. Then, by comparing the metric functions at different pupil radius, it is shown that the pupil radius influences the performance of focal beam shaping distinctly at the lower pupil radius, whereas the influence trails off, and both the C and the MSD get close to the theoretical limit as the pupil radius continuously increases. Third, the mathematical models of the C and the MSD are proposed to reveal the relationship among the metric functions, pupil radius and target intensity's size, as it is difficult to obtain the explicit expressions on the basis of metric functions' definition. And the three coefficients in each model are ascertained by surface fitting method based on the sampling data. In addition, SSE (sum of square due to error), RMSE (root mean square error) and R-square (coefficient of determination) are adopted to determine the fitting precision. For both the metric functions, the precision of SSE and RMSE can reach 10-2 and the R-square is shown to be more than 97%. The SSE, RMSE and R-square verify the proposed mathematical models. Finally, according to the models, we analyze when the influence of pupil truncation becomes negligible for the rectangle or circle target intensity. In practice, the size of target intensity is determined first. Sequentially, by combining the mathematical models and their first-order partial differentials, the changing regularity of metric functions with respect to pupil radius is studied. Meanwhile, the regularity helps us to find the beginning points for rectangle target and circle target intensities respectively. For the rectangle target intensity, when the pupil radius is 2.5 times that of the Gaussian waist radius, the metric functions become stable. The C with a value of 0.997 and the MSD with a value of 410-4 are both close to the theoretical limit. In the meantime, the influence of pupil truncation tends to be minimal as expected. For circle target intensity, when the pupil radius is 3 times that of the Gaussian waist radius, the first-order partial differentials of the C and the MSD decrease to about 10-3. This means that the metric functions begin to converge and that the influence of pupil truncation tends to be minimal at this point. Consequently, it is effective and meaningful to determine the best pupil radius using the proposed models in the article when designing a beam shaping system. Moreover, the models can also be used to evaluate the performance of a laser beam shaping system.

Pupil and Glint Detection Using Wearable Camera Sensor and Near-Infrared LED Array.

This paper proposes a novel pupil and glint detection method for gaze tracking system using a wearable camera sensor and near-infrared LED array. A novel circular ring rays location (CRRL) method is proposed for pupil boundary points detection. Firstly, improved Otsu optimal threshold binarization, opening-and-closing operation and projection of 3D gray-level histogram are utilized to estimate rough pupil center and radius. Secondly, a circular ring area including pupil edge inside is determined according to rough pupil center and radius. Thirdly, a series of rays are shot from inner to outer ring to collect pupil boundary points. Interference points are eliminated by calculating gradient amplitude. At last, an improved total least squares is proposed to fit collected pupil boundary points. In addition, the improved total least squares developed is utilized for the solution of Gaussian function deformation to calculate glint center. The experimental results show that the proposed method is more robust and accurate than conventional detection methods. When interference factors such as glints and natural light reflection are located on pupil contour, pupil boundary points and center can be detected accurately. The proposed method contributes to enhance stability, accuracy and real-time quality of gaze tracking system.

Influence of Source Light in Clinical Parameters of Pupillary Cycle

The pupil diameter and its dynamic motion can be analyzed by pupillometry. This technique is usually applied in researches on the autonomic nervous system. The pupillometer analyze numerically the parameters of pupil however, the spatial and temporal resolution of commercial devices are the most significant metrology parameters. This article presents an experimental device that describes the influence in clinical parameters of optical pupillometry due luminance and wavelength variation. Specifically, in the dynamic pupillometry response in order to maximize the interaction between Pupil Light Reflex (PLR) and the nervous system. The key point is the tracking of pupil radius and position associated with the predominant wavelength and luminance frame by frame during the pupillary cycle. The clinical parameters are amplitude, latency, dilation and contraction velocity, maximum and minimum size of pupil according papers and researches in this area. There are already reports on the usefulness of pupillometry in the research of various diseases and the results when compared to some existing in the literature shows significant differences due the stimulator.

Tight focusing induces pulse delay and pulse compression of double-ring-shaped radially polarized ultrashort light pulses

The focusing of double-ring-shaped radially polarized ultrashort light pulses by a high-numerical aperture objective is investigated using vectorial Debye theory. After focusing, the double-ring-shaped radially polarized ultrashort light pulses slow down near the focus, and this pulse delay induces pulse compression in the propagation direction. That is, without changing the pulse duration, the spatial pulse length of the ultrashort light pulse is decreased near the focus. The velocity of the longitudinal component of the light pulse near the focus is lower than that of the radial component. The simulation results demonstrate that control of the ratio of the pupil radius to the beam radius affects not only the longitudinal component of the light pulse, but also the velocity and spatial pulse length of the light pulse because of the destructive interference between the longitudinal components of the inner and outer rings of the light pulse.

A Low Cost Pupillometry Approach

The need for low-cost health monitoring is increasing with the continuous increase of the elderly population. In this context, unobtrusive audiovisual monitoring methods can be of great importance. More particularly, the diameter of the pupil is a valuable source of information, since, apart from pathological cases, it can reveal the emotional state, the fatigue and the ageing. To allow for unobtrusive monitoring to gain acceptance, one should seek for efficient methods of monitoring using common low-cost hardware. This paper describes a method for monitoring pupil sizes using a common, low-cost web camera in real time. The proposed approach detects the face and the eyes area at first stage. Subsequently, optimal iris and sclera location and radius, modeled as ellipses, are found using efficient spatial filtering. As a final step, the pupil center and radius is estimated by optimal filtering within the area of the iris. Experimental results show both the efficiency and the effectiveness of our approach.

Investigating the focus shaping of the TEM11* beam with radial varying polarization

In this article, based on vector diffraction theory the focusing properties of double ring shaped higher order Laguerre–Gauss beam with radial varying polarization are investigated numerically. The numerical simulations show that the evolution of some interesting focal spot, focal split and focal patterns in the focal region by changing polarization rotation angle under tight focusing through the high NA lens. It is also shown that a subwavelength focal hole with a quite long depth of focus, multiple focal holes are achieved near the focus, when tuning β (is the ratio of the pupil radius to the beam waist) in the focal plane for different modes under tight focusing through the high NA lens. We found that when tuning, beam parameter or the polarization rotation angle of the incident beam, it is possible to generate some interesting novel focal patterns, including multiple intensity rings, dark hollow focus and cylindrical crust focus. Such kind of beams plays an important role in optical trapping, laser cutting and optical manipulation applications.

Type 2 diabetes and cardiac autonomic neuropathy screening using dynamic pupillometry.

To determine if changes in pupillary response are useful as a screening tool for diabetes and to assess whether pupillometry is associated with cardiac autonomic neuropathy. We conducted a cross-sectional study with participants drawn from two settings: a hospital and a community site. At the community site, individuals with newly diagnosed diabetes as well as a random sample of control individuals without diabetes, confirmed by oral glucose tolerance test, were selected. Participants underwent an LED light stimulus test and eight pupillometry variables were measured. Outcomes were diabetes, defined by oral glucose tolerance test, and cardiac autonomic dysfunction, determined by a positive readout on two of four diagnostic tests: heart rate response to the Valsalva manoeuvre; orthostatic hypotension; 30:15 ratio; and expiration-to-inspiration ratio. The area under the curve, best threshold, sensitivity and specificity of each pupillometry variable was calculated. Data from 384 people, 213 with diabetes, were analysed. The mean (±sd) age of the people with diabetes was 58.6 (±8.2) years and in the control subjects it was 56.1 (±8.6) years. When comparing individuals with and without diabetes, the amplitude of the pupil reaction had the highest area under the curve [0.69 (sensitivity: 78%; specificity: 55%)]. Cardiac autonomic neuropathy was present in 51 of the 138 people evaluated (37.0%; 95% CI 28.8-45.1). To diagnose cardiac autonomic neuropathy, two pupillometry variables had the highest area under the curve: baseline pupil radius [area under the curve: 0.71 (sensitivity: 51%; specificity: 84%)], and amplitude of the pupil reaction [area under the curve: 0.70 (sensitivity: 82%; specificity: 55%)]. Pupillometry is an inexpensive technique to screen for diabetes and cardiac autonomic neuropathy, but it does not have sufficient accuracy for clinical use as a screening tool.

Effect of Pupil Beam in the Focal Region of High Numerical Aperture Objective Lens

In this article, based on vector diffraction theory the focusing properties of double ring shaped higher order Laguerre - Gauss beam with radial varying polarization are investigated numerically. The numerical simulations show that the evolution of some interesting focal spot, focal split and focal patterns in the focal region by changing polarization rotation angle under tight focusing through the high NA lens. It is also shown that a subwavelength focal hole with a quite long depth of focus, multiple focal holes are achieved near the focus, when tuning β (is the ratio of the pupil radius to the beam waist) in the focal plane for different modes under tight focusing through the high NA lens. We found that when tuning, beam parameter or the polarization rotation angle of the incident beam, it is possible to generate some interesting novel focal patterns, including multiple intensity rings, dark hollow focus and cylindrical crust focus. Such kind of beams plays an important role in optical trapping, laser cutting and optical manipulation applications.

Representation and focusing properties of higher-order radially polarized Laguerre–Gaussian beams

A method based on higher-order Poincaré sphere was proposed to represent the states of polarization of higher-order radially polarized Laguerre–Gaussian (LG) vectorial beams (VBs). And the focusing properties of such LG beams of different radial orders focused by a high-NA lens were discussed. By tuning the ratio of the pupil radius to the waist of the incident beams, some cage-like or needlelike electric intensity field is generated in the focal region for several specific LG VBs with high order. Modulated by diffractive optical elements, the shape of the focal field shows novel behaviors such as splitting of cage-like modes, which provides potentially a more flexible control over micro-particles.

Spherical and sub-wavelength longitudinal magnetization generated by 4π tightly focusing radially polarized vortex beams.

Based on the vector diffraction theory and the inverse Faraday effect, we numerically study the light-induced magnetization near the focus of a 4π high numerical aperture focusing configuration under the illumination of two counter- propagating radially polarized hollow Gaussian vortex beams. The simulated results demonstrate that, by selecting higher-order vortex beam modes (e.g. n=4with n - the beam order) and proper truncation parameter (e.g. β=1.75 with β- the ratio of the pupil radius to the incident beam waist), spherical and sub-wavelength longitudinal magnetization can be generated in the vicinity of focus. Such special magnetization feature is attributed to not only the interaction between optical vortices and the radially polarized beams, but also the completely destructive interference of azimuthal components and the constructive interference of the longitudinal component of the two counter-propagating radially polarized vortex beams. This spherical and sub-wavelength longitudinal magnetization distribution may be of interest for applications in all-optical magnetic recording and confocal and magnetic resonance microscopy.

Smartphone based visible iris recognition using deep sparse filtering

Good biometric performance of iris recognition motivates it to be used for many large scale security and access control applications. Recent works have identified visible spectrum iris recognition as a viable option with considerable performance. Key advantages of visible spectrum iris recognition include the possibility of iris imaging in on-the-move and at-a-distance scenarios as compared to fixed range imaging in near-infra-red light. The unconstrained iris imaging captures the images with largely varying radius of iris and pupil. In this work, we propose a new segmentation scheme and adapt it to smartphone based visible iris images for approximating the radius of the iris to achieve robust segmentation. The proposed technique has shown the improved segmentation accuracy up to 85% with standard OSIRIS v4.1. This work also proposes a new feature extraction method based on deep sparse filtering to obtain robust features for unconstrained iris images. To evaluate the proposed segmentation scheme and feature extraction scheme, we employ a publicly available database and also compose a new iris image database. The newly composed iris image database (VSSIRIS) is acquired using two different smartphones – iPhone 5S and Nokia Lumia 1020 under mixed illumination with unconstrained conditions in visible spectrum. The biometric performance is benchmarked based on the equal error rate (EER) obtained from various state-of-art schemes and proposed feature extraction scheme. An impressive EER of 1.62% is obtained on our VSSIRIS database and an average gain of around 2% in EER is obtained on the public database as compared to the well-known state-of-art schemes.

Study on polarization effect of azimuthally polarized LG beam in high NA Lens system

Based on vector diffraction theory, the intensity distributions of azimuthally polarized double-ring-shaped higher order beams near the focus are calculated numerically. It is shown that a subwavelength focal hole with a quite long depth of focus, multiple focal holes are achieved near the focus, when tuning β (is the ratio of the pupil radius to the beam waist) in the focal plane for different modes under tight focusing through high NA lens. Such kind of beams plays an important role in optical trapping, laser cutting and optical manipulation applications.