Pupil Location Research Articles

Iris segmentation using pupil location, linearization, and limbus boundary reconstruction in ambient intelligent environments

Advances in sensors and technology, on one side, and recognition techniques, on the other side, make the iris a top candidate for biometric use. Iris detection and segmentation, however, are still lacking. We propose here a novel iris segmentation technique using pupil location, linearization, and limbus boundary reconstruction, and show its feasibility and comparative advantages against existing methods.

Automatic localization of pupil using eccentricity and iris using gradient based method

This paper presents a novel approach for the automatic localization of pupil and iris. Pupil and iris are nearly circular regions, which are surrounded by sclera, eyelids and eyelashes. The localization of both pupil and iris is extremely important in any iris recognition system. In the proposed algorithm pupil is localized using Eccentricity based Bisection method which looks for the region that has the highest probability of having pupil. While iris localization is carried out in two steps. In the first step, iris image is directionally segmented and a noise free region (region of interest) is extracted. In the second step, angular lines in the region of interest are extracted and the edge points of iris outer boundary are found through the gradient of these lines. The proposed method is tested on CASIA ver 1.0 and MMU Iris databases. Experimental results show that this method is comparatively accurate.

Noise in Wavefront Error Measurement from Pupil Center Location Uncertainty

To examine the impact of pupil center location uncertainty in wavefront sensing on the variance in repeated measures of higher order root-mean-square (RMS) wavefront error (WFE). Dilated WFE for one normal eye and one eye with keratoconus of two patients were measured using a custom Shack-Hartmann wavefront sensor (lenslet spacing 400 μm). Twelve measurements for each patient were averaged to form the best estimate of each eye's WFE and standard deviation. The percentage of the standard deviation of the actual measurements attributable to the uncertainty in pupil center location was modeled by inducing random offsets in the pupil center up to 50, 100, 150, and 200 μm. The percentage of standard deviation of the actual measurements accounted for by pupil location uncertainty form a complex interaction between magnitude and distribution of the higher order WFE with the magnitude of pupil centering error. The larger the WFE and pupil center uncertainty, the greater the effect. As pupil center uncertainty increases, so does the WFE variation in repeated measurements. The larger the underlying WFE, the greater the impact on measurement variation. Increasing measurement variation decreases the ability to detect changes in WFE (eg, as a function of aging or clinical intervention) and decreases the accuracy with which wavefront-guided corrections can be made.

Distorted Pupil Localization in Eye Tracking

在视线跟踪过程中，变形瞳孔的定位至关重要。针对眼部图像出现干扰情况下的变形瞳孔定位，该文提出了一种基于3点的随机采样一致性定位算法RANSAC_3，即利用随机采样到的2点(以及它们的梯度方向)和搜索获得的1个点来确定椭圆参数。由于该算法在确定参数时只需随机采样两个点，从而大大降低了采样到干扰点的几率，利用搜索到的第3点来决定是否对当前点进行参数计算，有效地解决了标准随机采样一致性定位算法中的无效采样和误差累积问题，提高了椭圆拟合效率和瞳孔定位精度。实验证明，该算法对变形瞳孔具有很好的定位效果，对光斑、睫毛、头发、眼镜框以及眼球运动模糊的引起的干扰具有较强的鲁棒性，并且定位速度快，可以达到实时要求。

A knowledge-based approach to the iris segmentation problem

This paper describes a knowledge-based approach to the problem of locating and segmenting the iris in images showing close-up human eyes. This approach is inspired in the expert system’s paradigm but, due the specific processing problems associated with image analysis, uses direct encoding of the “decision rules”, instead of a classic, formalized, knowledge base. The algorithm involves a succession of phases that deal with image pre-processing, pupil location, iris location, combination of pupil and iris, eyelids detection, and filtering of reflections. The development was iterative, based on successive improvements tested over a set of training images. The results that were achieved indicate that this global approach can be useful to solve image analysis problems over which human “experts” have better performance than the present computer-based solutions.

Fast and robust iris recognition

Iris recognition is a reliable biometric identification technology. In this study, the one-to-many identification and one-to-one verification using iris recognition are both examined. Our method consists of three phases: pupil and iris location, iris feature image extraction and iris matching. The CASIA iris database was used in this study to evaluate the performance of the proposed method. The database includes 108 iris classes, each including seven images. The identification accuracy of our method is 99.646%; while the proposed method can achieve an equal error rate of 1.085%. On the other hand, feature extraction of an iris image in our method is only 16.78 ms. Each verification test of an iris images takes 1.4 ms and each identification test over 432 database images takes 151.2 ms. Note the experimental accuracies were reported without manual rejection of poor-quality images or invalid iris-location images, thus the efficiency and robustness of the proposed method can be proven.

Aberrations and Pupil Location under Corneal Topography and Hartmann-Shack Illumination Conditions

This study was conducted to determine the magnitude of pupil center shift between the illumination conditions provided by corneal topography measurement (photopic illuminance) and by Hartmann-Shack aberrometry (mesopic illuminance) and to investigate the importance of this shift when calculating corneal aberrations and for the success of wavefront-guided surgical procedures. Sixty-two subjects with emmetropia underwent corneal topography and Hartmann-Shack aberrometry. Corneal limbus and pupil edges were detected, and the differences between their respective centers were determined for both procedures. Corneal aberrations were calculated using the pupil centers for corneal topography and for Hartmann-Shack aberrometry. Bland-Altmann plots and paired t-tests were used to analyze the differences between corneal aberrations referenced to the two pupil centers. The mean magnitude (modulus) of the displacement of the pupil with the change of the illumination conditions was 0.21+/-0.11 mm. The effect of this pupillary shift was manifest for coma corneal aberrations for 5-mm pupils, but the two sets of aberrations calculated with the two pupil positions were not significantly different. Sixty-eight percent of the population had differences in coma smaller than 0.05 microm, and only 4% had differences larger than 0.1 microm. Pupil displacement was not large enough to significantly affect other higher-order Zernike modes. Estimated corneal aberrations changed slightly between photopic and mesopic illumination conditions given by corneal topography and Hartmann-Shack aberrometry. However, this systematic pupil shift, according to the published tolerances ranges, is enough to deteriorate the optical quality below the theoretically predicted diffraction limit of wavefront-guided corneal surgery.

System Architecture of Atopic Dermatitis Adjuvant for Children Using Wireless Sensor

Pre schools with state of the art facilities that would provide not just academic excellence but also ensure the safety and provide efficient healthcare to their pupils relative to Atopic Dermatitis with Asthma is the main objective of this research One of the most promising applications of sensor networks is for human healthcare monitoring. Due to recent technological advances in sensor, low power microelectronics and miniaturization, and wireless networking enable the design and proliferation of this wireless sensor networks capable of autonomously monitoring and controlling environments. Thus, this research presents the utilization of such microelectronic sensor and plots the hardware and software architecture of a wireless sensor network system with real-time pupil monitoring that integrates vital sign sensors, location sensor and allergen sensor. This proposed architecture for wearable sensors can be used as active tags which can track pupil's location within the school's premises, identify possible atopic dermatitis with asthma allergens, it would monitor and generate a health status report of the pupil.

Wearable pupil position detection system utilizing dye-sensitized photovoltaic devices

Detection of the line-of-sight (LOS) has a variety of applications, such as communication tools for elderly or disabled people, assisting drivers, and effective location of traffic signs. To realize such promising applications, there is strong demand for an LOS detection system that does not restrict users’ activities and inflicts no mental stress. The LOS can be obtained by combining the directions of the face and eyes, respectively, where the detection of location and motion of the pupils is a critical technology. In this paper, we propose a novel wearable pupil position detection system, featuring minimum disturbance to users, both physically and mentally, via the use of dye-sensitized photovoltaic devices. These latter are transparent and generate voltage according to the incident light intensity. Arraying the devices on wearable eyeglasses, this system detects the difference in the reflection light from the pupil and the white of the eye and hence determines the position of the pupil. It is wearable as an eyeglass, meaning it does not disturb users’ activities or eyesight. More importantly, it involves minimal physical and psychological stress. We fabricated the photovoltaic device and demonstrated their feasibility to determine the location of the pupil. We found it possible to meet the required reaction time of 100ms by reducing the size of the device and to improve the accuracy of pupil location detection by arraying the devices.

A Novel and Efficient Method for Iris Automatic Location

Abstract An efficient and robust iris location algorithm plays a very important role in a real iris recognition system. A novel and efficient iris automatic location method is presented in this study. It includes following two steps mainly: pupil location and iris outer boundary location. A digital eye image was divided into many small rectangular blocks with fixed size in the pupil location, and the block with the smallest average intensity was selected as a reference area. Then image binarization was implemented taking the average intensity of the reference area as a threshold. At last the center coordinates and radius of pupil were estimated by extending the reference area to the pupil's boundaries in the binary iris image. In the iris outer location, two local parts of the eye image were selected and transformed into polar coordinates from Cartesian reference. In order to detect the fainter outer boundary of the iris quickly, a novel edge detector was used to locate boundaries of the two parts. The center coordinates and radius of the iris outer boundary can be estimated using the fusion of the locating results of the two local parts and the location information of the pupil. The algorithm was tested on CASIA v1.0 and MMU v1.0 digital eye image databases and experimental results show that the proposed method has satisfying performance and good robustness.

PR48 UPPER BLEPHAROPLASTY

Introduction Upper blepharoplasty is performed in order to correct age‐related upper lid changes including dermatochalasis and irregular contours due to bulging post‐septal fat pads. Additionally, upper lid ptosis can be repaired in an anterior approach through the blepharoplasty incisions when indicated. These procedures are gratifying and have relatively low associated morbidity.Methods/Techniques Pre‐operative assessment includes observation of excess upper eyelid skin, bulging fat pads, lid position, and location of the suprataral crease. Most excess skin is located centrally and laterally. The most common bulging fat pad is the nasal fat pad, however the central fat pad also frequently requires excision. If a combination of procedures is being preformed, upper blepharoplsty follows browlifts and facelifts but precedes lower lid blepharoplasty. Surgical markings are made with the patient prone, under general anesthesia. Local anesthesia is also administered for hemostasis. The lower location of the incision is marked 8–10 mm above the lid margin centrally and 6 mm above the lateral canthus. The upper incision is identified by assessing the amount of excess skin by pinch testing. The upper incision is marked and calipers are used to confirm at least 10 mm of skin will still be present between the upper incision and the lower border of the eyebrow at the mid pupil location. A scalpel is used to make the incisions. A Bovie is used to cut through the orbicularis oculi muscle on cutting current. Westcott scissors are used to excise the skin and muscle. Hemostasis is acheived Gentle pressure is applied to the globe to reveal the excess nasal fat pad. The septum is opened focally and the excess portion of the fat pad is excised using coagulation current with the bovie. The central fat pad is reduced if needed. If ptosis exists, it is repaired using a tarso‐levator advancement technique. Often in cases of senile acquired ptosis, a high supratarsal fold exists. While the ptosis repair will partially resolve this cosmetic deformity, the septum is opened and the central fat pad is freed and advanced to further fill the sulcus. A supratarsal fixation stitch using 6‐O vicryl is placed in a mid pupil location to prevent postoperative ptosis. The wound is then closed with 6‐O nylon using interrupted sutures lateral to the lateral canthus and running sutures medial to the canthus.Results 527 patients underwent upper blepharoplasty with the technique described over a 12 year period. 10% underwent ptosis repair at the same time and all other patients underwent supratarsal fixation. 90% were satisfied satisfied with there procedure. Acute re‐operation for bleeding occurred in less than 1% of patients. The most common acute complication was chemosis occurring in 12% of patients which was far more likely to occur if a upper blepharoplasty was performed in conjunction with lower lid blepharoplasty. All cases of chemosis resolved with non‐surgical management including liberal use of ointment and taping the lid shut, and occasionally incision and drainage of the chemosis. The most common indication for re‐operation was residual excess skin.Conclusion Upper lid blepharoplasty is a very gratifying procedure whether preformed alone or in conjunction other procedures for facial rejuvenation. Complications are infrequent and generally minor. Satisfaction is generally very high. The open sky technique was used which includes removal of the skin, muscle, and septal flap with conservative fat removal.

Robust measurement of ocular torsion using iterative Lucas–Kanade

We present a new method to measure ocular torsion using Lucas–Kanade method. After pixels of iris annulus around a pupil have been converted into Cartesian coordinates, 30 features on the iris was selected then the features were tracked using the iterative Lucas–Kanade algorithm to calculate torsional shift. The results show that a precision of the method is higher than those measured by a conventional cross-correlation and by a template matching method. The suggested method showed 0.03° mean error with 0.15° maximum error. Particularly, the method was robust to change of pupil size and misalignment of pupil location. Processing time was also fast enough to be implemented in a real-time system.

A new segmentation approach for iris recognition based on hand-held capture device

Iris segmentation is an important step for automatic iris recognition. This paper presents a new iris segmentation method for hand-held capture device. We use a geometrical method for pupil detection. The bottom point of pupil is used as the reference point for pupil localization because it is insensitive to pupil dilation and not affected by the top eyelid or eyelashes. To decrease computational cost, the outer (or limbus) boundary of iris is localized based on shrunk image using Hough transform and modified Canny edge detector. The lower part of iris pattern is used for recognition in order to reduce the occlusion by eyelashes and eyelids. Experimental results demonstrate that the proposed method has an encouraging performance.

The Argyll Robertson Pupil

The Argyll Robertson (AR) pupil has been defined as a pupil that is small and constricts poorly to direct light but briskly when a target within reading distance is viewed ("light-near dissociation"). Most descriptions of the AR pupil do not mention segmental iris sphincter constriction, or slow, sustained constriction with a near vision effort. Such features are considered typical of the light-near dissociation of Adie syndrome and of neuropathic tonic pupils, where damage to the ciliary ganglion or ciliary nerves is believed to be the mechanism. Because the AR pupil lacks these features, it has been attributed to a dorsal midbrain lesion that interrupts the pupillary light reflex pathway but spares the more ventral pupillary near reflex pathway. However, lesions in this region have not been reliably demonstrated in syphilis. Resolving the issue about the location of the syphilitic lesion that produces the AR pupil will depend on careful examination of patients with techniques designed to disclose segmental palsy of the iris. If segmental iris sphincter palsy is found and the light-near dissociation has tonic features, one must conclude that the mechanism of the pupil disorder is a ciliary (peripheral) rather than a midbrain (central) denervation. Until better evidence settles the localization of the AR pupil, it is appropriate to screen patients with bilateral tonic pupils for syphilis.

Pupil location under scotopic, photopic and pharmacologically dilated conditions

目的 观察明视、暗视及药物散瞳状态下的瞳孔位置,评价瞳孔位置是否随瞳孔直径而改变及其与年龄、屈光不正等因素的相关性.方法运用Asclepion波前像差仪检测获得130例(130眼)屈光不正患者在明视、暗视及药物散瞳状态下的眼前节图像,设计软件计算图像中的瞳孔中心位置、角巩膜缘几何中心位置.结果随着瞳孔直径的增大,瞳孔中心位置始终向颞侧偏移.从明视到暗视,瞳孔直径平均由4.06 mm增至6.37 mm,而瞳孔中心平均向颞侧移动0.133 mm(t=4.604,P<0.01);从暗视到药物散瞳状态,瞳孔直径平均由6.37 mm增至7.58 mm,而瞳孔中心平均向颞上方移动0.162 mm(t=4.180,P<0.01);从明视到药物性散瞳,瞳孔中心平均向颞上方移动0.183 mm(t=7.378,P<0.01);但瞳孔中心位置的移动量与年龄、屈光不正度及瞳孔直径的改变值无显著相关性.结论瞳孔中心位置随着瞳孔直径的增大而主要向颞侧偏移同时略向上移动,但总的移动量不大。

Development of Pupillography Using Image Processing

Pupillary examination is an important objective method to diagnose lesions of the anterior visual pathways. However, errors and faults may easily alter the interpretation and value of the test as it is highly dependent on the examiner's skills. Therefore, we tried to develop a pupillography which is independent of the examiner. Hardware composed of a binocularly measuring instrument adapted for an infrared charge coupled device (CCD) was developed. Two arrays of infrared light emitting diodes (LED) were supplied in front of each of the subject's eyes. A microcontroller to modulate these LED was developed, as was software to save and analyze the pupil images. The hardware was able to deliver a light to either eye or to both eyes, and to change the time, frequency, and intensity of the stimulus. The software automatically analyzed the pupil size and location by image processing. Pupil size was calculated continuously. After artifact elimination, the response amplitudes of the pupils were determined for the right and left pupils. Pupillary images of size 320 x 240, at 30 frames/second, were saved and processed to evaluate the change of the actual pupil size and the velocity of pupillary response. A pupillography to measure, save and analyze the pupillary response using image processing was developed. Further detailed clinical studies with a large number of patients will be required to validate this new method.

Linear phase ring illumination monitor

A phase shifting mask pattern consisting of an Airy pattern multiplied by a linear phase progression is introduced as a quantitative monitor for the angular distribution of illumination in optical projection printing. The proximity effect spillover from the pattern rings is in phase at the center position only for illumination from the designed off-axis illumination direction. Thus, a quantitative analysis of the intensity in a particular pupil location is available simply by measuring intensity at the center of the pattern. A theoretical analysis is presented and image simulation studies are made of an implementation based on four-phase mask making. The results show that the signal strength is high (about 1/3–1/5 of the clear field intensity per ring), the angular discrimination is good (about 0.5/ring number), and that linear phase rings are reasonably unaffected by aberrations. Mask requirements suggest this technique is most advantageous for monitoring dipoles or quadrupoles. Since the patterns print at normal exposure levels, they may also be included on product wafers to fingerprint the illumination during production.

Predicting Mouth Width from Inter-Canine Width—A 75% Rule

It has been suggested that inter-canine width plus 57% of the cumulative distance between the lateral aspect of the canines and the pupil centers can be used to estimate mouth width. Evidence also suggests that the distance between the medial irises approximates actual mouth width fairly well. However, these soft tissue prediction guidelines are limited because they rely on accurate medio-lateral positioning of the pupils within the orbits, for which no systematic empirical evidence appears to exist at this stage. It would, therefore, be more appropriate to use only known hard tissue landmarks in mouth width prediction. This study reports the results of using inter-canine width as a percentage of mouth width for its prediction. This method seems favorable in comparison to the other guidelines because it is as accurate, uses known hard tissue landmarks, and does not rely on assumptions concerning pupil location. Estimating mouth width by using the canines alone, therefore, seems the best guideline to use in facial approximation techniques, at least given knowledge existing at this stage.

Aberrometry: The Past, Present, and Future of Optometry

2 pages.-- Guest editorial for 'Optometry and Vision Science', Vol. 80, No. 1 (January 2003).

Design of an in-water corrector system.

The optical design of systems for use in water is considered. Use of flat and concentric dome ports are discussed as well as problems with pupil location that are due to the dome-water interface. Data for the optical properties of seawater and various port materials are presented as well as a sample design.