Pupil Position Research Articles

Real-Time Facial and Eye Gaze Tracking System

The goal of gaze detection is to locate the position (on a monitor) where a user is looking. Previous researches use one wide view camera, which can capture the user's entire face. However, the image resolution is too low with such a camera and the fine movements of user's eye cannot be exactly detected. So, we propose the new gaze detection system with dual cameras (a wide and a narrow view camera). In order to locate the user's eye position accurately, the narrow-view camera has the functionalities of auto focusing/panning/tilting based on the detected 3D eye positions from the wide view camera. In addition, we use the IR-LED illuminators for wide and narrow view camera, which can ease the detecting of facial features, pupil and iris position. To overcome the problem of specular reflection on glasses by illuminator, we use dual IR-LED illuminators for wide and narrow view camera and detect the accurate eye position, which is not hidden by the specular reflection. Experimental results show that the gaze detection error between the computed positions and the real ones is about 2.89 cm of RMS error.

Information extraction from image sequences of real-world facial expressions

Information extraction of facial expressions deals with facial-feature detection, feature tracking, and capture of the spatiotemporal relationships among features. It is a fundamental task in facial expression analysis and will ultimately determine the performance of expression recognition. For a real-world facial expression sequence, there are three challenges: (1) detection failure of some or all facial features due to changes in illumination and rapid head movement; (2) nonrigid object tracking resulting from facial expression change; and (3) feature occlusion due to out-of-plane head rotation. In this paper, a new approach is proposed to tackle these challenges. First, we use an active infrared (IR) illumination to reliably detect pupils under variable lighting conditions and head orientations. The pupil positions are then used to guide the entire information-extraction process. The simultaneous use of a global head motion constraint and Kalman filtering can robustly track individual facial features even in condition of rapid head motion and significant expression change. To handle feature occlusion, we propose a warping-based reliability propagation method. The reliable neighbor features and the spatial semantics among these features are used to detect and infer occluded features through an interframe warping transformation. Experimental results show that accurate information extraction can be achieved for video sequences with real-world facial expressions.

What not to wear and other stories: addressing religious diversity in schools

This article considers the position of religion in schools in England and Wales in light of the recent decision in The Queen on the application of SB v Headteacher and Governors of Denbigh High School. This held that the refusal to allow a pupil to wear the jilbab was a breach of her rights under the European Convention for the Protection of Human Rights and Fundamental Freedoms 1950 and the Human Rights Act 1998. It contrasts approaches based on human rights principles with those based on discrimination law principles, highlighting overlap and inconsistency between both the definitions applicable to different forms of discrimination and the position of teachers and pupils. It concludes that the law is in urgent need of rationalisation to provide consistency.

The Pupil is a Moving Target: Centration, Repeatability, and Registration

To evaluate the ability to accurately center and register wavefront data to provide effective custom wavefront application for vision correction. Centration images were obtained of 40 undilated pupils at 5 different illumination levels using the Alcon LADARWave aberrometer (Alcon Laboratories Inc, Fort Worth, Tex). Pupil position relative to the limbus was determined for all eyes under all levels of illumination. Variability in centration of the pupil was based on difference in magnitude of offset between pupil center and limbal center. Human operators were compared to a computerized limbus recognition system through repeatability testing using 10 different images of one eye of a single patient. As determined by human operators, the pupil center in undilated pupils shifted a mean of 175 microm between the lowest level and the highest level of illumination (range 34 to 335 microm [standard deviation 84 microm]). Repeatability testing suggests human measurements can accurately position the pupil to within approximately 50 microm using current technology. Computer image processing using limbus recognition software appears equal or superior to manual pupil centration. The pupil center can have a significant change in position with changing illumination. Wavefront data must be centered on a fixed eye structure rather than the pupil center to ensure that wavefront data captured in scotopic light are appropriately matched to the pupil in the photopic light used at surgery. The goal is to avoid clinically significant decentration of the wavefront between capture and excimer laser application.

Teacher–Pupil Talk in Whole-class Discussions and Processes of Social Positioning within the Primary School Classroom

The shape and form of effective teacher–pupil talk has recently become the focus of attention within policy guidelines such as the National Numeracy and Literacy Strategies. Prior to this, research on classroom discourse has established that social context plays an important role in determining the quality of teacher–pupil talk since it directs teachers' and pupils' interpretations of what is said. This paper presents a multi-layered approach to the analysis of whole-class discussions which highlights the impact of wider, institutional and historical aspects of the classroom context on the meanings relayed within interactions. Video and audio data, collected over a five-month period of participant observation in a primary school mathematics classroom, highlights how issues such as teacher expectations and time pressure influence the quality of interactions pupils experience. The paper concludes that teacher–pupil interactions play an instrumental role in determining the social positioning of pupils within the classroom and this has a profound effect on the pupil's access to the learning process. In light of such findings, the potential limitations of establishing and implementing guidelines on effective teacher–pupil talk within policy are discussed.

Laser Doppler instrument to investigate retinal neural activity-induced changes in optic nerve head blood flow

A fundus camera-based instrument to investigate increased retinal neuronal activity effect on optic nerve blood flow is described. It incorporates (a) near infrared fundus illumination and observation, (b) near infrared laser Doppler flowmeter (LDF), (c) pupil position monitoring and (d) delivery of visual stimuli. Two types of stimulation are currently used: diffuse heterochromatic and chromatic luminance flicker generated by light emitting diodes, and contrast reversal pattern displayed on a video monitor. Recordings of the changes in the LDF parameters (blood velocity, volume and flow) from the optic nerve in response to these stimuli illustrate the potential of the technique.

Aberrational properties of an optical system composed of two reflective spherical surfaces with a compensator

Relationships have been obtained that determine the position of the entrance pupil of an optical system made from two reflective spherical surfaces for which the third-order coma equals zero, depending on the central screening over the pupil diameter. A basis is thus provided for achieving aplanatic correction of the aberrations by bringing one of the surfaces of a plane-parallel plate into coincidence with the plane of the entrance pupil and imparting a quasi-planoidal shape to it, and the sequence is given for designing it. It is shown that planastigmatic correction of the aberrations is possible. © 2004 Optical Society of America

On the necessity to change the educational system

The reform of education has always been an essential issue because it affects almost each element of the area. The paper discusses reforms with regard to the tasks schools will face in the future, including the position of teachers and pupils. The author considers basic tendencies of reform, emphasising the changes in teacher's work. The question of the school reform is seen as a permanent process that is connected with complex social, scientific and technological changes.

Correction for near vision in pseudophakic patients

Objective of the study was to show the mean values of correction for near vision and to discuss the presbyopic correction in pseudophakic patients. Setting was the Eye department where authors work. Inclusion criteria for 55 patients were native or corrected distant vision of 0.8-1.0 on Snellen's chart; 0,6 on Jagger's chart for near vision; round pupil and good position of the implant. Biometry of the anterior chamber depth with Alcon biophysics during distant and near vision was performed in our study. "Hi square" test was carried out and it was concluded that patients younger than 59 years (41 eyes) had median correction of +2.0 dsph, while patients older than 60 years (36 eyes) had correction of +3.0 dsph, but it was not statistically significant. There was no statistically significant difference of the correction between pseudophakic (41) and phakic (19) eyes in patients younger than 59 years. The anterior movement of the IOL was 0.18 mm in the younger group and 0.15 mm in the older group. With good IOL movement and new materials which could have changeable refractive power, the problem of pseudophakic correction for near vision might be solved.

Judgment, interpretation and impression of gaze direction in an Ukiyo‐e picture1,2

Abstract: We examined the judgment, interpretation and impression of gaze directions of figures5 in an Ukiyo‐e picture and its compositional variations. In those pictures, figures’ gaze directions were ambiguous because of their eyes drawn by thin lines (Hiki‐me). Observers had to judge gaze directions of the figures by cues other than the positions of pupils. The results showed that gaze directions of the figures were judged as a result of information integration of the natural cues of gaze directions and contextual cues in the scene. The object that was paid attention to by the figures as well as the head directions and compositional arrangements of the figures affected the judgment of gaze directions. We especially noted the composition of the figures viewing the object together side‐by‐side. In this composition, the judgment of gaze direction and the impression of a figure dramatically changed depending on the presence or absence of the commonly viewed object by the figures. We will discuss the results from the point of view of attention allocation and information integration as well as sociocultural background.

A noninvasive eye fixation and computer-aided eye monitoring system for linear accelerator–based stereotactic radiotherapy of uveal melanoma

Purpose To introduce a noninvasive eye fixation and computer-aided eye monitoring system for linear accelerator-based stereotactic radiotherapy for uveal melanoma. Methods and materials At the Department of Radiotherapy and Radiobiology, University of Vienna, stereotactic radiotherapy is offered to patients with uveal melanoma considered unsuitable for 106Ru brachytherapy or local resection. For the present feasibility study, 8 patients were carefully selected according to their ability to fixate a small light source with the diseased eye and whether they had a rather small head to meet the limited geometric space available. A polymethyl methacrylate tube was attached to a stereotactic mask system in craniocaudal orientation supporting a 45° mirror, which was placed in front of the diseased eye. At the other end of the tube, the patient was given a small fixation light, and a small camera was positioned beneath, which was shielded for use during MRI. A computer interface calculated and visualized the spatial difference of the actual and a given reference pupil position, which was defined before CT scanning, during the MRI sequences, and during treatment delivery at the linear accelerator. Results The described system can be attached to a conventional stereotactic mask system with minor modifications. Because of the large distance between the eye and the fixation light, the optical fixation system was well tolerated by all patients, and a stable position of the eye was obtained. The camera system can be used during CT and MRI without interference. Absorption of the 6-MV photon beam by the mirror and the polymethyl methacrylate tube was negligible. The computer interface designed to determine the pupil position uses an image-processing algorithm that correlates a template of the reference image with the actual image of the eye. Provided sufficient illumination of the pupil, the correlation function showed a pronounced minimum at the reference position. The precision of the algorithm was tested by phantom measurements. For a given 1 mm or 2 mm displacement, the interface reported a mean shift of 0.96 ± 0.18 mm or 2.07 ± 0.11 mm, respectively. Conclusion The results of this study demonstrated the feasibility of a new optical fixation system for linear accelerator-based stereotaxis. The artifact-free application of the camera system during image acquisition and irradiation and the use of the computer interface, which automatically monitored eye movements with submillimeter precision, provided large improvements compared with existing techniques. Given well-defined interruption criteria and accelerated image processing, the described system has a high potential to perform automatically gated treatment beam delivery in the near future.

Image size magnification and power and dilation factors for optical instruments in general.

Traditional treatments of spectacle magnification for distant objects consider only stigmatic spectacle lenses and they compare the retinal image size in a refractively fully compensated eye with the image size in the uncompensated eye. Spectacle magnification is expressed as a product of two factors, the power and shape factors of the lens. The power factor depends on the position of the entrance pupil of the eye. For an eye with an astigmatic cornea, however, the position of the entrance pupil is not well defined. Thus, the traditional approach to spectacle magnification does not generalize properly to allow for astigmatism. Within the constraints of linear optics and subject to the restriction that the eye's iris remains the aperture stop, this paper provides a complete, unified and exact treatment for optical instruments in general. It compares retinal image size in a generalized sense (including image shape and orientation) for any instrument in front of an eye with that of the eye alone irrespective of whether the instrument compensates or not. The approach does not make use of the concept of the entrance pupil at all and it allows for astigmatism and for non-alignment of refracting elements in the instrument and in the eye. The concept of spectacle magnification generalizes to the concept of instrument size magnification. Instrument size magnification can be expressed as the product of two matrix factors one of which can be interpreted as a power factor (as back-vertex power) and the other factor for which the name dilation factor is more appropriate in general. The general treatment is then applied to a number of special cases including afocal instruments, spectacle lenses (including obliquely crossing thick bitoric lenses), contact lenses, stigmatic systems and stigmatic eyes. In the case of spectacle lenses, the dilation factor reduces to the usual shape factor.

An Image Slicer Integral Field Unit with Diffraction‐limited Performance for Three‐Dimensional Imaging Spectroscopy

ABSTRACTWe have designed and constructed an advanced image slicer (AIS) integral field unit (IFU). The IFU employs an all‐mirror design and will be installed in the Penn State near‐IR Imager and Spectrograph (PIRIS) for three‐dimensional integral field spectroscopy at various astronomical telescopes. Using the AIS technique, the slicer IFU can preserve the telescope’s focal ratio and pupil (both position and size) while maximizing the packing efficiency for three‐dimensional data on the detector. Compared to other existing AIS IFU designs, our design, which uses monolithic optical components for both pupil and field mirror arrays, provides a convenient engineering solution for manufacturing, using the state‐of‐the‐art diamond‐turning machines and alignment of the IFU optics. Our slicer mirror array was also manufactured by diamond turning, with all the mirrors simultaneously machined, which also simplifies the procedure for the manufacture and the assembly of the mirrors. We present the IFU optical description, component test results, and overall IFU system performance. We also discuss possible science applications using the IFU.

Ocular aberrations with ray tracing and Shack-Hartmann wave-front sensors: does polarization play a role?

Ocular aberrations were measured in 71 eyes by using two reflectometric aberrometers, employing laser ray tracing (LRT) (60 eyes) and a Shack-Hartmann wave-front sensor (S-H) (11 eyes). In both techniques a point source is imaged on the retina (through different pupil positions in the LRT or a single position in the S-H). The aberrations are estimated by measuring the deviations of the retinal spot from the reference as the pupil is sampled (in LRT) or the deviations of a wave front as it emerges from the eye by means of a lenslet array (in the S-H). In this paper we studied the effect of different polarization configurations in the aberration measurements, including linearly polarized light and circularly polarized light in the illuminating channel and sampling light in the crossed or parallel orientations. In addition, completely depolarized light in the imaging channel was obtained from retinal lipofuscin autofluorescence. The intensity distribution of the retinal spots as a function of entry (for LRT) or exit pupil (for S-H) depends on the polarization configuration. These intensity patterns show bright corners and a dark area at the pupil center for crossed polarization, an approximately Gaussian distribution for parallel polarization and a homogeneous distribution for the autofluorescence case. However, the measured aberrations are independent of the polarization states. These results indicate that the differences in retardation across the pupil imposed by corneal birefringence do not produce significant phase delays compared with those produced by aberrations, at least within the accuracy of these techniques. In addition, differences in the recorded aerial images due to changes in polarization do not affect the aberration measurements in these reflectometric aberrometers.

A new data processing and calibration method for an eye-tracking device pronunciation system

In this paper, a new data processing and calibration method for a pronunciation system of an eye-tracking device is described. The eye-tracking device was created using both head mounted display (HMD) technology and remote operation capabilities. A pattern recognition computer program was used to distinguish the pupil position and calculate its coordinates. This system can be adapted to provide a digital speech function. A new method for processing the image of the eye in the PC-based system was also developed. With one video CCD camera and frame grabber analyzing a series of human pupil images while the subject is gazing at the screen, an auto-calibration algorithm is used to obtain the direction of the eye gaze in real time. The computers provide the speech sound according to the location where the eye gazes exceed 0.5 s . The availability of multipurpose in this eye-tracking system with very simple equipment will be reconfirmed for future advanced research.

An eye behavior measuring device for VR system

This work presents an eye-tracking and pupil size-measuring device that interfaces with a computer for applications useful in psychometry, ophthalmology, physiology and virtual reality (VR) systems. This system utilizes a change-coupled device (CCD) camera, appropriate lenses, PC with frame grabber and a DSP unit with various types of VR equipment, i.e., HMD, simulator or LCD projection device. The digital signal processing unit is used to calculate the average brightness and contrast of the VR video image. A CCD camera with various attachments can be mounted on various VR systems to capture the human eye image for testing. An image capture card and a personal computer are used to analyze the test image. From the eye digital image, the computer obtains data on the pupil size and a trace of the tested eye. A pattern recognition computer program and five measurement parameters are used to distinguish the position of the pupil, calculate the pupil location coordinate and analyze the physical conditions of the user. These data can be plotted against the average brightness and contrast of the VR video image in real time. This information is shown on the screen of a personal computer and used for cross-link analysis. This eye-tracking interface can determine the position of a subject's pupil and map that position into a display point on a computer screen. The pupil size and location data versus the average brightness and contrast of a VR video image are computed in real time.

English Title Not Available [Turkish title: SPORLA ILGILI MESLEKLERE YONELMEDE SOSYO-EKONOMIK SINIFSAL POZISYONUN ONEMI: H.U. SPOR BILIMLERI VE TEKNOLOJISI YUKSEK OKULU ORNEGI

The socio-cultural factors are are also functional during the socialization process in sports. Very much data are indicating that, to have an interest in sports as a hobby or to select sports as an occupation, has an interaction with the socio-economic background. In this respect the goal of this research is to determine the influences of the socio-economic positions of the pupils\' families to their occupational orientations. This simple is chosen by random sampling method. The results of the research are held by survey research methods and are evaluated by SPSS programme. The data are showing that there is a correlated relationsbetween the occupational orientations in sports and the socio-class position.

Ray aberration for a biaxial holographic imaging system

In revolution-symmetrical optical systems design, it is usual to extract information of aberrations from ray tracing of selected rays. In this work, we generalise the relationship between ray aberration and wave aberration for a biaxial imaging system that includes holographic optical elements (HOEs); both for conjugate planes perpendicular to optical axis or parallel to lens plane. We study the pattern of the light distribution at image plane produced by each aberration term, showing similarities and differences with those of revolution-symmetrical systems. We describe a practical procedure to complete characterisation of the imaging performance of biaxial optical systems including HOEs, by tracing only six rays. The principal advantage of this procedure is that we can obtain experimentally the aberration coefficients at the output of any imaging system including biaxial holographic elements. We show that aberration coefficients obtained from ray tracing have a good coincidence with those predicted by third-order approximation. We apply our procedure to pupil position optimisation in a holographic lens.

Decentration after refractive surgery.

To examine factors useful in evaluation of suspect decentration after refractive surgery. We evaluated 148 cases (eyes) referred to us for recentering procedures by review of information obtainable by evaluation of pupil position, corneal topography, and corneal curvature gradient. Only a minority of eyes (n=5, 3.4%) were truly decentered; in the remaining majority a high dioptric gradient with consequent focal scarring was present (n=107, 72.3%). In 28 eyes (18.9%), a drifting of the eye during treatment was responsible, and in eight eyes (5.4%), a central island was observed. Proper corneal topographical diagnosis reduces the risk of improperly suspecting decentration, and for most cases, smoothing of the central cornea is a simple and efficacious solution. Recommendations for the prevention of decentration include proper patient positioning, special care in treating high myopes, preoperative check of pupil displacement nasally, evaluation of preoperative map with detection of high temporal curvature gradient, and use of the cross-cylinder technique in the treatment of astigmatism.

Cognitive Style, Home Background and Conduct Behaviour in Primary School Pupils

The class teachers of 109 9-10-year-old (Year 4/5) and 10-11-year-old (Year 5/6) primary school pupils were asked to rate the classroom conduct behaviour and home background of their pupils on five-point scales from very poor through to very good. This was done during the Summer term and repeated by the new teachers of the classes during the following Autumn term of the next school year. The measures were then taken as the means of the two ratings. The position of pupils on the Wholist-Analytic cognitive style dimension was assessed by means of the Cognitive Styles Analysis. There was a significant effect of WholistAnalytic style on behaviour with the Wholists being the worst behaved. There was also an interaction between Gender and Home Background with the females behaving better than the males, and this being most pronounced when the Home Background was rated as poor. The results were discussed in terms of their implications for teaching and parenting, and their similarities to studies of pupils at the secondary level.