共查询到20条相似文献,搜索用时 46 毫秒
1.
We report on an implementation of coherence revival-based heterodyne swept source optical coherence tomography that is capable of simultaneously imaging the anterior and posterior eye. A polarization-encoded sample arm was used to efficiently focus orthogonal polarizations on the anterior segment and retina. Depth encoding was achieved using coherence revival, which allows for multiple depths within a sample to be simultaneously imaged and frequency encoded by carefully controlling the optical pathlength of each sample path. This design is a significant step toward whole-eye optical coherence tomography (OCT), which would enable customized ray-traced modeling of patient eyes to improve refractive surgical interventions and eliminate optical artifacts in retinal OCT diagnostics. We demonstrated the feasibility of this system for in vivo imaging by simultaneously acquiring images of the anterior segments and retinas in healthy human volunteers. 相似文献
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The visual system tends to favour one eye over the other in perceptual or motor tasks. This effect, called ocular dominance, makes those small movements in one eye be smaller and more precise than in the other eye. These dynamic effects are usually small and static devices are not capable of detecting differences between both eyes. In the last years ophthalmic devices are becoming more and more precise, thus they can be sensible to such variability. The hypothesis posed here is that variability of measures acquired this way is affected by ocular dominance. With a Pentacam system we have measured several parameters of the anterior segment of the eye. Our findings show that variables measured for the dominant eye are less dispersive than for the non-dominant eye although the limited accuracy of the device can mask this effect. The trend is confirmed by a contrast experiment and by a previous work, so we accept the validity of our hypothesis. Our main conclusion is that systematic election of the right eye in analysis of reliability or reproducibility can bias the variability of results and consequently we suggest considering dominance effects. 相似文献
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Saito K Obata T Hirono K Iwasawa T Yoshida T Matsubara S 《Magnetic resonance imaging》2000,18(3):357-360
The O(2) suppression effect of a soft contact lens on the human cornea was measured using dynamic magnetic resonance imaging (MRI) of the anterior chamber transcorneally exposed to O(2). Dynamic T(1)-weighted fast spin echo imaging of anterior chambers (TR = 2 s, TE = 15 ms, 5-mm slice) was performed both before and during oxygen supply to a full goggle placed on the face of volunteers wearing a soft contact lens on one eye and nothing on the other eye as a control. Within 15 min after O(2) administration, significantly lower intensity changes were obtained in the anterior chambers of the eyes with the contact lens than in those of the eyes without one, suggesting that dynamic MRI of the anterior chamber transcorneally exposed to O(2) can be used to evaluate the O(2) suppression effect of a soft contact lens on the cornea. 相似文献
5.
We tested the effects on laser ablation of reflection losses and nonnormal incidence on the anterior cornea. We measured presurgical and postsurgical corneal asphericity in 94 myopic eyes, comparing it with the corneal asphericity predicted by the Munnerlyn formula, modified or not, with an adjustment factor that takes into account the two effects mentioned above. The predictive power of the experimental results was stronger when we considered the adjustment factor. We propose to modify ablation algorithms by taking this adjustment factor into account, especially in customized corneal ablation, which needs high accuracy for correcting eye aberrations. 相似文献
6.
The Estimation of Multiple Light Scattering in Turbid Colloidal Suspensions using a 2-Probe Detector
Gary Bryant Hugo Schotman John C. Thomas 《Particle & Particle Systems Characterization》1998,15(4):170-173
This paper describes a detector for the direct measurement of multiple scattering in moderately turbid colloidal suspensions. The detector uses two optical fibers aligned so that one of the fibers measures the total signal (single and multiple scattering) and the other measures multiple scattering only. We report the results of preliminary investigations, and show how such a detector can be used to aid both static and dynamic light scattering investigations. In the former case we show how this information can be used to correct for low level multiple scattering. The utility and limitations of the technique are discussed. 相似文献
7.
We present a novel algorithm for full-range imaging by suppression of the complex conjugate artifact in phase-shifting Fourier domain optical coherence tomography. This technique utilizes the projection of multiple phase-shifted interferograms onto an orthogonal basis set to reconstruct the complex interferogram. Full-range imaging with >30 dB suppression of the symmetric artifact is demonstrated using a 3 x 3 fiber coupler swept source OCT system, providing a depth range of 6.6mm with -8 dB roll-off in sensitivity at the depth boundaries relative to DC. Real-time display of full-range images of the anterior segment of the human eye acquired in vivo at a line rate of 6.67 kHz are presented. 相似文献
8.
Mehdi Baneshi Shigenao Maruyama Atsuki Komiya 《Journal of Quantitative Spectroscopy & Radiative Transfer》2009,110(3):192-84
Pigmented coatings with high reflectivity against solar irradiation can be used to control unwanted thermal heating that occurs as materials absorb sunlight such as heat in buildings that increases cooling loads. However, these surfaces produce glare that is unpleasant to the eye, and the coatings themselves can damage the appearance of the coated object. We introduce a new optimization method that embraces both thermal and aesthetic requirements. Our proposed coatings maximize the reflectivity of the near infrared (NIR) region to reduce thermal heating, while for aesthetic appeal they also minimize the visible (VIS) reflected energy received by human eyes, especially at wavelengths where eye sensitivity is high. The optimization parameter is defined as the ratio of the total reflected energy in the NIR region to that in the VIS region weighted by human eye sensitivity. Titanium dioxide is used as the pigment, and databases of its radiative properties are constructed using the Mie theory. To compute reflectivity, nongray radiative heat transfer in an anisotropic scattering monosized pigmented layer, with independent scattering, including direct and diffuse solar irradiations, is analyzed using radiation element method by ray emission model (REM2). Colors are calculated and optimization parameter is evaluated by using spectral reflectivity. Finally, the optimum values of particle size, volume fraction of pigment, and coating thickness are obtained. 相似文献
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It is well recognised that metals, especially iron, will cause artifacts in magnetic resonance (MR) images. Hitherto it has not been recognised that some facial cosmetics contain magnetic materials, in sufficient quantities to cause artifacts. We report a case of a 25-year-old female who had MR images of her orbits made while wearing mascara eye makeup. The resultant images showed distortion of the signal over the anterior aspect of both eyes. Examination following the removal of the eye makeup resulted in the acquisition of normal images. The typical ingredients of mascara are natural and synthetic waxes, glycerine, water, kaolin, preservatives, polymer film formers and pigments. A wide range of pigments may be used, especially iron oxide, which is a constituent of both brown and blue mascara. In addition it is likely that a number of mascaras will be contaminated with heavy metals. As a result of this observation we now ensure that all patients who are undergoing MR imaging of the head, remove all facial cosmetics as well as any jewelry prior to imaging. 相似文献
11.
We present the design of a non-conventional optical system that uses cylindrical micro-doublets (CMD), integrated in an artificial
apposition compound eye configuration (AACE). We show some designs of an ultra-thin objective inspired in fly eyes. These
designs can give options to create new technologies that will process information in a different and effective way as usual.
This process will be carried out by means of sampling the object with an array of multiple micro lenses using a certain value
of the acceptance angle, and processing the optical signal to obtain partial images that will be part of a global one. The
objective has the advantage of having a smaller size, a wider field of view, and an acceptable image quality compared with
some conventional systems. Design parameters of the AACE and optical performance of the CMD are reported. 相似文献
12.
Jorge Pérez 《Optik》2005,116(2):49-57
We present a new modelization technique of the human eye based on the calculation of light distributions inside the eye. The method is applied to the study of the crystalline model proposed by Kasprzak and Popiolek. We obtain corneal surface data and axial lengths for two groups of real eyes. With these data, we construct a diffractive model of a human eye, which permits calculation of propagated light distributions at any distance inside the eye. The real crystalline lens is substituted by Kasprzak's model, thus obtaining a realistic model eye. From calculated patterns, we obtain the Strehl ratio and the modulation transfer functions of 44 eyes, divided in two groups according to the age. We compare our results with those in the bibliography. Finally, we check the performance of the method through individual comparison of the calculated image positions with respect to the retina with the refractive data for the each subject. We have observed good agreement between our method and results from other authors. We also find reasonable correlation between calculated refraction and subjective exams. 相似文献
13.
Tatsuo Yamaguchi Naoki Nakazawa Kenichiro Bessho Yoshiyuki Kitaguchi Naoyuki Maeda Takashi Fujikado Toshifumi Mihashi 《Optical Review》2008,15(3):173-180
We have developed an adaptive optics (AO) fundus camera to obtain high resolution retinal images of eyes. We use a liquid
crystal phase modulator to compensate the aberrations of the eye for better resolution and better contrast in the images.
The liquid crystal phase modulator has a wider dynamic range to compensate aberrations than most mechanical deformable mirrors
and its linear phase generation makes it easy to follow eye movements. The wavefront aberration was measured in real time
with a sampling rate of 10 Hz and the closed loop system was operated at around 2 Hz. We developed software tools to align
consecutively obtained images. From our experiments with three eyes, the aberrations of normal eyes were reduced to less than
0.1 μm (RMS) in less than three seconds by the liquid crystal phase modulator. We confirmed that this method was adequate
for measuring eyes with large aberrations including keratoconic eyes. Finally, using the liquid crystal phase modulator, high
resolution images of retinas could be obtained. 相似文献
14.
Tkaczyk ER Mauring T Pajusalu M Anijalg A Tkaczyk AH Teesalu P Kikas J Mauring K 《Optics letters》2011,36(23):4707-4709
We present a portable optical cataract assessment technology which measures with a circular photodetector the fraction of light scattered backwards by the human eye lens when illuminated by a laser diode. As our signal arises directly from the fundamental pathology-increased scattering in the lens-it directly assesses cataract extent and progression. Initial clinical results in undilated human eyes show device reading correlations in agreement with clinical examination and Scheimpflug photography. 相似文献
15.
Palmer AD Griffiths R Styles I Claridge E Calcagni A Bunch J 《Journal of mass spectrometry : JMS》2012,47(2):237-241
Sucrose is used as a cryo-preservation agent on large mammalian eyes post formalin fixation and is shown to reduce freezing artefacts allowing the collection of 12-μm thick sections from these large aqueous samples. The suitability of this technique for use in MALDI imaging experiments is demonstrated by the acquisition of the first images of lipid distributions within whole sagittal porcine eye sections. 相似文献
16.
We provide the first evidence that stochastic resonance within the human brain can enhance behavioral responses to weak sensory inputs. We asked subjects to adjust handgrip force to a slowly changing, subthreshold gray level signal presented to their right eye. Behavioral responses were optimized by presenting randomly changing gray levels separately to the left eye. The results indicate that observed behavioral stochastic resonance was mediated by neural activity within the human brain where the information from both eyes converges. 相似文献
17.
Chern-Sheng Lin Chia-Chin Huan Chao-Ning Chan Mau-Shiun Yeh C.-C.Chuang-Chien Chiu 《Optics and Lasers in Engineering》2004,42(1):457
An eye mouse interface that can be used to operate a computer using the movement of the eyes is described. We developed this eye-tracking system for eye motion disability rehabilitation. When the user watches the screen of a computer, a charge-coupled device will catch images of the user's eye and transmit it to the computer. A program, based on a new cross-line tracking and stabilizing algorithm, will locate the center point of the pupil in the images. The calibration factors and energy factors are designed for coordinate mapping and blink functions. After the system transfers the coordinates of pupil center in the images to the display coordinate, it will determine the point at which the user gazed on the display, then transfer that location to the game subroutine program. We used this eye-tracking system as a joystick to play a game with an application program in a multimedia environment. The experimental results verify the feasibility and validity of this eye-game system and the rehabilitation effects for the user's visual movement. 相似文献
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In eye movement research in reading, the amount of data plays a crucial role for the validation of results. A methodological problem for the analysis of the eye movement in reading are blinks, when readers close their eyes. Blinking rate increases with increasing reading time, resulting in high data losses, especially for older adults or reading impaired subjects. We present a method, based on the symbolic sequence dynamics of the eye movements, that reconstructs the horizontal position of the eyes while the reader blinks. The method makes use of an observed fact that the movements of the eyes before closing or after opening contain information about the eyes movements during blinks. Test results indicate that our reconstruction method is superior to methods that use simpler interpolation approaches. In addition, analyses of the reconstructed data show no significant deviation from the usual behavior observed in readers. 相似文献
20.
Annular objective apertures are fabricated for a CM300 transmission electron microscope using a focused ion beam system. A central beam stop in the back focal plane of the objective lens of the microscope blocks all electrons scattered up to a semi-angle of approximately 20 mrad. In this manner, contributions to the image from Bragg scattering are largely reduced and the image contrast is sensitive to the atomic number Z. Experimentally, we find that single atom scattering cross sections measured with this technique are close to Rutherford scattering values. A comparison between this new method and STEM-HAADF shows that both techniques result in qualitatively similar images although the resolution of ADF-TEM is limited by contrast delocalization caused by the spherical aberration of the objective lens. This problem can be overcome by using an aberration corrected microscope. 相似文献