Changes In Optical Performance Research Articles

Study on the optical properties of Sm3+ doped bismuth silicate crystals based on first principles

Abstract This study systematically investigated the effect of Sm3+ doping on the optical properties of bismuth silicate (Bi4Si3O12, abbreviated as BSO) crystals using first principles calculations based on density functional theory (DFT). By calculating the dielectric function, reflectivity, absorption coefficient, refractive index, conductivity, and energy loss function of BSO crystals under different Sm3+ doping ratios, we found that moderate Sm3+ doping can increase the dielectric function of BSO crystals, and the real part of the dielectric function represents the material’s ability to respond to the electric field, that is, the macroscopic polarization degree. Therefore, moderate Sm3+ doping enhances the polarization ability of BSO crystals. Simultaneously doping an appropriate amount can effectively enhance the conductivity and light (visible and infrared) absorption ability of BSO crystals, and reduce the energy loss between electrons in BSO crystals, thereby improving their luminescence performance. Specifically, when the Sm3+ doping ratio is 1/6, the optical properties of BSO crystals are significantly improved. These findings not only enhance the understanding of the mechanism of optical performance changes in rare earth ion doped BSO crystals, but also provide a theoretical basis for the development of new rare earth doped optical materials.

Investigating the effect of gravity on the optical performance of large-sized liquid crystal displays

This paper proposes a method to investigate the effect of gravity on optical performance of large-sized liquid crystal displays (LCDs). Combined with the finite element analysis and the LCD optical simulation, the change in optical performance of large-sized LCDs under the influence of gravity is analyzed. Compared with the condition without tilt angle, the Δu'v' is 0.025 in the bottom area of the 100-in LCD with the substrate thickness of 0.3 mm at a tilt angle of 1.5°, leading to a noticeable color shift. With the decrease of tilt angle or the increase of substrate thickness, the change in optical performance becomes unnoticeable and thus avoids the occurrence of visible display defect. Utilizing the proposed method, the assembly precision of large-sized LC panels can be calculated and the display defect caused by gravity can be effectively prevented.

Analyzing the effect of temperature on optical performance of dual‐layer liquid crystal displays

AbstractThe effect of temperature on optical performance of a dual‐layer liquid crystal display (LCD) is investigated by considering LC material parameter and structural deformation of LC panels simultaneously. First, the optical anisotropy of LC material under the influence of temperature is calculated theoretically. Then, the thermal deformations of the dual‐layer LC panels caused by temperature are simulated. Combined with the two factors, the change in optical performance of a dual‐layer LCD under the influence of temperature can be analyzed. In white state, the color in the central area of a dual‐layer LCD is shifted towards blue, and a yellowish border in the edge area may appear. In gray or black state, there may be a light leakage in the edge area of a dual‐layer LCD under the influence of temperature.

Differentiable scattering matrix for optimization of photonic structures

The scattering matrix, which quantifies the optical reflection and transmission of a photonic structure, is pivotal for understanding the performance of the structure. In many photonic design tasks, it is also desired to know how the structure's optical performance changes with respect to design parameters, that is, the scattering matrix's derivatives (or gradient). Here we address this need. We present a new algorithm for computing scattering matrix derivatives accurately and robustly. In particular, we focus on the computation in semi-analytical methods (such as rigorous coupled-wave analysis). To compute the scattering matrix of a structure, these methods must solve an eigen-decomposition problem. However, when it comes to computing scattering matrix derivatives, differentiating the eigen-decomposition poses significant numerical difficulties. We show that the differentiation of the eigen-decomposition problem can be completely sidestepped, and thereby propose a robust algorithm. To demonstrate its efficacy, we use our algorithm to optimize metasurface structures and reach various optical design goals.

A simple model for investigating the force–optical performance of LCDs

A simple model for investigating the optical performance of LCDs with respect to external forces is presented in this paper. Based on the continuum theory of a liquid crystal (LC) under an electric field, the simple model is established by adding the stress energy density term to Gibb’s free energy density. Besides, the change in cell gap due to external forces is also considered. The parameters in the model are determined by comparing the calculated results with the vertical tensile experiment data. After then, the tilting tensile experiment is performed to verify the simple model. In addition, the LC director distribution and optical performance changes are further discussed. The proposed model can help predict the possible change in the optical performance of LCDs in complex environments and save the product costs.

Characterization of laser thermal loading on microelectromechanical systems-based fast steering mirror in vacuum

Microelectromechanical systems (MEMS) have produced high-quality, high-bandwidth, small form factor, and inexpensive fast steering mirror (FSM) devices potentially suitable for a large variety of applications, such as image stabilization and beam pointing in satellite-based and ground-based, free-space optical communication systems. However, one outstanding question for this application is power handling. The absorption of the mirror substrate is low, but non-negligible, so the question remains of whether thermal loading from laser radiation on a MEMS mirror will deform its surface and, if so, to what extent. We show experimental results of optical performance changes due to thermal loading for MEMS two-axis FSM devices from Mirrorcle Technologies, Inc. Results and reproducible behavior are reported and compared in ambient versus vacuum conditions, where the benefits of convective cooling are absent. Finite element analyses corroborate the experimental results and show that the mirror substrate can deform due to thermal expansion imbalances. The deformation changes the focusing characteristics of the mirror, with a peak to valley defocus (second-order Zernike mode) of up to 50 nm when the mirrors are tested in ambient and up to approximately 450 nm when under vacuum. Such defocusing negatively impacts the link budget for laser-based satellite communications.

A simulation method for analyzing the effect of external forces on the optical performance of liquid crystal displays

A simulation method is proposed to analyze the effect of external forces on the optical performance of LCDs. The method consists of three steps: in the first step, the structure deformation of substrates under the influence of external forces is simulated. Secondly, the variations of electrode thickness are used to represent the structure deformation. Then, the force–optical performance of the LCD can be achieved. An experiment is performed to verify the proposed method. Besides, the LC director distribution and optical performance changes are discussed. The method can help predict the change in optical performance of LCDs in harsh environments.

Optical Performance of the Cornea One Year Following Keratoconus Treatment with Corneal Collagen Cross-Linking

ABSTRACT Purpose The purpose of the study is to assess changes in optical performance of the cornea in patients with keratoconus following treatment with corneal collagen crosslinking (CXL). Materials and Methods One hundred and eleven eyes of 111 consecutive keratoconus patients with 12-month follow-up after CXL were included. The changes in the visual acuity, manifest refractive errors, and corneal topographic parameters were evaluated. Sirius dual-scanning corneal tomography was used to determine the effectiveness of CXL on each patient’s total corneal optical quality; preoperative and 12-month postoperative measurements were analyzed over a 4-mm stimulated pupil and were compared with regards to higher order corneal aberrations (total amount of higher order aberrations [HOAs], vertical coma, horizontal coma, vertical trefoil, oblique trefoil, and spherical aberration), vertical and horizontal modulation transfer function (MTF), and Strehl ratio of point spread function (PSF). Results At 12 months, there was a significant improvement in mean uncorrected visual acuity (UCVA) (P < 0.001), best corrected visual acuity (BCVA) (P < 0.001), spherical equivalent refraction (P = 0.007), and manifest astigmatic refraction (P < 0.001). The corneal topographic measurements revealed a significant decrease in the mean simulated keratometry-1, simulated keratometry -2, and maximum keratometry compared with the baseline measurements (P < 0.001, for all). In addition, there were significant improvements in mean root mean square error values for corneal total HOA (P < 0.001), vertical coma (P < 0.001), and vertical trefoil (P = 0.008) following CXL. Mean MTF and Strehl ratio did not change after CXL (P > 0.05). The improvement in UCVA significantly correlated with the changes in vertical trefoil (r = −0.191, P = 0.044), and the improvement in BCVA and the changes in manifest astigmatic correction were also significantly correlated (r = −0.247, P = 0.009) 12 months after CXL. Conclusions CXL treatment for keratoconus led to an improvement in visual, refractive, topographic, and most corneal HOAs outcomes at the 12-month follow-up. However, these improvements were not enough to increase corneal MTF and the Strehl ratio of PSF.

Transparent block copolymer thin films for protection of optical elements via chemical vapor deposition

In this study, glycidyl methacrylate and 1H, 1H, 2H, 2H-perfluorodecyl acrylate copolymer p(GMA-co-PFDA) thin-films fabricated via Initiated Chemical Vapor Deposition (iCVD) were investigated as protective coatings on optical BK7 glass substrates and commercial optical filters. Durability tests based on military standards MIL-F-48616 and MIL-C-48497A were performed to evaluate performance of coatings for the protection of surfaces of optical elements. Cross-linked p(GMA-co-PFDA) copolymer coatings successfully passed all durability tests showing excellent mechanical properties and protection against humidity, salt water, swelling in water, and resistance to organic solvents while providing excellent adhesion to substrate. iCVD process enabled fine tuning of film morphology, mechanical properties and hydrophobicity by controlling the process parameters. Fabricated films were hydrophobic and highly transparent (>98%) in the wavelength range from 300 nm to 1000 nm. Optical transmittance measurements before and after coating process proved that while providing chemical and physical protection, p(GMA-co-PFDA) copolymer thin-films do not cause any detectable change in optical performance of commercial narrow band and wide band filters.

Optical performance of toric intraocular lenses in the presence of decentration.

To evaluate the optical performance of toric intraocular lenses (IOLs) after decentration and with different pupil diameters, but with the IOL astigmatic axis aligned. Optical performances of toric T5 and SN60AT spherical IOLs after decentration were tested on a theoretical pseudophakic model eye based on the Hwey-Lan Liou schematic eye using the Zemax ray-tracing program. Changes in optical performance were analyzed in model eyes with 3-mm, 4-mm, and 5-mm pupil diameters and decentered from 0.25 mm to 0.75 mm with an interval of 5° at the meridian direction from 0° to 90°. The ratio of the modulation transfer function (MTF) between a decentered and a centered IOL (MTFDecentration/MTFCentration) was calculated to analyze the decrease in optical performance. Optical performance of the toric IOL remained unchanged when IOLs were decentered in any meridian direction. The MTFs of the two IOLs decreased, whereas optical performance remained equivalent after decentration. The MTFDecentration/MTFCentration ratios of the IOLs at a decentration from 0.25 mm to 0.75 mm were comparable in the toric and SN60AT IOLs. After decentration, MTF decreased further, with the MTF of the toric IOL being slightly lower than that of the SN60AT IOL. Imaging qualities of the two IOLs decreased when the pupil diameter and the degree of decentration increased, but the decrease was similar in the toric and spherical IOLs. Toric IOLs were comparable to spherical IOLs in terms of tolerance to decentration at the correct axial position.

Precise Prediction of Optical Performance for Near Infrared Instrument Using Adaptive Fitting Line

Infrared optical systems are operated at low temperature and vacuum (LT-V) condition, whereas the assembly and alignment are performed at room temperature and non-vacuum (RT-NV) condition. The differences in temperature and pressure between assembly/alignment environments and operation environment change the physical characteristics of optical and opto-mechanical parts (e.g., thickness, height, length, curvature, and refractive index), and the resultant optical performance changes accordingly. In this study, using input relay optics (IO), among the components of the Immersion GRating INfrared Spectrograph (IGRINS) which is an infrared spectrograph, a simulation based on the physical information of this optical system and an actual experiment were performed; and optical performances in the RT-NV, RT-V, and LT-V environments were predicted with an accuracy of <TEX>$0.014{\pm}0.007{\lambda}$</TEX> rms WFE, by developing an adaptive fitting line. The developed adaptive fitting line can quantitatively control assembly and alignment processes below <TEX>${\lambda}/70$</TEX> rms WFE. Therefore, it is expected that the subsequent processes of assembly, alignment, and performance analysis could not be repeated.

Mechanistic modeling of vertebrate spatial contrast sensitivity and acuity at low luminance

The validity of the Barten theoretical model for describing the vertebrate spatial contrast sensitivity function (CSF) and acuity at scotopic light levels has been examined. Although this model (which has its basis in signal modulation transfer theory) can successfully describe vertebrate CSF, and its relation to underlying visual neurophysiology at photopic light levels, significant discrepancies between theory and experimental data have been found at scotopic levels. It is shown that in order to describe scotopic CSF, the theory must be modified to account for important mechanistic changes, which occur as cone vision switches to rod vision. These changes are divided into photon management factors [changes in optical performance (for a dilated pupil), quantum efficiency, receptor sampling] and neural factors (changes in spatial integration area, neural noise, and lateral inhibition in the retina). Predictions of both scotopic CSF and acuity obtained from the modified theory were found to be in good agreement with experimental values obtained from the human, macaque, cat, and owl monkey. The last two species have rod densities particularly suited for scotopic conditions.

Interaction between aberrations to improve or reduce visual performance

Purpose To investigate how pairs of Zernike modes interact to increase or decrease visual acuity. Setting Visual Optics Institute, College of Optometry, University of Houston, Houston, Texas, USA. Methods Subjects read aberrated and unaberrated visual acuity charts 3 times. Each aberrated chart was produced by convolving an aberrated point-spread function with an unaberrated acuity chart. Point-spread functions were defined by 4 pairs of Zernike modes. For each pair, 9 combinations were used, ranging from all aberration being loaded into the first mode to all aberration being loaded into the second mode. The root mean square (RMS) wavefront error always totaled 0.25 μm (6.0 mm pupil), a level similar to the aberration induced by traditional flying small-spot laser refractive surgeries. Results For all conditions (except the unaberrated charts), visual acuity decreased. Acuity varied significantly depending on which modes were mixed and the relative contribution of each mode. Modes 2 radial orders apart and having the same sign and angular frequency tended to combine to increase visual acuity. Modes within the same radial order tended to combine to decrease acuity. Conclusions For low levels of aberration, the RMS wavefront error is not a good predictor of visual acuity. Clinically, it is important to define how aberrations interact to optimize visual performance. New metrics of optical/neural performance that correlate better with clinical measures of visual performance need to be adopted or developed, as well as new clinically viable measures of visual performance that are sensitive to subtle changes in optical performance.

Optical performance of decentered bifocal contact lenses.

Contact lenses frequently do not center over the pupil. The potential changes in optical performance introduced by poor centration of bifocal contact lenses have only been described previously from theoretical considerations. The present study measured the modulation transfer function (MTF) of rigid concentric-design refractive and rigid diffractive bifocal contact lenses with varying apertures and amounts of decentration. Decentration was shown to have a greater effect on the MTF of the refractive than on the MTF of the diffractive bifocals. The MTF of the refractive bifocals was related to the proportion of the aperture covered by the central optic zone (COZ). Unexpectedly, the MTF of the distance focus of the diffractive bifocal contact lenses was reduced at moderately high spatial frequencies. The practitioner should be aware of the effects of decentration of bifocal contact lenses.