Optical, Electrical, Structural, and Thermo-Mechanical Properties of Undoped and Tungsten-Doped Vanadium Dioxide Thin Films.

The undoped and tungsten (W)-doped vanadium dioxide (VO2) thin films were prepared by electron beam evaporation associated with ion-beam-assisted deposition (IAD). The influence of different W-doped contents (3-5%) on the electrical, optical, structural, and thermo-mechanical properties of VO2 thin films was investigated experimentally. Spectral transmittance results showed that with the increase in W-doped contents, the transmittance in the visible light range (400-750 nm) decreases from 60.2% to 53.9%, and the transmittance in the infrared wavelength range (2.5 µm to 5.5 µm) drops from 55.8% to 15.4%. As the W-doped content increases, the residual stress in the VO2 thin film decreases from -0.276 GPa to -0.238 GPa, but the surface roughness increases. For temperature-dependent spectroscopic measurements, heating the VO2 thin films from 30 °C to 100 °C showed the most significant change in transmittance for the 5% W-doped VO2 thin film. When the heating temperature exceeds 55 °C, the optical transmittance drops significantly, and the visible light transmittance drops by about 11%. Finally, X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to evaluate the microstructure characteristics of VO2 thin films.

The influence of large-diameter multifocal contact lens on ocular surface, visual quality, and visual function for presbyopic adults with dry eye syndromes.

This study investigated the influence of large-diameter multifocal contact lenses on the ocular surface, visual quality, and visual function for presbyopic adults with dry eye syndromes. The study enrolled 40-55-year-old adults with presbyopia and dry eye syndromes (DES). The subjects were randomly assigned to three groups wearing different designs of contact lenses (Proclear, SMR, and Optimum) for 6-8 h a day for two weeks. Ocular surface health, tear quality, visual quality, and visual function were measured before and after lens wear. No significant difference was observed across all three groups for the amount of conjunctival redness, blink frequency (lens on), and stereopsis vision before and after wearing. Although there seemed to be a significant declining trend for corneal staining and limbal redness, non-invasive tear break-up time (TBUT), and lipid layer thickness while lens wear, the measured values were all within the normal range. Vice-versa after lens removal, results also showed significant improvement on lipid layer thickness, blink frequency (lens off), and contact TBUT. A significant improvement was observed in the modulation transfer function (MTF) of the total area ratio after wearing contact lenses. In contrast, the MTF of the high-order aberration area ratio resulting from lens wear was lower than that of the baseline measurement. There are also significant improvements observed for SMR and Optimum regarding near visual acuity, near point of accommodation, and the subjective questionnaire (OSDI and VBP) scores. Although it is difficult to avoid a specific negative impact on the ocular surface and tear film, visual function and visual quality can still be positively improved, especially shown on larger diameter and distance-center designed multifocal contact lenses.

Customized designed notch filters and applied effects on glare and contrast sensitivity in patients with dry eye syndrome.

PURPOSE: Glare visual acuity and contrast sensitivity are important indicators of visual quality. Studies have shown that the glare visual acuity and contrast sensitivity in dry eye patients tend to degenerate, further affecting their quality of life. The objective of this study was to investigate the effect of notch filters on glare VA and contrast sensitivity in patients with dry eye or with dry eye syndrome. METHOD: 36 subjects in the 20‒65 age group were diagnosed as having dry eye disease or perceived dry eye syndromes themselves who were included after the initial screening with the OSDI questionnaire, and one was subsequently excluded as they had undergone retinal detachment surgery. Finally, 35 subjects (14 male and 21 female) with a mean age of 40.66 ± 15.62 years participated in this study. All subjects wore their habitual prescriptions and four different filter lenses (namely 480, 620, dual 480 & 620 notch filter, and FL-41 tinted lens), and measured the parameters of glare visual acuity and contrast sensitivity using CSV-1000 and sine wave contrast test (SWCT), respectively. Student t-test and Repeated measurement analysis (R-ANOVA) were utilized by using SPSS 26.0 software. RESULTS: A dual-wavelength 480 & 620 nm optical notch filter had a significant anti-glare effect decreasing glare disabilities or discomfort, and leading to better visual quality, the same effect was also shown on a 480 nm notch filter lens. All participants showed a significant difference among the baseline, three notch filters (480 nm, 620 nm, dual-wavelength 480 & 620 nm), and FL-41 tinted lens were used on SWCT_A (1.5 cpd, F = 3.054, p = 0.019) and SWCT_E (18 cpd, F = 2.840, p = 0.049); but did not show statistical different on SWCT_B (3 cpd, F = 0.333, p = 0.771), SWCT_C (6 cpd, F = 1.779, p = 0.159), and SWCT_D (12 cpd, F = 1.447, p = 0.228). The baseline showed the best visual performance on CS at a low spatial frequency (SWCT_A, 1.5 cpd), any filter might reduce the contrast sensitivity at low spatial frequencies in the clinical trial, whereas 480 nm notch filter showed the best effectiveness on CS at a high spatial frequency (SWCT_E, 18 cpd), the FL-41 lens that also filters out the 480 nm band does not achieve the same effect. Moreover, patients with dry eye or those older than 40 years old preferred optical multilayer notch filters to FL-41 tinted lenses. CONCLUSION: The 480- & 620-nm dual-wavelength and 480-nm single-wavelength notch filters have the best effect on the glare visual acuity and contrast sensitivity (CS) at high spatial frequencies in dry eye patients. The 620-nm notch filter performs better in CS at low and mid-low spatial frequencies; the FL-41 tinted lens performs poorly for glare VA and CS spatial frequencies examination. Patients with glare disabilities or CS disturbance at high spatial frequencies may choose a 480-nm notch filter lens, and patients who have CS disturbance at low spatial frequencies may consider a 620-nm notch filter for the prescription.

Optical Design of a Miniaturized 10× Periscope Zoom Lens for Smartphones.

The size of the optical zoom system is important in smartphone camera design, especially as it governs the thickness of the smartphone. We present the optical design of a miniaturized 10× periscope zoom lens for smartphones. To achieve the desired level of miniaturization, the conventional zoom lens can be replaced with a periscope zoom lens. In addition to this change in the optical design, the quality of the optical glass, which also affects the performance of the lens, must be considered. With advancements in the optical glass manufacturing process, aspheric lenses are becoming more widely used. In this study, aspheric lenses are incorporated into a design for a 10× optical zoom lens with a lens thickness of less than 6.5 mm and an eight-megapixel image sensor. Furthermore, tolerance analysis is carried out to prove its manufacturability.

Design of Digital-Twin Human-Machine Interface Sensor with Intelligent Finger Gesture Recognition.

In this study, the design of a Digital-twin human-machine interface sensor (DT-HMIS) is proposed. This is a digital-twin sensor (DT-Sensor) that can meet the demands of human-machine automation collaboration in Industry 5.0. The DT-HMIS allows users/patients to add, modify, delete, query, and restore their previously memorized DT finger gesture mapping model and programmable logic controller (PLC) logic program, enabling the operation or access of the programmable controller input-output (I/O) interface and achieving the extended limb collaboration capability of users/patients. The system has two main functions: the first is gesture-encoded virtual manipulation, which indirectly accesses the PLC through the DT mapping model to complete control of electronic peripherals for extension-limbs ability by executing logic control program instructions. The second is gesture-based virtual manipulation to help non-verbal individuals create special verbal sentences through gesture commands to improve their expression ability. The design method uses primitive image processing and eight-way dual-bit signal processing algorithms to capture the movement of human finger gestures and convert them into digital signals. The system service maps control instructions by observing the digital signals of the DT-HMIS and drives motion control through mechatronics integration or speech synthesis feedback to express the operation requirements of inconvenient work or complex handheld physical tools. Based on the human-machine interface sensor of DT computer vision, it can reflect the user's command status without the need for additional wearable devices and promote interaction with the virtual world. When used for patients, the system ensures that the user's virtual control is mapped to physical device control, providing the convenience of independent operation while reducing caregiver fatigue. This study shows that the recognition accuracy can reach 99%, demonstrating practicality and application prospects. In future applications, users/patients can interact virtually with other peripheral devices through the DT-HMIS to meet their own interaction needs and promote industry progress.

Fabrication of Aluminum Oxide Thin-Film Devices Based on Atomic Layer Deposition and Pulsed Discrete Feed Method.

This study demonstrates the low-temperature (<100 °C) process for growing a thin silica buffer layer and aluminum oxide by atomic layer deposition (ALD) in the same reaction chamber. Heterogeneous multilayer thin films are prepared by a dual-mode equipment based on atomic layer deposition and plasma-enhanced chemical vapor deposition (PECVD) techniques. The pulse discrete feeding method (DFM) was used to divide the precursor purging steps into smaller intervals and generate discrete feeds, which improved the saturated distribution of gas precursors, film density and deposition selectivity. The experimental results show that the process method produces a uniform microstructure and that the best film uniformity is ±2.3% and growth rate is 0.69 Å/cycle. The thickness of aluminum oxide film has a linear relationship with the cyclic growth number from 360 to 1800 cycles. Meanwhile, the structural and mechanical stress properties of aluminum oxide thin films were also verified to meet the requirements of advanced thin-film devices.

Optical Simulation Design of a Short Lens Length with a Curved Image Plane and Relative Illumination Analysis.

This study proposes a three-lens design with a short lens length and explores the curved imaging plane and performs a relative illumination analysis. There are two ways to reduce the lens length: shortening the back focal and lens group lengths. We derived the relevant parameter relationships of three lenses using the first-order geometric optics theory. The optical lens length can be controlled within 2 mm. The shorter the lens length, the larger the angle of the chief ray in the image space, resulting in an increase in the field curvature and astigmatism. Third-order Seidel aberrations can be effectively reduced by a curved image plane. We also derived the equations for relative illuminance, solid angle, surface transmittance, and internal transmittance for the short three-lens design. The optical lens design uses a curved image plane to shorten the distance from the off-axis beam image space to the image plane and reduce the incident angle of the chief ray on the image plane. The formula and design results verified by Code V software (version 11.2) show that both the solid angle and relative contrast of the lens can be increased. For the proposed three-lens design with a short lens length, the semi-field angle is 32°, F/# is 2.7, the effective focal length is 1.984 mm, the image plane area is 2.16 mm × 1.22 mm, and the curvature radius of the concave image plane is 3.726 mm. Moroever, the MTF (100 lp/mm) is larger than 52%, the lateral color aberration is less than 2.12 µm, the optical distortion is less than 2.00%, and the relative illumination is greater than 68%.

Cost-Effective Design of a Miniaturized Zoom Lens for a Capsule Endoscope.

This paper presents a miniaturized design of a 2× zoom lens for application to a one-megapixel image sensor in a capsule endoscope. The zoom lens is composed of four lenses, including three plastic aspheric lenses and one glass spherical lens, and adopts a three-lens group design. This capsule endoscope is mainly for observation of the small intestine, which has a radius of about 12.5 mm. The height of the object is thus set to 12.5 mm. The object surface is designed to be curved surface with a radius of curvature of 15 mm. The focal length of the zoom lens ranges from 1.064 mm to 2.039 mm, and the full angle of view ranges from 60° to 143°, the f-number is F/2.8-F/3.5, the zoom lens is 11.6 mm in length, and the maximum effective diameter of the zoom lens is 6 mm. The zoom lens design is divided into six segments, corresponding to the different magnifications from Zoom 1 to Zoom 6. The magnification ratios are -0.0845, -0.0984, -0.1150, -0.1317, -0.1482, and -0.1690, respectively. Comparing the positions from Zoom 1 to Zoom 6, the maximum optical distortion is -14.89% for the Zoom 1 and 1.45% for the Zoom 6. The maximum vertical video distortion is 8.19% for Zoom 1 and 1.00% for Zoom 6. At a 1.0 field of view, the minimum relative illuminance is 71.8% at a magnification of M = -0.1317. Finally, we perform the tolerance analysis and lens resolution analysis at different zooming positions. Our design can obtain high-quality images for capsule endoscope.

Design of a Miniaturized Wide-Angle Fisheye Lens Based on Deep Learning and Optimization Techniques.

This paper presents the optimization design of a miniaturized five-element wide-angle fisheye lens using a deep learning algorithm. Zemax optical design software was used to simulate and optimize the wide-angle fisheye lens. A deep learning algorithm helped to find the best combination of different lens materials. We first used six lens elements as an initial configuration to design miniaturized wide-angle fisheye lenses using the optimization process. The optical system components were gradually decreased to five lens elements. Both OKP4HT and polymethyl methacrylate (PMMA) plastic aspheric lenses were selected to replace the second spherical glass lens in the original design. We propose two types of wide-angle fisheye lens designs with four spherical lenses and one aspheric lens. The results for these designs indicated a viewing angle of 174°, a total length of less than 15 mm, a spot size of less than 6 µm, lateral color within ±1 µm, field curvature within ±0.02 mm, and F-θ distortion of ±3.5%. In addition, the MTF value was larger than 0.4 at the spatial frequency of 100 cycles/mm.

The influence of contact lenses with different optical designs on the binocular vision and visual behavior of young adults.

Theoretically, contact lenses change the accommodation and vergence demands of the eyes and directly or indirectly influence binocular vision. The purpose of this study was to investigate the influence of different optical designs of contact lenses on binocular vision and visual behavior among young adults. In this randomized, single-blinded experimental study, visual behavioral performance (VBP) and Ocular Surface Disease Index questionnaires were used for preliminary screening. Nineteen myopic subjects aged 20-26 years (21.59 ± 1.40 years) participated in the study. Baseline values for subjective refraction and binocular visual functions were evaluated. All the subjects were randomly grouped to wear different optical designs of single-vision, progressive, and bifocal contact lenses. Eye examinations were performed on the first day (CL baseline), 2nd week, and 4th week of wearing the lenses. In addition, subjects completed the VBP and visual quality questionnaire again at the end of the examination. Single-vision contact lenses (Lens 1) increased accommodative lag, negative relative accommodation, and distant and near vergence; however, vergence facilities, accommodative facilities, heterophoria, and the comfort and posture balance dimensions in the VBP questionnaire were improved. Progressive contact lenses (Lens 2) reduced the lag of accommodation and near vergence; in addition, vergence facilities and accommodative facilities were also improved. Bifocal contact lenses (Lens 3) affected negative and positive relative accommodation, but vergence facilities and accommodative facilities also progressed. Furthermore, both progressive (Lens 2) and bifocal (Lens 3) contact lenses enhanced overall visual behavioral performance. In terms of visual quality, single-vision contact lenses (Lens 1) were the most comfortable, progressive and bifocal contact lenses reduced distant visual acuity and stability, progressive contact lenses (Lens 2) had more complaints about halos at night, and bifocal contact lens (Lens 3) users were more likely to have double vision. Compared with single-vision contact lenses, progressive and bifocal contact lenses relaxed accommodation, reduced the lag of accommodation, and improved visual behavioral performance. Although the vergence function showed a significant change, it did not show worse trends when wearing contact lenses. Contact lenses with different optical designs have a great influence on binocular vision and visual behavioral performance.

Internal Stress Prediction and Measurement of Mid-Infrared Multilayer Thin Films.

We present an experimental method for evaluating interfacial force per width and predicting internal stress in mid-infrared band-pass filters (MIR-BPF). The interfacial force per width between the two kinds of thin-film materials was obtained by experimental measurement values, and the residual stress of the multilayer thin films was predicted by the modified Ennos formula. A dual electron beam evaporation system combined with ion-assisted deposition was used to fabricate mid-infrared band-pass filters. The interfacial forces per width for Ge/SiO2 and SiO2/Ge were 124.9 N/m and 127.6 N/m, respectively. The difference between the measured stress and predicted stress in the 23-layer MIR-BPF was below 0.059 GPa. The residual stresses of the four-layer film, as well as the 20-layer and 23-layer mid-infrared band-pass filter, were predicted by adding the interface stress to the modified Ennos formula. In the four-layer film, the difference between the predicted value and the measured stress of the HL (high-low refractive index) and LH (low-high refractive index) stacks were -0.384 GPa for (HL)2 and -0.436 GPa for (LH)2, respectively. The predicted stress and the measured stress of the 20-layer mid-infrared filter were -0.316 GPa and -0.250 GPa. The predicted stress and the measured stress of the 23-layer mid-infrared filter were -0.257 GPa and -0.198 GPa, respectively.

Accurate prediction of multilayered residual stress in fabricating a mid-infrared long-wave pass filter with interfacial stress measurements.

We present an accurate approach to predict the residual stress in a multilayered mid-infrared long-wave pass filter (MIR-LWPF) by using interfacial stress measurements. Magnesium fluoride (MgF2) and zinc sulfide (ZnS) thin films were used to fabricate 7-layer (MgF2/ZnS)3/MgF2 MIR-LWPF devices by electron-beam evaporation with ion-assisted deposition technique. The interfacial stress between the high-index of ZnS and low-index of MgF2 thin film materials was obtained from the residual stress measurements based on Twyman-Green interferometer and fast Fourier transformation (FFT) method. The modified Ennos formula was used to estimate the residual stress in the (MgF2/ZnS)3/MgF2 multilayered thin films. The difference between the predicted stress value and the measured value is 28 MPa by the proposed method. In the MIR-LWPF design of (MgF2/ZnS)3/MgF2 multilayer structure, the optical transmittance at a near-infrared wavelength of 1.0 µm to 2.5 µm is less than 10%, and the transmittance at a mid-infrared wavelength of 2.5 µm to 7.5 µm is greater than 93%. The proposed method can accurately evaluate and predict residual stress in fabricating mid-infrared long-wave pass filter device which possesses low residual stress as well as lower surface roughness.

Electrically Controlled Diffraction Grating in Azo Dye-Doped Liquid Crystals.

This research applies the non-linear effect of azo dye-doped liquid crystal materials to develop a small, simple, and adjustable beam-splitting component with grating-like electrodes. Due to the dielectric anisotropy and optical birefringence of nematic liquid crystals, the director of the liquid crystal molecules can be reoriented by applying external electric fields, causing a periodic distribution of refractive indices and resulting in a diffraction phenomenon when a linearly polarized light is introduced. The study also discusses the difference in the refractive index (Δn), the concentration of azo dye, and the rising constant depending on the diffraction signals. The experimental results show that first-order diffraction efficiency can reach ~18% with 0.5 wt % azo dye (DR-1) doped in the nematic liquid crystals.

Optimization design of a stereo-photographic system based on achromatic double-prism arrays.

We present an optimization design for a stereo-photographic system where achromatic double-prism arrays are used in front of the camera lens to reduce chromatic aberration and distortion. Due to the optical properties of the prism, the image formed by a single-prism array exhibits large chromatic aberration and distortion. The chromatic aberration and distortion for both single-prism array and double-prism array stereo-photographic systems were analyzed by the CODE V software. The double-prism arrays have larger distortion, but the chromatic aberration is small. The distortion arising from the double-prism arrays can be compensated by the camera lens design. The design results show that the maximum spot size is reduced from 17.7 µm to 8.8 µm after optimization. The proposed stereo-photographic system has high-quality stereo images.

Zoom lens design for 10.2-megapixel APS-C digital SLR cameras.

A zoom lens design for a 10.2-megapixel digital single-lens reflex (SLR) camera with an advanced photo system type-C (APS-C) CCD image sensor is presented. The proposed zoom lens design consists of four groups of 3× zoom lenses with a focal length range of 17-51 mm. In the optimization process, 107 kinds of Schott glass combined with 26 kinds of plastic materials, as listed in Code V, are used. The best combination of glass and plastic materials is found based on the nd-Vd diagram. The modulation transfer function (MTF) was greater than 0.509 at 42 lp/mm, the lateral chromatic aberration was less than 5 µm, the optical distortion was less than 1.97%, and the relative illumination was greater than 80.05%. We also performed the tolerance analysis with the 2σ (97.7%) position selected and given tolerance tables and results for three zooming positions, which made the design more practical for manufacturing.

Optical, structural, and mechanical properties of silicon oxynitride films prepared by pulsed magnetron sputtering.

Silicon oxynitride films were deposited by reactive pulsed magnetron sputtering. The optical, structural, and mechanical properties of silicon oxynitride films with different nitrogen proportions were analyzed via spectroscopy, atomic force microscopy, Twyman-Green interferometer, and nanoindentation. The refractive indices of the silicon oxynitride films were adjusted from 1.487 to 1.956 with the increase in nitrogen proportions. The surface roughness decreased from 1.33 to 0.97 nm with the increase in nitrogen proportions. The residual stress of the silicon oxynitride films was higher than for pure silicon nitride and silicon dioxide films. The hardness and Young's modulus increased from 13.51 to 19.74 GPa and 110.41 to 140.49 GPa with the increase in nitrogen proportions, respectively. The hardness and Young's modulus of antireflection coatings using silicon oxynitride film were 13.64 GPa and 102.11 GPa, respectively. Silicon oxynitride film could be used to improve the hardness of antireflective coatings.

Optical design of an LED motorcycle headlamp with compound reflectors and a toric lens.

An optical design for a new white LED motorcycle headlamp is presented. The motorcycle headlamp designed in this study comprises a white LED module, an elliptical reflector, a parabolic reflector, and a toric lens. The light emitted from the white LED module is located at the first focal point of the elliptical reflector and focuses on the second focal point. The second focal point of the elliptical reflector and the focal point of the parabolic reflector are confocal. We use nonsequential rays to improve the optical efficiency of the compound reflectors. The toric spherical lens allows the device to meet the Economic Commission of Europe, regulation no. 113 (ECE R113). Furthermore, good uniformity is obtained by using aspherical surface optimization of the same toric lens. The reflectivity of the reflector is 95%, and the transmittance of each lens surface is 98%. The average deviation of the high beam is 14.17%, and the optical efficiency is 66.45%.

Simulation of autofocus lens design for a cell phone camera with object distance from infinity to 9.754 mm.

This paper presents the simulation of an autofocus lens design with large depth of field for a cell phone camera. The object distance of the lens is from infinity to 9.754 mm. When the object distance is from infinity to 550 mm, the value of the modulation transfer function (MTF) is greater than 0.6 for the spatial frequency of 114 lp/mm, the optical distortion is less than 1.5%, and the relative illumination is greater than 67%. When the object distance is from 325 to 9.754 mm, the MTF values is greater than 0.4 for close-up shooting. The optical distortion is less than 1.454%, and the relative illumination is greater than 68.8%.

Simulation design of a wearable see-through retinal projector.

This study proposes a new simulation design for a wearable see-through retinal projector combined with a compact camera. The see-through retinal projector is composed of an illumination system and eyepiece system. In this eyeglass-mounted design, all the information is projected directly into the user's eyes using a see-through retinal projector. The retinal projector forms a 20 in. (50.8 cm) upright virtual image located 2 m in front of the human eye, and the illumination system provides uniform illumination for liquid crystal on silicon (LCoS) panels. Moreover, an RGB LED array is used as the light source to generate color images with color sequences. The compact camera has a lens with an aperture of F/2.8, a half field-of-view (FOV) of 30°, and 2 million pixels. This optical system design with the combination of a see-through retinal projector and a compact camera has a volume of about 5.83 cm(3) and a weight of 6.02 g.

Simulation and comparison of the illuminance, uniformity, and efficiency of different forms of lighting used in basketball court illumination.

We simulate and compare the illuminance, uniformity, and efficiency of metal-halide lamps, white LED light sources, and hybrid light box designs combining sunlight and white LED lighting used for indoor basketball court illumination. According to the optical simulation results and our examination of real situations, we find that hybrid light box designs combining sunlight and white LEDs do perform better than either metal-halide lamps or white LED lights. An evaluation of the sunlight concentrator system used in our inverted solar cell shows that the energy consumption of stadium lighting can be reduced significantly.