Color Filter Research Articles

Use of Digital Methods to Optimize Visualization during Surgical Gonioscopy.

Purpose: The aim of this study was to evaluate the efficacy of digital visualization for enhancing the visualization of iridocorneal structures during surgical gonioscopy. Methods: This was a prospective, single-center study on a series of 26 cases of trabecular stent implantation performed by the same surgeon. Images were recorded during surgical gonioscopy, and before stent implantation, with standard colors and with the optimization of various settings, principally color saturation and temperature and the use of the cyan color filter. Subjective analyses were performed by two glaucoma surgeons, and objective contrast measurements were made on iridocorneal structure images. Results: The surgeons evaluating the images considered the optimized digital settings to produce enhanced tissue visibility for both trabecular meshwork pigmentation and Schlemm's canal in more than 65% of cases. The mean difference in the standard deviation of the pixel intensity values was 37.87 (±4.61) for the optimized filter images and 32.37 (±3.51) for the standard-color images (p < 0.001). The use of a cyan filter provided a good level of contrast for the visualization of trabecular meshwork pigmentation. Increasing the color temperature highlighted the red appearance of Schlemm's canal. Conclusions: We report here the utility of optimized digital settings including the cyan filter and a warmer color for enhancing the visualization of iridocorneal structures during surgical gonioscopy. These settings could be used in surgical practice to enhance the visualization of the trabecular meshwork and Schlemm's canal during minimally invasive glaucoma surgery.

Trans-Reflective Structural Color Filters Assisting Multifunctional-Integrated Semitransparent Photovoltaic Window.

Multifunction-integrated semitransparent organic photovoltaic cells (STOPVs), with high power generation, colorful transmittance/reflectance, excellent UV protection, and thermal insulation, are fully in line with the concept of architectural aesthetics and photoprotection characteristics for building-integrated photovoltaic-window. For the indelible rainbow color photovoltaic window, one crucial issue is to realize the integration of these photons- and photoelectric-related multifunction. Herein, dynamic transmissive and reflective structural color controllable filters, with asymmetrical metal-insulator-metal configurations (20nm-Ag-HATCN-30nm-Ag) through machine learning, were deliberately designed for colorful STOPV devices. This endows the resultant integrated devices with ∼5% enhanced power conversion efficiency than the bare-STOPVs, gifted UV (300-400nm) blocking rates as high as 93.5, 94.1, 90.2, and 94.5%, as well as a superior IR (700-1400nm) rejection approaching 100% for transparent purple-, blue-, green- and red-STOPV cells, respectively. Most importantly, benefiting from the photonic recycling effect beyond microcavity resonance wavelength, a reported quantum utilization efficiency as high as 80%, was first presented for the transparent-green-STOPVs with an ultra-narrow bandgap of 1.2eV. These asymmetrical Febry-Pérot transmissive and reflective structural color filters can also be extended to silicon- and perovskite-based optoelectric devices and make it possible to integrate additional target optical functions for multi-purpose optoelectric devices. This article is protected by copyright. All rights reserved.

All-dielectric metasurface-based color filter in CMOS image sensor

The development of all-dielectric metasurfaces vigorously prompts the applications of optical metasurfaces for a CMOS (Complementary Metal-oxide-semiconductor) image sensor. Dielectric nanostructures, due to their resonant behavior and its tunability, offer the possibility to be assembled into flexible and miniature spectral filters, which could potentially replace conventional pigmented and dye-based color filters. In this paper, a transmission filter based on a GMR (Guided Mode Resonance) mode of all-dielectric metasurface is adopted as an example to study the effect of application scenario of integrated CMOS image sensor chip and manufacturing mistakes, such as the small size of pixel, special dielectric environment around, surface roughness and structural defects. Numerical calculations based on the FDTD (finite difference time domain) method are used to study the relationship between the robustness of the metasurfaces and the optical resonant modes. More important, a method simplifying different manufacturing mistakes as basic geometry structure during the FDTD simulation is also proposed and demonstrated. This work deepens our understanding of the working mechanism of all-dielectric metasurfaces and paves the way for their use in CMOS image sensor.

A New Filter Design Built Into CMOS Image Sensor

dry etch and Electron beam lithography were used to directly integrate plasmonic color filters onto the top surface of a complementary metal oxide semiconductor (CMOS. The filters have a spectral range of 3.5 × 8 microns. After measuring the photocurrent, it was found that the 150×150-pixel plasmonic CIS was sensitive to all colors in the visible spectrum. The filters were made using a straightforward method that only required a single lithographic procedure. This is in contrast to the standard multi-stage processing required when working with dyedoped polymers. It is possible to fabricate these plasmonic components on a metal layer near to the photodiodes since they are intrinsically compatible with a typical CMOS process. Future low-cost, low-cross-talk, high-functionality advanced CIS may be possible with the help of such plasmonic components.

8.2: Invited Paper: The Full‐color Micro‐LED Display with Quantum Dots Inkjet Printing

A color conversion film, including red and green quantum dots, is fabricated using inkjet printing. To ensure the efficiency of the color conversion, a color filter is utilized to remove extra blue light. By selecting the appropriate central wavelength for the filter, the color conversion film can convert blue light to red and green light without extra blue light. The color conversion film is stimulated by blue micro‐LED, and the resulting color gamut can achieve 84.5% BT.2020. These results demonstrate that combining a quantum dots film with a color filter can result in full‐color micro‐LED displays.

Petrographic and technological aspects of improving the methodology for alternative determination of the degree of carbonification

The methodology for determining the earlier proposed indicator of the intensity of the shade of grey (Grey Intensity) as an alternative to the normative indicator of the reflectivity of vitrinite has been improved. The values of this indicator have been analyzed in the polished section specimen on the surfaces of the cut, layering, and tangential sections along the macerals of all three groups (vitrinite, liptinite, inertinite). The studies have been conducted in natural incident light as well as in the light passing through yellow, red, blue, and green filters. A large factual material has analyzed the petrographic and technological difficulties of measuring the Grey Intensity indicator. It is associated with the spatial arrangement of the observation planes of preparations relative to the natural occurrence of coal beds, the surface features of macerals, the influence of chemical (fluidization, gas generation) and tectonic (dynamic metamorphism) processes on the transformation of the gelled substance as the main object of research. Recommendations on the choice of a lens and a platform for measurements have been given, taking into consideration the optical system of incident light. The expediency of using color filters has been considered.

P‐17.2: Structure Design and Optical Performance Research of Automotive Oversized Curved Mini LED Module

BOE has launched a 21.6‐inch LTPS curved Mini LED module to meet the needs of automotive customer for oversized curved strip display, which can eliminate color mixture problem of curved display with COA (color filter on array) technology and achieve high contrast and local dimming. The radius of the module is R2000. There is no color mixture by visual inspection when the display is observed under the solid color picture, and the color shift can be up to max.3JNCD @U /D/L/R 30°. The brightness is 1000 nits, and the contrast is 1, 000, 000:1. At the same time, the optical performance has been tested and studied.

OPTIMIZATION ASSISTED AUTOREGRESSIVE METHOD WITH DEEP CONVOLUTIONAL NEURAL NETWORK-BASED ENTROPY FILTER FOR IMAGE DEMOSAICING

The natural scenes are captured by digital cameras that adopt a single charged-coupled device (CCD) or Complementary Metal Oxide Semiconductor (CMOS) sensor with a Color Filter Array (CFA). To reconstruct a full color image from the mosaiced CFA image, the missing components of color are recovered by a technique called color demosaicing. This research work introduces Deep Convolution Neural Network (DCNN)-based optimization assisted autoregressive method for image demosaicing. Here, the proposed optimization algorithm, termed Adaptive Autoregressive Water Wave Optimization algorithm (Adaptive Autoregressive-WWO), that is formed by combining Conditional autoregressive value at risk (CAViaR) model and Water Wave Optimization algorithm (WWO). Fusion process is carried out for residual images to generate the final demosaiced image based on entropy measure. Here, the output generated from DCNN is the first residual image. The LPA-ICI filter utilizes the optimization algorithm that generated second order polynomial coefficients to produce the second residual output image. Moreover, this proposed method is evaluated for its performance using metrics, such as Peak signal-to-noise ratio (PSNR) and Second Derivative like Measurement (SDME) and attained the highest PSNR values of 40.379dB and highest SDME values of 50.675dB.

Application of InP Quantum Dot film by Photolithography Technology on a Micro-LED Display

The technical of realizing full-color display by monochromatic integrated 100 × 100 blue Micro-LED array exciting InP quantum dot color conversion layer is researched in this study. Using photolithography technology to prepare color film on a separate glass cover glass has the advantages of better accuracy and display resolution. The optimum thickness 12 μm of the quantum dot photoresist (QDPR) was verified and 10 μm black matrix (BM) was proposed to reduce the light crosstalk between different sub-pixels. The thickness of color filter 1 ± 0.4 μm was made successfully between the QDPR and the cover glass, which can greatly can significantly increase the display color gamut from 78.7% to 100.8% NTSC. The red and green brightness conversion efficiency reach up to 78.1% and 296.5% respectively. Representative RGB monochromatic pictures with 100% high yield were displayed successfully.

Perylene Diimide Incorporated Polyurethane Polymer as Potential Colour Filter Material with Non‐fluorescent Property†

Comprehensive SummaryA novel polyurethane polymer containing perylene diimide (PDI) unit and aniline segment, denoted as PU‐PDI, was designed and synthesized. Their tensile property and photophysical characteristic were investigated using various experimental and theoretical techniques. It is found that the elongation of PU‐PDIs can reach more than 1000%, indicating good tensile performance. Moreover, based on the photoinduced electron transfer mechanism, the aniline segments in polyurethane can quench the auto‐fluorescence of PDI unit to a negligible value, which overcomes the intractable fluorescence drawbacks of conventional colour filters. The non‐emissive characteristic, in combination with the good thermal stability and tensile property of PU‐PDI, provides a feasible design strategy to fabricate optical filters with high display quality.

Nanotransfer-on-Things: From Rigid to Stretchable Nanophotonic Devices

The growing demand for nanophotonic devices has driven the advancement of nanotransfer printing (nTP) technology. Currently, the scope of nTP is limited to certain materials and substrates owing to the temperature, pressure, and chemical bonding requirements. In this study, we developed a universal nTP technique utilizing covalent bonding-based adhesives to improve the adhesion between the target material and substrate. Additionally, the technique employed plasma-based selective etching to weaken the adhesion between the mold and target material, thereby enabling the reliable modulation of the relative adhesion forces, regardless of the material or substrate. The technique was evaluated by printing four optical materials on nine substrates, including rigid, flexible, and stretchable substrates. Finally, its applicability was demonstrated by fabricating a ring hologram, a flexible plasmonic color filter, and extraordinary optical transmission-based strain sensors. The high accuracy and reliability of the proposed nTP method were verified by the performance of nanophotonic devices that closely matched numerical simulation results.

Recent Advances in Electro-Optic Response of Polymer-Stabilized Cholesteric Liquid Crystals

Cholesteric liquid crystals (CLC) are molecules that can self-assemble into helicoidal superstructures exhibiting circularly polarized reflection. The facile self-assembly and resulting optical properties makes CLCs a promising technology for an array of industrial applications, including reflective displays, tunable mirror-less lasers, optical storage, tunable color filters, and smart windows. The helicoidal structure of CLC can be stabilized via in situ photopolymerization of liquid crystal monomers in a CLC mixture, resulting in polymer-stabilized CLCs (PSCLCs). PSCLCs exhibit a dynamic optical response that can be induced by external stimuli, including electric fields, heat, and light. In this review, we discuss the electro-optic response and potential mechanism of PSCLCs reported over the past decade. Multiple electro-optic responses in PSCLCs with negative or positive dielectric anisotropy have been identified, including bandwidth broadening, red and blue tuning, and switching the reflection notch when an electric field is applied. The reconfigurable optical response of PSCLCs with positive dielectric anisotropy is also discussed. That is, red tuning (or broadening) by applying a DC field and switching by applying an AC field were both observed for the first time in a PSCLC sample. Finally, we discuss the potential mechanism for the dynamic response in PSCLCs.

Nonlinear demosaicking method and apparatus for nonlinear CMOS image sensors exhibiting low-density salt-and-pepper noise

Simple demosaicking methods designed for linear CMOS image sensors, such as MATLAB’s demosaic function, may be used with a monotonic nonlinear sensor having a Bayer color filter array (CFA). However, such methods may be inadequate at handling dynamic salt-and-pepper noise (SPN), i.e., outlier pixels, which is expected in images taken with a nonlinear sensor. Although SPN is present with linear sensors, nonlinear sensors express low-density light-dependent SPN that requires filtering. Extending a recent work on dynamic SPN filtering of a nonlinear sensor, we propose, evaluate, and verify a nonlinear method and apparatus to demosaic images, taken with a Bayer CFA, while simultaneously filtering the SPN. The approach relies on the use of weighted medians to filter the SPN, especially at densities that imply isolated outliers in small neighborhoods, while determining an accurate red, green, and blue (RGB) color at every pixel location. For explanatory purposes, three variants of the proposed method are presented and evaluated. A ground-truth image set, in which RGB channels were not obtained by demosaicking, is subsampled in a Bayer CFA pattern to produce mosaicked images for testing. In varying densities, SPN is introduced to these Kodak images for method and apparatus evaluation. Results of the proposed method and its variants are compared with those obtained with MATLAB’s demosaic function. Considering the alternatives and also apparatus complexity, the proposed nonlinear demosaicking method proves superior in visual quality, for smooth textures and along edges, and in peak signal-to-noise ratio, when there is low-density SPN.

Machine Learning-Enabled Inverse Design of Radiative Cooling Film with On-Demand Transmissive Color

Passive radiative cooling is a cost-efficient and eco-friendly approach to cool terrestrial objects by dissipating heat to the outer space. Colored radiative cooling (CRC) has many advantages over conventional passive radiative cooling and has garnered growing interest recently. However, existing CRC films are normally opaque, where the incident sunlight is either reflected for rendering color or absorbed to generate waste heat. In this work, we design a transmissive CRC film that allows a specific portion of light to pass through and provides more vivid colors. Such a transmissive film achieves the coloration and cooling dual-function by stacking a solar transparent selective emitter on top of a nanocavity-based color filter. The top emitter is first designed by using a mixed-integer memetic algorithm, where the layer materials, their number sequence, and thicknesses are simultaneously optimized. The variability in both material composition and layer thickness enables the emitter with a near-ideal emissivity in the atmospheric windows for subambient cooling, and an ultrahigh transmissivity in the solar range for sunlight penetration. Then, the structures of bottom nanocavity are determined by using a tandem neural network for on-demand color generation. This machine learning-assisted inverse design approach provides real-time structure prediction for on-demand colors and offers great flexibility in balancing the cooling and coloring functionalities. The proposed methodology can have special significance in broadening the application of passive radiative coolers in energy-efficient buildings, power-generating windows, and sustainable greenhouses.

A Multilevel Optical Anticounterfeiting System Based on Color Space‐Correlated Raman Spectroscopy of Diamond

Optical anticounterfeiting certifies the authenticity of goods using optical information coding units. A Raman tag with Raman peaks serving as copious optical information coding units is optimal for optical anticounterfeiting. However, complex manufacturing conditions, the use of toxic materials/pollutants, and the request for cross‐reference with fluorescence and/or Rayleigh scattering limit its actual application. Herein, these drawbacks are tackled by proposing the color space‐correlated Raman spectroscopy of diamonds, which are recognized as an extraordinary material in many respects. Specifically, diamond is utilized as a Raman tag because the 1332 cm−1 Raman peaks generate unlimited information coding states with excitation wavelengths and excitation powers. The diamond Raman spectra with excitation wavelength and excitation power in color space and grayscale space to access a 6D (R, G, B, Alpha, excitation wavelength, and excitation power) information coding space are swept. The design's implementation with a diamond is first showcased. Then, the corresponding information coding capacities in grayscale, color space and the dependencies of red, green, blue (RGB) color filters are investigated. Finally, a practical application of the method is proposed. This work opens up a new pathway for publicizing Raman‐based optical anticounterfeiting by an infinitely scalable information coding strategy with diamond photonics.

D$^\text{2}$UF: Deep Coded Aperture Design and Unrolling Algorithm for Compressive Spectral Image Fusion

Compressive spectral imaging (CSI) has attracted significant attention since it employs synthetic apertures to codify spatial and spectral information, sensing only 2D projections of the 3D spectral image. However, these optical architectures suffer from a trade-off between the spatial and spectral resolution of the reconstructed image due to technology limitations. To overcome this issue, compressive spectral image fusion (CSIF) employs the projected measurements of two CSI architectures with different resolutions to estimate a high-spatial high-spectral resolution. This work presents the fusion of the compressive measurements of a low-spatial high-spectral resolution coded aperture snapshot spectral imager (CASSI) architecture and a high-spatial low-spectral resolution multispectral color filter array (MCFA) system. Unlike previous CSIF works, this paper proposes joint optimization of the sensing architectures and a reconstruction network in an end-to-end (E2E) manner. The trainable optical parameters are the coded aperture (CA) in the CASSI and the colored coded aperture in the MCFA system, employing a sigmoid activation function and regularization function to encourage binary values on the trainable variables for an implementation purpose. Additionally, an unrolling-based network inspired by the alternating direction method of multipliers (ADMM) optimization is formulated to address the reconstruction step and the acquisition systems design jointly. Finally, a spatial-spectral inspired loss function is employed at the end of each unrolling layer to increase the convergence of the unrolling network. The proposed method outperforms previous CSIF methods, and experimental results validate the method with real measurements.

Structural Colors on Al Surface via Capped Cu-Si3N4 Bilayer Structure

Tunable structural colors have a multitude of applications in the beautification of mobile devices, in the decoration of artwork, and in the creation of color filters. In this paper, we describe a Metal-Insulator-Metal (MIM) design that can be used to systematically tune structural colors by altering the thickness of the top metal and intermediate insulator. Cu and Si3N4 were selected as the top metal and intermediate insulator layers, respectively, and various reflection colors were printed on Al. To protect the Cu surface from scratchiness and oxidation, a number of capping layers, including SiO2, LPSQ, PMMA, and the commercially available clear coat ProtectaClear, were applied. In addition to their ability to protect Cu from a humid environment without deteriorating color quality, ProtectaClear and LPSQ coatings have minimal angle dependency. Furthermore, a bilayer of PMMA/SiO2 can protect the Cu surface from the effects of humidity. In addition, the PMMA/SiO2 and ProtectaClear/SiO2 bilayers can also protect against corrosion on the Cu surface. The colors can be tuned by controlling the thickness of either the metal layer or intermediate insulator layer, and vivid structural colors including brown, dark orange, blue, violet, magenta, cyan, green-yellow, and yellow colors can be printed. The measured dielectric functions of Cu thin films do not provide any evidence of the plasmonic effect, and therefore, it is expected that the obtained colors are attributed to thin-film interference.

Reducing the Power Consumption of VR Displays with a Field Sequential Color LCD

To achieve 60 pixels per degree (PPD) and 100° field of view (FoV) while keeping a reasonably high aperture ratio for active-matrix liquid crystal displays (LCDs), field sequential color (FSC) is a promising approach. We evaluate the physical properties of a high birefringence nematic LC mixture and then use these data to simulate the performance of a fringe-field switching (FFS) LCD. Such an FFS LCD exhibits a fast average gray-to-gray response time (~1.5 ms) to enable FSC operation. By removing the spatial color filters, FSC operation triples the resolution density and optical efficiency, which are critical to high-resolution density and low power consumption virtual reality applications. Wide color gamut (96.2% of the DCI-P3 standard) and superior color uniformity are also demonstrated using such an FSC LCD.

Optical modeling and analysis of pixel organic light-emitting diode using a mixed-level algorithm considering light leakage effects

Fast optical simulation is the basis of optical optimization for cross-scale 3D pixel organic light-emitting diodes (OLEDs), and it is among the most critical challenges in the industry. We constructed an optical simulation model by using a mixed-level algorithm to fasten the analysis of pixel OLEDs, considering the light leakage effect, which was described in terms of the ratio of light extraction (RLE). Model correctness and efficiency were verified using a commercial software. Pixel OLEDs with different sizes were used, and the influence of the height and angle of pixel definition layers (PDLs) and width of color filters on the performance was analyzed. These geometric features change the path of light propagation, which changes performance. Device B was more sensitive to the PDL angle, whereas devices A and C were more sensitive to the PDL height. Device B had the least RLE (RLEB>RLEA>RLEC). An optimal structure can reduce light leakage and improve the performance of pixel OLEDs. The proposed method provides guidelines for designing optimal pixel OLEDs and for the high-throughput simulation of pixel OLEDs.

Coloured vortex beams with incoherent white light illumination.

The orbital angular momentum is a fundamental degree of freedom of light wavefronts, currently exploited in applications where information capacity is a key requirement, such as optical communication, super-resolution imaging and high-dimensional quantum computing. However, generating orbital angular momentum beams requires spatio-temporally coherent light sources (lasers or supercontinuum sources), because incoherent light would smear out the doughnut features of orbital angular momentum beams, forming polychromatic or obscured orbital angular momentum beams instead. Here we show generation of coloured orbital angular momentum beams using incoherent white light. Spatio-temporal coherence is achieved by miniaturizing spiral phase plates and integrating them with structural colour filters, three-dimensionally printed at the nanoscale. Our scheme can in principle generate multiple helical eigenstates and combine colour information into orbital angular momentum beams independently. These three-dimensional optical elements encoded with colour and orbital angular momentum information substantially increase the number of combinations for optical anti-counterfeiting and photonic lock-key devices in a pairwise fashion.