Color Filter Research Articles

Performance evaluation of coloured filters on PV panels in an outdoor environment

AbstractThis study aims to investigate the effects of colour filters and tilt angles on the electrical output characteristics of solar photovoltaic modules. The experimental set‐up allowed for the evaluation of various combinations of colour filters and tilt angles by using a realistic simulation of solar panel installations. The various light spectrum wavelengths and energy levels were taken into account, keeping in mind any potential impacts on the solar cells' conversion efficiency. The results showed that compared to other filter combinations, the use of red colour filters with a 10% blockage rate and an optimal tilt angle led to a noticeable increase in electrical output. This result emphasises the value of colour filtering and tilt angle selection in raising solar photovoltaic systems' overall performance. When compared to the other filters, the red, orange, and yellow filters stand out due to their outstanding efficiency of around 84.98%, 84.08%, and 83.69%. However, the teal, green, and blue filters exhibit relatively low levels of efficiency of about 69.62%, 67.06%, and 58.52%, respectively. The distinct reaction shown by purple and pink filters, when subjected to tilt angle of 30 degrees, offers a potentially productive direction of enhancing the efficiency of PV panel.

The Effect of Varying the Light Spectrum of a Scene on the Localisation of Photogrammetric Features

In modern digital photogrammetry, an image is usually registered via a digital matrix with an array of colour filters. From the registration of the image until feature points are detected on the image, the image is subjected to a series of calculations, i.e., demosaicing and conversion to greyscale, among others. These algorithms respond differently to the varying light spectrum of the scene, which consequently results in the feature location changing. In this study, the effect of scene illumination on the localisation of a feature in an image is presented. The demosaicing and greyscale conversion algorithms that produce the largest and smallest deviation of the feature from the reference point were assessed. Twelve different illumination settings from polychromatic light to monochromatic light were developed and performed, and five different demosaicing algorithms and five different methods of converting a colour image to greyscale were analysed. A total of 300 different cases were examined. As the study shows, the lowest deviation in the polychromatic light domain was achieved for light with a colour temperature of 5600 K and 5000 K, while in the monochromatic light domain, it was achieved for light with a green colour. Demosaicing methods have a significant effect on the localisation of a feature, and so the smallest feature deviation was achieved for smooth hue-type demosaicing, while for greyscale conversion, it was achieved for the mean type. Demosaicing and greyscale conversion methods for monochrome light had no effect. The article discusses the problem and concludes with recommendations and suggestions in the area of illuminating the scene with artificial light and the application of the algorithms, in order to achieve the highest accuracy using photogrammetric methods.

Monolithic full-color micro-LED displays featuring three-dimensional chip bonding and quantum dot-based color conversion layer

What we believe to be a novel fabrication process for monolithic full-color (RGB) micro-LED (µLED) display technology, featuring three-dimensional (3D) and quantum dot (QD)-based color conversion layer, has been proposed. This method offers advantages such as a wide color gamut, high pixel density, high yield, and low cost. A 16 × 16 passive matrix (PM) RGB µLED array, with a pitch size of 80 µm and a pixel density of 328 pixels per inch (PPI), has been successfully realized using flip-chip bonding technology. When measuring the electroluminescence (EL) spectra of the green and red pixels with the addition of color filters, the color gamut can achieve a maximum of 124% of the National Television System Committee (NTSC) standard. Additionally, this process significantly reduces the risk of damage to the QD film during photolithography compared to using two different colored QDs for RGB µLED arrays. The proposed manufacturing process shows considerable promise for commercialization.

Flexible plasmonic display featuring differentiated and localized control over transmission and reflection

Structural colors using metal materials, plasmonic color generation, can confine optical excitation beyond the diffraction limit owing to nanoscale metals with high efficiency in light absorption and scattering. They have several advantages over conventional display technology, including superior resolution and long-term preservation. However, most research on plasmonic color generation has been conducted for the development of static color generation, and dynamic tuning remains a challenging issue. To develop dynamic plasmonic colors, electrochemical, liquid crystal, and electromechanical methods have been proposed; however, there have been limitations in repeatability, flexibility, and scale-up processes. To address these problems, this work proposes a flexible dynamic plasmonic display using dielectric elastomer actuators (DEAs) to isotropically control the interdistance between the metal nanostructures, which can show dynamic coloration without polarization distortion. To replace the expensive and small-scale manufacturing approach, shadow masking and transfer technique with the anodic aluminum oxide (AAO) membrane was applied to realize large-scale and uniformly distributed Au nanodisc array. The differentiated and localized color change in the transmission and reflection modes, such as Janus's face, is realized by proper design of Au nanodisc array on the patterned transparent compliant electrodes formed by silver nanowires and PEDOT:PSS composites. Apparent and locally active color changes appeared in the transmission mode, but almost no color changes were observed in the reflection model by DEA actuation. The proposed system has the potential to activate color filters, cryptographic characters, and next generation display technologies.

Ultraviolet color image sensor based on CsPbBr3 inorganic perovskite nanocrystal film.

Ultraviolet and color imaging require different image sensors and optical channels, which results in large size, complex structure, and high cost of imaging systems. Here, we report a novel, to the best of our knowledge, image sensor that combines ultraviolet and color imaging functions. The fabrication of this image sensor is achieved by coating high-transparency CsPbBr3 perovskite nanocrystals in a polymer film on the color filter layer of a silicon-based detector. The film, serving as an ultraviolet photoluminescent layer, exhibits high transparency, exceeding 91.5% at wavelengths beyond the photoluminescence peak of 513 nm. During ultraviolet imaging, the film converts ultraviolet light into visible light, which passes through the green filter layer to reach the detector for imaging. During visible light imaging, red light, green light, and most of the blue light pass through the CsPbBr3 perovskite nanocrystal film and color filter layer to reach the detector for imaging. As a result, the image sensor can capture both 257 nm solar-blind ultraviolet images and color photos in the visible light.

Single-Frame Lagrangian Tracking Of 3-D Acoustic Streaming Flows Using Digital Defocusing Micro Particle Streak Velocimetry

In this study, a single-frame particle streak velocimetry technique is applied to the classic DDPIV(Digital Defocusing Particle Image Velocimetry) concept to achieve a single-frame 3-D Lagrangian tracking of particles in microscopic flows. The shortcoming of images suffering low signal to noise ratio due to pinholes can be avoided. With the streak resolving algorithm, it allows extended exposure time when streak images are taken, and the single-frame approach also eliminates the need for high-cost and complicated synchronization hardware for double-pulse frame-straddling light sources. For each long-exposure, color-coded images received from each pinhole equipped with red, green or blue color filters, the streak-resolving algorithm is applied first to find each streak on the separate color channel, followed by an one-time triplet-matching process to group the red, green and blue streak projections. From the streak triplets, 3-D reconstruction can be done on all the resolved points on the streak, and trajectory fitting can then be applied to resolve the tracer particle trajectories in the field of view with temporal history. This procedure was applied for visualizing a microscale 3-D acoustic streaming flow pattern induced by a longitudinal spine-shaped fin oscillating at 12kHz. The height of the channel is 1mm with the spine of 0.3mm height and a 30 。 tip angle. Resolved flow fields show that the particle streak images can be resolved with the same level of accuracy to the particle tracking method, while the throughput of velocity vectors can be significantly higher due to multiple velocity vectors can be resolved from each streak triplet. The methodology has the potential to be applied to various applications that can capture long-exposure images and possible to resolve higher-order information such as acceleration and forces applied on the particles or the flow.

Tailoring resonant modes in dual cavities for transmissive structural colors with high brightness and high purity

We present quad-layered structural color filters producing transmissive red (R), green (G), and blue (B) colors with high brightness and high purity, where thicknesses of layers for the RGB colors are optimized by using a L-BFGS-B algorithm. To evaluate the performance of the proposed structural color filters, computer-based inverse designs based on meta-heuristic and reinforcement learning algorithms are employed, where the optical properties obtained from the inverse designs are comparable to those shown in our proposed design. A peak separation phenomenon in dual cavities is applied to make a spectral response rectangular, and also a resonance order is optimally tailored to maximize the transmittance at a resonant wavelength with the suppression of undesired higher-order resonances at the same time for achieving pure colors. Transmission efficiency over 75% and the full width at half-maximum (FWHM) less than 90 nm are achieved. Besides, selecting a cavity medium with a high refractive index allows the optical properties of the structural color filters to remain almost constant in wavelength over a broad range of incident angles up to 60°. Moreover, only a few deposition steps are necessary, thus leading to a much simple fabrication as compared to previous works that involve a series of complicated lithographic processes. The approach described in this study may provide new ways for achieving diverse applications, such as displays, imaging devices, decorations, and colored solar cells.

Exploration of OLED structures for high-resolution microdisplays with enhanced efficiency and color gamut

The subpixel size of high-resolution organic light-emitting diode (OLED) microdisplays measures a few micrometers. To achieve a full-color microdisplay, the current preference is to use photolithography technology on a white OLED instead of using a fine metal mask for patterning. The application of photolithography techniques allows for the creation of microcavity structures or color filters (CFs) to enhance color purity in each emitted color. This paper focuses on investigating specialized OLED device structures for high-resolution microdisplays. The characteristics of each structure, including efficiency and color gamut, are thoroughly discussed. The structure, combining microcavity and CF, achieves the widest color gamut, while microcavity structures show higher efficiency compared to CF-only structures. Tandem structures are also considered for improved efficiency and stability.

Inverse design of color routers in CMOS image sensors: toward minimizing interpixel crosstalk

Abstract Over the past decade, significant advancements in high-resolution imaging technology have been driven by the miniaturization of pixels within image sensors. However, this reduction in pixel size to submicrometer dimensions has led to decreased efficiency in color filters and microlens arrays. The development of color routers that operate at visible wavelengths presents a promising avenue for further miniaturization. Despite this, existing color routers often encounter severe interpixel crosstalk, around 70 %, due to the reliance on periodic boundary conditions. Here, we present interpixel crosstalk-minimized color routers that achieve an unprecedented in-pixel optical efficiency of 87.2 % and significantly reduce interpixel crosstalk to 2.6 %. The color routers are designed through adjoint optimization, incorporating customized incident waves to minimize interpixel crosstalks. Our findings suggest that our color router design surpasses existing color routing techniques in terms of in-pixel optical efficiency, representing a crucial step forward in the push toward commercializing the next generation of solid-state image sensors.

Adaptive infrared radiation modulator using reversible metal electrodeposition with silicon carbide-based fabry-perot cavity

Conventional materials that statically modulate radiation in the infrared (IR) region of the electromagnetic spectrum underpin the performance of many entrenched technologies. The development of their adaptive variants, whereby the IR radiation properties dynamically change as a response to external stimuli, has emerged as an important unfulfilled scientific challenge. Here, by combining the silicon carbide (SiC)-based Fabry-Perot (FP) cavity effect with the traditional reversible metal electrodeposition device (RMED), where the FP cavity is used as a color filter to emit a particular wavelength and the RMED is used to reversibly modulate IR radiation, we develop an adaptive IR radiation modulator with large and uniform IR emissivity tunability (Δε ≥ 0.579) in the 3–14 µm region. A specific structural color which is a function of the SiC thickness can be simultaneously displayed when the modulator is in the low-emissivity mode. By varying the SiC thickness from 100 to 180 nm, a full gamut of colors spanning the entire visible spectrum can be achieved. Additionally, the modulator can exhibit fantastic patterns consisting of different structural colors with simple designs achieved. We believe that our findings may open opportunities for camouflage in multispectral detection and many technologies related to IR radiation management.

Functional Visual Outcomes of Wearing Colored Filters in Patients with Dry Age-Related Macular Degeneration

Functional Visual Outcomes of Wearing Colored Filters in Patients with Dry Age-Related Macular Degeneration

Full-colour-sorting metalens based on guided mode resonance

Full-colour-sorting metalens using few nanostructured layers have recently generated considerable interest as high-sensitivity colour image sensors because of their reliability and high resolution. Based on the guided mode resonance principle and propagation phase modulation, a full-colour-sorting metalens is designed, which can theoretically obtain any wavelength of light from the incident white light and realize arbitrary wavelength focusing with the same focal length in the visible range. Without the loss of generality, we propose a prototype of such metalens used for sorting blue, green and red light from the visible spectrum commonly used in practical applications. The maximum focussing efficiency is over 50% with a relatively high numerical aperture of 0.7. The proposed full-colour-sorting metalens can be used in many applications, such as colour mixing, colour holography, colour filtering, wavelength division multiplexing and so on.

Analysis of the possibility of increasing the level of reliability of fire alarms systems through integration with video-based flame detection system

Classic Fire Alarm Systems (FAS) are characterized by a high level of false alarms in relation to the number of confirmed reports. To increase the level of reliability of operation of this type of system, it was proposed to integrate it with a Video-Based Flame Detection System (VBFDS). For this purpose, a video-based fire detection algorithm was designed. In addition, methods popular in the literature for increasing the reliability of such systems, such as color filtering, the Tracking Growth Object (TGO) factor, and the use of the Naive-Bayes (NB) classifier, were tested. The purpose of the article is to analyze these methods in comparison with the basic version of the algorithm, as well as the possibility of integrating Video-Based Flame Detection System (VBFDS) with classic FAS.

High-Magnification Object Tracking with Ultra-Fast View Adjustment and Continuous Autofocus Based on Dynamic-Range Focal Sweep.

Active vision systems (AVSs) have been widely used to obtain high-resolution images of objects of interest. However, tracking small objects in high-magnification scenes is challenging due to shallow depth of field (DoF) and narrow field of view (FoV). To address this, we introduce a novel high-speed AVS with a continuous autofocus (C-AF) approach based on dynamic-range focal sweep and a high-frame-rate (HFR) frame-by-frame tracking pipeline. Our AVS leverages an ultra-fast pan-tilt mechanism based on a Galvano mirror, enabling high-frequency view direction adjustment. Specifically, the proposed C-AF approach uses a 500 fps high-speed camera and a focus-tunable liquid lens operating at a sine wave, providing a 50 Hz focal sweep around the object's optimal focus. During each focal sweep, 10 images with varying focuses are captured, and the one with the highest focus value is selected, resulting in a stable output of well-focused images at 50 fps. Simultaneously, the object's depth is measured using the depth-from-focus (DFF) technique, allowing dynamic adjustment of the focal sweep range. Importantly, because the remaining images are only slightly less focused, all 500 fps images can be utilized for object tracking. The proposed tracking pipeline combines deep-learning-based object detection, K-means color clustering, and HFR tracking based on color filtering, achieving 500 fps frame-by-frame tracking. Experimental results demonstrate the effectiveness of the proposed C-AF approach and the advanced capabilities of the high-speed AVS for magnified object tracking.

Potassium Iodide Doping for Vacancy Substitution and Dangling Bond Repair in InP Core-Shell Quantum Dots.

This work highlights the novel approach of incorporating potassium iodide (KI) doping during the synthesis of In0.53P0.47 core quantum dots (QDs) to significantly reduce the concentration of vacancies (i.e., In vacancies; VIn-) within the bulk of the core QD and inhibit the formation of InPOx at the core QD-Zn0.6Se0.4 shell interfaces. The photoluminescence quantum yield (PLQY) of ~97% and full width at half maximum (FWHM) of ~40 nm were achieved for In0.53P0.47/Zn0.6Se0.4/Zn0.6Se0.1S0.3/Zn0.5S0.5 core/multi-shell QDs emitting red light, which is essential for a quantum-dot organic light-emitting diode (QD-OLED) without red, green, and blue crosstalk. KI doping eliminated VIn- in the core QD bulk by forming K+-VIn- substitutes and effectively inhibited the formation of InPO4(H2O)2 at the core QD-Zn0.6Se0.4 shell interface through the passivation of phosphorus (P)-dangling bonds by P-I bonds. The elimination of vacancies in the core QD bulk was evidenced by the decreased relative intensity of non-radiative unpaired electrons, measured by electron spin resonance (ESR). Additionally, the inhibition of InPO4(H2O)2 formation at the core QD and shell interface was confirmed by the absence of the {210} X-ray diffraction (XRD) peak intensity for the core/multi-shell QDs. By finely tuning the doping concentration, the optimal level was achieved, ensuring maximum K-VIn- substitution, minimal K+ and I- interstitials, and maximum P-dangling bond passivation. This resulted in the smallest core QD diameter distribution and maximized optical properties. Consequently, the maximum PLQY (~97%) and minimum FWHM (~40 nm) were observed at 3% KI doping. Furthermore, the color gamut of a QD-OLED display using R-, G-, and B-QD functional color filters (i.e., ~131.1%@NTSC and ~98.2@Rec.2020) provided a nearly perfect color representation, where red-light-emitting KI-doped QDs were applied.

Resonant-mode engineering for additive reflective structural colors with high brightness and high color purity

We present quad-layered reflective structural color filters generating vivid additive primary colors by controlling a mode number in a Fabry–Perot (FP) cavity and an anti-reflective (AR) coating layer, thus accomplishing high spectral contrast which is highly demanded in creating sharp colors. The reflection brightness of fabricated structural color filters is over 78% and a color gamut is comparable to the standard color gamut (sRGB). Higher-order resonant modes are exploited yielding a narrow passband with strong suppression of the reflection at shorter and longer wavelength ranges for a green color, while red and blue colors are produced by employing fundamental resonant modes. Besides, the structural color filters maintain both high brightness and high color purity at oblique incidence angles up to 40° due to a small angle of refraction by a cavity medium with high refractive index. Moreover, a large-scale fabrication is enabled owing to the simplicity of a device structure, where thin film deposition is used. The scheme presented in this work may open the door to a number of applications, such as reflective displays, imaging devices, colored photovoltaics, and decorations.

Compact multispectral light field camera based on an inkjet-printed microlens array and color filter array

With emerging advanced optical sensing technologies and their wide-ranging applications, gathering comprehensive optical data from real-world scenes is becoming increasingly crucial for their accurate reconstruction and analysis. In order to capture both three-dimensional (3D) spatial and spectral information from a scene, multiple devices or time-intensive scanning processes are often involved. Here, we demonstrate a multispectral light field camera that allows for the simultaneous acquisition of 3D information and spectral data in a single snapshot. By utilizing inkjet printing as the fabrication technology, the miniaturized optical components in the camera were manufactured with high precision and can be integrated into a standard camera housing. Furthermore, the microlens arrays and the color filter arrays were fabricated on the same substrate, and a precise alignment between the two arrays was achieved. The compact multispectral camera opens the door to a multitude of possibilities for mobile applications, ranging from autonomous driving and consumer electronics such as smartphones to medical technology such as endoscopes.

Scaling up multispectral color filters with binary lithography and reflow (BLR)

Abstract Efforts to increase the number of filters are driven by the demand for miniaturized spectrometers and multispectral imaging. However, processes that rely on sequential fabrication of each filter are cost ineffective. Herein, we introduce an approach to produce at least 16 distinct filters based on a single low-resolution lithographic step with minimum feature size of 0.6 μm. Distinct from grayscale lithography, we employ standard binary lithography but achieve height variations in polymeric resist through a post-development reflow process. The resulting transparent polymeric films were incorporated in Fabry–Perot cavity structures with cavity thickness ranging from 90 to 230 nm to produce transmittance across the visible spectrum. This binary lithography and reflow (BLR) process demonstrates control of the dielectric layer thickness down to ∼15 nm. This new process provides a cost-effective alternative to traditional techniques in fabricating microscopic transmission filters, and other applications where precise thickness variation across the substrate is required.

56‐1: Invited Paper: Mechanical Strength Improvement of Foldable Panel with COE

It is significant to reduce power consumption and thickness of foldable display with larger size. Color filter on Encapsulation (COE), as one of the most critical technologies, has excellent performance in terms of power consumption and thinning. COE refers to the technical proposal replacing polarizer with color filter on the surface of encapsulation(COE). However, we have encountered two problems of reduced mechanical strength in the mass production. One of the problems is panel peeling in module process, and the other one is cracking during drop test. This paper has studied the root cause of COE panel strength reduction from panel design, process and material. As a result we achieved the same mechanical strength as polarizer panel.

P‐239: Late‐News Poster: Modeling Particle Deposition in Evaporating Colloidal Droplets

Inkjet printing is a cost‐effective method of particle deposition applicable, for example, in the manufacture of Quantum Dot (QD) color filters. However, it is a challenge to achieve uniform deposition of particles because evaporating colloidal dispersions are prone to the coffee‐ring effect.When the particle size is small, it is difficult to gauge directly by experiment how particles migrate during the evaporation process. Consequently, it is a challenge to optimize the process conditions to improve uniformity by experiment alone. To aid in this task, we have developed a simulator for colloidal droplet evaporation. Rather than use an effective particle concentration field as in previous works, motion of each individual particle is calculated by Stokesian Dynamics, with particle interactions governed by the DLVO theory. In order to facilitate the simulation of large collections of particles, GPU computing is applied to reduce the simulation time.A phase‐field approach is taken to capture the interface physics at the solvent‐air interface. Within a colloidal droplet we find that, by controlling the temperature, it is possible to promote Marangoni flow and, in turn, improve deposition uniformity. In future, we aim to use simulation to further optimize the process conditions, such as the chamber pressure and temperature, in order maximize uniformity.