Contrast Ratio Research Articles

Perceived Brightness and Resolution of Holographic Augmented Reality Retinal Scan Glasses

Augmented reality display performance depends strongly on features of the human visual system. This is especially true for retinal scan glasses, which use laser beam scanning and transparent holographic optical combiners. Human-centered approaches allow us to go beyond conventional optical metrology and evaluate display performance as it is perceived in actual augmented reality use cases. Here, we first present a theoretical formula for the retinal scan luminance and ambient contrast ratio calculated from optical powers, wavelengths, field of view, and human pupil diameter. As a promising insight, we found that the pupil diameter dependence is beneficial in assimilating the virtual image luminance to the ambient luminance. Second, we designed and performed a psychophysical experiment to assess perceived resolution in augmented reality settings using a fully functional retinal scan glasses prototype. We present the results of the trials and illustrate how this approach can be used in the further development of augmented reality smart glasses.

Liquid Crystal Display with High Transmittance and Excellent Image Quality

High transmittance and excellent image quality are two crucial requirements for thin-film transistor liquid crystal displays (TFT-LCDs). This work presents a novel pixel structure utilizing a vertical alignment liquid crystal (VA-LC) to improve both transmittance and image quality. The new pixel structure, called TCL-pixel, features a unique transparent conducting layer (TCL) that constructs an electric field shielding layer and a large transparent storage capacitor, resulting in good stability and a large aperture ratio. The 55" 8K product incorporating the TCL-pixel achieves high transmittance (3.87%) and a high contrast ratio (5100:1), attributed to the large aperture ratio. Additionally, it exhibits negligible vertical cross talk (0.7%), low color cross talk (3‰), low horizontal cross talk (JND 2.3), and enhanced variable refresh rate performance, confirming its good stability. Furthermore, the TCL-pixel demonstrates an improved viewing angle (CESI 0.03：65°) due to the multi-domain alignment produced by the transparent conducting layer.

Performance analysis of the photonic crystal–based X-OR gate for the terahertz applications

Abstract A key component of high-speed switching networks is an optical logic gate. This study presents the design and analysis of an all-optical XOR gate based on a two-dimensional photonic crystal (2D PC) structure, aiming to enhance high-speed switching in optical networks. The XOR gate, with two input and one output waveguide, is constructed on a hexagonal lattice, optimized for operation at a wavelength of 1,550 nm. The design is evaluated using the Finite Difference Time Domain (FDTD) approach, which simulates the optical performance of the structure. Key performance metrics, including the bit rate, contrast ratio, and delay time, are computed, showing that the proposed logic gate achieves a high contrast ratio of 30.35 dB and a minimal delay time of 0.4 ps. The results confirm the potential of this all-optical XOR gate for integration into high-speed optical circuits, offering low power consumption and high efficiency. This work demonstrates the feasibility of utilizing photonic crystal structures for high-performance optical logic gates in future communication systems. The simplicity of fabrication in a two-dimensional photonic crystal (2D-PC)-based all-optical logic gate can often be attributed to its simple design.

Cholesteric liquid crystal mixtures for the switchable smart windows and light shutters: electro-optical and dielectric behavior

Abstract Cholesteric liquid crystal (CLC) mixtures with variable pitch lengths were prepared for the electrical switchable smart window and light shutter applications by taking varied concentrations (2.6, 3.0, 4.0, and 5.0 wt%) of chiral dopant (R1011) having helical twisting power (HTP) 37.6 μm−1 and nematic E7 liquid crystal (LC). The morphological and electro-optical analysis of these CLC mixtures filled in 10µm thick cells were observed and reported herein, the switching of initial planar (P) and initial focal conic (FC) to homeotropic (H) states as well as vice-versa. The operating voltage of the 2.6 wt% of chiral doped CLC cell was relatively lower among all the sample cells compared with other concentrations. The maximum contrast ratio (CR) was observed for 5.0 wt% chiral doped CLC cell with initial planar state. However, the best CR was observed in 2.6wt% CLC cell with initial FC state. The comparative macroscopic views of the P, FC, and H states in the OFF and ON conditions of applied voltage for prepared CLC cells were observed for transparent and opaque states. Further, UV-visible spectroscopy was performed in the P, FC, and H states under the application of an externally applied field to observe the absorbance and band gap behavior of the fabricated CLC cells. Additionally, chiral concentration-dependent dielectric parameters with variable frequency in initial P and FC states of the fabricated cells were also reported. The temperature-dependent phase behavior of all the prepared cells exhibited a slight decrease in the isotropic phase of LC due to the doping of chiral dopants.

In-pixel foreground and contrast enhancement circuits with customizable mapping

This paper presents an in-pixel contrast enhancement circuit that performs image processing directly within the pixel circuit. The circuit leverages HyperFET, a hybrid device combining a MOSFET and a phase transition material (PTM), to enhance performance. It can be tuned for different modes of operation. In foreground enhancement mode, it suppresses low-intensity background pixels to nearly zero, isolating the foreground for better object visibility. In contrast enhancement mode, it improves overall image contrast. The contrast enhancement function is customizable both during the design phase and in real-time, allowing the circuit to adapt to specific applications and varying lighting conditions. A model of the designed pixel circuit is developed and applied to a full pixel array, demonstrating significant improvements in image quality. Simulations performed in HSPICE show a nearly 6x increase in Michelson Contrast Ratio (CR) in the foreground enhancement mode. Furthermore, process variation and Signal-to-Noise Ratio (SNR) analysis has been conducted to evaluate the robustness of the design under manufacturing variations. The simulation results indicate its potential for real-time, adaptive contrast enhancement across various imaging environments.

Squared diffusion-weighted imaging for improving the detection of clinically significant prostate cancer

Aim of this study was to proof the concept of optimizing the contrast between prostate cancer (PC) and healthy tissue by DWI post-processing using a quadrature method. DWI post-processing was performed on 30 patients (median age 67 years, prostate specific antigen 8.0 ng/ml) with PC and clear MRI findings (PI-RADS 4 and 5). Multiparametric MRI was performed at 3 Tesla. A multi-shot readout segmentation (rs-EPI) plus zoomed single-shot imaging (z-EPI) sequence was used in 15 patients (group 1) and a single-shot echo-planar imaging (ss-EPI) plus rs-EPI sequence in 15 patients (group 2). B-value images (b1000 and b1800/2000) were squared and then evaluated objectively software-based and subjectively using a 5-point. The squared DWI technique showed a significantly higher contrast ratio (CR) for ss-EPI b1800 (p < 0.001), rs-EPI b1000 (p < 0.001), rs-EPI b1800 (p < 0.001), z-EPI b1000 (p = 0.008) and for z-EPI b2000 (p < 0.001). After post-processing, a significant improvement in the subjective assessment of image quality was observed for rs-EPI b1000 (p < 0.001), rs-EPI b1800 (p < 0.001) and z-EPI b1000 (p < 0.001). The application of the square post-processing to DWI results in a significant improvement in the CR between PC and healthy tissue, especially at high b-values of ss-EPI or re-EPI. This method may help to improve the detection and differentiation of PC lesions.

The relative contrast ratio of malignant bone lesion is highest on relative Fat Fraction maps compared with T1-weighted and b900 DWI images.

Whole-body MRI (WB-MRI) is increasingly used in clinical practice for detection of malignant bone disease. A high relative contrast ratio (RCR) of malignant bone lesions compared with normal bone can improve disease detection in breast, prostate and myeloma malignancies. However, the RCR of malignant bone lesions on T1w, DWI and relative Fat Fraction (rFF) maps derived from Dixon T1w have not been compared. 110 baseline WB-MRI of patients with suspected malignant bone lesions were reviewed retrospectively. On each scan, up to four active bone lesions were identified, one each at the cervicothoracic spine, lumbosacral spine, pelvis and extremity, and their ROI signal intensity measured on rFF, T1w and DWI b = 900. The signal intensity of background bone was measured by placing an ROI on the nearest normal-appearing bone to each lesion, for each sequence. The mean lesion signal-to-background ratio (taken as RCR) for each lesion was calculated. We compared the RCR of bone lesions on rFF, T1w and DWI (Mann-Whitney test). The median rFF RCR of malignant bone lesions was highest compared with normal bone marrow than that of T1w (p < 0.0001) and DWI (p < 0.0001). There was no significant difference in the median rFF RCR of malignant bone lesions from breast cancer, myeloma and prostate cancer (p > 0.017, Bonferroni correction) or according to their anatomical locations (p > 0.012, Bonferroni correction). Malignant bone lesion RCR measured by lesion/background signal intensity was higher on rFF than on T1w and DWI b = 900 in patients with prostate, breast and myeloma malignancies, indicating its value for disease detection.

Central Involvement in Pure Autonomic Failure: Insights from Neuromelanin-Sensitive Magnetic Resonance Imaging and 18F-Fluorodopa-Positron Emission Tomography.

Central synucleinopathies, including Parkinson's disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA), involve alpha-synuclein accumulation and dopaminergic cell loss in the substantia nigra (SN) and locus coeruleus (LC). Pure autonomic failure (PAF), a peripheral synucleinopathy, often precedes central synucleinopathies. To assess early brain involvement in PAF using neuromelanin-sensitive magnetic resonance imaging (NM-MRI) and fluorodopa-positron emission tomography (FDOPA-PET), and to determine whether PAF patients with a high likelihood ratio (LR) for conversion to a central synucleinopathy exhibit reduced NM-MRI contrast in the LC and SN compared with controls and low-LR patients. Participants with PAF (n = 23) were categorized as high-LR (n = 13) or low-LR (n = 10) for conversion to central synucleinopathy. Additional participants included PD (n = 22), DLB (n = 8), and age- and sex-matched healthy controls (n = 23). NM-MRI at 3 T was used to quantify contrast ratios in the LC and SN, while FDOPA-PET measured presynaptic dopamine synthesis. Linear regression analyses, adjusted for age and sex, were used to compare NM-MRI contrast across groups. High-LR PAF patients showed reduced contrast in the LC and SN compared with controls and low-LR PAF patients, with values similar to PD and DLB. The NM-MRI contrast in the SN correlated with dopamine uptake in the striatum. Longitudinal imaging in PAF patients (n = 6) demonstrated reduced NM-MRI and PET values in individuals who developed central synucleinopathies. NM-MRI and FDOPA-PET may serve as potential biomarkers for early brain involvement and predicting progression to central synucleinopathies in PAF and could help identify patients for early intervention. © 2025 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Quantifying the perceptual translucency of the objects by spectrophotometric and imaging methods.

This study investigated the performance of various spectrophotometric methods in predicting visually perceived translucency and evaluated the efficiency of imaging techniques in quantifying translucency. We conducted the visual assessment in two stages using the pair comparison method. In the first stage, pairs of samples with identical colors but differing levels of translucency were compared. In the second stage, we compared pairs of samples with different colors but almost identical translucency. In the first stage, spectrophotometric methods exhibited high Pearson correlation coefficients, ranging from 0.96 to 0.99, with visual perceptions, demonstrating their accuracy in estimating translucency. Examination samples of different colors also revealed that among spectrophotometric methods, L*, absorption, and contrast ratio, with Pearson correlation coefficients of approximately 0.96, 0.96, and 0.98, respectively, had the strongest correlations with perceptual data. Using imaging techniques, the best result was obtained by comparing the lightness of the sample image on a black background to the same value on a white background, yielding a Pearson correlation coefficient of approximately 0.87. Additionally, we employed imaging-based methods for predicting translucency in real 3-D objects with simple shapes and limited colors. Despite the limitations, these methods produced promising results.

Evaluation of Intensive Statins and Proprotein Convertase Subtilisin/Kexin Type 9 Inhibitors on Intracranial Artery Plaque Stability: A Prospective Single-Arm Study.

Intracranial atherosclerotic stenosis is a leading cause of ischemic stroke and recurrent events due to plaque instability. High-resolution magnetic resonance imaging identifies plaque enhancement as a key marker of instability. This study evaluated the efficacy of combined high-intensity statins and proprotein convertase subtilisin/kexin type 9 inhibitors in plaque stabilization. In this prospective, single-arm study, patients with acute stroke and intracranial atherosclerotic stroke in the M1 segment of the middle cerebral artery or basilar artery were enrolled. After 24 weeks of intensive statin and evolocumab therapy, high-resolution magnetic resonance imaging assessments of intracranial vessels were conducted at baseline and follow-up. The primary end point was the change in stenosis degree; secondary end points included changes in plaque enhancement (contrast ratio) and plaque burden. Thirty-six patients (median age, 58 years) participated. After therapy, stenosis decreased from 75.9% (interquartile range, 69.5%-84.8%) to 65.3% (interquartile range, 53.8%-75.0%; P<0.001). Contrast ratio grades and contrast volume decreased significantly (P<0.001), and lumen area increased (from 1.03 mm2 [interquartile range, 0.59-1.72 mm2] to 2.08 mm2 [interquartile range, 1.00-3.10 mm2]; P<0.001). No significant changes were observed in wall area, wall area index, or remodeling index. A notable correlation between the decrease in low-density lipoprotein cholesterol/apolipoprotein B ratio and reduction in contrast volume was observed. Combining proprotein convertase subtilisin/kexin type 9 inhibitors with high-intensity statins may improve plaque stability and reduce lumen stenosis in patients with intracranial atherosclerotic stenosis. Larger randomized controlled trials are needed to confirm these findings. URL: https://www.chictr.org.cn; Unique identifier: ChiCTR2200058029.

Novel bilayered zirconia systems using recycled 3Y-TZP for dental applications.

To synthesize bilayer zirconia systems based on commercial or recycled 3Y-TZP obtained from non-milled remnants and to compare their optical and mechanical properties before and after aging. Bilayer zirconia samples were fabricated using either recycled 3Y-TZP (3Y-R/4Y and 3Y-R/5Y) or commercial powders (3Y/4Y and 3Y/5Y). Microstructure and phase composition were analyzed using ScanningElectronMicroscopy (SEM) and X-Ray Diffraction (XRD). Optical and mechanical properties were assessed via reflectance and biaxial flexural strength tests (BFS), followed by fractographic analysis. Optical properties and BFS data were analyzed using two-way ANOVA and Tukey test, and Weibull statistics, respectively. Recycled powder exhibited particle sizes < 2.07μm. SEM micrographs depicted dense surfaces with largest grains in the 5Y, followed by recycled-3Y, 4Y, and commercial-3Y. XRD analysis revealed tetragonal peaks in commercial and recycled 3Y-TZPs, and tetragonal and cubic phases in the 4Y and 5Y surfaces. Aging induced significant phase transformation in 4Y (∼40 %), commercial- (58 %) and recycled-3Y (53 %), with no effect in 5Y surfaces. Commercial bilayers exhibited higher translucency and strength (∼1130 MPa) compared to recycled bilayers (∼935 MPa), with no significant differences within commercial, nor within recycled groups. Aging decreased contrast ratio for recycled groups and increased the strength of all groups. While all groups presented high reliability up to 500MPa, commercial bilayers outperformed recycled systems at 800-MPa. The synthesis of bilayered systems using recycled-3Y was successful, resulting in high reliability in missions up to 500MPa. Bilayers based on commercial powder demonstrated superior translucency, strength, and reliability at 800MPa compared to their recycled counterparts.

Digital Mini-LED Lighting Using Organic Thin-Film Transistors Reaching over 100,000 Nits of Luminance.

This paper demonstrates the use of organic thin-film transistors (OTFTs) to drive active digital mini light-emitting diode (mini-LED) backlights, aiming to achieve exceptional display performance. Our findings reveal that OTFTs can effectively power mini-LED backlights, reaching brightness levels exceeding 100,000 nits. This approach not only enhances image quality but also improves energy efficiency. OTFTs offer a flexible and lightweight alternative to conventional silicon-based transistors, enabling innovative and versatile display designs. The integration of mini-LED technology with OTFTs produces displays with superior contrast ratios, enhanced color brightness, and lower power consumption. This technological advancement is poised to revolutionize high-dynamic-range (HDR) displays, including those in televisions, smartphones, and wearable devices, where the demand for high brightness and energy efficiency is paramount.

High contrast ratio light-emitting liquid crystal device based on AIEE dyes

In this paper, we have fabricated a light-emitting liquid crystal device (LELCD) with high contrast ratio (CR) using aggregation-induced emission enhancement (AIEE) dye, a photoluminescent (PL) material connected with liquid crystals (LCs) on weak surface anchoring boundaries. This LELCD can continually vary the PL intensity by controlling the direction of AIEE-dye molecules following the orientation of the LCs responding to the strength of the electric field. In order to check the effect of surface anchoring on the CR of this device, we used both horizontal and vertical alignment layers. For the horizontal alignment layer, we investigated the effect of CR at three different types of alignment layers with different anchoring energy and at different rubbing conditions for each alignment layer. For the vertical alignment layer, changes in the CR according to the rubbing strength were observed. Additionally, our study was conducted on the impact of LELCD cell thickness variations on the CR. Consequently, we achieved CR of about 30:1 at LELCD with cell thickness of 10 µm using polymethyl methacrylate as a horizontal alignment layer with weak surface anchoring boundary. This is the best result to date for CR of display devices using AIEE. We anticipate that the results of this study can be applied to optical devices and various other applications.

Effects of thiols on electro-optical properties of reverse polymer-stabilised liquid crystal films

ABSTRACT Reverse-mode polymer stabilised liquid crystal (RPSLC) can maintain a transparent state without voltage and exhibit excellent light scattering haze performance when voltage is applied, making it suitable for long-term use in smart windows. However, the high operating voltage of polymer stabilised liquid crystal devices necessitates efforts to reduce the driving voltage and enhance the contrast ratio to improve their optical properties. In this paper, we demonstrate that the introduction of a small amount of the thiol monomer into acrylate polymer monomer during UV-induced homopolymerisation and copolymerisation significantly affects the crosslinking density of the polymer network, thereby influencing the electro-optic performance of RPSLC devices. As a result, we have developed a high-contrast RPSLC device with a saturation voltage below 10 V. These findings are crucial for guiding practical improvements in the performance of RPSLC device.

Clinical feasibility of a deep learning approach for conventional and synthetic diffusion-weighted imaging in breast cancer: Qualitative and quantitative analyses

PurposeIn this study, we aimed to investigate the clinical feasibility of deep learning (DL)-based reconstruction applied to conventional diffusion-weighted imaging (cDWI) and synthetic diffusion-weighted imaging (sDWI) by comparing the DL reconstructions to cDWIs and sDWIs in patients with various breast malignancies. MethodsWe retrospectively analyzed 115 patients with biopsy-proven breast malignancies who underwent breast magnetic resonance imaging from July 2022 to June 2023, including conventional DWI with b-value of 800 s/mm2 (cDWI800), sDWI with b-value of 1500 s/mm2 (sDWI1500), DWI using DL-based reconstruction (DL-DWI) with b-value of 800 s/mm2, and synthetic DL-DWI with b-value of 1500 s/mm2 (DL-DWI800 and sDL-DWI1500). Two radiologists independently performed the qualitative analyses using a 5-point Likert scale for all DWI sets. The quantitative analyses were also conducted for signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and cancer-to-parenchyma contrast ratio (CPR). ResultsDL-DWI800 and sDL-DWI1500 provided better lesion conspicuity and thoracic muscle and rib delineation than cDWI800 and sDWI1500 (all P < 0.05). DL-DWI800 and sDL-DWI1500 showed comparable normal parenchymal signals to those of cDWI800 and sDWI1500 (all P > 0.05). sDL-DWI1500 and sDWI1500 showed no significant differences in SNR and CNR (P = 0.908, and P = 0.081, respectively). DL-DWI800 and cDWI800 were not significantly different between SNR, CNR, and CPR (all P > 0.05). ConclusionsDL-DWI outperformed cDWI and sDWI in both qualitative and quantitative analyses at the high b-values, while also achieving a shorter acquisition time.

Denoising low-field MR images with a deep learning algorithm based on simulated data from easily accessible open-source software

In this study, we introduce a denoising method aimed at improving the contrast ratio in low-field MRI (LFMRI) using an advanced 3D deep convolutional residual network model. Our approach employs synthetic brain imaging datasets that closely mimic the contrast and noise characteristics of LFMRI scans, addressing the limitation of available in-vivo LFMRI datasets for training deep learning models. In the simulation data, the Relative Contrast Ratio (RCR) increased, and similar improvements were observed in the in-vivo data across different imaging conditions. Comparative evaluations demonstrate that our model performs better than the widely used non-deep learning method, BM4D, in enhancing RCR and maintaining high spatial frequency components in in-vivo data.

Multilevel azopolymer patterning from digital holographic lithography

Holographically generated grayscale light patterns are used to directly create discrete multilevel surface reliefs, expanding the azopolymer-based patterning capabilities for complex surface designs.

Comparing Peristaltic and Direct-Drive Contrast Injection Systems for Thoracic Computed Tomography (CT): Effects on Dose, Image Quality, and Pathology.

Introduction To compare thoracic vasculature opacification between the direct-drive and the peristaltic drive contrast injection systems and the effect on quantitative and qualitative image quality during computed tomography. Method A retrospective chart review of 88 patients who underwent chest computed tomography (CT) following a direct-drive injector before 2016 (Group A) or a peristaltic injector after 2016 (Group B). Both protocols employed 80mL of iodinated contrast media volume. Quantitative measurements of the thoracic vascular opacification, contrast-to-noise ratio (CNR), effective radiation dose, and arterial venous contrast ratio (AVCR) for each vessel were computed and compared. The measured values of vascular opacification, CNR, and dose length product (DLP) were assessed utilizing paired t-test and Pearson's correlation. Receiver operating characteristic(ROC), visual grading characteristics (VGC), and Cohen's kappa methodology were measured. Results There was no significant difference in the mean opacification of the chest vasculature (p > 0.05). The CNR in Group B was significantly lower than in Group A (p < 0.05) except for the brachiocephalic artery, proximal descending aorta, and the right pulmonary artery. Arterial venous contrast ratio at all anatomic levels demonstrated no statistical significance between groups. There were no differences in ROC, VGC, or kappa values between groups. Conclusion When comparing two contrast media injection systems in chest CT, there was no qualitative difference in image quality or pathology detection. However, quantitatively, direct-drive injectors provided higher CNR. Direct-drive contrast injectors also provided a superior quantitative image quality of chest vasculature compared to peristaltic injectors.

Balancing Cost and Quality Goals with Full‐Array Local Dimming Displays

AbstractNew method drives down power consumption in FALD displays while simultaneously increasing contrast ratios and compensating for ambient lighting conditions.

High Ambient Contrast Ratio and Efficiency LED Display Devices Utilizing Inverted Packaging Structure

High Ambient Contrast Ratio and Efficiency LED Display Devices Utilizing Inverted Packaging Structure