Improved Contrast Ratio Research Articles

Far-focus compound ultrasound imaging with lag-one coherence-based zero-cross factor

BACKGROUND: Ultrasound imaging has been widely used in clinical examination because of portability, safety, and low cost. However, there are still some main challenges of imaging quality that remain in conventional ultrasound systems. OBJECTIVE: Improving image quality of SA-based methods using an improved imaging mode named far-focus compound (FSC) imaging. METHODS: A far-focus compound (FSC) imaging based on full-aperture transmission and full-aperture reception is proposed in this paper. In transmission, it uses the full aperture to transmit the focused beam to ensure image resolution and emission of sound field energy. In reception, the full aperture is used to receive the reflected beam to ensure the image quality. A lag-one coherence-based zero-cross factor (LOCZF) is then implemented in FSC for improvement of contrast ratio (CR). The LOCZF uses lag-one coherence as zero-cross factor’s adaptive coefficient. Comparisons were made with several other weighting techniques by performing simulations and experiments for performance evaluation. RESULTS: Results confirm that LOCZF applied to FSC offers a good image contrast and simultaneously the speckle pattern. For simulated cysts, CR improvement of LOCZF reaches 194.1%. For experimental cysts, CR improvement of LOCZF reaches 220%. From the in-vivo result, compared with FSC, CR improvement of LOCZF reaches 112.7%. CONCLUSION: Proved gCNR performance. In addition, the LOCZF method shows good performance in experiments. The proposed method can be used as an effective weighting technique for improvement of image quality in ultrasound imaging.

Plane-wave medical image reconstruction based on dynamic Criss-Cross attention and multi-scale convolution.

Plane-wave imaging is widely employed in medical imaging due to its ultra-fast imaging speed. However, the image quality is compromised. Existing techniques to enhance image quality tend to sacrifice the imaging frame rate. The study aims to reconstruct high-quality plane-wave images while maintaining the imaging frame rate. The proposed method utilizes a U-Net-based generator incorporating a multi-scale convolution module in the encoder to extract information at different levels. Additionally, a Dynamic Criss-Cross Attention (DCCA) mechanism is proposed in the decoder of the U-Net-based generator to extract both local and global features of plane-wave images while avoiding interference caused by irrelevant regions. In the reconstruction of point targets, the experimental images achieved a reduction in Full Width at Half Maximum (FWHM) of 0.0499 mm, compared to the Coherent Plane-Wave Compounding (CPWC) method using 75-beam plane waves. For the reconstruction of cyst targets, the simulated image achieved a 3.78% improvement in Contrast Ratio (CR) compared to CPWC. The proposed model effectively addresses the issue of unclear lesion sites in plane-wave images.

Improvement of contrast ratio between cavitation bubbles and tissue by frequency filtering in triplet pulse ultrasound imaging

Bubble-enhanced high-intensity focused ultrasound treatment requires selective imaging of cavitation bubbles to ensure their localization to the target tissue. Previous studies have proposed the ultrasound imaging of cavitation bubbles with a filtering method, which makes bubble extraction by a triplet pulse sequence more selective. The envelope component as well as harmonic components are generated during the nonlinear propagation of an ultrasonic imaging pulse, but the triplet pulse sequence can significantly reduce only the harmonic components, and its selectivity is degraded by the residual envelope component. In this study, the effects of nonlinear propagation at various intensities of imaging pulse and the frequency filtering to obtain better selectivity are investigated for the triplet pulse sequence with a filtering method. The result shows that the imaging pulse intensity is an important parameter that determines the strength of the effect of nonlinear propagation and that the optimal frequency filtering changes according to it.

35‐2: A kind of Front Light Source Module Adapted to Reflective LCD

Reflective Liquid Crystal display (RLCD) has the advantage s of low power and lightweight relying on the metal layer in TFT glass to reflect the environment light, developing rapidly in the outdoor display, e‐books, price tag, and sports watch market. However, when the ambient light weaker, RLCD requires an additional light source. Therefore the development of the front light source has become a new research direction. This paper designed a thin front light source adapted to Reflective LCD by using the microstructure to control light angle. Optimize microstructure parameters to improve contrast ratio and light efficiency utilization. The density arrangement of microstructures to achieve the higher uniformity and no moire.

Enhancement of Ultrasound B-Mode Image Quality Using Nonlinear Filtered-Multiply-and-Sum Compounding for Improved Carotid Artery Segmentation.

In ultrasound B-mode imaging, the axial resolution (AR) is commonly determined by the duration or bandwidth of an excitation signal. A shorter-duration pulse will produce better resolution compared to a longer one but with compromised penetration depth. Instead of relying on the pulse duration or bandwidth to improve the AR, an alternative method termed filtered multiply and sum (FMAS) has been introduced in our previous work. For spatial-compounding, FMAS uses the autocorrelation technique as used in filtered-delay multiply and sum (FDMAS), instead of conventional averaging. FMAS enables a higher frame rate and less computational complexity than conventional plane-wave compound imaging beamformed with delay and sum (DAS) and FDMAS. Moreover, it can provide an improved contrast ratio and AR. In previous work, no explanation was given on how FMAS was able to improve the AR. Thus, in this work, we discuss in detail the theory behind the proposed FMAS algorithm and how it is able to improve the spatial resolution mainly in the axial direction. Simulations, experimental phantom measurements and in vivo studies were conducted to benchmark the performance of the proposed method. We also demonstrate how the suggested new algorithm may be used in a practical biomedical imaging application. The balloon snake active contour segmentation technique was applied to the ultrasound B-mode image of a common carotid artery produced with FMAS. The suggested method is capable of reducing the number of iterations for the snake to settle on the region-of-interest contour, accelerating the segmentation process.

Improving lateral resolution and contrast by combining coherent plane-wave compounding with adaptive weighting for medical ultrasound imaging

Due to the severe lateral lobe artifact by coherent plane-wave compounding (CPWC) and the low signal-to-noise ratio of radiofrequency (RF) data collected from the plane wave, the adaptive beamforming methods based on focused wave imaging (FWI) are improper to be directly applied to CPWC. To obtain a high-quality image with high resolution and contrast, this study combined the threshold phase coherence factor (THR-PCF) with the reconstructed covariance matrix minimum variance (RCM-MV) and then proposed a novel CPWC-based adaptive beamforming algorithm, THR-PCF + RCM-MV. The simulation, phantom, and in-vivo experiments were performed to investigate the performance of the proposed methods in comparison with the CPWC and the classical adaptive methods including the minimum variance (MV), generalized coherence factor (GCF) and their combination GCF + MV. The simulation results demonstrated that the THR-PCF + RCM-MV beamformer improved contrast ratio (CR) by 28.14%, contrast noise ratio (CNR) by 22.01%, speckle signal-to-noise ratio (s_SNR) by 23.58%, generalized contrast-to-noise ratio (GCNR) by 0.3%, and the full width at half maximum (FWHM) by 43.38% on average, compared with the GCF + MV method. The phantom experimental results showed a better performance of the THR-PCF + RCM-MV beamformer with an average improvement by 21.95% in CR, 2.62% in s_SNR, and 48.64% in FWHM compared with the GCF + MV. Meanwhile, the results showed that the image quality of the near and far fields was enhanced by the THR-PCF + RCM-MV. The in-vivo imaging results showed that our new method had potential for clinical application. In conclusion, the lateral resolution and contrast of medical ultrasound imaging could be improved greatly with our proposed method.

High-speed optimisation of an all-optical half adder using a T-shaped photonic crystal waveguide with an improved contrast ratio

High-speed optimisation of an all-optical half adder using a T-shaped photonic crystal waveguide with an improved contrast ratio

Dual projection generalized sidelobe canceller based on mixed signal subspace for ultrasound imaging.

In this paper, we propose a dual projection generalized sidelobe canceller (DPGSC) based on mixed subspace (MS) for ultrasound imaging, which aims to improve the speckle signal-noise-ratio (sSNR) and decrease the dark-region artifacts. A mixed signal subspace based on the correlation between the desired steering vector and the eigenvectors is constructed to further optimize the desired steering vector and the final weight vector. The simulated and experimental results show that the proposed method can greatly improve the speckle uniformity. In the geabr_0 experiment, the standard deviation of background and sSNR of MS-DPGSC can be improved by 48.07% and 58.49% more than those of eigenspace-based generalized sidelobe canceller (ESGSC). Furthermore, for a hyperechoic target, the maximal improvement of contrast ratio is 95.29%. In terms of anechoic cyst, the contrast-to-noise ratio of MS-DPGSC is increased by 123.08% than that of ESGSC. The rat mammary tumor experimental data show that the proposed method has better comprehensive imaging effect than traditional generalized sidelobe cancellers and ESGSCs.

Optically Isotropic Liquid Crystal Mode Templated by Nanoporous Breath Figure Membrane

AbstractIn this study, a printing‐based scalable method is proposed for the higher density of a liquid crystal (LC) nanodroplet structure suitable for the optically isotropic LC mode where the LC nanodomains are accurately templated by a nanoporous breath figure (BF) membrane. The highly porous BF polymeric template structure is reliably obtained by utilizing self‐structured packing effects of the silica nanospheres achieved by doctor blade coating. A nanocomposite film with densely packed silica nanospheres encapsulated by the UV‐crosslinked polymer matrix is made by controlling the blade coating velocity and blade gap conditions. This provides a higher LC fill‐factor condition of the optically isotropic nanodroplet LC (OI‐NDLC) mode with filling the LCs into the nanopores obtained after selective silica etching. The OI‐NDLC structure templated by the nanoporous BF membrane made with the silica nanospheres of 300 nm can effectively resolve the scattering‐induced optical loss and depolarization issues observable in the OI‐NDLC mode prepared by conventional phase separation approaches due to the sufficiently reduced LC droplet size. The structure exhibits a much‐improved light leakage level in the field‐off optically isotropic state, a higher transmittance level as the field‐induced Kerr operation, and resultant improved contrast ratio properties.

Photonic-crystal-based design and FDTD simulation of all-optical NAND and NOR gates with improved contrast ratio

The proposed research reports the simulation of a photonic crystal (PhC) ring-resonator-based full-optical NAND and NOR gate design. The designed structure comprises a 18 × 30 square lattice dielectric silicon rod-type PhC with a refractive index of n = 3.46. An interatomic distance ‘a’ of 560 nm, radius ‘r’ of 0.21a (0.133 μm) and input wavelength λ = 1550 nm with an input signal amplitude of 1 volt are used in this design. The proposed structure provides two large band gaps in Transverse Electric polarized mode in the ranges of 1342–1980 nm and 758–779 nm. Similar parameters are used for both NAND and NOR logic gate designs. The functionality of the proposed full-optical gates depends on the ring resonator principle and the intensity of the incident light. Numerical analysis of the simulation is based on the finite difference time domain method, whereas band gap analysis is performed using the plane wave expansion method.

Ultrasound far-focused pixel-based imaging using Wiener postfilter scaled by adjustable zero-cross factor

Synthetic aperture (SA) imaging can provide a uniform lateral resolution but an insufficient signal-to-noise ratio (SNR). SA method with bidirectional pixel-based focusing (SA-BiPBF) has the ability to obtain a higher quality image than conventional SA imaging. In this paper, an enhanced SA-BiPBF named full aperture received far-focused pixel-based (FrFPB) is firstly proposed to obtain a high resolution image. An adjustable zero-cross factor scaled Wiener postfilter (AZFsW) is then implemented in FrFPB for improving contrast ratio (CR). The adjustable zero-cross factor is calculated using the polarity of echo signals sequence with an adjustable coefficient σ to estimate the signal coherence, and it is combined with Wiener postfilter to obtain a good capability of noise reduction and background speckle pattern preservation. Simulation and experiments have been conducted to evaluate the imaging performance of the proposed methods. Results show that FrFPB can obviously improve the resolution in comparison with SA-BiPBF, and contrast-to-noise ratio (CNR) and speckle signal-to-noise ratio (sSNR) are retained. In addition, AZFsW can achieve a much higher CR than SA-BiPBF. When σ is 0.6, the CR improvement is 96.7% in simulation, 78.7% in phantom experiment, and 49.2% in in-vivo experiment. To evaluate the imaging performance of AZFsW, coherence factor, conventional Wiener postfilter, and scaled Wiener postfilter are implemented. The imaging results show that when σ is in the range of [0.6, 0.7], AZFsW exhibits a satisfying comprehensive imaging performance.

All‐optical half adder based on non‐linear triangular lattice photonic crystals with improved contrast ratio

All‐optical half adder based on non‐linear triangular lattice photonic crystals with improved contrast ratio

Textural and electro-optical study of a room temperature nematic liquid crystal 4̍-pentyl-4-biphenylcarbonitrile doped with metal oxide nanowires in planar and in-plane switching cell configurations

ABSTRACT This work shows the doping effect of metal oxide nanowires (alumina nanowires) on the textural and electro-optical characteristics of nematic liquid crystal (5CB) in planar and in-plane switching (IPS) cell configurations. Results indicate the increase in nematic to isotropic phase transition temperature after doping in both planar and IPS cells. A decrease in threshold voltage in addition to increase in contrast ratio, birefringence, and band gap energy was observed after doping with alumina nanowires in both types of cells. Overall analysis shows that IPS cell configuration has more improved threshold voltage and contrast ratio in addition to decrease in birefringence and transmission intensity, as compared to planar cell configuration. No effect of cell configuration was observed on energy band gap and found same value for both planar and IPS cell configurations, as energy band gap is a material specific property.

A Stronger Aadaptive Local Dimming Method with Details Preservation

Local dimming technology focuses on improving the contrast ratio of the displayed images for a great visual perception. It consists of backlight extraction and pixel compensation. Considering a single existing backlight extraction algorithm can hardly adapt to images with diverse characteristics and rich details, we propose a stronger adaptive local dimming method with details preservation in this paper. This method, combining the advantages of some existing methods and introducing the combination of the subjective evaluation and the objective evaluation, obtains a stronger adaptation compared with others. Besides, to offset the luminance reduction caused in the backlight extraction process, we improve the bi-histogram equalization algorithm and propose a new pixel compensation method. To preserve image details, the Retinex theory is adopted to separate details. Experimental results demonstrate the effect of the proposed method on contrast ratio improvement and details preservation.

Contrast ratio improvement of ADS UHD product

Contrast ratio improvement of ADS UHD product

Electropolymerized poly(3,4-ethylenedioxyselenophene) on flexible substrate: A comparative study of electronic and electrochromic properties with sulfur analogue and rigid substrate

Recently, significant efforts have been devoted on poly(3,4-ethylenedioxyselenophene) (PEDOS) and its derivatives due to their promising properties for various optoelectronic applications. Surprisingly, no study has been reported on electrochemical synthesis of PEDOS on flexible substrate, and its optoelectronic properties. In this work, electropolymerization of 3,4-ethylenedioxyselenophene (EDOS) on flexible (ITO/PET) as well as rigid (ITO/glass) substrates, followed by cyclic voltammetry, electrochemical stability, morphology, spectroelectrochemical, and electrochromic properties of the PEDOS films were studied. For comparison purpose, poly(3,4-ethylenedioxythiophene) (PEDOT) films were also prepared on both flexible and rigid substrates and a throughout comparison was made. It has been observed that the polymer films on flexible substrates are relatively more stable, rough, and show blue shift in absorption spectra as compared to the polymer films on rigid substrates. On repeated bending, polymers films on flexible substrate exhibits good mechanical stability. Moreover, polymer film on flexible substrate has improved contrast ratio than that of polymer film on rigid substrate, whereas no significant change of response time has been observed. To the best of our knowledge, electropolymerization of EDOS on flexible substrate has been reported for the first time.

TFT-LCD Contrast Ratio Improvement by Using Design for Six Sigma Disciplines

The current market demands for thin-film transistor (TFT) liquid crystal display (LCD) is high; however, the LCD televisions still have contrast ratio-related issues. To resolve this, researchers conventionally use trial and error methods for parameter optimization and adjustment. However, this method is slow and can delay the development of new products. Therefore, this study focused on the high contrast ratio of the in-plane switching (IPS) panel. The Define–Measure–Analyze–Design–Verify procedure, comprising the methodology of the Design for Six Sigma, was used to help the researchers enhance the ultra-high contrast ratio of LCD panels. In this study, customer requirements were confirmed, after which the quality function deployment method was used to establish the technical requirements of the enhanced high contrast ratio of LCD. The contradiction matrix of TRIZ was then used to find the corresponding principles and thus propose the design scheme for the LCD contrast ratio. Methodologies, such as design failure modes and effect analysis, Taguchi’s parameter design, and reliability tests were used to enhance the ultra-high LCD contrast ratio. After the implementation of an actual case, the ultra-high contrast ratio of LCD panel was enhanced to 1000000:1; the benefits of such an improvement exceeded U.S. \\(9.5 million. This has also driven market orders for TFT IPS LCD. This study can serve as a reference for product design, product performance enhancement, pilot run yield improvement, and patent applications of LCD panel plants.

P‐38: Improved contrast ratio of TFT‐LCDs for automotive applications by optimizing retardation films and color filters

The effects of inserted retardation films and color filters were investigated for improving contrast ratio of in‐plane‐switchingmode TFT‐LCDs. Contrast ratios with horizontally wide viewing angles corresponding to automotive applications were increased by optimizing optical characteristics of the retardation films. The effects of color filters on the contrast ratio were also investigated by comparing optical characteristics of fabricated samples.

Dynamic coherence factor based on the standard deviation for coherent plane-wave compounding

The ultrafast imaging technique based on plane wave transmission has been a commonly investigated imaging mode in medical ultrasound imaging. Coherent plane-wave compounding (CPWC) was proposed to improve the quality of plane-wave imaging (PWI), which obtained a high-quality image by summing the low-quality images formed by transmitting plane waves at different steering angles. Coherence factor (CF) weighting algorithms can effectively improve image contrast with low computational complexity. However, this usually introduces black artifacts and degraded speckle quality. In this paper, we propose a dynamic coherence factor (DCF) that is based on the angular difference of CPWC to adaptively determine the number of plane waves and utilizes several plane waves with small angular difference to evaluate coherence. To improve resolution and contrast-to-noise ratio (CNR), adjusted DCF (ADCF) introduces a parameter related to the standard deviation to adjust DCF. Furthermore, a square neighborhood ADCF (SN-ADCF) using a 2-dimensional average filter is designed to obtain higher contrast and speckle quality. The simulated, experimental and in-vivo datasets are used to evaluate the proposed methods. Results show that, in comparison with CF, DCF can achieve improved contrast ratio (CR), CNR and speckle signal-to-noise ratio (sSNR). ADCF achieves a maximal lateral full width at half maximum (FWHM) improvement by 40% and better speckle quality than CF. SN-ADCF causes about 20% improvements upon CF in CNR and sSNR, while maintaining a similar resolution performance. SN-ADCF also provides higher lateral resolution than the generalized coherence factor (GCF) and scaled coherence factor (scCF), meanwhile obtaining a comparable contrast and speckle quality. Therefore, SN-ADCF has a satisfying comprehensive performance, which can achieve a reasonable balance among resolution, contrast and speckle quality.

Design and analysis of multi-hexagonal reversible encoder using photonic crystals

In this paper, a 4 × 2 reversible encoder with hexagonal lattice has been designed using two-dimensional photonic crystals with non-linear refractive index. In order to demonstrate the working of the encoder, we have used the multi-hexagonal shaped structure arranged in parallel with appropriate inclination to get the desired output. During its functionality as an encoder, more than 98% of the power is coupled at the output port to obtain logic 1 and less than 17.2% of the power is coupled for obtaining logic 0. In addition, during its functionality as a reversible encoder, the logic 1 and logic 0 correspond to 97.5% and 15.1%, respectively. The proposed encoder provides an improved contrast ratio of 12.18 dB and 11.5 dB for logical states of 01 and 10, respectively.