Distortion-Free Data Embedding Scheme for High Dynamic Range Images

Distortion-free data embedding is a technique which can assure that not only the secret data is correctly extracted but also the cover media is recovered without any distortion after secret data is extracted completely. Because of these advantages, this technique attracts the attention of many researchers. In this paper, a new distortion-free data embedding scheme for high dynamic range （HDR） images is proposed. By depending on Cartesian product, this scheme can obtain higher embedding capacity while maintaining the exactly identical cover image and stego image when using the tone mapping algorithms. In experimental results, the proposed scheme is superior to Yu et aL＇s scheme in regard to the embedding rate——an average embedding rate of 0.1355 bpp compared with Yn et aL＇s scheme （0.1270 bpp）.

Multi-exposure fusion for high dynamic range scene

Due to the existing limited dynamic range a camera cannot reveal all the details in a high-dynamic range scene. In order to solve this problem,this paper presents a multi-exposure fusion method for getting high quality images in high dynamic range scene. First,a set of multi-exposure images is obtained by multiple exposures in a same scene and their brightness condition is analyzed. Then,multi-exposure images under the same scene are decomposed using dual-tree complex wavelet transform( DT-CWT),and their low and high frequency components are obtained. Weight maps according to the brightness condition are assigned to the low components for fusion. Maximizing the region Sum Modified-Laplacian( SML) is adopted for high-frequency components fusing. Finally,the fused image is acquired by subjecting the low and high frequency coefficients to inverse DT-CWT.Experimental results show that the proposed approach generates high quality results with uniform distributed brightness and rich details. The proposed method is efficient and robust in varies scenes.

Analysis of Wide-Bandgap Material OPFET UV Detectors for High Dynamic Range Imaging and Communication Applications

The ultraviolet (UV) photoresponses of Wurtzite GaN, ZnO, and 6H-SiC-based Optical Field Effect Transistor (OPFET) detectors are estimated with an in-depth analysis of the same considering the generalized model and the front-illuminated model for high resolution imaging and UV communication applications. The gate materials considered for the proposed study are gold (Au) and Indium-Tin-Oxide (ITO) for GaN, Au for SiC, and Au and silver dioxide (AgO2) for ZnO. The results indicate significant improvement in the Linear Dynamic Range (LDR) over the previously investigated GaN OPFET (buried-gate, front-illuminated and generalized) models with Au gate. The generalized model has superior dynamic range than the front-illuminated model. In terms of responsivity, all the models including buried-gate OPFET exhibit high and comparable photoresponses. Buried-gate devices on the whole, exhibit faster response than the surface gate models except in the AgO2-ZnO generalized OPFET model wherein the switching time is the lowest. The generalized model enables faster switching than the front-illuminated model. The switching times in all the cases are of the order of nanoseconds to picoseconds. The SiC generalized OPFET model shows the highest 3-dB bandwidths of 11.88 GHz, 36.2 GHz, and 364 GHz, and modest unity-gain cut-off frequencies of 4.62 GHz, 8.71 GHz, and 5.71 GHz at the optical power densities of 0.575 μW/cm2, 0.575 mW/cm2, and 0.575 W/cm2 respectively. These are in overall, the highest detection-cum-amplifi-cation bandwidths among all the investigated devices. The same device exhibits the highest LDR of 73.3 dB. The device performance is superior to most of the other existing detectors along with comparable LDR, thus, emerging as a high performance photodetector for imaging and communication applications. All the detectors show considerably high detectivities owing to the high responsivity values. The results have been analyzed by the photovoltaic and the photoconductive effects, and the series resistance effects and will aid in conducting further research. The results are in line with the experiments and the commercially available software simulations. The devices will greatly contribute towards single photon counting, high resolution imaging, and UV communication applications.

Improvement of High Dynamic Range Capacitive Displacement Sensor by a Globalm Planarization

This study presents an improvement of high dynamic range contact-type capacitive displacement sensor by applying planarization. The sensor is called the contact-type linear encoder-like capacitive displacement sensor (CLECDiS), is a nano-meter-resolution sensor with a wide dynamic range. However, height differences due to patterned electrodes may cause a variety of problems or performance degradation. In devices of two glass wafer surfaces with patterned structures assembled face-to-face and in sliding contact, the heights of the patterns crucially affect their performance and practicality, so it should be planarized for reducing the problem. A number of techniques for planarizing glass wafer surfaces with patterned chrome electrodes were evaluated and the following three were selected as adequate: lift-off, etch-back, and chemical mechanical polishing (CMP). The fabricated samples showed that CMP provided the best planarization. CMP was successfully employed to produce CLECDiS with improved signal reliability due to reduced collisions between electrodes.

Novel Logarithmic Active Pixel Sensor with High Dynamic Range and High Output Swing

The logarithmic response complementary metal oxide semiconductor （CMOS） image sensor provides a wide dynamic range, but its drawback is the lack of simple fixed pattern noise（FPN） cancellation scheme. Designed is a novel logarithmic active pixel sensor（APS） with high dynamic range and high output swing. Firstly, the operation principle of mixed-model APS is introduced. The pixel can work in three operation modes by choosing the proper control signals. Then, FPN sources of logarithmic APS are analyzed, and double-sampled technique is implemented to reduce FPN. Finally, according to the simulation results, layout is designed and has passed design rule check（DRC）, electronic rule eheck（ERC） and layout versus schematic（LVS） verifications, and the post-simulation results are basically in agreement with the simulation results. Dynamic range of the new logarithmic APS can reach about 140 dB; and the output swing is about 750 inV. Results show that by using double sampled technique, most FPN is eliminated and the dynamic range is enhanced.

Shape recovery using high dynamic range images

An effective method for object shape recovery using HDRIs （high dynamic range images） is proposed. The radiance values of each point on the reference sphere and target object are firstly calculated, thus the set of candidate normals of each target point are found by comparing its radiance to that of each reference sphere point. In single-image shape recovery, a smoothness operation is applied to the target normals to obtain a stable and reasonable result; while in photometric stereo, radiance vectors of reference and target objects formed due to illuminations under different fight source directions are directly compared to get the most suitable target normals. Finally, the height values can be recovered from the resulting normal field. Because diffuse and specular reflection are handled in an unified framework with radiance, our approach eliminates the limitation presented in most recovery strategies, i.e., only Lambertian model can be used. The experiment results from the real and synthesized images show the performance of our approach.

Fast Scheme for Projective Geometric Correction and Edge Blending Based on High Dynamic Range Images

With the development of graphic processing unit(GPU)power,it is now possible to implement geometric correction and edge blending functions on a single computer.However,the processing resources consumed by the geometric correction and edge blending phases still burden the system and slow down the main application considerably.A new platform independent scheme is proposed,minimizing the negative influence on performance.In this scheme,parameters for geometric correction and edge blending are firstly defined in an interactive way and recorded as a 32-bit high dynamic range(HDR) image,which is then used by high level shading language(HLSL) codes embedded in the main application as a lookup table,greatly reducing the computational complexity and enhancing flexibility.

High Dynamic Range Image Fusion Based on Wavelet

With the developpment of image fusion technology and the maturity of wavelet theory, wavelet transform with its good time-frequency characteristics stands out in the field of image fusion. On the basis of wavelet transforms theory, this article proposes a high dynamic range imaging confusion method which combines with wavelet decomposition. First, perform a wavelet multi-scale decomposition to the two registered source image; then conduct wavelet inverse transform to the decomposed images. This paper focuses on the characteristics of high frequency and low frequency domain after wavelet decomposition,using different fusion methods in each of the frequency domain, finally obtain the fused image through inverse wavelet transform image reconstruction. The simulation results and evaluation index results show that, compared with other similar methods, this method is better in retaining the original image's details information, and improves the quality of fusion image.

A high gain wide dynamic range transimpedance amplifier for optical receivers

As the front-end preamplifiers in optical receivers, transimpedance amplifiers （TIAs） are commonly required to have a high gain and low input noise to amplify the weak and susceptible input signal. At the same time, the TIAs should possess a wide dynamic range （DR） to prevent the circuit from becoming saturated by high input currents. Based on the above, this paper presents a CMOS transimpedance amplifier with high gain and a wide DR for 2.5 Gbit/s communications. The TIA proposed consists of a three-stage cascade pull push inverter, an automatic gain control circuit, and a shunt transistor controlled by the resistive divider. The inductive-series peaking technique is used to further extend the bandwidth. The TIA proposed displays a maximum transimpedance gain of 88.3 dBΩ with the -3 dB bandwidth of 1.8 GHz, exhibits an input current dynamic range from 100 nA to 10 mA. The output voltage noise is less than 48.23 nV/√Hz within the -3 dB bandwidth. The circuit is fabricated using an SMIC 0.18 μm 1P6M RFCMOS process and dissipates a dc power of 9.4 mW with 1.8 V supply voltage.

A wideband large dynamic range and high linearity RF front-end for U-band mobile DTV

A wideband large dynamic range and high linearity U-band RF front-end for mobile DTV is introduced, and includes a noise-cancelling low-noise amplifier （LNA）, an RF programmable gain amplifier （RFPGA） and a current communicating passive mixer. The noise/distortion cancelling structure and RC post-distortion compensation are employed to improve the linearity of the LNA. An RFPGA with five stages provides large dynamic range and fine gain resolution. A simple resistor voltage network in the passive mixer decreases the gate bias voltage of the mixing transistor, and optimum linearity and symmetrical mixing is obtained at the same time. The RF front-end is implemented in a 0.25 #m CMOS process. Tests show that it achieves an IIP3 （third-order intercept point） of -17 dBm, a conversion gain of 39 dB, and a noise figure of 5.8 dB. The RFPGA achieves a dynamic range of-36.2 to 23.5 dB with a resolution of 0.32 dB.

Single-shot cross-correlator for pulse-contrast characterization of high peak-power lasers

Pulse contrast is a crucial parameter of high peak-power lasers since the prepulse noise may disturb laser–plasma interactions. Contrast measurement is thus a prerequisite to tackle the contrast challenge in high peak-power lasers.This paper presents the progress review of single-shot cross-correlator(SSCC) for real-time contrast characterization.We begin with the key technologies that enable an SSCC to simultaneously possess high dynamic range(1010), large temporal window(50–70 ps) and high fidelity. We also summarize the instrumentation of SSCC prototypes and their applications on five sets of petawatt laser facilities in China. Finally, we discuss how to extend contrast measurements from time domain to spatiotemporal domain. Real-time and high-dynamic-range contrast measurements, provided by SSCC, can not only characterize various complex noises in high peak-power lasers but also guide the system optimization.

低频大幅隔振器设计及实验

为了突破传统隔振器刚度和承载能力之间的矛盾,需要隔振器具有高的静态刚度,低动态刚度的特性.如今的准零刚度隔振器技术可以实现低频微幅隔振,但是对于大幅振动,隔振效果并不明显甚至失效,因此突破宽幅隔振成为隔振领域亟待解决的问题.为此,我们利用多稳态折纸通过并联装配的方式,构造具有宽幅零刚度区间的折纸型隔振器,以解决传统隔振器振动抑制幅值较低的问题.本文建立了宽零刚度隔振器模型,提出宽幅零刚度的设计方法,并通过动力学分析分析了模型的隔振效果.最后搭建试验样机,验证了理论的正确性.这种设计打破了传统准零刚度隔振器单点准零的设计准则,能够在一个大幅范围内保证稳定性,同时实现零刚度,极大拓宽了隔振器的适用范围.这种设计理念能够被用在新隔振材料设计和航空、船舶等大幅低频动态环境中.

基于动态阈值和差异性检验的自训练算法

针对自训练算法在迭代训练分类器的过程中存在难以有效选取高置信度样本以及误标记样本错误累积的问题,本文提出了基于动态阈值和差异性检验的自训练算法。引入样本的局部离群因子,据此剔除有标签样本中的离群点以及分类标注无标签样本,依据标注分批次处理无标签样本,以使模型更易选取到高置信度的无标签样本;根据新增伪标签样本的数量和对比隶属度的变化,设计一种动态隶属度阈值函数,提升高置信度样本的质量;定义密集距离度量样本间的差异性,分别计算伪标签样本与同类和不同类样本之间的密集距离之和,从而找出不确定度高的伪标签样本,并将此类样本并入下轮训练的无标签样本集中,缓解误标记样本错误累积的问题。实验结果表明,该算法在12个UCI基准数据集上均取得理想效果。

极端曝光图像的多尺度分解细节感知融合算法

针对极端曝光(欠曝光和过曝光)图像动态范围低的问题,提出一种基于多尺度分解细节感知的图像融合算法。欠曝光图像经过细节增强后,与过曝光图像进行初步的粗融合;采用小波变换对细节增强后图像的亮度分量进行多尺度分解,并设计专门的高频和低频融合策略,实现亮度分量的精融合;将粗融合图像的色调、饱和度分量,与精融合图像的亮度分量重组,获得最终的融合结果。基于大量测试数据,实验结果表明所提方法在视觉效果方面表现优异,平均MEF-SSIM指标为0.9854,平均SSIM指标为0.6508,均优于现有主流算法。

高动态范围条纹结构光在机检测技术及应用进展

条纹结构光技术是近年来发展迅速的非接触式测量方法,为机械加工在机检测提供了新的解决方案。由于加工环境光线复杂且金属零件本身具有高反光的特性,造成结构光在机检测的精度降低。将高动态范围(High Dynamic Range,HDR)技术应用于结构光检测中,可抑制高反光的影响,实现金属零件在复杂场景的测量。本文首先介绍了结构光测量原理,总结出HDR结构光在机检测面临的难点;其次,对HDR结构光技术进行了全面综述,以机械加工在机检测为背景,对基于硬件设备的HDR技术和基于条纹算法的HDR技术分别进行了归纳分析;然后,根据在机检测的条件需求,对各类技术进行总结,并比较不同方法的优缺点和在机检测的适用性;最后,结合近年来先进制造技术和精密测量的研究热点,对潜在应用进行分析,提出技术展望。

基于自适应多曝光融合的高动态范围表面测量方法

为解决结构光测量高动态范围表面物体时出现局部过度曝光或曝光不足的问题,提出一种改进的多曝光融合方法,利用自适应曝光代替手动曝光,并对图像融合过程进行优化。首先,将初始曝光时间下拍摄的图像利用直方图进行分析,将被测物体表面反射率不同的区域分为若干组,分别计算出每个组别的最佳曝光时间;在此基础上,拍摄不同组别对应最佳曝光时间下投射白光和条纹的图像,并去除图像中超过设定阈值的高灰度值区域,再将投射白光处理后的图像制作成掩模图,与相同曝光时间下投射条纹处理后的图像相乘,进而对多组相乘后的图像进行亮度压缩与融合;最后,通过CLAHE算法提高融合后所生成条纹图的对比度与清晰度,并对条纹解相后进行点云重建和尺寸测量。实验结果表明:文中方法中自适应曝光相较于手动曝光具有高效性和准确性,U型卡、连接块、圆盘三个高动态范围表面物体的点云重建率分别高达99.98%、99.74%、99.76%,测量出的标准块阶梯高度差绝对误差为0.062 mm,相对误差仅为0.69%,该方法有效解决了高动态范围表面物体测量时点云缺失的问题,提高了三维轮廓的测量精度。

基于三通道并行的高反光物体三维形貌测量

传统条纹投影技术测量高反光物体时因过度曝光导致相机失真,而常用的多重曝光时间法采集图像数量过多、耗时过长,为此提出了一种基于三通道并行的条纹投影强度预测与图像融合的方法。该方法根据被测物体的光强直方图分布计算条纹最佳投影光强比例关系,投影对应的红绿蓝条纹。利用彩色相机在多光通道下对投影条纹的不同响应,分离对应条纹图像并选择其中不饱和并且调制度最大的像素生成各自通道的图像掩膜,根据三通道下的掩膜图像和条纹图像合成高动态范围条纹图。通过相位解算与系统标定,最终恢复出高反光金属平面与球面零件的三维形貌。实验结果表明,该方法测量误差减小至传统方法的61.2%,同样采集12张条纹图像,仅增加1张预投影图像,提高系统适应性的同时也提升了测量精度。

星载高动态范围差分吸收成像光谱仪成像电路设计及实现

星载差分吸收成像光谱仪通常运行于太阳同步轨道,探测地表反射光的光谱并根据特征气体的谱线吸收强度测量区域内某些痕量气体浓度。第一代星载差分吸收光谱仪受限于探测器性能等原因,探测的动态范围不大,造成暗背景下数据信噪比低,亮背景下像元饱和。随着更大阱深,更高速度的探测器出现,第二代高动态范围的差分吸收成像光谱仪得以实现。本文介绍了高动态范围的差分吸收光谱仪成像电路的研制过程,包括器件选型,电路方案及电路测试,并对测试结果进行了分析。重点讨论了高动态范围的实现,给出了单点测量值的概念,提出了最大单点测量值的计算公式,解释了最大单点测量值与动态范围的关系,并评估了探测器件的单点探测能力,同时规划了未来进一步提高动态范围的方法,从而为同类设备的研制提供参考。

基于多特征融合的人像HDR图像处理算法

基于深度学习的高动态范围(High Dynamic Range,HDR)图像处理算法在处理含有人像的图片时存在皮肤偏色问题。针对此问题,本文提出了一种基于多特征融合的人像HDR图像处理算法U2HDRnet。该算法由皮肤特征提取模块、三边特征提取模块、色彩重建模块3部分构成。首先,皮肤特征提取模块分离出皮肤区域的颜色和位置信息;其次,三边特征提取模块分别提取图片的局部特征、全局特征和语义特征,并与皮肤特征融合;最后,色彩重建模块对网格做空间和颜色深度上的插值。此外,本文引入改进的自注意力与卷积融合模块以提升HDR的处理效果;同时本文还制作了人像HDR数据集PortraitHDR,填补了该领域内数据集的空白。实验结果显示,U2HDRnet的PSNR达31.42 dB,SSIM达0.985,均优于目前常见的HDR算法,在获得高质量人像HDR图像的同时避免了皮肤的失真。

人工智能在图像增强技术中的应用

电视技术在人工智能时代(AI,Artificial Intelligence)迎来了新的发展机遇。其中图像增强技术在AI的赋能下,取得了前所未有的进展。本文面向超分辨率、低照度增强和高动态范围三种常见的图像增强技术,以本团队的相关工作为线索,从一个切面介绍“AI+广电”发展现状,并就其发展趋势展开思考。