Digital image forensics

This tutorial explains how photo-response nonuniformity (PRNU) of imaging sensors can be used for a variety of important digital forensic tasks, such as device identification, device linking, recovery of processing history, and detection of digital forgeries. The PRNU is an intrinsic property of all digital imaging sensors due to slight variations among individual pixels in their ability to convert photons to electrons. Consequently, every sensor casts a weak noise-like pattern onto every image it takes. This pattern, which plays the role of a sensor fingerprint, is essentially an unintentional stochastic spread-spectrum watermark that survives processing, such as lossy compression or filtering. This tutorial explains how this fingerprint can be estimated from images taken by the camera and later detected in a given image to establish image origin and integrity. Various forensic tasks are formulated as a two-channel hypothesis testing problem approached using the generalized likelihood ratio test. The performance of the introduced forensic methods is briefly illustrated on examples to give the reader a sense of the performance.     

Computational cameras: convergence of optics and processing

A computational camera uses a combination of optics and processing to produce images that cannot be captured with traditional cameras. In the last decade, computational imaging has emerged as a vibrant field of research. A wide variety of computational cameras has been demonstrated to encode more useful visual information in the captured images, as compared with conventional cameras. In this paper, we survey computational cameras from two perspectives. First, we present a taxonomy of computational camera designs according to the coding approaches, including object side coding, pupil plane coding, sensor side coding, illumination coding, camera arrays and clusters, and unconventional imaging systems. Second, we use the abstract notion of light field representation as a general tool to describe computational camera designs, where each camera can be formulated as a projection of a high-dimensional light field to a 2-D image sensor. We show how individual optical devices transform light fields and use these transforms to illustrate how different computational camera designs (collections of optical devices) capture and encode useful visual information.     

Research on a novel imaging bionic polarization navigation sensor for glimmer environment application

Polarization navigation system is a hotspot in the field of bionic navigation. Compared with point source polarized light navigation sensor, the polarization information acquisition method based on image sensor and imaging technology has better robustness, and it can obtain more polarization information. In this paper, an embedded imaging polarization sensor for glimmer environment application is designed and developed. The multi-channel video processing technology of TMS320DM642 is used to capture the polarization information of charge coupled device (CCD) camera with three channels. The images are processed by digital signal processer (DSP) in real time, and the angle of polarization (AOP) image is calculated simultaneously with an acquisition and calculation speed of 10 frame per second. Sensor can obtain absolute rotation angle, and the AOP image can be displayed on liquid crystal display (LCD). It provides an effective experimental platform for the research of imaging polarization mode navigation device based on embedded system.     

Image capture: simulation of sensor responses from hyperspectralimages

This paper describes the design and performance of an image capture simulator. The general model underlying the simulator assumes that the image capture device contains multiple classes of sensors with different spectral sensitivities and that each sensor responds in a known way to irradiance over most of its operating range. The input to the simulator is a set of narrow-band images of the scene taken with a custom-designed hyperspectral camera system. The parameters for the simulator are the number of sensor classes, the sensor spectral sensitivities, the noise statistics and number of quantization levels for each sensor class, the spatial arrangement of the sensors and the exposure duration. The output of the simulator is the raw image data that would have been acquired by the simulated image capture device. To test the simulator, we acquired images of the same scene both with the hyperspectral camera and with a calibrated Kodak DCS-200 digital color camera. We used the simulator to predict the DCS-200 output from the hyperspectral data. The agreement between simulated and acquired images validated the image capture response model and our simulator implementation. We believe the simulator will provide a useful tool for understanding the effect of varying the design parameters of an image capture device.     

CMOS图像传感器在数码相机中的应用

对CMOS与CCD图像传感器的特点及其在数码相机中的应用进行了讨论，着重研究了CMOS图像传感器芯片的应用及其发展前景，针对CMOS图像传感器的特点设计了一个完整的数码相机，并利用PC机中的图像处理软件处理和显示所拍摄的图片。     

Adaptive-Quantization Digital Image Sensor for Low-Power Image Compression

The recent emergence of new applications in the area of wireless video sensor network and ultra-low-power biomedical applications (such as the wireless camera pill) have created new design challenges and frontiers requiring extensive research work. In such applications, it is often required to capture a large amount of data and process them in real time while the hardware is constrained to take very little physical space and to consume very little power. This is only possible using custom single-chip solutions integrating image sensor and hardware-friendly image compression algorithms. This paper proposes an adaptive quantization scheme based on boundary adaptation procedure followed by an online quadrant tree decomposition processing enabling low power and yet robust and compact image compression processor integrated together with a digital CMOS image sensor. The image sensor chip has been implemented using 0.35-mum CMOS technology and operates at 3.3 V. Simulation and experimental results show compression figures corresponding to 0.6-0.8 bit per pixel, while maintaining reasonable peak signal-to-noise ratio levels and very low operating power consumption. In addition, the proposed compression processor is expected to benefit significantly from higher resolution and Megapixels CMOS imaging technology     

数码相机在自动气象站中的应用

通常传统自动气象站只能采集常规的气象数据,如：温度、湿度、风力等,而无法采集自动气象站当地的高分辨率图像信息,通过对奥林巴斯数码相机进行研究,采用奥林巴斯提供的CAMEDIA SDK 3.3开发套件,设计了一套基于高分辨数码相机的自动气象站图像采集和传输系统。系统通过自动站的高分辨率数码相机远程采集图像,并通过网络传输到数据中心,实现了自动气象站对当地图像信息的采集与传输。着重介绍分析了数码相机在系统中的应用,并实现了图像数据的自动采集功能。 更多还原     

基于FPGA的工业数字摄像机系统的设计

针对传统工业数字摄像机的灵活性差、实时性差等缺点,设计了一种基于FPGA的工业数字摄像机系统。将工业数字摄像机与FPGA结合起来,利用FPGA通过I2 C总线接口控制器控制图像传感器采集图像数据,然后将Bayer格式图像转化为RGB格式图像,通过调用Altera IP核DDRII SDRAM controller with ALTMEMPHY和FIFO存储器设计了DDR2SDRAM的接口,将图像数据缓存到DDR2存储器中,最后通过SPI总线接口在液晶屏上显示图像,可达到53帧/s图像的速度。系统代码共需约5 000个逻辑单元,3 704个寄存器,117个引脚。将设计代码下载到系统芯片中后,系统可以清晰显示所拍到的画面。设计结果表明,基于FPGA的工业数字摄像机设计灵活,易于移植,可实现高速图像采集和传输。     

低功耗CMOS视觉传感器新结构及其SOC实现

提出了一种新型单片CMOS摄像传感器电路的体系结构,该结构集成了摄像、噪声消除、模数转换、图像处理、图像增强、色彩空间转变等功能.采用该结构实现的CMOS视觉芯片动态范围大,在弱光和强光下均能拍摄图像;工作在30帧的情况下,消耗的功耗只有75 mW,具有低功耗的优点.基于该单芯片低功耗CMOS视觉传感器芯片开发的系统元器件少,可广泛应用于手机拍照、数码相机和网络视频等多媒体终端.     

Unconventional Image-Sensing and Light-Emitting Devices for Extended Reality

Extended reality (XR) refers to a space where physical and digital elements coexist and comprises three elements, namely, environment, human, and computer, which interact with each other. Image sensors and displays are the core elements of XR systems because visual information is important for recognizing and judging objects. Recently, new features of image sensors and displays that are useful for developing next-generation XR systems have been reported. For example, a miniaturized version of image sensors with the superb object detection and recognition capability offers new opportunities for machine vision technology. Furthermore, transparent and deformable displays are the key components of XR systems because they not only provide highly realistic virtual image information but also serve as efficient user interfaces. Herein, the recent progresses in such unconventional image sensors and display technologies are reviewed. First, image sensors with features of wavelength-selective photodetection for color discrimination, neuromorphic image acquisition for facile pattern recognition, and curved image sensor designs inspired by biological eyes for miniaturization and unconventional imaging performances are discussed. Then, light-emitting device technologies focusing on devices with transparency and deformable form factors are described. Finally, the review is concluded with a brief summary and a future outlook.     

Digital Camera Imaging System Simulation

A digital camera is a complex system including a lens, a sensor (physics and circuits), and a digital image processor, where each component is a sophisticated system on its own. Since prototyping a digital camera is very expensive, it is highly desirable to have the capability to explore the system design tradeoffs and preview the system output ahead of time. An empirical digital imaging system simulation that aims to achieve such a goal is presented. It traces the photons reflected by the objects in a scene through the optics and color filter array, converts photons into electrons with consideration of noise introduced by the system, quantizes the accumulated voltage to digital counts by an analog-to-digital converter, and generates a Bayer raw image just as a real camera does. The simulated images are validated against real system outputs and show a close resemblance to the images captured under similar condition at all illumination levels.     

基于DM6437的数字摄像机

为了适应现代采集系统的小型化以及数字化需要,设计了一种基于达芬奇技术DSP芯片的数字图像采集系统。这种设计方法不需要外接编解码芯片,直接连接数字摄像头,减少了D/A转换带来的图像干扰,同时利用了达芬奇系列DSP上集成的视频处理子系统组件(VPSS),其中的视频处理前端(VPFE)以硬件方式对数字视频图像进行视频采集、CFA插值、色彩空间变换等图像预处理操作,简化了软件设计。结果显示,该系统采集到的视频图像清晰、稳定、色彩均衡,满足普通摄像机对视频图像的要求。     

基于Wi—FiDirect的农业图像采集系统设计

农业大棚所处环境偏远,通用的无线网基站难以很好覆盖,导致信号不强、通信不畅。提出了一种基于Wi—Fi Direct无线通信的图像采集系统。该系统采用Linux操作系统与ARM9s3C2440作为软硬件开发平台,将CMOS OV9650摄像头作为图像传感器,利用Wi—Fi Direct无线通信将采集到的图像信息发送至远程监控终端,上位机监控界面用LabVIEW开发。给出了图像采集系统的软硬件设计方案及测试结果。结果表明,该系统硬件结构小、运行稳定,最大优势是传输速率快,不用路由器就能组网实现远程图像的实时传输,在农业方面具有一定的实用价值。     

An addressable 256×256 photodiode image sensor array with an 8-bit digital output

We have constructed an addressable 256 × 256 photodiode sensor array together with an 8-bit ADC (analog-to-digital converter) on the same chip. Such a digital camera is easy to connect to a computer where also the flexibility of the computer can be used to control the camera output. The sensor has been constructed in two versions. The first version was implemented with a 256-column parallel-bit-slice image processor on the same die in a commercial project and the second as a separate addressable digital image sensor. The sensor was functionally fabricated using 1.6 µm design rules in a 1.2 µm CMOS process where it required a total area of 96 mm².     

Vertically integrated sensors for advanced imaging applications

A thin film on ASIC (TFA) image sensor is fabricated depositing an amorphous silicon thin-film detector onto a CMOS ASIC. With regards to advanced imaging systems, TFA provides enhanced performance and more flexibility than conventional technologies. Extensive on-chip signal processing is feasible, as well as small pixels for high resolution imagers. Two new TFA imager prototypes have recently been fabricated. High-resolution image sensor (HIRISE II) with 1024×128 pixels is an active pixel sensor suited for digital photography. Local autoadaptiver sensor (LARS II) with 368×256 pixels splits the illumination information into two signals, thereby providing a dynamic range of more than 120 dB, as required by automotive applications. Both prototypes include correlated double sampling and double delta sampling for efficient suppression of fixed pattern noise     

高光谱成像系统在中医舌诊中的应用研究

舌诊是传统中医诊病的重要方法,然而传统舌诊中存在一个很大的问题是具有主观性,难于进行定量化描述.随着计算机技术的发展,图像处理和模式识别技术正在用于舌诊的辅助诊断.目前舌图像的采集方法基本都是使用数码相机,所提供的舌图像包含的病理信息有限,使得分析算法非常复杂且效果不甚理想.针对这种情况,提出使用高光谱成像系统代替数码相机进行舌图像的采集.由于高光谱舌图像具有丰富的图谱信息,初步试验表明了这一方法的有效性,为中医舌诊提供了一种新方法.     

可用于数码相机的新型滤色器实验研究

目前的数码相机获取彩色大多是由棋盘格状Ｂａｙｅｒ型滤色器与ＣＣＤ构成彩色成像器件获得。本文则提出了一种新型格式的滤色器,其不仅具有三原色空间周期采样的特点,同时又具有三色光栅编码的特点,即编码数字图像的频谱面上红、绿和蓝信号相互分离。本文的分析表明这种滤色器和Ｂａｙｅｒ型相比具有解码步骤较为简单的优点。本文特殊设计的模拟实验验证了其用于数码摄影的实际效果。     

基于灰度投影的快速电子稳像算法

提出的基于灰度投影的快速电子稳像算法是将两维图像转化为一维投影曲线,然后进行一维相关运算求出运动矢量,因此计算量小速度快,且算法是对灰度图像进行直接处理,处理的信息反映了图像的整体特征并有效地抑制了噪声,因此具有较高的稳像精度.该算法经试验证明具有较好的稳像效果,并已进行了基于FPGA的硬件实现.     

基于成像时刻校准的混合域TDICMOS成像技术研究

随着航天遥感领域超高分辨率成像电子学中行频的不断提升，一个积分时间内光生电荷数量逐渐减少，弱光成像能力有所下降，电子学中需要采用增大时间延迟积分级数的方法弥补能量的不足。传统数字域累加探测器有着引入过多噪声与帧频受限的多项弊端，而电荷域探测器的超大级数累加会带来电荷转移效率的下降和图像的混叠。基于此，文章在采用低功耗、高集成度TDICMOS基础上，提出了一种基于电荷域和数字域混合的新型累加方式，并对影响弱光成像像质水平的主要指标进行分析。随后针对混合域累加方式下多感光单元间的像质退化，提出一种基于图像配准的成像时刻校准方法，通过多片感光单元间隔测量和成像时刻时序微调有效改善了大积分级数电荷运动与景物运动的失配程度。最后通过滚筒测试验证了成像时刻校准方法的有效性，通过性能测试验证了混合域成像在弱光照下探测能力的提升。结果表明，文中所提方法有效地解决了TDI型探测器的主要瓶颈，为超高分辨率遥感相机提供了有效的解决方案。     

星敏感器地基评测系统的设计研究

为了能够方便、准确地评价星敏感器的成像质量,设计了一款专门用于评价成像质量的图像采集系统。该系统基于PCI总线接口,以FPGA作为核心控制逻辑,用双SRAM的双缓存结构实现了图像数据的大量传输。在软件上采用多线程方法实现了图像的显示和存储,并加入了图像评价模块,从而精确检测出了星敏感器的工作性能。多次严格试验表明,该系统工作稳定、可靠,其采集的图像数据不失真。当系统运行在16位的情况下,其峰值图像传输速率可达到40 Mbps。