Smart-pixel-based network interface chip

We present the design and experimental setup of an optically interconnected smart-pixel network interface chip designed to implement a collisionless multichannel-access control protocol. The design demonstrates the cointegration of optoelectronic pixel modules of various levels of complexity for dense, high-speed interconnection of highly functional digital logic components typical of multiprocessor network routers.     

Denoising in digital speckle pattern interferometry using fast discrete curvelet transform

In digital speckle pattern interferometry, the denoising of speckle fringe patterns is of vital importance for quantitative extraction of phase distribution. A filtering method of fast discrete curvelet transform based on weighted average thresholding technique is proposed in this paper for noise removal in speckle fringe patterns. Both computer-simulated and experimental digital speckle pattern interferometry fringe patterns are adopted to evaluate the performance of the proposed filtering method. In addition, a widely used and representative filtering method, windowed Fourier filter, is introduced for making a comparison and validation in the image processing effect, and the parameter of peak signal noise ratio is also used for assessment of denoising effect. It is shown from the filtered results that the filtering method of fast discrete curvelet transform is effecitve to remove speckle noises and simultaneously preserve fringe structure information.     

Discrete correlation processor as a building core of a digital optical computing system: architecture and optoelectronic embodiment

In this paper we present a general-purpose discrete correlation processor (DCP) expected to be the building core block of a digital optical computing system. The DCP-1 is embodied by optoelectronic devices such as a VCSEL and a complementary metal-oxide silicon photodetector. The application targets of the DCP-1 are optical interconnection and various types of digital optical computing. It is expected that digital optical computing techniques coupled with the optoelectronic technology will provide large capability and flexibility in information processing. Introduction of a processing scheme of optical array logic enlarges the applicable field of the DCP-1 as well as its processing capability. With the experimental DCP-1 a bit error rate smaller than 10(-9) was obtained for A . B? operation under a 500-kHz clock rate.     

Holographic digital Fourier microscopy for selective imaging of biological tissue

We present an application of digital Fourier holography for selective imaging of scatterers with different sizes in turbid media such as biological tissues. A combination of Fourier holography and high‐resolution digital recording, digital Fourier microscopy (DFM) permits crucial flexibility in applying filtering to highlight scatterers of interest in the tissue. The high‐resolution digital hologram is a result of the collation of Fourier holographic frames to form a large‐size composite hologram. It is expected that DFM has an improved signal‐to‐noise ratio as compared to conventional direct digital imaging, e.g., phase microscopy, as applied to imaging of small‐size objects. The demonstration of the Fourier filtering capacity of DFM using a biological phantom represents the main focus of this article. © 2005 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 14, 253–258, 2004; Published online inWiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.20031     

Holographic optical coherence imaging of rat osteogenic sarcoma tumor spheroids

Holographic optical coherence imaging is a full-frame variant of coherence-domain imaging. An optoelectronic semiconductor holographic film functions as a coherence filter placed before a conventional digital video camera that passes coherent (structure-bearing) light to the camera during holographic readout while preferentially rejecting scattered light. The data are acquired as a succession of en face images at increasing depth inside the sample in a fly-through acquisition. The samples of living tissue were rat osteogenic sarcoma multicellular tumor spheroids that were grown from a single osteoblast cell line in a bioreactor. Tumor spheroids are nearly spherical and have radial symmetry, presenting a simple geometry for analysis. The tumors investigated ranged in diameter from several hundred micrometers to over 1 mm. Holographic features from the tumors were observed in reflection to depths of 500-600 microm with a total tissue path length of approximately 14 mean free paths. The volumetric data from the tumor spheroids reveal heterogeneous structure, presumably caused by necrosis and microcalcifications characteristic of some human avascular tumors.     

数字图象处理技术应用于温场分布在线测量

首先阐述在恶劣环境下的工业生产中采用成象光谱法来监测温场分布的理由 ,然后结合面阵 CCD成象技术和数字图象处理方法 ,选用恰当的波长搭配 ,进行合理的设计 ,研制出新的成象光谱数字图象温场监测装置。利用黑体的标定证实理论和设计的正确性 ,并在现场测试中取得满意的结果。     

Digital pulse processor for ion beam microprobe tomography

A digital pulse processor, suitable for 3D imaging with focused ion beam techniques, has been developed using a high performance FPGA (field-programmable gate array) and a high-level FPGA design tool. The hardware and software implementation of several components, including analog signal conditioning, trapezoidal filtering, and median filtering, are presented. The system is applied to the 3D STIM (scanning transmission ion microscopy) tomography technique.     

Design of adaptive digital filters for phase extraction in complex fringe patterns obtained using the Ronchi test

A powerful technique is presented for processing complex fringe patterns with high noise levels and arbitrary distributions of spatial frequencies, which can successfully extract the phase information. Artifacts that arise from phase extraction in local filtering approaches are avoided by using a simple design and implementation strategy for the adaptive filter, based on the theory of digital filter design used in electronics, and applied to pixel rows (or columns) in the fringe-pattern. The filter designed in this manner is then applied to phase extraction in an experimental fringe pattern measured in a digital Ronchi test setup using a Carré phase-shifting procedure. The filtering strategy has a very low computational cost and allows phase extraction in noisy ronchigrams regardless their spatial frequency distribution, provided the fringes are still visible.     

红外小目标图像预处理及FPGA实现

针对红外图像低对比度、低信噪比等特点,为提高红外小目标的探测能力,提出一种用于红外小目标预处理方法:在对图像进行热晕消除的基础上,结合空间数字滤波,形态学运算,能量累积及帧间分析等先进技术进行处理,采用大规模可编程门阵列(FPGA)来实现,实时给出高质量的图像信息。仿真证明,该方法是有效的。     

Chiro-Optoelectronic Encodable Multilevel Thin Film Electronic Elements with Active Bio-Organic Electrolyte Layer

It is suggested that chiral photonic bio-enabled integrated thin-film electronic elements can pave the base for next-generation optoelectronic processing, including quantum coding for encryption as well as integrated multi-level logic circuits. Despite recent advances, thin-film electronics for encryption applications with large-scale reconfigurable and multi-valued logic systems are not reported to date. Herein, highly secure optoelectronic encryption logic elements are demonstrated by facilitating the humidity-sensitive helicoidal organization of chiral nematic phases of cellulose nanocrystals (CNCs) as an active electrolyte layer combined with printed organic semiconducting channels. The ionic-strength controlled tunable photonic band gap facilitates distinguishable and quantized 13-bit electric signals triggered by repetitive changes of humidity, voltage, and the polarization state of the incident light. As a proof-of-concept, the integrated circuits responding to circularly polarized light and humidity are demonstrated as unique physically unclonable functional devices with high-level logic rarely achieved. The convergence between functional nanomaterials and the multi-valued logic thin-film electronic elements can provide optoelectronic counterfeiting, imaging, and information processing with multilevel logic nodes.     

高速数字采集系统通道间信号传输延迟时间分析

通道间信号传输延迟时间是多通道高速数字采集系统的一项重要评价指标.本文应用Hilbert Huang变换对采集到的单频正弦信号进行数字信号滤波处理,对滤波后的数据进行Hilbert变换得到信号的瞬时相位,可以精确识别信号源的频率,并能够方便地得到通道问信号传输延迟时间.为高速数字采集系统通道间信号传输延迟时间分析提供了...     

用于分数傅里叶域滤波位相元件设计新算法

基于部分相干成像和分数傅里叶变换理论,建立成像系统的分数傅里叶域滤波模型,提出了可快速设计分数域位相型滤波片的 FrPI 算法。此算法将逆向设计预设初位相与分数傅里叶迭代技术相结合,针对成像系统中不同的设计要求可快速设计出所需的分数域滤波片结构。模拟结果表明,对数值孔径有限的部分相干成像系统,使用新算法设计的分数域滤波片,可有效补偿由于高频损失带来的图像失真,从而使局部线宽偏差和面积偏差分别由滤波前的 36.548nm 和 39.09%下降到了 15.234nm 和 7.72%,明显减少了空间像畸变。     

Despeckling of medical ultrasound images

Speckle noise is an inherent property of medical ultrasound imaging, and it generally tends to reduce the image resolution and contrast, thereby reducing the diagnostic value of this imaging modality. As a result, speckle noise reduction is an important prerequisite, whenever ultrasound imaging is used for tissue characterization. Among the many methods that have been proposed to perform this task, there exists a class of approaches that use a multiplicative model of speckled image formation and take advantage of the logarithmical transformation in order to convert multiplicative speckle noise into additive noise. The common assumption made in a dominant number of such studies is that the samples of the additive noise are mutually uncorrelated and obey a Gaussian distribution. The present study shows conceptually and experimentally that this assumption is oversimplified and unnatural. Moreover, it may lead to inadequate performance of the speckle reduction methods. The study introduces a simple preprocessing procedure, which modifies the acquired radio-frequency images (without affecting the anatomical information they contain), so that the noise in the log-transformation domain becomes very close in its behavior to a white Gaussian noise. As a result, the preprocessing allows filtering methods based on assuming the noise to be white and Gaussian, to perform in nearly optimal conditions. The study evaluates performances of three different, nonlinear filters--wavelet denoising, total variation filtering, and anisotropic diffusion--and demonstrates that, in all these cases, the proposed preprocessing significantly improves the quality of resultant images. Our numerical tests include a series of computer-simulated and in vivo experiments.     

数字化光电跟踪伺服系统定位极限环的抑制

数字光电跟踪系统定位时将产生自振荡,在相平面下可描述为极限环。自振荡对定位精度影响较大,因此必须对其进行抑制。针对实际的数字光电跟踪伺服系统,提出一种描述方法,即用等效间隙非线性来描述其定位时非线性特性,且该间隙主要由光电传感器的滞后效应和伺服系统的摩擦死区引起。理论分析表明,双极PWM功率放大器的零点振颤特性可以抑制伺服系统的定位极限环。实验也证明,通过软件补偿以及PWM驱动模式设计来改善光电跟踪系统定位精度是可行的,定位精度由1.77提高到了22.23,大大抑制了定位非线性特性。     

Standard cell-based implementation of a digital optoelectronic neural-network hardware

A standard cell-based implementation of a digital optoelectronic neural-network architecture is presented. The overall structure of the multilayer perceptron network that was used, the optoelectronic interconnection system between the layers, and all components required in each layer are defined. The design process from VHDL-based modeling from synthesis and partly automatic placing and routing to the final editing of one layer of the circuit of the multilayer perceptrons are described. A suitable approach for the standard cell-based design of optoelectronic systems is presented, and shortcomings of the design tool that was used are pointed out. The layout for the microelectronic circuit of one layer in a multilayer perceptron neural network with a performance potential 1 magnitude higher than neural networks that are purely electronic based has been successfully designed.     

Extended depth of field through wave-front coding

We designed an optical-digital system that delivers near-diffraction-limited imaging performance with a large depth of field. This system is the standard incoherent optical system modified by a phase mask with digital processing of the resulting intermediate image. The phase mask alters or codes the received incoherent wave front in such a way that the point-spread function and the optical transfer function do not change appreciably as a function of misfocus. Focus-independent digital filtering of the intermediate image is used to produce a combined optical-digital system that has a nearly diffraction limited point-spread function. This high-resolution extended depth of field is obtained through the expense of an increased dynamic range of the incoherent system. We use both the ambiguity function and the stationary-phase method to design these phase masks.     

In vivo ultrasound biomicroscopy of skin: spectral system characteristics and inverse filtering optimization

High-frequency ultrasound (HFUS) in the 20 MHz to 100 MHz range has to meet the opposite requirements of good spatial resolution and of high penetration depth for in vivo ultrasound biomicroscopy (UBM) of skin. The attenuation of water, which serves as sound propagation medium between utilized single element transducers and the skin, becomes very eminent with increasing frequency. Furthermore, the spectra of acquired radio frequency (rf) echo signals change over depth because of the diffracted sound field characteristics. The reduction of the system's center frequency and bandwidth causes a significant loss of spatial resolution over depth. In this paper, the spectral characteristics of HFUS imaging systems and the potential of inverse echo signal filtering for the optimization of pulse-echo measurements is analyzed and validated. A Gaussian model of the system's transfer function, which takes into account the frequency-dependent attenuation of the water path, was developed. Predictions of system performance are derived from this model and compared with measurement results. The design of a HFUS skin imaging system with a 100 MHz range transducer and a broadband driving electronics is discussed. A time-variant filter for inverse rf echo signal filtering was designed to compensate the system's depth-dependent imaging properties. Results of in vivo measurements are shown and discussed.     

图像处理在密封条尺寸测量中的应用研究

通过工业摄像机获取密封条的图像,采用数字图像处理技术对图像进行分析处理和分析,实时提取密封条的几何特征,即密封条的宽度或厚度,可实现密封条的在线实时测量。但其测量精度会受一些条件的影响,如光线环境、图像采集设备的分辨率以及各种干扰等。文章讨论了密封条在线检测中的图像处理问题,对实现密待条的在线实时检测提供可能。