Design and demonstration of a miniature catheter for a confocal microendoscope

The fluorescence confocal microendoscope provides high-resolution, in vivo imaging of cellular pathology during optical biopsy. The confocal microendoscope employs a flexible fiber-optic catheter coupled to a custom-built slit-scan confocal microscope. The catheter consists of a fiber-optic imaging bundle linked to a miniature objective and focus assembly. The 3-mm-diameter catheter may be used on its own or routed though the instrument channel of a commercial endoscope, adding microscopic imaging capability to conventional endoscopy. The design and performance of the miniature objective and focus assembly are discussed. Primary applications of the system include diagnosis of disease in the gastrointestinal tract and female reproductive system.     

Variable zoom system with aberration correction capability

We describe experiments conducted with two deformable mirrors (DMs) at fixed locations in an optical microscope imaging system. In this configuration, the DM shapes are controlled to provide 2.5× zoom capability, to allow dynamic focus control and to compensate for aberrations of the fixed optical components. Zoom is achieved by simultaneously adjusting focal lengths of the two DMs, which are inserted between an infinity-corrected microscope objective and a tube lens. Image quality is measured using contrast modulation, and performance of the system is quantified, demonstrating an improved point spread function in the adaptively compensated system.     

激光干涉测量中光学窗口受动态压力的影响分析

利用激光干涉仪对动态压力进行非接触测量时,压力腔中常设计光学窗口,目的是在动态压力环境与激光干涉仪间建立光学通道,利用激光干涉法使动态压力能溯源到时间、长度与静态压力上。由于在动态压力环境下光学窗口受到内外压差、温度梯度、振动等因素影响,将直接影响光学测量精度。针对上述问题,通过仿真分析方法,分析在动态压力环境下压力、温度、振动与光学窗口的影响关系,同时通过光学窗口在动态压力环境下试验,研究各影响分量对真实测量结果的影响,可为后续动态压力的校准和测量进行修正和补偿以及其他类似动态压力环境下的光学窗口设计提供依据。     

相移掩模和离轴照明在ArF浸没式光刻中对工艺窗口的影响

研究了交替型相移掩模及离轴照明对65nm分辨率ArF浸没式光刻的影响,在3／4环形照明和3／4四极照明方式下,分别选用传统掩模和交替型相移掩模,研究65nm线宽的密集线条、半密集线条、孤立线条在较大的曝光系统参数范围内,对光刻工艺窗口的改善。并对在不同的照明方式、掩模结构下获得的工艺窗口进行了比较,结果表明：①在较大焦深(DOF)范围内,满足光刻性能要求可以有较大范围的曝光系统参数配置;②相时于传统照明和传统掩模,采用交替型相移掩模或者离轴照明,焦深均可提高100％-150％。     

气动效应地面模拟装置光学窗口设计与评价

气动热效应地面模拟装置是航空载荷成像性能地面检测设备的核心部分。本文设计了一种光学窗口用于气动热效应地面模拟装置,使用理论计算与模型仿真相结合的方式,严谨地阐述气动环境下光学窗口的设计理论。首先使用计算流体动力学理论(Computational Fluid Dynamics,CFD)进行仿真,计算给定条件下的气动压力和温度值,给出最严苛的条件值;然后根据经典强度理论和断裂力学理论,提出光学材料加工工艺要求,并设计窗口满足安全使用要求的厚度;最后依据流固热耦合仿真分析,验证设计的合理性,并依据导致载荷光学成像质量下降程度的变形量优化窗口的厚度。     

大视场可见光目标模拟器光学系统设计

具有特定视场的动态可见光目标模拟器是可见光成像系统测试与评估的关键设备,该模拟器的准直投影光学系统决定了基于数字微镜阵列(DMD)的动态景象投射器的性能。根据成像系统测试与评估需求,本文对可见光准直投影光学系统进行设计。基于对投影光学系统的参数计算,设计了视场58°的大视场可见光目标模拟器光学系统。将设计结果与成像光学系统进行匹配仿真,获得了良好的配合效果。通过对所研制的系统进行测试,实验结果表明所设计的光学系统完全满足模拟器的要求和对动态场景的仿真需求。     

Optimization of image-forming optics for transmission optical projection tomography

A new optical system for transmission optical projection tomography (TOPT) is presented to reduce the divergence of the projection data from the true parallel projections. This is performed by introducing an iris at the back focus of the objective lens. The influence of the defocusing on TOPT is demonstrated by computational simulations and experiments. We compare the performances of the new and conventional TOPT systems in order to optimize the optical system for three-dimensional imaging of the embryos of small animals. The optimal imaging performance is given by the new system with numerical apertures between 0.007 and 0.014, with which the spatial resolution of 25 microm is achieved. The optimal configuration is validated by TOPT of a phantom sample and a fixed five-day chick embryo.     

Image focus volume enhancement in shape from focus systems

Three-dimensional object reconstructions is an active research area in digital imaging. In shape from focus approach, erroneous focus measurements result in inaccuracy in the depth map reconstruction of 2D object. Conventionally, to enhance the image focus volume, focus values are aggregated within a window, which is a linear filtering approach. Owing to the inherent limitation of linear process, optimal results may not be obtained. In order to overcome this limitation, a non-linear filtering approach is proposed to enhance the image focus volume for accurate depth estimation. The noisy focus values are restored in two steps. First, noisy focus values are detected using min–max operators. In order to increase the dynamic range between the minimum and the maximum focus values within the window, an appropriate power law function is designed. In second step, only the noisy measurements are replaced with the estimated ones. A refined depth map is obtained from the updated focus volume. This process continues until the difference between the previous and the current depth maps becomes very small. The performance of the proposed non-linear filtering approach is obtained for various synthetic and real objects. The results highlight the depth map estimates of the proposed approach more accurate while preserving object edges. Comparative analysis demonstrates the effectiveness of the proposed approach.     

Possibility of an optical focal shift with polarization masks

The polarization phase shift (PPS) has emerged as an important analytical tool in optical metrology. The present study utilizes the concept of controlling the polarization phase in applications such as focal shift and automatic focusing. When elliptically polarized light, in general, is incident upon a circularly symmetric polarization mask consisting of circular and annular zones with each zone having a unique linear polarizability, the polarization-phase difference introduced between the polarization-masked zones is also circularly symmetric. With the mask at the lens aperture, the polarization phase introduced is multiplicative with the lens function and is shown to result in a shift of the Gaussian focus plane. Because the polarization phase can be controlled by variation of the polarization parameters, the effective focal length of the imaging system can be varied within a small range. A study of the point-spread functions at the shifted focal planes has shown that the quality of the focal patch in these planes is comparable with that produced by a diffraction-limited imaging system at Gaussian focus. The shift of focus can be achieved by control of the polarization of the input beam. It is anticipated that this technique may find application in areas for which dynamic focusing within a small range is required.     

汽车制动主缸补偿孔形位尺寸检测双远心光学系统研究

为了解决制动主缸补偿孔的成像问题,设计了一种远心内窥成像光学系统。在设计中采用工业内窥镜来延长成像系统的视距,它的后端与CCD摄像机相连接,并通过内窥镜的前后移动来捕捉补偿孔的图像信息。该系统由于将内窥镜的成像光路设计成一个像方远心光路与物方远心光路合一的光路,较好地解决制动主缸补偿孔图像因为虚焦而造成的检测误差问题,从而提高了系统的检测精度。实验结果表明,系统的测量精度达到0.01 mm。     

In vivo optical imaging and dynamic contrast methods for biomedical research

This paper provides an overview of optical imaging methods commonly applied to basic research applications. Optical imaging is well suited for non-clinical use, since it can exploit an enormous range of endogenous and exogenous forms of contrast that provide information about the structure and function of tissues ranging from single cells to entire organisms. An additional benefit of optical imaging that is often under-exploited is its ability to acquire data at high speeds; a feature that enables it to not only observe static distributions of contrast, but to probe and characterize dynamic events related to physiology, disease progression and acute interventions in real time. The benefits and limitations of in vivo optical imaging for biomedical research applications are described, followed by a perspective on future applications of optical imaging for basic research centred on a recently introduced real-time imaging technique called dynamic contrast-enhanced small animal molecular imaging (DyCE).     

Optical transfer function shaping and depth of focus by using a phase only filter

The design of a desired optical transfer function (OTF) is a common problem that has many possible applications. A well-known application for OTF design is beam shaping for incoherent illumination. However, other applications such as optical signal processing can also be addressed with this system. We design and realize an optimal phase only filter that, when attached to the imaging lens, enables an optimization (based on the minimal mean square error criterion) to a desired OTF. By combining several OTF design goal requirements, each represents a different plane along the beam propagation direction, an imaging system with an increased depth of focus is obtained. Because a phase only filter is used, high energetic efficiency is achieved.     

Highly compact imaging using Bessel beams generated by ultraminiaturized multi-micro-axicon systems

Employing Bessel beams in imaging takes advantage of their self-reconstructing properties to achieve small focal points while maintaining a large depth of focus. Bessel beams are efficiently generated using axicons, and their utility in scanning imaging systems, such as optical coherence tomography (OCT), has been demonstrated. As these systems are miniaturized to allow, for example, endoscopic implementations, micro-axicons are required to assure the maintenance of a large depth of focus. We demonstrate here the design, fabrication, and application of molded micro-axicons for use in silicon-based micro-optical benches. It is shown that arrangements of multiple convex and concave axicons may be implemented to optimize the depth of focus in a miniaturized OCT system, using a telescopic optical arrangement of considerably shorter optical system length than that achievable with classical micro-optics.     

线聚焦光学相干层析术的研究

提出了一种高速光学相干层析(OCT)成像技术方案。利用柱面镜的成像特性将传统OCT的点聚焦成像模式改变为线聚焦成像模式,从而降低二维OCT图像的扫描维数,达到提高成像速度的目的。利用ZEMAX光学软件对系统进行光线追迹获得光束经过柱面镜后的聚焦情况。随后采用635nm的激光光源和柱面镜构建了实验系统,实验结果很好地验证了光线追迹仿真结果。     

圆孔阵列对“猫眼”目标成像质量的影响分析

利用圆孔阵列光强调制作用可以有效减弱光学窗口的“猫眼”效应,同时也会对“猫眼”目标成像质量产生一定不利影响.考虑到利用调制传递函数(MTF)可对光电仪器成像质量进行综合评价,分别给出了测试望远系统和微光夜视系统MTF的数学模型,利用自行研制的光学仪器MTF数字化检测系统,实现了这两种典型“猫眼”目标MTF的数字化检测.结果表明,圆孔阵列在全空间频率上均使“猫眼”目标的MTF有所下降,且孔径较小、孔阵较密的圆孔阵列对“猫眼”目标MTF的影响较小,这为合理设计圆孔阵列结构以减小对“猫眼”目标成像质量的影响提供了可靠的实验数据.     

Design and characterization of a microchannel optical interconnect for optical backplanes

The design, modeling, and experimental characterization of a microchannel-based free-space optical interconnect is described. The microchannel interconnect was used to implement a representative portion of an optical backplane that was based on field-effect transistor, self-electro-optic device smart-pixel transceivers. Telecentric relays were used to form the optical interconnect, and two modes based on two different optical window clusterings were implemented. The optical system design, including the optical geometry for different degrees of clustering of windows supported by a lenslet relay and the image mapping associated with a free-space optical system, is described. A comparison of the optical beam properties at the device planes, including the spot size and power uniformity of the spot array, as well as the effects of clipping and misalignment for the different operating modes, is presented. In addition, the effects of beam clipping and misalignment for the different operating modes is presented. We show that microchannel free-space optical interconnects based on a window-clustering scheme significantly increase the connection density. A connection density of 2222 connections/cm(2) was achieved for this prototype system with 2 x 2 window clustering.     

Reflectance study of compressed paper

Reflectance of three paper grades was investigated using a pressure gauge, an imaging system, and a spectrophotometer. It was observed that under high pressure, dark-colored areas appear in paper when using the imaging system. The area of the dark pattern increases as the pressure is raised. Reflectance measurements as a function of wavelength confirmed that the dark patterns appear due to the contact of the paper and the probe window of the pressure gauge. Based on results by other researchers the amount and the nature of optical contact observed depends on structural properties of paper such as surface roughness, formation, and compressibility. Although there are differences in the spectral properties of different paper grades they all share the common feature that the reflectance is decreasing as a function of the applied pressure. An empiric result for the fine and the super-calendered (SC) paper samples measured is that they both have an exponential dependence of total reflectance as a function of applied pressure when the illumination wavelength is kept constant.     

High tolerance to spherical aberrations and defects of focus with a birefringent lens

We report a systematic investigation of the imaging behavior of an optical system consisting of a lens from a uniaxial birefringent crystal sandwiched between two linear polarizers into which primary spherical aberration has been introduced. The proposed system has higher tolerance to primary spherical aberration and has a larger depth of focus than an imaging system found with an isotropic lens. Some specific cases are computed and illustrated graphically.     

An Auto-Focusing Method in a Microscopic Testbed for Optical Discs

An auto-focusing method in a digital image system is demonstrated that uses a standard deviation of pixel gray levels as a feedback signal. In this system, an optical microscope and a charge coupled device (CCD) camera are used to create clear pit images of optical discs. A dynamic focusing scheme is designed in the system-control software, which is able to eliminate environmental disturbances and other noises so that a fast and stable focus can be achieved. The method shows an excellent focusing accuracy. The performance and possible applications of this method are discussed. The test results for optical discs are given in this paper.     

Optical Imaging Approaches to Monitor Static and Dynamic Cell‐on‐Chip Platforms: A Tutorial Review

Miniaturized laboratories on chip platforms play an important role in handling life sciences studies. The platforms may contain static or dynamic biological cells. Examples are a fixed medium of an organ‐on‐a‐chip and individual cells moving in a microfluidic channel, respectively. Due to feasibility of control or investigation and ethical implications of live targets, both static and dynamic cell‐on‐chip platforms promise various applications in biology. To extract necessary information from the experiments, the demand for direct monitoring is rapidly increasing. Among different microscopy methods, optical imaging is a straightforward choice. Considering light interaction with biological agents, imaging signals may be generated as a result of scattering or emission effects from a sample. Thus, optical imaging techniques could be categorized into scattering‐based and emission‐based techniques. In this review, various optical imaging approaches used in monitoring static and dynamic platforms are introduced along with their optical systems, advantages, challenges, and applications. This review may help biologists to find a suitable imaging technique for different cell‐on‐chip studies and might also be useful for the people who are going to develop optical imaging systems in life sciences studies.