线照明并行谱域光学相干层析成像系统与缺陷检测应用研究

针对玻璃缺陷在线无损检测的迫切需求,本文报道了一种基于线照明并行谱域光学相干层析成像系统的大视场检测系统.该系统采用快速面阵CMOS相机,单次拍摄即可获取完整的横截面(B-scan)图像.基于线照明面阵探测器的并行谱域光学相干层析成像系统,可以同时获取沿线照明方向各位置处的深度分辨信息,避免了横向扫描机构的应用.研制系统的轴向分辨率为17.9μm,并行方向上的横向分辨率55.7μm,扫描方向上的横向分辨率为24.8μm,轴向扫描速率为128 000 A-scan/s,横向视场为32 mm,空气中成像深度大于6 mm,成像灵敏度达到62 dB以上.利用研制的线照明并行谱域光学相干层析成像系统,开展了不同类型玻璃表面及其内部缺陷的检测应用研究.     

超高分辨光学相干层析成像技术与材料检测应用

本文报道了一种超高分辨率谱域光学相干层析成像(SD-OCT)系统. 该系统基于超连续谱激光光源并截取部分光谱作为宽带光源, 其中心波长为665 nm, 光谱半高全宽(FWHM) 230 nm. 系统轴向分辨率0.9 μm, 轴向扫描速率28600行/秒, 横向分辨率3.9 μm, 横向视场1 mm, 最大成像深度0.6 mm(空气中). 利用研制的超高分辨率SD-OCT系统, 对不同型号的工业砂纸精细结构进行了成像, 并与普通SD-OCT的成像结果进行对比, 充分展示了研制系统在材料无损检测中优势.     

Ultrahigh-resolution full-field optical coherence tomography using spatial coherence gating and quasi-monochromatic illumination

We developed an ultrahigh-resolution full-field optical coherence tomography (FF-OCT) microscope that is based on the spatial, rather than the temporal, coherence gating. The microscope is capable of observing three-dimensional microbiological structures as small as 0.4 μm × 0.4 μm × 1.0 μm (xyz) using quasi-monochromatic light and a liquid crystal retarder. Unlike traditional FF-OCT systems, this microscope can be operated in high resolution for any preferable wavelength with minimized defocusing and dispersion effects. High-resolution images of an onion cell are presented.     

Parallel optical coherence tomography using a CCD camera

Parallel optical coherence tomography is demonstrated using a 12-bit scientific-grade charge-coupled device array.A superluminescent diode in combination with a free-space Michelson interferometer was employed to achieve 10-μm axial resolution and 1.1-μm transverse resolution on a 902×575 μm2 field of view.We imaged a test mirror and bovine retinal tissue using a four-step phase shift method.     

光学成像在疾病诊断中的应用

当前，医生们利用各种成像技术与疾病进行斗争，其中光学成像技术是获得高分辨率图像的新方法，其原理是每种生物介质具有各自特有的光谱特性，可赖以区分病变组织和正常组织，或对潜在问题准确定位。而光学相干层析则是最精确的光学成像技术，可提供１０～２０μｍ量级的高分辨率及比迄今为止任何其他技术都高的灵敏度。本文着重讨论光学相干层析术的基本原理及目前发展状况     

基于最优化线性波数光谱仪的谱域光学相干层析成像系统

相比传统光谱仪,基于线性波数光谱仪的谱域光学相干层析(OCT)无需对非线性波数干涉光谱数据进行重采样和插值,可大大减少数据计算量并提高成像灵敏度.通过模拟计算干涉光谱信号和点扩散函数,以点扩散函数半峰全宽值的倒数作为评价准则,可以优化包括色散棱镜材料的折射率、顶角角度以及衍射光栅和色散棱镜之间旋转角角度的线性波数光谱仪的结构参数.根据优化结果,实验中选用F2玻璃等边色散棱镜,以光栅-棱镜间旋转角角度为21.8°搭建了最优化线性波数光谱仪,并引入谱域OCT成像系统.实验测得成像系统的轴向分辨率达到8.52μm,灵敏度达到91 dB,6 dB成像深度达到1.2 mm.结合具有通用并行计算能力的图形处理卡,在无需重采样和插值的情况下可实时处理和显示人手指指甲皮肤接缝处的横断面OCT图像,验证了基于最优化线性波数光谱仪的谱域OCT系统的成像性能.     

Human cervical carcinoma detection and glucose monitoring in blood micro vasculatures with swept source OCT

We report a pilot method, i.e., speckle variance (SV) and structured optical coherence tomography to visualize normal and malignant blood microvasculature in three and two dimensions and to monitor the glucose levels in blood by analyzing the Brownian motion of the red blood cells. The technique was applied on nude live mouse’s skin and the obtained images depict the enhanced intravasculature network forum up to the depth of ～2 mm with axial resolution of ～8 μm. Microscopic images have also been obtained for both types of blood vessels to observe the tumor spatially. Our SV-OCT methodologies and results give satisfactory techniques in real time imaging and can potentially be applied during therapeutic techniques such as photodynamic therapy as well as to quantify the higher glucose levels injected intravenously to animal by determining the translation diffusion coefficient.     

Basic Study on Imaging Interferometer using Long Gradient-Index Lenses for Optical Coherence Tomography

An imaging interferometer with two long gradient-index (GRIN) lenses and a charge coupled device (CCD) sensor array is proposed and studied for application to an optical coherence tomography system that can observe the subsurface structure of internal organs through a small hole in the body. An image of lines 11 μm wide was obtained using the phase-shifting method and a test pattern as a sample. The lateral resolution obtained was 22 μm. The axial resolution was also measured and found to be 19.4 μm by measuring the coherence function. The dynamic range was about 60 dB, based on the RF spectrum of the beat signal. A sectional image of a 10-yen Japanese coin was measured as a rough surface sample.     

Holoscopy--holographic optical coherence tomography

Scanning optical coherence tomography (OCT) is limited in sensitivity and resolution by the restricted focal depth of the confocal detection scheme. Holoscopy, a combination of holography and Fourier-domain full-field OCT, is proposed as a way to detect photons from all depths of a sample volume simultaneously with uniform sensitivity and lateral resolution, even at high NAs. By using the scalar diffraction theory, as frequently applied in digital holographic imaging, we fully reconstruct the object field with depth-invariant imaging quality. In vivo imaging of human skin is demonstrated with an image quality comparable to conventionally scanned OCT.     

突破分辨率极限的拉曼光谱学——简介近场光学与近场拉曼光谱

突破分辨率极限的拉曼光谱学——简介近场光学与近场拉曼光谱张树霖（北京大学物理系北京１００８７１）ＴｈｅＲａｍａｎＳｐｅｃｔｒｏｓｃｏｐｙＢｒｏｋｅｎｔｈｅＤｉｆｒａｃｔｉｏｎＬｉｍｉｔａｔｉｏｎ——Ｉｎｔｒｏｄｕｃｔｉｏｎｔｏｔｈｅｎｅａｒ－ｆｉｅｌ...     

双光栅快速扫描光学延迟线的色散补偿

光学相干层析成像(OCT)系统的纵向分辨力不仅与光源的带宽有关,而且与系统中两干涉臂间的色散匹配有关。如果色散没有得到精确匹配,将使光学相干层析成像系统的纵向分辨力达不到所预期的理论值。色散问题在超高分辨光学相干层析成像系统中尤为突出。提出了一种基于双光栅快速扫描光学延迟线(RSOD),用于光学相干层析成像系统的色散补偿。该方法中新增的光栅引入了光栅间距这一独立变量,其与常规单光栅快速扫描光学延迟线机构中的光栅离焦量一起,可使光学相干层析成像系统中的群速度色散(GVD)和三阶色散(TOD)同时得到补偿。分析了双光栅快速扫描光学延迟线的色散特性和色散调节原则,并提供了一个典型光学相干层析成像系统中的色散补偿实例。     

High-resolution optical coherence tomography over a large depth range with an axicon lens

In optical coherence tomography, axial and lateral resolutions are determined by the source coherence length and the numerical aperture of the sampling lens, respectively. Whereas axial resolution can be improved by use of a broadband light source, there is a trade-off between lateral resolution and focusing depth when conventional optical elements are used. We report on the incorporation of an axicon lens into the sample arm of an interferometer to overcome this limitation. Using an axicon lens with a top angle of 160 degrees , we maintained 10-microm or better lateral resolution over a focusing depth of at least 6 mm. In addition to having high lateral resolution, the focusing spot has an intensity that is approximately constant over a greater depth range than when a conventional lens is used.     

In vivo imaging of intrinsic optical signals in chicken retina with functional optical coherence tomography

Visually evoked intrinsic optical signals (IOSs) were measured in vivo for the first time to our knowledge from all retina layers of the chicken retina with a combined functional optical coherence tomography and electroretinography (ERG) system. IOS traces were recorded from a small volume in the retina with 3.5 μm axial resolution and 7 ms time resolution. Comparison of the IOS and ERG traces shows a correlation between the positive and negative IOS measured from different retinal layers and the timing of the a and b waves in the ERG recording.     

Fiber-optic Fourier-domain common-path OCT

We experimentally and theoretically investigated the performance of a fiber-optic based Fourier-domain common-path optical coherence tomography （OCT）. The fiber-optic common-path OCT operated at the 840-nm center wavelength. The resolution of the system was 8.8 μm （in air） and the working depth using a bare fiber probe was approximately 1.5 mm. The signal-to-noise ratio （SNR） of the system was analyzed. OCT images obtained by the system were also presented.     

Real-time four-dimensional optical-resolution photoacoustic microscopy with Au nanoparticle-assisted subdiffraction-limit resolution

Photoacoustic microscopy (PAM) offers label-free, optical absorption contrast. A high-speed, high-resolution PAM system in an inverted microscope configuration with a laser pulse repetition rate of 100,000 Hz and a stationary ultrasonic transducer was built. Four-dimensional in vivo imaging of microcirculation in mouse skin was achieved at 18 three-dimensional volumes per second with repeated two-dimensional (2D) raster scans of 100 by 50 points. The corresponding 2D B-scan (50 A-lines) frame rate was 1800 Hz, and the one-dimensional A-scan rate was 90,000 Hz. The lateral resolution is 0.23 ± 0.03 μm for Au nanowire imaging, which is 2.0 times below the diffraction limit.     

激光超衍射加工机理与研究进展

随着纳米科技和微纳电子器件的发展,制造业对微纳加工技术的要求越来越高.激光加工技术是一种绿色先进制造技术,具有巨大的发展潜力,己广泛应用于不同的制造领域.为实现低成本、高效率、大面积尤其是高精度的激光微纳加工制造,研究和发展激光超衍射加工技术具有十分重要的科学意义和应用价值.本文首先阐述了基于非线性效应的远场激光直写超衍射加工技术的原理与国内外发展状况,包括激光烧蚀加工技术、激光诱导改性加工技术和多光子光聚合加工技术等;然后介绍了几种基于倏逝波的近场激光超衍射加工技术,包括扫描近场光刻技术、表面等离子激元光刻技术等新型超衍射激光近场光刻技术的机理与研究进展;最后对激光超衍射加工中存在的问题及未来发展方向进行了讨论.     

Ultra-High Resolution Optical Coherence Tomography (OCT) Using a Halogen Lamp as the Light Source

The axial resolution of optical coherence tomography (OCT) is determined by the coherence length of the light source. We demonstrate for the first time high-resolution OCT of biological tissue using a halogen lamp as the light source for a low coherence interferometer. High-resolution OCT imaging with 3.5 μm resolution was performed successfully for onion and porcine skin, although the coherence light power for illumination of a sample is as small as 100 nW.     

用表面等离子体共振传感器检测纳米间距

结合物理光学原理和表面等离子体共振（SPR）角度传感器,提出了可以突破衍射极限的纳米间距检测方法。在理论上建立起纳米间距和位相改变量之间的函数关系,借助于SPR角度传感器的高灵敏性,提出通过检测出射光束振动方向的p分量和s分量的位相差值来实现纳米间距的实时检测。模拟结果显示：纳米间距改变量从-0.5～0.5μm变化时,位相改变量可实现-150°～150°的变化,检测灵敏度〉1 nm。该检测方法能够实现10 nm以下间距的灵敏检测,且具有结构简单,易于操作,实时检测的特点。     

In-focus Fourier-domain Optical Coherence Tomography by Complex Numerical Method

We introduce a numerical in-focus Fourier-domain optical coherence tomography(in-focus FD-OCT) which can measure cross-sectional images of samples with the high lateral resolution comparable with the resolution in the focal plane in overall range of measurement. In this method, the lateral resolution is enhanced by lateral signal processing of a complex OCT image obtained with FD-OCT. Quantitative evaluation of this method and application to measurement of a porcine eyeball are presented.     

用于光电仪器和相关测量的自混合干涉技术（特邀）

回顾了一种全新结构的干涉仪—自混合干涉仪（SMI）的发展情况。SMI由于其在激光器外部无需任何光学元件且应用范围广泛而倍受关注。SMI可用于测量与光路长度有关的一些量（如位移、小幅度振动、速度）,也可用于测量弱光的回波（即回波损耗和隔离因子的测量）并可表征与介质相互作用特性相关的物理参数（如激光线宽、相干长度以及α因子等）。SMI是一种相干探测方法,其工作在靠近接收场的量子极限处,目前对散射目标物的最小探测幅值可达槡20 pm/（Hz）～（1/2）甚至更高,使用角锥棱镜使其计数步长为半波长,在动态范围为2 m时其分辨率约为0.5μm。另外,SMI结构紧凑、易于现场安装且可用于MEMS测试、旋转机械振动测试和生物运行测试等各种实验。