Smart pixels with smart illumination

Smart pixels with smart illumination is a new concept in sensor array technology based on structured built-in illumination and optoelectronic feedback. It offers many new possibilities and potential advantages over more-traditional sensor arrays. We discuss an edge-detection system as an example of how smart illumination can advantageously be used to achieve a variety of functions. We also present initial experimental results from a fabricated chip based on this concept. The chip includes an integrated array of photodetectors and LED's. The output of each pixel can be controlled based on the feedback received by its dual detectors.     

Heat-generating property of a local plasmon resonator under illumination

We have investigated the heat generation from gold nanoparticles resulting from their local plasma resonance. We have demonstrated the self-assembly of Au nanoparticle arrays/dielectric layer/Ag mirror sandwiches, i.e., a local plasmon resonator, using a dynamic oblique deposition technique. The thicknesses of the Au and dielectric layers were changed combinatorially on a single substrate. As a result, local plasmon resonator chips were successfully fabricated. Because of strong interference, their optical absorption can be controlled between 0.0% and 97% in the near-IR region, depending on the thickness of the dielectric layer. We evaluated the heat generation from Au nanoparticles by measuring the temperature of water with which a cell prepared on a chip is filled under laser illumination. The change in the water temperature is proportional to the optical absorption of the local plasmon resonator chips. This suggests that the photothermal conversion efficiency can be controlled by interference. These features make the application of the local plasmon resonator to nanoheaters, which can spatiotemporally control heat generation, suitable.     

Wide-field high-resolution structured illumination solid immersion fluorescence microscopy

The use of aplanatic solid immersion lenses (ASILs) made of high-refractive-index optical materials provides a route to wide-field high-resolution optical microscopy. Structured illumination microscopy (SIM) can double the spatial bandwidth of a microscope to also achieve high-resolution imaging. We investigate the combination of ASILs and SIM in fluorescence microscopy, which we call structured illumination solid immersion fluorescence microscopy (SISIM), to pursue a microscopic system with very large NA and high lateral resolution. We demonstrate that the combination can produce a wide-field high-resolution microscopic system with bandwidth corresponding to an NA of 3. Future developments of the SISIM system to make it achieve even higher resolution are proposed.     

Optofluidic pressure sensor based on interferometric imaging

We present a chip-scale optofluidic interferometric sensor for measuring liquid pressure based on an imaging method. The chip was constructed with a polymer by multilayer soft lithography. It consists of a flexible air gap optical cavity, which, upon illumination by monochromatic light, generates interference patterns that depend on pressure. The pressure was measured by imaging and analyzing the interference patterns. We also employed a pattern recognition algorithm that significantly simplified the calculation and enhanced the measurement reliability. This pressure sensor was demonstrated with a working range of 0-22 psi and an accuracy of ±1.4% of full scale when temperature stabilized.     

Theoretical assessment of optical resolution enhancement and background fluorescence reduction by three-dimensional nonlinear structured illumination microscopy using stimulated emission depletion

Three-dimensional structured illumination microscopy (SIM) enlarges frequency cutoff laterally and axially by a factor of two, compared with conventional microscopy. However, its optical resolution is still fundamentally limited. It is necessary to introduce nonlinearity to enlarge frequency cutoff further. We propose three-dimensional nonlinear structured illumination microscopy based on stimulated emission depletion (STED) effect, which has a structured excitation pattern and a structured STED pattern, and both three-dimensional illumination patterns have the same lateral pitch and orientation. Theoretical analysis showed that nonlinearity induced by STED effect, which causes harmonics and contributes to enlarging frequency cutoff, depends on the phase difference between two structured illuminations and that the phase difference of π is the most efficient to increase nonlinearity. We also found that undesirable background fluorescence, which degenerates the contrast of structured pattern and limits the ability of SIM, can be reduced by our method. These results revealed that optical resolution improvement and background fluorescence reduction would be compatible. The feasibility study showed that our method will be realized with commercially available laser, having 3.5 times larger frequency cutoff compared with conventional microscopy.     

结构光照明显微中的偏振控制

结构光照明显微(structured illumination microscopy.SIM)作为一种宽场超分辨光学显微成像技术,具有成像速度快、光漂白和光毒性弱等优点,是目前主流超分辨成像方法之一.在SIM技术中,正弦强度分布的条纹结构光场的对比度决定了SIM超分辨图像的质量.低的条纹对比度将导致样品中超衍射极限的高频信息被噪声掩盖,从而无法解析出超分辨信息.结构照明入射光的偏振态调控决定了干涉条纹的对比度,是SIM的关键技术.鉴于此,本文总结对比了几种典型的SIM系统偏振控制方法,同时提出了一种使用零级涡旋半波片的偏振控制方法.实验证明,与其他方法相比,采用零级涡旋半波片法可以获得更高效的偏振控制效果,具有系统结构简单、易使用、可将光能利用率提升到接近100%的优点.     

CMOS传感器感光范围测定系统及其可编程接口的实现

介绍了一种实用的CMOS传感器感光范围测定系统。利用积分球作标准光源,并用逻辑分析仪作数字输出信号的分析统计,测出CMOS传感器光照度接收曲线。在此基础上提出了一种基于可编程接口(FPGA)芯片控制的CMOS传感器自动调光技术。利用FPGA控制CMOS传感器的电子快门,以此来控制其光照度,达到自动调光的目的。由于FPGA是在线可编程器件,具有电路简单,实时性好,适应性强等特点,并能与后期的图像处理有机结合,所以简化了整个系统的设计。     

Axial coding in full-field microscopy using three-dimensional structured illumination implemented with no moving parts

We report a simple optical setup to produce both axial and lateral structured illumination through a single objective lens. With a minimum of six full-field images obtained without moving either the sample or the microscope objective, 100 nm diameter fluorescent beads can be localized axially with an accuracy of 50 nm in a 1.76-microm-thick layer. We show that this axial localization improvement can easily be combined with classical lateral structured illumination, so that lateral resolution enhancement by a factor of 2 is maintained.     

基于相移结构光照明的浮雕成像技术研究

详细介绍了一种基于相移结构光照明的浮雕成像技术,对该成像技术的原理和成像特性进行了实验研究,并采用相移结构光照明的方法实现彩色浮雕成像。实验中,将多幅相移正弦条纹光场斜投射到被拍摄物体上,数码相机依次拍摄被照明的物体,再利用拍摄到的多幅相移图像,通过计算的方法重建出所需要的图像。理论分析和实验结果表明,相移结构光照明成像技术能有效地消去环境不均匀光照的影响,获取的反射率分布图像只与结构光照明有关,突显了斜投射照明所形成的阴影,图像的明暗变化反映出物体表面的法线变化,因而在视觉上形成了明显的浮雕效果。     

数字微镜器件的时空特性对相位测量轮廓术的影响

数字微镜器件是一种新型的微电子、微机械、微光学集成器件,可广泛的用于大屏幕投影显示。实际上,数字微镜器件作为一种新型的空间光调制器,在光学信息处理和结构照明型三维传感中也具有广泛的应用前景。介绍了数字微镜器件和数字光处理器的基本原理,分析了数字微镜器件的时间空间特性,用计算机模拟了这种时空特性对相位测量轮廓术的影响。结果表明,数字微镜器件(DMD)可为投影系统在结构照明型光学三维传感中的应用提供指导。     

硅衬底垂直结构InGaAlN多量子阱发光二极管电致发光谱的干涉现象研究

测试了硅衬底垂直结构芯片在不同空间角度上的电致发光(EL)谱.指出硅衬底垂直结构InGaAlN多量子阱发光二极管的EL谱中多个峰型来源于干涉现象,而不是来自于多个阱层的发光.干涉峰的疏密反映p型层厚度的一致性,干涉现象的强弱反映p型欧姆接触层反光能力的强弱.芯片法线方向附近发光最强干涉现象最明显,芯片侧边的发光几乎没有干涉现象且发光强度最弱. 关键词： InGaAlN 发光二极管 垂直结构 电致发光     

基于束间动态干涉的快速匀滑新方法

针对高功率激光装置中靶面辐照均匀性的高要求,提出了一种利用束间动态干涉改善辐照均匀性的快速匀滑方法.基本原理是利用共轭相位板阵列对存在一定波长差的多束激光附加相位调制,从而使各子束在远场两两相干叠加以产生动态的干涉图样,进而引起焦斑内部散斑的动态扫动,在ps时间内抹平不均匀性.以典型惯性约束聚变装置中的激光集束为例,通过建立基于束间动态干涉的快速匀滑物理模型,定量分析了相位板类型、相位调制幅度和束间波长差等因素对焦斑动态干涉图样的影响及规律,进而对其束匀滑特性进行了讨论.结果表明,基于束间动态干涉的快速匀滑方法可以有效地实现多方向、多维度的焦斑内部散斑快速扫动,且通过与传统束匀滑技术的联用,可以在更短的时间内达到更好的焦斑均匀性.     

Adaptation of video moiré techniques to undersea mapping and surface shape determination

Fixed and variable resolution video moiré techniques have been used to project structured illumination in a model undersea environment and a prototype system has been developed which generates equal depth contours of undersea objects and has applications in sizing, orientation and ranging. An advantage of this system is that the entire field is continously illuminated, and the moiré contours and images are formed at video rates. The spatial frequency of the structured illumination can be continously varied, providing optimal contours for a variety of object sizes. The data can be easily interpreted by eye or processed by computer to obtain surface shape, range and orientation of a known structure.     

Performance study of microwave photonic phase shifter based on vector-sum technique

An integrated microwave photonic phase shifter based on vector-sum technique in silicon on insulator was verified and designed. The principle of phase-shift was demonstrated and the components were designed in detail. The interference was taken into account in the design and 0.3 nm line-width of a light source was required to make the coherent interference smallest even to be neglected. Owing to the compact size and excellent characteristics of integration, the proposed component has a promising utilization in optical communication and optical phased-array radar.     

基于LED的便携式近红外整粒小麦成分测量仪的研制

采用最新集成芯片和软件设计 ,研制出以近红外LED为光源的整粒小麦成分快速分析的仪器 ,为小麦成分的现场检测提供了一个经济、快捷的便携式设备。该测量仪由近红外LED光源、窄带干涉滤光片、菲涅尔透镜、硅光电池检测器、单片机系统及校准模型等组成。与其他近红外仪器相比 ,该测量仪具有体积小、结构简单、低功耗、抗震动等特点。同时介绍了该测量仪的硬件设计 ,软件设计 ,对小麦蛋白质的建模和预测应用实例等。该测量仪可在粮库甚至田间现场对整粒小麦成分进行无损检测     

A compact lensless and slitless volume holographic spectrometer for diffuse source spectroscopy

We present a simple, very compact, and inexpensive spectrometer for diffuse source spectroscopy using only a volume hologram (recorded by two spherical beams) and a CCD camera (or a detector array). We show that this spectrometer can operate well under spatially incoherent light illumination. We also show that the resolution of this spectrometer can be optimized by proper selection of the location of the CCD camera (or the detector array). The results show the possibility of using optimized holographic optical elements as the integrated collimating, dispersive, and light-collective components of spectrometers. PACS 42.40.Pa; 42.79.-e     

Resolution improvement for enhancing interference fringes of digital holograms with near infrared illuminance

A new resolution improving method of enhancing the interference stripes, which can achieve better reconstruction of the recorded object of infrared digital holography has been proposed in this paper. The experiment is conducted under near infrared illuminance. We create poor quality holograms with very low-resolution interference stripes and enhance it with our new method. The processed holograms have much higher-resolution interference stripes. This method is based on interpolation theory, and we make it works fast, stable and easy to apply. Both the forward and backward interpolation of the oriental and portrait direction of the source pixels have been calculated, and have been used to realize the final aim of resolution improvement. During the experiment, since the responsivity of the CCD is not satisfied with the illuminance laser, which is by design, we also give specific analysis on the experimental setup of our work to make sure the object information can be fully recorded by the optical setup but cannot be reconstructed because of the low-resolution and unobvious of the interference stripes. After the resolution improvement process of the original hologram, the object information can then be fully reconstructed, which is very clear in the paper. Figures and dataflow give evidence and demonstrate the good performance of our method.     

Highly Efficient Excitation of Surface Plasmons Using a Si Gable Tip

A compact and highly efficient technique to excite SPP mode at an Au/SiO₂ interface by using an engineered high index (silicon) gabled tip at the 1550 nm wavelength has been proposed. The optimized geometry of the Si tip enables a highly efficient excitation of the single interface SPP mode through near field interaction in an ultra‐compact setup. An experimental demonstration of the proposed scheme is also presented in the paper which converts 25.5% of the total input power to an SPP mode. With an improved fabrication, this efficiency can reach as high as 52%. The device is compact, facilitates on‐chip excitation of the SPP, its fabrication is compatible with the standard Si fabrication processes, and, as such it is expected to be very useful in the design of future integrated photonic circuits as well as integrated sensors. Also, this scheme can find applications in studying nonlinear characteristics of materials.     

实现均匀照明的自由曲面反射器

通过单个自由曲面反射器的反射,令光源发出的能量重新分布,在特定照明面上实现所需照明,从而简化了投影设备中的照明系统,使设备的进一步小型化成为可能。根据给出的光源辐射特性和所需实现的照明面上的能量分布,可得到一组偏微分方程,数值差分求解直接得到自由曲面反射器。光源采用发光面积1 mm×1 mm朗伯体发光的LED,视角为120°,照明面为4:3的均匀矩形光斑。设计了两种自由曲面反射器,并用软件对得到的曲面进行了照明模拟,模拟得到的照明均匀性接近90%。两种反射器在光轴方向上的投影尺寸均小于25 mm,垂直光轴方向上投影长度均小于22 mm,照明系统总长均小于40 mm,结构紧凑,适用于小型LED投影设备。     

A compact ESPI system for displacement measurements of specular reflecting or optical rough surfaces

A stable and compact speckle interferometer for doing out-of-plane displacement measurements on reflective as well as diffusely scattering object surfaces is demonstrated. The set-up is based on a nearly path length compensated interferometer of the Fizeau type and uses diffuse illumination of the object combined with a speckled reference wave. This combination eliminates the need for special optical components, and the interferometer can be built of commonly available components. The diffuse illumination wave is obtained by scattering coherent light from a diffusely scattering surface. The speckled reference wave is established by reflecting a part of the diffuse illumination wave from a glass plate placed in front of the object. Besides relaxing the alignment tolerances of the set-up, the diffuse illumination eliminates the need for any preparation of the surface under test, which turns the system into a candidate for testing micro mechanical systems. When using the interferometer for measurements of the eye, the risk of focusing the laser beam on the retina is decreased due to the diffuse object illumination.