Imaging biological specimens with the confocal scanning laser microscope/macroscope

A new confocal scanning laser microscope/macroscope (cslm/M) has recently been developed. It combines in one instrument the high resolution capability of a confocal scanning beam microscope for imaging small specimens, with good resolution confocal imaging of macroscopic specimens. Some of its main features include: (a) 0.25 μm lateral resolution in the microscope mode and 5 μm lateral resolution in the macroscope mode; (b) a field of view that can vary from 25 μm × 25 μm to 75,000 μm × 75,000 μm; (c) capability for acquiring large data sets from 512 × 512 pixels to 2048 × 2048 pixels; (d) 0.5 μm depth resolution in the microscope mode and 200 μm depth resolution in the macroscope mode.

In this work the cslm/M was used to image whole biological specimens (> 5 m diameter), including insects which are ideal specimens for the macroscope. Specimens require no preparation, unlike scanning electron microscope (SEM) specimens which require a conductive coating. The specimens described in this paper are too large to be imaged in their entirety by a scanning beam laser microscope, however they can be imaged by slower scanning stage microscopes. In the macroscope mode the cslm/M was used to acquire a large number (e.g. 20–40) of confocal image slices which were then used to reconstruct a three-dimensional image of the specimen. High resolution images were collected by the cslm/M by switching to the microscope mode where high numerical aperture (NA) objectives were used to image a small area of interest. Reflected-light and fluorescence images of plant and insect specimens are presented which demonstrate the morphological details obtained in various imaging modes. A process for three-dimensional visualization of the data is described and images are shown.     

CMOS monolithic pixel sensors research and development at LBNL

This paper summarizes the recent progress in the design and characterization of CMOS pixel sensors at LBNL. Results of lab tests, beam tests and radiation hardness tests carried out at LBNL on a test structure with pixels of various sizes are reported. The first results of the characterization of back-thinned CMOS pixel sensors are also reported, and future plans and activities are discussed.      

THALES long wave QWIP thermal imagers

THALES have developed for volume manufacture high performance low cost thermal imaging cameras based on the THALES Research Technology (TRT) third generation gallium arsenide long wave QWIP array. Catherine XP provides 768 × 575 CCIR video resolution and Catherine MP provides 1280 × 1024 SXGA video resolution. These compact and rugged cameras provide 24 h passive observation, detection, recognition, identification (DRI) in the 8–12 μm range, providing resistance to battlefield obscurants and solar dazzle, and are fully self contained with standard power and communication interfaces. The cameras have expansion capabilities to extend functionality (for example, automatic target detection) and have network battlefield capability. Both cameras benefit from the high quantum efficiency and freedom from low frequency noise of the TRT QWIP, allowing operation at 75 K, low integration times and non interruptive non uniformity correction. The cameras have successfully reached technology readiness level 6/7 and have commenced environmental qualification testing in order to complete the development programmes. These latest additions to the THALES Catherine family provide high performance thermal imaging at an affordable cost.     

Towards dualband megapixel QWIP focal plane arrays

Mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) 1024 × 1024 pixel quantum well infrared photodetector (QWIP) focal planes have been demonstrated with excellent imaging performance. The MWIR QWIP detector array has demonstrated a noise equivalent differential temperature (NEΔT) of 17 mK at a 95 K operating temperature with f/2.5 optics at 300 K background and the LWIR detector array has demonstrated a NEΔT of 13 mK at a 70 K operating temperature with the same optical and background conditions as the MWIR detector array after the subtraction of system noise. Both MWIR and LWIR focal planes have shown background limited performance (BLIP) at 90 K and 70 K operating temperatures respectively, with similar optical and background conditions. In addition, we have demonstrated MWIR and LWIR pixel co-registered simultaneously readable dualband QWIP focal plane arrays. In this paper, we will discuss the performance in terms of quantum efficiency, NEΔT, uniformity, operability, and modulation transfer functions of the 1024 × 1024 pixel arrays and the progress of dualband QWIP focal plane array development work.     

Design, characterization and evaluation of high performance 2.8 μm pitch zero space microlens

Utilization of the zero space microlens technology can significantly improve the image quality of CMOS sensors. In this study, we present systematical data of design, simulation, characterization and silicon level testing during the initial stage of development of the zero space microlens based CMOS imaging technology. The optimal structure of zero space microlens was obtained based on the simulation results. Sample CMOS image sensors with a 2.8 μm pitch zero space microlens above each pixel have been successfully fabricated based on 0.18 μm CMOS technology. Using AFM (atomic force microscopy) and sensor test platform, the structural and optical properties of both space microlens and zero space microlens have been characterized, and their performances have been evaluated respectively. Both AFM results and silicon tests have demonstrated that the 2.8 μm pitch zero space microlens can remarkably improve the pixel sensitivity and pixel array non-uniformity, and reduce the optical crosstalk. Compared to the space 2.8 μm square microlens, the zero space microlens shows 78.83% (68.42% and 75.93%) enhancement of photosensitivity and increment of pixel non-uniformity up to 20% (45.6% and 30.77%) for R (G and B), and reduction of the optical crosstalk up to 44.49%, under 45 lux light and 30 ms exposure time. In addition, the zero space microlens has also shown a great potential in further reducing pixel size down to less than 2.8 μm and meanwhile improving imaging performance of CMOS image sensors.     

两种高速CMOS图像传感器的应用与测试

采用MI-MV13和LUPA-1300-2两种不同厂家型号的高速CMOS图像传感器,设计了分辨率为1 280×1 024的300～500 frame/s高速数字工业相机,并在实验室条件下对设计相机进行了关键性能指标对比测试,得到了光谱响应及量子效率、增益、动态范围、暗电流、读出噪声、光电响应非均匀性等测试结果。测试分析显示,LUPA-1300-2的峰值量子效率为50%,比MI-MV13的峰值量子效率高12%,与厂家的参考指标基本一致。测试结果证明：该测试方法正确,对两种高速CMOS图像传感器的关键性能指标的测试客观可信,所设计的高速CMOS摄像机的性能基本满足高帧频摄像的要求。     

Optical characterization methods for solid-state image sensors

The accurate measurement of the optoelectronic properties of imaging sensors is of utmost importance for their appropriate use in various modern application fields, such as in metrology, quality control, environmental monitoring, medicine or for automotive applications. Key sensor parameters include spatial resolution, uniformity, sensitivity, linearity, signal to noise ratio and dynamic range. Today high-end optical systems mostly rely on charge coupled device (CCD) image sensors. Continuous progresses in CMOS submicron technology and the advent of ‘active pixel sensor’ (APS) imagers have however led to a wealth of novel line and area array imaging devices with added functionalities (eg. on-chip control and read-out electronics) or performance optimized for specific tasks (eg. a dynamic range in excess of 120 dB). The optimal use of CMOS image sensing technology nevertheless depends strongly on the absolute and accurate optoelectronic characterization of these devices. Modern measurement techniques for a reliable, traceable, precise and absolute measurement of the most relevant parameters of CCD and CMOS imaging sensors are described and discussed in the present paper, with examples based on recent state-of-the art CMOS imagers.     

Optical fiber sensor-based detection of partial discharges in power transformers

In this paper, a fiber optic acoustic sensor system is designed and tested for on-line detection of the partial discharges inside high voltage power transformers. The fiber optic sensor uses a silica diaphragm and a single mode optical fiber encapsulated in a silica glass tube to form an extrinsic Fabry–Perot interferometer. Test results indicate that the developed fiber optic sensors are capable of detecting the acoustic signals propagating inside the transformer oil with high resolution and high frequency.     

Image processing pipeline for synchrotron‐radiation‐based tomographic microscopy

With synchrotron‐radiation‐based tomographic microscopy, three‐dimensional structures down to the micrometer level can be visualized. Tomographic data sets typically consist of 1000 to 1500 projections of 1024 × 1024 to 2048 × 2048 pixels and are acquired in 5–15 min. A processing pipeline has been developed to handle this large amount of data efficiently and to reconstruct the tomographic volume within a few minutes after the end of a scan. Just a few seconds after the raw data have been acquired, a selection of reconstructed slices is accessible through a web interface for preview and to fine tune the reconstruction parameters. The same interface allows initiation and control of the reconstruction process on the computer cluster. By integrating all programs and tools, required for tomographic reconstruction into the pipeline, the necessary user interaction is reduced to a minimum. The modularity of the pipeline allows functionality for new scan protocols to be added, such as an extended field of view, or new physical signals such as phase‐contrast or dark‐field imaging etc.     

A planar lightwave circuit based micro interrogator and its applications to the interrogation of multiplexed optical fiber Bragg grating sensors

Optical fiber Bragg grating sensors have found potential applications in many fields, but the lack of a simple, field deployable and low cost interrogation system is hindering their deployment. To tackle this, we have developed a micro optical sensor interrogator using a monolithically integrated planar lightwave circuit based echelle diffractive grating demultiplexer and a detector array. The design and development of this device are presented in this paper. It has been found that the measurement range of this micro interrogator is more than 25 nm with better than 1 pm resolution. This paper also reports the applications of the micro interrogator developed to the monitoring of commercial optical fiber Bragg grating (FBG) temperature sensors and mechanical sensors. The results obtained are very satisfactory and in some cases, they are better than those obtained using commercial bench top lab equipment.     

An STM investigation of the Cu(110)−c(6 × 2)O system

The formation of the c(6 × 2)−O phase on a Cu(110) surface, after completion of the (2 × 1)−O structure, was observed by scanning tunneling microscopy (STM). The phase is composed of isotropic structural elements on fourfold hollow sites of the substrate lattice, which form a quasi-hexagonal array and manifest themselves as large protrusions in the STM images. Individual units of this type are mobile and also represent stable nuclei within a (2 × 1) surrounding. Nucleation is activated and occurs preferentially at steps, in contrast to previous findings with the (2 × 1) phase. Structural implications of additional weak features in high resolution images and of the observed change in two-dimensional density of Cu atoms are discussed.     

An STM study of the adsorption of Pb on Cu(100): formation of an ordered surface alloy

The adsorption of Pb on Cu(100) from 0 to 1 ML was investigated by UHV scanning tunneling microscopy. We obtained atomic resolution images of the different superstructures which appear at 300 K with increasing coverage (c(4 × 4), c(2 × 2) and c( √2)R45°). We confirm recent results and propose, partly on the basis of low temperature studies, new arguments in favour of an incorporation of lead atoms in the surface layer of copper for low coverage. We demonstrate that the c(4 × 4) superstructure corresponds to an ordered surface alloy of Pb₃Cu₄ composition, by investigating separately the alloying and de-alloying transitions. De-alloying occurs during the first-order transition between the c(4 × 4) and c(2 × 2) superstructures.     

Microwave Photonics for High-Resolution and High-Speed Interrogation of Fiber Bragg Grating Sensors

Abstract

Conventional fiber Bragg grating sensors have a few limitations, such as limited interrogation resolution and speed and difficulty in separating different measurands. In this article, microwave photonic techniques applied to fiber Bragg grating sensors to improve the interrogation resolution and speed are discussed. Experimental results to validate the techniques are provided.     

Surface plasmon resonance interferometer for bio- and chemical-sensors

An interferometric method for the detection of the phase shifts of reflected light under Surface Plasmon Resonance (SPR) conditions due to refractive index changes is proposed and experimentally realized. The sensitivity threshold of the method to a refractive index variation Δn is estimated to be 4×10⁻⁸. The proposed SPR-interferometer provides spatial phase resolution and thus enables to take into account the peculiarities of refractive index distribution over the surface of an SPR-supporting film. It can be successfully applied in bio- and chemical-sensor systems.     

一种折反式大视场强焦比平场CCD照相机

介绍了折反式大视场强焦比平场CCD照相机的设计思想和方法,给出了详细的结构参数和像斑弥散直径。照相机焦比0.9,对角视场22.2°,使用波长范围390～900nm,以660nm为分界波长分为红蓝两区照相机,各用一块1024×2048CCD接收器。照相机像质优良,结构全新。     

小孔阵列式太阳敏感器的光学系统设计

微型数字式太阳敏感器光学系统由APS CMOS图像传感器和基于MEMS工艺的小孔阵列式光线引入器组成。图像传感器的分辨率为1024×1024pixel,像素尺寸为10μm×10μm;光线引入器具有微小孔阵列结构,小孔为方形孔,30×30阵列,尺寸为60μm×60μm,间距为250μm。光线引入器采用了MEMS工艺的掩模板制备工艺。针对所设计的光学系统计算了曝光时间,并在此基础上进行了地面成像实验。实验结果表明,光学系统设计合理,保证了敏感器所具有的高精度和大视场。     

Surface reconstructions and phase transitions on the GaAs(111)B surface

The (111)B surface of GaAs has been investigated using scanning tunneling microscopy (STM) and a number of different reconstructions have been found at different surface stoichiometries. In accordance with electron diffraction studies, we find the series (2 × 2), (1 × 1)_LT, ( ) and (1 × 1)_HT with increasing annealing temperature, corresponding to decreasing surface As concentration. The (1 × 1)_LT is of particular interest, since it only occurs in a narrow temperature window between the two more established reconstructions, the (2 × 2) and the ( ). We find the (1 × 1)_LT to take the form of a mixture of the local structures of both the (2 × 2) and ( ) phases, rather than having a distinct structure. This is behaviour consistent with a kinetically limited system, dominated by the supply of As adatoms to the surface, and may be an example of a continuous phase transition. Above the (1 × 1)_LT transition, atomic resolution images of the ( ) surface reveal only a three-fold symmetry of the hexagonal structural units, brought about by inequivalent surface bonding due to the 23.4° rotation of the surface unit cell relative to the substrate. This is responsible for the disorder found in the ( ) reconstruction, since the structure may form in one of two domains. At lower surface As concentration, the (1 × 1)_HT surface adopts a structure combining small domains of a 19.1° structure and random disorder. There is no apparent similarity between the (1 × 1)_LT and (1 × 1)_HT structures, which may be due to our measurements being conducted at room temperature and without an As flux to control the surface As concentration.     

New developments of the R&;D silicon tracking for linear collider on silicon trackers

The status of the R&D activity achieved so far within the SiLC (silicon tracking for the linear collider) collaboration is reported here. It includes the following items: present status of the collaboration, new developments on sensors, on mechanics (new directions for module construction, large support structure, cooling, and alignment and integration issues), new lab test bench results on electronics and sensors. The perspectives over a period of four years are presented with a detailed test beam schedule and the roadmap including the construction of new mechanical prototypes equipped with front end and readout chips in deep sub-micron CMOS technology are discussed. Combined tests with other sub-detectors are finally addressed. This test beam program is inserted in the framework of the EUDET European project. on behalf of the SiLC R&D Collaboration     

Core-level photoemission study of 2D ordered Bi/Si(100) interfaces

A high resolution core-level photoemission investigation of 2D ordered Bi layers grown on Si(100)-(2×1) is presented. We study the Si 2p and Bi 5d core-levels at room temperature as a function of coverage and in the reconstructed phases. The different Bi structural configurations around the monolayer coverage and in the (2×n)-reconstructed phase are derived from the core-level lineshape evolution. By following the Fermi level pinning, the presence of Bi-induced occupied electronic states close to the Si mid-gap is suggested.     

Spatially resolved dynamics of the TiO2(1 1 0) surface reconstruction

We use low-energy electron microscopy to image the reversible transformation of the TiO₂(1 1 0) surface between a high-temperature 1 × 1 structure and a low-temperature 1 × 2 structure. The reconstruction dynamics are novel: 1 × 2 bands nucleated during cooling at the steps of the starting 1 × 1 surface and then grew laterally from the steps. The transformation kinetics are dominated by mass flow from the surface to the bulk, a process that facilitates converting the high-density 1 × 1 phase to the lower-density 1 × 2 phase. We have also imaged how the 1 × 1 surface reconstructs to 1 × 2 phase after sufficient oxygen is removed from the crystal’s bulk during vacuum annealing. 1 × 2 bands also nucleated and grew laterally from the initial 1 × 1-surface’s steps. However, because this isothermal 1 × 1-to-1 × 2 transition occurs largely by mass redistribution on the surface, the steps of the initial 1 × 1 surface and final 1 × 2 surface are offset. We propose models of mass redistribution during the 1 × 1/1 × 2 phase transition to explain this effect. We conclude that the phase transition is first-order because it always occurred by the nucleation and growth of discrete phases. Finally, we show that quenching can roughen TiO₂’s surface by forming pits and that changing temperature causes step motion on 1 × 2 surfaces.