Transmission confocal laser scanning microscopy with a virtual pinhole based on nonlinear detection

We present a transmission-mode confocal laser scanning microscope system based on the use of second-harmonic generation (SHG) for signal detection. Our method exploits the quadratic intensity dependence of SHG to preferentially reveal unscattered signal light and reject out-of-focus scattered background. The SHG crystal acts as a virtual pinhole that remains self-aligned without the need for descanning.     

Fibre-optic double-pass confocal microscopy

This paper reports on the construction and characterisation of a novel double-pass confocal scanning microscope that uses a four-port fibre coupler. The new imaging system is self-aligned, compact, vibration-free, and purely coherent. Compared with fibre-optic transmission- and reflection-mode confocal systems, the fibre-optic double-pass confocal imaging system exhibits higher resolution.     

A lateral differential confocal microscopy for accurate detection and localization of edge contours

Common path noise and disturbance in light source and ambient lighting affect detection accuracy of edge contours greatly in optical microscopy. In order to solve this problem, a lateral differential confocal microscopy is proposed based on principle of lateral difference and confocal microscopy. The approach proposed uses confocal dual-receiving light path arrangement and real-time heterodyne subtraction of two signals with lateral offsets by a differential detector to improve the system′s accuracy and detection sensitivity. Theoretical analyses have been presented. In addition, a simple prototype system has been built based on theoretical analyses. Related experiments have been performed under laboratory conditions. Different from former image processing methods, common path noise and additive disturbance in light source and ambient lighting are eliminated before they are recorded. Theoretical analyses and experimental results indicate a more accurate and sensitive result.     

Wavelength division multiplexed confocal microscopy using supercontinuum

We investigate both theoretically and experimentally wavelength division multiplexed confocal imaging by using white light supercontinuum. We show that with the optimized pinhole diameter an axial resolution of 0.75 μm and detection efficiency of 80% can be achieved. In addition, we applied the axial WDM confocal system to 3D surface measurement and the result agreed well with that measured by commercially available surface profilometer. The measured sensitivity of the system is 3.25 nm. Finally, we demonstrated lateral confocal imaging by using supercontinuum. An effective lateral scanning range of 130 μm was obtained.     

Chromatic confocal microscopy with a finite pinhole size

Chromatic confocal microscopy has the advantage of short measurement times because of its parallel depth scan. As most white-light sources have limited optical output power, light-efficient setups are necessary. Using an extended detection pinhole is one way to improve light efficiency. We have calculated the effect of extended pinholes in chromatic confocal setups. We found that, for certain pinhole sizes, the FWHM of the confocal signal is nearly constant over a large wavelength interval.     

Dual-axes differential confocal microscopy with high axial resolution and long working distance

We discover that the slight transverse offset of a point detector results in a shift of the axial intensity response curve in a dual-axes confocal microscopy (DCM). Based on this, we propose a new dual-axes differential confocal microscopy (DDCM) with high axial resolution and long working distance, in which two point detectors are placed symmetrically about the collection axis. And a signal is obtained through the differential subtraction of two signals received simultaneously by the two point detectors. Theoretical analyses and preliminary experiments indicate that DDCM is feasible and suitable for the high precision tracing measurement of microstructures and surface contours.     

共聚焦显微镜激光高速扫描控制系统设计及实现

 在传统光学扫描方法基础上,有效地将检流式与共振式光学扫描振镜结合起来,提出一种速度可达4 M/s采样率的高速激光扫描方法,并基于单片机系统设计搭建了系统控制硬件平台,编写了上位机端和下位机端应用软件。实验结果表明:该控制系统扫描速度快,性能稳定可靠,能够应用于共聚焦显微镜,实现实时扫描成像 。     

Dual-axes confocal microscopy with post-objective scanning and low-coherence heterodyne detection

We present a dual-axes confocal microscope that employs postobjective scanning and low-coherence heterodyne detection to collect vertical cross-sectional images from biological tissue with high axial resolution, reduced noise from scattered light, deep tissue penetration, and a large dynamic range. This architecture can be scaled down to millimeter dimensions with microelectromechanical systems technology for performance of in vivo optical biopsy.     

Measurement of steep edges and undercuts in confocal microscopy

Confocal microscopy is widely used to measure the surface topography of specimen with a precision in the micrometer range. The measurement uncertainty and quality of the acquired data of confocal microscopy depends on various effects, such as optical aberrations, vibrations of the measurement setup and variations in the surface reflectivity. In this article, the influence of steep edges and undercuts on measurement results is examined. Steep edges on the specimen's surface lead to a reduced detector signal which influences the measurement accuracy and undercuts cause surface regions, which cannot be captured in a measurement. The article describes a method to overcome the negative effects of steep edges and undercuts by capturing several measurements of the surface with different angles between the surface and the optical axis of the objective. An algorithm is introduced which stitches different angle measurements together without knowledge of the exact position and orientation of the rotation axis. Thus, the measurement uncertainty due to steep edges and undercuts can be avoided without expensive high-precision rotation stages and time consuming adjustment of the measurement setup.     

Improvements in confocal microscopy imaging using serrated divided apertures

Confocal microscopy with serrated divided apertures is presented. Compared with using two smooth D-shaped apertures in confocal microscopy, the serrated divided apertures can suppress the out-of-focus central bright spot, thus increasing the efficiency of rejection of scattered light. Diffraction analysis shows that the serrated apertures maintain the optical sectioning strength while attenuating the background coming from far from the focal plane. In addition, the signal to background ratio (S/B) is also improved.     

High-sensitivity piezoelectric tube sensor for shear-force detection in scanning near-field optical microscopy

An easy-to-implement non-optical shear-force detection setup for tip–sample distance regulation in scanning near-field optical microscopy is demonstrated. The detection method is based on attaching the near-field probe to a piezoelectric tube resulting in excellent mechanical contact between tip and detector. The main advantages of the method are good signal-to-background contrast and thus potential for high sensitivity. The method is demonstrated by obtaining approach curves of silicon surfaces. The suitability for optical experiments is further shown by measuring the near-field intensity distribution of the emission of a semiconductor laser.     

The coaxial tip as a nano-antenna for scanning near-field microwave transmission microscopy

A novel scanning-probe setup is reported that maps the complex transmission of microwaves. Response to topographic features as small as 15 nm was observed. The sharpened coaxial probe tip serves as a microwave antenna and, at the same time, as a tunnel tip to warrant precise distance control by STM (scanning tunneling microscope) feedback. The instrument can be applied to map the microwave conductivity of, e.g. thin films or low-dimensional semiconductors. Consequences for the development of an infrared microscope are outlined.     

Large field of view MEMS-based confocal laser scanning microscope for fluorescence imaging

Although confocal fluorescence microscopes are widely used in biology and have been proven to be promising diagnostic tools in dermatologic diagnostics, they are at present uncommon in medical practice. This is mainly due to high costs of acquisition and their large and complex outline. With the integration of a MEMS scanner we present a demonstration system of a confocal fluorescence laser scanning microscope which is affordable and portable. It has a field of view of 500 μm × 500 μm and is mainly composed of off-the-shelf components.     

Shrinking of ultrathin polyelectrolyte multilayer capsules upon annealing: A confocal laser scanning microscopy and scanning force microscopy study

Heating-induced morphological changes of micrometer size capsules prepared by step-wise deposition of oppositely charged polyelectrolytes onto melamine formaldehyde (MF) latex particles and biological cells with subsequent dissolution of the core have been investigated by confocal laser scanning microscopy (CLSM) and scanning force microscopy (SFM). For poly(styrenesulfonate-Na salt)/poly(allylamine hydrochloride) polyelectrolyte capsules a remarkable heating-induced shrinking is observed. An increase of the wall thickness corresponding to the capsule diameter decrease is found. The morphology of these microcapsules after temperature treatment is characterized. The thickening of the polyelectrolyte multilayer is interpreted in terms of a configurational entropy increase via polyanion-polycation bond rearrangement. Received 20 January 2000     

An approach to achieve lateral superresolution for small probe confocal measurement system and its element

A shaped annular beam superresolution approach is proposed to improve a lateral resolution of a small probe laser confocal measurement system (LCMS). The approach proposed enables lateral superresolution measurement of LCMS to be achieved by using a binary optical diffractive element to shape a He–Ne Gaussian laser beam into an annular beam with an inner diameter of 0.87 mm and an outer diameter of 1.8 mm required for superresolution measurement, and shift the beam spatial frequency from low to high. And a binary optical element (BOE) with 16 phase levels is designed and fabricated to shape a Gaussian laser beam into an annular beam. Preliminary experimental results indicate that an intensity distribution of a shaped annular beam is in agreement with simulation results, the diffractive efficiency is 87.2%; LCMS lateral and axial resolutions of 0.2 μm and 3 nm are achieved, respectively, and its measurement range is expanded nearly to double, when BOE is used in LCMS and , NA=0.85.     

Optical inspection and characterization of microoptics using confocal microscopy

With the growing demand for microoptics in different areas the importance of the characterization increases. Methods for a fast defect detection in microlens arrays are developed. We present a technique where the confocal principle is applied for determining the variation and the absolute value of the focal length. Additionally, using a self–filtering method the deviation of the periodic structure of microlens arrays is investigated theoretically and experimentally. Point-like defects as well as aberrations have been detected. The introduced methods allow the fast, parallel characterization of microlens arrays.     

差动共焦显微成像高稳定三维扫描技术与系统

激光差动共焦显微镜具备高空间分辨率特点,但因其逐点扫描成像方式,扫描时间长,易受三维扫描系统不稳定和环境干扰等影响,产生系统漂移,影响仪器的空间分辨率。利用楔块机构高稳定特点,结合刹车机构的自由抱闸特性,设计了一种新型的轴向升降机构,由此构建了结构更具稳定特性的电动三维扫描系统。稳定性实验验证在搭建的激光差动共焦显微镜上进行,经过监测系统在90min内的轴向位置,轴向漂移小于50nm,与原三维扫描系统漂移140nm对比,漂移速度明显减慢,稳定性有显著提升,进而明显改善了差动共焦显微成像效果。     

Dual mode near-field scanning optical microscopy for near-field imaging of surface plasmon polariton

In this paper, we theoretically and experimentally demonstrate that metal coated apertured probes are efficient near-field probes on surfaces with high reflectivity for the scattering as well as for the collection mode near-field scanning optical microscopy (NSOM). We show that a blunt apertured metal coated tip is very effective in suppressing image dipoles which affect strongly the signals scattered from frequently used sharp metal tips or gold nanoparticle attached probes. By using a simultaneous collection and scattering mode (dual mode) NSOM we measure the near-field images of surface plasmon polariton (SPP) launched from a slit. The collection mode measures propagating SPP along lateral distance in a long scan range with high signal-to-noise ratio, and the scattering mode measures the polarization resolved near-field of SPP. Comparisons of the measured data obtained in the dual mode enable to easily characterize SPP and to separate the measured near-field into the propagating SPP and the directly transmitted light.     

扫描近场红外显微镜近场距离控制系统的改进

针尖 样品的距离控制系统是扫描近场红外显微镜的重要组成部分。切变力探测作为一种重要的近场距离控制手段而得到了广泛的应用。介绍了一种对切变力探测系统的改进方法 ,它可以有效地提高石英晶振音叉的品质因数 ,进而提高探测系统对切变力感应的灵敏度。给出了理论分析和实验验证结果