Interfacial shape and contact-angle measurement of transparent samples with confocal interference microscopy

A model has been developed that predicts the effective optical path through a thick, refractive specimen on a reflective substrate, as measured with a scanning confocal interference microscope equipped with a high-numerical-aperture objective. Assuming that the effective pinhole of the confocal microscope has an infinitesimal diameter, only one ray in the illumination bundle (the magic ray) contributes to the differential optical path length (OPL). A pinhole with finite diameter, however, allows rays within a small angular cone centered on the magic ray to contribute to the OPL. The model was incorporated into an iterative algorithm that allows the measured phase to be corrected for refractive errors by use of an a priori estimate of the sample profile. The algorithm was validated with a reflected-light microscope equipped with a phase-shifting laser-feedback interferometer to measure the interface shape and the 68 degrees contact angle of a silicone-oil drop on a coated silicon wafer.     

Multifocus confocal Raman microspectroscopy for fast multimode vibrational imaging of living cells

We have developed a multifocus confocal Raman microspectroscopic system for the fast multimode vibrational imaging of living cells. It consists of an inverted microscope equipped with a microlens array, a pinhole array, a fiber bundle, and a multichannel Raman spectrometer. Forty-eight Raman spectra from 48 foci under the microscope are simultaneously obtained by using multifocus excitation and image-compression techniques. The multifocus confocal configuration suppresses the background generated from the cover glass and the cell culturing medium so that high-contrast images are obtainable with a short accumulation time. The system enables us to obtain multimode (10 different vibrational modes) vibrational images of living cells in tens of seconds with only 1 mW laser power at one focal point. This image acquisition time is more than 10 times faster than that in conventional single-focus Raman microspectroscopy.     

一种全场三维共焦检测的新方法

提出了一种利用微光学阵更合成器件实现全场三维面形并行检测、记录的共焦方法。此方法的关键是，在共焦系统中引入一一微光学耻列合成器件来产生一点光源阵列，实现了对同一一剖面同时并行检测，并首次采用了ＣＣＤ面阵像元取代上孔光阑直接截取三维信息光强。本文讨论了该方法的三信息检测原理，响应关系，给出了初步的实验结果和三维重构图。     

A desktop X‐ray monochromator for synchrotron radiation based on refraction in mosaic prism lenses

Focusing planar refractive mosaic lenses based on triangular prism microstructures have been used as an alternative approach for wide‐bandpass monochromatization of high‐energy X‐rays. The strong energy dependence of the refractive index of the lens material leads to an analogous energy dependence of the focal length of the lens. The refractive mosaic lens, in comparison with the refractive lens of continuous parabolic profile, is characterized by a higher aperture because of reduced passive material. In combination with a well defined pinhole aperture in the focal plane, the transmittance of photons of an appropriate energy can be relatively high and photons of deviating energy can be efficiently suppressed. The photon energy can be tuned by translating the pinhole along the optical axis, and the bandwidth changed by selecting appropriate pinhole aperture and beam stop. This method of monochromatization was realised at the ANKA FLUO beamline using a mosaic lens together with a 20 µm pinhole and beam stop. An energy resolution of 2.0% at 16 keV has been achieved.     

Micromachined transmissive scanning confocal microscope

We have developed a miniature scanning confocal microscope that uses electrostatically actuated microlenses for focusing and scanning. Objective lenses, scanners, a pupil, and a pinhole of the confocal microscope are microfabricated and integrated into a volume smaller than 2 mm3 by stacking these components. Objective lenses are composed of two vertically cascaded polymer microlenses integrated into micromachined comb actuators. Raster scanning is implemented by electrostatically actuating each microlens in orthogonal directions. We have demonstrated reflection confocal imaging with 3-microm transverse resolution over a 100-microm field of view and a 0.38-mm working distance at lambda = 633 nm.     

Improving contrast and sectioning power in confocal imaging by third harmonic generation in SiOx nanocrystallites

We present a new optical microscope in which the light transmitted by a sample-scanned transmission confocal microscope is frequency-tripled by SiOx nanocrystallites in lieu of being transmitted by a confocal pinhole. This imaging technique offers an increased contrast and a high scattered light rejection. It is demonstrated that the contrast close to the Sparrow resolution limit is enhanced and the sectioning power are increased with respect to the linear confocal detection mode. An experimental implementation is presented and compared with the conventional linear confocal mode.     

Suppression for the Low spatial frequency Rings and Ripples of Laser Near field Intensity Distribution in the Spatial Filter Used in ICF Laser DriveSupported by the key project of the National Science Foundation, National Hi Tech Foundation.

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Parallel confocal detection of single molecules in real time

The confocal detection principle is extended to a highly parallel optical system that continuously analyzes thousands of concurrent sample locations. This is achieved through the use of a holographic laser illumination multiplexer combined with a confocal pinhole array before a prism dispersive element used to provide spectroscopic information from each confocal volume. The system is demonstrated to detect and identify single fluorescent molecules from each of several thousand independent confocal volumes in real time.     

Autoconfocal microscopy with a cw laser and thermionic detection

We introduce an application of thermionic emission in a PMT photocathode. Because of the nonlinear dependence of thermionic emission on absorbed laser power, a conventional PMT is found to produce a virtual pinhole effect that rejects unfocused light at least as strongly as a physical pinhole. This virtual pinhole effect is exploited in a scanning transmission confocal microscope equipped with a cw laser source. Because the area of the PMT photocathode is large, signal descanning is not required and thermionic detection acts as a self-aligned pinhole. Our technique of thermionic-detection autoconfocal microscopy is further implemented with graded-field contrast to obtain enhanced phase-gradient sensitivity in unlabeled samples, such as rat hippocampal brain slices.     

Confocal microscopy with a volume holographic filter

We describe a modified confocal microscope in which depth discrimination results from matched filtering by a volume hologram instead of a pinhole filter. The depth resolution depends on the numerical aperture of the objective lens and the thickness of the hologram, and the dynamic range is determined by the diffraction efficiency. We calculate the depth response of the volume holographic confocal microscope, verify it experimentally, and present the scanned image of a silicon wafer with microfabricated surface structures.     

Phase-sensitive detection of dipole radiation in a fiber-based high numerical aperture optical system

We theoretically study the problem of detecting dipole radiation in a fiber-based confocal microscope of high numerical aperture. By using a single-mode fiber, in contrast to a hard-stop pinhole aperture, the detector becomes sensitive to the phase of the field amplitude. We find that the maximum in collection efficiency of the dipole radiation does not coincide with the optimum resolution for the light-gathering instrument. The derived expressions are important for analyzing fiber-based confocal microscope performance in fluorescence and spectroscopic studies of single molecules and/or quantum dots.     

Improved axial resolution in confocal fluorescence microscopy using annular pupils

The axial image of a thick fluorescent layer is studied in a confocal microscope consisting of either circular or annular pupils. The response for circular pupils is sharper than that for annular pupils if a small pinhole detector is used. But when the size of the pinhole is larger than a certain value, the response in the latter case can become sharper than that in the former. This result implies that for a given detector of finite size, axial resolution in confocal fluorescence microscopy can be improved when an annular lens is used. Our experimental results qualitatively demonstrate the theoretical prediction. The strength of optical sectioning and the axial cross-section of the three-dimensional optical transfer function are also derived from the measured data.     

Combined Raman and continuous-wave-excited two-photon fluorescence cell imaging

We demonstrate a confocal optical microscope that combines cw two-photon-excited fluorescence microscopy with confocal Raman microscopy. With this microscope fast image acquisition with fluorescence imaging can be used to select areas of interest for subsequent chemical analysis with spontaneous Raman imaging. The distribution of the UV-absorbing fluorophore Hoechst 33342 in the apoptotic HeLa cells is measured in the combined cw two-photon-excited fluorescence and Raman microscopy modes. The 647-nm line of a Kr-ion laser is used to excite both the Raman scattering and the two-photon-excited fluorescence emission. The lateral and axial resolutions in the two imaging modes are compared by use of the Gaussian beam approximation and backprojection of the focal volume through the confocal pinhole.     

Phase retrieval and coherent diffraction imaging by a linear scanning pinhole sampling array

We propose a new method for phase retrieval and coherent diffraction imaging by a specially designed pinhole sampling array (PSA) based on a liquid crystal spatial light modulation. We demonstrate that the phase and the amplitude of the wave front passing through a pinhole sampling array plate can be directly extracted from the inverse Fourier transform of the far-field diffraction intensity pattern. Scanning the whole surface of the wave front by such a series of the PSA plates, we can assemble the extracted complex amplitude to a two-dimensional discrete distribution of the sampled wave front covering the entire PSA plate plane in the scanning consequence. We called it linear scanning pinhole sampling array (LSPSA). Thus the wave front can be reconstructed which avoids any iterative algorithms. Furthermore, it provides a feasible approach for lensless coherent diffraction imaging in real-time.     

All-optical super resolved and extended depth of focus imaging with random pinhole array aperture

In this paper, we present a novel approach which allows combining super resolved imaging with extended depth of focus while the result is obtained by all-optical means and no digital processing is required. The presented approach for the super resolved imaging includes attaching a random pinhole array plate to the aperture plane of the imaging system. The energetic efficiency of the system is high and it is much larger than an imaging through a single pinhole which also has extended depth of focus. The super resolving result is obtained by mechanic scanning of the aperture plane with the random plate.     

High-contrast microscopy of semiconductor and metal sites in integrated circuits by detection of optical feedback

High-contrast microscopy of semiconductor and metal sites in integrated circuits is demonstrated with laser-scanning confocal reflectance microscopy, one-photon (1P) optical-beam-induced current (OBIC) imaging, and detection of optical feedback by means of a commercially available semiconductor laser that also acts as an excitation source. The confocal microscope has a compact in-line arrangement with no external photodetector. Confocal and 1P OBIC images are obtained simultaneously from the same focused beam scanned across the sample plane. Image pairs are processed to generate exclusive high-contrast distributions of semiconductor, metal, and dielectric sites in a GaAs photodiode array sample.     

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.     

Detection of Volume Changes in Calcein-Stained Cells Using Confocal Microscopy

Calcein is an intracellular fluorescent probe that has been used as an indicator of cell volume in several previous studies. These studies have reported two different fluorescence responses depending on the optical setup used to collect the data: wide-field microscopy has resulted in a decrease in fluorescence upon cell shrinkage, whereas confocal microscopy has been shown to yield the opposite result. In this short communication, we have investigated the effect of optical setup on detection of cell volume changes in calcein-stained endothelial cells. A confocal microscope was used to collect the fluorescence data, and the pinhole diameter was varied in order to examine the effects of optical section thickness on fluorescence response. For large pinhole diameters – which correspond to relatively thick optical sections – fluorescence intensity decreased when cells were induced to shrink. In contrast, for small pinhole diameters the fluorescence intensity increased with cell shrinkage. The transition between these two types of fluorescence responses occurred when using a pinhole diameter of 285 μm, which corresponds with an optical section thickness slightly less than the height of the cells. Our results have implications for the design and interpretation of experiments involving the use of calcein as a cell volume indicator.     

无外加氟施主产生KrF准分子发射谱实验研究

We report a new technique to suppress the low-spatial-frequency rings and ripples (LSFRs) of laser near-field intensity distribution in the spatial filter (SF) used in ICF laser drivers. This technique employs a spatial filter with Gaussian transmission, instead of the hard-edged pinhole, at the confocal plane of a Newtonian telescope. The resulting beam has a super-Gaussian transverse intensity profile without the LSFRs that certainly appear when a hard-pinhole was used as a filter in the conventional technique.     

Transport-based image reconstruction in turbid media with small source-detector separations

We demonstrate a new method for imaging through several millimeters of a turbid sample with a resolution of approximately 100 mum by combining aspects of confocal reflectance microscopy and diffuse optical tomography. By laterally displacing the pinhole aperture of a confocal microscope we can achieve small source-detector separations and detect minimally scattered light. A reconstruction algorithm based on the first Born approximation to the radiative transport equation is then used to reconstruct an image of a 100-mum absorbing object located 2 mm beneath the surface.