Showing papers by "Min Gu published in 1998"
TL;DR: It is shown by means of3D Fourier space analysis that successful reading of 3D data can be obtained by selection of the appropriate parameter for the RCM.
Abstract: We propose to use a reflection confocal microscope (RCM) as a readout system for digital data stored in a three-dimensional (3D) photochromic optical memory. We describe the merits and the difficulties for 3D optical memory that are associated with the use of such a RCM.It is shown by means of 3D Fourier space analysis that successful reading of 3D data can be obtained by selection of the appropriate parameter for the RCM.The system parameters include the numerical aperture of the objective lens and the wavelength of the light used for analysis (reading). Experimental results of multilayer recording and reflection confocal reading in photochromic-molecule-doped poly(methyl methacrylate) are presented. Good-contrast images are obtained.
157 citations
TL;DR: It is found both theoretically and experimentally that spherical aberration can be compensated for by a change in the tube length at which a microscope objective is operated in recording and reading processes.
Abstract: Reported is an investigation into the effect of spherical
aberration caused by the mismatch of the refractive indices between the
recording material and its immersion medium on the three-dimensional
optical data-storage density in a two-photon bleaching polymer. It
is found both theoretically and experimentally that spherical
aberration can be compensated for by a change in the tube length at
which a microscope objective is operated in recording and reading
processes. After compensation for the spherical aberration it is
possible to achieve a three-dimensional recording density of 3.5
Tbits/cm3 for a commercial objective with a numerical
aperture of 1.4.
93 citations
TL;DR: In this article, the authors investigated the transverse trapping force in laser tweezers in the presence of spherical aberration caused by the refractive-index mismatch between a cover slip and the water solution where particles are suspended.
Abstract: Transverse trapping force in laser tweezers is investigated in the presence of spherical aberration caused by the refractive-index mismatch between a cover slip and the water solution where particles are suspended. The transverse trapping efficiency is characterized in terms of the numerical aperture of a microscope objective and the thickness of a sample cell. It has been experimentally demonstrated that the spherical aberration can be compensated for by changing the effective tube length of an objective used for trapping. As a result, the transverse trapping efficiency can be improved by up to 20%. In principle, a further improvement in the trapping efficiency is possible if an objective of an infinitely-long tube length is used.
63 citations
TL;DR: A new method for microscopic imaging of an object embedded in a turbid medium, based on the differential polarization-gating mechanism, is reported, which achieves an image resolution of tens of micrometers, which is approximately 10 times better than that achieved in transillumination imaging in a similar medium.
Abstract: We report a new method for microscopic imaging of an object embedded in a turbid medium, based on the differential polarization-gating mechanism. It is demonstrated that with this method, image resolution through optically thick milk suspensions can be improved by as much as 30% compared with no-gating methods. An image resolution of tens of micrometers is achieved in an optically thick turbid medium, which is approximately 10 times better than that achieved in transillumination imaging in a similar medium.
36 citations
TL;DR: In this paper, the relationship of image resolution to scattered photons, which experience different numbers of scattering events, is explored in a scanning microscope, and the effects of the numerical aperture of a microscope objective and the detector size on image resolution that is contributed by scattered photons are carefully investigated.
Abstract: Image formation in a turbid medium under a microscope is studied both theoretically and experimentally. In particular, the relationship of image resolution to scattered photons, which experience different numbers of scattering events, is explored in a scanning microscope. The effects of the numerical aperture of a microscope objective and the detector size on image resolution that is contributed by scattered photons are carefully investigated. The results show that for an object embedded in a turbid medium of a thickness of 12 scattering mean-free-path lengths, transverse resolution of an image contributed by scattered photons is much lower than the diffraction-limited resolution. A criterion for determining the efficiency of a gating method is proposed in terms of the relationship of resolution to signal strength.
28 citations
TL;DR: A new method for microscopic imaging of an object embedded in a turbid medium based on the angle-gating mechanism achieved by the use of polarized annular objectives in the illumination and collection paths of a microscopic imaging system is reported.
Abstract: We report a new method for microscopic imaging of an object embedded in a turbid medium. The new method is based on the angle-gating mechanism achieved by the use of polarized annular objectives in the illumination and collection paths of a microscopic imaging system. A detailed experimental study is presented of the effects of the size of annular obstructions on image quality when turbid media, including polystyrene microspheres and milk suspensions, are imaged. Images of 22-mum polystyrene microspheres embedded in the turbid media show that misinterpretation can occur when circular objectives are used, because of the detection of mainly multiply scattered photons (i.e., diffusing photons). However, when annular objectives are employed, diffusing photons from a turbid medium can be efficiently suppressed; thus image contrast appears correctly, and image resolution is increased.
22 citations
TL;DR: In this paper, the effect of the scattering particle size in a turbid medium on microscopic imaging is experimentally investigated in order to determine the resolution achievable when differential polarisation-gating (DPG) is employed.
15 citations
TL;DR: In this paper, the authors report on the construction and characterisation of a novel double-pass confocal scanning microscope that uses a four-port fiber coupler and a self-aligned, compact, vibration-free, and purely coherent imaging system.
Abstract: 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.
10 citations
Journal Article•
TL;DR: In this article, an analysis of the light field and intensity distribution within a double-layer thin-film stack coated on a prism is presented, and the effect of the thickness and the refractive index of a sample is investigated in order to use the double layer structure in near-field microscopy.
4 citations
TL;DR: A significant improvement in image resolution and contrast is obtained when a polarizing annular objective is used to image a reflective test bar through various turbid media.
Abstract: In this report, we describe the implementation of an angle-gating mechanism into a reflection optical microscope for imaging through a turbid medium. A significant improvement in image resolution and contrast is obtained when a polarizing annular objective is used to image a reflective test bar through various turbid media. The experimental results confirm that the improvement is caused by the efficient suppression of diffused photons scattered from the turbid medium when a polarized annular objective is employed as an angular gate.
3 citations
TL;DR: Three-dimensional image formation in an interference confocal scanning microscope under ultrashort pulsed beam illumination is investigated and spatial resolution in the axial and transverse directions is improved by approximately 45% and 15%, respectively, compared with that in the case of continuous wave illumination.
Abstract: Three-dimensional image formation in an interference confocal scanning microscope under ultra-short pulsed beam illumination is investigated in this study. The novelty of this new image system is that it keeps advantages in femtosecond interferometry but also provides a femtosecond-resolved three-dimensional image without necessarily using an ultrafast detector. For a 5-fs pulsed beam illumination, spatial resolution in the axial and transverse directions in this system is improved by approximately 45% and 15%, respectively, compared with that in the case of continuous wave illumination. However, strong chromatic aberration caused by an ultrashort pulsed beam can result in a degradation of spatial and temporal resolution, whereas weak chromatic aberration may lead to an improvement in transverse resolution.