共查询到20条相似文献,搜索用时 109 毫秒
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G. A. Lenkova 《Optics and Spectroscopy》2011,111(1):100-106
A physical interpretation of the focal shift is given based on geometrical optics. The results of an analytical study of the
focal shift depending on the Fresnel numbers are presented. The effect of the aperture diameter and the width of the central
zone of the phase Fresnel lens on the distribution of the light intensity along the axis upon illumination by a convergent
light beam is analyzed. 相似文献
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We use a generalized refractive index that includes diffraction effects to show that the Gouy phase shift can be seen as an intensity averaged optical path difference between the generalized eikonal and the geometrical eikonal. This approach generalizes previous treatments to include the effects of phase distortion and confirms the role of transverse spatial confinement in the Gouy shift. 相似文献
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A new method is presented for synthesizing arbitrary intensity patterns based on phase contrast imaging. The concept is grounded on an extension of the Zernike phase contrast method into the domain of full range [0; 2π] phase modulation. By controlling the average value of the input phase function and by choosing appropriate phase retardation at the phase contrast filter, a pure phase to intensity imaging is accomplished. The method presented is also directly applicable in dark field image synthesis. 相似文献
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A modified point diffraction interferometer is presented, where interference is made in the first diffracted order of a composite grating. A 180° phase shift between reference and object beam is introduced to obtain a complete image contrast reversal. 相似文献
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We describe in this paper a speckle interferometer constituted by two partially diffusing plates. They are illuminated by a laser and the resulting intensity distribution is observed in the image plane of the source. Each speckle of this plane (Fourier plane) is modulated by a ring system whose interference order depends on its phase. Since the observation plane is a Fourier plane, a longitudinal or lateral shift of one of the diffusers results only into a change of the modulating fringes, the speckles themselves remaining unchanged. A photographic plate which records successively the intensity distribution lying in the Fourier plane before and after the considered shift, exhibits after processing a system of Moiré fringes, the shape of which depends on the nature of the translation given to the diffuser between the exposures. 相似文献
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Henryk Szmacinski Joseph R. Lakowicz W. J. Lederer K. Nowaczyk Michael L. Johnson 《Journal of fluorescence》1993,3(3):161-167
Fluorescence lifetime imaging microscopy (FLIM) is a new methodology for studying the spatial and temporal dynamics of macromolecule, molecules, and ions in living cells. In FLIM image contrast is derived from the mean fluorescence lifetime at each point in a two-dimensional image. In our case the lifetime was measured by the phase-modulation method. We describe our FLIM apparatus, which consists of a fluorescence microscope, high-speed gated proximity focused MCP image intensifier, and slow-scan CCD camera. To accomplish subnanosecond time-resolved imaging, the gain of the image intensifier is modulated with a high-frequency signal, resulting in stationary phase-sensitive intensity images on the image intensifier. These images are recorded using a cooled slow-scan CCD camera and stored in an image processor. The lifetime images are created from a series of phase-sensitive images at various phase shift of the gain-modulation signal. We demonstrate calcium concentration imaging in living COS cells based on Ca2+-induced lifetime changes of Quin-2. The phase-angle image is mapped to the Ca2+ concentration image using anin vitro-determined calibration curve. The Ca2+ concentration was found to be uniform throughout the cell. In contrast, the intensity image shows significant spatial differences, which likely reflect variations in the thickness and distribution of probe within the cell. 相似文献
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A. V. Tavrov 《Technical Physics》2010,55(3):400-408
A common-path interferometer that is intended for observation of a faint off-axis light source against the background of an
intense on-axis source is suggested. The on-axis source and its replicated image acquire an achromatic phase shift of 180°
and interfere in antiphase. The achromatic phase shift is due to the geometrical phase in the configuration of a 3D interferometer.
Interference spatially separates the dark and bright fields of the on-axis source by directing them to different sides of
a beam splitter. At the same time, interference does not attenuate the field of the off-axis source, directing it to different
sides of the beam splitter with equal intensities. Such a configuration of the common-path interferometer provides mechanical
stability. 相似文献
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Hamilton’s theory of turns for the group SU(2) is exploited to develop a new geometrical representation for polarization optics.
While pure polarization states are represented by points on the Poincaré sphere, linear intensity preserving optical systems
are represented by great circle arcs on another sphere. Composition of systems, and their action on polarization states, are
both reduced to geometrical operations. Several synthesis problems, especially in relation to the Pancharatnam-Berry-Aharonov-Anandan
geometrical phase, are clarified with the new representation. The general relation between the geometrical phase, and the
solid angle on the Poincaré sphere, is established. 相似文献
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A method of visualization of phase objects is described based on selective properties of the Bragg diffraction of light by ultrasound. The main attention is focused on specific features of visualization in tangential geometry of the acousto-optical interaction. It is shown that, in the optimized case, the light intensity distribution in the visualized image is proportional to the phase gradient. The resolution and contrast of the visualized image are analyzed numerically. Potentialities of the method are illustrated by examples of computer simulation of the visualization effect. 相似文献
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Wenjing Zhou Qiangsheng Xu Yingjie Yu Anand Asundi 《Optics and Lasers in Engineering》2009,47(9):896-901
A digital phase-shifting in-line holographic system based on the single coherence beam is developed. A series of phase-shifting fringes are generated by computer and outputted by a digital micro-mirror device (DMD). These fringes modulate the coherence beam because of the intensity modulation ability of DMD. In this work, the reconstructed conjugate image would not appear because of applying the phase-shifting algorithm. And calibration for the value of the optical phase shift is not necessary. An experiment based on a lens-less digital in-line micro-holographic setup with a phase grating specimen is conducted to demonstrate the validity of the present method. 相似文献
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A new method of absolute phase evaluation for three-dimensional (3D) profile measurement using fringe projection is presented, which combines the gray code and the phase shift technique. Two kinds of fringe patterns are projected onto the object surface respectively, one is sinusoidal intensity distribution used for phase demodulation and the other is gray code fringe pattern for unwrapping. These images are acquired by camera and stored into computer. The absolute phase is obtained by analyzing these images. The validity of this method is verified experimentally. The method is superior to other phase unwrapping methods. 相似文献
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提出了用相位型错位光栅产生光学双阱的新方案.用平面光波(或TEM00模式高斯光波)照射、正透镜聚焦,在透镜焦平面上产生的适用于冷原子或冷分子囚禁的多对可调光学双阱.计算和推导了双阱的光强分布、强度梯度以及光阱的几何参数与光学系统参数间的解析关系,研究了双阱到单阱三种不同的演化过程.同时还计算了光学双阱囚禁冷原子的光学偶极势和光子散射速率.研究发现,该方案不仅简单可行、操作方便,而且在原子物理、原子光学、分子光学和量子光学领域中有着广阔的应用前景.
关键词:
原子光学
相位光栅
光学双阱
冷原子囚禁 相似文献
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It is known from a number of publications that when a converging, monochromatic spherical wave is diffracted at a circular aperture, the point of maximum intensity of the diffracted wave may not be at the geometrical focus of the incident wave, but may be located closer to the aperture. In the present note we show that when the incident wave is uniform and the angular semi-aperture is small, the ratio of such a shift Δ? of the point of maximum intensity to the distance ? between the geometrical focus and the plane of the aperture depends only on the Fresnel number N of the aperture when viewed from the geometrical focus. The effect becomes significant when N ? 5. When N = 1, for example, |Δ?| ≈ 0.4 ? and the maximum intensity is approximately twice as large as the intensity at the geometrical focus. 相似文献
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Masaaki Adachi 《Optical Review》2008,15(3):148-155
White-light interference has changes in fringe contrast. When phase-shift techniques are applied to white-light interference,
the phase-shift algorithm which can extract the phase accurately under the contrast changes is required. There is often another
requirement that the phase shift between frames should not be restricted to π/2. Computer simulations show that the well-known algorithms have non-negligible errors under both requirements. To find an
algorithm which will satisfy the requirements, I extract individual terms (I
j
∓ I
k
) in an algorithmic equation by considering symmetry of light intensity against phase, where I
j
is light intensity just after the j-th phase shift. Using computer simulations, I search for appropriate coefficients by which the terms are multiplied in the
equation, finally finding an algorithm which satisfies both the requirements with the phase shift used. 相似文献
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相干反斯托克斯拉曼散射(CARS)显微能够对样品的特殊化学组分进行选择性成像,无需荧光标记,在生物医学领域被广泛应用.然而,传统的CARS图像往往存在非共振背景信号.本文将基于光强传输方程的单光束相位成像技术用于CARS显微成像,来抑制CARS的非共振背景信号.该方法通过记录样品在三个相邻平面上的CARS图像,然后利用光强传输方程获取CARS光场的相位分布,最后利用共振CARS信号和非共振背景信号在相位上的差异,实现了对背景噪声的抑制.该方法无需参考光,通过三次测量可完成CARS的背景噪声抑制,具有良好的应用前景. 相似文献