We proposed an incoherent self-interference digital holography imaging system based on the Michelson interferometer. The proposed system records holograms of USAF1951 resolution target, herbaceous stem crosscut, and osteocyte. The reconstruction of the captured hologram using a three-step generalized phase shift can effectively eliminate bias and a twin image and obtain a clear reconstructed image. Element 3 in group 9 on the USAF1951 resolution target can be clearly seen, and the resolution achieves 645 lp / mm. Results indicate that the diffraction distance can influence the reconstructed image quality, which was confirmed by analyzing their relationship. In addition, the hair hologram was reconstructed, thereby demonstrating that the proposed system can record a 3D image of the object.
Effects of dyes and initiators in the photopolymer on the holographic storage properties are studied. Diffraction efficiency of photopolymer with Erythrosin B (ErB) as dye is significantly larger than that the same photopolymer with Eosin Y (EY), Rose Bengal (RsB), Rodamine B (RoB) and Fluorescein (F) as dyes under the same conditions. The maximum absorption of ErB is closer to 514nm than the others, and the photobleaching rate constant of the initiating system is higher than the others. Compared with the holographic properties with triethanolamine(TEA) as initiator, diffraction efficiency of the photopolymer with N-phenylglycine(NPG) as initiator is lower, but the photopolymer shows higher stability.
Fresnel incoherent correlation holography (FINCH) shows great advantages of coherent-light-source-free, high lateral resolution, no scanning, and easy integration, and has exhibited great potential in recording three-dimensional information of objects. Despite the rapid advances in the resolution of the FINCH system, little attention has been paid to the influence of the effective aperture of the system. Here, the effective aperture of the point spread function (PSF) has been investigated both theoretically and experimentally. It is found that the effective aperture is mainly restricted by the aperture of the charge-coupled device (CCD), the pixel size of the CCD, and the actual aperture of the PSF at different recording distances. It is also found that the optimal spatial resolution exists only for a small range of recording distance, while this range would become smaller as the imaging wavelength gets longer, leading to the result that the optimal spatial resolution is solely determined by the actual aperture of the PSF. By further combining the FINCH system with a microscopy system and optimizing the recording distance, a spatial resolution as high as 0.78 μm at the wavelength of 633 nm has been obtained, enabling a much higher quality imaging of unstained living biological cells compared to the commercial optical microscope. The results of this work may provide some helpful insights into the design of high-resolution FINCH systems and pave the way for their application in biomedical imaging.
Volume holographic digital data storage has many performance characteristics including large storage capacity and high transfer rate. But there are some problems in the commercial applications for holographic digital disc of volume holographic digital data storage. A single beam setup is introduced in this article for holographic digital disc. In this new system, the reference beam and the information beam are coaxially arranged to perform reading and writing. This new single beam setup can reduce the complexity, the demand for mechanical precision, the size and cost of the conventional holographic digital storage setup using dual beams. And it is also compatible with the conventional optical disk technologies.
High-density holographic recording parameters changing with the exposure wavelength of a wideband sensitive photopolymer are studied. The results show that the maximum diffraction efficiency, exposure sensitivity, maximum refraction index modulation, dynamic range and the exposure time constant are all incremental with the increase of the exposure wavelength. The analysis indicates that the scattering plays an important role in the phenomenon.
We systematically study the transmission property of metallic short-slab pair and continuous wire structure metamaterial and its dependence on the system geometrical parameters in the infrared frequency regime, using the transfer-matrix method and the commercial code, CST Microwave Studio. It is found that the passband is sensitive to the length and the thickness of the continuous wire. As the length or thickness increases, the passband is slightly extended to a higher frequency. It is also found that the dependence of the passband on the material of dielectric layer.
Camera calibration is one of the indispensable processes to obtain 3D depth information from 2D images in the field of computer vision. Camera self-calibration is more convenient and flexible, especially in the application of large depth of fields, wide fields of view, and scene conversion, as well as other occasions like zooms. In this paper, a self-calibration method based on two vanishing points is proposed, the geometric characteristic of disappear points formed by two groups of orthogonal parallel lines is applied to camera self-calibration. By using the vectors' orthogonal properties of connection optical centers and the vanishing points, the constraint equations on the camera intrinsic parameters are established. By this method, four internal parameters of the camera can be solved though only four images taken from different viewpoints in a scene. Compared with the two other self-calibration methods with absolute quadric and calibration plate, the method based on two vanishing points does not require calibration objects, camera movement, the information on the size and location of parallel lines, without strict experimental equipment, and having convenient calibration process and simple algorithm. Compared with the experimental results of the method based on calibration plate, self-calibration method by using machine vision software Halcon, the practicability and effectiveness of the proposed method in this paper is verified.
A novel wideband sensitive dry holographic photopolymer sensitized by rose bengal (RB) and methylene blue (MB) is fabricated, the holographic storage characteristics of which are investigated under different exposure wavelengths. The result shows that the sensitive spectral band exceeds 200 nm in visible light range, the maximum diffraction efficiency under different exposure wavelengths is more than 40% and decreases with the decrease of exposure wavelength, the exposure sensitivity is not change with the exposure wavelength. This photopolymer is appropriate for wavelength multiplexing or multi-wavelength recording in digital holographic storage.
Digital holographic microscopy (DHM) is one of the most effective methods in imaging the weakly-scattering objects, such as small colloidal particles and most biological cells. Compared to phase contrast and differential interference contrast microscopy, DHM cannot only visualize but quantify these phase objects. In this work, a spiral phase modulated FINCH microscope was implemented. The core of the system is an in-line incoherent interferometer composed of a spatial light modulator (SLM) and a charge-coupled device. In order to enhance image contrast, the SLM was space-division multiplexed by a helical lens and a conventional lens. To study the properties of this vortex imaging system, the precise mathematical model of the Point Spread Function (PSF), which describes the intensity distribution in digital image of the system’s response to a point source, is determined for the first time from the view of wave optics. The experimental 2D PSF agrees well with that of simulated one. When the system is used for biological microscopic imaging the enhancement of edge contrast and the enlargement of field of view are obtained without loss of resolution.
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