Thick dye-doped poly(methyl methacrylate) films for real-time holography

Molding and direct-polymerization techniques are used for the fabrication of holographic materials based on dye-doped poly(methyl methacrylate). The thickness of the samples obtained ranges from several micrometers to several millimeters. Pump-signal cross modulation is studied experimentally, and photophysical mechanisms responsible for refractive-index and absorption changes are discussed. Self-developing intensity and polarization holographic recording capability, strong anisotropy of diffraction, and high angular selectivity are demonstrated in thick samples.     

Study on the method of precision adjustment of star sensor

Star sensors are indispensable spatial measurement sensors for high-resolution earth observation and astronomical observations, and the demand for high measurement accuracy of satellite sensors continues to increase; thus, the star sensor optical machine adjustment error cannot be ignored. The commonly used installation error correction method cannot solely meet the precision analysis requirements. In this paper, the relationship between the optical machine installation and the star sensor measurement error is analyzed, and several common adjustment error correction methods are compared. An adjustment method for optical machines is proposed to meet the requirements of very high precision star sensors. The assembly precision requirements of the investigated very high precision star sensor are analyzed considering the whole machine, and then the optical components are controlled through optical precision adjustments to satisfy the precision requirements. Finally, through the complete machine calibration, the star sensor precision adjustment for an optical machine structure is verified. This method meets the requirements of very high precision sensors and is suitable for the precision adjustment of optical machine structures, which is of practical significance to improve the precision of star sensors.     

实时视场拼接系统的设计与实现

当要求的场景尺寸超出一个光学传感器的范围时,同时取得完整的场景就成为一个难点.针对这一问题,采用多个光学传感器同时对场景进行采集,可以得到几幅互相有一定重叠的场景图像.应用改进的相位相关算法对重叠图像进行快速配准,应用渐入渐出融合算法消除拼缝,实现无缝大视场拼接.并将整套算法在以TMS320DM642为核心处理器的平台上实现,得以构成一个小型化视频拼接系统.实验结果表明,该系统可以自动地对存在一定重叠和旋转的两幅768×494分辨率、25帧/秒的视频图像进行拼接,获得无缝、清晰的大视场视频图像,满足系统实时性的要求.     

Nonparaxial model for the focusing of high-numerical-aperture photon sieves

Recently, a paraxially individual far-field model was presented for the focusing and imaging analysis of pinhole photon sieves. By use of a local Taylor expansion of the integrated function of the Rayleigh-Sommerfeld diffraction formula, the small-size property of the individual pinholes, and the linear superposition principle, we extend this model to the nonparaxial case of high-numerical-aperture photon sieves. Some related problems, such as the validity range of this nonparaxial model and the selection conditions for the individual pinholes, are also discussed in detail.     

Experimental characterization of focusing by high-numerical-aperture zone plates

High-numerical-aperture zone plates have important applications in high-resolution optical maskless lithography as well as scanning confocal microscopy. We describe two methods to experimentally characterize the focusing properties, i.e., the point-spread function, of such diffractive lenses. The first method uses spot exposures in photoresist and the second uses a conventional knife-edge scan. The experimental results agree well with rigorous theoretical calculations.     

Iterative algorithm of phase determination in digital holography for real-time recording of real objects

We propose a numerical method to obtain complex amplitude distribution of a three-dimensional (3D) object from a digital hologram. The method consists of two processes. The first process is to measure simultaneously a hologram of the 3D object and an object intensity distribution by two image sensors. These intensity distributions give us the amplitude and absolute value of phase of the 3D object at the image sensor plane. The second process is the determination of phase distribution by a proposed iterative process based on the criterion that the reconstructed 3D object is in focus and its conjugate reconstruction is out of focus. Numerical and experimental results show the effectiveness of the proposed method.     

Fast method for physical optics propagation of high-numerical-aperture beams

A method is presented that expands the scheme of physical optics propagation beyond the Fresnel approximation to include beams that are nonparaxial. The formalism retains most of the calculation advantages of the Fresnel approach; i.e., it is based on a single Fourier transform step. The kernel of the new transformation is no longer separable in Cartesian coordinates; thus the formalism can account for astigmatic coupling effects originating purely from diffraction. The validity limits of the proposed algorithm are explored. Analytical expressions, numerical simulation results, and experimental data are compared.     

A theoretical model for noise gratings recorded in acrylamide photopolymer materials used in real-time holography

Abstract

Among the different sources of noise in holography, noise gratings have been analysed extensively in photographic emulsions owing to the granular nature of these recording materials; however, information about photopolymers is quite scarce. The effect of age on transmittance curves in a photopolymer system, used as holographic recording material, shows the appearance of noise gratings. We present a theoretical model, which explains the results for transmittance as a function of time in the presence of noise gratings recorded in an acrylamide mixture photopolymer. Good agreement between theory and experience has been observed, and the model can be used to obtain an approximate value for the diffraction efficiency of noise gratings, as well as to explain the results of age in transmittance curves.     

Totally implantable real-time in vivo video telemetry monitoringsystem for implant biocompatibility studies

An implantable real-time video telemetry monitoring system was developed for remote monitoring and evaluation of tissue reactions to an implant such as a biosensor. Experimental coatings and treatments to improve the function of an implant can now be evaluated in situ and in real-time for improved blood vessel growth (angiogenesis), reduced inflammation, and reduction of foreign body encapsulation. A tissue site can be viewed, recorded, and evaluated for a continuous time period without surgical intervention, thereby saving animal lives. The implantable system comprises a miniaturized fiber optic lens-based CCD camera, a TV video transmitter, a 4-LED illumination module, and a 9 VDC battery source. The TV video signal is telemetried out to a TV set or video tape recorder having a tuner. The 512×492 display or printout image pixels represent a 1.6×1.2 mm field of view by virtue of a 1:3 tapered (3X optical magnification) lens. The apparent magnification thus can approach 200 power with a 200 μm resolution (4 μm Nyquist). Test pattern modulation transfer functions showed resolvability at 90.5 1p/mm (5.5 μm line width) for both telemetried and direct captured images. In vivo and ex vivo rat tissue images showed blood vessels with diameters of 5-10 μm. Various tissue types, such as muscle and connective tissues, were distinguishable, as were experimental drug delivery microspheres of 10-20 μm in diameter. Therefore, we conclude that we have developed a new tool to study tissue reactions to implants     

车联网视频交换系统的测试平台研究

目的:随着物联网技术发展,智慧交通的应用势必会成为未来整个交通系统的发展方向,其中车联网系统将是关注热点。目前全球已将视频信息大量应用于车车互联、车路互联以及车与管理平台互联中,由于目前尚未有统一的标准规范,不同厂家在视频集成过程中差异较大。因此,相关车联网视频交换系统的测试成为必须。方法:提出一种采用视频流主观评价与传输网络客观测试相结合的方法。结果:验证测试平台的可用性。结论:通过本次研究对车联网视频交换系统的验证测试方法提出新的思路,具备应用价值。     

A fuzzy-based impulse noise detection and cancellation for real-time processing in video receivers

In this paper, a simple fuzzy-based algorithm to remove the impulse noise from images is proposed. To achieve real-time applications, the proposed filter architecture, which combines fuzzy noise detection and noise filtering, is also designed. With low computational complexity, simulation results show that the proposed filters effectively remove the impulse noise.     

Removal of bias and the conjugate image in incoherent on-axis triangular holography and real-time reconstruction of the complex hologram

We present and experimentally test a new passive-device incoherent holographic system that removes the bias and the conjugate image. The system is based on the triangular interferometer with the modification of insertion of simple passive devices and can easily be extended for obtaining real-time complex holograms without bias and conjugate images for moving objects. A scheme for real-time reconstruction of the complex hologram is also presented and experimentally tested.     

进出口音视频产品能效测试技术研究

为完善我国音视频产品能效测试标准的不足,通过调研和追踪发达国家的能效法律法规与标准,制定音视频产品能效检测方法和榆测标准,提出我国应对国外音视频产品能效技术壁垒方法,可起到指导出口企业提升音视频产品能效水平、提高出口音视频产品竞争力的作用.     

Reduction of the spherical aberration effect in high-numerical-aperture optical scanning instruments

In modern high-numerical-aperture (NA) optical scanning instruments, such as scanning microscopes, optical data storage systems, or laser trapping technology, the beam emerging from the high-NA objective focuses deeply through an interface between two media of different refractive index. Such a refractive index mismatch introduces an important amount of spherical aberration, which increases dynamically when scanning at increasing depths. This effect strongly degrades the instrument performance. Although in the past few years many different techniques have been reported to reduce the spherical aberration effect, no optimum solution has been found. Here we concentrate on a technique whose main feature is its simplicity. We refer to the use of purely absorbing beam-shaping elements, which with a minimum modification of optical architecture will allow a significant reduction of the spherical aberration effect. Specifically, we will show that an adequately designed reversed-Gaussian aperture permits the production of a focal spot whose form changes very slowly with the spherical aberration.     

Optical tolerances of an actively tilted high-numerical-aperture two-lens objective for optical recording

Analytical expressions for the primary wave-front aberrations of an actively tilted two-lens objective are derived, and expressions for the higher-order wave-front aberrations for disk tilt of this lens system are presented. This analysis is important because the two-lens objective opens the way to achieving higher-numerical-aperture systems for optical recording with acceptable tolerances that cannot be achieved with a single-lens objective. To test whether the conclusions drawn from the analytically derived results remain valid for high numerical apertures, we compare the results with those obtained by ray tracing: It is shown not only that the two-lens system is tolerant of disk-thickness variations and decentering of the lenses but that it can also be made tolerant of disk tilt when the lens facing the disk is actively tilted.     

Polarization imaging by use of digital holography

We present what we believe to be a new digital holographic imaging method that is able to determine simultaneously the distributions of intensity, phase, and polarization state at the surface of a specimen on the basis of a single image acquisition. Two reference waves with orthogonal polarization states interfere with the object wave to create a hologram that is recorded on a CCD camera. Two wave fronts, one for each perpendicular polarization state, are numerically reconstructed in intensity and phase. Combining the intensity and the phase distributions of these two wave fronts permits the determination of all the components of the Jones vector of the object-wave front. We show that this method can be used to image and measure the distribution of the polarization state at the surface of a specimen, and the obtained results indicate that precise quantitative measurements of the polarization state can be achieved. An application of the method to image the birefringence of a stressed polymethyl methacrylate sample is presented.     

Evanescent-wave holography by use of surface-plasmon resonance

We report a method for evanescent-wave holography using surface-plasmon resonance from the illumination light. The device we have made consists of three layers: a prism of high refractive index, a thin metallic film, and a grating. Evanescent waves generated by the surface plasmons are diffracted with a prerecorded grating to reconstruct a three-dimensional image. The possibility of white-light illumination and the application to a flat display system with waveguides in the proposed method are discussed.     

Design of a high-numerical-aperture miniature microscope objective for an endoscopic fiber confocal reflectance microscope

An endoscopic confocal microscope requires a high-performance, miniaturized microscope objective. We present the design of a miniature water-immersion microscope objective that is approximately 10 times smaller in length than a typical commercial objective. The miniature objective is 7 mm in outer diameter and 21 mm in length (from object to image). It is used in a fiber confocal reflectance microscope. The miniature microscope objective has a numerical aperture of 1.0, a field of view of 250 microm, and a working distance of 450 microm. It delivers diffraction-limited performance at lambda = 1064 nm. Micrometer-level resolution has been experimentally demonstrated.     

High-resolution digital holography utilized by the subpixel sampling method

A novel (to our knowledge) approach for resolution improvement in digital holography is presented in this paper. The proposed method is based on recording the incoming interference field on a complementary metal-oxide semiconductor (CMOS) camera with subpixel resolution. The method takes advantage of the small pixel size of the CMOS sensor, while overcoming the reduced fill factor. This paper describes the experimental and numerical procedures. The improvement of the obtainable optical resolution, image quality, and phase measurement accuracy are demonstrated within this paper.     

Artificial adjustment of element stiffness with a particular reference to plate bending

A finite element may satisfy all convergence requirements and work well except for being too stiff or too flexible when the mesh is coarse. Here we discuss a technique for softening or stiffening such elements, provided that they have internal degrees-of-freedom. The technique is applied to a previously derived plate element, and the element is found to be much improved.