Visibility enhancement in two-dimensional lensless ghost imaging with true thermal light

We report an experimental demonstration of two-dimensional(2D) lensless ghost imaging with true thermal light. An electrodeless discharge lamp with a higher light intensity than the hollow cathode lamp used before is employed as a light source. The main problem encountered by the 2D lensless ghost imaging with true thermal light is that its coherence time is much shorter than the resolution time of the detection system. To overcome this difficulty we derive a method based on the relationship between the true and measured values of the second-order optical intensity correlation, by which means the visibility of the ghost image can be dramatically enhanced. This method would also be suitable for ghost imaging with natural sunlight.     

Nakagami-m parametric imaging for characterization of thermal coagulation and cavitation erosion induced by HIFU

Nowadays, both thermal and mechanical ablation techniques of HIFU associated with cavitation have been developed for noninvasive treatment. A specific challenge for the successful clinical implementation of HIFU is to achieve real-time imaging for the evaluation and determination of therapy outcomes such as necrosis or homogenization. Ultrasound Nakagami-m parametric imaging highlights the degrading shadowing effects of bubbles and can be used for tissue characterization. The aim of this study is to investigate the performance of Nakagami-m parametric imaging for evaluating and differentiating thermal coagulation and cavitation erosion induced by HIFU. Lesions were induced in basic bovine serum albumin (BSA) phantoms and ex vivo porcine livers using a 1.6 MHz single-element transducer. Thermal and mechanical lesions induced by two types of HIFU sequences respectively were evaluated using Nakagami-m parametric imaging and ultrasound B-mode imaging. The lesion sizes estimated using Nakagami-m parametric imaging technique were all closer to the actual sizes than those of B-mode imaging. The p-value obtained from the t-test between the mean m values of thermal coagulation and cavitation erosion was smaller than 0.05, demonstrating that the m values of thermal lesions were significantly different from that of mechanical lesions, which was confirmed by ex vivo experiments and histologic examination showed that different changes result from HIFU exposure, one of tissue dehydration resulting from the thermal effect, and the other of tissue homogenate resulting from mechanical effect. This study demonstrated that Nakagami-m parametric imaging is a potential real-time imaging technique for evaluating and differentiating thermal coagulation and cavitation erosion.     

DMLS 2011: Fourth International Workshop on Diamonds for Modern Light Sources

The fourth in a series of workshops devoted to the use of diamonds at synchrotrons and free electron lasers (FELs) was held on May 5-6, 2011, at the Advanced Photon Source. The previous DMSL workshop was held in Japan in 2008. The workshop was supported in part by Argonne National Laboratory; Applied Diamond, Inc.; SINMAT, Inc.; and elementsix, Ltd. The scope was to assess : 1) the status, size, quality, and availability of synthetic type IIa diamonds; 2) the status of CVD diamonds; 3) applications for beamline optics; 4) applications for beam position monitors (BPMs) and detectors; 5) applications at FELs; and 6) novel applications, such as for an X-ray free electron laser oscillator (XFELO). On May 5, Linda Young (APS/XSD) gave the workshop welcome. There were three sessions on each of the two days. A website was created and will be kept live where the detailed age-nda and list of speakers will remain available (http://www.aps.anl.gov/News/Conferences/2011/DMLS). As part of the session on BPMs and detectors, there were several speakers from outside the light source community, which demonstrated that there is a larger science audience for these applications than just light sources. Highlights of the workshop include: 1) reports of supplier facilities for thinning and polishing; 2) reports on tests of supplier-provided bonds to CVD cooling manifolds; 3) a report of more than 99% reflectivity from diamond for hard X-rays, significant for XFELO feasibility, measured at the APS; 4) a report on thermal expansion measurements at low temperatures made at the APS (no negative thermal expansion, thermal expansion below 1e-9); 5) a report from Brookhaven National Laboratory on substantial progress in diamond beam flux monitors (BPMs), and fast detectors; 6) a presentation on plans for a self-seeding at LCLS with diamond crystals. A synopsis of each technical session follows below.     

Visualising impregnated chitosan in Pinus radiata early wood cells using light and scanning electron microscopy

Chitosan, a deacetylated product of an abundant naturally occurring biopolymer chitin, has been used in a range of applications, particularly in food and health areas, as an antimicrobial agent. In the work reported here Pinus radiata wood was impregnated with chitosan as an environmentally compatible organic biocide (Eikenes et al., 2005a, Eikenes et al., 2005b) to protect wood against wood deteriorating microorganisms and to thus prolong the service life of wooden products. We developed sample preparation techniques targeted to visualise impregnated chitosan within wood tissues using light microscope and field-emission scanning electron microscope (FE-SEM). Sections were viewed with the light microscope without staining with a dye as well as after staining with the dye toluidine blue. Light microscopy was also undertaken on sections that had been stained with 1% aqueous osmium tetroxide (OsO₄). For SEM observations, the sections were treated with OsO₄ and then examined with the FE-SEM, first in the secondary electron imaging mode (SEI) and then in the backscattered electron imaging (BEI) mode, imaging the same areas of a section in both SEI and BEI modes. The preparation techniques employed and the combined use of light and scanning electron microscopy provided valuable complementary information, revealing that chitosan had penetrated into the cavities (cell lumens, intercellular spaces) of all sizes present within wood tissues and had also impregnated early wood cell walls. The information obtained is discussed in relation to its importance in further development of chitosan formulations and refinement of impregnation technologies to optimise chitosan impregnation into and distribution within wood tissues as well as in assessing chitosan efficacy.     

基于统计光学的正负热光非定域成像

本文, 基于经典统计光学, 建立符合热光特性的统计模型, 通过数值模拟证明了吴令安和Meyers提出的图像重构算法, 并进行了定性的理论分析. 在关联成像获得的数据样本中, 根据桶探测器的光强涨落进行分组, 分别以某个阈值作为下限和上限, 再将分组后的独立样本和相应的面探测器信号进行强度关联, 则可以得到物体的正像或负像. 然而, 不经过关联运算, 直接对分组后的面探测器信号进行算数平均也可以得到物体的正像或负像, 同时成像的对比度得到较大提高. 这种分组对应的非定域成像进一步说明强度涨落在热光成像中的重要性. 最后以字符掩膜版作为成像物体, 分别运用关联成像和分组对应正负成像算法重构物体的图像, 实验结果证明这种新的正负算法可以提高非定域成像的对比度. 关键词： 统计光学 热光 关联成像 正负非定域成像     

Effect of wavefront error on 10(-7) contrast measurements

Received October 11, 2005; accepted November 10, 2005; posted December 2, 2005 (Doc. ID 65234) We have measured a contrast of 6.5 x 10(-8) from 10 to 25 lambda/D in visible light on the Extreme Adaptive Optics testbed, using a shaped pupil for diffraction suppression. The testbed was designed with a minimal number of high-quality optics to ensure low wavefront error and uses a phase-shifting diffraction interferometer for metrology. This level of contrast is within the regime needed for imaging young Jupiter-like planets, a primary application of high-contrast imaging. We have concluded that wavefront error, not pupil quality, is the limiting error source for improved contrast in our system.     

日光强度涨落自关联消湍流成像

从关联成像理论出发,提出了日光场在实际大气湍流环境中强度点对点自关联成像理论,并进行了实验验证,分析了太阳光强度二阶自关联成像和强度点对点二阶自关联成像的区别.研究结果表明,太阳光场的点对点四阶自关联,即强度的二阶点对点自关联,可实现消大气湍流成像.为验证理论有效性,利用外场实验进行了验证,获得优于17 km距离的消湍流成像结果.理论和实验均表明,太阳光强度涨落的点对点自关联可实现消大气湍流成像.相比于相机直接成像,本文成像方法消除了大气湍流影响,同时该方案极大提升了关联成像技术的实用性,可直接用于远距离消大气湍流的高质量成像,增加图像识别率.理论表明,任何成像过程中波前受相位扰动影响的波段,如红外、紫外等,均可利用本文方法消除影响,成果具有较大实用价值.     

Effects of light intensity on reflective ghost imaging

In this letter, we analyze the effects of light intensity find that the brightness of reflective ghost image can on reflective ghost imaging with thermal source. We be changed by modulating the light intensity of the source and the splitting ratio of the beam splitter. The signal-to-noise ratio will be improved by increa.sing the light intensity of the source. More important, we can obtain the reflective ghost image with high image quality by adopting a low light intensity signal beam and a high light intensity reference beam, which is better than the classical optical imaging, because it can reduce the effects of light on the object.     

The impact of light polarization on imaging visibility of Nth-order intensity correlation with thermal light

The relationship between the imaging visibility of arbitrary Nth-order intensity correlation with thermal light and light’s degree of polarization is investigated. It is shown that for the same order correlation, the value of visibility with partially polarized light is greater than that with natural light but smaller than that with completely polarized light, and the visibility in all three cases is remarkably enhanced as N increases.     

Infrared workshop held at the SRC

The 2005 Advanced Photon Source (APS) User Meeting commemorated the tenth anniversary of first light at the APS. The weeklong meeting, with more than 600 participants, was held May 2–5, 2005, in collaboration with the new Center for Nanoscale Materials (CNM). The CNM, sited adjacent to the APS experiment hall, is currently under construction. Monday's session concentrated on CNM activities. Business and science sessions on Wednesday and Thursday morning highlighted the APS. Nine workshops related to CNM and APS science filled the schedule on Tuesday, Thursday afternoon, and Friday.     

Broadband emission of dye mixtures in films and polymer matrices

Emission of mixtures of organic compounds in thin acrylic films and matrices is investigated from the blue to red range of the spectrum. The present paper is aimed at studying the feasibility of obtaining white light by conversion of output diode radiation (379 nm) using a mixture of fluorophors. It is demonstrated that the emission band shape depends on ratios of dye concentrations and geometry of excitation and registration that must be taken into account in the development of devices based on these compounds.__________This revised version was published online in May 2005 with a correction on affiliation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 67–70, November, 2004.     

Resonances in a Microstrip System with an Iris and a Short-Circuit Plunger

We reveal resonant reflection in a microstrip system with an iris and a short-circuit plunger for distances between the iris and the plunger that are much less than the wavelength in the transmission line. It is shown that the studied system can be used for design of novel microwave devices, including semiconductor ones, with controllable characteristics and decreased sizes. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 5, pp. 402–405, May 2005.     

Interaction of Nitrogen Oxide and Carbon Molecules Adsorbed on Ni Clusters Formed on the MgO(111) Thin Film Surface

The joint adsorption of CO and NO molecules on the surface of nanodimensional nickel clusters formed on the Mo(110) face of a thin MgO(111) magnesium oxide film under conditions of ultrahigh vacuum is investigated by methods of infrared reflection and thermal desorption spectroscopy. It is revealed that the adsorption of the NO molecules changes significantly the state of the adsorbed CO molecules. Based on an analysis of thermal desorption and IR spectra, a conclusion can be drawn that the adsorption of the NO molecules stimulates the migration of the CO molecules from the metal cluster surface to the boundary between the cluster and oxide accompanied by a decrease in the tilt angle of the molecular axis to the surface. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 85–89, May, 2005.     

Experimental study on the imaging of the squeezed state light at 1064 nm

Stable, low noise, infrared squeezed state tight at 1064 nm is generated by utilizing optical parametric down-conversion (OPDC) technique based on periodically poled KTiOPO₄ in a optical parametric amplifier (OPA) resonator. A non-classical noise reduction of 2.58 dB below the shot noise is observed through balanced homodyne detection. The squeezed state light is used to set up an imaging system for high-resolution imaging, and it is found that the resolution of image based on the amplitude-squeezed light is 1.26 times larger than that of infrared coherent light under the same intensity. The experimental results indicate that squeezed light is an important non-classical light, which can overcome the coherent laser shot-noise, the classical diffraction limit and limit of quantum noise.     

From entropy and jet quenching to deconfinement?

The challenge of demonstrating that the matter produced in heavy ion collisions is a deconfined quark-gluon plasma, as predicted by lattice QCD calculations, is the challenge of measuring the number of thermodynamic degrees of freedom at the time t₀ at which the matter comes into approximate local thermal equilibrium and begins to behave like a hydrodynamic fluid. Data from experiments done at the Relativistic Heavy Ion Collider have been used to estimate t₀ and to put a lower bound on the energy density . However, measuring has seemed out of reach, because no current data serve even as qualitative proxies for the temperature T(t₀). We point out that may equally appropriately be defined via , where s is the entropy density, which can be estimated from the measured final state entropy. This estimate is based on the testable assumption of an isentropic expansion. The observation of jet quenching has the potential to provide an upper bound on the energy density at early times. Our goal is to motivate such an analysis by pointing out that it would set a lower bound on .Received: 18 February 2005, Revised: 14 April 2005, Published online: 31 May 2005     

光读出热成像焦平面阵列的光学与热学设计

针对提出的一种光读出热成像系统 ,对其焦平面阵列的光学和热学特性进行了详细的分析 ,主要涉及法布里珀罗微腔两个反射面的反射率、可动微镜的温度响应、噪声等效温差以及响应时间四个方面。理论分析表明 :当法布里珀罗微腔两个反射面的反射率为 0 .5时 ,能获得较大的输出反射光强和反衬度 ,并保证了输出反射光强尽可能地随微镜位移在 0～λ/ 4范围内呈线性变化 ;可动微镜的温度响应值可达 2 .0 5× 10 -4,噪声等效温差为19.5mK ,热响应时间为 1.5 4× 10 -3 s。     

基于渥拉斯顿棱镜的单路实时偏振成像系统设计

针对非实时成像中动态场景偏振探测产生的虚假偏振信息问题,充分利用渥拉斯顿棱镜的分光特性,设计了一种新型实时偏振成像系统.采用像方远心望远透镜系统、准直透镜系统并设计匹配的成像镜系统,在单探测器阵列上同时获取偏振态相互垂直的两幅偏振图像.通过全系统联动设计与优化,系统的调制传递函数在截止频率处不小于0.55,全系统弥散斑均方根半径小于5.3μm,即小于探测器像元尺寸,满足成像设计要求.仿真结果证明该成像系统可有效解决传统分振幅偏振成像系统的实时性差的不足,分孔径偏振成像系统的能量利用率和分辨率低的问题以及偏振焦平面方法中光路串扰的缺陷,应用前景广阔.     

基于稀疏阵赝热光系统的强度关联成像研究

强度关联成像在近几年取得很大的突破,其应用价值越来越明显。以随机涨落的热光作为光源是强度关联成像的前提。目前常使用激光穿过旋转的毛玻璃产生赝热光。鉴于使用毛玻璃产生赝热光的局限性,提出了使用稀疏阵独立子光源产生赝热光,并在这种光源结构下讨论了基于线性关联算法的强度关联成像和基于稀疏约束非线性算法的强度关联成像的异同。     

混合仿生鱼眼-复眼的广角高清成像系统

基于多尺度成像理论,采用混合仿生鱼眼-复眼结构,实现了大视场兼具高分辨率的光学成像系统设计。前级物镜系统为大直径球透镜,收集广角目标光线并成像到与球透镜同心的球面中继像面上;次级目镜系统是关于球透镜中心球对称的小口径透镜组阵列,对中继像进行像差校正并成像到探测器阵列上。对比了物镜采用双层同心球和单个球透镜的成像性能,后者可获得更优的成像性能且避免了双胶合球透镜带来的公差控制及力学与热稳定性问题。整个成像系统的视场大于100°,全视场内角分辨率优于10″,而畸变小于5%;系统具有大景深特点,不需调焦即可同时对300 m到无穷远目标清晰成像,可广泛应用于侦查监控等领域。     

Probability theory of intensity correlation in ghost imaging with thermal light

To well reveal the imaging mechanism of ghost imaging (GI) with thermal light, we propose a probability theory using more general assumptions than existing theoretical explanations that the reference patterns obey an arbitrary identical distribution and the objects are of grayscale. It is not limited to a specific correlation function, even multi-functional variants of reference patterns can be used in correlation calculation. We have proven in both theory and experiments that the reconstruction means are linear transformations of original object's gray values and the probabilities of recovered pixel values in the pixel region of the same original gray value follow a Gaussian distribution, whose variance explains the appearance of reconstruction noise. We also derive the relationship between pattern variance and contrast-to-noise ratio under noisy conditions, which will be instructive for better pattern construction. This work will deepen the understanding of GI and enrich intensity correlation forms.