Mono-detection spatially super resolved microwave imaging for RADAR applications

In this paper we present a novel RF photonic approach to radar scanning and imaging. The operating principle is based upon a system in which several (in our case two) radiating microwave sources generate and project at far field, a moving grating pattern over an object, e.g. by linearly modifying the relative phase between the microwave sources. Capturing a set of such integrated reflections (we work only with a mono detector) coming from the object at different radio frequencies (due to a simultaneously performed spectral scanning) can spatially reconstruct high resolution image of the object despite the fact that the sensing was performed with a small mono receiving antenna.     

Evaluation of the echolocation model for range estimation of multiple closely spaced objects

Experimental evidence indicates that bats can use frequency-modulated echolocation to identify objects with an accuracy of less than 1 μs. However, when modeling this process, it is difficult to estimate the delay times of multiple closely spaced objects by analyzing the echo spectrum, because the sequence of delay separations cannot be determined without information on the temporal changes in the interference patterns of the echoes. To extract the temporal changes, Gaussian chirplets with a carrier frequency compatible with bat emission sweep rates are introduced. The delay time for object 1 (T(1)) is estimated from the echo spectrum around the onset time. The T(2) is obtained by adding the T(1) to the delay separation between objects 1 and 2. Further objects are located in sequence by this procedure. Here echoes were measured from single and multiple objects at a low signal-to-noise ratio. It was confirmed that the delay time for a single object could be estimated with an accuracy of about 1.3 μs. The range accuracy was less than 6 μs when the frequency bandwidth was less than 10 kHz. The delay time for multiple closely spaced objects could be estimated with a high range resolution by extracting the interference pattern.     

A new approach to synchrotron energy‐dispersive X‐ray diffraction computed tomography

A new data collection strategy for performing synchrotron energy‐dispersive X‐ray diffraction computed tomography has been devised. This method is analogous to angle‐dispersive X‐ray diffraction whose diffraction signal originates from a line formed by intersection of the incident X‐ray beam and the sample. Energy resolution is preserved by using a collimator which defines a small sampling voxel. This voxel is translated in a series of parallel straight lines covering the whole sample and the operation is repeated at different rotation angles, thus generating one diffraction pattern per translation and rotation step. The method has been tested by imaging a specially designed phantom object, devised to be a demanding validator for X‐ray diffraction imaging. The relative strengths and weaknesses of the method have been analysed with respect to the classic angle‐dispersive technique. The reconstruction accuracy of the method is good, although an absorption correction is required for lower energy diffraction because of the large path lengths involved. The spatial resolution is only limited to the width of the scanning beam owing to the novel collection strategy. The current temporal resolution is poor, with a scan taking several hours. The method is best suited to studying large objects (e.g. for engineering and materials science applications) because it does not suffer from diffraction peak broadening effects irrespective of the sample size, in contrast to the angle‐dispersive case.     

基于支撑矢量机的天体光谱自动分类方法

天体光谱自动识别系统的主要目标是对天体进行分类和参数测量。文章提出一种新的基于支撑矢量机的非活动天体与活动天体的自动分类方法。在信噪比低的时候 ,由于红移值未知使得噪声与发射谱线难于辨别 ,因此不能单纯依靠寻找发射谱线来确定是否为活动天体。据此 ,在低噪声情况下对非活动天体与活动天体的区分成为难点。本方法结合主分量分析法和支撑矢量机 ,能够对红移值未知的活动天体与非活动天体比较有效地进行自动光谱分类 ,对天文界的大型巡天计划中的海量观测数据自动处理有比较重要的应用价值。     

Three-dimensional object recognition from digital Fresnel hologram by wavelet matched filtering

We propose and demonstrate a digital holographic technique for 3D object recognition and classification. One Fresnel digital hologram of each of the 3D objects to be classified is recorded. The electronic holograms are processed digitally to retrieve 3D object information as 2D digital complex images. We use this method to classify four physical objects in a 3D scene into two classes. Results are presented from an experiment to demonstrate the proof of the concept.     

Occlusion removal technique for improved recognition of partially occluded 3D objects in computational integral imaging

In this paper, we propose an occlusion removal technique for improved recognition of 3D objects that are partially occluded in computational integral imaging (CII). In the reconstruction process of a 3D object which is partially occluded by other objects, occlusion degrades the resolution of reconstructed 3D images and thus this affects negatively the recognition of a 3D object in CII. To overcome this problem, we introduce a method to eliminate occluding objects in elemental image array (EIA) and the proposed method is applied to 3D object recognition by use of CII. To our best knowledge, this is the first time to remove occlusion in CII. In our method, we apply the elemental image to sub-image (ES) transform to EIA obtained by a pickup process and those sub-images are employed for occlusion removal. After the transformation, we correlate those sub-images with a reference sub-image to locate occluding objects and then we eliminate the objects. The inverse ES transform provides a modified EIA. Actually, the modified EIA is considered to be an EIA without the object that occludes the object to be reconstructed. This can provide a substantial gain in terms of the image quality of 3D objects and in terms of recognition performance. To verify the usefulness of the proposed technique, some experimental results are carried out and the results are presented.     

Temporal scales of auditory objects underlying birdsong vocal recognition

Vocal recognition is common among songbirds, and provides an excellent model system to study the perceptual and neurobiological mechanisms for processing natural vocal communication signals. Male European starlings, a species of songbird, learn to recognize the songs of multiple conspecific males by attending to stereotyped acoustic patterns, and these learned patterns elicit selective neuronal responses in auditory forebrain neurons. The present study investigates the perceptual grouping of spectrotemporal acoustic patterns in starling song at multiple temporal scales. The results show that permutations in sequencing of submotif acoustic features have significant effects on song recognition, and that these effects are specific to songs that comprise learned motifs. The observations suggest that (1) motifs form auditory objects embedded in a hierarchy of acoustic patterns, (2) that object-based song perception emerges without explicit reinforcement, and (3) that multiple temporal scales within the acoustic pattern hierarchy convey information about the individual identity of the singer. The authors discuss the results in the context of auditory object formation and talker recognition.     

图像中近圆形对象的一种识别方法

介绍了一种利用多特征联合概率的红外图像中近圆形对象检测方法,通过计算图像中诸多小段曲线的弯拱方向来获得图像中各处存在圆的概率,并用梯度强度对这些概率进行加权,再结合对象内部为空洞的概率,共同形成对图像中近圆形对象所在位置的一个判决。经与经典的Hough变换法相比较,表现出一定的优越性。对一组不同特征的红外图像进行测试实验,均能检测出近圆形对象,表现出一定的适应性,对某些应用场景中的目标检测与识别有辅助价值。     

High-speed three-dimensional shape measurements of objects with laser speckles and acousto-optical deflection

Many three-dimensional (3D) shape measurement techniques in stereophotogrammetry with temporal coded structured illumination are limited to static scenes because the time for measurement is too long in comparison to the object speed. The measurement of moving objects result in erroneous reconstructions. This is apparent to reduce measurement time to overcome this limitation, which is often done by increasing the projection rate for illumination while shrinking the amount of images taken for reconstruction. The projection rate limits most applications in its speed because digital light processing (DLP) projectors, which are widely used, bring a limited projection rate along. Our approach, in contrast, does not take a DLP. Instead we use laser speckles as projected patterns which are switched using an acousto-optical deflector. The projection rate is 10× higher than what the fastest stripe projection systems to our knowledge achieve. Hence, we present this uncommon but potential approach for highspeed (≈250 3Dfps= [3D measurements per second]), dense, and accurate 3D measurements of spatially separated objects and show the media that emphasizes the ability of accurate measurements while the objects under testing move.     

Determination of the size of a radiation source by the method of calculation of diffraction patterns

In traditional X-ray radiography, which has been used for various purposes since the discovery of X-ray radiation, the shadow image of an object under study is constructed based on the difference in the absorption of the X-ray radiation by different parts of the object. The main method that ensures a high spatial resolution is the method of point projection X-ray radiography, i.e., radiography from a point and bright radiation source. For projection radiography, the small size of the source is the most important characteristic of the source, which mainly determines the spatial resolution of the method. In this work, as a point source of soft X-ray radiation for radiography with a high spatial and temporal resolution, radiation from a hot spot of X-pinches is used. The size of the radiation source in different setups and configurations can be different. For four different high-current generators, we have calculated the sizes of sources of soft X-ray radiation from X-ray patterns of corresponding objects using Fresnel-Kirchhoff integrals. Our calculations show that the size of the source is in the range 0.7–2.8 μm. The method of the determination of the size of a radiation source from calculations of Fresnel-Kirchhoff integrals makes it possible to determine the size with an accuracy that exceeds the diffraction limit, which frequently restricts the resolution of standard methods.     

Recognition of a light line pattern by Hu moments for 3-D reconstruction of a rotated object

A simple technique of a light line projection for 3-D shape detection of rotated objects is presented. In this technique, an object is rotated around its symmetrical axis four times at an angle by using an electromechanical device and scanned by a light line. Four views of the object surface are extracted from each one of these rotations by processing a set of light line images. These views are connected using rotation angle and origin coordinates to obtain the complete 3-D shape. Angle and origin are calculated by recognition of a light line pattern. Light line pattern is recognized by Hu moments. In this manner, measurement errors on setup are avoided. It is an advantage over common methods, where these two parameters are measured directly on the setup to obtain the 3-D shape. Local profilometric method is based on the perturbation that the light line suffers when it is projected on the object surface. This perturbation is observed on an image plane due to the different direction between light line projector and viewer. These perturbations are measured by using Gaussian functions. In this technique the light line images are processed in very fast form. The technique and processing time are presented in detail. This technique is tested with objects, which have little information and its experimental results are also presented.     

Light scattering from mesoscopic objects in diffusive media

No direct imaging is possible in turbid media, where light propagates diffusively over length scales larger than the mean free path .The diffuse intensity is, however, sensitive to the presence of any kind of object embedded in the medium, e.g. obstacles or defects. The long-ranged effects of isolated objects in an otherwise homogeneous, non-absorbing medium can be described by a stationary diffusion equation. In analogy with electrostatics, the influence of a single embedded object on the intensity field is parametrized in terms of a multipole expansion. An absorbing object is chiefly characterized by a negative charge, while the leading effect of a non-absorbing object is due to its dipole moment. The associated intrinsic characteristics of the object are its capacitance Q or its effective radius ,and its polarizability P. These quantities can be evaluated within the diffusion approximation for large enough objects. The situation of mesoscopic objects, with a size comparable to the mean free path, requires a more careful treatment, for which the appropriate framework is provided by radiative transfer theory. This formalism is worked out in detail, in the case of spherical and cylindrical objects of radius R, of the following kinds: (i) totally absorbing (black), (ii) transparent, (iii) totally reflecting. The capacitance, effective radius, and polarizability of these objects differ from the predictions of the diffusion approximation by a size factor, which only depends on the ratio .The analytic form of the size factors is derived for small and large objects, while accurate numerical results are obtained for objects of intermediate size .For cases (i) and (ii) the size factor is smaller than one and monotonically increasing with ,while for case (iii) it is larger than one and decreasing with . Received: 7 August 1998 / Accepted: 3 September 1998     

Longitudinal-differential interferometry: direct imaging of axial superluminal phase propagation

We introduce and demonstrate a new interferometric method called longitudinal-differential (LD) interferometry, which measures the spatially resolved phase difference of the scattered field by an object relative to the illumination. This method is combined with a high-resolution interference microscope that allows recording three-dimensional field distributions in amplitude and phase. The method is applied to study the axial phase behavior of Arago spots, an effect observable in low-Fresnel-number systems behind objects with a size comparable to the wavelength. We directly observe the initial phase delay in the Arago spot and prove that the local phase velocity exceeds the speed of light in air. Such LD phase studies are applicable not only to the Arago spot but also to other kinds of light interactions with wavelength-scale objects, e.g., photonic nanojets.     

Frequency-multiplexed profilometric phase coding for three-dimensional object recognition without 2pi pi phase ambiguity

A novel phase-coding technique based on Fourier-transform profilometry (FTP) is proposed for three-dimensional object recognition. Two spatially multiplexed grating patterns of different spatial frequencies are projected simultaneously onto the objects-target, and the phase changes in the distorted patterns are detected. An algebraic addition or subtraction of these phase values is utilized to code the two-dimensional plans of the objects-target with spatial harmonic modulations. The phase-coded plans of the objects and the target are cross correlated digitally to yield a high correlation peak at the target location. The 2pi ambiguity of the phase associated with FTP has been resolved in correlation results without recourse to phase unwrapping. Experimental results show an excellent discrimination capability for target recognition.     

Three-dimensional-object recognition by use of single-exposure on-axis digital holography

On-axis phase-shifting digital holography requires recording of multiple holograms. We describe a novel real-time three-dimensional- (3-D-) object recognition system that uses single-exposure on-axis digital holography. In contrast to 3-D-object recognition by means of a conventional phase-shifting scheme that requires multiple exposures, our proposed method requires only a single digital hologram to be synthesized and used to recognize 3-D objects. A benefit of the proposed 3-D recognition method is enhanced practicality of digital holography for 3-D recognition in terms of its simplicity and greater robustness to external scene parameters such as moving targets and environmental noise factors. We show experimentally the utility of the single-exposure on-axis digital holography-based 3-D-object recognition method.     

基于螺旋相位调制的非相干全息点扩散函数研究

分析了菲涅耳非相干相关全息(Fresnel incoherent correlation holography,FINCH)系统中纯相位空间光调制器(spatial light modulator,SLM)加载螺旋相位掩模时的点扩散函数.以氙灯为照明光源搭建了FINCH系统,电荷耦合器记录的点源全息图与点扩散函数模拟结果一致.采用该系统分别在SLM上加载双透镜掩模和螺旋相位调制双透镜掩模两种情况下对分辨率板和非染色洋葱细胞成像,给出了成像对比结果.结果表明:采用螺旋相位调制的FINCH系统可以在几乎不牺牲分辨率的情况下提高图像的边缘对比度;同样,对相位物体也可以实现图像的边缘提取和识别.该方法在实时监测活细胞的分裂、形变等方面具有重要应用前景.     

Scale invariant recognition in optical correlators using prior estimation of object size

A new perspective of scale-invariant pattern recognition is proposed in this paper. Instead of computing a filter from one of many orthogonal components of the reference object, the scaling factor is estimated from the Fourier spectrums of reference and test images and utilized in rescaling of the spectrum. The test image is correlated with the reference image after rescaling its Fourier spectrum with classical matched filtering. Computer simulation results are presented for a reference object at several scaling versions as well as some non-target objects.     

Display of tilt information of vibrating object in time average mode using lateral shearing interferometry and interferometric grating

We have experimentally demonstrated vibration analysis of a reflecting object in time-average mode using shearing interferometry and interferometric grating. Experimental results show that time-average moiré fringes, formed between fringe pattern reflected from object and sinusoidal grating are modulated spatially by the amplitude of vibrating tilt. From the experimental results, information regarding tilt of vibrating objects can be determined.     

基于Raman光谱和支持向量机回归的古井贡酒年份鉴别方法

白酒年份的快速准确鉴定是白酒品质分析的重点和难点问题之一。实现白酒年份酒的快速、准确的鉴别,对促进白酒行业的健康发展、维护消费者的合法权益具有重要意义。光谱分析法结合模式识别技术是实现白酒品质快速鉴别的首选方法之一,而Raman光谱由于其受水的影响很小且很少或不需要样品前处理,在白酒分析中具有广阔的发展空间。因此,采用Raman光谱和支持向量机回归(SVR)建立数据分析模型,用于不同年份白酒的年份鉴定和同一年份不同贮存时间的白酒年份鉴定。该研究创新之处主要包括如下三个方面：(1)应用Raman光谱对白酒品质进行分析,在分析方法的应用上具有一定的创新之处。(2)研究白酒的年份鉴定问题,在研究对象的选择上,具有一定的创新之处。(3)建立基于回归框架的白酒年份与年份指数对应关系,实现白酒年份识别及预测,不仅可以有效鉴别白酒年份,同时可用于鉴别白酒贮存时间,因此,在分析方法的确定和应用上,具有一定的创新之处。实验中采用古井贡5年、8年、16年及26年系列年份酒进行了实证分析,数据分析实验结果表明,所建立的基于Raman光谱和SVR的白酒年份鉴别分析流程和方法,对鉴别不同年份的白酒,以及同一年份不同贮存时间的白酒样品(包括对数据库内已有样本年份的鉴别,以及对数据库内没有的盲样的年份预测),均取得较好的应用效果,相比于其他常用回归分析方法具有明显的优越性,可以为白酒年份酒分析提供一定的技术支持。