Real-time joint transform correlation with photoanisotropic dye-polymer films

The results of joint transform correlation with photoanisotropic organic materials are presented. The materials' dynamic holographic recording capability and high resolution permit the operation of such a correlator in real time. Both theoretical and experimental results show that the photoanisotropic properties cause a dependence of the correlation output on the state of the polarization of the readout beam and can be used to produce an output polarization orthogonal to the input, which permits polarization filtering to be used, greatly increasing the signal-to-noise ratio. The effect of the saturation of the nonlinearity on correlation performance is investigated and is shown to be able to improve correlator recognition and discrimination. The correlation results of binary images and of a highresolution synthetic-aperture radar image are presented, demonstrating excellent optical quality, nonlinear edge enhancement, and real-time operation.     

Scale-invariant recognition of three-dimensional objects by use of a quasi-correlator

A method of scale-invariant recognition of three-dimensional (3-D) objects is presented. Several images of the observed scene are recorded under white-light illumination from several different points of view and compressed into a single complex two-dimensional matrix. After filtering with a single scale-invariant filter, the resultant function is then coded into a computer-generated hologram (CGH). When this CGH is coherently illuminated, a correlation space is reconstructed in which light peaks indicate the existence and location of true targets in the tested 3-D scene. The light peaks are detectable for different sizes of the true objects, as long as they are within the invariance range of the filter. Experimental results in a complete electro-optical system are presented, and comparisons with other systems are investigated by use of computer simulation.     

Rotation-invariant optical recognition of three-dimensional objects

An automatic method for rotation-invariant three-dimensional (3-D) object recognition is proposed. The method is based on the use of 3-D information contained in the deformed fringe pattern obtained when a grating is projected onto an object's surface. The proposed method was optically implemented by means of a two-cycle joint transform correlator. The rotation invariance is achieved by means of encoding with the fringe pattern a single component of the circular-harmonic expansion derived from the target. Thus the method is invariant for rotations around the line of sight. The whole experimental setup can be constructed with simple equipment. Experimental results show the utility of the proposed method.     

Optical image recognition of three-dimensional objects

A three-dimensional (3-D) optical image-recognition technique is proposed and studied. The proposed technique is based on two-pupil optical heterodyne scanning and is capable of performing 3-D image recognition. A hologram of the 3-D reference object is first created and then is used to modulate spatially one of the pupils of the optical system; the other pupil is a point source. A 3-D target object to be recognized is then scanned in two dimensions by optical beams modulated by the two pupils. The result of the two-dimensional scan pattern effectively displays the correlation of the holographic information of the 3-D reference object and that of the 3-D target object. A strong correlation peak results if the two pieces of the holographic information are matched. We analyze the proposed technique and thereby lay a theoretical foundation for optical implementations of the idea. Finally, computer simulations are performed to verify the proposed idea.     

Robotic tactile recognition of pseudorandom encoded objects

This paper discusses an original model-based method for blind robotic tactile recognition of three-dimensional objects. Conveniently shaped geometric symbols representing terms of a pseudorandom array (PRA) are embossed on object surfaces. Symbols recovered by tactile probing are recognized using a neural network and then clustered in a PRA window that contains enough information to fully identify the absolute coordinates of the recovered window within the encoding PRA. By knowing how different object models were mapped to the PRA, it is possible to unambiguously identify the object face and the exact position of the recovered symbols on the face.     

Real-time detection of multiple moving objects in complex image sequences

In this article, a real-time multistage method for detecting multiple objects moving in real scenes is presented. At the first level, a rough focus-of-attention mechanism is used to individuate areas of the input image that show remarkable differences with a real-time updated background image. Binary statistical morphology (BMS) operators are applied to individuate image pixels, which can be associated with real objects moving into the scene. High stability to noise is obtained by tuning the smoothing effects of the BSM operators according to the noise level present in the original image sequence. Then, at the second level, a composition of BSM is applied to eliminate isolated points and to favor dense agglomerate of changed pixels, i.e., blobs. The last level attempts to describe changes in terms of motion of blobs by allowing blobs to merge, split, appear, and vanish. A blob-matching procedure is used for tracking blobs over consecutive frames. Experimental results on real scenes, which demonstrate the advantages of the proposed method with respect to existing change detection methods, are given. © 1999 John Wiley & Sons, Inc. Int J Imaging Syst Technol 10, 305–317, 1999     

Real-time interaction of virtual and physical objects in mixed reality applications

We present a real-time method for computing the mechanical interaction between real and virtual objects in an augmented reality environment. Using model order reduction methods we are able to estimate the physical behavior of deformable objects in real time, with the precision of a high-fidelity solver but working at the speed of a video sequence. We merge tools of machine learning, computer vision, and computer graphics in a single application to describe the behavior of deformable virtual objects allowing the user to interact with them in a natural way. Three examples are provided to test the performance of the method.     

Real-time three-dimensional object recognition with multiple perspectives imaging

A novel system for recognizing three-dimensional (3D) objects by use of multiple perspectives imaging is proposed. A 3D object under incoherent illumination is projected into an array of two-dimensional (2D) elemental images by use of a microlens array. Each elemental 2D image corresponds to a different perspective of the 3D object. Multiple perspectives imaging based on integral photography has been used for 3D display. In this way, the whole set of 2D elemental images records 3D information about the input object. After an optical incoherent-to-coherent conversion, an optical processor is employed to perform the correlation between the input and the reference 3D objects. Use of micro-optics allows us to process the 3D information in real time and with a compact optical system. To the best of our knowledge this 3D processor is the first to apply the principle of integral photography to 3D image recognition. We present experimental results obtained with both a digital and an optical implementation of the system. We also show that the system can recognize a slightly out-of-plane rotated 3D object.     

结合颜色和形态特征的杂草实时识别方法

利用计算机视觉技术将杂草从农作物和土壤中区别开来已成为精细农业领域研究的热点问题。提出了一种颜色和形态特征相结合的杂草实时识别方法。在YcbCr颜色模型中,以色差Cr为特征量、以最大类间方差作为GA的适应度函数对Cr进行自适应阈值分割将植物与背景分离;利用植物的形态特征,结合形态学腐蚀、膨胀方法及差影法将农作物和杂草分离。多幅杂草图像研究结果表明:该算法杂草正确识别率大于83.1%,处理一幅640像素×480像素的图像平均只需38ms,识别速度满足25帧/秒的实时性要求。     

Shift- and scale-invariant recognition of contour objects with logarithmic radial harmonic filters

The phase-only logarithmic radial harmonic (LRH) filter has been shown to be suitable for scale-invariant block object recognition. However, an important set of objects is the collection of contour functions that results from a digital edge extraction of the original block objects. These contour functions have a constant width that is independent of the scale of the original object. Therefore, since the energy of the contour objects decreases more slowly with the scale factor than does the energy of the block objects, the phase-only LRH filter has difficulties in the recognition tasks when these contour objects are used. We propose a modified LRH filter that permits the realization of a shift- and scale-invariant optical recognition of contour objects. The modified LRH filter is a complex filter that compensates the energy variation resulting from the scaling of contour objects. Optical results validate the theory and show the utility of the newly proposed method.     

Design of correlation filters for recognition of linearly distorted objects in linearly degraded scenes

Generalized correlation filters are proposed to improve recognition of a linearly distorted object embedded in a nonoverlapping background when the input scene is degraded with a linear system and additive noise. Several performance criteria defined for the nonoverlapping signal model are used for the design of filters. The derived filters take into account information about an object to be recognized, disjoint background, noise, and linear degradations of the target and the input scene. Computer simulation results obtained with the proposed filters are discussed and compared with those of various correlation filters in terms of discrimination capability, location errors, and tolerance to input noise.     

Coupled-wave analysis of vector holograms. 2. Reflective gratings formed in photoanisotropic medium with uniaxial birefringence

The diffraction properties of reflective anisotropic gratings, which can be recorded in photoanisotropic media with uniaxial birefringence by three-dimensional vector holography, were characterized through the use of coupled-wave analysis (CWA). By investigating the perturbation of the dielectric tensor, we demonstrated that the gratings with sinusoidal distribution of the azimuthal angle of the optic axis diffract polarized light in which the ordinary and extraordinary components are converted for incident light. The polarization conversion was consistent with that calculated by a numerical method. In addition, it was shown that CWA enables highly accurate calculation of the diffraction efficiency with wavelength dispersion when the amplitude of the azimuthal angle is small.     

Measurement of phase objects by simple means

A printed fringe pattern is imaged by a CCD camera, whereas a phase object is placed in the ray path for imaging. The ray deflections distort the image of the pattern and are measured by evaluation of the image with the Fourier transform method.     

Scattering of singular beams by subwavelength objects

In recent years, there has been a mounting interest in better methods of measuring nanoscale objects, especially in fields such as nanotechnology, biomedicine, cleantech, and microelectronics. Conventional methods have proved insufficient, due to the classical diffraction limit or slow and complicated measuring procedures. The purpose of this paper is to explore the special characteristics of singular beams with respect to the investigation of subwavelength objects. Singular beams are light beams that contain one or more singularities in their physical parameters, such as phase or polarization. We focus on the three-dimensional interaction between electromagnetic waves and subwavelength objects to extract information about the object from the scattered light patterns.     

Differential theory of diffraction by finite cylindrical objects

We present a differential theory for solving Maxwell equations in cylindrical coordinates, projecting them onto a Fourier-Bessel basis. Numerical calculations require the truncation of that basis, so that correct rules of factorization have to be used. The convergence of the method is studied for different cases of dielectric and metallic cylinders of finite length. Applications of such a method are presented, with a special emphasis on the near-field map inside a hole pierced in a plane metallic film.     

Real-time PCR measurement by fluorescence anisotropy

We have developed an instrument for monitoring real-time PCR using fluorescence anisotropy, enabling an assay chemistry in which the fluorescence from a labeled primer elucidates amplification. The instrument holds the sample temperature constant to within +/-0.03 degrees C during measurement in the extension phase of each PCR cycle and achieves 0.116 mP FA resolution. Primer conjugation with Alexa-Fluor 488, when compared with other fluorophores, is shown to provide the greatest FA range between primer and product. Comparable reproducibility and linearity of the crossing point for a range of target copy numbers is observed between the FA-based assay run in our instrument and the SYBR green assay run in commercial instrumentation. Reproducibility is also consistent with Poisson-distributed experimental error in aliquoting starting copies, a theoretical limit to instrument/assay performance.