Range measurement from defocus gradient

Images taken of 3D objects are generally defocused. Depth-from-focus techniques use the defocus information to determine range. However, quantitative measurement of focus is difficult and requires accurate modeling of the point-spread function (PSF). We describe a new method that determines depth using the symmetry and smoothness of focus gradient with respect to the focus position. The technique is passive and uses a monocular imaging system. The performance for estimating range is experimentally demonstrated.     

Defect identification on specular machined surfaces

In many industrial applications, it is important to identify defects on specular surfaces. On machined surfaces, defect identification may be further complicated by the presence of marks from a machining process. These marks may dramatically and unpredictably change the appearance of the surface, while not altering its ability to function. To differentiate between surface characteristics that constitute a defect and those that do not, we propose a system that directly illuminates specular machined surfaces with a programmable array of high-power light-emitting diodes that allows the angle of the incident light to be varied over a series of images. A reflection model is used to predict the reflected intensity as a function of incident lighting angle for each point on the imaged surface. A surface defect causes the observed reflected intensity as a function of incident lighting angle to differ from that predicted by the reflection model. Such differences between the observations and the reflection model are shown to identify surface defects such as porosities, dents and scratches in the presence of marks from the machining process.     

Improved support vector classification using PCA and ICA feature space modification

An approach that unifies subspace feature selection and optimal classification is presented. Independent component analysis (ICA) and principal component analysis (PCA) provide a maximally variant or statistically independent basis for pattern recognition. A support vector classifier (SVC) provides information about the significance of each feature vector. The feature vectors and the principal and independent component bases are modified to obtain classification results which provide lower classification error and better generalization than can be obtained by the SVC on the raw data and its PCA or ICA subspace representation. The performance of the approach is demonstrated with artificial data sets and an example of face recognition from an image database.     

Real-time measurement of corner position in binary images

The design and testing of an efficient method for measurement of the location of corners of binary regions in digital images is described. From a single perspective image, the image coordinates of corner points are obtained from moments and intersection points accumulated within specified windows. Corner-point coordinates may then be used in further processing such as inverse photogrammetric solutions to determine 3D position. A video-processing board based on a TMS 320C25 DSP chip has been developed to process the image windows. Together with an 80386-based single-board computer, object corner location is achieved at the standard RS-170 television field rate of 60 Hz     

Improved motion estimation time using a combination of dynamic reference frame selection and residue-based mode decision

Motion estimation using multiple reference frames is widely used as the basis for recent video coding standards (eg. H.264/AVC) to achieve increased coding efficiency. However, this increases the complexity of the encoding process. In this paper, a new technique for efficient motion estimation is proposed. A combination of multiple reference frame selection and image residue-based mode selection is used to improve motion estimation time. By dynamic selection of an initial reference frame in advance, the number of reference frames to be considered is reduced. In addition, from examination of the residue between the current block and reconstructed blocks in preceding frames, variable block size mode decisions are made. Modified initial motion vector estimation and early stop condition detection are also adopted to speed up the motion estimation procedure. Experimental results compare the performance of the proposed algorithm with a state of the art motion estimation algorithm and demonstrate significantly reduced motion estimation time while maintaining PSNR performance.     

Differences in the topoisomerase I cleavage complexes formed by camptothecin and wakayin, a DNA-intercalating marine natural product

Wakayin is bispyrroloiminoquinone isolated from a Clavelina sp. ascidian by cytotoxicity directed fractionation. Like camptothecin, it has been found to inhibit the topoisomerase I catalyzed relaxation of supercoiled DNA. Wakayin enhanced cleavage complex formation at the same DNA sequences as camptothecin. Both compounds showed dose-related increases in cleavage complex formation, though wakayin's effect is attenuated at high concentrations. Wakayin is a string DNA binder. Wakayin also differed from camptothecin in that its cleavage complexes were much less stable than those of camptothecin in 0.5 M NaCl. Again in contrast to camptothecin, wakayin stabilized cleavage complexes poorly, if at all, at 0 degree C.     

Vision-guided fixtureless assembly of automotive components

Assembly operations in many industries make extensive use of fixtures that are costly and inflexible. The goal of “robotic fixtureless assembly” (RFA) is to replace these fixtures with sensor-guided robots. In this paper, the development of a vision-guided RFA workcell for automotive components is described. Each robot is equipped with a multiple degree-of-freedom programmable gripper, allowing it to hold a wide range of part shapes without tool changing. A 2D computer vision is used to achieve part pickup which is robust to positioning errors. A novel 3D computer vision system is used to align the parts prior to joining them. The actions of the workcell devices are coordinated using a flexible distributed object-oriented approach. Experimental results are presented for the RFA of four automotive body components.