复眼透镜光学信息保密编码及译码的研究——Ⅱ.分解掩模编码与综合再现

本文根据复眼透镜光学信息编译码的技术原理,实现了对二维图像进行分解编码记录以及综合译码再现.一幅m×n个目标单元的二维图像,通过1×k阵列的复眼透镜,得到(1×k)(m×n)个像元.经过一个特制的掩模板,得到一幅随机分解编码像,并根据透镜的物、像共轭原理,综合再现了原始图像.进而还实现了同时记录多幅二维图像信息的互补编码像,以及将互补编码像分离重现了每一幅原始目标图像.此互补编码像携带了更大的信息量,同时也大大提高了保密性能.     

Object/Context Specific Memory Deficits following Medial Frontal Cortex Damage in Mice

Recent evidence suggests that the medial prefrontal cortex (MFC) is important for processing contextual information. Here we evaluate the performance of mice with MFC damage in a discrimination task that requires an association between an object and the context in which it was experienced (the object/context mismatch task), as well as a version of the novel object preference task that does not require knowledge of contextual information to resolve. Adult C57/BL6 mice received aspiration lesions of the MFC or control surgery. Upon recovery, mice were tested in the object/context mismatch and novel object preference tasks. The object/context mismatch task involved exposing mice to two different contexts, each of which housed a unique pair of identical objects. After a brief delay, mice were re-exposed to one of the contexts, this time with one object that was congruent with that context and one that was not. Novel object preference was performed within a single context, housing an identical pair of objects. After the initial exposure and following a brief delay, mice were re-exposed to the context, this time housing a familiar and a novel object. Control mice were able to successfully resolve the object/context mismatch and novel object preference discriminations, investigating the incongruent/novel object within each task significantly greater than chance. Mice with MFC damage experienced deficits in the object/context mismatch task but not the novel object preference task. These findings add to a growing body of evidence that demonstrate a critical role for the MFC in contextual information processing.     

EEG dynamics reflect the distinct cognitive process of optic problem solving

This study explores the changes in electroencephalographic (EEG) activity associated with the performance of solving an optics maze problem. College students (N = 37) were instructed to construct three solutions to the optical maze in a Web-based learning environment, which required some knowledge of physics. The subjects put forth their best effort to minimize the number of convexes and mirrors needed to guide the image of an object from the entrance to the exit of the maze. This study examines EEG changes in different frequency bands accompanying varying demands on the cognitive process of providing solutions. Results showed that the mean power of θ, α1, α2, and β1 significantly increased as the number of convexes and mirrors used by the students decreased from solution 1 to 3. Moreover, the mean power of θ and α1 significantly increased when the participants constructed their personal optimal solution (the least total number of mirrors and lens used by students) compared to their non-personal optimal solution. In conclusion, the spectral power of frontal, frontal midline and posterior theta, posterior alpha, and temporal beta increased predominantly as the task demands and task performance increased.     

A theory on the determination of 3D motion and 3D structure from features

The present paper proposes a mathematical theory and a method of recognition of both the 3D structure and the motion of a moving object from its monocular image. Initially, characteristic features are extracted from the 2D perspective image of the object. Because motion of the object induces a change in its 2D perspective image, it also induces a change in the features which depends on the 3D structure and the velocity of the object. This suggests the possibility of detecting the 3D structure and the motion directly from the features and their changing rate, without the need for calculating optical flows. An analysis is made of the relation between the 3D rigid motion of a surface element and the change in local linear features. From this relation, a method is proposed for calculating the velocity of and the normal to the surface element without considering any correspondence of points. An optical flow can also be calculated by this method. Two simple computer simulations are provided.     

A Method for the Evaluation of Image Quality According to the Recognition Effectiveness of Objects in the Optical Remote Sensing Image Using Machine Learning Algorithm

Objective and effective image quality assessment (IQA) is directly related to the application of optical remote sensing images (ORSI). In this study, a new IQA method of standardizing the target object recognition rate (ORR) is presented to reflect quality. First, several quality degradation treatments with high-resolution ORSIs are implemented to model the ORSIs obtained in different imaging conditions; then, a machine learning algorithm is adopted for recognition experiments on a chosen target object to obtain ORRs; finally, a comparison with commonly used IQA indicators was performed to reveal their applicability and limitations. The results showed that the ORR of the original ORSI was calculated to be up to 81.95%, whereas the ORR ratios of the quality-degraded images to the original images were 65.52%, 64.58%, 71.21%, and 73.11%. The results show that these data can more accurately reflect the advantages and disadvantages of different images in object identification and information extraction when compared with conventional digital image assessment indexes. By recognizing the difference in image quality from the application effect perspective, using a machine learning algorithm to extract regional gray scale features of typical objects in the image for analysis, and quantitatively assessing quality of ORSI according to the difference, this method provides a new approach for objective ORSI assessment.     

Effect of segmentation errors on 3D-to-2D registration of implant models in X-ray images

In many biomedical applications, it is desirable to estimate the three-dimensional (3D) position and orientation (pose) of a metallic rigid object (such as a knee or hip implant) from its projection in a two-dimensional (2D) X-ray image. If the geometry of the object is known, as well as the details of the image formation process, then the pose of the object with respect to the sensor can be determined. A common method for 3D-to-2D registration is to first segment the silhouette contour from the X-ray image; that is, identify all points in the image that belong to the 2D silhouette and not to the background. This segmentation step is then followed by a search for the 3D pose that will best match the observed contour with a predicted contour. Although the silhouette of a metallic object is often clearly visible in an X-ray image, adjacent tissue and occlusions can make the exact location of the silhouette contour difficult to determine in places. Occlusion can occur when another object (such as another implant component) partially blocks the view of the object of interest. In this paper, we argue that common methods for segmentation can produce errors in the location of the 2D contour, and hence errors in the resulting 3D estimate of the pose. We show, on a typical fluoroscopy image of a knee implant component, that interactive and automatic methods for segmentation result in segmented contours that vary significantly. We show how the variability in the 2D contours (quantified by two different metrics) corresponds to variability in the 3D poses. Finally, we illustrate how traditional segmentation methods can fail completely in the (not uncommon) cases of images with occlusion.     

Relationship Between the Reaction Time and EEG Parameters During Judgments on the Correspondence of Delayed or Simultaneously Presented Images of Two Models

This study examined how judging whether the poses of two figures are the same in tasks with delayed and simultaneous image presentation affects the participants’ reaction times and electroencephalograms (EEGs). Eighteen university students performed a delayed task, in which an image of a doll was first presented for 3 sec followed by a second image of the doll, and a simultaneous task, in which images of two dolls were presented on the left and right sides of the monitor at the same time. The dolls were shown from the front and rear angles. The participants were instructed to judge whether the images were the same as accurately and quickly as possible, and the reaction times were recorded. EEG signals were recorded from Fp1, Fp2, F3, F4, C3, C4, P3, and P4. The reaction times in the delayed task were found to be shorter then those in the simultaneous task, and that these times for the 0° condition were shorter than for the 180° condition. The amplitudes of EEG responses at Fp1 and Fp2 were larger than those at other electrodes, and the responses in the right hemisphere during the 180° condition and the delayed task within the α1 frequency band were smaller than the responses at other electrodes. These results indicate that cerebral activity in the frontal region of the right hemisphere is associated with the judgment of correspondence or non-correspondence in spatial compatibility tasks.     

Fully automated measurements by light microscopy of tissue sections using a cellular array computer

Software was developed for the acquisition, segmentation and analysis of microscopic OD-images on a VICOM digital image processor, extended with a VISIOMORPH morphoprocessor board. The delineation algorithms for peroxisomes, lysosomes, and nuclei in liver, kidney, and adrenal gland sections start by thresholding the difference between the original image and a low pass filtered version. The resulting binary mask is then processed by morphological operations in order to produce an object overlay. The efficiency of the programs is evaluated by comparing delineated objects at different OD-levels, created by varying the stain or by multiplying the original pixel values with constant factors. Manual delineation on some images is also used as a reference. More complex algorithms are used for the delineation of muscle fibres in ATP-ase-stained sections and immunocytochemically labelled cells in monolayer preparations. Muscle images from parallel sections with different stainings are matched with a coordinate transform, enabling the transfer of the object mask from a single delineated image to the unprocessed images and thus obtain all necessary information for fibre classification. After segmentation, the OD-images and their object overlays are fed into a data extraction program, measuring for each delineated object user-selected features. Data are sent to a VAX for statistical interpretation.     

Object concept and mental representation inCebus apella andMacaca fascicularis

The achievement of Stage 6 object concept as an index of the representational capacity, was studied both in juveniles and adults of two nonhuman primate species,Cebus apella andMacaca fascicularis. The general goal of the present investigation was to evaluate the real nature of the strategy adopted by subjects searching an object in the invisible displacement task. To this purpose, the original Piagetian version of the invisible displacement task was used modifying some parameters and employing additional tasks and analyses in order to differentiate representational solutions from the nonrepresentational ones. With this method it was found that an adult cebus, but not macaques, solved the invisible displacement task with the use of the mental representation.     

The influence of change in the size of face elements on the perception of a woman's portrait

This research attempts to answer the question how the change of selected face elements influences the likeness between the original portrait (sketch) and its modified versions. For this purpose, several series of portraits were created into which changes to the original sizes of eyes, mouth and nose within a scope of +/-14% (every 2%) were introduced. The task for a subject consisted of indicating one portrait out of each row that was the first to be "clearly unlike the original image". In this way, two values were obtained for each feature (lesser and greater than the initial one). These values have been called "the terminal values", i.e. those which, according to the subjects, once exceeded, the portrait becomes unlike the original. The results obtained indicate that the majority of the subjects, as much as 61.7%, consider the face they observe to be "clearly different" when the change of the studied features amounts to at least 8% of the original value, or even 6% in some cases. In addition, it has been noticed that, in the process of identification, men much earlier than women (p=0.049) consider the portraits in the row with the reduction of eye size unlike the original image.     

Development of Architectures for Internet Telerobotics Systems

This paper presents our experience in developing and implementing Internet telerobotics system. Internet telerobotics system refers to a robot system controlled and monitored remotely through the Internet. A robot manipulator with five degrees of freedom, called Mentor, is employed. Client-server architecture is chosen as a platform for our Internet telerobotics system. Three generations of telerobotics systems have evolved in this research. The first generation was based on CGI and two tiered architectures, where a client presents a Graphical User Interface to the user, and utilizes the user＇s data entry and actions to perform requests to robot server running on a different machine. The second generation was developed using Java. We also employ Java 3D for creating and manipulating 3D geometry of manipulator links, and for constructing the structures used in rendering that geometry, resulting in 3D robot movement simulation presented to the users （clients） through their web browser. Recent development in our Internet telerobotics includes object recognition through image captured by a camera, which poses challenging problem, giving the undeterministic latency of the Internet. The third generation is centered around the use of CORBA for development platform of distributed internet telerobotics system, aimed at distributing task of telerobotics system.     

Evidence for a specific internal representation of motion–force relationships during object manipulation

 Human subjects learned a tracking task which required them to point at a moving target with the free end of an inverted pendulum object. In order to determine how subjects represented this object internally, we studied learning interference between variants of this task in which the pendulum object had either stable or unstable dynamics. Using a novel method, agreement between possible internal representations of the two tasks was estimated by analysis of the motion-to-torque relationships experienced by each subject as they manipulated each object. It was possible to predict retention of the primary task on day 2 from our measure of agreement between primary and interfering tasks on day 1. This result suggests that the subjects learned the correct torque patterns to use to produce specific desired patterns of motion as they learned the balancing task. Surprisingly, the analyses indicate that retention was not impaired when similar motions of the two objects required retrieval of incompatible torque responses, but retention was impaired when similar patterns of motion in the two tasks required similar patterns of applied torque. These findings can be accounted for by a simple model of how multiple similar torque responses are selected and retrieved from memory when responses are freely chosen. Received: 20 December 2001 / Accepted in revised form: 25 July 2002 Correspondence to: C. D. Mah (e-mail: c-mah@northwestern.edu)     

Detecting binocular 3D motion in static 3D noise: no effect of viewing distance

Relative binocular disparity cannot tell us the absolute 3D shape of an object, nor the 3D trajectory of its motion, unless the visual system has independent access to how far away the object is at any moment. Indeed, as the viewing distance is changed, the same disparate retinal motions will correspond to very different real 3D trajectories. In this paper we were interested in whether binocular 3D motion detection is affected by viewing distance. A visual search task was used, in which the observer is asked to detect a target dot, moving in 3D, amidst 3D stationary distractor dots. We found that distance does not affect detection performance. Motion-in-depth is consistently harder to detect than the equivalent lateral motion, for all viewing distances. For a constant retinal motion with both lateral and motion-in-depth components, detection performance is constant despite variations in viewing distance that produce large changes in the direction of the 3D trajectory. We conclude that binocular 3D motion detection relies on retinal, not absolute, visual signals.     

A microcomputer based system for three-dimensional reconstructions from tomographic or histologic sections

The reconstructions of three-dimensional (3-D) objects from serial two-dimensional (2-D) images can contribute to the understanding of many biologic structures, from organelles to organs and tissues. The 3-D reconstruction of sections can be divided into several major tasks: image acquisition, alignment of slices, internal object definition, object reconstruction and rotation of the completed image. A fast, versatile, interactive system was devised for the reconstruction of 3-D objects from serial 2-D images using a low-cost microcomputer, original programs and commercial software. The system allows reconstruction from any serial images, e.g., electron micrographs, histologic sections or computed tomograms. A photographic image or a microscopic field is acquired into the computer memory using a video digitizer. Slices are superimposed and aligned to each other using an operator-interactive program. A contour-(edge-) finding algorithm isolates an object of interest from the background image by "subtraction" of the image from an overlaid, slightly shifted identical image. Contours for each slice are input to a reconstruction procedure, which calculates the x, y and z coordinates of every point in a slice and the thickness and number of slices. It then calculates the illumination for every point using a given point source of light and an intensity-fading coefficient. Finally, the points are represented by cubes to provide dimension and reflective surfaces. A cube of appropriate shade and color represents in 2-D the equivalent of a 3-D object; this results in a very effective 3-D image. The reconstruction is rotated by recalculating the positions of every point defining the object and rebuilding the image.(ABSTRACT TRUNCATED AT 250 WORDS)     

Handling objects in old age: forces and moments acting on the object

We measured the external moments and digit-tip force directions acting on a freely moveable object while it was grasped and manipulated by old (OA) and young (YA) adults. Participants performed a grasp and lift task and a precision orientation (key-slot) task with a precision (thumb-finger) grip. During the grasp-lift task the OA group misaligned their thumb and finger contacts and produced greater grip force, greater external moments on the object around its roll axis, and oriented force vectors differently compared with the YA group. During the key-slot task, the OA group was more variable in digit-tip force directions and performed the key-slot task more slowly. With practice the OA group aligned their digits, reduced their grip force, and minimized external moments on the object, clearly demonstrating that the nervous system monitored and actively manipulated one or more variables related to object tilt. This was true even for the grip-lift task, a task for which no instructions regarding object orientation were given and which could tolerate modest amounts of object tilt without interfering with task goals. Although the OA group performed the key-slot task faster with experience, they remained slower than the YA group. We conclude that with old age comes a reduced ability to control the forces and moments applied to objects during precision grasp and manipulation. This may contribute to the ubiquitous slowing and deteriorating manual dexterity in healthy aging.     

Tracking facilitates 3-D motion estimation

The recently emerging paradigm of Active Vision advocates studying visual problems in form of modules that are directly related to a visual task for observers that are active. Along these lines, we are arguing that in many cases when an object is moving in an unrestricted manner (translation and rotation) in the 3D world, we are just interested in the motion's translational components. For a monocular observer, using only the normal flow — the spatio-temporal derivatives of the image intensity function — we solve the problem of computing the direction of translation and the time to collision. We do not use optical flow since its computation is an ill-posed problem, and in the general case it is not the same as the motion field — the projection of 3D motion on the image plane. The basic idea of our motion parameter estimation strategy lies in the employment of fixation and tracking. Fixation simplifies much of the computation by placing the object at the center of the visual field, and the main advantage of tracking is the accumulation of information over time. We show how tracking is accomplished using normal flow measurements and use it for two different tasks in the solution process. First it serves as a tool to compensate for the lack of existence of an optical flow field and thus to estimate the translation parallel to the image plane; and second it gathers information about the motion component perpendicular to the image plane.     

Constructing complex 3D biological environments from medical imaging using high performance computing

Extracting information about the structure of biological tissue from static image data is a complex task requiring computationally intensive operations. Here, we present how multicore CPUs and GPUs have been utilized to extract information about the shape, size, and path followed by the mammalian oviduct, called the fallopian tube in humans, from histology images, to create a unique but realistic 3D virtual organ. Histology images were processed to identify the individual cross sections and determine the 3D path that the tube follows through the tissue. This information was then related back to the histology images, linking the 2D cross sections with their corresponding 3D position along the oviduct. A series of linear 2D spline cross sections, which were computationally generated for the length of the oviduct, were bound to the 3D path of the tube using a novel particle system technique that provides smooth resolution of self-intersections. This results in a unique 3D model of the oviduct, which is grounded in reality. The GPU is used for the processor intensive operations of image processing and particle physics based simulations, significantly reducing the time required to generate a complete model.     

Modeling feature-based attention as an active top-down inference process

Vision is a crucial sensor. It provides a very rich collection of information about our environment. The difficulty in vision arises, since this information is not obvious in the image, it has to be constructed. Wheres earlier approaches have favored a bottom-up approach, which maps the image onto an internal representation of the world, more recent approaches search for alternatives and develop frameworks which make use of top-down connections. In these approaches vision is inherently a constructive process which makes use of a priory information. Following this line of research, a model of primate object perception is presented and used to simulate an object detection task in natural scenes. The model predicts that early responses in extrastriate visual areas are modulated by the visual goal.     

Modeling feature-based attention as an active top-down inference process

Vision is a crucial sensor. It provides a very rich collection of information about our environment. The difficulty in vision arises, since this information is not obvious in the image, it has to be constructed. Wheres earlier approaches have favored a bottom-up approach, which maps the image onto an internal representation of the world, more recent approaches search for alternatives and develop frameworks which make use of top-down connections. In these approaches vision is inherently a constructive process which makes use of a priory information. Following this line of research, a model of primate object perception is presented and used to simulate an object detection task in natural scenes. The model predicts that early responses in extrastriate visual areas are modulated by the visual goal.