In order to search for an object as efficiently as possible, it can be very useful to take advantage of the spatial relationships in which it commonly participates. Searches that do so, which we call indirect searches...
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ISBN:
(纸本)0819410268
In order to search for an object as efficiently as possible, it can be very useful to take advantage of the spatial relationships in which it commonly participates. Searches that do so, which we call indirect searches, can be modeled as two-stage processes that first find an intermediate object that commonly participates in a spatial relationship for the target object, and then look for the target in the restricted region specified by this relationship. Using this model, previous work has determined that over a wide range of situations, for searches that involve rotating a camera about a fixed location, indirect searches improve efficiency by factors of 2 to 8. However, several areas require future research if indirect search is to become a widely applicable easily usable technique. This paper describes three major areas in need of study - recognizing typical intermediate objects, defining spatial relationships, and constructing mechanisms for moving a camera to examine cluttered regions of space. It concentrates especially on the latter topic, discussing many issues arising in the design of systems for looking around clutter and occlusions.
This paper describes the process of calibrating the kinematic model for an active binocular head having four revolute joints and two prismatic joints. We use the complete and parametrically continuous (CPC) model prop...
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ISBN:
(纸本)0819410268
This paper describes the process of calibrating the kinematic model for an active binocular head having four revolute joints and two prismatic joints. We use the complete and parametrically continuous (CPC) model proposed by Zhuang and Roth in 1990 to model the motorized head (or camera positioning system), and use a closed form solution to identify its CPC kinematic parameters. The calibration procedure is divided into two stages. In the first stage, the two cameras are replaced by two end-effector calibration plates each having nine circles. The two removed cameras can be used to build a stereo vision system for observing the varying positions and orientations of the end-effector calibration plates when moving the joints of the head. The positions and orientations of the calibration plates, or equivalently, of the end-effectors, can be determined from the stereo measurements. The acquired data are then used to calibrate the kinematic parameters. In the second stage, the cameras are remounted to the IIS-head, and a method proposed by Tsai is used to calibrate the hand-eye relation. Once the above kinematics calibration is done, the binocular head can be controlled to gaze or track 3-D targets.
A cellular multilayer phase grating with hexagonal closest packing proves to be the ideal focal plane architecture for the human eye, and is thus also the best model for designing stimulus- adaptive robot eyes which a...
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ISBN:
(纸本)0819410268
A cellular multilayer phase grating with hexagonal closest packing proves to be the ideal focal plane architecture for the human eye, and is thus also the best model for designing stimulus- adaptive robot eyes which achieve the spatial and chromatic performance of the human eye. Crystal-optical calculation of the retinal cellular multilayer chip and the resulting correlations between the physical stimulus parameters and the adaptive shifts in human vision at the retinal level give rise to a time-frequency diagram of the eye and its stimulus-adaptive latitudes, which will become relevant in the design of future chips for robot eyes with performance comparable to that of human vision. The current presentation shows that 3-D grating optical parameters ensure the frequency-related chromatic adaptive shifts (transition from photopic to scotopic vision in the Purkinje shift, Stiles-Crawford effects I/II, Bezold-Bruecke phenomenon, chromatic adaptation to artificial light sources of different spectral composition, etc.) and also indicates what 3-D grating optical parameters are relevant to spatial transfer and adaptation, i.e., the time-related aspects in the time-frequency diagram (adaptation of the spatial modulation transfer function to the image parameters;log term for spatial adaptation to the intensity level;coding of spatial phase relationships between a fundamental spatial frequency and higher frequencies up to the third harmonic, etc.).
For many applications in computervision, it is important to recover range, 3-D motion, and/or scene geometry from a sequence of images. However, there are many robot behaviors which can be achieved by extracting rele...
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ISBN:
(纸本)0819410268
For many applications in computervision, it is important to recover range, 3-D motion, and/or scene geometry from a sequence of images. However, there are many robot behaviors which can be achieved by extracting relevant 2-D information from the imagery and using this information directly, without recovery of such information. In this paper, we focus on two behaviors, obstacle avoidance and terrain navigation. A novel method of these two behaviors has been developed without 3-D reconstruction. This approach is often called purposive active vision. A linear relationship, plotted as a line and called a reference flow line, has been found. The difference between a plotted line and the reference flow line can be used to detect discrete obstacles above or below the reference terrain. For terrain characterization, slopes of surface regions can be calculated directly from optical flow. Some error analysis is also done. The main features of this approach are that (1) discrete obstacles are detected directly from 2-D optical flow, no 3-D reconstruction is performed;(2) terrain slopes are also calculated from 2- D optical flow;(3) knowledge about the terrain model, camera-to-ground coordinate transformation, or vehicle (or camera) motion is not required;(4) the error sources involved are reduced to a minimum, since the only information required is a component of optical flow. An initial experiment using noisy synthetic data is also included to demonstrate the applicability and robustness of the method.
We describe a robot vision system that achieves complex object recognition with two layers of behaviors, performing the tasks of planning and object recognition, respectively. The recognition layer is a pipeline in wh...
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When a camera's center axis is not parallel to the surface normal of a planar object, the perceived shape of the object will be skewed. Most existing shape analysis methods are sensitive to such shape distortions....
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ISBN:
(纸本)0819410268
When a camera's center axis is not parallel to the surface normal of a planar object, the perceived shape of the object will be skewed. Most existing shape analysis methods are sensitive to such shape distortions. That is, if a shape is skewed due to non-orthographic projection, it may not be correctly recognized. In this paper we present a shape normalization process which neutralizes such shape skewing effects. In our case, a perceived shape is represented by a list of corner points along its boundary. We first compute the six lower moments of the shape from its boundary. Then these moments are used to compute the shape's center location, orientation, and maximum and minimum moments of inertia. To normalize the shape we first translate the shape's center to the origin. Next we rotate the shape to align its major axis with the x-axis. Then we expand the shape along its minor axis to neutralize shape skewing. Lastly, we scale the size of the shape so it has a standard moment of inertia. The suggested method can be used as a preprocessing step for any planar shape analysis method which is sensitive to shape skewing, shape size change, and/or shape translation. Since the moments are computed from the shape's boundary instead of from all its interior pixels, the method is also efficient. Several experimental results are given to show the effectiveness of the approach.
We have built a new miniature pan-tilt actuator, the spherical pointing motor (SPM). The SPM is an absolute positioning device, designed to orient a small camera sensor in two degrees of rotational freedom. The basic ...
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ISBN:
(纸本)0819410268
We have built a new miniature pan-tilt actuator, the spherical pointing motor (SPM). The SPM is an absolute positioning device, designed to orient a small camera sensor in two degrees of rotational freedom. The basic idea is to orient a permanent magnet to the magnetic field induced by three orthogonal coils by applying the appropriate ratio of currents to the coils. The function describing the relation between the coil currents and the resultant motor position can be calculated, but it is not very accurate as the actual coils do not exactly satisfy the assumptions made in these calculations. The motor must be calibrated to find the coil currents accurately. This paper describes a procedure for automatic calibration of the SPM. It is based on image feedback from a camera returning space-variant images, mounted on the rotor of the motor. It assumes that a calibrated image sensor and lens are used, i.e., that it is known how many degrees each pixel subtends. It also assumes that the camera rotates about its focal point. The calibration algorithm uses a scene of black dots on a white background. For each motor position that is to be calibrated, the algorithm moves the motor approximately to that position using the calculated currents. The algorithm analyzes the image, and uses the position of the relevant dot to calculate the actual position of the motor. It then associates this position with the coil currents and stores it in a look-up-table. Finally, we interpolate between calibrated points to move to other positions.
The concept of active object recognition is introduced and a proposal for its solution is described. It is argued that single-view object recognition is fraught with problems, mainly due to viewpoint-related ambiguiti...
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The representation and recognition of object shapes are important tasks of image analysis and computervision systems. In the last years, a lot of effort has been made in these fieds and there are many applications in...
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We present a solution to a common problem in industrial machine vision, to identify and estimate the orientation of touching mechanical parts on a plane surface. The algorithm is based on watershed segmentation and ca...
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ISBN:
(纸本)0819410268
We present a solution to a common problem in industrial machine vision, to identify and estimate the orientation of touching mechanical parts on a plane surface. The algorithm is based on watershed segmentation and can handle cases where objects touch. After an initial thresholding step, we extract the edges of the binary image, the outer edge as well as edges around holes inside the object. Then we use a distance transformation to create a distance map, i.e., an image where each pixel value represents the distance to the nearest edge pixel. The watershed algorithm is applied on the distance map and we get an image where some objects may be segmented into several parts. For every segment we calculate the center of gravity for its surrounding edge pixels. The different centers of gravity are enough for estimating the orientation of objects that have been segmented into more than one segment. By also calculating the center of gravity for holes of the object and using them in the same way we can estimate the orientation of objects having holes. To recognize the mechanical parts we use the distances between the center of gravity of its segments and holes together with the greatest maximum of the distance map that we find inside each of them. We also calculate the length of the peripheries of the segments and use them to distinguish the objects. We can perhaps recognize, and certainly locate, but not estimate the rotation of the mechanical parts that consist of only one segment without holes. For those objects we construct a circle around the center of gravity with the corresponding greatest maximum as radius. We collect the values of the distance map on this circle line and plot them as a function of the angle to the horizontal axis. We can identify the maxima and minima of this function, from which we estimate the rotation of the object. This information can also be used to identify the object. For overall control algorithm we are using fuzzy logics. As a final step to
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