Browsing by Author "Chou, HL"

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3D shape recovery of complex objects from multiple silhouette images
(2003-06-01)
Fang, YH
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Chou, HL
;
Chen, Z
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資訊工程學系
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Department of Computer Science
A reconstruction method is proposed which represents the object with a line-based geometric model. The method does not need the point correspondence information in recovering the 3D object geometry. It is based on the concept of volume intersection, but it is substantially different from the existing octree-based reconstruction methods in the aspects of data structure, reconstruction process and representation uniqueness under a 2D rigid motion. For visualizing the 3D reconstructed object geometry a conversion from the line-based geometric model to a bounded triangular mesh model is developed. The experimental results show that the method is capable of capturing the different details of the object. And it works fast and requires a relatively low memory space. (C) 2002 Elsevier Science B.V. All rights reserved.
A novel 3D planar object reconstruction from multiple uncalibrated images using the plane-induced homographies
(2004-09-01)
Chou, HL
;
Chen, Z
;
資訊工程學系
;
Department of Computer Science
A computer vision method is proposed to determine all the visible 3D planar surfaces in a scene from uncalibrated images and locate them in a single 3D projective space. Most of the existing methods for reconstructing planar objects use point correspondences to estimate the fundamental matrix and derive the compatible projection equations, before they apply the standard triangulation technique to find the 3D points and fit the planes to the 3D points. This type of approaches is generally slow and less accurate because the 3D points are estimated separately, making them vulnerable to image error. We present a plane based reconstruction method to estimate the 3D projective structure using the planar homographies estimated from the plane features in the images. First, we estimate the homography for each visible plane.. and then we use the homographies of two primary planes to compute an epipole. We proceed to represent the epipolar geometry for each image pair using the estimated homography and epipole, together with a specified reference plane coefficient vector. Next, we show that the 3D plane coefficient vector of any plane visible in each image pair can be determined with respect to the reference plane coefficient vector once its planar homography is found. Finally, the reconstruction results obtained in individual projective spaces are integrated within a common projective space. To this end. we use the homography and plane equation information of two planes and the epipole associated to derive the coordinate transformation matrix between two involved projective spaces. To evaluate the performance of our method, we apply our method to the synthetic images and real images. All the results indicate the method works successfully. (C) 2004 Published by Elsevier B.V.
Fast octree construction endowed with an error bound controlled subdivision scheme
(2006-05-01)
Chou, HL
;
Chen, Z
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資訊工程學系
;
Department of Computer Science
In the conventional octree construction method any grey octant is subdivided recursively until all its descendant octants are no longer grey. The subdivision process is executed no matter how small the white portion in the grey octant is. When there are many grey octants, each containing a fairly small white portion, then the huge increase in the resulting descendant nodes due to the subdivisions may cause the construction process to terminate due to an insufficient amount of memory. In such a case the subdivisions made are not worthwhile. In this paper, we shall make effective use of octant subdivision to improve the overall system performance. A new octree construction method is proposed with a novel subdivision strategy such that only those octants with a projection error exceeding a pre-specified error bound will be subdivided. Furthermore, we also present a fast way to compute the 2D projection of octant vertices and a new intersection test to reduce overall processing time. Computer simulations are conducted which show that the new method performs better than the conventional method in terms of memory space and computation time. Moreover, a theoretical analysis of the performance of the new method is included.
Fiber-lens-based module for optical recording applications
(2003-07-01)
Tien, CH
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Chou, HL
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Chiu, Y
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Hsu, W
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Milster, TD
An optical fiber-lens-type pickup with numerical aperture (NA) congruent to 0.27 was demonstrated for thermal recording of continuous 1.6-mum-wide lines on MO disks with 50% throughput efficiency. Moreover, a Si-micromachined near-field module integrated with a fiber lens, solid immersion lens (SIL), and submicron aperture was fabricated to improve the mechanical fragility and increase the NA of the optical-fiber-based pickup. The preliminary configuration design and measurement suggest the feasibility of the module as a submicron heat source for high-density optical data storage.
Integrated near-field optical head for hybrid recording
(2003)
Chiu, Y
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Wu, M
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Shieh, HPD
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Sun, YT
;
Chou, HL
As the recording density of longitudinal magnetic storage increases at a 100% annual growth rate, it will soon approach the superparamagnetic limit where the thermal energy at room temperature starts to induce thermal instability to the grains in the small recorded marks. Thermal magnetic recording schemes, such as those used in magneto-optical recording, help alleviate the problems with the superparamagnetic limit. Recently, a hybrid recording system was proposed where data were recorded thermal magnetically on a magneto-optical disk and read back with a GMR head. In this paper, we propose an integrated planar head that combines an optical fiber lens, a solid immersion lens, a sub wavelength aperture, a micro coil, an air bearing surface, and a GMR head for such a hybrid recording system. Preliminary fabrication and calculation are discussed.