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Rational filter design for depth from defocus

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Joseph Raj, Alex Noel and Staunton, R. C.. (2012) Rational filter design for depth from defocus. Pattern Recognition, Vol.45 (No.1). pp. 198-207. ISSN 0031-3203

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Official URL: http://dx.doi.org/10.1016/j.patcog.2011.06.008

Abstract

The paper describes a new, simple procedure to determine the rational filters that are used in the depth from defocus (DfD) procedure previously researched by Watanabe and Nayar [4]. Their DfD uses two differently defocused images and the filters accurately model the relative defocus in the images and provide a fast calculation of distance. This paper presents a simple method to determine the filter coefficients by separating the M/P ratio into a linear and a cubic error correction model. The method avoids the previous iterative minimisation technique and computes efficiently. The model has been verified by comparison with the theoretical M/P ratio. The proposed filters have been compared with the previous for frequency response, closeness of fit to M/P, rotational symmetry, and measurement accuracy. Experiments were performed for several defocus conditions. It was observed that the new filters were largely insensitive to object texture and modelled the blur more precisely than the previous. Experiments with real planar images demonstrated a maximum RMS depth error of 1.18% for the proposed, compared to 1.54% for the previous filters. Complicated objects were also accurately measured.

Item Type:	Journal Article
Subjects:	Q Science > QA Mathematics T Technology > TK Electrical engineering. Electronics Nuclear engineering
Divisions:	Faculty of Science > Engineering
Library of Congress Subject Headings (LCSH):	Filters (Mathematics), Image processing -- Digital techniques
Journal or Publication Title:	Pattern Recognition
Publisher:	Pergamon-Elsevier Science Ltd.
ISSN:	0031-3203
Date:	January 2012
Volume:	Vol.45
Number:	No.1
Number of Pages:	10
Page Range:	pp. 198-207
Identification Number:	10.1016/j.patcog.2011.06.008
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
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URI:	http://wrap.warwick.ac.uk/id/eprint/40476