Image deblurring by means of defocus T.E. Gureyev * , A.W. Stevenson, Ya.I. Nesterets, S.W. Wilkins CSIRO Manufacturing and Infrastructure Technology, Private Bag 33, Clayton South, Vic. 3169, Australia Received 18 March 2004; received in revised form 9 June 2004; accepted 9 June 2004 Abstract A new method for rapid deblurring (partial deconvolution) is proposed which is based on the physics of coherent image formation. The method uses slightly out-of-focus images in a way that makes the Fresnel diffraction counteract the blurring due to the point-spread function. The resultant deblurring improves spatial resolution in the images and is remarkably insensitive to noise. Successful performance of several variants of this technique is demonstrated using sim- ulated and experimental images. It is anticipated that this method will find applications in medical, astronomical and other imaging problems, as well as in lithography. Crown Copyright Ó 2004 Published by Elsevier B.V. All rights reserved. PACS: 42.30.Va; 85.40.Hp; 87.57.Gg; 95.75.Mn Keywords: Image forming and processing; Lithography; Image reconstruction We consider the problem of deconvolution of a noisy image given complete or partial knowledge of the point-spread function (PSF) of the imaging system. Such a problem is encountered in a variety of scientific and industrial applications, e.g. in imag- ing using visible light, electrons, X-rays, etc. (see e.g. [1]). It is also well known that the deconvolution problem is a difficult one due to its mathematical ill-posedness [2]. The latter means in particular that small errors (e.g. noise) in the measured data may re- sult in strong artefacts in the reconstructed (decon- volved) image. A large number of methods have been developed over the years which implement various regularization techniques for more robust deconvolution of noisy data [2,3]. It has been dem- onstrated that accurate deconvolution can be achieved in the presence of suitable additional (a priori) information that helps constrain the set of all possible solutions, thus eliminating some reconstruction artefacts [3]. However, deconvolu- tion methods that make effective use of a priori 0030-4018/$ - see front matter. Crown Copyright Ó 2004 Published by Elsevier B.V. All rights reserved. doi:10.1016/j.optcom.2004.06.020 * Corresponding author. Tel.: +61-3-9545-2702; fax: +61-3- 9544-1128. E-mail address: tim.gureyev@csiro.au (T.E. Gureyev). Optics Communications 240 (2004) 81–88 www.elsevier.com/locate/optcom