[OPTICAL REVIEW Vol. 18, No. 1 (2011) 19-26]
© 2011 The Japan Society of Applied Physics

Tomographic Implementation of Astronomical Speckle Imaging from Bispectra

Susumu KUWAMURA*, Yuuki YOSHINOYA, Noriaki MIURA, Fumiaki TSUMURAYA1, Makoto SAKAMOTO1, and Naoshi BABA2

Department of Computer Sciences, Kitami Institute of Technology, Kitami, Hokkaido 090-8507, Japan
1Nishi-Harima Astronomical Observatory, Sayo, Hyogo 679-5313, Japan
2Division of Applied Physics, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan

(Received October 22, 2010; Accepted November 23, 2010)

A bispectral method for astronomical speckle imaging utilizes an average speckle bispectrum of an object to derive its Fourier phase. There has been, however, a problem in conventional bispectral algorithm owing to difficulty in processing bispectral data in a four-dimensional (4D) space. In this paper, we propose an implementation to overcome this problem, where a one-dimensional (1D) object projection is reconstructed from a two-dimensional (2D) average bispectrum of speckle projections, and object projections so obtained at various angles are then tomographically combined into a 2D object image. In this tomographic approach, processes are separable into those for individual projection angles, implying that bispectral data required to be stored at a time are from 4D to 2D and computation time can be substantially reduced by parallelizing angle-by-angle processes. We have performed experiments using simulated and observed data, and have demonstrated the feasibility of the present approach with an achievable accuracy comparable to that of a conventional approach.

Key words: astronomical speckle imaging, bispectrum, block-building method, projection, tomographic reconstruction

*E-mail address: kuwamura@cs.kitami-it.ac.jp