Shift-and-add image processing incorporated with the unsharp masking method.

Shift-and-add (SAA) is a simple image processing procedure. SAA was devised to reconstruct a diffraction-limited image from atmospherically degraded stellar images. Recently SAA has been applied to biological imaging. There are several variants of SAA. Here proposed is an SAA procedure incorporated with unsharp masking (USM). The SAA procedure proposed here encompasses an extended version of USM. The proposed SAA method retains the simplicity and easiness, and the basic features of SAA. The effectiveness of the proposed method is examined by restoring atmospherically degraded solar images. It is shown that the USM SAA reconstructed image exhibits high contrast and reveals fine structures blurred by atmospheric turbulence. It is also shown that the USM SAA performs better with a data frame selection scheme.

Wavelength scanning profilometry for real-time surface shape measurement.

Wavelength scanning profilometry suitable for real-time surface shape measurement is proposed. A phase slope of the interference signal generated by a wavelength scan is measured at an individual image pixel on-line. The parallel outputs of these on-line measurements show a map of surface height in real time. Experiments where a tunable dye laser was used were conducted to simulate the real-time measurements of step objects with specular and diffuse surfaces. The results have shown that a height map is available at any moment during the wavelength scan, and the measurement accuracy of height increases as the scanning proceeds. For a scanning width of 25 nm, the accuracy was as high as 1 mum. Analyses of the measurement accuracy are given.

Stellar speckle camera for spectroscopy.

A stellar speckle spectrometer with increased performance and flexibility has been newly developed. In this new spectrometer two synchronized detectors are used to observe a dispersed speckle pattern and a specklegram. A reflection grating is employed as a disperser. We obtained a stellar spectrum with the diffraction-limited spatial resolution of a telescope by referring to specklegrams that are simultaneously recorded with dispersed speckle patterns. A preliminary observational result is also shown.

Speckle decorrelation in surface profilometry by wavelength scanning interferometry.

The accuracy and the measurement range of surface profilometry by wavelength scanning interferometry applied to diffusely reflecting surfaces are investigated. The influences of surface roughness and the imaging system in the interferometer are theoretically analyzed by derivation of the autocorrelation function of interferograms arising from wavelength scanning. By using a dye laser with a tuning range of 4.2 nm to a yield resolution of 39.1 mum, we have observed interferograms and their Fourier transforms and autocorrelations to study effects of defocusing and the size ratio of speckle to the CCD pixel for a plane diffuse object positioned normal to the incident beam.

Stellar speckle imaging by reference to different-colored specklegrams.

Stellar specklegrams at different wavelengths are examined. The position of the brightest speckle at one wavelength is shown to coincide nearly with that at a widely separated wavelength. The shift-and-add operation for specklegrams at one wavelength produces a high-resolution stellar image at the other wavelength. We show that the shift-and-add operation at 450 nm results in a high-resolution image at 800 nm by use of observational speckle data from which specklegrams at these wavelengths are taken simultaneously.

Speckle spectroscopy with tip-tilt operation.

A stellar speckle spectrometer with tip-tilt operation is proposed for high-spatial-resolution spectroscopy under atmospheric turbulence. A specklegram is used to drive a tip-tilt mirror for real-time shift-and-add operation to its dispersed specklegram. The proposed speckle spectroscopy attains a long exposure for the spectrum and a slit spectrometer. Several simulation experiments confirm the effectiveness of our method.

Toward high-resolution imaging with a simple adaptive-optics system.

High-resolution imaging with reference to a widely separated star is examined. Peak tracking of the specklegram in the reference channel results in a high-resolution image in the observational channel. A binary star with angular separation of 30.5 arcsec is examined in white light, and the resultant image of the primary star obtained with reference to the secondary star is shown to have better resolution than the centroid tracking image by a factor of 3.

Parallel scheme of the iterative blind deconvolution method for stellar object reconstruction.

An algorithm for stellar object reconstruction without a reference star is described. The algorithm is based on parallel application of the iterative blind deconvolution method to several speckle frames, and it permits reconstruction of an object that satisfies the convolution relation in all the frames used. Computer simulations with noisy speckle images are carried out to demonstrate performances of the algorithm. The algorithm is applied to observational data of binary stars, and high-resolution images are clearly reconstructed. Binary parameters extracted from the images show good consistency with those obtained both with the power spectrum analysis and with the shift-and-add method.