STUDIES ON HIGH-RESOLUTION IMAGING WITH TWO-COLOR SPECKLEGRAMS

由于地球的大气湍流，从地面观察到的恒星物体的短曝光图像显示出类似斑点的图案。然而，这样的散斑图包含了望远镜衍射受限分辨率的物体的信息。散斑干涉是除自适应光学外获得高分辨率图像的一种简单方法。当两个波长相差很大的散斑图之间存在较高的相关性时，通过参考另一个波长的散斑图来实现高分辨率成像是可行的，其中恒星物体表现为点源或参考星。本研究的目的是通过分析两个不同波长的散斑图来建立双色散斑图的高分辨率成像方法。我们用安装在日本冈山天体物理观测站90 cm或188 cm望远镜上的双色散斑相机对卡佩拉和织女星进行了观测，探测波长在短波长为400 nm或450 nm，长波长为800 nm。这些波长对应于可见光区域的极值，比例约为两倍。对一个波长的散斑图进行移位和加法运算，得到另一个波长的伴随重建图像。结果表明，参考另一波长的散斑图重建的图像优于通过对散斑图居中并添加重力而产生的伪长曝光图像。这表明，利用不同波长的散斑图可以实现高分辨率成像。我们的方法在可见光-近红外观测中的应用仍是一个未来的项目。

A short exposure image of a stellar object observed from the ground exhibits a speckle-like pattern because of atmospheric turbulence of the earth. However, such a specklegram contains the information of the object with diffraction-limited resolution of a telescope. The speckle interferometry is a simple method to get high-resolution image apart from adaptive optics. When there is a high correlation between two specklegrams with greatly differnt wavelengths, high-resolution imaging is feasible at one wavelength by reference to a specklegram at the other wavelength where the stellar object appears as a point-source or a reference star is available.The purpose of this research project is to establish high-resolution imaging method with two-color specklegrams by analysing specklegrams at two greatly different wavelengths. We conducted observations of Capella and Vega with our two-color speckle camera attached to the 90cm or 188cm telescope at the Okayama Astrophysical Observatory, NAOJ.The detection wavelengths are 400nm or 450nm at the short wavelength and 800nm at the long one. These wavelengths correspond to the extremes of the visible region and the ratio is about two.The shift-and-add operation for specklegrams at one wavelength results in an accompaningly reconstructed image at the other wavelength. It is clarified that the reconstructed image at one wavelength by reference to specklegrams at the other wavelength is better than the pseudo long exposure image, which is produced by centering and adding the gravity of specklegrams. This shows that high-resolution imaging is possible by utilizing specklegrams at the different wavelength. The application of our method to visible-NIR observations remains as a future project.