STUDIES ON HIGH-RESOLUTION IMAGING WITH TWO-COLOR SPECKLEGRAMS

由于地球大气湍流的影响，从地面观测到的恒星天体短曝光图像呈现出斑点状图案。然而，这样的散斑图包含了望远镜衍射极限分辨率的物体信息。散斑干涉法是一种除自适应光学外获得高分辨率图像的简单方法。当两个波长相差很大的散斑图之间有很强的相关性时，在一个波长上参考另一个波长上的散斑图进行高分辨率成像是可行的，此时天体是点源或有参考星星，本研究的目的是通过分析两个波长相差很大的散斑图，建立双色散斑图高分辨率成像方法。我们在日本国立天文台冈山天体物理观测站的90 cm或188 cm望远镜上安装了双色散斑照相机，对卡佩拉和织女星进行了观测，探测波长为短波长400 nm或450 nm，长波长800 nm。这两个波长对应于可见光区的极值，比值约为2。对一个波长的散斑图进行移位相加操作，可得到另一个波长的重复再现像。结果表明，利用一个波长的散斑图再现另一个波长的像优于利用散斑图重心叠加产生的伪长曝光像。这表明，高分辨率成像是可能的，通过利用散斑图在不同的波长。我们的方法的应用可见近红外观测仍然是一个未来的项目。

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.