Research for Diffraction Limited Imaging with Large Optical Telescope

在这项研究中，我们发展了一种使用非冗余孔径掩模(NRM)的孔径合成方法，用于在大型光学望远镜上获得衍射极限图像。1988年，我们搭建了一个数据采集系统，研究了二维NRM的设计方法，并进行了基本的光学模拟。1989年，在这些结果的基础上，利用数据采集系统的数据，我们在国家天文台Dodaira天文台用91厘米望远镜观测了单星和双星。通过这些观测，我们发现日本的大气波动非常严重，必须要有一个图像稳定系统。因此，在1990年，我们开发了一种具有图像稳定功能的孔径掩模系统。利用日本天文台冈山天体物理观测站188 cm望远镜的NRM观测系统，证实了成像稳定功能的良好响应，并获得了大量的衍射极限成像的基础数据。通过调查，我们得到了以下结果：1.日本的相干带半径小于3厘米。由于NRM的子孔径数目较少，子孔径半径等于相干贴片的NRM的总孔径面积很小，因此需要对弱目标使用冗余度小的掩模。在基线较长的情况下，由于子孔径之间的延迟差较大，能见度幅度严重下降。这种影响的一部分可以通过图像稳定系统来抵消。然而，在视力不佳的情况下，希望使用简单的自适应光学。

In this research, we have developed an aperture synthesis method with a non-redundant aperture mask (NRM) to obtain diffraction limited images with a large optical telescope. In 1988, we constructed a data acquisition system, investigated the design method of 2-dimensional NRM, and conducted a fundamental optical simulation. In 1989, based on these results and using the data using the data acquisition system, we observed single stars and binaries with the 91 cm telescope at Dodaira Astronomical Observatory, National Astronomical Observatory (NAO). From these observations, we found that the atmospheric fluctuations are very severe in Japan and an image stabilizing system must be required. Thus, in 1990, we developed an aperture masking system with an image stabilizing function. Using the system for NRM observations with the 188 cm telescope at Okayama Astrophysical Observatory, NAO, we confirmed good response of the imaging stabilizing function and obtained a lot of fundamental data for diffraction limited imaging. From our investigations, we obtained following results :1. The radius of the coherence patch is less than 3 cm in Japan. Since the number of sub-apertures of NRM is small, total aperture area of NRM of which sub-aperture radius is equal to that of coherence patch is very small Therefore, it is required to use the mask with small redundancy for weak objects.2. At longer baselines, visibility amplitude decreases severely, because the delay difference between sub-apertures is large. Some portion of this effect can be canceled out by an image stabilizing system. In the case of bad seeing, however, it is desired to use a simple adaptive optics.