甚长基线干涉测量（VLBI）的出现为天文学研究提供了很高的角分辨率（空间分辨率），为人们认识和理解活动星系核（AGN）现象起到不可替代的作用。毫米波VLBI以其独有的优势正在成为天体物理学研究中最有效的研究工具之一。本文简要回顾了射电干涉测量的发展历程，重点介绍了毫米波VLBI的发展历史与现状，及其在活动星系核研究中的重要作用。展望了未来几年随着大口径毫米波段望远镜以及望远镜阵列的加入，毫米波VLBI的发展和应用前景。
Very Long Baseline Interferomety (VLBI) is a high-resolution imaging technique in radio astronomy. It has made substantial contribution to our understanding of Active Galactic Nuclei (AGN). The progress in VLBI is reviewed focusing on the development at millimeter wavelengths and its applications to AGN studies. Extending this technique to millimeter wavelengths, so-called mm-VLBI, leads to a unique opportunity to directly probe the central regions of AGN with the highest angular resolution in astronomy. Direct imaging of the jet innermost regions is indispensable for answering a number of unresolved fundamental questions regarding the jet formation, acceleration, and collimation. It is also a key to understand how the gravitational effects and magnetic fields (through full polarimetric VLBI observations) play the role in the vicinity of Super Massive Black Holes (SMBH). Such kind of studies are not possible at centimeter wavelengths due to the self-absorption, opacity, Faraday depolarization and scattering (in the case of Sgr A*) effects. In addition, millimeter-VLBI observations also open windows to study new species of spectral lines with unprecedented angular resolutions. The present challenges of millimeter VLBI are explained and a brief developing history is then described. Recent technical development allows imaging of hundreds of sources at 86GHz with high dynamic range. At even higher frequencies, studies are at present limited to pilot experiments, but have shown the detectability of brightest AGN and the existence of event-horizon-scale structures. These studies provide us with direct insights into black hole and relativistic jet physics. The future potential for improvement in mm-VLBI detection sensitivity is summarized. The characteristics for those radio telescopes and interferometer arrays, which are likely available in the next few years for global VLBI at short millimeter wavelengths (≤1.3mm) are presented. With the addition of these new instruments, a detailed imaging of nearby SMBHs (e.g. Sgr A*, M87) and answer to the open question of jet formation can be prospected.
