日冕仪（Coronagraph）是法国默东天文台的贝尔纳·费迪南·李奥在1930年发明的一种观测设备，设计当时主要用来研究太阳的日冕和日珥的形态及光谱变化。

Lyot的构想灵感源由于日全蚀：一般的时候，因为太阳本身太亮了，我们很难观测到相对较暗（与太阳相比约是一百万分之一亮度）的日冕部分；但在日全蚀，月亮挡住了太阳圆盘大部份的面积，使得周围黯淡的日冕及色球层可以显现出来，就可以进行观测。那这样的话，何不做一个人工「月亮」，挡在望远镜和太阳中间，把太阳光遮掉，不就可以观测到日冕了?这就是最初的日冕仪构想，使用档板遮掉太阳光，就可以观测到太阳周围的日冕等区域。

A coronagraph is a telescopic attachment designed to block out the direct light from a star so that nearby objects – which otherwise would be hidden in the star's bright glare – can be resolved. Most coronagraphs are intended to view the corona of the Sun, but a new class of conceptually similar instruments (called stellar coronagraphs to distinguish them from solar coronagraphs) are being used to find extrasolar planets and circumstellar disks around nearby stars.