1. A night vision instrument having a first imaging system of field-glass type provided with a first entrance aperture at a front side end and an ocular at the other end for viewing a scene therethrough, and a second imaging system provided at its front end with a second entrance aperture larger than the first, and at the other end thereof a concave mirror for imaging light-rays from the scene, a light intensifier having an entrance surface for projecting a weak-light image thereto and an opposite exit surface for obtaining an intensified image of said weak-light image, and mirror means for projecting said intensified image into the ray-path of said first imaging system for viewing by said ocular of said first imaging system, wherein said concave mirror faces said entrance surface of said light intensifier, said exit surface thereof facing said second entrance aperture, and said mirror means catching said intensified image from the front side of said image intensifier.