This is a long focal length concave parabolic mirror that produces an image between the object and the focal point of the mirror for the setup photographed. The central ray passes through a half-silvered mirror which deflects half of the light to the tip of the object arrow. The upper mirror can be rotated to create any of the three principal rays. A convex lens at the left keeps the light ray narrow.
The object can be moved within the focal point of the mirror to produce an enlarged virtual image behind the mirror.