focusing (concave) mirrors

Focusing (concave) mirrors are characterized by one concave surface with a high reflection coating that allows for focusing of the light beam. Most common coatings include Al, Au or Ag. Mirrors are found most useful when refractive optics cannot be used due to extremely high energy light beam in lasers or condition for no chromatic aberration in a broad spectral range. Another common use case is tightness optimization of the optical system.

Concave mirrors can be used similar to focusing lenses and can create:
imaginary or real,
reversible or simple,
decreased, increased or equal to object images
depending on: radius of curvature of concave surface and distance from object to mirror surface.