An optical system operable to transmit an energy flux is described. A first substantially spherical lens includes first and second substantially hemispherical portions joined at an interface. The interface includes a partially reflective material on a first substantially planar surface of at least one of the first and second hemispherical portions. A second lens has a convex surface and a second substantially planar surface. A portion of the second substantially planar surface of the second lens is secured to the first lens to form an optical axis. The first and second lenses are operable to transmit a first portion of the energy flux along the optical axis. The partially reflective surface is operable to reflect a second portion of the energy flux at an angle to the optical axis.