Abstract: A filtering apparatus 30 passes an incident beam of light through a first lens having a first focal length, causing the incident beam of light 32 to be focussed, and then passes the incident beam of light through a pinhole 36 having an opening of a predetermined size. In accordance with one aspect of the invention, the pinhole 36 is spaced from the first lens 34 by a distance which is greater than, or less than, but not equal to the lens' focal length wherein only a portion of the incident beam of light passes through the opening of the pinhole 36. In the illustrated embodiment, the pinhole 36 has a size which is significantly larger than the nominal diffraction limited spot size of the first lens 34. The incident beam of light which passes through the pinhole is then directed toward a second lens 38 having a second focal length. In a preferred embodiment, the second lens 38 is spaced from the pinhole 36 by a distance substantially equal to the second lens' focal length.