text: TITLE       = "Infinite telecentric 4f telescope"
  DESCRIPTION = """ Two lenses separated by the sum of their focal lengths is a
  telecentric telescope, or a 4f-system.  If we set up the path from the focal
  plane of the first lens to the focal plane of the second lens (as is done
  here), then the system has a transfer matrix that is "imaging", with B=0. This
  can be checked with path.isImaging.
  
  Raytracing defines System4f() to conveniently put two lenses
  in this configuration: System4f(lens1, lens2).
  """
  
  from raytracing import *
  
  def exampleCode(comments=None):
      path = ImagingPath()
      path.label = TITLE
      path.append(Space(d=50))
      path.append(Lens(f=50))
      path.append(Space(d=100))
      path.append(Lens(f=50))
      path.append(Space(d=50))
      print("Transfer matrix of system is imaging (i.e. B=0): {0}".format(path.isImaging))
      path.display(comments=comments)
  
  if __name__ == "__main__":
      exampleCode()
  