ABSTRACT
The majority of optical systems consist of a number of spaced elements, which individually may not be thin or simple. Treatment of refraction by such a thick or compound lens for simple calculations would be lengthy using the procedures of Chapter 6, although this is done routinely in ray tracing for lens design. Fortunately, the formulae of paraxial geometric optics or Gaussian optics are found to hold for thick lenses, provided that measurements of conjugate and focal distances are made from the appropriate transverse cardinal planes and associated cardinal points on the optical axis. There are six cardinal planes in three conjugate pairs (see Figure 7.1).
