- [1)] Find the general equation describing layer behavior (e.g., equation (5)).
- [2)] Divide the variables that occur in the general layer equation
into three classes:
- [2a)] The
**layer**parameters are assumed given (e.g., the*k*_{i}). - [2b)] The
**constant**parameters have the same value for all layers in the stack (e.g.,*F*). - [2c)] The
**additive**parameters sum through the stack (e.g., the ).

- [2a)] The
- [3)] Rewrite the equation from step 1 so it has the form
(12) - [4)] Identify the term ``''
as an alternative
*layer-group*representation of the layer parameters (e.g., the 1/*k*_{i}). To find the homogeneous equivalent of a stack, convert from the standard representation to the layer group, sum, and convert back.

11/17/1997