In a recent Design Note, we noted the unique ability of OSLO SIX to perform true global optimization using Adaptive Simulated Annealing. In many practical design tasks, the interest is not so much to find a global optimum as it is to find several good solutions that are suitable as starting points for final optimization. We call algorithms that do this multiple solution generators. Multiple solution generators provide a useful tool in many aspects of optical design. Several approaches have been used for this purpose, including the beta-gamma theory of T. Smith used Genesee's Synthesis program, Shafer's BUSD (Blow-Up-Settle-Down) method, based on non-linearities found in damped-least-squares (DLS) iteration, and Isshiki's Global Explorer, based on an escape function that can be added to an error function to prevent stagnation of DLS. The Global Explorer method, implemented in CCL, has been added to OSLO SIX, starting with Rev. 5.4.
Global Explorer uses OSLOs damped least squares routines for optimization, but provides a special escape function that permits it to search for alternate design forms, once a local minimum has been achieved. Implemented in CCL, Global Explorer is supplied with source code, permitting users to modify it and experiment with new methods in this interesting area of optical design research. The general principles and some examples of the use of Global Explorer are described in the Beginner's Guide to Global Explorer.