How many times have you heard the phrase, "Do the best you can!"? If you are old and experienced (i.e., wary), you will probably snap back with "What does that mean?" "Oh, diffraction limited will do," your customer
will reply with a condescending air, and hurry off. It is sad, but so often true, that the optical designer (or project engineer) finds himself/herself with back firmly affixed against the proverbial wall as a result of this simple, preliminary, and often only specification. The odds are that "the best" is usually too good (i.e., costs too much and/or takes too long) or is not good enough (i.e., functions poorly).
by Valerie Olson