Introduction

Most of the material presented in the earlier chapters of this book is associated with achieving the optimum lens design. There has been a lot said over the years about lens design optimization theory and algorithms, global search algorithms, aberration theory, and other related topics. These are all directed toward achieving the optimum lens performance for what we sometimes call the "paper design." The performance of the paper design is that of the design prescription, or the theoretical design, with the effects of absolutely no manufacturing errors of any kind included. While the performance of the paper design is indeed important, the effects of real-world hardware-related manufacturing errors and tolerances can and will, by definition, alter and degrade the level of performance from the theoretical paper design performance. We often find that the degradations due to manufacturing errors can many times even surpass the image degradations of the nominal design itself.

Tolerancing is the science (and art, to some extent) of distributing and error budgeting the manufacturing tolerances of all optical and opto-mechanical components and dimensions throughout the system to assure that your system will meet its required level of optical performance at a reasonable cost.

Unfortunately, there is little, if any, direct correlation between the performance of the paper design and the robustness or insensitivity of the design with respect to the level of manufacturing errors or tolerances. For example, we may have a design where steep bendings and high angles of incidence has allowed for the...