Chromatic Aberration, Field Curvature, Distortion, Astigmatism
This article is an introduction to different kinds of optical aberrations including Chromatic Aberration, Field Curvature, Distortion, and Astigmatism, the basic definition and the principle of, and how to correct these aberrations are explained in the text.
Harmonic Generation
This article explained what is harmonic generation (or frequency conversion), which is the result of the utilization of nonlinear optical effects, and other contents including type I, type II phase matching.