Thin film coatings are universal on optical components such as displays, lenses, mirrors, cameras and windows, and serve a variety of functions such as antireflection, high reflection, spectral filtering, etc. Designs can be as simple as a single layer dielectric for antireflection effects or very complex with hundreds of layers for producing elaborate spectral filtering effects. Starting from basic principles of electromagnetics, design techniques are progressively introduced towards more intricate optical filter designs, numerical optimization techniques and production methods, as well as emerging areas such as phase change materials and metal film optics. Worked examples, Python computer codes, and instructor problem sets are included.