Book excerpt: Photonic Instrumentation: Sensing and Measuring with Lasers is designed as a source for university-level courses covering the essentials of laser-based instrumentation, and as a useful reference for working engineers. Photonic instruments have very desirable features like non-contact operation and unparalleled sensitivity. They have quickly become a big industrial success, passing unaffected through the bubble years and, not any less important, well-established methods in measurement science. This book offers coverage of the most proven instruments, with a balanced treatment of the optical and electronic aspects involved. It also attempts to present the basic principles, develop the guidelines of design and evaluate the ultimate limits of performances set by noise. The instruments surveyed include: alignment instruments, such as wire diameter and particle size analyzers, telemeters, laser interferometers and self-mixing interferometers, and speckle pattern instruments, laser doppler velocimeters, gyroscopes, optical fiber sensors and quantum sensing. A few appendices offer convenient reference material for key principles on lasers, optical interferometers, propagation, scattering and diffraction.