The emergence of optical dimensional methods has brought new approaches and new perspectives in experimental solid mechanics. These measurement systems are very different from the classical systems such as strain gauges, extensometers and displacement sensors. The classical systems measure local information, are in direct contact with the structure but benefit from a standardization which allows them to be favoured by the industry. Systems based on optical methods, and in particular by stereo-correlation of digital images, the grid method, the image correlation method, interferometry, the infrared method and the thermographic method offer field measurements, without contact with the structure. In fact, these techniques allow access to three-dimensional displacements and deformations at any point on the surface of the structure being evaluated. These new means of measurement, due to the great wealth of information (qualitative and quantitative aspects) that they provide, renew many aspects of experimental mechanics and are favoured by researchers to complete.