Optical observation and measurement instruments

Of our five senses, vision is the one that enables us to perceive our immediate or distant environment from a distance, without the need for a material medium. In fact, the emitter of light needs no material contact with the eye to bring it a sensation; electromagnetic radiation, the carrier of information, is capable of traversing spaces empty of matter, even over astronomical distances.

Subjective observation already provides a whole range of qualitative knowledge. But vision can also be used to acquire quantitative data: reading the deviation of a pointer in front of a scale, a number displayed on a dial, a table of numbers, graphs, coded synthetic images, etc.

However, like each of our senses, vision has its limits. The role of optical instruments is to bring objects invisible to the naked eye into conditions exploitable by vision, by moving them closer or further away, by enlarging or reducing them, by circumventing opaque obstacles, by increasing or decreasing the level of light, or even by changing the frequency range of their radiation, as well as by storing and then restoring image data on photographic, magnetic, computer or other media.