All optical devices, regardless of their specifics and purpose, necessarily have one common physical characteristic, which is called "resolution". This physical property is decisive for all optical and optical-measuring instruments without exception. For example, for a microscope, the most important parameter is not only the magnifying power of its lenses, but also the resolution, on which the quality of the image of the object under study directly depends. If the design of this device is not capable of providing a separate perception of the smallest details, then the resulting image will be of poor quality even with a significant increase.
The resolution of optical instruments is a value that characterizes their ability to distinguish the smallest individual detailsobserved or measured objects. The resolution limit is the minimum distance between adjacent parts (points) of an object, at which their images are no longer perceived as separate elements of the object, merging together. The smaller this distance, the higher the resolution of the device.
The reciprocal of the resolution limit is a measure of resolution. This most important parameter determines the quality of the device and, accordingly, its price. Due to the diffractive property of light waves, all images of small elements of an object look like bright spots surrounded by a system of concentric interference circles. It is this phenomenon that limits the resolution of any optical devices.
According to the theory of the 19th century English physicist Rayleigh, the image of two nearby small elements of an object can still be distinguished if their diffraction maximum coincides. But even this resolution has its limits. It is determined by the distance between these smallest details of objects. The resolution of a lens is usually determined by the maximum number of separately perceived lines per millimeter of image. This fact was established empirically.
The resolution of devices decreases in the presence of aberrations (deviations of the light beam from a given direction) and various errors in the manufacture of optical systems, which increases the dimensions of diffraction spots. SoThus, the smaller the size of the diffraction spots, the higher the resolution of any optics. This is an important indicator.
The resolution of any optical device is evaluated by its hardware features, reflecting all the factors that affect the quality of the image provided by this device. Such influencing factors, of course, should first of all include aberration and diffraction - the rounding of obstacles by light waves and, as a result, their deviation from a rectilinear direction. To determine the resolution of various optical instruments, special transparent or opaque test plates with a standard pattern, called worlds, are used.
