correcting lenses
41radial keratotomy — Ophthalm. a surgical technique for correcting nearsightedness by making a series of spokelike incisions in the cornea to change its shape and focusing properties. [1975 80; KERATO + TOMY] * * * ▪ surgical procedure surgical procedure to… …
42Refraction — In ophthalmology, the bending of light that takes place within the human eye. Refractive errors include nearsightedness (myopia), farsightedness (hyperopia), and astigmatism. Lenses can be used to control the amount of refraction, correcting… …
43Microscopy — is the technical field of using microscopes to view samples and objects that cannot be seen with the unaided eye (objects that are not within the resolution range of the normal eye). There are three well known branches of microscopy, optical,… …
44Parabolic reflector — Parallel waves coming in to a parabolic mirror are focused at a point F A parabolic reflector (or dish or mirror) is a reflective device used to collect or project energy such as light, sound, or radio waves. Its shape is that of a circular… …
45Optical disc drive — A CD/DVD ROM Drive A Blu ray (BD RE DL) writer tray in a Sony Vaio E series laptop …
46Bernhard Schmidt — Bernhard Woldemar Schmidt (March 30, 1879 ndash; December 1, 1935) was an Estonian Swede optician who spent his adult life in Germany. In 1930 he invented the Schmidt telescope which corrected for the optical errors of spherical aberration, coma …
47Perspective control — is a procedure for composing or editing photographs to better conform with the commonly accepted distortions in constructed perspective. The control would: * make all lines, which are vertical in reality, vertical on the image. This includes… …
48Weak gravitational lensing — While the presence of any mass bends the path of light passing near it, this effect rarely produces the giant arcs and multiple images associated with strong gravitational lensing. Most lines of sight in the universe are thoroughly in the weak… …
49range finder — any of various instruments for determining the distance from the observer to a particular object, as for sighting a gun or adjusting the focus of a camera. Also, rangefinder. [1870 75] * * * Instrument used to measure the distance from the… …
50rare-earth element — /rair errth /, Chem. any of a group of closely related metallic elements, comprising the lanthanides, scandium, and yttrium, that are chemically similar by virtue of having the same number of valence electrons. Also called rare earth metal. [1955 …
