Search results
Results from the WOW.Com Content Network
t. e. PRISM is a code name for a program under which the United States National Security Agency (NSA) collects internet communications from various U.S. internet companies. [1] [2] [3] The program is also known by the SIGAD US-984XN. [4] [5] PRISM collects stored internet communications based on demands made to internet companies such as Google ...
A pinhole occluder is an opaque disk with one or more small holes through it, used by ophthalmologists, orthoptists and optometrists to test visual acuity. The occluder is a simple way to focus light, as in a pinhole camera, temporarily removing the effects of refractive errors such as myopia. Because light passes only through the center of the ...
Eyeglass prescription. An eyeglass prescription is an order written by an eyewear prescriber, such as an optometrist, that specifies the value of all parameters the prescriber has deemed necessary to construct and/or dispense corrective lenses appropriate for a patient. If an eye examination indicates that corrective lenses are appropriate, the ...
An Abbe–Koenig prism is a type of reflecting prism, used to invert an image (rotate it by 180°). They are commonly used in binoculars and some telescopes for this purpose. The prism is named after Ernst Abbe and Albert Koenig . The prism is made from two glass prisms, which are optically cemented together to form a symmetric, shallow Vee ...
A reflex finder is a viewfinder system with a mirror placed behind a lens. The light passing through the lens is reflected by the mirror to a focusing screen, usually ground glass. The image formed on this ground glass can be observed directly, giving a waist-level reflex finder, or through a redressing optical device (set of mirrors or prism ...
Corrective lenses. A corrective lens is a lens worn on or before the eye. They are used to treat myopia, hypermetropia, astigmatism, and presbyopia .
Šidák correction for t-test. One of the application of Student's t-test is to test the location of one sequence of independent and identically distributed random variables. If we want to test the locations of multiple sequences of such variables, Šidák correction should be applied in order to calibrate the level of the Student's t-test.
Vertex distance is the distance between the back surface of a corrective lens, i.e. glasses (spectacles) or contact lenses, and the front of the cornea. Increasing or decreasing the vertex distance changes the optical properties of the system, by moving the focal point forward or backward, effectively changing the power of the lens relative to ...