correcting lenses
31Astigmatic — Referring to astigmatism or a person with astigmatism, a common form of visual impairment in which part of an image is blurred, due to an irregularity in the curvature of the front surface of the eye, the cornea. The curve of the cornea is shaped …
32Dialyte lens — A dialyte lens (sometimes called a dialyt[1]) is a compound lens design that corrects optical aberrations where the lens elements are widely air spaced.[2] The design is used to save on the amount of glass used for specific elements or where… …
33Newtonian telescope — The Newtonian telescope is a type of reflecting telescope invented by the British scientist Sir Isaac Newton (1642–1727), using a concave primary mirror and a flat diagonal secondary mirror. Newton’s first reflecting telescope was completed in… …
34Visual acuity — 20/15 and 20/15 vision redirect here. For other uses, see 2020 (disambiguation). Typical Snellen chart used for visual acuity testing. Visual acuity (VA) is acuteness or clearness of vision, which is dependent on the sharpness of the retinal… …
35Metamaterial antenna — This Z antenna tested at the National Institute of Standards and Technology is smaller than a standard antenna with comparable properties. Its high efficiency is derived from the Z element inside the square that acts as a metamaterial, greatly… …
36Adaptive optics — (AO) is a technology used to improve the performance of optical systems by reducing the effects of rapidly changing optical distortion. It is used in astronomical telescopes and laser communication systems to remove the effects of atmospheric… …
37Reflecting telescope — 24 inch convertible Newtonian/Cassegrain reflecting telescope on display at the Franklin Institute. A reflecting telescope (also called a reflector) is an optical telescope which uses a single or combination of curved mirrors that reflect light… …
38What's Happening!! — Infobox Television show name = What s Happening!! caption = What s Happening!! opening titles from the show s third season format = Sitcom runtime = 30 Minutes creator = Eric Monte executive producer = Bernie Orenstein Saul Turteltaub Bud Yorkin… …
39Nikon D1 — Type Digital single lens reflex camera Sensor CCD, 23.7 × 15.6 mm DX format, 1.5× FOV crop Maximum …
40astigmatism — /euh stig meuh tiz euhm/, n. 1. Also called astigmia /euh stig mee euh/. Ophthalm. a refractive error of the eye in which parallel rays of light from an external source do not converge on a single focal point on the retina. 2. Optics. an… …
