Search results
Results from the WOW.Com Content Network
An example of mildly elevated ST segments in V1 to V3 that are concave down An ST elevation is considered significant if the vertical distance inside the ECG trace and the baseline at a point 0.04 seconds after the J-point is at least 0.1 mV (usually representing 1 mm or 1 small square) in a limb lead or 0.2 mV (2 mm or 2 small squares) in a ...
For optics like convex lenses, the converging point of the light exiting the lens is on the input side of the focal plane, and is positive in optical power. For concave lenses, the focal point is on the back side of the lens, or the output side of the focal plane, and is negative in power.
This list covers optical lens designs grouped by tasks or overall type. The field of optical lens designing has many variables including the function the lens or group of lenses have to perform, the limits of optical glass because of the index of refraction and dispersion properties, and design constraints including realistic lens element center and edge thicknesses, minimum and maximum air ...
A lens with one convex and one concave side is convex-concave or meniscus. Convex-concave lenses are most commonly used in corrective lenses, since the shape minimizes some aberrations. For a biconvex or plano-convex lens in a lower-index medium, a collimated beam of light passing through the lens converges to a spot (a focus) behind
Like other lenses for vision correction, aspheric lenses can be categorized as convex or concave. Convex aspheric curvatures are used in many presbyopic vari-focal lenses to increase the optical power over part of the lens, aiding in near-pointed tasks such as reading. The reading portion is an aspheric "progressive add".
However, for the record: the first autofocus lens for a still camera was the Konishiroku Konica Hexanon 38mm f/2.8 [171] built into the Konica C35 AF (1977, Japan) 35mm point-and-shoot; the first autofocus lens for an SLR camera was the unnamed 116mm f/8 [172] built into the Polaroid SX-70 Sonar (1978, USA) instant film SLR; the first ...
Other lenses for the Contax included the Biotar, Biogon, Orthometar, and various Tessars and Triotars. The last important Zeiss innovation before the Second World War was the technique of applying anti-reflective coating to lens surfaces invented by Olexander Smakula in 1935. [8] A lens so treated was marked with a red "T", short for "Transparent".
Real images can be produced by concave mirrors and converging lenses, only if the object is placed further away from the mirror/lens than the focal point, and this real image is inverted. As the object approaches the focal point the image approaches infinity, and when the object passes the focal point the image becomes virtual and is not ...