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In some lenses, the curved surfaces are replaced with flat surfaces, with a different angle in each section. Such a lens can be regarded as an array of prisms arranged in a circular fashion with steeper prisms on the edges and a flat or slightly convex center. In the first (and largest) Fresnel lenses, each section was actually a separate prism.
This page provides a list of the oldest brands and companies operating only in the eyewear manufacturing business to date and in any country. "Eyewear", although a relatively modern terminology, refers to the category of all items and accessories worn over the eyes for fashion adornment, protection against the environment and medical issues, including glasses (also called eyeglasses or ...
A Luneburg lens (original German Lüneburg lens) is a spherically symmetric gradient-index lens. A typical Luneburg lens's refractive index n decreases radially from the center to the outer surface. They can be made for use with electromagnetic radiation from visible light to radio waves . For certain index profiles, the lens will form perfect ...
24 November 2020. Rodenstock GmbH ( German pronunciation: [ˈʁoːdn̩ʃtɔk]) is a German manufacturer of ophthalmic lenses and frames for eyeglasses. The company, which was founded by Thuringian Josef Rodenstock in 1877, is headquartered in Munich. [1]
The Fresnel number is a useful concept in physical optics. The Fresnel number establishes a coarse criterion to define the near and far field approximations. Essentially, if Fresnel number is small – less than roughly 1 – the beam is said to be in the far field. If Fresnel number is larger than 1, the beam is said to be near field.
Sinar Photography AG is a Swiss company based in Zürich manufacturing specialized high-resolution view cameras for studio, reproduction, landscape and architecture photography. Sinar's view-cameras allow both the lens and the film back or sensor back to move in rotation or linearly in any direction (up/down, left/right, front back linearly ...
The aim of an accurate intraocular lens power calculation is to provide an intraocular lens (IOL) that fits the specific needs and desires of the individual patient. The development of better instrumentation for measuring the eye's axial length (AL) and the use of more precise mathematical formulas to perform the appropriate calculations have significantly improved the accuracy with which the ...
Lens clock. A lens clock is a mechanical dial indicator that is used to measure the dioptric power of a lens.It is a specialized version of a spherometer.A lens clock measures the curvature of a surface, but gives the result as an optical power in diopters, assuming the lens is made of a material with a particular refractive index.
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