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Crown glass is a type of optical glass used in lenses and other optical components. It has relatively low refractive index (≈1.52) and low dispersion (with Abbe numbers between 50 and 85). Crown glass is produced from alkali-lime silicates containing approximately 10% potassium oxide and is one of the earliest low dispersion glasses .
A concave lens of flint glass is commonly combined with a convex lens of crown glass to produce an achromatic doublet lens because of their compensating optical properties, which reduces chromatic aberration (colour defects).
A burning apparatus consisting of two biconvex lens. A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction.A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (elements), usually arranged along a common axis.
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 ...
Normal lens: angle of view of about 50° (called normal because this angle considered roughly equivalent to human vision [118]) and a focal length approximately equal to the diagonal of the film or sensor. [119] Wide-angle lens: angle of view wider than 60° and focal length shorter than a normal lens. [120]
A pair of contact lenses, positioned with the concave side facing upward. A corrective lens is a transmissive optical device that is worn on the eye to improve visual perception. The most common use is to treat refractive errors: myopia, hypermetropia, astigmatism, and presbyopia.
Léon Foucault developed a catadioptric microscope in 1859 to counteract aberrations of using a lens to image objects at high power. [2] In 1876 a French engineer, A. Mangin, invented what has come to be called the Mangin mirror, a concave glass reflector with the silver surface on the rear side of the glass. The two surfaces of the reflector ...
Moulding concave forms with small centre thickness is difficult due to sticking of the moulded part to the mould occurring as a result of the different thermal expansion coefficients. Furthermore, it is recommended to avoid undercuts and sharp edges. For the lens design it should be considered that the lens has to be mountable in measurement ...