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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).
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 ...
Concerning the curvature of the lens elements, the following statements can be drawn: Acceptable lens shapes are most bi-convex, plano-convex and mild meniscus shapes. Not unacceptable but hard to mould are bi-concave lenses, steep meniscus lenses, and lenses with severe features (e.g. a bump on a convex surface). In general, plano-curved ...
Most lenses are spherical lenses: their two surfaces are parts of the surfaces of spheres. Each surface can be convex (bulging outwards from the lens), concave (depressed into the lens), or planar (flat). The line joining the centres of the spheres making up the lens surfaces is called the axis of the lens. Typically the lens axis passes ...
The lens is moved until a sharp image is formed on the screen. In this case 1 / u is negligible, and the focal length is then given by . Determining the focal length of a concave lens is somewhat more difficult. The focal length of such a lens is defined as the point at which the spreading beams of light meet when they are extended ...
Very-large-aperture lenses designed to be useful in very low light conditions with apertures ranging from f/1.2 to f/0.9 are generally restricted to lenses of standard focal length because of the size and weight problems that would be encountered in telephoto lenses and the difficulty of building a very wide aperture wide angle lens with the ...
The focal length f is considered negative for concave lenses. Incoming parallel rays are focused by a convex lens into an inverted real image one focal length from the lens, on the far side of the lens. Incoming parallel rays are focused by a convex lens into an inverted real image one focal length from the lens, on the far side of the lens
Ibn al-Haytham (Alhacen) wrote about the effects of pinhole, concave lenses, and magnifying glasses in his 11th century Book of Optics (1021 CE). [ 46 ] [ 48 ] [ 49 ] The English friar Roger Bacon , during the 1260s or 1270s, wrote works on optics, partly based on the works of Arab writers, that described the function of corrective lenses for ...