Dioptre

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A dioptre (English spelling) or diopter (American spelling) is an optical power measurement unit of a lens or a curved mirror, which is the exact opposite of the focal length measured in meters. (1 dioptre = 1 m ^-1.) Thus a unit of mutuality. For example, a 3-dioptre lens carries a parallel ray of light to focus on ^//₃ meters. Flat windows have zero optical powers of diopters, and do not merge or deviate light.

Dioptres are also sometimes used for other reciprocity from a distance, especially radius curvature and optical beam vergence. This use was proposed by the French ophthalmologist Ferdinand Monoyer in 1872, based on the earlier use of the term dioptrice by Johannes Kepler.

The main benefit of using optical power rather than focal length is that the lensmaker equation has object distance, image distance, and focal length all as reciprocity. A further benefit is that when relatively thin lenses are placed close together, their strength will increase. Thus, the 2.0-dioptre thin lens placed close to a 0.5-dioptre thin lens produces almost the same focal length as a single 2.5-dioptre lens.

Although the dioptre is based on an SI-metric system it is not yet included in the standard so there is no international name or abbreviation for this measurement unit - in an international unit system, this unit for optical power needs to be explicitly set as an upside-down meter (m ^-1). But most languages â€‹â€‹have borrowed their real names and some national standardization bodies such as DIN specify unit names (dioptrie, dioptria, etc.) and unit units of "dpt" symbols.

Video Dioptre

In vision correction

The fact that optical power around additives enables an eye care professional to prescribe corrective lenses as a simple correction for optical power of the eye, rather than doing a detailed analysis of the entire optical system (eye and lens). Optical power can also be used to adjust basic recipes for reading. So an eye care professional, having determined that shortsighted people need a basic correction, for example, -2 dioptres to restore normal sight distances, may then make further recipes of 'add 1' to read, to make up for the lack of accommodation (ability to change focus). This is equivalent to saying that a 1-dioptre lens is prescribed for reading.

In humans, the total optical strength of the relaxed eye is about 60 diopters. The cornea accounts for about two-thirds of this bias strength (about 40 diopters) and the crystalline lens accounts for the remaining one-third (about 20 diopters). In focusing, the ciliary muscle contract to reduce tension or stress is transferred to the lens by suspensory ligaments. This results in an increase in the convexity of the lens which in turn increases the optical power of the eye. The amplitude of the accommodation is about 15 to 20 diopters at a very young age, decreasing to about 10 diopters at age 25, and about 1 dioptre above the age of 50.

The convex lens has a positive dioptric value and is commonly used to repair hyperopia (farsightedness) or to allow people with presbyopia (late age limited accommodation) to read at close range. Concave lenses have negative dioptic values â€‹â€‹and are generally true myopia (farsightedness). Typical glasses for mild myopia will have a strength between 0.00 to -3.00 diopters, whereas over the counter reading glasses will be rated at 1.00 to 3.00 dioptres. The ophthalmologist usually measures the refractive error using the lenses assessed in 0.25 dioptres steps.

Maps Dioptre

Curvature

Dioptre can also be used as a measurement of the same curvature as the inverse of the radius measured in meters. For example, a circle with a 1/2 meter radius has a curvature of 2 dioptres. If the curvature of the lens surface is C and the refraction index is n , its optical power is? = ( n - 1) C . If both surfaces of the lens are curled, consider their curves as positive against the lens and add. This will give a less precise result, as long as the thickness of the lens is much less than the radius of curvature of one of the surfaces. For a mirror, its optical power? = 2 C .