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Adjustable focus eyeglasses are eyeglasses with an adjustable focal length. They compensate for refractive errors (such as presbyopia) by providing variable focusing, allowing users to adjust them for desired distance or prescription, or both. Current bifocals and progressive lenses are static, in that the user has to change their eye position ...
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 ...
The lens of the eye is the most obvious example of gradient-index optics in nature. In the human eye, the refractive index of the lens varies from approximately 1.406 in the central layers down to 1.386 in less dense layers of the lens. [1] This allows the eye to image with good resolution and low aberration at both short and long distances. [2]
Progressive lenses are corrective lenses used in eyeglasses to correct presbyopia and other disorders of accommodation. They are characterised by a gradient of increasing lens power, added to the wearer's correction for the other refractive errors. The gradient starts at the wearer's distance prescription at the top of the lens and reaches a ...
Bifocals. A bifocal lens with areas of differing magnification. Bifocals with separate lenses. In this case, the Swedish ethnologist Jan-Öjvind Swahn [ sv]. Bifocals are eyeglasses with two distinct optical powers. Bifocals are commonly prescribed to people with presbyopia who also require a correction for myopia, hyperopia, and/or astigmatism .
Scientist using an optical microscope in a laboratory. The optical microscope, also referred to as a light microscope, is a type of microscopethat commonly uses visible lightand a system of lensesto generate magnified images of small objects. Optical microscopes are the oldest design of microscope and were possibly invented in their present ...
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