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Adjustable focus lenses, like single-focus lenses, also reduce image-jump and spatial distortion in the field of view associated with traditional multi-focal lenses. Additionally, the ideal near-vision correction can be achieved with precision, because the variable lenses emulate the focusing action of the youthful (non-presbyopic) eye.
The add segment of the lens for near vision is the D-shaped area. A bifocal is a lens with two sections, separated by a line (see image to the right). Generally, the upper part of the lens is used for distance vision, while the lower segment is used for near vision. The area of the lens that caters to near vision is called the add segment.
The most common type of corrective lens is "single vision", which has a uniform refractive index. For people with presbyopia and hyperopia, bifocal and trifocal glasses provide two or three different refractive indices, respectively, and progressive lenses have a continuous gradient. [1]
Bifocals are eyeglasses with two distinct optical powers correcting vision at both long and short distances. Bifocals are commonly prescribed to people with presbyopia who also require a correction for myopia , hyperopia , and/or astigmatism .
A lenticular lens is an array of lenses, designed so that when viewed from slightly different angles, different parts of the image underneath are shown. [ 1 ] [ 2 ] [ failed verification – see discussion ] The most common example is the lenses used in lenticular printing , where the technology is used to give an illusion of depth, or to make ...
Modern stereo TV camera. Stereo photography techniques are methods to produce stereoscopic images, videos and films. This is done with a variety of equipment including special built stereo cameras, single cameras with or without special attachments, and paired cameras. This involves traditional film cameras as well as, tape and modern digital ...
Some people find them more cosmetically attractive. Because bifocals and related designs are associated with old age, proponents have suggested the lack of visible lines makes a progressive lens appear similar to the single vision lenses worn before the onset of presbyopia.
The four-tube television camera, intended for color television studio use, was first developed by RCA in the early 1960s. [1] [2]: 96 In this camera, in addition to the usual complement of three tubes for the red, green and blue images, a fourth tube was included to provide luminance (black and white) detail of a scene. With such a camera, a ...