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The 4-element orthoscopic eyepiece consists of a plano-convex singlet eye lens and a cemented convex-convex triplet field lens achromatic field lens. This gives the eyepiece a nearly perfect image quality and good eye relief, but a narrow apparent field of view — about 40°–45°. It was invented by Ernst Abbe in 1880. [3]
It was developed in 1898 by Emil von Hoegh, as a development of his earlier Dagor lens (1892) designed for the German company Goerz. [1] [2] It was originally named the Double Anastigmat Goerz [Dagor] Type B, sold in both f /4.5 and f /6.3 versions; in 1904, the faster f /4.5 version was renamed to the Celor and the f /6.3 version was renamed to the Syntor.
The largest element observed without distinct image contrast indicates the approximate resolution limit. [citation needed] This element's label is noted by the observer (each group, and each element within a group, is labeled with a single digit). This pair of digits indicates a given element's row and column location in the series table, which ...
Field lens: A correcting lens placed just before the image plane of a telescope. [citation needed] Telecompressor or focal reducer: Optical element to decrease the telescope's focal length and magnification (usually by a fixed percentage) and widen the field of view, providing opposite effects of a Barlow lens.
Orthoscopy used in optics and vision for the condition of normal, distortion-free view, from "ortho", straight, right, correct, and "scope", seeing.. Abbe in 1880 [1] designed an orthoscopic eyepiece for stereoscopic microscopes which minimized distortion.
Zeiss Protar (Rudolph, 1890). The first Anastigmat was designed by Paul Rudolph for the German firm Carl Zeiss AG in 1890 and marketed as the Protar; [1]: 65–66(§103) it consisted of four elements in two groups, as an asymmetric arrangement of two cemented achromatic lens doublets and was improved to a five-element, two-group design in 1891, substituting a cemented triplet for the rear group.
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 ...
Cooke triplet. According to Taylor, the lens design was derived by considering a cemented achromatic doublet consisting of one thin negative element and one thin positive element, both of equal power; such a doublet would result in a compound lens with zero net power but also a flat field of focus.