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  2. Optical path length - Wikipedia

    en.wikipedia.org/wiki/Optical_path_length

    In optics, optical path length (OPL, denoted Λ in equations), also known as optical length or optical distance, is the length that light needs to travel through a vacuum to create the same phase difference as it would have when traveling through a given medium.

  3. 1951 USAF resolution test chart - Wikipedia

    en.wikipedia.org/wiki/1951_USAF_resolution_test...

    Glass chart. A 1951 USAF resolution test chart is a microscopic optical resolution test device originally defined by the U.S. Air Force MIL-STD-150A standard of 1951. The design provides numerous small target shapes exhibiting a stepped assortment of precise spatial frequency specimens.

  4. Optical resolution - Wikipedia

    en.wikipedia.org/wiki/Optical_resolution

    Real optical systems are complex, and practical difficulties often increase the distance between distinguishable point sources. The resolution of a system is based on the minimum distance at which the points can be distinguished as individuals. Several standards are used to determine, quantitatively, whether or not the points can be distinguished.

  5. List of optometric abbreviations - Wikipedia

    en.wikipedia.org/wiki/List_of_optometric...

    Back vertex distance BVP: Back vertex power CD: Centration distance C/D: Cup–disc ratio CF: Count fingers vision – state distance c/o or c.o. Complains of CT: Cover test c/u: Check up CW: Close work Δ: Prism dioptre D: Dioptres DC: Dioptres cylinder DNA: Did not attend DOB: Date of birth DS: Dioptres sphere DV: Distance vision DVD ...

  6. Focal length - Wikipedia

    en.wikipedia.org/wiki/Focal_length

    The rear focal length f ′ is the distance from the rear principal plane H ′ to the rear focal point F ′. Front focal distance (FFD) The front focal distance (FFD) (s F) is the distance from the front focal point of the system (F) to the vertex of the first optical surface (S 1). [1] [3] Some authors refer to this as "front focal length".

  7. Optical time-domain reflectometer - Wikipedia

    en.wikipedia.org/wiki/Optical_time-domain...

    It is the optical equivalent of an electronic time domain reflectometer which measures the impedance of the cable or transmission line under test. An OTDR injects a series of optical pulses into the fiber under test and extracts, from the same end of the fiber, light that is scattered (Rayleigh backscatter) or reflected back from points along ...

  8. Foucault knife-edge test - Wikipedia

    en.wikipedia.org/wiki/Foucault_knife-edge_test

    Foucault test setup to measure a mirror. The Foucault knife-edge test is an optical test to accurately measure the shape of concave curved mirrors. It is commonly used by amateur telescope makers for figuring primary mirrors in reflecting telescopes. It uses a relatively simple, inexpensive apparatus compared to other testing techniques.

  9. Optical path - Wikipedia

    en.wikipedia.org/wiki/Optical_path

    The geometrical optical-path length or simply geometrical path length (GPD) is the length of a segment in a given OP, i.e., the Euclidean distance integrated along a ray between any two points. [1] The mechanical length of an optical device can be reduced to less than the GPD by using folded optics .

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