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13 – Prism scale knob. A lensmeter or lensometer (sometimes even known as focimeter or vertometer), [1] [2] is an optical instrument used in ophthalmology. It is mainly used by optometrists and opticians to measure the back or front vertex power of a spectacle lens and verify the correct prescription in a pair of eyeglasses, to properly ...
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Lens clock. A lens clock is a mechanical dial indicator that is used to measure the dioptric power of a lens.It is a specialized version of a spherometer.A lens clock measures the curvature of a surface, but gives the result as an optical power in diopters, assuming the lens is made of a material with a particular refractive index.
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Multiple prism beam expander using r prisms ( M B 0 1 M ) {\displaystyle {\begin{pmatrix}M&B\\0&{\frac {1}{M}}\end{pmatrix}}} M is the total beam magnification given by M = k 1 k 2 k 3 ··· k r , where k is defined in the previous entry and B is the total optical propagation distance [ clarification needed ] of the multiple prism expander.
The Preview application can display PDF files, as can version 2.0 and later of the Safari web browser. System-level support for PDF allows macOS applications to create PDF documents automatically, provided they support the OS-standard printing architecture. The files are then exported in PDF 1.3 format according to the file header.
Developed by. 3D Systems. Initial release. 1987. Type of format. Stereolithography. STL is a file format native to the stereolithography CAD software created by 3D Systems. [ 3][ 4][ 5] Chuck Hull, the inventor of stereolithography and 3D Systems’ founder, reports that the file extension is an abbreviation for stereolithography. [ 6]
Many mathematical problems have been stated but not yet solved. These problems come from many areas of mathematics, such as theoretical physics, computer science, algebra, analysis, combinatorics, algebraic, differential, discrete and Euclidean geometries, graph theory, group theory, model theory, number theory, set theory, Ramsey theory, dynamical systems, and partial differential equations.