A magnifying glass is optical a subjective instrument made up of a convex lens making it possible to obtain from an object an increased image. The magnifying glass is the simplest form of the optical Microscope, which, it, consists of several lenses: the objective and the Ocular and of a supplemented elaborate lighting system of a condenser of light returning the bottom linked without parasitic image, and which answers the dioptric definition of system centered .
A magnifying glass functions on the principle of the convex lens (a system converge simple): an increased virtual image of an object is created in front of the lens. For that, the distance between the lens and the object must be shorter than the focal distance from the lens. Characterized by its enlargement, its commercial enlargement (for an observer to 0,25 m), its lens by its power.
The invention of the magnifying glass is lost in the mists of time: for example the archaeological museum of Iraklion, in Greece, presents in a window of objects of. some " cailloux" round-offs and carefully polished glass, well transparencies, and through which one sees perfectly the very enlarged screen of the fabric on which these " cailloux" are posed.
There exist several kinds of magnifying glasses differentiated by their mountings:
- the magnifying glasses with handle, most current, which are held with the hand, and make it possible to enlarge a detail difficult to distinguish with the naked eye, or with reading a text writes too small,
- the magnifying glasses thread-counter, which can be posed, and eliminate the tremors thus. At the origin, these magnifying glasses were intended to count wire of a fabric and for this reason comprise a Réticule graduated. The photographers use them to control the detail of negative or the diapositifs of small sizes, in silver technique.
- the ocular magnifying glasses plating itself on the arcade even eye by an of the same mounting forms, releasing the hand of its maintenance.
- magnifying glasses of large diameter associated with a circular lighting, coupled on a socketed stanchion often type pantograph, allowing to work with the two hands on the part observed and without shade.
There exist collapsible magnifying glasses, lighting magnifying glasses, magnifying glasses with frontal support, magnifying glasses with flexible support, grip, etc Et a derived name (which could appear unsuitable): the binocular magnifying glass which comprise, it, two tubes having each one an objective and an eyepiece, allowing the stereoscopic vision of small elements, returning the observation less tiring that with an eye alone, as requires it the elementary magnifying glass. It should not be confused with the optical, more demanding microscope and of another technical development.
Numerical magnifying glass
By extension, one calls numerical magnifying glass, of the systems of industrial vision used to replace the traditional magnifying glass. For operators continuously using magnifying glasses with their work, like the clock and watch makers, precision mechanics, quality control, visual comfort is incomparable.The numerical magnifying glasses are made up of a system of vision and elements following:
- digital camera of variable resolution (but to the maximum equalizes with the resolution of the screen of posting), black and white or color;
- objective, with fixed or variable enlargement;
- software of acquisition and posting;
- screen LCD for posting;
- rigid or adjustable, magnetized or fixed support.
See too
- optical System
- Ocular Lens
- virtual Image
Simple: Magnifying knell Zh-min-nan: Hàm-kiàⁿ
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