In optics, an index-matching material is a substance, usually a liquid, a cement (adhesive), or gel, having a refractive index approaching other objects (such as lenses, materials, optical fibers, etc.).
When two substances with the same index come into contact, the light moves from one to the other without reflection or refraction. As such, they are used for a variety of purposes in science, engineering, and art.
For example, in popular home experiments, glass rods are made almost invisible by soaking them in transparent liquids that are index-matched like mineral spirits.
Video Index-matching material
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In light microscopy, oil dyeing is a technique used to improve the resolution of a microscope. This is achieved by immersing objective lenses and specimens in transparent oils with a high refractive index, thus increasing the objective lens's numerical openings.
Oil immersion is a transparent oil having special optical and viscosity characteristics required for use in microscopy. The special oil used has a refractive index of about 1,515. The purpose of oil immersion is an objective lens specially designed to be used in this way. The oil index is usually selected to match the microscope lens glass index, and the cover slip.
For more details, see the main article, oil immersion. Some microscopes also use other index-matching materials other than oil; see immersion of objective lens and solid immersion.
Maps Index-matching material
In optical fiber
In optical fibers and telecommunications, suitable index materials may be used in conjunction with pairs of mated connectors or with mechanical connections to reduce the reflected signal in guide mode (known as return loss) (see: fiber optic connector). Without the use of suitable index materials, Fresnel reflections will occur on the smooth finish surface of the fibers unless there is no air-fiber interface or significant non-conformity in the refractive index. This reflection may be as high as -14 dB ( i.e., 14 dB below the optical signal signal incident). When the signal is reflected back to the transmitting end, it can be reflected back and back to the receiver end at a level that (28 plus twice the fiber loss) dB below the direct signal. The reflected signal will also be delayed by twice the delay time introduced by the fiber. The re-reflected, twice-delayed signal superimposed on the direct signal can significantly decrease the analog-intensity modulated video signal. In contrast, for digital transmission, the reflected signal often does not have a practical effect on the detected signal seen at the optical optical receiver decision point except in the marginal cases where the bit-error ratio is significant. However, certain digital transmitters such as those using the Distributed Laser Feedback may be affected by rear reflection and then fall outside the specifications such as Side Mode Suppression Ratio, potentially lowering the system bit error ratio, so network standards intended for DFB lasers can specify reflection tolerances such as -10 dB for transmitter so it stays in the specification even without index matching. This rear reflection tolerance can be achieved by using an optical isolator or by reducing coupling efficiency.
For some applications, not polished standard connectors (eg FC/PC), polished corner connectors (eg FC/APC) can be used, where non-perpendicular polish angles greatly reduce the bounce signal ratio launched into guided mode even in cases fiber-air interface.
In experimental fluid dynamics
Index matching is used in liquid-liquid and liquid-solid (multifasa) experimental systems to minimize distortions occurring in this system, which is critical for systems with many optically inaccessible interfaces. Refractive index matching minimizes reflection, refraction, diffraction and rotation that occur on the interface allowing access to areas that should not be accessible by optical measurements. This is especially important for advanced optical measurements such as Laser-induced fluorescence, velocimetry particle tracking and velocimetry particle tracking to name a few.
In art conservation
If the statue is broken down into sections, the art conservator can reassemble pieces using adhesives such as Paraloid B-72 or epoxy. If the sculpture is made of transparent or semi-transparent material (such as glass), the stitches in which the pieces are installed will usually be much less noticeable if the refractive index of the adhesive corresponds to the refractive index of the surrounding object. Therefore, the art conservator can measure the index of objects and then use index-matched adhesives. Similarly, losses (missing parts) in a transparent or semi-transparent object are often filled using index-matched materials.
In the optical component adhesive
Certain optical components, such as the prism of Wollaston or the prism of Nicol, are made up of several transparent parts attached to each other. The adhesive is usually matched to the index. Historically, Canadian balsam is used in this application, but it is now more common to use epoxy or other synthetic adhesives.
References
- This article incorporates public domain material from the "Federal Standard 1037C" General Administration Service document.
Source of the article : Wikipedia
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