Optical density

Optical density

In optics, density is a unitless measure of the transmittance of an optical element for a given length at a given wavelength "λ": [cite book|title=The Focal Digital Imaging A-Z|first=Adrian|last=Davies|url=http://books.google.com/books?id=j7l0CxBUwGwC&pg=PT44&dq=density+dmax+dmin+logarithm&ei=2j23R7OwKJbWzAT4gpXGBQ&sig=DqqcRgdi1GeJs_J5GnzBIS3ZB44|publisher=Focal Press|isbn=0240519809|year=2005]

:OD_lambda = log_{10} O = - log_{10} T = - log_{10} left ({I over I_0} ight ):

The higher the optical density, the lower the transmittance.

Defined in terms of unit length, and expressed in decibels, the density is termed the transmission loss rate For example, an optical density of 0.3 corresponds to a transmission loss of 3 dB per cm. Defined without regard to the length of the sample, the density is a synonym for absorbance. Neutral density filters are typically quantified this way. Some filters, notably welding glass, are rated by shade number, which is 7/3 times the optical density. A shade number of 14 is regarded as safe for direct observation of the sun.

At least one high-school textbookCitation | author = Zitzewitz, Paul W. | year = 1999 | title = Glencoe physics | isbn = 0028254732 | publisher = Glencoe/McGraw-Hill | location = New York, N.Y. | | page = 395 ] claims that optical density and refractive index are the same property. The accepted definitions of the two properties are, however, incompatible.


ee also

* Densitometry

Wikimedia Foundation. 2010.

Look at other dictionaries:

  • optical density — n ABSORBANCE * * * (OD) absorbance …   Medical dictionary

  • optical density — optinis tankis statusas T sritis Standartizacija ir metrologija apibrėžtis Į sugeriančiąją sistemą kritusios ir per ją perėjusios šviesos intensyvumų dalmens dešimtainis logaritmas, t. y. D(λ) = –lg(τ(λ)); čia τ(λ) – spektrinis praleidimo… …   Penkiakalbis aiškinamasis metrologijos terminų žodynas

  • optical density — optinis tankis statusas T sritis chemija apibrėžtis Į sistemą kritusios ir pro ją praėjusios šviesos intensyvumų santykio dešimtainis logaritmas. atitikmenys: angl. absorbance; absorbency; optical density rus. оптическая плотность …   Chemijos terminų aiškinamasis žodynas

  • optical density — optinis tankis statusas T sritis fizika atitikmenys: angl. optical density vok. optische Dichte, f rus. оптическая плотность, f pranc. densité optique, f …   Fizikos terminų žodynas

  • optical density — noun (physics) a measure of the extent to which a substance transmits light or other electromagnetic radiation • Syn: ↑transmission density, ↑photographic density, ↑absorbance • Topics: ↑physics, ↑natural philosophy …   Useful english dictionary

  • Optical density — Оптическая плотность …   Краткий толковый словарь по полиграфии

  • optical density — Смотри оптическая плотность …   Энциклопедический словарь по металлургии

  • optical density — noun Physics the degree to which a refractive medium retards transmitted rays of light …   English new terms dictionary

  • optical density method — the measuring of growth rates of cells by taking the optical density or turbidity of a dense population and comparing this with optical densities of known dilutions of the sample …   Medical dictionary

  • spectral optical density — spektrinis optinis tankis statusas T sritis Standartizacija ir metrologija apibrėžtis Dydis, lygus atvirkštinio optinio spektrinio praleidimo faktoriaus dešimtainiam logaritmui, t. y. D(λ) = lg (1/τ(λ)); čia – D(λ) – spektrinis optinis tankis,… …   Penkiakalbis aiškinamasis metrologijos terminų žodynas