Query	Result	Comments
N-BAF*	N-BAF10 N-BAF3 N-BAF4 N-BAF51 N-BAF52	The result contains all media which names start with N-BAF and finish with any symbols.
N-BAF+	N-BAF3 N-BAF4	Symbol * was substituted with +, thus the result contains the media which names start with N-BAF followed with exactly one symbol. In case of existance of the medium named N-BAF, it is not listed in the result.
N-BF+*	N-BAF3 N-BAF4 N-BALF4 N-BALF5 N-BASF2	This example query matches all names that start with N-BAF, followed by a sequence of symbols ending with F. After F there must be a single symbol.

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Cyrillic names

In catalog GOST Rus all media names are in russian. In english version of the site these names are automatically converted with translit encoding (russian letters are substituted with appropriate english letters) accoding to russian standart GOST 16876-71 (presently GOST 7.79-2000).

Thus, it is possible to use both russian and translit names in search queries, for example:

СТК10 = STK10
ИКС30 = IKS30

Russian/Translit mode switches automatically with the language of viewed version of the site.

The convertion of russian names to translit is implemented according to the table:

а - a	к - k	х - kh
б - b	л - l	ц - c
в - v	м - m	ч - ch
г - g	н - n	ш - sh
д - d	о - o	щ - shh
е - e	п - p	ъ - "
ё - jo	р - r	ы - y
ж - zh	с - s	ь - '
з - z	т - t	э - eh
и - i	у - u	ю - ju
й - jj	ф - f	я - ja

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What is the bin and how to use it

The bin is designed with the aim to make it possible to analyze a separate group of media. You can specify desired group just by adding selected media to the bin. It is very easy to use the bin:

add media to the bin;
analyze them.

Adding is available anywhere at the site where you meet media names:

medium properties page;
page with results of search by name, by parameters or analog search;
page with catalog listing.

Use the icon left to the medium name to add a medium to the bin.

You can gather a set of media just while surfing on the catalogs or making different types of searches. To view the bin contents just click on the "open the bin" link in the main menu.

To delete a medium from bin click on the icon left the the medium name. To clear the bin click "delete all".

After adding you can proceed to analysis. The following functions are presently available:

diagram refraction index / wavelength;
media map refraction index / Abbe value;
media map refraction index / inverse Abbe value;

Media maps display all media in the bin. Only when more than one medium are in the bin media maps are available.

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How to find the most similar media

Analog search gives you the possibility to find media which are the most close by their parameters to the selected medium (etalon).

First specify the etalon. For this purpose use link in the medium properties page or click "analog search" in the main menu.

After you have selected the medium name please specify search parameters:

Limit for the quantity of media found.
This limit sets maximum of media quantity listed in the result.
Dispersion formula.
When a medium has several approxiamations of refraction index you are required to select the one that would be used for calculations of optical parameters.Working spectral range (spectral range on which approximation of refraction index was realized) is specified in brackets just after dispertion formula name.
Search source.
Select the set of catalogs searched for analogs. The default value is "all catalogs".
Search criterium.
The criterium which is used for analog search must be selected. Search by refraction index, partial dispertion or Abbe value are available.

It is possible to indicate several characteristics at different wavelengthes. Choose standart wavelength from listbox or an arbitrary wavelength in mkm. Please be attentive, the wavelength value must be in working spectral range.

The result list is sorted in order of increasing of mean square deviation of media parameters from etalon (first in the list).

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Dispersion formulas

Dispersion formula is the approximation that allows to descript refraction index as a function of wavelength .

A set of coefficients are defined for each medium (depend on formula type). The coefficients are used for calculations of refration index at any point of spectrum, where approximation was made. Border wavelengthes of this part of spectrum should be defined for each separate approximation to avoid data extrapolation.
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Description of dispersion formulas

The Herzberger formula
, where

The Sellmeier formula

The Conrady formula

The Schott formula

The Reznik formula
, where
, , , , , ,
, ,
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Optical properties

Refraction index

Refraction index is the ratio of speed light in vacuum to that in medium: . glassbank uses dispertion formulas for calculation of refraction indexes.
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Dispersion

The dependence of refraction index from wavelength is called the dispertion of refraction index . Numerically dispertion is described by a number of characteristics.

Principal dispertion coefficient (Abbe value) – , where and – are refraction indices, that bound some spectral range, and – is the refraction index for a wavelegth in the spectral range.

Partial dispersion is defined as , where and are refraction indices for two wavelengthes that bound some specral range.

Relative partial dispersion is the ratio of partial dispertions calculated for two spectral ranges. It characterizes the degree of change of dispertional properties of a medium along the spectrum:
, where and are relative partion dispertions for spectral ranges, corrispondingly bounded with wavelengthes x, y and z, k.

All dispertion parameters are calculated with dispertion formulas.
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transmittance

Spectral internal transmittance (transmission factor or transmittance) is the ratio of luminous flux transmitted through a medium to the incident luminous flux:

The incident flux should be monochromatic, parallel, directed normally to plainparallel plate made of isotropic, homogeneous, non luminescent, non photocromic material.
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Coloring (Color code)

The position of the transmission cut off in the UV range is described by the color code. The coloring specifies wavelengthes and , where transmittance is equal to 0.8 and 0.05 correspondingly.
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Weakening

Weakening – is the value inversed to the thickness of a sample, which weakens incident flux in 10 (or e) times (light absorbtion and scattering are taken into consideration).

, where – weakening, – transmittance, – sample thickness.
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mechanical properties

Density

Density is the mass of a unit of volume.

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Poisson's ratio

Poisson's ration (lateral deformation coefficient) – is the ratio of ralative lateral expansion (narrowing) to relative longitudinal lengthening :

The poisson's ration is the same for all directions for the amorphous media, and depends on direction of applied force for crystals.
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Young's modulus

Young's modulus is defined as the ratio of the tension to the internal deformation:

, where – is the force perpendicularly applied to an unit of area.

The young's modulus is the same for all directions for the amorphous media, and depends on direction of applied force for crystals.

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Modulus of rigidity

Modulus of rigidity connects young's modulus and poisson's ratio:

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Abrasion

Abrasion is the realtive grind hardness, which defines the ratio of volume of etalon medium grinded with loose abrasive to the volume of test medium grinded in the same conditions.

Abrasion serves as technological criterion of deterioration speed of a medium during grinding.

Each catalog defines abrasion in it's own way.

Russian GOST Etalon medium is glass 'K8'.

Schott 2000 The meaning of the characteristic is defined according to
ISO 12844 (1999)

O'Hara Techical information is available at
http://www.ohara-gmbh.com/e/katalog/tinfo_5_3.html

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Optical stress coefficient

Optical stress coefficient defines the difference of optical pathes of polarized rays in medium and characterises birefringence caused by tensions in the material.

When elastic deformations appear the medium obtains photoelastic properties. The medium becomes an anisotropic material, that causes birefringence to appear: the passing through the medium ray polarizes and devides into two rays - ordinary and extraordinary, which polarization planes are perpendicular. This effect is called photoelastisity.

Refraction indices for polarized ray differ from refraction indeces of not stressed medium. Photoelasity of a medium is characterized by photoelastic constants and , that show change of refraction index values for rays which are polarized parallel and perpendicular to the tension line; another characteristic is optical stress coefficient:

After force is removed glass becomes an isotropic material again.

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Hardness

Hardness is the measure of resistance to permanent set or destruction.

There are several method of hardness determinaton. The most common method is the measuring of resistance of tested material to chisel (indentor or ball) penetration. The hardness value is determined by force applied to the unit area at place of contace of indentor with tested medium and has dimention (Knoop hardness, Brinell hardness, Vickers hardness).

Determination of Knoop hardness is standartized by ISO 9385.

Another method of hardness determination exposes material to scratching. Classification uses scale from 1 to 10. The lower number corresponds to hardness of talk, 10 - hardness of diamond. Theese numbers define Mohs hardness.

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Chemical properties

Chemical properties of russian GOST

Russian GOST uses two types of chemical resistance: the resistance of polished glass surface to damp atmosphere influence (climatic resistance) without vapour condensation (relative humidity 75 %) and resistance to staining reagents (staining): neutral water, acid and alkaline water solutions.

Silicate optical glasses are grouped into 3 groups by climatic resistance:
А – stable,
Б – middle,
В – nonstable.

Most of the glass are in A group. Optical details made of nonstable glasses are covered with protective films.

Optical glasses are grouped by resistance to staining reagents::
I – stable,
II – half stable,
III – nonstable,
IV – nonstable glasses which require covering with protective films.

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Climatic resistance

Climatic resistance characterizes the degree of influence of water vapours of atmosphere at the glass. This influence, at high temperatures espesially, causes muddy film to appear at the glass surface. Chemical reaction is the result of reaction neutral water from atmosphere with glass.

Technical information about ways of definition of climatic resistance for O'Hara catalog is available at http://www.ohara-gmbh.com/e/katalog/tinfo_4_2.html.

In Schott 2000 catalog climatic resistance is defined as result of transmittance change after glass plates exposing in water-vapour-saturated atmosphere during 30 hours at temperatures from 40 to 50 С.

Class	1	2	3	4
transmittance change	< 0,3%	>= 0,3% < 1%	>= 1% < 2%	>= 2%

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Resistance to acids

Reaction of acid medium with glass surface leads to staining and destruction of glass surface. Resistance to acids determines the degree of influence of acid medium onto glass.

Acid resistance classes are defined accoding to ISO 8424 (O'Hara, Schott 2000).

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Resistance to alkalis

Resistance to alkalis determines the degree of influence of alkalis medium onto glass.

Standart method of alkalis resistence definition is described in ISO 10629.

In Schott 2000 catalog alkalis resistance classes are determined by time required for 0.1 mm layer dissolving by alkalis medium at the temperature of 50 C.
Schott 2000 alkalis resistance classes are listed in the following table:

Class	1	2	3	4
Time, hour	> 4	1 - 4	0.25 - 1	< 0.25

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Phosphate resistance

The water solutions used to clean optical glassesusually are not pure hydroxide solutions, rather they contain polyphosphates among other things. The phosphte resistance classes allow statements to be made regarding the resistance of optical glasses to such detergents.

In O'Hara and Scoott 2000 catalogs phosphate resistance classes are defined according to ISO 9689.

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Staining

The influence of light acid solutions (breath, perspiration) results in the wash out of some substances from glass, that leads to appearing of interference color stains on the glass surface. Еру resistance of glass to such influences is discribed by staining.

The class of stain resistance in Schott 2000 catalog is determined according to the following procedure: the plain polisged glass sample to be tested is pressed onto a test cuvette which has a spherical depression of max 0.25 mm depth containing a few drops of a test solution (standart acetate, pH=4.6 (I) or sodium acetate buffer, pH=5.6 (II) ).

Interference color stains develop as a result of decomposition of the surface of the glass by the test solution. The measure for classifying the glasses in the time which elapses beforethe first brown-blue stain occurs at a temperature of 25 С.

Class	0	1	2	3	4	5
Test solution	I	I	I	I	II	II
Time, hour	100	100	6	1	1	0.2
Color change	no	yes	yes	yes	yes	yes

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Termal properties

Temperature coefficient of refraction index

The refraction index depends on not only the wavelength, but also from temperature.

The ratio of temperature change to refraction index change is called temperature coefficient of refraction index. The value of the coefficient can be positive or negative.

Relative temperature coefficient of refration index is measured in air at certain air pressure, absolute coefficient - in vacuum.
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Temperature coefficient of linear expansion

Internatinal standart: ISO 7991.

Temperature coefficient of linear expansion (TCLE) characterizes relative lengthening of glass sample after it's heating on 1 C:

The TCLE is usually measured in wide temperature range, so it's value depends not only on the mediam itself, but also on temperature range.

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