The AGF & BGF File Formats

OpticStudio stores glass catalog data in two file formats, called the ANSI Glass Format (AGF) and the Binary Glass Format (BGF). The glass catalog data supplied with OpticStudio is in the AGF format, and AGF files may be used when glass catalog data needs to be modified or created by the glass manufacturer. When OpticStudio runs, AGF files are automatically converted, if required, to BGF files. The BGF files are only used by OpticStudio to speed up the loading of the glass catalogs, and should never be created, edited, or distributed. OpticStudio will create or update a BGF whenever required. The AGF file is the "master" file used to define glass catalog data

The AGF file consists of a header line followed by a series of records, one for each glass. The header line format is:

CC <Catalog Comment>
!Standard glass: write your definition of standard status
!Special glass: write your definition of special status
!Obsolete glass: write your definition of obsolete status

The mnemonic CC stands for Catalog Comment, and any comment string up to 140 characters may be placed here to define a comment for the catalog as a whole. The lines starting with ! are optional and will not appear in the material catalog. These lines can be used to explain the classification between the different status of materials. Each subsequent record consists of a two letter mnemonic followed by one or more data items separated by spaces. For a description of these data see "Description of catalog data". The format of a single record is:

NM <glass name> <dispersion formula #> <MIL#> <N(d)> <V(d)> <Exclude Sub> <status>
<melt freq>
GC <Individual Glass Comment>
ED <TCE (-30 to 70)> <TCE (100 to 300)> <density> <dPgF> <Ignore Thermal Exp>
CD <dispersion coefficients 1 - 10>
TD <D0> <D1> <D2> <E0> <E1> <Ltk> <Temp>
MD <E> <nu> <HK> <cp> <k>
OD <rel cost> <CR> <FR> <SR> <AR> <PR>
LD <min lambda> <max lambda>
IT <lambda> <transmission> <thickness>
IT <lambda> <transmission> <thickness>
... multiple IT lines may follow
BD <lambda> <K> <-K11> <-K12>

Comments on the individual fields follow.

NM: Glass name and other data.

The syntax is:

NM <glass name> <dispersion formula #> <MIL#> <N(d)> <V(d)> <Exclude Sub> <status> <melt freq>

  • <glass name> is the name of the material.

  • The dispersion formula number is 1 for Schott, 2 for Sellmeier 1, 3 for Herzberger, 4 for Sellmeier 2, 5 for Conrady, 6 for Sellmeier 3, 7 for Handbook of Optics 1, 8 for Handbook of Optics 2, 9 for Sellmeier 4, 10 for Extended, 11 for Sellmeier 5, 12 for Extended 2 and 13 for Extended 3.

  • The MIL# is provided for back compatibility and is not used, but a placeholder value must be provided.

  • The nd and vd values are also provided for reference but are not used.

  • The "exclude sub" flag is 0 for no and 1 for yes.

  • Status is 0 for Standard, 1 for Preferred, 2 for Obsolete, 3 for Special, and 4 for Melt.

  • Melt Freq is an integer between 1 and 5 to indicate the relative frequency of melting by the manufacturer.

GC: Glass comment. Any text string up to 140 characters long may be placed here.

ED: Extra Data. The values are the TCE in the -30 to 70 degree Celsius range, the TCE in the 100 to 300 degree Celsius range (this value is currently not used), the density, dPgF, and the Ignore Thermal Expansion flag, which is 0 for no and 1 for yes.

CD: Coefficient Data. Up to 10 coefficients may be provided. The meaning of these coefficients depends upon the dispersion formula used.

OD: Other Data. The relative cost, CR, FR, SR, AR, and PR values. For these values, -1 should be specified if the data is not available.

LD: Lambda Data. The minimum and maximum wavelength in micrometers over which the dispersion formula is valid.

MD: Mechanical Data. Young's Modulus E in GPa (10³ N/mm²), Poisson's Ratio ν(nu), Knoop Hardness HK in kgf·mm−2, Specific Heat Capacity cp in J/kgK, Heat Conductivity in W/mK

TD: Thermal Data. These are the D0, D1, D2, E0, E1, Ltk, and reference temperature values.

IT: Internal Transmittance. These lines are the internal transmittance. Each line defines a wavelength, transmission, and thickness in millimeters. The wavelengths must be in ascending order. Up to 100 points may be defined for each glass record.

BD: Stress Birefringence Data. These lines hold the Stress Optical Coefficients. Each line defines the wavelength lambda in µm, Stress Optical Coefficient K = K11-K12 (unit 10^-6 mm²/N), photoelastic coefficient for light oscillating parallel to the direction of stress -K11, photoelastic coefficient for light oscillating perpendicular to the direction of stress -K12 (unit 10^-6 mm²/N).

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