NIR Neutral Density Glass References

Purpose

These references can be used to qualify the absorbance accuracy and linearity of near-infrared spectrophotometers with a spectral bandwidth of 6.5 nm or less, over the wavelength range 800 nm - 3200 nm.

 

Description and Discussion

Glass filters mounted ‘stress free’ in an anodised aluminiumholder. The use of Schott NG-type glasses is well established for the validation of the absorbance scale and linearity of spectrophotometers in the near-infrared region.

The spectrum of these filters is relatively flat over most of the range of calibration, but with significant deviation above 2700 n

Calibration values (in % Transmission and Absorbance) are certified at 1100, 1700, 2210, 2500 and 2850 nm. Three filters are available, designated, R1 R3 and I1. Approximate values are:

 

Wavelength  1100 nm 1700 nm 2210 nm 2500 nm 2850 nm
Scale %T A %T A %T A %T A %T A
R1 20 0.70 40 0.40 47 0.32 49 0.31 2 1.83
R3 25 0.59 46 0.34 53 0.28 55 0.26 3 1.54
I1 33 0.48 53 0.28 59 0.23 60 0.22 6 1.25

 

Typical spectra

NG-glass-NIR

Catalogue Number

 

1100 nm 1700 nm 2210 nm 2500 nm 2850 nm Catalogue Number
%T A %T A %T A %T A %T A  
20 0.70 40 0.40 47 0.32 49 0.31 2 1.83 RM-R1
25 0.59 46 0.34 53 0.28 55 0.26 3 1.54 RM-R3
33 0.48 53 0.28 59 0.23 60 0.22 6 1.25 RM-I1

Set of all 3 filters as above

 RM-R1R3I1