Optical Density

$OD\_\backslash lambda\; =\; \{A\_\backslash lambda\; \backslash over\; l\}\; =\; -\{1\; \backslash over\; l\}\; \backslash log\_\{10\}\; T\; =\; \{1\; \backslash over\; l\}\backslash log\_\{10\}\; \backslash left\; (\{I\_0\; \backslash over\; I\}\; \backslash right\; )$

l is the distance that light travels through the sample (i.e., the sample thickness), measured in cm;

$A\_\backslash lambda$ is the absorbance at wavelength λ;

T is the per-unit transmittance;

$I\_0$ is the intensity of the incident light beam;

I is the intensity of the transmited light beam.

−1. The higher the optical density, the lower the transmittance. Optical density times 10 is equals to a transmission loss rate expressed in decibels per cm, e.g., an optical density of 0.3 corresponds to a transmission loss of 3 dB per cm.

References

• Federal Standard 1037C

* MIL-STD-188

 

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