Optical density
2023-11-23
Definition:
Abbreviation: OD Logarithmic value of power attenuation.
Optical density is generally considered to refer to the absolute value of the base 10 logarithm of the optical attenuator power transmission factor. For example, an optical density of 3 represents a power attenuation factor of 103 = 1000. The corresponding attenuation coefficient is 30 dB.
If several attenuators form a chain, their optical densities are simply added.
Optical density is considered the same as absorbance. However, the optical attenuation of neutral density filters, for example, does not come entirely from absorption but is at least partly from reflection. Optical density therefore characterizes the overall power transmission, regardless of the extent to which it is due to absorption.
Optical density and refractive index
A transparent medium usually has a high optical density if it has a high refractive index. For example, one can say that total internal reflection occurs only when a beam of light travels from an optically denser medium to an optically rarer medium. The optical density at this time is completely unrelated to the attenuation.
Abbreviation: OD Logarithmic value of power attenuation.
Optical density is generally considered to refer to the absolute value of the base 10 logarithm of the optical attenuator power transmission factor. For example, an optical density of 3 represents a power attenuation factor of 103 = 1000. The corresponding attenuation coefficient is 30 dB.
If several attenuators form a chain, their optical densities are simply added.
Optical density is considered the same as absorbance. However, the optical attenuation of neutral density filters, for example, does not come entirely from absorption but is at least partly from reflection. Optical density therefore characterizes the overall power transmission, regardless of the extent to which it is due to absorption.
Optical density and refractive index
A transparent medium usually has a high optical density if it has a high refractive index. For example, one can say that total internal reflection occurs only when a beam of light travels from an optically denser medium to an optically rarer medium. The optical density at this time is completely unrelated to the attenuation.
