Absorptive Neutral Density Filters

• Good general purpose attenuators
• Optical density values to 4
• Stackable without concern for multiple reflections

 

Neutral density filters are used to control the intensity level without affecting the spectral response of the system. They are normally specified in terms of their optical density which is defined as the logarithm of the ratio of intensities in the incident and transmitted beams as follows:

D = log₁₀(I_o/I_t)

This series of absorbing glass neutral density filters is offered in small increments from D=0.1 up to D=4. The thickness of the filters is controlled to produce a calibrated optical density at 546 nm. The response is approximately neutral so they can be used as broad band devices. However, if used at other wavelengths the optical densities will not be exactly as stated for 546 nm. Since these filters rely on absorption as the attenuation mechanism they may be combined in stacks without concern for multiple reflection effects. Optical densities may be combined additively when stacking these filters.