ND13B Dia. 25 mm Unmounted Reflective ND Filter; Optical Density 1.3

The ND13B is a circular Neutral Density Filter, unmounted and with a diameter of 25 mm, sourced from the renowned optical component manufacturer, Thorlabs. This filter is designed to reduce the intensity of incident light without altering its color composition, making it an essential tool for various optical applications.

The filter's primary coating, denoted as 'tho nd13' on both the front and back surfaces, contributes to its neutral density properties. This coating is uniformly applied to ensure consistent light reduction across the entire spectral range. The ND13B boasts an optical density of 1.3, which translates to a reduction of approximately 40% of the incident light's intensity.

The filter is made from N-BK7 Schott glass, a material known for its excellent optical properties, including high homogeneity, low auto-fluorescence, and superior transmittance across a wide spectrum. The geometry of the filter includes a thickness of 1 mm, which contributes to its durability and overall structural integrity.

The ND13B's shape is classified as a 'Thin Lens', indicating that it has been designed to minimize optical aberrations and distortions. This feature is particularly beneficial in applications that require high precision and accuracy, such as imaging and metrology.