FND-20C02-30 20 mm Dia. Unmounted N-BK7 Visible Reflective Neutral Density Filter; t=2mm 400-700nm

The FND-20C02-30 is a high-quality Neutral Density Filter, unmounted and with a 20 mm diameter, sourced from the reputable vendor OptoSigma. This particular model is designed for use within the visible light spectrum, specifically catering to wavelengths between 400 and 700 nanometers.

The filter boasts a thickness of 2mm, providing a robust and durable platform for various optical applications. Its base shape is circular, allowing for easy integration into a wide range of optical systems. The material used for this filter is N-BK7, a type of borosilicate glass manufactured by Schott AG, renowned for its excellent optical properties and versatility.

The FND-20C02-30 is coated with OptoSigma's proprietary FND-30 coating on both the front and back surfaces. This coating enhances the filter's performance, providing a reflective neutral density effect that is crucial in many optical setups. The coating also ensures the filter maintains a thin lens shape, minimizing any potential distortions and maintaining the integrity of the optical path.