Case Study: Visible ND Filter 10%

Case Study: Low-Cost Neutral Density Filter to Reduce Excess Signal in the Visible Range

Customer Challenge: The customer required an affordable solution to reduce the solar radiation entering their system in the visible range. ‘Off the shelf’ polarisers had been tried in the past, but they were not suitable for this application because prolonged exposure bleached them, rendering them unsuitable for long term use.

Vortex’s Solution: To meet the budget challenge, we decided to make this filter from borosilicate glass, an inexpensive substrate, when compared to sapphire, quartz and other materials that transmit in the visible range. We also had uncoated 25 mm diameter, 1mm thick substrates in stock, so the lead-time was less than 2 weeks. The coating that we applied was a simple neutral density filter to meet the 10+/-3% transmission requirement (Optical Density 1).

Outcome: We were able to provide the ND filter to cover all the requirements, reducing solar radiation without bleaching and deterioration over time and keeping the cost to a minimum. We have since supplied these filters to the same customer on a call-off contract  for over 10 years!