Learn about the function and importance of UV-A pass filters, and why ASTM E3022 requires all LED UV lamps to have them
The quick answer to, “Why should a LED UV black light have a UV-A pass filter?” is because UV-A pass filters reduce glare and increase contrast of fluorescent indications. Which makes fluorescent inspection easier, faster and more reliable.
In this article, we will explain why a UV-A pass filter is needed, and how the pass filter works to create better UV irradiation for nondestructive testing inspection.
Why do LED UV lamps need a filter?
From a technical point of view, ASTM defines UV-A as 320-400 nm, and visible light as 400-760 nm. The emission spectrum of an UV-A LED is a single peak in the 360-370 nm range. But this is not a tight, sharp peak, and at the tail end of the emission spectrum you get measurable emission above 400 nm.