Case Study: 450 nm Long Pass Filter

Case Study: Long Wave pass filter to ensure visibility of Fluorescence wavelengths

Customer Challenge: Fluorescence is quite a well know effect for detecting certain chemicals. A substance in this case was illuminated by a UV LED which excites a higher wavelength to be emitted from the substance under microscopic observation due to fluorescence. These emitted wavelengths are of a much lower intensity than the exciting photons and thus there is a danger they will not be observed. A suitable long wave pass filter in the path of the emitted light is required.

Vortex’s Solution: The long wave pass filter should be designed to act as per figure 1 and 2 above. It needs to be quite steep in this case since the excitation and emitted wavelengths are relatively close. The long wave pass filter also needs to be dense (> than OD 5) to block out the overlap of the LED and emitted wavelengths, failure to do this would result in a ‘false positive’ result. The LED light source was also slightly divergent meaning this had to be taken into account in the filter design.

The Outcome: The steep filter supplied proved very effective in eliminating the LED wavelengths that could cause a false result.