Pulsed dye laser densitometry using an optical delay

The light transmission of absorbing filters with optical densities (ODs) greater than 5 is extremely difficult to measure using conventional spectrophotometers due to low SNRs. The paper outlines a simple laser densitometer system using an optical delay to improve the detection scheme, significantly increasing the sensitivity and precision. Optical density measurements of opaque samples as high as 7.5 and a resolution of 0.2% at 4 OD are demonstrated. Through appropriate calibration, signal averaging, and photon counting, the range and the accuracy can be extended to values approaching 12 densities.