MULTI-REGION OPTICAL FILTERS AND SYSTEMS AND METHODS USING SAME

A liquid measuring system (LMS) comprising: a light source; a multi-region optical filter (MROF); a sample cell configured to contain a liquid sample; an optical detection subsystem (ODS) having an optical detector for measuring optical properties of light emanating from the liquid sample. The MROF may include a spectral filter region such as a bandpass or a long-pass filter type region, and natural density (ND) type filter region, for enabling simultaneous optical measuring at least of turbidity level and algae concentration in a water sample contained by the sample cell, by having light passed through the water sample and the MROF before reaching the optical detector of the ODS. Embodiments of the MROFs may be also used, for example for selective spectral attenuation of light illuminating the liquid sample to achieve reduction in distortions due to stray light.