Compensatory approach to exclude methodological errors in measurements of spectral transparency of seawater

Abstract

A compensatory approach aimed at eliminating methodological errors in the measurements of the beam attenuation coefficient in seawater is proposed and the scheme of the transmissometer in which this approach is implemented is described. The special feature of the proposed optical scheme is that the measuring and reference beams are formed by identical optical elements that make up the reference and measuring channels, while both channels are transmitted to the measured medium. Since the measurement and reference channels are identical and both are transmitted in the measured environment, there is no need to correct changes of reflectance on optical parts when the device is immersed in sea water. There is also no need for complex calibration using pure water. As a result, it is possible to use the instrument calibration in air to determine the beam attenuation coefficient after immersion of the instrument in water. Since the measurements are actually performed on two optical bases, self-calibration of the device can be performed without the usage of pure water with known optical characteristics. A powerful multi-element seven-color LED is used as a light source.