Optical Technology
SMC's Optical Flow Sensor technology is based on two concepts:
- Optical Scintillation (Light Fluctuation)
- Temporal Cross-Correlation (i.e. Time of Flight)
ALOFS technology is independent of the media, temperature, pressure, humidity & opacity!
Optical Scintillation
Scintillation: the refraction of light through air pockets with different temperatures & densities (i.e. atmospheric turbulence).
Optical Scintillation induces light fluctuations. This phenomenon is a measureable atmospheric condition. The method employed to measure scintillation has been in use fro over 30 years in atmospheric remote sensing.
Examples of Scintillation: the light shimmering off a blacktop road on a hot day or the twinkling of a star at night.
The left-hand picture shows how light behaves without atmospheric turbulence (as in the vacuum of space). The right-hand picture demonstrates the diffusion of light (a.k.a. optical scintillation) caused by atmospheric turbulence, which exists in the air everywhere.
Temporal Cross-Correlation
A Statistical Method to Measure Time of Flight: ALOFS measures the movement of scintillation "cells." Detector A senses the scintillation pattern first and then detector B senses the same pattern as it moves through the beam and past both detectors. OFS measures the time at which this pattern is detected at each point and knows the distance between the two detectors. Using advanced digital signal processing and temporal cross-correlation, OFS can calculate the velocity of the flow: Velocity = distance / time