Optical particle sensor
摘要:
The invention describes a laser sensor module. The laser sensor module comprises at least a first laser (111) being adapted to emit a first measurement beam (111′) and at least a second laser (112) being adapted to emit a second measurement beam (112′). The laser sensor module further comprises an optical device (150) being arranged to redirect the first measurement beam (111′) and the second measurement beam (112′) such that the first measurement beam (111′) and the second measurement beam enclose an angle between 45° and 135°. The laser sensor module comprises one detector (120) being adapted to determine at least a first self-mixing interference signal of a first optical wave within a first laser cavity of the first laser (111) and at least a second self-mixing interference signal of a second optical wave within a second laser cavity of the second laser (112). This configuration enables determination of an average velocity of the particles despite of the fact that it is not possible to determine the components of the velocity vector. The introduced error by means of statistical variations is acceptable because the number of detected particles scales with the cubic root of the particle velocity. The invention further describes a particle sensor (100) comprising such a laser sensor module, a corresponding method and computer program product. The invention enables a simple and low-cost particle sensor (100) for detecting small particles based on laser self-mixing interference.
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