Simple and robust speckle detection method for fire and heat detection in harsh environments.

Area of Science:

• Optical Engineering
• Fire Safety Technology
• Sensor Systems

Background:

• Standard laser fire detection relies on optical signal amplitude, susceptible to mechanical noise, dust, and steam interference.
• These limitations hinder performance in harsh environments, leading to false alarms or undetected fires.
• Existing systems struggle with fires lacking visible flames or in areas with significant particulate matter.

Purpose of the Study:

• To develop a robust fire detection technology for challenging industrial environments.
• To overcome the limitations of conventional laser-based fire detection systems.
• To enable reliable fire detection in dusty and mechanically noisy conditions.

Main Methods:

• A standalone laser system utilizing a Linux-based Red Pitaya, a 650 nm laser diode, and a positive-intrinsic-negative photodetector.
• Monitoring random fluctuations in the refractive index caused by heat convection, rather than light intensity or wavelength.
• Analyzing speckle patterns generated by reflected laser light, measuring time traces and frequency noise spectra every 3 seconds.

Main Results:

• Successful laboratory and factory acceptance tests demonstrated the system's efficacy.
• The technology proved capable of detecting fires in simulated harsh and dusty conditions.
• Eight key descriptors were identified for reliable fire identification based on refractive index fluctuations.

Conclusions:

• The developed laser-based system offers a reliable method for fire detection in environments previously unsuitable for such technology.
• By focusing on refractive index changes, the system is immune to dust and steam interference.
• This innovation enhances fire safety in industrial settings, including detecting fires without visible flames.