Baseline correction for stray light in log-ratio diode laser absorption measurements

Area of Science:

• Spectroscopy
• Optical Sensing
• Analytical Chemistry

Background:

• Log-ratio detection is widely used for temperature and concentration measurements with tunable diode laser absorption spectroscopy (TDLAS) sensors.
• Practical TDLAS applications often encounter stray light interference on the photodiode.
• This stray light introduces systematic errors not eliminated by standard baseline subtraction techniques.

Purpose of the Study:

• To analyze the factors contributing to systematic errors caused by stray light in TDLAS.
• To develop and present a calibration method for correcting stray light-induced errors.
• To validate the proposed correction method experimentally.

Main Methods:

• Analysis of systematic error sources in log-ratio detection under stray light conditions.
• Development of a novel calibration procedure to compensate for noncommon-mode interference.
• Experimental verification of the calibration method using a simplified setup.

Main Results:

• Identified key factors influencing systematic error magnitude due to stray light.
• Demonstrated the effectiveness of the proposed calibration method in reducing measurement errors.
• Experimental results confirmed the practical applicability of the correction technique.

Conclusions:

• Stray light is a significant source of systematic error in TDLAS sensors employing log-ratio detection.
• The presented calibration method effectively corrects for these errors, enhancing measurement reliability.
• This work provides a practical solution for improving the accuracy of TDLAS-based sensing systems.