Passive heterodyning method for dual-beam phase difference measurement and compensation

Area of Science:

• Optical Imaging
• Interferometry
• Signal Processing

Background:

• Synthetic aperture optical imaging systems are crucial for advanced imaging.
• Optical path difference (OPD) significantly impacts interferometric imaging quality.
• Current OPD correction methods often rely on mechanical structures.

Purpose of the Study:

• To present a novel passive laser heterodyne measurement approach for OPD correction.
• To overcome the limitations of conventional mechanical compensation techniques.
• To propose a digital correction strategy for synthetic aperture systems.

Main Methods:

• Utilizing a laser as the local oscillator (LO) signal for passive heterodyne measurement.
• Analyzing beat frequency components generated from the superposition of independent lasers and incoherent broadband light.
• Employing two passive heterodyne units to detect a common light source and calculating OPD via cross-correlation of beat frequency signals.

Main Results:

• Beat frequency components were observed and extracted from the superposition of different light sources.
• The optical path difference was successfully ascertained using the cross-correlation of beat frequency signals.
• Digital compensation techniques were demonstrated for precise phase matching.

Conclusions:

• The passive laser heterodyne approach offers an effective method for OPD measurement.
• This technique provides a viable digital correction strategy for synthetic aperture optical imaging.
• The proposed method surpasses conventional dual-beam superposition techniques in terms of correction capabilities.