Frequency detuning analysis in multi-chirp range-selective digital holography with temporal heterodyning.

Area of Science:

• Optical Engineering
• Metrology
• Signal Processing

Background:

• Range-selective digital holography (RSDH) integrates digital holography with FMCW chirped lidar for depth-resolved imaging.
• Temporal heterodyne FMCW RSDH (TH FMCW RSDH) uses phase-shifting for on-axis holographic imaging.
• Standard RSDH assumes alignment between hologram integration and chirp duration for optimal performance.

Purpose of the Study:

• To develop a theoretical framework for analyzing local oscillator (LO) detuning effects in TH FMCW RSDH under multi-chirp integration.
• To investigate the impact of LO detuning on range resolution and hologram strength.
• To experimentally validate the theoretical model.

Main Methods:

• Theoretical modeling of LO detuning in TH FMCW RSDH with multi-chirp integration.
• Experimental validation using a time-of-flight (ToF) camera for phase-shifting and integration.
• Analysis of hologram strength and range resolution as a function of LO frequency shift.

Main Results:

• The optimal LO frequency shift for maximum hologram strength can deviate from the nominal range-dependent value when hologram integration spans multiple chirps.
• LO detuning affects both hologram strength and range resolution.
• Experimental results confirm the theoretical predictions regarding optimal LO frequency shifts.

Conclusions:

• The assumption of aligned hologram integration and chirp duration is not always valid in multi-chirp systems.
• Optimizing LO frequency shift is crucial for maximizing hologram strength and performance in multi-chirp RSDH systems.
• Findings offer insights for enhancing both TH and non-TH FMCW RSDH systems.