Complete complex conjugate resolved heterodyne swept-source optical coherence tomography using a dispersive optical...

Area of Science:

• Biomedical Optics
• Optical Imaging
• Coherence Tomography

Background:

• Swept-source optical coherence tomography (SSOCT) offers high sensitivity but faces limitations in imaging depth due to sensitivity falloff and complex conjugate ambiguity.
• Existing methods to resolve complex conjugate ambiguity in SSOCT, like heterodyne complex conjugate-resolved SSOCT (HCCR-SSOCT), often require expensive and lossy optical modulators.
• These modulators can reduce imaging speed or system performance, limiting practical applications of enhanced SSOCT.

Purpose of the Study:

• To demonstrate a novel, cost-effective implementation of HCCR-SSOCT using a dispersive optical delay line (D-ODL) in the reference arm.
• To maintain the benefits of HCCR-SSOCT, including complete complex conjugate artifact resolution and unimpeded imaging speed.
• To introduce a more accessible and versatile approach for advanced SSOCT imaging.

Main Methods:

• Integration of a dispersive optical delay line (D-ODL) into the reference arm of a swept-source optical coherence tomography (SSOCT) system.
• Utilizing the D-ODL to achieve differential phase modulation for heterodyne complex conjugate resolution.
• System characterization using falloff measurements and demonstration of in vivo imaging on human volunteers.

Main Results:

• The D-ODL successfully enabled HCCR-SSOCT, completely resolving complex conjugate ambiguity.
• A doubling of the effective imaging depth range was achieved without any penalty to system sensitivity or resolution.
• The D-ODL approach proved to be low-cost, maintained system performance, and did not require additional signal processing or reduce imaging speed.
• Hardware correction for unbalanced dispersion was facilitated by the D-ODL, enhancing system flexibility.

Conclusions:

• The D-ODL is a viable, low-cost alternative to optical modulators for implementing HCCR-SSOCT.
• This technique significantly extends the imaging depth of SSOCT systems while preserving critical performance metrics.
• The D-ODL-based HCCR-SSOCT is suitable for high-speed, in vivo imaging applications, as demonstrated by anterior segment imaging in humans.