Table 1.

Comparing phase-shifting methods.

Parameter	Pivot offsetting at the sample arm	Pivot offsetting at the reference arm	PZT at the reference arm
Max suppression ratio (with a paperboard)	25 [dB]	21 [dB]	20 [dB]
Image quality	Best complex conjugate suppression	Moderate complex conjugate suppression	Moderate complex conjugate suppression
Additional hardware requirement	None	One additional galvo-scanner	PZT and power amplifier
Scanning beam pattern	Fixed	Changeable	Changeable
Data acquisition	Full acquisition speed over 100,000 A-scans	Full acquisition speed over 100,000 A-scans	Restriction of phase shifting by limited PZT displacement
Image processing	Standard FD-OCT algorithm	Required additional DC subtraction algorithm	Required additional DC subtraction algorithm
Potential problems	Lower complex conjugate suppression by sample motion. Difficulty to implement in existing OCT system.	Lower complex conjugate suppression by sample motion. Increased coherence noise caused by the reference beam intensity variations.	Lower complex conjugate suppression by sample motion. Increased coherence noise caused by the reference beam intensity variations.