Expand this Topic clickable element to expand a topic
Skip to content
Optica Publishing Group
Journal Home About Issues in Progress Current Issue All Issues Feature Issues

Heterodyne Fourier domain optical coherence tomography for full range probing with high axial resolution

Adrian H. Bachmann, Rainer A. Leitgeb, and Theo Lasser

Open Access Open Access

Abstract

One of the main drawbacks of Fourier domain optical coherence tomography (FDOCT) is the limited measurement depth range. Phase shifting techniques allow reconstructing the complex sample signal resulting in a doubled depth range. In current complex FDOCT realizations the phase shift is introduced via a reference path length modulation, which causes chromatic phase errors especially if broad bandwidth light sources are employed. With acousto-optic frequency shifters in the reference and sample arm, and the detector being locked to the resulting beating frequency, the signal is quadrature detected at high speed. The beating signal frequency is the same for all wavelengths allowing for achromatic complex reconstruction. With a Ti: Sapphire laser at 800 nm and spectral width of 130nm, a heterodyne complex FDOCT system is realized with 20kHz line rate and an axial resolution of 4μm.

©2006 Optical Society of America

Full Article  |  PDF Article
More Like This
Dual beam heterodyne Fourier domain optical coherence tomography

Adrian H. Bachmann, Roland Michaely, Theo Lasser, and Rainer A. Leitgeb
Opt. Express 15(15) 9254-9266 (2007)

Full range polarization-sensitive Fourier domain optical coherence tomography

Jun Zhang, Woonggyu Jung, J. Stuart Nelson, and Zhongping Chen
Opt. Express 12(24) 6033-6039 (2004)

Phase-shifting algorithm to achieve high-speed long-depth-range probing by frequency-domain optical coherence tomography

Rainer A. Leitgeb, Christoph K. Hitzenberger, Adolf F. Fercher, and Tomasz Bajraszewski
Opt. Lett. 28(22) 2201-2203 (2003)

View More...

Cited By

Optica participates in Crossref's Cited-By Linking service. Citing articles from Optica Publishing Group journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (6)
Fig. 1.
Fig. 1. Simulation of complex FDOCT signal reconstruction with chromatic phase shifting. Mirror terms in the left half (P*, grey shaded area) are not totally suppressed. The signals are normalized to the true signal peak amplitudes (P) in the right half space. The ratio between P* and P indicates the mirror term suppression. The simulation supposes a Gaussian spectral distribution with a spectral width (FWHM) of 20nm (black), 40nm (red), 90nm (green) and 130nm (blue) respectively. The central wavelengths are 800nm for all cases.

Download Full Size | PDF

Fig. 2.
Fig. 2. The three plotted curves show the suppression ratio of P* (mirror term) with respect to P (signal peak) for three different central wavelengths of the light source depending on optical bandwidth (λ 0=550nm (blue), λ 0=800nm (red), λ 0=1300nm (green)). Above -40dB mirror terms become visible and the reconstruction algorithm fails. The “noisy” characteristics of the curves at larger bandwidths are due to leakage after discrete FFT.

Download Full Size | PDF

Fig. 3.
Fig. 3. Logarithmic spectral characteristics of the two pigtailed AOFS.

Download Full Size | PDF

Fig. 4.
Fig. 4. Mach-Zehnder like interferometer comprising: Ti:Sapphire light source (LS), 90:10 fiber coupler (FC), AOFS shifting the light fields by ωR,S, translation stage (TS), dispersion compensation (DC), 50:50 beamsplitter (BS), galvo scanners (X-Y scan), camera lens (CL). Box in top left corner shows: (a) beating signal; (b) camera trigger; (c) camera exposure; (d) brackets indicate the frames used for complex two-frame reconstruction; different colors indicate frames used for differential complex technique.

Download Full Size | PDF

Fig. 5.
Fig. 5. (a) Tomogram of a fingernail fold region with standard FDOCT and no DC correction. The zero-delay is clearly visible due to the strong DC signal (bright line in the center). (b) As (a) but with calculated DC correction. (c) As (a) but reconstruction of complex signal according to differential complex method (see Eq.(5)) described in §2.2. (d) As (a) but reconstruction of complex signal according to Eq.(4) in §2.1 with a calculated DC correction. All tomograms are based on the same dataset. The tomogram depth shown is 1.75mm (in air).

Download Full Size | PDF

Fig. 6.
Fig. 6. (a)-(d) Same remarks as for Fig. 5. In-vivo object was a fingertip of an adult and the tomogram depth shown is 1.95mm (in air).

Download Full Size | PDF

Equations (7)

Equations on this page are rendered with MathJax. Learn more.

I ( k ) = I R ( k ) + I S ( k ) + ∑ i , j ; i ≠ j E S , i ( k ) E S , j * ( k ) + ∑ i E R ( k ) E S , i * ( k ) + c . c ,
I AC k t = 2 ∑ i I R ( k ) I S , i ( k ) cos ( Ω t − Ψ i ) ,
I AC , int k t = 2 ∑ i I R ( k ) I S , i ( k ) cos ( Ω t − Ψ i ) sin c ( τ Ω 2 π ) ,
I ˜ ( k ) = I k t 0 − jI ( k , t 0 + π 2 Ω ) ,
I ˜ 2 x 2 ( k ) = I ˜ k t 0 − I ˜ ( k , t 0 + π Ω ) =
= [ I AC ( k , t 0 ) − I AC ( k , t 0 + π Ω ) ] − j [ I AC ( k , t 0 + π 2 Ω ) − I AC ( k , t 0 + 3 π 2 Ω ) ] =
= 2 ( I AC k t 0 − jI AC ( k , t 0 + π 2 Ω ) ) .
Select as filters
Select Topics Cancel
Top
       
© Copyright 2024 | Optica Publishing Group. All rights reserved, including rights for text and data mining and training of artificial technologies or similar technologies.
Privacy | Terms of Use