## The effects of reduced bit depth on optical coherence tomography phase data |

Optics Express, Vol. 20, Issue 14, pp. 15654-15668 (2012)

http://dx.doi.org/10.1364/OE.20.015654

Acrobat PDF (1459 KB)

### Abstract

Past studies of the effects of bit depth on OCT magnitude data concluded that 8 bits of digitizer resolution provided nearly the same image quality as a 14-bit digitizer. However, such studies did not assess the effects of bit depth on the accuracy of phase data. In this work, we show that the effects of bit depth on phase data and magnitude data can differ significantly. This finding has an important impact on the design of phase-resolved OCT systems, such as those measuring motion and the birefringence of samples, particularly as one begins to consider the tradeoff between bit depth and digitizer speed.

© 2012 OSA

## 1. Introduction

1. V. J. Srinivasan, D. C. Adler, Y. L. Chen, I. Gorczynska, R. Huber, J. S. Duker, J. S. Schuman, and J. G. Fujimoto, “Ultrahigh-speed optical coherence tomography for three-dimensional and en face imaging of the retina and optic nerve head,” Invest. Ophthalmol. Vis. Sci. **49**(11), 5103–5110 (2008). [CrossRef] [PubMed]

2. W. Wieser, B. Biedermann, T. Klein, C. Eigenwillig, and R. Huber, “Multi-megahertz OCT: high quality 3D imaging at 20 million A-scans and 4.5 GVoxels per second,” Opt. Express **18**(14), 14685–14704 (2010). [CrossRef] [PubMed]

3. D. C. Adler, R. Huber, and J. G. Fujimoto, “Phase-sensitive optical coherence tomography at up to 370,000 lines per second using buffered Fourier domain mode-locked lasers,” Opt. Lett. **32**(6), 626–628 (2007). [CrossRef] [PubMed]

4. C. Joo, T. Akkin, B. Cense, B. H. Park, and J. F. de Boer, “Spectral-domain optical coherence phase microscopy for quantitative phase-contrast imaging,” Opt. Lett. **30**(16), 2131–2133 (2005). [CrossRef] [PubMed]

5. G. Liu, M. Rubinstein, A. Saidi, W. Qi, A. Foulad, B. Wong, and Z. Chen, “Imaging vibrating vocal folds with a high speed 1050 nm swept source OCT and ODT,” Opt. Express **19**(12), 11880–11889 (2011). [CrossRef] [PubMed]

6. J. Zhang, W. Jung, J. S. Nelson, and Z. Chen, “Full range polarization-sensitive Fourier domain optical coherence tomography,” Opt. Express **12**(24), 6033–6039 (2004). [CrossRef] [PubMed]

7. E. Gotzinger, M. Pircher, and C. K. Hitzenberger, “High speed spectral domain polarization sensitive optical coherence tomography of the human retina,” Opt. Express **13**(25), 10217–10229 (2005). [CrossRef] [PubMed]

2. W. Wieser, B. Biedermann, T. Klein, C. Eigenwillig, and R. Huber, “Multi-megahertz OCT: high quality 3D imaging at 20 million A-scans and 4.5 GVoxels per second,” Opt. Express **18**(14), 14685–14704 (2010). [CrossRef] [PubMed]

8. B. D. Goldberg, B. J. Vakoc, W-Y Oh, M. J. Suter, S. Waxman, M. I. Freilich, B. E. Bouma, and G. J. Tearney, “Performance of reduced bit-depth acquisition for optical frequency domain imaging,” Opt. Express **17**(19), 16957–16968 (2009). [CrossRef] [PubMed]

10. R. Huber, D. C. Adler, and J. G. Fujimoto, “Buffered Fourier domain mode locking: unidirectional swept laser sources for optical coherence tomography imaging at 370,000 lines/s,” Opt. Lett. **31**(20), 2975–2977 (2006). [CrossRef] [PubMed]

## 2. Background/Theory

### 2.1. The origin of phase in OCT data

*t*, once resampled to be linear in wavenumber, bears the following form: where

*A*(

*k*) accounts for the source spectrum, spectrometer efficiency, and line camera pixel non-uniformity;

*R*and

_{R}*R*are the reflectivities of the reference and sample, respectively;

_{S}*n*is the spatially averaged index of refraction (assumed constant in time); and Δ

*z*is the displacement of the sample reflector from the position of zero optical pathlength relative to the position of the reference reflector to within a multiplicative constant of the pixel spacing in the

*z*domain. The sum of Δ

*z*and

*δz*(

*t*) yields the exact position of the sample reflector. The Fourier transform (FT) of the interferogram yields a complex number encoding the position (in depth) and intensity (i.e., refractive index contrast) of reflectors within the sample. The A-scan is calculated from the magnitude of

*I*(

*z*,

*t*), the FT of

*i*(

*k*,

*t*), centered at

*z*= 2

*n*(Δ

*z*+

*δz*(

*t*)). Note that for simplicity, Eq. (1) omits the DC terms because they do not contribute to the interferometric signal of interest.

3. D. C. Adler, R. Huber, and J. G. Fujimoto, “Phase-sensitive optical coherence tomography at up to 370,000 lines per second using buffered Fourier domain mode-locked lasers,” Opt. Lett. **32**(6), 626–628 (2007). [CrossRef] [PubMed]

12. M. A. Choma, A. K. Ellerbee, C. Yang, T. Creazzo, and J. A. Izatt, “Spectral-domain phase microscopy,” Opt. Lett. **30**(10), 1162–1164 (2005). [CrossRef] [PubMed]

15. A. K. Ellerbee and J. A. Izatt, “Phase retrieval in low-coherence interferometric microscopy,” Opt. Lett. **32**(4), 388–390 (2007). [CrossRef] [PubMed]

*δn*if the position or thickness of the object remains stationary.

### 2.2. Sources of noise in OCT systems

*n*(

*k*), measured by the single pixel receiving wavenumber

*k*. The measured signal is

*y*(

*k*) =

*i*(

*k*) +

*n*(

*k*).

*B*-bit digitizer is exactly

*B*bits due to errors in the quantization thresholding circuitry and the inherent noise present in electronics [19]. Hence, an ideal

*B*-bit quantizer and a real

*B*-bit ADC have noise characteristics given by Eq. (3) and Eq. (4), respectively, where

### 2.3. Effects of noise on the measurement of OCT phase

*i*(

*k*) and additive noise

*n*(

*k*) such that

*y*(

*k*) =

*i*(

*k*) +

*n*(

*k*). After applying the discrete Fourier transform (DFT), we obtain transformed signal and noise vectors

*I*(

*z*) and

*N*(

*z*), respectively. Previous attempts to derive an analytical expression relating

*n*(

*k*) to the noise in ∠

*Y*(

*z*) employed a semi-deterministic model: additive shot noise was assumed to be the dominant noise source [12

12. M. A. Choma, A. K. Ellerbee, C. Yang, T. Creazzo, and J. A. Izatt, “Spectral-domain phase microscopy,” Opt. Lett. **30**(10), 1162–1164 (2005). [CrossRef] [PubMed]

*N*(

*z*) was treated as a complex stochastic process with constant, deterministic magnitude (i.e., the standard deviation of the photoelectron shot noise) and random phase. The standard deviation of phase error was assumed to be the largest phase deviation that could be imparted to the signal by the noise variable of constant magnitude: where

*σ*is the standard deviation of the phase change caused by noise. In contrast with [12

_{δθ}12. M. A. Choma, A. K. Ellerbee, C. Yang, T. Creazzo, and J. A. Izatt, “Spectral-domain phase microscopy,” Opt. Lett. **30**(10), 1162–1164 (2005). [CrossRef] [PubMed]

## 3. Methods

### 3.1. Simulation of reduced ADC resolution

20. D. Hillmann, G. Huttmann, and P. Koch, “Using nonequispaced fast Fourier transformation to process optical coherence tomography signals,” Proc. SPIE **7372**. 73720R (2009). [CrossRef]

21. S. Vergnole, D. Lvesque, and G. Lamouche, “Experimental validation of an optimized signal processing method to handle non-linearity in swept-source optical coherence tomography,” Opt. Express **18**(10), 10446–10461 (2010). [CrossRef] [PubMed]

21. S. Vergnole, D. Lvesque, and G. Lamouche, “Experimental validation of an optimized signal processing method to handle non-linearity in swept-source optical coherence tomography,” Opt. Express **18**(10), 10446–10461 (2010). [CrossRef] [PubMed]

8. B. D. Goldberg, B. J. Vakoc, W-Y Oh, M. J. Suter, S. Waxman, M. I. Freilich, B. E. Bouma, and G. J. Tearney, “Performance of reduced bit-depth acquisition for optical frequency domain imaging,” Opt. Express **17**(19), 16957–16968 (2009). [CrossRef] [PubMed]

9. Z. Lu, D. K. Kasaragod, and S. J. Matcher, “Performance comparison between 8- and 14-bit- depth imaging in polarization-sensitive swept-source optical coherence tomography,” Biomed. Opt. Express **4**(2), 794–804 (2011). [CrossRef]

*N*-bit numbers, where

*N*is an integer, by first dividing the 12-bit number by 2

^{12−N}and then rounding the fractional part to the nearest integer. This method, however, produces an output with an ENOB less than

*N*: the 12-bit input already contains QN, and rounding adds additional QN that makes the total noise greater than that of a true

*N*-bit sequence. To accurately round from 12 bits to

*N*bits, one must account for both the noise added by the

*N*-bit quantizer and the QN of a 12-bit sequence, so that the sum of the original 12-bit QN and the newly added QN yields the desired QN of a true

*N*-bit sequence. In [8

8. B. D. Goldberg, B. J. Vakoc, W-Y Oh, M. J. Suter, S. Waxman, M. I. Freilich, B. E. Bouma, and G. J. Tearney, “Performance of reduced bit-depth acquisition for optical frequency domain imaging,” Opt. Express **17**(19), 16957–16968 (2009). [CrossRef] [PubMed]

9. Z. Lu, D. K. Kasaragod, and S. J. Matcher, “Performance comparison between 8- and 14-bit- depth imaging in polarization-sensitive swept-source optical coherence tomography,” Biomed. Opt. Express **4**(2), 794–804 (2011). [CrossRef]

*N*+

*F*, where

*F*∈ (0, 1). Throughout this work, we assume for simplicity that an ADC with a nominal resolution of

*N*+ 1 bits will have an ENOB between

*N*and

*N*+ 1. Not all ADCs satisfy this requirement, but our analysis can be straightforwardly extended for those other cases.

*N*+ 1)-bit ADC is not an ideal (

*N*+ 1)-bit quantizer (i.e., an (

*N*+ 1)-bit rounding operation), various error sources combine to reduce the true resolution of the ADC. The effects of these error sources may be modeled as an additive noise source

*n*, placed before the ideal quantizer [19]. As a result, the ENOB of the ADC is

_{e}*B*=

*N*+

*F*bits, where

*N*is an integer and

*F*∈ (0, 1).

*n*of the appropriate variance and added it to the raw data. An (

_{e}*N*+ 1)-bit quantizer was then implemented using rounding as in [8

**17**(19), 16957–16968 (2009). [CrossRef] [PubMed]

9. Z. Lu, D. K. Kasaragod, and S. J. Matcher, “Performance comparison between 8- and 14-bit- depth imaging in polarization-sensitive swept-source optical coherence tomography,” Biomed. Opt. Express **4**(2), 794–804 (2011). [CrossRef]

- Generate the spectrum of the ADC output using the DFT. (Note that the length of the DFT is set to an integer multiple of the period of the sinusoid to eliminate windowing effects).
- Calculate the SNR of the ADC output. Determine the total noise energy by summing the squared magnitude of all DFT coefficients excluding the signal and DC.
- Calculate the ENOB using ENOB = (SNR − 1.76)/6.02, where SNR is in dB.

### 3.2. Experimental design

11. A. B. Vakhtin, D. J. Kane, W. R. Wood, and K. A. Peterson, “Common-path interferometer for frequency-domain optical coherence tomography,” App. Opt. **42**(34), 6953–6958 (2003). [CrossRef]

14. A. K. Ellerbee, T. L. Creazzo, and J. A. Izatt, “Investigating nanoscale cellular dynamics with cross-sectional spectral domain phase microscopy,” Opt. Express **15**(13), 8115–8124 (2007). [CrossRef] [PubMed]

*λ*

_{0}= 1325 nm, Δ

*λ*= 150 nm). The lateral resolution of the system was 12

_{FWHM}*μ*m (NA = 0.08). All interferograms were captured with a 12-bit digitizer operating at an A-scan rate of 5.5 kHz (high-sensitivity mode). At this A-scan rate and in the CP configuration, the sensitivity is 90 dB. The system was operated in CP mode by closing the aperture of the reference arm. A schematic of the system is shown in Fig. 5. We acquired 8000 A-scans and calculated the phase of the DFT for the pixel at depth 2

*n*Δ

*z*, corresponding to the position of the bottom (sample) surface. This experimental protocol was repeated after changing the reflectivity of the coverslip by adding a liquid droplet of water or index-matching gel to its bottom surface. All reported phase sensitivities are given by the standard deviation of 8000 measurements for a given condition. Our choice of 8000 was arbitrary but satisfactory, as we observed little phase drift over the course of the experiments.

## 4. Results and discussion

*λ*/10. Such vibrations could result in time-varying thicknesses that cause direct rotation of the complex signal vector - which is different from the effect of additive noise - leading to additional phase noise.

*P*is the DFT length (typically the number of camera pixels) and the

*K*are constants.

_{i}*K*

_{1}(

*R*+

_{S}*R*) is the variance of the shot noise and

_{R}*K*

_{2}(

*R*+

_{S}*R*)

_{R}^{2}is the variance of the RIN;

*K*

_{3}is the proportionality factor relating

*K*depend on a number of system parameters such as source power spectral density, spectrometer efficiency, and responsivity [16

_{i}16. S. H. Yun, G. J. Tearney, J. F. de Boer, N. Iftimia, and B. E. Bouma, “High-speed optical frequency-domain imaging,” Opt. Express **11**(22), 2953–2963 (2003). [CrossRef] [PubMed]

17. R. Leitgeb, C. K. Hitzenberger, and A. F. Fercher, “Performance of fourier domain vs. time domain optical coherence tomography,” Opt. Express **11**(8), 889–894 (2003). [CrossRef] [PubMed]

*R*(an accurate approximation when shot noise and RIN are small compared to all other additive noise sources), then by Eq. (12) we would expect the displacement sensitivity for the glass-water sample to be 3.33 times as large as for glass-air. The experimental results showed a factor of 2.64 at 12 bits that increased to 3.15 at 7 bits. Similarly, a simplified calculation for the gel sample would indicate a sensitivity difference between air and gel of 11.8, while the experimental result was 9.48 at 12 bits and increased to 11.4 at 7 bits. The discrepancy between the expected and actual values deceases with ENOB because QN, which is independent of

_{S}*R*, becomes more dominant in the numerator of Eq. (12).

_{S}23. D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, and J. G. Fujimoto, “Optical Coherence Tomography,” Science **254**(5035), 1178–1181 (1991). [CrossRef] [PubMed]

**17**(19), 16957–16968 (2009). [CrossRef] [PubMed]

**4**(2), 794–804 (2011). [CrossRef]

*π*,

*π*], phase data should be unwrapped in time to track changes over large displacements (each

*π*phase corresponds to a displacement of

*λ*

_{0}/4

*n*). Hence, displacements that correspond to more than a

*π*phase change within a single time interval cannot be accurately tracked. Moreover, phase wrapping will occur during the time step when the phase noise is sufficiently high, making the phase data ambiguous. To the extent that quantization noise affects phase noise, this can cause additional problems for accurately measuring phase data.

## 5. Conclusions

**30**(10), 1162–1164 (2005). [CrossRef] [PubMed]

## Acknowledgments

## References and links

1. | V. J. Srinivasan, D. C. Adler, Y. L. Chen, I. Gorczynska, R. Huber, J. S. Duker, J. S. Schuman, and J. G. Fujimoto, “Ultrahigh-speed optical coherence tomography for three-dimensional and en face imaging of the retina and optic nerve head,” Invest. Ophthalmol. Vis. Sci. |

2. | W. Wieser, B. Biedermann, T. Klein, C. Eigenwillig, and R. Huber, “Multi-megahertz OCT: high quality 3D imaging at 20 million A-scans and 4.5 GVoxels per second,” Opt. Express |

3. | D. C. Adler, R. Huber, and J. G. Fujimoto, “Phase-sensitive optical coherence tomography at up to 370,000 lines per second using buffered Fourier domain mode-locked lasers,” Opt. Lett. |

4. | C. Joo, T. Akkin, B. Cense, B. H. Park, and J. F. de Boer, “Spectral-domain optical coherence phase microscopy for quantitative phase-contrast imaging,” Opt. Lett. |

5. | G. Liu, M. Rubinstein, A. Saidi, W. Qi, A. Foulad, B. Wong, and Z. Chen, “Imaging vibrating vocal folds with a high speed 1050 nm swept source OCT and ODT,” Opt. Express |

6. | J. Zhang, W. Jung, J. S. Nelson, and Z. Chen, “Full range polarization-sensitive Fourier domain optical coherence tomography,” Opt. Express |

7. | E. Gotzinger, M. Pircher, and C. K. Hitzenberger, “High speed spectral domain polarization sensitive optical coherence tomography of the human retina,” Opt. Express |

8. | B. D. Goldberg, B. J. Vakoc, W-Y Oh, M. J. Suter, S. Waxman, M. I. Freilich, B. E. Bouma, and G. J. Tearney, “Performance of reduced bit-depth acquisition for optical frequency domain imaging,” Opt. Express |

9. | Z. Lu, D. K. Kasaragod, and S. J. Matcher, “Performance comparison between 8- and 14-bit- depth imaging in polarization-sensitive swept-source optical coherence tomography,” Biomed. Opt. Express |

10. | R. Huber, D. C. Adler, and J. G. Fujimoto, “Buffered Fourier domain mode locking: unidirectional swept laser sources for optical coherence tomography imaging at 370,000 lines/s,” Opt. Lett. |

11. | A. B. Vakhtin, D. J. Kane, W. R. Wood, and K. A. Peterson, “Common-path interferometer for frequency-domain optical coherence tomography,” App. Opt. |

12. | M. A. Choma, A. K. Ellerbee, C. Yang, T. Creazzo, and J. A. Izatt, “Spectral-domain phase microscopy,” Opt. Lett. |

13. | M. V. Sarunic, S. Weinberg, and J. A. Izatt, “Full-field swept-source phase microscopy,” Opt. Lett. |

14. | A. K. Ellerbee, T. L. Creazzo, and J. A. Izatt, “Investigating nanoscale cellular dynamics with cross-sectional spectral domain phase microscopy,” Opt. Express |

15. | A. K. Ellerbee and J. A. Izatt, “Phase retrieval in low-coherence interferometric microscopy,” Opt. Lett. |

16. | S. H. Yun, G. J. Tearney, J. F. de Boer, N. Iftimia, and B. E. Bouma, “High-speed optical frequency-domain imaging,” Opt. Express |

17. | R. Leitgeb, C. K. Hitzenberger, and A. F. Fercher, “Performance of fourier domain vs. time domain optical coherence tomography,” Opt. Express |

18. | A. Oppenheim and R. Schafer, |

19. | W. Kester, |

20. | D. Hillmann, G. Huttmann, and P. Koch, “Using nonequispaced fast Fourier transformation to process optical coherence tomography signals,” Proc. SPIE |

21. | S. Vergnole, D. Lvesque, and G. Lamouche, “Experimental validation of an optimized signal processing method to handle non-linearity in swept-source optical coherence tomography,” Opt. Express |

22. | C. Copeland and A. K. Ellerbee, “The effects of different gold standards on the assessment of the accuracy of different resampling techniques for optical coherence tomography,” Proc. SPIE . 8225–8237 (2012). |

23. | D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, and J. G. Fujimoto, “Optical Coherence Tomography,” Science |

**OCIS Codes**

(030.4280) Coherence and statistical optics : Noise in imaging systems

(100.5070) Image processing : Phase retrieval

(170.3890) Medical optics and biotechnology : Medical optics instrumentation

(170.4500) Medical optics and biotechnology : Optical coherence tomography

**ToC Category:**

Medical Optics and Biotechnology

**History**

Original Manuscript: May 11, 2012

Revised Manuscript: June 18, 2012

Manuscript Accepted: June 19, 2012

Published: June 26, 2012

**Virtual Issues**

Vol. 7, Iss. 9 *Virtual Journal for Biomedical Optics*

**Citation**

William A. Ling and Audrey K. Ellerbee, "The effects of reduced bit depth on optical coherence tomography phase data," Opt. Express **20**, 15654-15668 (2012)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-20-14-15654

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### References

- V. J. Srinivasan, D. C. Adler, Y. L. Chen, I. Gorczynska, R. Huber, J. S. Duker, J. S. Schuman, and J. G. Fujimoto, “Ultrahigh-speed optical coherence tomography for three-dimensional and en face imaging of the retina and optic nerve head,” Invest. Ophthalmol. Vis. Sci.49(11), 5103–5110 (2008). [CrossRef] [PubMed]
- W. Wieser, B. Biedermann, T. Klein, C. Eigenwillig, and R. Huber, “Multi-megahertz OCT: high quality 3D imaging at 20 million A-scans and 4.5 GVoxels per second,” Opt. Express18(14), 14685–14704 (2010). [CrossRef] [PubMed]
- D. C. Adler, R. Huber, and J. G. Fujimoto, “Phase-sensitive optical coherence tomography at up to 370,000 lines per second using buffered Fourier domain mode-locked lasers,” Opt. Lett.32(6), 626–628 (2007). [CrossRef] [PubMed]
- C. Joo, T. Akkin, B. Cense, B. H. Park, and J. F. de Boer, “Spectral-domain optical coherence phase microscopy for quantitative phase-contrast imaging,” Opt. Lett.30(16), 2131–2133 (2005). [CrossRef] [PubMed]
- G. Liu, M. Rubinstein, A. Saidi, W. Qi, A. Foulad, B. Wong, and Z. Chen, “Imaging vibrating vocal folds with a high speed 1050 nm swept source OCT and ODT,” Opt. Express19(12), 11880–11889 (2011). [CrossRef] [PubMed]
- J. Zhang, W. Jung, J. S. Nelson, and Z. Chen, “Full range polarization-sensitive Fourier domain optical coherence tomography,” Opt. Express12(24), 6033–6039 (2004). [CrossRef] [PubMed]
- E. Gotzinger, M. Pircher, and C. K. Hitzenberger, “High speed spectral domain polarization sensitive optical coherence tomography of the human retina,” Opt. Express13(25), 10217–10229 (2005). [CrossRef] [PubMed]
- B. D. Goldberg, B. J. Vakoc, W-Y Oh, M. J. Suter, S. Waxman, M. I. Freilich, B. E. Bouma, and G. J. Tearney, “Performance of reduced bit-depth acquisition for optical frequency domain imaging,” Opt. Express17(19), 16957–16968 (2009). [CrossRef] [PubMed]
- Z. Lu, D. K. Kasaragod, and S. J. Matcher, “Performance comparison between 8- and 14-bit- depth imaging in polarization-sensitive swept-source optical coherence tomography,” Biomed. Opt. Express4(2), 794–804 (2011). [CrossRef]
- R. Huber, D. C. Adler, and J. G. Fujimoto, “Buffered Fourier domain mode locking: unidirectional swept laser sources for optical coherence tomography imaging at 370,000 lines/s,” Opt. Lett.31(20), 2975–2977 (2006). [CrossRef] [PubMed]
- A. B. Vakhtin, D. J. Kane, W. R. Wood, and K. A. Peterson, “Common-path interferometer for frequency-domain optical coherence tomography,” App. Opt.42(34), 6953–6958 (2003). [CrossRef]
- M. A. Choma, A. K. Ellerbee, C. Yang, T. Creazzo, and J. A. Izatt, “Spectral-domain phase microscopy,” Opt. Lett.30(10), 1162–1164 (2005). [CrossRef] [PubMed]
- M. V. Sarunic, S. Weinberg, and J. A. Izatt, “Full-field swept-source phase microscopy,” Opt. Lett.31(10), 1462–1464 (2006). [CrossRef] [PubMed]
- A. K. Ellerbee, T. L. Creazzo, and J. A. Izatt, “Investigating nanoscale cellular dynamics with cross-sectional spectral domain phase microscopy,” Opt. Express15(13), 8115–8124 (2007). [CrossRef] [PubMed]
- A. K. Ellerbee and J. A. Izatt, “Phase retrieval in low-coherence interferometric microscopy,” Opt. Lett.32(4), 388–390 (2007). [CrossRef] [PubMed]
- S. H. Yun, G. J. Tearney, J. F. de Boer, N. Iftimia, and B. E. Bouma, “High-speed optical frequency-domain imaging,” Opt. Express11(22), 2953–2963 (2003). [CrossRef] [PubMed]
- R. Leitgeb, C. K. Hitzenberger, and A. F. Fercher, “Performance of fourier domain vs. time domain optical coherence tomography,” Opt. Express11(8), 889–894 (2003). [CrossRef] [PubMed]
- A. Oppenheim and R. Schafer, Discrete-time Signal Processing, 3rd ed. (Prentice Hall, 2009).
- W. Kester, The Data Conversion Handbook (Elsevier, 2005).
- D. Hillmann, G. Huttmann, and P. Koch, “Using nonequispaced fast Fourier transformation to process optical coherence tomography signals,” Proc. SPIE7372. 73720R (2009). [CrossRef]
- S. Vergnole, D. Lvesque, and G. Lamouche, “Experimental validation of an optimized signal processing method to handle non-linearity in swept-source optical coherence tomography,” Opt. Express18(10), 10446–10461 (2010). [CrossRef] [PubMed]
- C. Copeland and A. K. Ellerbee, “The effects of different gold standards on the assessment of the accuracy of different resampling techniques for optical coherence tomography,” Proc. SPIE. 8225–8237 (2012).
- D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, and J. G. Fujimoto, “Optical Coherence Tomography,” Science254(5035), 1178–1181 (1991). [CrossRef] [PubMed]

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