Modeling of low coherence interferometry using broadband multi-Gaussian light sources

Abstract

Using a low coherence interferometry (LCI) model, a comparison of broadband single-Gaussian and multi-Gaussian light sources has been undertaken. For single-Gaussian sources, the axial resolution improves with the source bandwidth, confirming the coherence length relation that the resolution for single Gaussian sources improves with increasing spectral bandwidth. However, narrow bandwidth light sources result in interferograms with overlapping strata peaks and the loss of individual strata information. For multiple-Gaussian sources with the same bandwidth, spectral side lobes increase, reducing A-scan reliability to show accurate layer information without eliminating the side lobes. The simulations show the conditions needed for the resolution of strata information for broadband light sources using both single and multiple Gaussian models. The potential to use the model to study optical coherence tomography (OCT) light sources including super luminescent diodes (SLDs), as reviewed in this paper, as well as optical delay lines and sample structures could better characterize these LCI and OCT elements. Forecasting misinformation in the interferogram may allow preliminary corrections. With improvement to the LCI-OCT model, more applications are envisaged.

Development of a Free Space, LED Illuminated Spectral-domain Optical Coherence Tomography Setup

“…Table 2 lists distances through which the reflector was translated range from 50 µm to 860 µm. It is of interest to note that a setting of the reflector within the coherence gate of the source rather than at the exact ZPD produced the fringes as previously observed [3,4,5,7]. This quasi-aberrant measurement is often exhibited by readings of near ZPD e.g.…”

“…With quasi-monochromatic sources, the fringes are therefore visible through large path differences. However, where a broadband source illuminates the interferometer, fringes tend to wash out beyond the zero path difference (ZPD) point or the coherence gate of the light source [7,8]. This is the key feature that separates OCT sources from line sources such as Mercury lamps.…”

Characterizing the resolvability of real superluminescent diode sources for application to optical coherence tomography using a low coherence interferometry model

“…In this section, the time-domain OCT method, OCT light source characteristics, and SLD characteristics that are selected and briefly reviewed in previous research 7 and interferometrically investigated in this research, are reviewed more extensively.…”

“…In previous research, 7 tandem Gaussian spectra were simulated, and it was observed that the A-scan resolution degraded with increasing spectral peaks and increasing spectral peak depths; that is, satellite peaks became larger and more numerous, degrading resolution. Though having exceptional bandwidth, many new sources for OCT present broad bandwidth spectra that are significantly non-Gaussian.…”

“…Though having exceptional bandwidth, many new sources for OCT present broad bandwidth spectra that are significantly non-Gaussian. It is more realistic than the previous research model, 7 as it includes the air-tissue boundary's significant reflection, as well as the actual dermal strata refractive indices from dermatological literature. In this study, the work on simulated multiple Gaussian sources 7 has been extended by investigating the empirical sample's stratum depth resolution limit (SDRL) for the real SLD sources reviewed in that research.…”