40
Z. Amini et al.
Fig. 3.1 Block-diagram of optical coherence tomography
In this chapter, we discuss the structural information of OCT with focus on its
denoising. Several publications have addressed the theory and performance of OCT
imaging, but very few works have principal information for applications like denoising.
Speckle noise is dominant in OCT and causes erroneous interpretation similar to
ultrasound images. In time-domain techniques, axial movement of reference reflector
would produce interferometric fringes and this movement was the main reason of
low acquisition speed. In Fourier domain OCT, the fixed reference reflector leads to
higher speeds up to several hundred thousand lines per second [2]. The resolution of
Fourier domain OCT is also high in both axial and lateral directions.
Regarding the resolution of OCT images, a simple assumption is Gaussian profile
sample arm beam in the region of the beam focus. This approach is a reasonable
approximation and provides that spot size is proportional to the numerical aperture
(N A) of the sample arm focusing optics, while depth of focus is proportional to
N A
2 . However, a more correct model is to treat the sample arm of an OCT system
as a reflection-mode scanning confocal microscope. In such a case, lateral and axial
resolutions are:
lateral_resolution δ x 0.37
λ 0
N A
(3.1)
Axial_resolution δ z
2 ln(2)
π
λ
2
0
λ
(3.2)
Z. Amini et al.
Fig. 3.1 Block-diagram of optical coherence tomography
In this chapter, we discuss the structural information of OCT with focus on its
denoising. Several publications have addressed the theory and performance of OCT
imaging, but very few works have principal information for applications like denoising.
Speckle noise is dominant in OCT and causes erroneous interpretation similar to
ultrasound images. In time-domain techniques, axial movement of reference reflector
would produce interferometric fringes and this movement was the main reason of
low acquisition speed. In Fourier domain OCT, the fixed reference reflector leads to
higher speeds up to several hundred thousand lines per second [2]. The resolution of
Fourier domain OCT is also high in both axial and lateral directions.
Regarding the resolution of OCT images, a simple assumption is Gaussian profile
sample arm beam in the region of the beam focus. This approach is a reasonable
approximation and provides that spot size is proportional to the numerical aperture
(N A) of the sample arm focusing optics, while depth of focus is proportional to
N A
2 . However, a more correct model is to treat the sample arm of an OCT system
as a reflection-mode scanning confocal microscope. In such a case, lateral and axial
resolutions are:
lateral_resolution δ x 0.37
λ 0
N A
(3.1)
Axial_resolution δ z
2 ln(2)
π
λ
2
0
λ
(3.2)