Joint aperture detection for speckle reduction and increased collection efficiency in ophthalmic MHz OCT

Abstract

Joint-aperture optical coherence tomography (JA-OCT) is an angle-resolved OCT method, in which illumination from an active channel is simultaneously probed by several passive channels. JA-OCT increases the collection efficiency and effective sensitivity of the OCT system without increasing the power on the sample. Additionally, JA-OCT provides angular scattering information about the sample in a single acquisition, so the OCT imaging speed is not reduced. Thus, JA-OCT is especially suitable for ultra high speed in-vivo imaging. JA-OCT is compared to other angle-resolved techniques, and the relation between joint aperture imaging, adaptive optics, coherent and incoherent compounding is discussed. We present angle-resolved imaging of the human retina at an axial scan rate of 1.68 MHz, and demonstrate the benefits of JA-OCT: Speckle reduction, signal increase and suppression of specular and parasitic reflections. Moreover, in the future JA-OCT may allow for the reconstruction of the full Doppler vector and tissue discrimination by analysis of the angular scattering dependence.

High-speed OCT light sources and systems [Invited]

“…However, even in this case, only half of the reference power contributes to the OCT signal, which again leads to a 3 dB sensitivity penalty. In joint-aperture (JA) OCT, multiple passive channels detect light backscattered from outside the illumination aperture [149,150], which increases sensitivity, data rate and image quality, but not A-scan rate.…”

Time-encoded Raman scattering (TICO-Raman) with Fourier domain mode locked (FDML) lasers

“…FDML lasers exhibit the unique feature being capable of wavelength sweep repetition rates well into the MHz range [2,3,[5][6][7][8][9][10], because they do not suffer from inherent physical constraints with respect to wavelength sweep rate [11][12][13][14][15]. Hence, they found widespread applications from ultrafast OCT [16][17][18][19][20], over non-destructive sensing and testing [16,[21][22][23][24] to optical molecular [25] and functional imaging [26,27] and even short laser pulse generation [28].…”

“…Hence, they found widespread applications from ultrafast OCT [16][17][18][19][20], over non-destructive sensing and testing [16,[21][22][23][24] to optical molecular [25] and functional imaging [26,27] and even short laser pulse generation [28]. The extension of the accessible wavelength range of FDML lasers to the 1060nm spectral region [9,[29][30][31][32]] enabled high quality ultra-fast retinal swept source OCT imaging with good penetration into the choroid [5,9,10]. Theses lasers provide a well-defined wavelength sweep over time, where the wavelength output is a sinusoidal sweep with the wavelength being time-encoded (Figure 1, right).…”

Speckle reduction in optical coherence tomography images based on wave atoms

“…The hardware-based approaches include frequency [6][7][8][9] and spatial compoundings. [10][11][12][13][14][15][16][17][18] These hardwarebased approaches are robust ways for speckle suppression as speckle properties vary across wavelengths or different illumination angles. 7 However, these methods require further modification of an existing system and increase a system's complexity and cost.…”