Common path Fourier domain optical coherence tomography based on multiple reflections within the sample arm

Abstract

We present a common path Fourier domain optical coherence tomography (FDOCT) setup where the reference signal arises from multiple reflections within the sample arm. Two configurations are demonstrated. The first is based on a reflective microscope objective while the second is based on a normal (refractive) microscope objective. The second configuration is effectively a Mireau interferometer. We present sensitivity analysis of these setups and images of in vivo skin. Advantages of both common path arrangements include: 1) the reference surface is not close to the sample surface while keeping the optical path lengths matched (so the additional interferometer is not needed) and 2) the user can independently control reference and sample arm power. Additionally, the configuration using the refractive objective ensures that the coherence gate and focus gate always match. A disadvantage is that the reference arm power in certain circumstances is not optimal (i.e. close to saturating the CCD). However, this issue can be removed by a light source of sufficient output power. We believe the idea is scalable and therefore of interest to endoscopy applications. 3 RESEARCH HIGHLIGHTS• Multiple reflections within the sample arm can be beneficial.• We demonstrate a novel common-path Fourier domain OCT based on Mireau interferometer.

256 × 2 SPAD line sensor for time resolved fluorescence spectroscopy

“…A long pass filter is also present further filtering fluorescence above 500 nm. Fluorescence coupled into the MMF was dispersed in a custom spectrometer comprising of a ruled reflection grating (1200 grooves per mm, blaze wavelength 500 nm, Thorlabs GR25-1205) and focusing optics similar to that presented before [45,46]. The spectra were calibrated to cover 500 nm to 600 nm over 256 pixels.…”

Tissue surface as the reference arm in Fourier domain optical coherence tomography

“…27 with common-path images in Ref. 17. In this comparison we limited ourselves to true common-path OCT systems, which do not include a miniinterferometer at the tip of the fiber.…”

“…1(a). 17 A superluminescent diode (SLED371-HP1, Superlum Diodes, Russia) illuminates the tissue via a 3-dB fiber coupler (FC850-40-50-APC, Thorlabs, NJ, USA) and microscope objective with a working distance of 25 mm and lateral resolution of 17 μm (LSM03-BB, Thorlabs, NJ, USA). The reference arm shares the physical path of the sample arm, and is generated by the diffuse surface on the top of the tissue.…”

“…16 Recently, multiple reflections within the sample arm were also used to implement a common-path OCT imaging system. 17,18 In this article we present a simple and, to the best of our knowledge, novel way of acquiring common-path OCT images by using the tissue surface as the reflective surface of the reference arm. This removes the need for a separate reference reflective surface, such as glass plate.…”

Electrophysiological and Anatomical Correlates of Spinal Cord Optical Coherence Tomography

“…The OCT images were recorded using a custom spectrometer-based Fourier-domain. The system is described in detail elsewhere [ 30 , 31 ]. In brief, a single mode fiber coupled superluminescent diode with 850 nm central wavelength and 50 nm spectral bandwidth at half-maximum (SLED371-HP1, Superlum Diodes, Ireland) illuminates the tissue via a 3dB fiber coupler (FC850-40-50-APC, Thorlabs, NJ, USA), with a power on the sample on the order of 0.5 mW.…”