Master Slave Optical Coherence Tomography Research Articles

Downconversion master slave optical coherence tomography for simultaneous en-face imaging at two depths.

We report the production of two en-face optical coherence tomography (OCT) images from two different depths in real time, using three interferometers in a configuration of double downconversion master slave OCT. Two active mixers are used to produce the analog product of two photodetection signals. A low-cost digitizer with a sampling rate just at the level of twice the inverse of the tuning interval is used, with a much lower sampling rate than that required by the conventional A-scan-based OCT imaging at the same tuning rate. Not employing a fast digitizer for the photodetected signal, as conventional OCT imaging does, the selection of temporal windows from the photodetected signals is achieved by low-cost RF switches. Optimum conditions for the active mixers and switches employed are evaluated to optimize the downconversion operation.

Master slave en-face OCT/SLO.

Master Slave optical coherence tomography (MS-OCT) is an OCT method that does not require resampling of data and can be used to deliver en-face images from several depths simultaneously. As the MS-OCT method requires important computational resources, the number of multiple depth en-face images that can be produced in real-time is limited. Here, we demonstrate progress in taking advantage of the parallel processing feature of the MS-OCT technology. Harnessing the capabilities of graphics processing units (GPU)s, information from 384 depth positions is acquired in one raster with real time display of up to 40 en-face OCT images. These exhibit comparable resolution and sensitivity to the images produced using the conventional Fourier domain based method. The GPU facilitates versatile real time selection of parameters, such as the depth positions of the 40 images out of the set of 384 depth locations, as well as their axial resolution. In each updated displayed frame, in parallel with the 40 en-face OCT images, a scanning laser ophthalmoscopy (SLO) lookalike image is presented together with two B-scan OCT images oriented along rectangular directions. The thickness of the SLO lookalike image is dynamically determined by the choice of number of en-face OCT images displayed in the frame and the choice of differential axial distance between them.

On the possibility of producing true real-time retinal cross-sectional images using a graphics processing unit enhanced master-slave optical coherence tomography system

In a previous report, we demonstrated master-slave optical coherence tomography (MS-OCT), an OCT method that does not need resampling of data and can be used to deliver en face images from several depths simultaneously. In a separate report, we have also demonstrated MS-OCT's capability of producing cross-sectional images of a quality similar to those provided by the traditional Fourier domain (FD) OCT technique, but at a much slower rate. Here, we demonstrate that by taking advantage of the parallel processing capabilities offered by the MS-OCT method, cross-sectional OCT images of the human retina can be produced in real time. We analyze the conditions that ensure a true real-time B-scan imaging operation and demonstrate in vivo real-time images from human fovea and the optic nerve, with resolution and sensitivity comparable to those produced using the traditional FD-based method, however, without the need of data resampling.