Parallel scanning light ophthalmoscope (PSLO) for retinal imaging

K.V. Vienola, Mathi Damodaran, Boy Braaf, Johannes F. de Boer

Research output: Contribution to ConferencePosterOther research output


The eye is constantly in motion even when fixating on a target. These so-called fixational eye movements exist to maintain a sharp vision and they can easily extend to frequencies above 100 Hz. However, they are also the major source of artefacts in retinal imaging systems where the imaging is typically done 30 Hz. In order to reduce eye motion related artifacts in retinal image data we are developing a high-speed imaging system using digital light projection (DLP) technology.

To achieve high imaging speeds, retinal area is illuminated with multiple spots/lines in parallel within the whole field of view (FOV) instead of using a single focused spot/line like in traditional scanning laser ophthalmoscopes. These multiple lines/spots patterns are generated with a digital light projector (Lightcrafter 4500, Texas Instrument) and by slightly altering spot/line patterns that we are projecting to the retina, a scanning effect is created. The back-scattered light patterns from the retinal layers are collected via the beamsplitter (PBS) and imaged on to the camera. After every pattern is projected, the final frame is generated by combining these back-reflected illumination patterns. To compensate the lack of physical pinholes, out-of-focus light is removed in the post-processing.

The fovea of a healthy subject was imaged using 72 patterns. On the left all recorded line patterns were combined to form a non-confocal fundus image showing negligible visible structure. On the right the same lines undergo image processing to remove the out-of-focus light and the corneal scattering. This leads to improved contrast and better lateral resolution in the fundus image. The typical Henle’s fiber layer bowtie is observed around the fovea seen as two brighter areas. Image size is approximately 2.3 mm × 2.3 mm.

It is possible to create confocal images with the PSLO system. In theory the projector can achieve higher frame rates than traditional scanner-based systems (> 100 Hz) by illuminating the sample with multiple spots/lines. In retinal imaging, such a setup will provide better images because higher imaging speeds reduce motion artifacts.
Original languageEnglish
Number of pages1
Publication statusPublished - 25 Sept 2015
EventVU University Medical Center Amsterdam 9th Science Exchange Day - VU University Medical Center Amsterdam, Amsterdam, Netherlands
Duration: 25 Sept 201525 Sept 2015


ConferenceVU University Medical Center Amsterdam 9th Science Exchange Day
Abbreviated titleVUmc SED 2015


  • structured illumination
  • retinal imaging
  • digital micromirror device
  • ophthalmic imaging
  • retina


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