Incoherent Light Sources for Speckle Reduction in Double Pass Ocular Imaging

2018 edition

Donatus Halpaap

Using the double pass (DP) technique, the point spread function of a patient’s eye can be determined, including information about aberrations of higher orders as well as scattering, to obtain an overall estimation of the optical quality of a patient’s eye. It requires a sufficiently powerful, directional and point-like light source like e.g. a laser. However, if a laser is used, images suffer from speckle formation, which hinders their interpretation.

We compared light sources with different degrees of temporal coherence, namely a laser diode (LD), a light emitting diode (LED), and a superluminescent light emitting diode (SLED) in terms of speckle formation in DP images of a static eye model to evaluate their usefulness. For this, we compare the radially evaluated speckle contrast of DP images, with and without a vibrating mirror in the beam path, which is a conventionally used technique to remove speckle in DP images.