title: A 3-sided Pyramid Wavefront Sensor Controlled by a Neural Network for Adaptive Optics to reach diffraction-limited Imaging of the Retina
creator: Alvarez Diez, Cristina
subject: 530
subject: 530 Physics
description: In-vivo imaging of the eye's fundus is the basis for  the diagnosis of retinal diseases in ophthalmology.  However, the resolution of the images is limited -  besides the inevitable diffractive limitation by the  finite size of the pupil - by the imperfect optical  elements of the eye, causing aberrations. In astronomy,  first test measurements of atmospheric aberrations with  the novel 4-sided pyramid sensor have confirmed the  benefits of this sensor compared with conventional  wavefront sensors. This work presents a pyramid  wavefront sensor for the measurement of aberrations and  their compensation on a confocal laser scanning  ophthalmoscope. By contrast, a 3-sided pyramid prism is  used and it is demonstrated experimentally, that this  prism, which is easier to manufacture than the 4-sided  prism, reveals to be an equivalent sensor.  The control of the deformable mirror which can  compensate the aberrations is implemented by an  artificial neural network based on the acquired sensor  data. With the trained neural network, aberrations of  150nm RMS could already be reduced to half the error.  The neural network is composed of a convolutional  S_C-net of 2x4 layers, which extracts feature  information out of the signal images of the pyramid,  and a 3-layer, feed-forward backpropagation net, that  determines the required deflection of the mirror in  order to compensate for a given aberration.
date: 2006
type: Dissertation
type: info:eu-repo/semantics/doctoralThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserverhttps://archiv.ub.uni-heidelberg.de/volltextserver/6944/1/Diss_CAlvarezDiez.pdf
identifier: DOI:10.11588/heidok.00006944
identifier: urn:nbn:de:bsz:16-opus-69449
identifier:   Alvarez Diez, Cristina  (2006) A 3-sided Pyramid Wavefront Sensor Controlled by a Neural Network for Adaptive Optics to reach diffraction-limited Imaging of the Retina.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/6944/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: eng