Use this URL to cite or link to this record in EThOS:
Title: Microscopic imaging and photo-stimulation using micro-structured light emitting diodes
Author: Poher, Vincent Yves Jean
ISNI:       0000 0004 2737 5603
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2008
Availability of Full Text:
Access from EThOS:
Access from Institution:
Recent developments in light emitting diode (LED) technology such as increasing improvements in brightness, UV operation and micro-structured array devices make LEDs very attractive illumination sources for a wide range of applications. This thesis describes the development and application of micro-structured LED technology as a patterned light source for confocal microscopy and photo-stimulation of neuron cells. Using lithographic techniques, light emitting diodes can be readily patterned into arrays of individual elements of order 20 microns in size. Several such programmable arrays are presented and tested, along with the ancillary drive electronics that were developed to allow the display of arbitrary light patterns on a timescale of tens of microseconds. A one-dimensional 120-element array of line emitters, is applied to obtain optically sectioned images in a fluorescence microscope with no moving parts. Several optical sectioning techniques are demonstrated, including grid-projection structured illumination microscopy and line scanning confocal microscopy. This latter technique is extended to multi-line illumination, and the concern about removing the remaining out-of-focus background leads to a new background subtraction technique that dramatically improves the sectioning strength and image contrast. The theory of optical sectioning by out-of-focus background subtraction under line-patterned illumination is developed, and it is shown that the performance converges towards that of the grid-projection structured illumination method for high fill-factor illumination patterns. This theory is used to propose the design of a double-sided spinning disk microscope that should enable confocal imaging at very high-frame rate with superior optical sectioning. A second application makes use of matrix addressable LED arrays for direct stimulation of neuron cells. Gallium-Nitride LED arrays are demonstrated to be realistic light sources for photo-stimulation that have clear advantages in terms of emission wavelengths, temporal response and spatial resolution. Micro-LED arrays enable very reliable photo-stimulation with sub-cellular resolution at a single cell level and selective neuron excitation at a network level. A long-term project to implement an LED based retinal prosthesis is presented.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available