Scanning laser ophthalmoscopy is a confocal imaging technique that allows high-contrast imaging of retinal structures. Rapid, involuntary eye movements during image acquisition are known to cause artefacts and high-speed imaging of the retina is crucial to avoid them. To reach higher imaging speeds we propose to illuminate the retina with multiple parallel lines simultaneously within the whole field of view (FOV) instead of a single focused line that is raster-scanned. These multiple line patterns were generated with a digital micro-mirror device (DMD) and by shifting the line pattern, the whole FOV is scanned. The back-scattered light from the retinal layers is collected via a beam-splitter and imaged onto an area camera. After every pattern from the sequence is projected, the final image is generated by combining these back-reflected illumination patterns. Image processing is used to remove the background and out-of-focus light. Acquired pattern images are stacked, pixels sorted according to intensity and finally bottom layer of the stack is subtracted from the top layer to produce confocal image. The obtained confocal images are rich in structure, showing the small blood vessels around the macular avascular zone and the bow tie of Henle's fiber layer in the fovea. In the optic nerve head images the large arteries/veins, optic cup rim and cup itself are visualized. Images have good contrast and lateral resolution with a 10°×10° FOV. The initial results are promising for the development of high-speed retinal imaging using spatial light modulators such as the DMD.
A method is proposed for determining blood oxygen saturation in frozen tissue. The method is based on a spectral
camera system equipped with an Acoustic-Optical-Tuneable-Filter. The HSI-setup is validated by measuring series of
unfrozen and frozen samples of a hemoglobin-solution, a hemoglobin-intralipid mixture and whole blood with varying
oxygen saturation. The theoretically predicted linear relation between oxygen saturation and absorbance was observed in
both the frozen sample series and the unfrozen series. In a final proof of principal, frozen myocardial tissue was
measured. Higher saturation values were recorded for ventricle and atria tissue compared to the septum and connective
tissue. These results are not validated by measurements with another method. The formation of methemoglobin during
freezing and the presence of myoglobin in the tissue turned out to be possible sources of error.