Global illumination

Dopaminergic amacrine cells with widespread dendritic arborizations increase release of dopamine in response to increases in global illumination. Dopamine diffuses throughout the retina to influence cells as far away as the RPE. The increased release of dopamine by light modifies cell function to opdmize retinal responses in daylight (Witkovsky, 2004). 

Raman microspectroscopy was not a completely new concept. In 1966, Delhaye and Migeon [35] showed that a laser beam could be hghtly focused at a sample, and that Raman-scattered light could be collected and transferred to a spectrometer, with minimal loss. Their calculahons showed that the increased irradiance more than compensated for the decrease in the size of the irradiated volume. The first Raman microscope was reported by Delhaye and Dhamelincourt in 1975 [36], and an instrument based on these principles (the MOLE) was introduced by Jobin Yvon at about the same time. However, the optical scheme used for imaging, which employed global illumination, was inefHcient and it was not until the advent of CCD-Raman spectrometers that the advantages of Raman microscopy became apparent. 

Two alternative methods of Raman imaging via global illumination and via point illumination in combination with confocal light collection were applied to the study of heterogeneous polymer systems. The spectral and spatial resolving power of the different techniques was estimated experimentally. The influence of the depth resolution on the Raman image of a defined sample structure was demonstrated in a mathematical simulation. Data are given for PE, PS, polyacrylate, and epoxy resins. 23 refs. 

In this case, the samples studied were polymeric they were transparent and exhibited significant amounts of fluorescence. The authors found that as a consequence of the absence of depth resolution, the global illumination technique appeared more vulnerable to artifacts arising from scattering effects due to the sample geometry and fluorescence. ... 

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