travis.sadecki@LIGO.ORG - posted 16:21, Wednesday 07 January 2015 - last comment - 08:17, Thursday 08 January 2015(15928)
Green light photo-subtraction image of ETMy cleaning
WIth Rick's help, we have created a composite image of ETMy before, after, and before-minus-after using Matlab. Due to saturation of the camera's photodetector in the 'after' photo (we believe due to higher power in the arm), the particles we removed during cleaning appear magenta. Tomorrow, I hope to do the same with the IR photos.
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I think Travis meant to say "before photo" rather than "after photo." We suspect that the purple color comes from the fact that in the "before" photo the large scatterers were saturating the image at this exposure, as indicated by the bright white fields in the image. In the "after" photo, we subtract a fair amount of the green light due to the diffuse background scatter which is perhaps brighter due to the higher circulating power resulting from the reduction in losses. Removing most of the green leaves the red and blue for the saturated scatterers, rendering them purple.
Rick is correct, 'after' should be 'before'. I also meant that the appearance of more green light scattering in the 'after' photo is likely due to more arm buildup. Apologies for any confusion induced.