Hello group. I'm using a Zeiss microscope to examine a thin film of auto-fluorescent polyurethane cast onto a glass coverslip. The objective is a Nikon 1.30 glycerol immersion. Images obtained in reflected mode seem reasonable but transmitted images are sharp only in the periphery. In the center of the field there seems to be a circular haze extending 1/3 of the way out to the edge. This occurs at every setting of the condenser, and I can see the haze through the binocular. Any ideas? Rik G.