Fig. 1.

Zemax design showing the illumination arm of the confocal system (Media 1 ^{(458.6KB, AVI)} ) including the ETL positioned adjacent to the scanning mirrors (SM). With negative ETL focal lengths, the imaging planes lie further from the lens or deeper in the sample (a), and with positive ETL focal lengths, the imaging planes lie closer to the lens and sample surface (b). The insets show the change in the numerical aperture and focal position at the sample space as ETL changes focal length from (a) f = −127 mm to (b) f = + 44.3 mm. L1: Simplified objective lens, L2/L3: beam expander.