Confocal microscope slit aperture

If the sample is transparent and very thin, less than hi, then the combination of lenses LI and L2 and the intermediate slit in Fig. 2 are redundant. The stigmatic quality of the microscope ensures that a diffraction-limited image will be focused on the CCD. In this case, the Raman microscope is intrinsically confocal without the need for a slit or other aperture. 

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