Question

Is it possible to scan a slide upsode-down (with the coverslip toward the illuminator)?

Answer

Yes. This is possible with 20x and lower-powered objectives. Since the specimen is underneath the slide, which is 1mm thick, an objective with a working distance larger than 1mm should be able to scan the slide.

High-powered objectives require a working distance that much closer than 1mm and, therefore, cannot scan a slide that is upside-down.