Objective lenses coverslip thickness

Figure 7 shows two designs of coverslip-form solid-immersion micropshere superlens we have proposed, a flat-top design (Fig. 7a), and a hemisphere-top design (Fig. 7b), both having a thickness similar to standard coverslip which is small enough for the superlens to be directly inserted into the gap between conventional microscope s objective lens and sample. The hemisphere-top curved surface in the design Fig. 7(b) is used to reduce the effect of total internal reflection from a flat surface. 

This is the least expensive optical component, but very important and the most likely to be carelessly chosen. Many objectives are designed and marked to be used with coverslips of a certain thickness, usually 0.17 mm (or 170 5 pm), which corresponds to a thickness grade of 1.5. Ideally, for obtaining the best FISH images, it is recommended that an oil immersion lens is used and these lenses almost always require a 1.5 coverslip for optimal resolution. Any deviation from this thickness leads to spherical aberration, loss in resolution and results in larger and dimmer FISH spots. 

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