The two most important parameters in objective design are the numerical aperture (which determines the fine detail in the image) and the magnification, which decreases the area that is imaged. For more than 100 years the magnification of objective lenses was kept between 40 and 70 times the numerical aperture. It was thought pointless to make this number lower, since, even though a larger field could in principle be seen the detail in the image would then be too fine to be seen by the human eye.
The Mesolens has a magnification-to-N.A. ratio of 8, achieved by a total redesign, in which great precision is required to achieve the correction of chromatic and other aberrations. This was made much more difficult by the need to use large optical elements (its magnification is x4 and NA 0.5 and working distance nearly 3 mm, multi-immersion): aberrations scale with the diameter of the lens.
Although modern cameras can record more detail than the human eye, the main reason for going through this marathon of design and construction was to make the Mesolens able to discriminate depth. This allows it to be used for 3-dimensional imaging (e.g. confocal and multi-photon optical sectioning) for which existing low-magnification objectives are almost useless. The Strathclyde Mesolens was developed for imaging mouse embryos 5mm long in their entirety by confocal scanning microscopy, yielding 3D datasets in which all of the millions of cells present are shown with sub-cellular resolution (<1 micron).
Click below to read more about the Strathclyde 'Mesolab' facility