During the last decade, various efforts have been undertaken to enhance the resolution of optical microscopes, mostly because of their importance in biological sciences. Herein, we describe a method to increase the resolution of fluorescence microscopy by illuminating the specimen with a mesh-like interference pattern of a laser source and electronic postprocessing of the images. We achieve 100-nm optical resolution, an improvement by a factor of more than 2 compared with standard fluorescence microscopy and of 1.5 compared with confocal scanning.

A method for increasing lateral as well as axial resolution in fluorescence microscopy is presented. A passband with a high cutoff frequency throughout reciprocal space can be achieved by illumination of the object with spatially harmonic excitation patterns generated by the interference of two collimated laser beams. Theoretical calculations show an almost isotropic point-spread function with a FWHM near 100 nm.

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An ongoing concern of conservators when restoring paintings and polychrome objects is the possibility of irreversible damage to the original paint layers. This is the case when removal and replacement of aged varnishes is being considered. Although much work has been conducted to determine the effect of the removal of a varnish on the condition of the (painted) surface, there is still some uncertainty in the conclusions because it has, until recently, been impossible to characterize the original surface under the varnish in situ. A promising solution to this problem is the use of white light confocal profilometry. An initial study has been conducted using this technique to measure the roughness of pencil lines and oil paint under a varnish. Measurements were made on areas up to several mm 2 in size, at lateral resolutions down to 1 µm, and vertical (roughness) resolutions of 0.1-0.3 µm. It was found that the surface roughness of surfaces under relatively thick varnishes can be measured at relatively low magnification (20x). For thin varnish layers typical of paintings, higher magnifications are required. White light confocal profilometry has thus been shown to be a useful tool for in situ studies of the (sub)surface properties of (painted) objects.

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