To identify wave lengths smaller than the light waves Near-field imaging and Confocal microscopy methods are used. All confocal microscopes use an aperture to exclude light that originates above or below the object plane, giving them excellent depth resolution, however, the aperture also excludes information from all points in the object plane except the imaged point, thus requiring a scanning approach to image acquisition. Confocal microscopy involves moving the focal plane of a microscope vertically through the sample while acquiring a series of images. Advanced confocal microscopy simultaneously acquires data from multiple apertures in a spinning disk to dramatically reduce image acquisition time. ACM can produce a detailed model with sub-micrometer resolution in all three dimensions in a few seconds. To create the 3D image, the microscope collects 2D images or 'slices' of an object, and then uses computers and software to recreate a 3D image from hundreds of individual slices similar to a computed tomography system. It is possible to make a non-contact measurement of 3D microstructures and hence make the determination of surface roughness. For biological samples, speed is often an important concern as the lasers used for image scanning can photo bleach or damage the sample under prolonged exposure. See http://www.nano.org.tr/confocal_microscope.html for an excellent gallery of images.