Light Diffraction Pattern

This is the light diffraction pattern at the back focal plane of a 10X, NA 0.25, microscope objective when viewing a diffraction of grating of 1.9 micrometers with darkfield illumination. The diffraction maxima of all of the visable wavelengths can be seen at the back focal plane. All though the resolution limit of this objective is 1.9 micrometers for blue light the 1.9 diffraction grating can be resolved with all wavelengths when darkfield illumination is used.