The principle of electron holography can also be applied to interference lithography. These include interferometric distance measurement, holography, coherent communications, and coherent control of chemical reactions. Holography requires temporally and spatially coherent light. The first reports of using digital holography for light microscopy came in the mid 1990s. Electron holography is the application of holography techniques to electron waves rather than light waves. This patch holography is called holonomy or windowed Fourier transformations. Coherence length is important in holography and telecommunications engineering. It is also used for image retrieval from undersampled measurements in optical and millimeter-wave holography. Fourier processes are the basis of holography. Holography technique can also be effectively used for radiation dosimetry. Neutron beam holography has been used to see the inside of solid objects. Dichromated gelatine is still used for some laser holography. This scheme is also called "point projection holography". Since the beginning of holography, amateur experimenters have explored its uses. The latter developed in parallel with classical holography during the hibernation of digital holography.