Simple interferometric microscopy for in situ real-time two-dimensional observation of crystal growth

We have developed a simple interferometric microscope suitable for in situ observation of crystal growth. The device consists of a light emitting diode (LED) light source, a slightly modified microscope, and a charge coupled device (CCD) camera, all of which are inexpensive and commercially available. In addition to information on a standard 2D image from a CCD camera, this system displays interference fringes that enable one to map the temporal evolution of the distribution of thickness in real time, practically allowing 3D observation of growing crystals. LED light of a relatively low coherence can preferentially project a depth distribution of thin growing crystals as a fringe pattern, effectively suppressing parasitic interference induced by stray beams reflected off optical components. This device is as easy to use as a conventional microscope and can be routinely applied to observe a growth of zeolite crystals in a pressurized hot solution cell. (C) 1996 American Institute of Physics.