Optical magnetometry makes use of various optical techniques to measure magnetization. One such technique, Kerr magnetometry makes use of the magneto-optic Kerr effect, or MOKE. In this technique, incident light is directed at the samples surface. Light interacts with a magnetized surface nonlinearly so the reflected light has an elliptical polarization, which is then measured by a detector. Another method of optical magnetometry is Faraday rotation magnetometry. Faraday rotation magnetometry utilizes nonlinear magneto-optical rotation to measure a samples magnetization. In this method a Faraday modulating thin film is applied to the sample to be measured and a series of images are taken with a camera that senses the polarization of the reflected light. To reduce noise, multiple pictures are then averaged together. One advantage to this method is that it allows mapping of the magnetic characteristics over the surface of a sample. This can be especially useful when studying such things as the Meissner effect on superconductors. Microfabricated optically pumped magnetometers (µOPMs) can be used to detect the origin of brain seizures more precisely and generate less heat than currently available superconducting quantum interference devices, better known as SQUIDs. The device works by using polarized light to control the spin of rubidium atoms which can be used to measure and monitor the magnetic field.