An ultra-minute microscope for spectroscopy includes a rod-shaped lens having an index of refraction distribution gradient and capable of having a sample mounted on one end surface thereof, an element for projecting a laser beam into the rod-shaped lens from another end surface thereof and converging...http://www.google.com.hk/patents/US6108094?utm_source=gb-gplus-share專利 US6108094 - Ultra-minute microscope for spectroscopy
