A substantially solid transparent body focuses light from an LED wholly immersed therein to a point external to the body. The body is composed of a substantially non-heat-conducting plastic material and has a surface with the curvature of a Cartesian Ovoid substantially in accordance with the formula...http://www.google.com.tw/patents/US4869580?utm_source=gb-gplus-share專利 US4869580 - Immersion cartesian ovoid lens
