A method for outputting a closest match of a plurality of electronically stored shade guide values of a dental shade guide system is disclosed. A protective tip including a hole for couples light from a probe to a measurement spot on a dental object. The probe is in proximity to a reference standard...http://www.google.com.tw/patents/US7785103?utm_source=gb-gplus-share專利 US7785103 - Apparatus and method for measuring optical characteristics of teeth
