A reflective movable diaphragm unit 2 having diaphragm portions 25 formed by a circular SiO2 film, a mesa portion 22 and light-reflecting mirror portion 23 of the SiO2 film disposed in the center, and a ring-shaped spacer 24a and bonding layer 24b formed of metal layers in the circumferential edge portion...http://www.google.com.hk/patents/US6820487?utm_source=gb-gplus-share專利 US6820487 - Reflective moveable diaphragm unit and pressure sensor containing same
