A tristimulus colorimeter including a modified dual slope integrator digital voltmeter measures the red, blue and green light reflected from a sample and displays the same in digital form as optical density units. The colorimeter includes a light conducting probe with a diffusing member and a movable...http://www.google.de/patents/US3986777?utm_source=gb-gplus-sharePatent US3986777 - Tristimulus colorimeter for use in the fabrication of artificial teeth
