A miniature readhead is provided for photometric color detection using ambient light. The readhead is hand-held, including a superposed plate and tray. The tray receives sample media configured to react and to change color according to an amount of analyte in a sample. The plate is optically transmissive,...http://www.google.de/patents/US7768645?utm_source=gb-gplus-sharePatent US7768645 - Miniature optical readhead and colorimeter for analysis media
