An apparatus (100) for measuring toner concentration in a developer contained in a developer housing (10) includes a developer sample container (102) that receives a portion of developer extracted from the developer housing (10). A spectrophotometer (112) measures spectrophotometric data for the portion...http://www.google.com.tw/patents/US6774999?utm_source=gb-gplus-share專利 US6774999 - Apparatus and method for characterizing the toner concentration in a developer of a printing device
