| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for detecting concentration of a liquid developer by excluding errors in the method for detecting concentration due to a change in the quantity of light of an emission light source and the contamination of a light path for detection. SOLUTION: In a method for detecting the concentration of a toner where a light-emitting device 9 and a light reception sensor 10 are installed while sandwiching a developer delivery channel 6 in that a developer flows and the intensity of light with the light-emitting device 9 as a light source is detected by the light reception sensor 10, the distance of the above channel being sandwiched by the light-emitting device 9 and the light reception sensor 10 is changed continuously or discontinuously, thus changing a light path length, namely the length where the above light is transmitted through the above developer, detecting the transmission light intensity, and performing the operation processing of the detected transmission light intensity as a function of the above light path length for obtaining the fluctuation of the above developer.
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