DEVELOPER COMPOSITION

PROBLEM TO BE SOLVED: To solve the problem wherein toner concentration is measured with a toner concentration (TC) sensor which is expensive but not accurate and relys on a measurement technique which is indirect and inferior in noise signal ratio, is used. SOLUTION: A developer composition having improved noise signal ratio in an optical toner concentration sensing system, including a toner having a first diffuse reflectivity and a carrier having a second diffuse reflectivity wherein the difference between the first diffuse reflectivity and the second diffuse reflectivity is substantially high. For example, the difference between the 1st diffuse reflectivity of the toner and the 2nd diffuse reflectivity of the carrier is preferably 5% or more. Consequently, the nose signal ratio of a toner concentration signal generated from an electric signal can be made relatively large according to light reflected by a transparent visual field window and a developer. COPYRIGHT: (C)2003,JPO