| 摘要 |
PURPOSE:To enable accurate detection of toner concentration according to reflection intensity of a specified wavelength light from a developer by utilizing the fact that the carrier in the developer exhibits always constant reflectivity in the specified wavelength light. CONSTITUTION:A light from light emitting station 3b irradiates developer d through transparent plate 3a in toner concentration detector 3 arranged in the bottom of developer tank 21, and this reflected light is received by light receiving station 3c. The spectral curves of the reflected light from the carrier of developer before use and that from the carrier approach each other or intersect each other, and the light having the wavelengths of these intersection point A or B or near A or B is used and the reflected light of this light from the developer is received to detect toner concentration. As a result, the toner concentration is accurately measured without being affected by deterioration of the developer by selecting such wavelengths. |
