| 摘要 |
PURPOSE:To take a measurement accurately and stably for a long period while eliminating the influence of the thicknesses of a liquid film and a liquid layer upon measurement accuracy by placing a liquid developer and a measurement system in a non-contacting state, and photodetecting scattered light due to toner particles in the developer and measuring the concentration. CONSTITUTION:A laser light source 35 arranged above a developer container 30 emits laser light to a liquid surface 34 at a constant angle and the laser light incident on the developer 31 is diffracted by toner particles 36 in the developer; and the scattered light due to the diffraction returns to the liquid surface and is converged by a lens 37. This converged light forms a diffraction graphic form on the focal plane of the lens 37 and a solid-state image pickup element 38 which moves as shown by an arrow is installed along the focal plane. The diffraction graphic form is scanned in the X-axial direction in the figure by the element 38 and converted into an electric signal, which is inputted to a concentration decision device 39 to detect the concentration. Consequently, the concentration is measured accurately and stably for a long period. |
