| 摘要 |
PURPOSE:To receive transmit light without reducing the quantity of light even if a pair of reciprocated fibers are not parallel with each other by setting up the cross section of the reciprocated fibers and a light receiving fiber to a value larger than that of a light transmitting fiber at the time of detecting a toner state in each developing unit of a developing device by the reciprocated fibers. CONSTITUTION:In order to detect toner density and toner residual in each developing container, a fixed detecting part embedding a fiber 12 connected to a light source 10 rectangularly to the side of the container and a fiber 13 connected to a light receiving element 11 is formed. These fibers 12, 13 are fixed by a light coupling part 8 and a pair of reciprocated fibers 14, 15 connected to the coupling part 8 are penetrated into a detecting part 7 and cut off so that light from the fiber 14 is radiated to the container and the reflected light is received by the fiber 15 to detect the toner state by the element 11. In said constitution, the cross sectional areas of the fibers 14, 15, 13 are set up to values larger than that of the fiber 12, so that even if a movable detecting part is slightly shifted, light can be surely detected.
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