| 摘要 |
<p>A light emitting device (57) and light receiving device (58) are positioned to face each other to sandwich the developer cartridge (18). A pair of light transmitting tubes (56L, 56R) is installed in the casing (19) of a developer cartridge (18). Light emitted from the light emitting device (57) travels inside the casing (19) via the light transmitting tubes (56L, 56R) and is received by the light receiving device (58). The direction of light traveling through light transmitting tubes (56L, 56R) changes along the light path to the light receiving device (58). When a developer cartridge (18) is attached to the housing, toner blocks light from traveling through the toner chamber (23) to the light receiving device (58). When the toner is consumed and the developer cartridge (18) is ready to be replaced, light passes through the toner chamber (23) and is received by the light receiving device (58), prompting exchange of the developer cartridge (18).</p> |
