| 摘要 |
Apparatus and method to detect and measure, in a non-image area on a toner-image-bearing member, a low coverage of toner particles relating to a background coverage of toner particles in an image frame, and in particular, to detect and measure by an optical detector a low toner coverage in excess of a threshold coverage or a pre-selected coverage and thereby produce a signal, e.g., a process control signal. Such a process control signal can be used to adjust the operating parameters of a process in a subsystem, such as a toning process or a photoexposure process. In preferred embodiments, synchronous detection is used to extract a signal having a magnitude proportional to the low toner coverage representative of the background coverage of toner particles.
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