Closed loop control of reproduction machine

In a reproduction machine having a photosensitive member, a corotron device for charging the photosensitive member, an illumination and projection system for projecting images disposed on a platen along an optical path onto the photosensitive member, a developer for applying toner particles to the photosensitive member, and a toner dispenser for supplying toner to the developer, the combination of

• a first test target disposed near the photosensitive member, the test target movable into and out of the optical projection path, the first test target having an opaque target portion and a 0.4 solid area density portion,
• a second test target fixedly located at the edge of the platen, the second test target having a white target portion and a 0.3 solid area density portion, the first test target overlapping along the optical path the second test target upon movement of the first test target into the optical path,
• an electrometer disposed near the photosensitive member, the electrometer generating signals in response to imaging of the opaque portion of the first test target to control the corotron device, the electrometer producing signals in response to the imaging of the white portion of the second test target to initiate control of the illumination system,
• an infrared densitometer located near the photosensitive member, the infrared densitometer being responsive to the 0.3 solid area density target of the second test target to initiate control of the developer bias, and
• the densitometer being responsive to the overlapping 0.4 and 0.3 solid area density portions to initiate control of a toner dispenser.

Apparatus for controlling the operation of a reproduction machine having an optical path comprising:

• a controller,
• a first test medium,
• a driver, the driver moving the first test medium into and out of the optical path,
• the photosensitive surface manifesting the presence of the first test medium in the optical path and
• a sensor responsive to the characteristics of the photosensitive surface for producing signals, the controller responsive to the signals for controlling machine operation.

Apparatus for controlling the operation of a reproduction machine having an optical path for projecting an image of an object on a platen onto a photosensitive surface, comprising:

• a controller,
• a plurality of test mediums,
• means to dispose the test mediums in overlapping relationship in the optical path, the characteristics on a portion of the photosensitive surface manifesting the presence of the overlapping test mediums in the optical path, and
• a sensor responsive to the portion of the photosensitive surface manifesting the overlapping test mediums for producing signals,
• the controller responsive to the signals for changing the operation of the machine.