| 摘要 |
A xerographic copier is arranged to produce, on the imaging element (26) a developed test area (30) corresponding to an original of uniform colour and density bordered by an unimaged area (28). The reflectivity of both areas are sensed to provide control signals to alter either developer bias or illumination intensity. The alteration is carried out such as to maintain a vector, comprising the image voltage on the imaging element corresponding to the latent image of the test area minus the developer bias voltage, contant. The test area is produced in a cycle either at the end of a multiple copy run or in a cycle interrupting a lengthy multiple copy run. |
