hp Color 9850mfp SCANNER 1.2.2 Shading correction reading The exposure unit starts the shading correction with the white standard board attached to the scanner glass once it completes the home position search. In the shading correction operation, the white correction is performed twice and the black correction once. In the white correction, the white standard board is read while the exposure lamp (L1) is turned on. In the black correction, the board is read while the lamp is off. Data for each CCD sensor is read during the both white corrections and each pixel is compared its bright- ness. The brighter data is regarded as the white correction data.
The shading correction reading operation may differ between when the main switch (SW2) is turned on II UNIT EXPLANATION and when the start button is pressed. A. When the main switch (SW2) is turned on [2] [1] [3] [4] [5] [6] [7] [1] [5] 2nd white correction Scanner APS location (home position) [2] PS1 [6] Black correction [3] [7] [4] 1st white correction Scanner APS position Returning the amount moved B. When the start button is pressed The basic operation is identical to when the main switch (SW2) is turned on; however, it starts the copying operation without stopping at the scanner glass APS location (home position) after reading the shading correction. 2-3