Minolta CF910 Service Manual page 32

2. AIDC Detection
• Three density patterns selected through the AIDC Sensor UN20 fine adjustment are pro-
duced on the surface of the PC Drum for each color (in the order of Y, M, C, and Bk) to
allow UN20 to detect the amount of toner attracted to the drum surface.
• The amount readings are used in "5. Operations" that follows.
• The detection is made when the Power Switch is turned ON, a misfeed or malfunction is
reset, and at the end of the copy cycle.
• It occurs while the PC Drum turns one complete turn.
3. PC Drum Surface Potential Detection (Vi Detection)
• The PC Drum surface potential is detected by Surface Potential Detection Sensor UN22.
• Ten latent image patterns with varying gradation levels are produced on the surface of
the PC Drum and UN22 detects the surface potential of each pattern.
• The surface potential readings are used in "5. Operations" that follows.
When Power Switch S1 is turned ON:
• The intensity of LD1 light and grid voltage (VG) are varied in three steps and, for each of
these three steps, ten latent image patterns of varying gradation levels are produced for
surface potential detection. (The PC Drum turns three turns.)
Other than above
• Ten latent image patterns with different gradation levels are produced with LD1 and VG
remaining the same, for each of which the surface potential is detected.
• Surface potentials of a total of ten patterns are detected.
4. Max. LD1 Intensity Correction
• To prevent the copy image density from being changed by changes in the PC Drum sen-
sitivity during a multi-copy cycle, the maximum intensity of LD1 light (PMAX) is corrected
at a timing between copies.
PMAX Correction Operation
A. The VG value of Black of the first copy is directly applied to the PC Drum without any
correction.
B. The surface of the PC Drum is illuminated with the PMAX of Black for the first copy.
C. Surface Potential Detection Sensor UN22 measures the surface potential of the PC
Drum.
D. Using the measurement result, the copier calculates an optimum PMAX to make the
necessary correction.
5. Operations
• Based on the copier conditions found through the AIDC detection and PC Drum surface
potential detection (Vi detection), the CPU computes the PC Drum charge, image trans-
fer, PC Drum sensitivity and developing characteristics, grid voltage (VG), developing
bias (VB), exposure curve and maximum intensity of LD1 light. By setting the parame-
ters, the CPU maintains the best possible image quality.
• The values set for "PRT Max Density," "PRT Hilight," and "Background Voltage" of
"Image Adjust" available from the Service Mode are incorporated during these opera-
tions.
M-15