Minolta Di450 Service Manual page 52

1. Erasure of Outside Area: PWB-B
Erases the area outside of the image area, so as to prevent firing of the laser over
non-image areas.
2. Bit Expansion: PWB-B
If image quality is set to photo mode, this block expands binary data values into 8-bit
data values. (If image quality is set to the Text mode, the block outputs binary image
density data values without change.)
3. Image Density Smoothing: PWB-B
The edge data is filtered in the Text mode and data is converted, thereby reducing jag-
gies that would otherwise occur along the edges.
4. γ Correction: PWB-B
Adjusts data so that the copied image's gradation characteristics will be proportional
to the gradation characteristics of the original. Adjustment is made by selecting the
appropriate gamma look-up table, then using the table data to convert image density
values into appropriate laser intensity values.
5. Line Memory: PWB-B
Corrects for differences in data transfer frequency with respect to PH line memory.
6. Two-Beam Position Correction: PWB-B
The amount of positional deviations in the main and sub scanning directions of the
two laser beams is detected to make the necessary corrections.
• Main scanning direction: Correction is made by advancing or retarding the laser
• Sub scanning direction: Correction is made by turning the stepping motor of the PH.
7. D/A Conversion: PWB-B
Converts the 8-bit laser intensity data values into analog laser intensity voltages.
8. LIMOS Circuitry: PWB-JL, JR
Activates the APC (Auto Power Control) function that controls the current flowing
through the LD for each line; activates the ACC (Auto Current Control) function that
stabilizes the drive current for each dot.
9. Laser Emission: PWB-JL, JR
• Fires laser onto PC drum in accordance with the emission level given by the LIMOS
block.
• The copier employs 2 laser beams, and therefore prints two lines at a time.
emission start timing signal.
M-32