Minolta Di 620 Manual page 69

1. PH-I/F: PWB-J
Blocks out external noise during transfer of image density data from the memory
section (PWB-B) to the PH section.
2. Bit Expansion: PWB-J
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 "character mode", the block outputs
binary image density data values without change.)
3. Straight-Line Screen Processing: PWB-J
This section operates only if image quality is set to "photo." The section enhances
visible copy quality by improving the grain of the copy's middle tones, stabilizing
the density reproduction of low-density areas, and reducing pitch disparities in the
subscan direction. These improvements are obtained by combining pixels into
groups of 2, and printing the two pixels such that one of the pixels gets most of
the density. Vertical lines appear along the pixel lines that take the reduced den-
sity.
4. γ Correction: PWB-J
Adjusts data so that the copied image's gradation characteristics will be propor-
tional to the gradation characteristics of the original. Adjustment is made by
selecting the appropriate gamma look-up table, then using the table data to con-
vert image density values into appropriate laser intensity values.
5. PH Line Memory: PWB-J
Corrects for differences in data transfer frequency with respect to PH line mem-
ory.
6. Erasure of Outside Area: PWB-J
Erases the area outside of the image area, so as to prevent firing of the laser over
non-image areas.
7. D/A Conversion: PWB-L
Converts the 8-bit laser intensity data values into analog laser intensity voltages.
8. LIMOS Circuitry: PWB-L
Compares the received laser intensity voltage with the detected LD (laser diode)
emission voltage, and uses the difference between these values as the bases for
controlling LD current and emission level.
9. Laser Emission: PWB-L
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.
M-50