Sony UP-D2600S Service Manual page 112

[Each Block]
γ Correction Circuit
The print data from the IF-787 or IF-788 board is γ -corrected by the data conversion table of γ ROM
(IC206).
The address of γ ROM is allotted as follows, two bits are allotted for switching of each YMC color,
four bits for temperature correction of the thermal head, and four bits for kinds and feeding of the
ribbon. γ data is switched according to the switching signal from CPU (IC112).
PQC IC
Edge emphasis processing
To improve definition of the image, edge emphasis is performed by using a digital filter in the
horizontal and vertical directions.
Heat accumulation correction processing
The slow rising and dull operation due to bad head temperature response are corrected using a digital
filter.
Head Driving IC
PWM modulation processing
Eight-bit parallel data is PWM-modulated and converted into serial print data.
Separation print processing
If the print dot area of low density image portion becomes small, clearance
between print lines appears. Therefore, one step gradation is divided by four for printing.
Line Number Correction IC
If the exothermic resistor element connected to the thermal head increases, the composite resistance
of the element decreases. Voltage drop by common resistor of a harness cannot be thus ignored. The
print density becomes low. Therefore, the time turning on electricity to the head element is
controlled, and print density is corrected.
Head Voltage Correction
The head voltage can be increased or decreased by changing a VCONT signal. The following
corrections are performed by using the A/D port output of CPU (IC112). The V CONT signal is
controlled digitally by software.
Correction using thermal head temperature.
When printing with the same head voltage, there is a difference between print density due to the
degree of head temperature. Therefore, the head voltage is increased or decreased by the head
temperature just before printing.
4-18
UP-D2600/V1(E)