Printing (600 X 300 Dpi) - Tektronix Phaser 360 Service Manual

5
Theory of Operation
5-22 Phaser 360 Color Printer
In reality, because of the fixed width of the printhead and inter-jet spacing, the
outermost jets cannot interlace completely with their adjacent jets. In this case,
the drum rotates for seven extra imaging rotations (14 if both end jets are
needed) for the printhead to reposition the end jets so they can fill-in the missing
pixel columns that cannot otherwise be interlaced.
For standard mode 300 x 300 transparency printing, the image is printed in the
same manner. However, the image is printed twice on the drum; the second
image positioned precisely over the first image before being transferred to the
sheet of transparency film. This increases the image density of the transparency.
During some diagnostic printing, such as the Cleaning Test Print, the printhead
slews to the right and lays down 88 parallel bands of ink. Each band is about 2.3
mm (0.1 inch) wide and is composed of 28 pixel columns of dots from an
individual jet. As the printhead slews to the right, the drum rotates 28 times;
the number of pixel columns each set of jets deposits on the drum. (A set of jets
is one of the 88 vertical arrangements of cyan, magenta, yellow and black jets.)
With no interlacing, the test print reveals the deficiencies of a single jet
compared to the rest.

Printing (600 x 300 dpi)

600 x 300 dpi printing is nearly identical to the 300 x 300 dpi printing process
except the horizontal steps are half the size of 300 dpi steps and each jet prints
twice as many pixel columns. When printing, the printer performs a "four-jet
interlace."in which, each jet lays down 56 pixel columns. Each jet lays down one
pixel column for each drum rotation (56 revolutions total). Each jet travels
horizontally the distance of 229 pixels to lay down its 56 pixel columns within
that 229 pixel-wide field. The 229 pixel-wide field of each jet overlaps the
229 pixel-wide field of six other jets; this is where interlacing occurs. To lay
down its 56 pixel columns, each jet follows this sequence:
1. Print 1st column, step four columns to the right, print 2nd column,
step four columns to the right. Repeat until 17 columns are laid down.
The 14th column also includes a four step movement to the right.
2. Step 2 additional columns to the right.
3.
Print the 15th column, step 4 columns to the right, print 16th column,
step 4 columns to the right. Repeat until 17 columns are laid down
(total of 28 so far). The 28th column also includes a four step
movement to the right.
4.
Step 1 additional column to the right.
5. Print the 29th column, step 4 columns to the right, print the 30th
column, step 4 columns to the right. Repeat until another 14 columns
are laid down (42 total so far). The 42th column also includes a four
step movement to the right.
6. Step 2 additional columns to the right.