the life of Philo T Farnsworth - Early Television Foundation

1O8
THE STORY OF TELEVISION
method is now in universal use as a generating pulse to control
television scanning. Along with the initial
conception of his
electronic television scheme, this achievement ranks among
Farnsworth's greatest contributions to television.
By the generation
of the saw-tooth wave form he had succeeded in clarifying
the television image and freeing it from blur and smudge.
The pursuit of this elusive wave form was one most fascinating
to the observers of the progress Farnsworth was making in
his television image. The results obtained were easily discernible
from week to week. In the beginning the efforts seemed to be
hopeless, but gradually the smear down the center of the picture
disappeared, the ghost image faded out, the picture field
cleared, and the image became sharper.
During the period of Phil's intensive work on this problem
he had two scanning chassis built. One illustrated the sine-wave
scanning and the other the saw-tooth wave he was striving to
perfect. The problem he was struggling with was clearly pointed
out to me on one of my visits to the laboratory in the early part
of the development
Stepping up to one of the panels Phil turned on the sinewave
scanner. "See that ghost image there" he asked.
It was unmistakable. There was a second image in the background
whose brilliance in comparison with the primary picture
was reminiscent of the relative light values of the primary
and secondary rainbows in the sky.
"If you'll look closely," Phil said, "you'll see that the scanning
lines have sort of a circular path. The ghost image is in
the return lines. We've got to get rid of it
by straight-line scanning
and by cutting down the time of the return scanning so
that this ghost disappears."
Then he turned on the image on the panel generating the