1-6 The Road to Dligital Teleivsion
The Nipkow disc was capable of about 4,000 picture “dots” (or pixels) per second. The scan-
ning process analyzed the scene by dissecting it into picture elements. The fineness of picture
detail that the system was capable of resolving was limited in the vertical and horizontal axes by
the diameter of the area covered by the aperture in the disc. For reproduction of the scene, a light
source controlled in intensity by the detected electrical signal was projected on a screen through
a similar Nipkow disc rotated in synchronism with the pickup disc.
Despite subsequent improvements by other scientists (J. L. Baird in England and C. F. Jenkins
in the United States) and in 1907 the use of Lee De Forest's vacuum-tube amplifier, the serious
limitations of the mechanical approach discouraged any practical application of the Nipkow disc.
The principle shortcomings were:
• Inefficiency of the optical system
• Use of rotating mechanical components
• Lack of a high-intensity light source capable of being modulated by an electrical signal at the
higher frequencies required for video signal reproduction.
Nevertheless, Nipkow demonstrated a scanning process for the for the analysis of images by dis-
secting a complete scene into an orderly pattern of picture elements that could be transmitted by
an electrical signal and reproduced as a visual image. This approach is—of course—the basis for
present-day television.
Nipkow lived in Berlin, although he was of Russian birth. The U.S.S.R. claims a Russian
invented television, not because of Nipkow, but another man who experimented with the Nipkow
disc in 1905 in Moscow. The Germans, English and Japanese also claim their share of the fame
for inventing television.
No one argues, however, that credit for the development of modern electronic television
belongs to two men: Philo T. Farnsworth and Vladimir Zworykin. Each spent their lives perfect-
ing this new technology.
1.1.2b Zworykin: The Brains of RCA
A Russian immigrant, Vladimir Zworykin came to the United States after World War I and went
to work for Westinghouse in Pittsburgh. During his stay at the company, 1920 until 1929, Zwo-
rykin performed some of his early experiments in television. Zworykin had left Russia for Amer-
ica to develop his dream: television. His conception of the first practical TV camera tube, the
Iconoscope (1923), and his development of the kinescope picture tube formed the basis for sub-
sequent advances in the field. Zworykin is credited by most historians as the father of television.
Zworkin's Iconoscope (from Greek for “image” and “to see”) consisted of a thin aluminum-
oxide film supported by a thin aluminum film and coated with a photosensitive layer of potas-
sium hydride. With this crude camera tube and a CRT as the picture reproducer, he had the essen-
tial elements for electronic television.
Continuing his pioneering work, Zworykin developed an improved Iconoscope six years later
that employed a relatively thick, 1-sided target area. He had, in the meantime, continued work on
improving the quality of the CRT and presented a paper on his efforts to the Eastern Great Lakes
District Convention of the Institute of Radio Engineers (IRE) on November 18, 1929. The pre-
sentation attracted the attention of another former Russian immigrant, David Sarnoff, then vice
president and general manager of RCA. Sarnoff persuaded Zworykin to join RCA Victor in
Camden, NJ, where he was made director of RCA’s electronics research laboratory. The company