What Video Cameras Learned from TV

Just what is a video camera? Let’s start with what it is not. A video camera is not a movie camera. A movie camera records images on film. A video camera creates electronic moving images. It has also been called a television camera and that is not entirely untrue since the modern video camera is a great- great grandchild, once removed, of the old TV camera.

Tracing the video camera tree is not an easy task since television was born, not of any one person’s invention but rather, evolved from the efforts and ideas of many people working alone and together over several decades and several countries.

The family tree would stem from two main root systems – mechanical pioneers and electronic pioneers.

Mechanical Pioneers

Paul Nipkow

Paul Nipkow came up with the hypothesis that if one were to dissect an image into small portions, it would be possible to transmit it sequentially. In so doing he discovered television's scanning principle: that light intensities of small portions of an image can be successively analyzed and transmitted over a wire.

He came up with a rotating spiral-perforated disk, called the Nipkow disk that would divide an image into a mosaic of points and lines. While rapidly rotating, the disk was placed between a scene and a light sensitive selenium photocell. The light then passed through a synchronously rotating perforated disk and replicated the image on the projection screen.

Nipkow Disk

The result was an image with a rudimentary 18 lines of resolution. It was 1884 and the world had its first mechanical television system.

In the 1920’s John Logie Baird, a Scottish engineer would use Nipkow’s technology to come up with his patented invention using transparent glass rods to transmit images. In 1924,  he was able to transmit simple face shapes, using reflected light  His transmission across a few feet consisted of flickering images of silhouettes in barely adequate half-tones, but these 30 line images were the first demonstrations of television by reflected light rather than back-lit silhouettes.

Logie and his first transmitter

Even though he would  transmit images in 1927 from London to Glasgow, Scotland, using  438 miles of telephone lines, and in 1928, achieve the first transatlantic television transmission between London and New York, Baird's mechanical system was rapidly becoming obsolete as electronic systems were being developed.

Meanwhile in the United States, Charles Jenkins, an inventor came up with the idea of viewing distant scenes by radio. His first success was a wireless transmission of a photograph of President Harding sent from Washington to Philadelphia. He called his invention Radiovision.

This rudimentary  mechanical television consisted of a mechanical scanning-drum and  a multi-tube radio set that had a special attachment for receiving pictures resulting in a fuzzy 40 to 48 line image projected onto a six-inch square mirror.

Jenkins with Radiovision receiver

 On June 24, 1923 he succeeded in transmitting moving silhouettes, and by June 23, 1925, had progressed to transmitting moving pictures.

Meanwhile in other labs and workshops, inventors were taking an electronic path.

Electronic Pioneers

In 1897, Karl Braun invented the cathode ray tube, the foundation on which modern television would be built. He took a sealed glass tube from which most of air had been removed. At one end, was a negative terminal, or cathode, through which electrons entered the tube. Due to the vacuum atmosphere the electrons formed a moving ray or beam through the tube. Braun discovered that an image could be produced when the ray struck a phosphorescent surface.

Cathode Ray Tube

Using his accomplishment as a building block, Braun used a changing current to deflect the electron beam within the cathode ray tube. The trace remaining on the tubes surface corresponded to the amplitude and frequency of the alternating -current voltage. He then set up a rotating mirror to produce a visible pattern based on the graphical representation of this current. His invention, initially known as Braun’s electrometer, and later as an oscilloscope, not only became the basic component of early television receivers but remained an essential instrument in future electronic research .

A couple of subsequent inventors tweaked the CRT concept a bit:

·         In 1927, Philip Farnsworth invented the image dissector tube and was the first person to transmit an image comprised of sixty lines of resolution.  His subject was a dollar sign from a glass slide, backlit by an arc .By 1928 Farnsworth was using electric scanning in both the pickup and the display device, and when he demonstrated it to the press , he billed it as the first working all-electronic television system.

·          Vladimir Zwroykin, a Russian immigrant, working for Westinhouse was impressed with Braun's invention andbegan to work on improving it. when Westinghouse told him to stop wasting time with this impractible pursuit, he worked on his own time and came up with the"kinescope,"a more sophisticated cathode-ray picture tube, and later, the "iconoscope," the first all-electronic camera tube.

For decades, the cathode ray tube would be the workhorse of televisions and other display devices until its eclipse by the liquid crystal display screen.
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