Video surveillance has proven itself to be an advanced sensor with benefits. Serving as a remote set of eyes, video surveillance allows a virtual presence in off-site locations from a single point. What's more, video cameras cover a large contiguous swath of view, allowing a panning camera to steadily and consistently sweep a search pattern.
Video systems can also function in locations where humans cannot. The earliest known video surveillance technology was used to safely monitor the development and launch of V-2 rockets in 1942. From a safe distance, scientists and engineers could observe performances and identify failures.
Since then, video systems have acted as an extension of our eyes and ears. A steady stream of technology developments and manufacturing advancements have taken video surveillance to such a level that we feel comfortable relying on it for security purposes.
First Light
Light-sensitive materials can change their resistance or conductance based on the presence or absence of light. Early monochrome video systems like the RCA Vidicon camera system of the 1950s involved vacuum tubes featuring a light-sensitive selenium plate that acted as the focus of the image to be sensed.
An electron beam would scan the plate and the resulting current was directly proportional to the amount of light hitting that section of the plate at that exact time. Thus, the raster-scanned tube produced a rudimentary electronic video signal that could easily be transmitted long distances. The CRT television took this signal in reverse order, scanning a phosphor screen with the electron beam to re-create corresponding light levels in the image.
For decades, video was limited to monochrome sensing and displaying of images in real time. Color filters in front of each sensor limited the analog level to the intensity of the constituent colors in order to create color sensors. Color phosphors placed in the path of the electron beam were used to create colors. The advent of colorburst crystals helped to synchronize color components in the video signals.
Steady advances made improvements in these tubes over time, including better resolutions, lower power, lower cost manufacturing, and higher reliabilities. The Closed Circuit Television (CCTV) and broadcast industries were born and driving development at an even quicker pace.
On the down side, these technologies used fragile glass and the circuitry needed used higher voltages. Size constraints made tube-based image sensors a large and bulky assembly. Thanks to modern semiconductor technology, this is no longer the case.
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