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Awaveform monitor is a special type ofoscilloscope used intelevision production applications. It is typically used to measure and display the level, orvoltage, of a video signal with respect totime.
The level of a video signal usually corresponds to the brightness, orluminance, of the part of the image being drawn onto a regular video screen at the same point in time. A waveform monitor can be used to display the overall brightness of a television picture, or it can zoom in to show one or two individual lines of the video signal. It can also be used to visualize and observe special signals in thevertical blanking interval of a video signal, as well as thecolorburst between each line of video.
Waveform monitors are used for the following purposes:
A waveform monitor is often used in conjunction with avectorscope. Originally, these were separate devices; however modern waveform monitors include vectorscope functionality as a separate mode. (The combined device is simply called a "waveform monitor").
Originally, waveform monitors were entirely analog devices; the incoming (analog) video signal was filtered and amplified, and the resulting voltage was used to drive the vertical axis of acathode-ray tube. Async stripper circuit was used to isolate thesync pulses andcolorburst from the video signal; the recovered sync information was fed to asweep circuit which drove the horizontal axis. Early waveform monitors differed little from oscilloscopes, except for the specializedvideo trigger circuitry. Waveform monitors also permit the use ofexternal reference; in this mode the sync and burst signals are taken from a separate input (thus allowing all devices in a facility to begenlocked, or synchronized to the same timing source).
With the advent ofdigital television anddigital signal processing, the waveform monitor acquired many new features and capabilities. Modern waveform monitors contain many additional modes of operation, includingpicture mode (where the video picture is simply presented on the screen, much like a television), various modes optimized for color gamut checking, support for the audio portion of a television program (either embedded with the video, or on separate inputs),eye pattern andjitter displays for measuring thephysical layer parameters of serial-digital television formats, modes for examining the serial digitalprotocol layer, and support forancillary data and television-relatedmetadata such astimecode,closed captions and thev-chip rating systems. Some digital cameras (such as theNikon Z50II andZ9) allow for waveform monitoring while taking a video.[1][2][3]
Modern waveform monitors and other oscilloscopes have largely abandoned old-style CRT technology as well. All new waveform monitors are based on arasterizer, a piece of graphics hardware that duplicates the behavior of a CRT vector display, generating araster signal. They may come with a flat-panelliquid crystal display, or they may be sold without a display, in which case the user can connect anyVGA display.
