Vectorscope

A vectorscope (often with English. Referred vectorscope ) is a specialized mainly for video technology instrument. Image signals are transmitted in the analog television technology by vector modulation, which can be considered difficult only with a conventional oscilloscope. The vectorscope, however, allows a specialized representation of the color vectors. As the main application of a vectorscope the color balance as well as the analysis of the image quality is mentioned. Likewise, the vectorscope is useful in the analysis of copy protection method in video technology, as these are mostly based on a manipulation of the color vectors. Measurement solutions for digital modulation methods as found come on digital TV used to be, however, usually not referred to as vectorscope, but as a vector analyzer.

As a vectorscope and a goniometer (stereo visual display unit) is referred to in audio engineering.

Operation

On older devices the color vectors are displayed visually in a circular scale with the help of a cathode ray tube. Today, the usual gauges calculate the vector representation by software in real time and are usually equipped to represent the result by LCD screens.

To display in the vertical direction of the color difference signal (RY ) ( red minus luminance ) and in horizontal direction, the color difference signal ( BY) are applied ( blue minus luminance ). Up to constant factors, these color difference signals correspond to the U and V signal in YUV color model. The determination of the two color difference signals from the RGB color space is done according to the EBU specification the following equations, where R represents the color value of red, G for green and B for blue:

For the determination of the two color values ​​U and V according to the following relationship:

In television technology are used for the X and Y deflection directly processes the reduced color difference signals U and V, where U is plotted along the X axis and V in the Y- axis.

The greater the saturation of a color, the further out are the color locations shown. Achromatic tones give a point in the center of the screen ( black / white / gray values ​​). A color can be defined by specifying two values ​​(angle on the vectorscope ) and color saturation ( distance from the center of the scale ).

The designated with I and Q lines indicate the color axes of the YIQ color model. Since skin color normally lie on the I- line, it is displayed as a reference for color correction, because skin tones that differ greatly from that line, unnatural to the human eye.