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Tektronix provides test and measurement instruments, solutions and services for the computer, semiconductor, military/aerospace, consumer electronics and education industries worldwide.
A parallel data channel used in mainframe computers that supports data transfer rates of 100 Mbps.
Industry:Software
Distortion which results when all of the frequency components of a signal are not transmitted with the same gain or loss. A departure from “flatness” in the gain/frequency characteristic of a circuit. Refer also to the Frequency Response discussion.
Industry:Software
Proponent of the CCF ATV scheme.
HRS plans to offer other ATV schemes, including one using synchronised electron beam spatial modulation (turning each scanning line into a series of hills and valleys) in both camera and receiver to achieve increased vertical resolution.
Industry:Software
Since picture monitors have a nonlinear relationship between the input voltage and brightness, the signal must be correspondingly predistorted.
Gamma correction is always done at the source (camera) in television systems: the R, G, and B signals are converted to R 1/g, G 1/g, and B 1/g. Values of about 2.2 are typically used for gamma. Gamma is a transfer characteristic. Display devices have gamma (or at least CRTs do).
If you measure the actual transfer characteristic of a CRT used for either television display or computer display, you will find it obeys a power law relationship: Light = Volts^gamma where gamma is 2.35 plus or minus 0.1. CRTs have values between 2.25 and 2.45.
2.35 is a common value. It is a function of the CRT itself, and has nothing to do with the pictures displayed on it. CRT projectors are different; green tubes are typically 2.2 while red is usually around 2.1 and blue can be as low as 1.7. But there are no direct-view CRTs which have values lower than 2.1. Pictures which are destined for display on CRTs are gamma-corrected which means that a transfer characteristic has been applied in order to try to correct for the CRT gamma. Users of TV cameras have to accept the characteristic supplied by the manufacturer, except for broadcasters who have adjustable camera curves (the video engineers adjust the controls until they like the look of the picture on the studio monitor in their area). Even so, no TV camera uses a true gamma curve; they all use rather flattened curves with a maximum slope near black of between 3 and 5. The higher this slope, the better the colorimetry but the worse the noise performance.
Industry:Software
Undesirable variations that occur above the 15.75 kHz line rate.
Industry:Software
A) The RGB data is corrected to compensate for the gamma of the display. b) Historically, gamma correction was a precompensation applied to the video signal at the camera to correct for the nonlinearities of the CRT (i.e., power function of the electron gun) and, as such, it was the inverse of the electron gun function. It is now widely used, however, to describe “the total of all transfer function manipulations” (i.e., including the departures from a true power law function), whether inherent or intentionally introduced to act upon the video signal for the purpose of reducing the bandwidth for signal processing, making the image on the final display conform to preconceived artistic objectives, and/or providing noise suppression, or even bit rate reduction. c) The insertion of a nonlinear output-input characteristic for the purpose of changing the system transfer characteristic. As this usage has grown, the IEEE definition correlating gamma to an analytical function becomes optimistic. d) An adjustment factor used to correct an image’s intensity when it is displayed.
Display devices can perform gamma correction but raster images can also be gamma corrected with software prior to display.
Industry:Software
Interference effects which occur at high frequency. Generally considered as any frequency above the 15.75 kHz line frequency.
Industry:Software
The common magnetic constituent of magnetic tapes in the form of a dispersion of fine acicular particles within the coating.
Industry:Software
A very new type of image sensor (target) for a camera tube. HARP target tubes are about 10 times more sensitive to light than conventional tube types and have been demonstrated to offer hope of overcoming the sensitivity drawbacks of HDTV cameras.
Industry:Software
A table of constants which functions as a nonlinear amplifier to correct the electron gun drive voltages so that the CRT display appears to be linear. Because the gamma function for each colour is different in a typical CRT, different values for each colour are usually contained in the gamma table. This processes is called Gamma Correction.
Industry:Software
