Tektronix AWVG1, User Manual

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AWVG1 Wideband Video Generator User Manual
C- 1
Appendix C: Zone Plates
This appendix provides reference information about zone plate patterns. Refer to
the
Operating Basics section of the manual for instructions on using the AWVG1
Generator module to generate zone plate signals.
Zone Plate Patterns
Zone plate video test patterns are called zone plates because the classical circular
pattern looks like an optical zone plate (which uses the principles of Fresnel
diffraction to focus and intensify light). However, the name has been applied to a
variety of stationary and moving monochrome test patterns.
Figure C--1 shows two enlarged optical zone plates. The white areas are
transparent and the black areas are opaque. The precise spacing of the rings
focuses and intensifies light that passes through the plate.
Figure C- 1: Optical zone plates (enlarged)
Zone plate patterns are made up of sinusoidal variations in luminance, with the
peaks of the sine waves resulting in white areas on the video screen and the wave
troughs shown as gray or black.
The cycles can occur in all three of the video dimensions: horizontally (along
each line of the picture), vertically (down the video frame), and temporally (with
time). The three dimensions are often referred to as X, Y, and T, respectively.
The luminance of any point in the picture (physically on the screen and in time)
is determined by the value of sine at that particular point; the value of sine