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Geometry, Focus, Registration
Getting the Image Square, Sharp and Aligned
The first performance category we address is Geometry, Focus and Registration. Here we discuss and evaluate the size and shape of the image, the quality of focus, and the registration of the three colors to each other.
The most basic pattern used here is the
Convergence Pattern (WV-52),
and the most complicated pattern is the
Complex Pattern (WV-51). For optimal results with digital, fixed pixel displays, these patterns require that the PC graphics output resolution exactly match the display resolution for a pixel by pixel mapping. The display should be set for a "true" display, and not be scaled or resized. If there is any question, check the
Alternating Pixel Pattern
(WV-53) - looking up close you should see the pixels making clean alternating ON/OFF column and hatch patterns. It should not appear to be noisy, or appear to be clear in some areas but blurry in other areas - if it is, you may be able to correct it by selecting an automatic alignment mode, or by adjusting Clock and Phase settings in the display .
The
Convergence Pattern is used to reveal several display characteristics, such as . . . .
1. Screen Size in Pixels: The squares are each 100 pixels on an edge, so the screen size in pixels can be quickly approximated by simply counting squares and multiplying by 100. (Of course, if you don't have a pixel by pixel match, the squares will not be 100 pixels per edge.)
2. Linearity: The lines should be perfectly straight and the squares should be perfectly square
(equal horizontal and vertical sides) over the entire screen. Thus the squares should appear to be the same size and shape over all areas of the screen, which indicates good linearity. (If you don't have a pixel by pixel match, the squares may appear as rectangles.)
3. Color Registration: For a critical color registration evaluation, carefully check the lines making up the edges of the squares. These lines are broken up into a sequence of segments that goes white-green-red-blue-green-white, and these all ideally lie in a perfect line. You can thus compare the registration of the three colors either by looking at the white line segments and looking for the
lack of color fringing, or by directly comparing any color to
any other color at the point that they meet. Ideally these
line segments, both going up-down and left-right, will line up
perfectly to form straight lines. For CRT
projectors, the registration (convergence) adjustments can be used to critically set the alignment of the three colors. Most digital projectors don't provide any adjustments, so you can just evaluate the color registration. Note that for direct view CRTs with phosphor "stripes", as well as plasma and LCD panels, the red, green and blue pixels don't overlap, but are offset from each other, typically by 1/3 pixel going left-right, so perfect registration is impossible, and the small error will be the same over the entire screen.
4. Focus: In the center of each square you will find small squares for each color plus white, and each square has a single dot inside. Using this array of squares you can quickly check and adjust, if possible, the focus
(optical and/or electronic, as available) for each color at all areas of the screen.
The
Complex Pattern is used to further reveal these and other related characteristics, including . . . .
5. Focus: Focus evaluations can be made using small "plusses", a small square, and a single dot - all for each color and in different screen areas.
6. Color Registration: Color registration can be further evaluated by reviewing the nested color boxes - the boxes should appear perfectly centered within each other, and there should be a single pixel gap between the boxes.
7. Display Resolution: Display resolution can be checked by reviewing the small sections of alternating rows of ON/OFF pixels, alternating columns of ON/OFF pixels, and the staggered ON/OFF pixel mesh.
8. Linearity: The circles can be used to check for display linearity - they should be very nearly perfect circles in all screen areas.
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