B&K Precision 1253 - Manual - Manual (Page 28)

3. Geometry Calibration
Geometry calibration is the process of adjusting the display for the correct picture size, while ensuring that
horizontal and vertical lines in the picture remain straight and parallel to the edges of the picture and evenly spaced
from one another when using an appropriate calibration pattern. Displays may have an array of adjustments for this
purpose including horizontal and vertical position, size, linearity, tilt, bow, keystone, pincushion and others. Many
CRT projectors permit the green CRT to be turned on by itself to adjust geometry and then the remaining red and
blue CRTs are adjusted later for the best convergence.
BK-1253 Geometry Adjustment Patterns:
Cross Hatch Overscan-Bounce
The BK-1253 includes a 16:9 Crosshatch with vertical and horizontal white lines against a black background. The
16 x 9 grid pattern produces square cells on a HDTV monitor for easy adjustment or measurement of horizontal
and vertical linearity.
The Overscan-Bounce pattern is marked with single-pixel wide guide lines that are approximately 2.5% from the
edges of the display (at 2.5%, 5%, 7.5% and 10%)
Geometry Adjustment Procedure:
Use the available adjustment controls to fit the 16:9 Crosshatch calibration pattern to the display screen size and to
optimize the straightness and spacing of the grid pattern lines. Many direct-view and rear-projection TVs will work
best when adjusted for about 3% overscan using the 16:9 pattern guidelines. This allows for some change in
picture size with changes in APL, and also allows for some variation in geometry at the edges of the picture so that
no portion of the screen is without picture coverage. In some cases more overscan may be required to cover these
variations. It may be possible to adjust high-performance front projectors for satisfactory performance with less
overscan. Use the Overscan-Bounce pattern to adjust for specific percentage values.