|
Dot
Pitch Defined for CRTs
Definition
Dot pitch is the distance between phosphor dots that are alike
in color. These phosphor dots are tiny red, green and blue
phosphors. The image you see on the display is composed of
these tiny phosphors (called triads - a group of one red,
one blue and one green colored phosphor) that produce colored
light patterns. The display creates the illusion of other
colors by lighting these phosphors up in different concentrations.
 Dot
pitch is sometimes referred to as phosphor pitch. The image
displayed will be more detailed and graphic the more minute
and less distance the dots are to one another. The image will
look grainer when the dots are furtherer apart.
Measurement
Dot Pitch is measured in millimeters (mm) where the smaller
the number, the sharper the image. The common range of dot
pitch is 0.25 - .31mm. But some of the larger displays can
go as high as .80mm
Types
There is more than one kind of pitch. The term Dot Pitch,
which is associated with Shadow Mask CRTs using round dots,
is often used to describe the following types of pitches:
| |
Shadow
Mask
A metal screen filled with holes. Three electron beams,
generated by colored guns, pass through the focus to a
single point on the tube's phosphor surface. There are
two types of pitch found in Shadow Mask CRTs. |
|
| |
Dot
Pitch - This is measured as vertical pitch, the distance
between the centers of two same-colored round dots
Slot Pitch - The slots are measured with vertical or
horizontal pitch.
|
|
| |
Aperture
Grille Mask
Sony Trinitron™ tubes use masks, that they call the
"aperture grill", to separate strips instead
of each dot . The aperture grill replaces the shadow mask
with a series of narrow alloy strips that run vertically
across the inside of the tube. Their equivalent measure
to a shadow mask's dot pitch is known as "stripe
pitch". Rather than using conventional phosphor dot
triplets, aperture grill-based tubes have phosphor lines
without horizontal breaks, and therefore rely on the accuracy
of the electron beam to define the top and bottom edges
of a pixel. Since less of the screen area is occupied
by the mask and the phosphor is uninterrupted vertically,
more of it can glow, resulting in a brighter, more vibrant
display.
|
|
How
it relates to resolution
Resolution depends on the sharpness of the CRTs electron beams
and its dot pitch. The dot is the smallest physical visual
component in the display. The smallest programmable visual
element is a pixel. The pixel maps to the dot when the display
is set to the CRTs maximum resolution. If the CRT is set to
a lower resolution, then the pixel will contain multiple dots.
This in turn will make the image appear larger on the screen.
Other
Important Factors
You can't judge a monitor on dot pitch alone. There are other
important factors that will determine the clarity - or resolution
- of the display image. Here are just a few of them:
| |
Bandwidth
Video bandwidth is how quickly and precisely the display
electronics can regulate the beam. This is an important
factor in determining the sharpness and image quality
of the displayed image.
Convergence
Convergence is the alignment of 3 separate red, green
and blue beams. This alignment is critical for producing
sharp characters that are the correct color.
Focus / Beam Size
Focus is the size of the beam that strikes the phosphors
and is the finest detail that can be displayed. The
beam size is always larger than the dot pitch.
Video
Peripheral Quality
The video board signals quality and the video cables
length and quality can interfere with the sharpness
and image quality of the displayed image.
|
|
LCDs measure
dot pitch as the distance between subpixels of the same color
in pixel triads.
|
