Glossary
G-4
ni.com
N
NI-IMAQ
Driver software for National Instruments IMAQ hardware.
NTSC
National Television Standards Committee. The committee that developed
the color video standard used primarily in North America, which uses
525 lines per frame.
See also
P
PAL
Phase Alternation Line. One of the European video color standards.
PAL uses 625 lines per frame.
See also
PCI
Peripheral Component Interconnect. A high-performance expansion bus
architecture originally developed by Intel to replace ISA and EISA.
PCI offers a theoretical maximum transfer rate of 132 Mbytes/s.
PCLK
Pixel clock signal. Times the sampling of pixels on a video line.
pixel aspect ratio
The ratio between the physical horizontal size and the vertical size of the
region covered by the pixel. An acquired pixel should optimally be square,
thus the optimal value is 1.0, but typically it falls between 0.95 and 1.05,
depending on camera quality.
pixel clock
Divides the incoming horizontal video line into pixels.
R
resolution
(1) The number of rows and columns of pixels. An image composed of
m
rows and
n
columns has a resolution of
m
×
n
. This image has
n
pixels
along its horizontal axis and
m
pixels along its vertical axis. (2) The
smallest signal increment that can be detected by a measurement system.
Resolution can be expressed in bits, proportions, or a percentage of full
scale. For example, a system has 12-bit resolution, one part in
4,096 resolution, and 0.0244 percent of full scale.
ROI
Region of interest. (1) An area of the image that is graphically selected
from a window displaying the image. This area can be used to focus further
processing. (2) A hardware-programmable rectangular portion of the
acquisition window.
