pixel area is closer together because there is no shift reg-
ister between each vertical row of pixels. This will make a
difference in some video applications.
CCD Size Format
Currently there are three format sizes available for the
industrial and security markets; 1/3", 1/2", 2/3" formats.
Oddly enough the size format does not represent the
actual size of the CCD. The formats were developed
under the old rules from the video tube (VIDICON) days.
The trend in size format has been going from big to small.
The 1/3" is the latest size format. The idea is to make the
CCD smaller so that the overall camera size is reduced.
Take a look at our TM-7X camera for size. At PULNiX this
is considered our smallest, but don't be surprised if a
smaller one is unveiled soon. One problem with smaller
CCD's is that the equivalent FOV (field of view) is reduced
thus requiring a change in optics. This can cause a prob-
lem for existing applications that are already spec'd. in.
By the way, if you do not know what FOV is, don't panic it
will be discussed later.
The ratio between horizontal and vertical is close to 4 to 3
or 4/3. This again follows the video tube type cameras.
This is known as the ASPECT RATIO. This ratio is com-
mon to broadcast specifications.
Video Format
To understand the format that a video camera will output
to the outside world we need to look at a few standards
that various committee's have set. The most common in
North America is the RS-170 and NTSC (National
Television System Committee) standards. For Europe,
CCIR (International Radio Consultative Committee) and
PAL (Phase Alternation Line) are the common standards.
Basically, RS-170 and CCIR are standards for black and
white video cameras, and NTSC and PAL are standards
for color cameras. The standards are necessary in that
video cameras and other devices such as TV monitors,
video frame grabbers, and VCR's must have a common
way of interacting with each other. The majority of the
standards have to deal with the timing of various signals.
We will discuss this next.
Video Timing
In order for a device such as a video monitor to receive a
video signal from a video camera, the camera must pro-
vide signals that the monitor can understand. This
includes the signal amplitude ( voltage level) as well as
frequency timing ( signal occurrence). RS-170 and NTSC
have similar formats, but the NTSC must also contend
with color information as well. The basic timing require-
ments for a RS-170 format is that the camera outputs two
fields of video information every 1/30 of a second. It takes
two fields to make up a frame (full resolution) of video.
The camera outputs one field at a time (1/60 of a second
or 60 Hz). For every field there is a vertical pulse generat-
ed inside the camera. Between two vertical pulses there
are 262 .5 pulses generated called horizontal signals. The
horizontal signals specify a new horizontal line. Each field
consists of 262.5 horizontal lines. Two fields (frame) will
make up 525 lines of video every 1/30 of a second. Now
for CCIR and PAL these timing signals change a bit. First
of all the vertical timing changes to 50 pulses per second
(50Hz). Secondly, the horizontal pulses occurs 312.5
times per vertical pulse. This makes up the 625 lines
(frame of resolution) available on a CCIR standard. The
vertical and horizontal signals that were described here
are called the H & V SYNC timing. When both signals are
combined together this is called a COMPOSITE SYNC
SIGNAL.
2
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