Rockwell Automation 5370-CVIM2 Module - Manual (Page 81)

Chapter 3
Image Acquisition Parameters
3–42
•
Period (
ms) –– This is amount of time required to scan one horizontal
line. It is equal to the reciprocal of the horizontal frequency. (For the
2801–YC camera, the horizontal frequency is 15.734KHz; thus, the
period is 1
B 15.734KHz = 63.557ms.)
•
HD Length –– This is the duration, stated in microseconds, of the “active
low” HD (horizontal drive) pulse provided to the camera from the CVIM2
system.
•
Restore Start (
ms) –– This is starting point of the DC restore pulse, which
the CVIM2 system uses during each horizontal line to “sample” the
analog composite video signal at a time when the camera sees “black.”
(For the 2801–YC camera, the center of this pulse is located halfway
between 6.3
ms and 10.8ms after the start of the horizontal drive pulse;
thus, the start of the restore start pulse is 8.2
ms after the start of the
horizontal drive pulse.)
•
Restore Length (
ms) –– This is the duration of the DC restore pulse. (For
the 2801–YC camera, it is 1
ms.)
•
Acq. Center (
ms) –– This is the center of the image sensing area (the
acquired picture), in microseconds, after the start of the horizontal drive
pulse. (For the 2801–YC camera, it is 37.20
ms after the start of the HD
pulse.)
•
Acq.Pixels (Pixels) –– Refer to the Editing Standard Allen–Bradley
Cameras section for details.
•
Acq.Phase (Pixels) –– Refer to the Editing Standard Allen–Bradley
Cameras section for details.
•
Total (Pixels) –– This value represents the number of times that the
CVIM2 system “samples” each horizontal line of the analog composite
video signal from the camera in the process of digitizing the video signal.
NOTE: The frequency range limit of the CVIM2 system is 10MHz to
20MHz. Since the frequency is a function of the camera’s period and the
Total (Pixels) selection, any combination of these values must lie within
that range. The frequency is the reciprocal of the camera’s period divided
by the total pixels; or stated another way, the total pixels divided by the
period. For example, the period of the 2801–YC camera is 63.557
ms, and
the total pixels is 794. Thus, the frequency is 794
B 63.557ms, or
12.5MHz, which is well within the CVIM2 system’s frequency range
limits.
•
Transfer (1/2 Lines) –– This value applies only to free–running,
interlaced CCD cameras. “Transfer” refers to the process by which image
data is transferred from the image sensor to the shift register for the
current image field. During this time, the CVIM2 will not fire a strobe.
The Transfer value indicates the time, stated in 1/2 lines, around which a
strobe will not be fired. For the 2801–YC camera, the Transfer value is
the 16 half lines, and the transfer time is two half lines before to two half
lines after this point. Thus, the CVIM2 system will not fire a strobe
during that interval.