Configuration control
Leuze electronic
DCR 50
58
8.3
Motion detection
The scan engine supports motion detection, which means, the device can detect codes brought into the
field of view and decode them without manually triggering a decode. Motion detect is often used with the
device stationary or mounted, and targets passing in front of it. The device is set to use the minimum inter-
nal illumination possible, and works best when in bright ambient light shining from behind the device.
Motion detection parameters
The motion detection determination uses many parameters. The exposure time, gain, and illumination are
camera settings used to get the best picture to determine whether or not objects have moved into the field
of view. They all have minimum and maximum values which the AGC (Automatic Gain Control) uses to get
that best picture.
• The exposure is how long the camera “shutter” lets light into the detector array. If it is not open long
enough, all the device can see is blackness. If it is open too long, all the pixels are over-exposed, and
the picture is white. By setting the minimum and maximum time, the AGC is allowed to open the shut-
ter. We can try to force the AGC to not over- or under-expose the picture.
• The gain is the amount of amplification the AGC can use to attempt to increase the contrast of the pic-
ture between light and dark pixels. Setting the minimum too low does not produce enough contrast, and
setting the maximum too high overflows the AGC. Thus, the gain range helps the AGC to optimize the
contrast of the data without overflowing the calculations.
• The illumination is how much additional light the device shines on the image to increase the sensitivity
of the motion detection algorithm. The more illumination, the easier it is to read the codes, however, it
also makes the device more obvious in a given environment. By setting the minimum and maximum il-
lumination, the device can be set to add much less light into an environment.
• Thresholds are used to detect motion in the following way:
• A baseline is created when motion detection starts. Thus, the device has a set of values to com-
pare against.
• Motion detection finds pixels that vary (more or less) from the baseline by more than the
pix-
elThreshold
threshold. Motion detection then filters out groups of pixels detected when the number
of consecutive pixels is less than the
blobThreshold
threshold, considering it a false positive.
• When the total number of pixels not filtered out is greater than the total threshold, the device deter-
mines that a code has come into the field of view: motion detected.
• The motion detect takes three blocks ‑ a left block, a center block, and a right block ‑ from the complete
image from which to detect motion. Motion in any one of the three blocks or in the combined detection
from all three blocks causes motion detection.
