A License Plate Recognition and Speed Detection System - Index of
A License Plate Recognition and Speed Detection System - Index of
A License Plate Recognition and Speed Detection System - Index of
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characters were first extracted. This was made possible as defined in the algorithm given in<br />
Section V.C.3. This algorithm works much better than the first algorithm because the intensity<br />
contrast between license plate characters <strong>and</strong> the license plate itself remains constant across all<br />
vehicle images whereas intensity contrast between the license plate <strong>and</strong> the surrounding region<br />
changes from vehicle to vehicle. Test case results improved after this was fixed, but there were<br />
still some test cases that failed. It was found that when the registration sticker was placed closely<br />
to one <strong>of</strong> the license plate characters, that character would be misrecognized. This was a result <strong>of</strong><br />
not having an optimal intensity threshold. The sticker was being seen as part <strong>of</strong> the license plate<br />
character. To fix this, the intensity threshold algorithm as described in V.C.3 was written, so that<br />
the optimal threshold intensity was calculated by the s<strong>of</strong>tware, <strong>and</strong> the registration sticker was no<br />
longer being seen as part <strong>of</strong> a license plate character.<br />
Once this had been fixed the s<strong>of</strong>tware worked well against stationary objects. However,<br />
further testing showed that if the license plate was visible to the camera for only a very short<br />
period <strong>of</strong> time, the recognition s<strong>of</strong>tware had trouble recognizing the characters. This test case<br />
was done by moving a piece <strong>of</strong> cardboard quickly in front <strong>of</strong> <strong>and</strong> away from the license plate.<br />
This was puzzling, because at 30 frames a second, the camera should be able to capture the<br />
license plate image no matter how fast I move the cardboard. I discovered where the problem<br />
was by watching the application “Processed Image” window. When I moved the cardboard away<br />
from the plate, the license plate characters did not suddenly appear in the “Processed Image”<br />
window. Instead, the license plate characters faded in slowly even though images were being<br />
received at 30 frames per second. This wasn’t due to a bug in the code, but is an inherent trait in<br />
CCD chips used by common video cameras. It takes time for sensors in the CCD chip to react to<br />
changes in color. Data may be pulled from the CCD chip at 30 frames per second; however,<br />
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