"A high resolution adaptive image capture system with a FireWire interface."
The
Transport Data Systems license plate capture system uses Point
Grey Scorpion and Grasshopper digital area scan cameras to provide high resolution
lane coverage. The digital video is transmitted via a fiber
link to a standard Firewire interface board located in the image
processor. The Firewire link provides a means for initialization
and control of the camera by the image processor. The cameras
are availabe with narrow, medium or wide lane coverages and in
either a color or a monochrome version. The monochrome version
is also capable of operating in the near IR band. For front
end capture installations, TDS provides the system with a pulsed
LED illuminator (color or near IR). The use of near IR for the
front camera eliminates the blinding effects of visible light
illumination and the possibility of capturing the identity of
the driver. The combination of a visible rear plate capture
system with a near IR front based capture system provides the
optimum in automatic license plate capture performance. The
use of identical components for each part of the system eliminate
the need for multiple sets of spare parts and repair procedures.
The image processor provides for the capture of the image as well as the compression of the image and the transmission of the image to an image processing center. The image processor relies on a separate trigger input for control of the image process. Further it expects a signal from the lane controller indicating that the most recent image needs to be stored and transmitted to the image processing center. The trigger and the image save messages can be transmitted from the lane controller to the image processor via a serial link or an ethernet link.
Transport Data Systems provides the image capture and camera control software in the image processor. The key to good capture performance in the fare collection environment lies in the ability of the camera control module to cope with various lighting conditions in the lane. The TDS camera control module uses a set of adaptive algorithms which examine image data over a series of time periods to eliminate the need for extensive setup and tuning. When the system is turned on, the automatic tuning process begins. The correct camera and lens settings are determined within a few images after startup. The algorithm then learns the correct settings over time with the initial training process being completed within 24 hours. The system is capable of providing better than 90% usable images over an extended period of operations with no further tuning required.
