intensity mode in urg_node while using hokuyo sensor

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In intensity mode, the intensity of laser returns is also read out and written to the "intensities" field of the LaserScan message. So for every scan point you also get a measure of how much IR light has been reflected. You can think of it as the LIDAR returning a 1D image (as opposed to the 2D intensity grid for a monochrome camera). In fact, multiple scans with intensity data can be used to generate an image that looks similar to a normal camera image (just in the IR range). The Calibrating the PR2 tutorial page has a few example of images generated using the PR2´s tilting LIDAR.