3D Laser Scanner

  
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The red laser line slowly sweeps the object (here a Fabuland lamb head). Behind the scanned object, two planes with a 90 ° angle provide reference to the scanning software. They are also marked with regularly spaced black dots that serve during the calibration process that inform scanning software of webcam characteristics, field of view, optics distortion.
3D Laser Scanner - schematic

The laser sweeping mechanism. The NXT motor is down-geared by 1:2880, providing a really slow motion. The two white rubber bands maintain tension on the gears to avoid gear lash. The NXC code allows to set the scan speed through motor speed variation, and to move the laser at maximum speed during scan setup. Below the sweeping mechanism there is a Logitech Pro 9000 webcam. This high quality webcam provides very good images, thus detailed scans (though I made my first tries with a much lower cost Trust webcam). The drawback of this webcam is that it doesn` have a screw mounting hole, here is how I added one. The laser itself is powered from the NXT through a sensor port. The small interface board in the middle of the cable contains a transistor to switch the laser on/off (the same way as the LED of NXT light sensor) and a series diode to lower voltage. Schematics of the control interface. D2 is a small silicon diode (1N4148) whose purpose is to lower voltage on the laser, since lightly loaded NXT IO supply can exceed the 4. 5V maximum rating of the laser used. Q1 is a small NPN transistor (BC548, 2N3904. ) used to control laser with DIGI0 NXT I/O pin. This is the same circuitry as the one used in the LEGO light sensor to control the red LED, so the laser can be controlled the same way. Program the port as a reflected light sensor to light up the laser, and as an ambient light sensor to put it off. Top view of the scan bench....



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