Description

3d scan

A 3d scan of a doorway

Description

The rangefinder sends out a pulse of sound and measures the time in which it takes for the sound to echo back and return to the sensor. Since the speed of sound is a constant this time can be used to calculate distance. By moving the sensor one line at a time I was able to get a distance reading every two degrees. Even though I purchased a rangefinder with the narrowest advertised beam I could find, it still creates a fairly wide cone the farther it gets from the sensor, so reading any less than two degrees wouldn’t have made much of a difference.

After each line was complete I returned the servo to the beginning of the line and moved it down two degrees. I covered an area 150° wide and 90° high. By taking a reading every 2° I had 75 x 45 ‘pixels’ for a total of 3,375 bits of information per reading.

I sent this information from the Arduino microcontroller in the device to Processing running on a computer. Processing drew a box of color representing the distance reading at the x and y coordinate based on the vertical and horizontal degrees form the servo motors. I experimented with greyscale and color to represent the distance. Color was better for seeing small changes in more complex areas and greyscale was better for showing large discrepancies in distance and is easier to intuitively tell where objects are located.

Since the pulse from the rangefinder is invisible and inaudible it is difficult to tell exactly where it is pointed and what the shape of the entire sampled area looks like.  To solve this I added a laser to next to the sensor to give an approximation of where the sensor was pointed. I also placed a camera on a tripod behind the device and took a long exposure while the sensor was moving. The laser created trails that gave an estimation of where sensor had visited.

Materials

LV-MaxSonar ® -EZ4™ ultrasonic rangefinder
Arduino microcontroller
2 servos on a pan and tilt mount
5v laser

Created by Matthew Styer for Digital Innovation Design class as part of Philadelphia University’s M.S. in Digital Design.

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