by Dan Mauch
Finally ... affordable 3D! Three dimensional (3D) scanning
technologies have been around for several years but for
most of us these have been unavailable. The very high
costs and complexities involved have attributed to this. While
there have been some low cost attempts that have been
posted on the web, most have been fairly crude.
With what I am about to show you now, you will
be able to make 3D scans at a fraction of the cost
while achieving quality comparable to some of the high
end products out there. This scanner can be used
by graphic artists, gamers, reverse engineers and
especially by those that have computer aided design
(CAD) computer aided manufacturing (CAM)
programs and equipment for rapid prototyping or
3D capable computer numerical control (CNC)
machines. Best of all, this project involves nuts,
volts, lasers, a video camera, and a computer!
First, a little background. There are many
types of 3D scanners but, basically, these can be
categorized into “contact” and “non-contact”
scanners. The contact types are straightforward in their
design and use. These use a probe that contacts the object
to be scanned. A computer program runs a mechanism that
would move the probe (typically, a gimbal mounted switching device)
back and forth over the object recording where the probe makes contact.
At the end of the cycle, it produces what is a called a point cloud file. The file
includes the locations of each contact point that was recorded. A single point cloud
entry would look like this: X1.124, Y.097, Z -1.075. While they can be very precise,
contact type scanners are also very slow, taking hours or days to scan an object.
Non-contact scanners come in many configurations. They are usually much
faster, taking minutes and sometimes only seconds to scan an object. Optical non-contact 3D scanners are the most popular. They can be set up for topographical
scanning that takes 3D images of an object in a frontal fashion for scanning a face,
medallion, or coin, for instance. Another configuration is full object scanning that
rotates the object 360 degrees and are called “circumference scanners” (3DCS).
These scan the rotating object, capturing most of the details in one session. The
scans require minimal post processing, since it is not necessary to merge multiple
scans. Optical non-contact 3D scanners typically involve the use of a laser to project
a line over the object, a turn table to rotate the object, a camera to register the scan, and
a computer with software to take the images from the camera and process them into a
3D model representation (see Figures 1 and 2). Many parameters need to be set to do this
correctly. It may seem complicated at first, but once a few scans are made it becomes easier.
The scanner that this article will address is a 3D circumference scanner. It uses a Digital