Table of Contents
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Welcome to DAVID (help_welcome.htm)
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Camera Calibration (help_camera_calibration.htm)
-
3D Laser Scanning (help_3d_scanning.htm)
-
Shape Fusion (help_shape_fusion.htm)
-
Frequently Asked Questions (help_faq.htm)
-
General Hints (help_hints.htm)
Welcome to DAVID
DAVID is a freeware software that allows you to
scan/digitize three-dimensionals objects.
www.david-laserscanner.com
If you don't like reading manuals...
Sorry, our software cannot automatically adapt to your environment; it needs
your help. That's why you should read the manual or at least the
following 5 hints:
-
The background structure "Calibration Corner" must have an exact 90° angle.
-
Switch off all automatic image enhancements (like
auto-exposure, auto-gain, auto-white-balance, ...)
-
During camera calibration, the image (i.e. the
exposure and/or aperture settings and/or the ambient light) must be quite
bright, so that the camera image looks ideally like this:

-
During scanning, the image (i.e. the exposure
and aperture settings and the ambient light) must be very dark.
To obtain suitable settings, you should watch the live camera image with
the laser line visible, and adjust the settings so that the laser
line is clearly visible in the image while the rest of
the image is as dark as possible (possibly totally
black), like here:

-
You must hold the laser rather "high", i.e. the distance
between the laser light plane and the camera must not be too small. Otherwise
you will get the error message "INTERSECTION ANGLE TOO LOW!"
Those were most critical reasons why our "impatient" beta testers
were not immediately successful. But there are more things you have to know
about, so you really should consider reading the manual. Especially if your
scanning results are not as beautiful as our screenshots. The manual is
not too long... :-)
Introduction
Many approaches for contact-free measurement techniques for
object surfaces and approaches for 3d object reconstruction have been proposed;
but often they require complex and expensive equipment. Not least due to the
rapidly increasing number of efficient 3d hard- and software system components,
alternative low-cost solutions are in great demand. DAVID is such a low-cost
system for 3d data acquisition. The only hardware requirements are a simple
commercial hand-held laser and a webcam or a standard grayscale camera.
Hardware Requirements
PC:
....with Windows 2000/XP and Microsoft .NET
Framework 2.0
Laser:
Any light source that creates a very thin but bright light plane. A
10-Euro Laser-Level from a home improvement store will be sufficient in
many cases. We did most experiments with a laser diode equipped with a
cylendrical lens.
Camera:
Although the scanner will work with a cheap webcam, of course
you will obtain better results with high quality cameras. Color is only
necessary if you want to get a colored texture. Otherwise, you may even
get better results with a grayscale camera. The camera MUST come with WDM drivers.
Calibration Corner:
You need a Calibration Corner for calibration of the camera and as background
structure during scanning. It must consist of two plain walls / boards which
stand in an angle of exactly 90°. For camera calibration, we provide a
calibration pattern for download which you should glue onto the walls / boards.
Construction Manual
The following steps show how you can build your Calibration Corner.
This example consists of two white flat plastic boards, some adhesive
tape, and a printout of the calibration pattern (choose from
the Calibpoints... .pdf files that came with the DAVID software).
Theoretically, you can print the pattern scaled up or down to any size.

You should measure and remember the "scale" length on the
printout because you will need it during camera calibration.

Cut the printout at the thin line marked with a scissors symbol very
precisely. In the end, it is very important that the cut edges
of the two parts precisely touch each other.

Stick the printouts to the boards so that, when the board will be set up in a
90° angle, the cut edges precisely touch each other.


Use any precisely rectangular object to set up the two boards in a precise
90° angle. The parts of the gray coordinate system in the
lower corner must fit together perfectly! The double marker
must be in the lower right corner of the pattern (from the
camera's point of view)!
!!! These requirements must be met during camera calibration and scanning
!!!

You should glue the boards together using adhesive tape, or better, using
angle brackets and screws.


Using Your Room's Walls
Alternatively, you can simply use the corner of a room as long as the walls
are plain, have a precise 90° angle, and allow you to attach the calibration
pattern printout(s) so that the cut edges fit together perfectly. Remember that
the double marker in the calibration pattern must be in the lower right corner
(of the camera image).
Table of Contents
-
Welcome to DAVID (help_welcome.htm)
-
Camera Calibration (help_camera_calibration.htm)
-
3D Laser Scanning (help_3d_scanning.htm)
-
Shape Fusion (help_shape_fusion.htm)
-
Frequently Asked Questions (help_faq.htm)
-
General Hints (help_hints.htm)