# Table of Contents

1. Welcome to DAVID (help_welcome.htm)
2. Camera Calibration (help_camera_calibration.htm)
3. 3D Laser Scanning (help_3d_scanning.htm)
4. Shape Fusion (help_shape_fusion.htm)
5. Frequently Asked Questions (help_faq.htm)
6. 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

1. Welcome to DAVID (help_welcome.htm)
2. Camera Calibration (help_camera_calibration.htm)
3. 3D Laser Scanning (help_3d_scanning.htm)
4. Shape Fusion (help_shape_fusion.htm)
5. Frequently Asked Questions (help_faq.htm)
6. General Hints (help_hints.htm)