1. Getting Started
2. Camera Calibration
3. 3D Laser Scanning
4. Shape Fusion
5. Frequently Asked Questions
6. General Hints

(Left: New “V3” calibration pattern. Right: Old calibration pattern.)

Note: This manual refers to the new “V3” calibration pattern (with 70 markers). If you are using the old pattern (25 markers), steps 4 and 5 are different, please read the old version of this page. The DAVID software will recognize automatically which pattern you are using.

Before you can scan objects, you have to calibrate the camera. This determines the position and orientation of the camera in 3D space and its internal parameters (focal length, lens distortion). The following steps will guide you through the camera calibration dialog of DAVID:

1. Make sure that the camera is connected to the PC and that the camera drivers are installed. Your camera must support WDM Video Capture Driver (i.e. DirectShow-Driver) for Windows.
2. Click on the upper rollout-box and choose your camera device. If your camera is not listed, try to reconnect it and open the rollout-box again. After you have chosen a camera device, you will be asked whether you want to allow DAVID to read and write camera parameters (description). This function greatly enhances comfort by remembering and switching between different camera settings for calibbration, scanning, and texture grabbing. Therefore it should be switched on - unless problems appear. Finally, a new window with a camera live view appears.
3. If the standard image format (e.g. resolution or frames per second (fps)) does not match your requirements, you can change the image format by pressing the “Change Format” button. In your first trials, you should choose a medium resolution (e.g. 640*480 or 800*600) and then set the highest available frame rate (typically 30 fps).
4. Place your camera in front of the calibration corner (see here for a construction manual), in such a way that the calibration pattern completely fills the camera image. The camera should not be able to see past the calibration panels. The camera need not see all markers, but must see at least the 6 ring markers and some dot markers around them. The automatic camera calibration approach needs an image with a rather high contrast. (Usually the calibration points are black and the background is white. If you have bright points on dark background, check the “Inverted printout” option.) To get an adequate image brightness, you can switch on some light or adjust the camera settings: Pressing the “Camera Settings” button and increase e.g. Exposure, Gain, Contrast, Brightness. Besides the calibration markers, there should not be any too dark objects (image areas) in the camera image!
   Now your camera image should look like one of these:
   
   Good average camera image for calibration.
   
   
   Also a good camera image for calibration - the camera is rather far away, and the illumination is quite low.
   
   
   Also a good camera image for calibration - the camera is standing very close, and the illumination is quite high.
   
   
   Bad camera image! Much too dark, and the pattern is too small / the camera is standing too far away. Calibration won't succeed.
   
   Usually you can skip step 5.
   
5. a) OPTIONAL: Use the Eraser to improve your calibration image. If the calibration fails in automatic mode, look at the error message. Often DAVID has found too many markers. You can easily help DAVID by selecting the “Eraser” calibration mode. The “size” refers to the size of the rectangular mouse eraser. Use your left mouse button to “clean” the camera image from false markers (dark image areas). You can “unerase” with the right mouse button. The following screenshots show a not-optimal calibration image where the user has erased dark areas (bright white):
   
   
   b) ADVANCED: Manual calibration mode
   Manual calibration mode is not possible with the new “V3” pattern! It's not recommendable anyway.
   
   
6. Make sure that the scale of your printed calibration pattern is correct. Measure the scale length of your printout and enter the value in mm into the input field labeled “Scale (mm)”.
   
   
7. Press the “Calibrate Camera” button. If the camera calibration is successful, you should see small red crosses in the live image, which mark the centers of the calibration points:
   
   If the calibration failed, first try to readjust the camera image (aperture, exposure time, light conditions) according to step 4. Use the Eraser Mode to clean “dirty” areas if necessary, so that the calibration markers are the only dark image elements (step 5).
8. Press “Next” button to enter the scanning dialog.

1. Getting Started
2. Camera Calibration
3. 3D Laser Scanning
4. Shape Fusion
5. Frequently Asked Questions
6. General Hints