The calibration of the camera is a one time process but it is also one of the most important processes to get the highest accuracy from Dragonfly. It allows to create a calibration file that encodes the distortion parameters of the camera optics. These distortion parameters are a function of the manual assembly process of the camera optics and of any enclosure used to protect the camera. The calibration file is used by Dragonfly to “normalize” the wide-angle images collected by the camera.

1 – Preliminary steps

1. Launch Dragonfly and connect your monocular camera (following the information of the left menu).
2. Click on the Three lines button and then on the Calibrate camera button.
3. Type the calibration File name using a meaningful name (e.g. 180_Low_Illumination_Camera.737z)
4. Download your favorite calibration pattern from this link:
   • CHESSBOARD grid
   • CIRCLES grid
   • ASYMMETRIC CIRCLES grid
5. Print the calibration pattern on a A4 or Letter paper with no margin and place it on a plain surface.
   • Do not perform the calibration if the calibration pattern printed is wavy because you won’t be able to perform a good calibration and Dragonfly won’t produce accurate results!
6. Measure the distance in millimeters (NO inches and NO centimeters!) of the HDIST line visible inside the calibration pattern.
7. Enter the distance just measured inside the field HDIST.
8. Select the Mode that you would like to use for the calibration process.
   • free auto mode – allows to perform the calibration process by pointing a calibration pattern from the angles chosen by the users. The poses used for the calibration will be AUTOMATICALLY collected by Dragonfly every 1 second.
   • free mode – allows to perform the calibration process by pointing a calibration pattern from the angles chosen by the users. The poses used for the calibration will be collected by Dragonfly after having clicked on a button of the GUI.
   • assisted mode – guides you through the calibration process thanks to a set of pulsating color patterns that are over imposed on the video stream in order to show you the poses to be used to frame the printed calibration pattern.
9. Inside the Distortion model field choose:
   • Wide Fov – if you are working with a 170° camera.
   • Fisheye 4 distortion coeff – if you are working with a 180° camera.
   • Fisheye 6 distortion coeff – if you are working with a 180° camera and you want to generate a calibration file that is compatible with the legacy Dragonfly 2 (be aware that the accuracy of this file is lower than the one generated with 4 distortion coeff).
10. Inside the Board pattern select the calibration pattern that has been printed.

2 – Calibration steps

2.1 – Free-auto mode

The free auto mode allows to perform the calibration process by pointing a calibration pattern from the angles chosen by the users. The poses used for the calibration will be AUTOMATICALLY collected by Dragonfly every 1 second.

1. Click on Start calibration.
2. Now you just have to point the camera towards the calibration pattern until you should see the black dots/squares being connected by colored lines. The first pose will be AUTOMATICALLY captured by Dragonfly (and you will see the taken image count counter growing).
   • Please make sure that the camera and the pattern are close. Otherwise the calibration result won’t be usable!
3. Now you have to move the camera and point the calibration pattern from a different angle every 1 second so that Dragonfly can capture all the other poses.
4. Dragonfly will collect a total of 21 poses or 28 poses depending on the distortion model chosen.
5. After you have collected all the poses, the Dragonfly App will automatically start the computation of the calibration parameters of your camera.
   • It should take few seconds and the calibration file will be automatically saved inside the configuration folder of the Dragonfly App.
   • If you see a black screen instead of the video feed coming from your camera, then there are chances that the calibration process did not produce a good calibration file. In this case you just have to repeat the calibration process.
6. Click on the Set as default button to exit the calibration process and automatically set the new calibration file as default file to be loaded or click on the STOP button to exist the calibration process.

2.2 – Free mode

The free mode allows to perform the calibration process by pointing a calibration pattern from the angles chosen by the users. The poses used for the calibration will be collected by Dragonfly after having clicked on a button of the GUI.

1. Click on Start calibration.
2. Now you just have to point the camera towards the calibration pattern until you should see the black dots/squares being connected by colored lines. When this happens click on the camera button to capture the pose and you will see the taken image count counter growing.
   • Please make sure that the camera and the pattern are close. Otherwise the calibration result won’t be usable! 
3. Now you can move the camera and point the calibration pattern from another angle.
4. You will have to collect a total of 21 poses or 28 poses depending on the distortion model chosen.
5. After you have collected all the poses, the Dragonfly App will automatically start the computation of the calibration parameters of your camera.
   • It should take few seconds and the calibration file will be automatically saved inside the configuration folder of the Dragonfly App.
   • If you see a black screen instead of the video feed coming from your camera, then there are chances that the calibration process did not produce a good calibration file. In this case you just have to repeat the calibration process.
6. Click on the Set as default button to exit the calibration process and automatically set the new calibration file as default file to be loaded or click on the STOP button to exist the calibration process.

2.3 – Assisted mode

The assisted mode guides you through the calibration process thanks to a set of pulsating color patterns that are over imposed on the video stream in order to show you the poses to be used to frame the printed calibration pattern.

1. Click on Start calibration.
2. Dragonfly will present you with a  pulsating color pattern overlay, surrounded by a black frame with a positioning indicator in the corner, and a dynamic green indicator bar below.
3. If you point the camera to the calibration pattern, you should see the black dots being connected by colored lines.
4. The objective is now to match the pattern displayed inside the preview window with your calibration pattern printed. Once there is a match the snapshots are made automatically.
   • Please make sure that the camera and the pattern are close. Otherwise the calibration result won’t be usable!
5. The server will present between 21 poses or 28 poses depending on the distortion model chosen.
6. After you have collected all the poses, the Dragonfly App will automatically start the computation of the calibration parameters of your camera.
   • It should take few seconds and the calibration file will be automatically saved inside the configuration folder of the Dragonfly App.
   • If you see a black screen instead of the video feed coming from your camera, then there are chances that the calibration process did not produce a good calibration file. In this case you just have to repeat the calibration process.
7. Click on the Set as default button to exit the calibration process and automatically set the new calibration file as default file to be loaded or click on the STOP button to exist the calibration process.

3 – Verify the calibration quality

To verify the calibration quality please:

1. Click on the Three lines button and then on the Camera settings button.
2. Check if the calibration file just computed is shown inside the Calibration file path field.
3. Now point the camera towards a square or rectangular shape and verify that the lines/shapes that are straight on the square/rectangular shape are also straight inside the video preview.
   • If this is the case then the calibration computed is good.
   • If this is NOT the case then it might be that something went wrong during the calibration process. Please repeat the calibration process and make sure to select:
     • Wide Fov – if you are working with a 170° camera.
     • Fisheye 4 distortion coeff – if you are working with a 180° camera.
     • Fisheye 6 distortion coeff – if you are working with a 180° camera and you want to generate a calibration file that is compatible with the legacy Dragonfly 2