What are the intrinsic camera parameters for the Orbbec Astra Mini?

Technical Support & Q&A
2

Hi. I am currently working with the Astra Mini depth sensor and experimenting with ORB SLAM 2.

ORB SLAM 2 features a settings file called TUM.yaml and it has the following content:

%YAML:1.0

#--------------------------------------------------------------------------------------------
# Camera Parameters. Adjust them!
#--------------------------------------------------------------------------------------------

# Camera calibration and distortion parameters (OpenCV) 
Camera.fx: 535.4
Camera.fy: 539.2
Camera.cx: 320.1
Camera.cy: 247.6

Camera.k1: 0.0
Camera.k2: 0.0
Camera.p1: 0.0
Camera.p2: 0.0

Camera.width: 640
Camera.height: 480

# Camera frames per second 
Camera.fps: 30.0

# IR projector baseline times fx (aprox.)
Camera.bf: 40.0

# Color order of the images (0: BGR, 1: RGB. It is ignored if images are grayscale)
Camera.RGB: 1

# Close/Far threshold. Baseline times.
ThDepth: 40.0

# Deptmap values factor
DepthMapFactor: 5000.0

Especially I am looking for the intrinsic camera parameters; the focal length (fx, fy) and the optical centers (cx, cy).

I guess I need to calibrate my camera myself in order to get the k1, k2, p1 and p2 parameters; is that correct?

Please could somebody point out the correct settings for the Orbbec Astra Mini depth sensor ?

UPDATE 18th April 2018

I meanwhile followed the calibration procedure contained in the calibration package available here.

Here are the results:

[Left Camera Intrinsic]
578.457       0 346.077
      0 571.928 250.389
      0       0       1
[Right Camera Intrinsic]
517.723       0 337.738
      0 512.275 242.524
      0       0       1
[Right to Left Camera Rotate Matrix]
   0.999841 -0.00841257   0.0157468
 0.00861483    0.999881  -0.0128205
  -0.015637   0.0129542    0.999794
[Right to Left Camera Translate]
-24.8819 0.138074 -0.203578

With the help of this tutorial and the depicted matrix, I can extract the fx, fy, cx and cy values for the left and right camera (left camera is the IR camera and right camera is RGB camera).

But how do I have to apply these values to my YAML file? Within the YAML file, there’s only 1x {fx, fy, cx, cy} values to be defined:

# Camera calibration and distortion parameters (OpenCV) 
Camera.fx: 535.4
Camera.fy: 539.2
Camera.cx: 320.1
Camera.cy: 247.6

Camera.k1: 0.0
Camera.k2: 0.0
Camera.p1: 0.0
Camera.p2: 0.0

Shouldn’t there be Camera.fx/.fy/.cx/.cy for both cameras?

Moreover, how do I have to extract the k1/k2/p1/p2/p3 parameters from the matrix I got from the calibration process (depicted above) ?

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