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    Why does my stereo calibration fails for extrinsics?

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    • D
      Darshit Desai
      last edited by Darshit Desai 4 May 2023, 19:55 4 May 2023, 19:54

      I am using the modal ai portal for calibration of onboard stereo cameras but it has failed to calibrate the extrinsics multiple times.

      The board size is 6x9 with each square of 25 mm

      Please open voxl-portal in a web browser to view the camera calibrator overlay stream
      Calibrating Left Camera
      Matrix
      [508.80440670594, 0, 308.5135447003642;
       0, 505.8572996337453, 244.1641938401985;
       0, 0, 1]
      Distortion
      [-0.1811268882769062;
       0.07256140246308232;
       0.001569367963422894;
       -0.001895561795494848;
       0]
      distortion_model: plumb_bob
      Re-projection error reported by calibrateCamera: 0.228868
      Calibration Succeded!
      Calibrating Right Camera
      Matrix
      [499.3757621172282, 0, 325.48861203442;
       0, 497.8217173811094, 235.3877218749848;
       0, 0, 1]
      Distortion
      [-0.1815603484893367;
       0.06567294535447908;
       -0.001628603839397166;
       0.001644475509575583;
       0]
      distortion_model: plumb_bob
      Re-projection error reported by calibrateCamera: 0.219737
      Calibration Succeded!
      Calibrating Extrinsics
      4 frames will be processed
      R
      [0.9998749556474266, -0.01520329924164708, 0.004351179291381281;
       0.01514403461767066, 0.9997962803983895, 0.01334375947938024;
       -0.004553162039243111, -0.01327619650779887, 0.9999015008098201]
      T
      [-0.08098804070286524;
       -0.000892545176548338;
       -0.003303076144588922]
      Re-projection error reported by stereoCalibrate: 0.832656
      Detected horizontal stereo pair
      Distance between cameras: 0.0810
      Extrinsics Calibration Failed
      exceeded allowable max reprojection error:  0.5
      
      Saved intrinsics to: /data/modalai/opencv_stereo_intrinsics.yml
      Exiting Cleanly
      
      1 Reply Last reply Reply Quote 0
      • C
        Chad Sweet ModalAI Team
        last edited by 4 May 2023, 20:31

        Can you take a picture of your setup?

        Are the image sensors mounted rigidly on the same plane?

        D 1 Reply Last reply 5 May 2023, 17:37 Reply Quote 0
        • D
          Darshit Desai
          last edited by 5 May 2023, 02:05

          This post is deleted!
          1 Reply Last reply Reply Quote 0
          • D
            Darshit Desai @Chad Sweet
            last edited by 5 May 2023, 17:37

            @Chad-Sweet I am not sure about the plane of the camera. I am attaching some photos for your reference

            https://drive.google.com/drive/folders/1nJOy9G0-hZSNSN0kZyrtJ9HcxRaZa50X?usp=share_link

            A 1 Reply Last reply 5 Sept 2023, 15:48 Reply Quote 0
            • A
              afdrus @Darshit Desai
              last edited by 5 Sept 2023, 15:48

              @Chad-Sweet I am also facing the same issue, it is unclear from the documentation what is the procedure that should be followed to calibrate the extrinsics. Should the board be tilted? Should it be vertical or horizontal?

              M 1 Reply Last reply 5 Sept 2023, 19:01 Reply Quote 0
              • M
                Moderator ModalAI Team @afdrus
                last edited by 5 Sept 2023, 19:01

                @afdrus have you watched the video here found at this link? https://docs.modalai.com/calibrate-cameras/#stereo-calibration-process

                The angle of the PCB is not related to stereo calibration. For stereo configuration, the sensors must be rigidly mounted and coplanar. Any movement or tilt between the sensors will not work

                A 1 Reply Last reply 6 Sept 2023, 07:41 Reply Quote 0
                • A
                  afdrus @Moderator
                  last edited by 6 Sept 2023, 07:41

                  @Moderator thank you for the reply, by board I meant the checkboard used for the calibration not the PCB.

                  However, I watched the video, but it looks old because the current extrinsics procedure is asking me to move the checkboard in 4 poses whereas the video is showing only 2 poses. How much tilt should the checkboard have during the extrinsics calibration process in order to have a low calibration error?

                  1 Reply Last reply Reply Quote 1
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