DUO Calibration

Overview

In this article we review how to use our Calibration App to capture calibration frames, perform calibration and save the results to the device. Below we go through the steps of getting a proper calibration and testing. A proper calibration is critical stereo vision algorithms, make sure to follow the steps below to assure you get best results. Also make sure you have the latest DUO Software from our downloads page.

Prerequisites

Calibration Pattern

  • DUO Calibration Squares - A standard pattern for use in the calibration process can be downloaded here.

Calibration App

The Calibration application provides a process for calibrating the images using a 9x9 grid that is included in the SDK. You can find a file called DUOCalibrationGrid.pdf in the Dashboard/Calibration folder. Alternatively you can download the PDF from the web. To calibrate you will need to print this grid pattern and put it on a stable surface.

Calibration Steps

  • Step 1 - Print the DUO Calibration Grid and attach to a flat/stable surface.
  • Step 2 - Start the DUO Dashboard application and switch to the Calibration App.
  • Step 3 - Setup your scene so the Calibration Grid is clearly visible and well illuminated.
  • Step 4 - Click the Start Capture button to begin capturing. If needed use the Clear Frames button.
  • Step 5 - Capture will automatically stop based on the current value of the Frame Count parameter.
  • Step 6 - Review each frame and verify proper point matches. If a frame is bad simply click on it to ignore.
  • Step 7 - Click the Start Calibration button and you should see the results of the process after.

* Tip - If you use more frames you can achieve higher accuracy.

You can toggle the Show Epipoles option to give you a comparison of the two cameras, also the Show Calibrated option will toggle in between processed and non-processed image data. After a successful calibration you should see the following files created in the Dashboard/Calibration folder:

  • stereo_R[CURRENT_WIDTH]x[CURRENT_HEIGHT]_[CURRENT_BINNING].yml
  • extrinsics_R[CURRENT_WIDTH]x[CURRENT_HEIGHT]_CURRENT_BINNING.yml
  • intrinsics_R[CURRENT_WIDTH]x[CURRENT_HEIGHT]_CURRENT_BINNING.yml
  • rectifyMap_R[CURRENT_WIDTH]x[CURRENT_HEIGHT]_CURRENT_BINNING.yml
Note: The exact file name may vary dependent on resolution you calibrated at, each resolution requires its own settings.

The following parameters are used in the calibration process:

  • Frame Count - The amount of frames to capture for the calibration process.
  • Show Calibrated - True/False toggle for displaying calibrated or not calibrated image data.
  • Show Epipoles - True/False option for showing debug for the Epipolar geometry.

Also these specific actions are exposed:

  • Start Capture - Begins the capturing of frames for use in the calibration process.
  • Stop Capture - Ends the capturing of frames for use in the calibration process.
  • Clear Capture - Removes all frames previously captured into the frame queue.
  • Start Calibration - After capturing and reviewing your frames you can run the calibration.

Resources

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