Camera Calibration (USB)

1. Install Plugins

Install Image Calibration Tool

sudo apt install ros-${ROS_DISTRO}-image-pipeline -y

Install Official USB Camera Tool

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sudo apt install ros-${ROS_DISTRO}-usb-cam -y

2. Start the Camera

Restart the terminal, re-enable the ROS environment, and then run the following command to start the USB camera node.

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ros2 run usb_cam usb_cam_node_exe

Open another terminal and launch rqt:

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rqt

3. Image Calibration

3.1. Calibration Board

3.2. Viewing Topics and Services

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ros2 topic list
ros2 service list

3.3. Image Calibration

Launch the Image Calibration Tool

Launch the ROS 2 camera calibration tool, camera_calibration, to perform the camera calibration. Note: The camera must be started before running the calibration tool.

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ros2 run camera_calibration cameracalibrator --size 9x6 --square 0.02 --ros-args --remap /image:=/image_raw --remap camera/set_camera_info:=usb_cam/set_camera_info

Parameter Explanation

--size: The number of internal corners on the chessboard pattern → 9 rows by 6 columns of internal corners.

--square: The side length of each square on the chessboard pattern → 0.02 meters

--ros-args: Pass ROS arguments

--remap: Topic remapping → /image_raw serves as the image input stream

Calibration Process

Parameter Descriptions

X: Move the chessboard left and right within the camera's field of view

Y: Move the chessboard up and down within the camera's field of view

Size: Move the chessboard forward and backward within the camera's field of view

Skew: Tilt and rotate the chessboard within the camera's field of view

When X, Y, Size, and Skew turn green, you can click CALIBRATE to compute the camera's intrinsic parameters. Note: The more images used for calibration, the longer the process will take, and there is a possibility that the program may freeze.

Once calibration is complete, click SAVE to save the results!

Close the program after the results have been successfully saved! Calibration Results

Default save location and filename for the calibration results:

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/tmp/calibrationdata.tar.gz

Copy and extract the calibration results:

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sudo mv /tmp/calibrationdata.tar.gz ~
mkdir calibrationdata
tar -xzvf calibrationdata.tar.gz -C ~/calibrationdata

The extracted files include the calibration *.png, ost.yaml, and ost.txt files. We will primarily copy the data contained within the ost.yaml file into the camera_usb.yaml file.

ost.yaml

Replace the corresponding data in the camera_usb.yaml file with the values ​​for image_width, image_height, the data field within camera_matrix, the data field within projection_matrix, and the data field within distortion_coefficients.

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image_width: 1280
image_height: 800
camera_name: narrow_stereo
camera_matrix:
  rows: 3
  cols: 3
  data: [2126.24686,    0.     , 1045.90416,
            0.     , 2038.73134,  292.1827 ,
            0.     ,    0.     ,    1.     ]
distortion_model: plumb_bob
distortion_coefficients:
  rows: 1
  cols: 5
  data: [0.618718, -0.496057, -0.038096, 0.134905, 0.000000]
rectification_matrix:
  rows: 3
  cols: 3
  data: [1., 0., 0.,
         0., 1., 0.,
         0., 0., 1.]
projection_matrix:
  rows: 3
  cols: 4
  data: [2049.23772,    0.     , 1082.02717,    0.     ,
            0.     , 2153.52835,  282.33049,    0.     ,
            0.     ,    0.     ,    1.     ,    0.     ]

camera_usb.yaml

Modified File:

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%YAML:1.0
---
image_width: 1920
image_height: 1080
camera_name: camera
camera_matrix: !!opencv-matrix
  rows: 3
  cols: 3
  dt: d
  data: [2126.24686,    0.     , 1045.90416,
            0.     , 2038.73134,  292.1827 ,
            0.     ,    0.     ,    1.     ]
distortion_model: plumb_bob
distortion_coefficients: !!opencv-matrix
  rows: 1
  cols: 5
  dt: d
  data: [0.618718, -0.496057, -0.038096, 0.134905, 0.000000]
rectification_matrix:
  rows: 3
  cols: 3
  data: [1., 0., 0.,
         0., 1., 0.,
         0., 0., 1.]
projection_matrix:
  rows: 3
  cols: 4
  data: [2049.23772,    0.     , 1082.02717,    0.     ,
            0.     , 2153.52835,  282.33049,    0.     ,
            0.     ,    0.     ,    1.     ,    0.     ]