ZED OpenCV Calibration

A stereo camera calibration toolkit for ZED cameras using OpenCV.

Overview

This project provides two main applications for working with ZED cameras:

1. Stereo Calibration Tool - Interactive calibration data acquisition and processing
2. Reprojection Viewer - Real-time reprojection tool to visualize calibration on unrectified images

Requirements

Dependencies

• ZED SDK (version 5.1 or higher)
• OpenCV (4.x recommended)
• CUDA (compatible with ZED SDK version)
• OpenGL libraries:
  • GLEW
  • FreeGLUT
  • OpenGL
• CMake (3.5 or higher)
• C++17 compatible compiler

Installation

git clone https://github.com/stereolabs/zed-opencv-calibration.git
cd zed-opencv-calibration

# Build stereo calibration tool
cd stereo_calibration
mkdir build && cd build
cmake ..
make -j$(nproc)

# Build reprojection viewer
cd ../../reprojection_viewer
mkdir build && cd build
cmake ..
make -j$(nproc)

Usage

Stereo Calibration

The calibration process requires a printed checkerboard pattern.

Default configuration expects a 9x6 checkerboard with 24mm squares. For other configurations, please update the checkerboard description in the code directly.

Prepare Calibration Target

• Print a checkerboard pattern on rigid, flat surface
• Default: 9 horizontal × 6 vertical inner corners, 24mm square size
• Ensure the pattern is perfectly flat and well-lit

Run Calibration

cd stereo_calibration/build
./ZED_Opencv_Calibration [options]

Options:

• --svo <file> - Use SVO file instead of live camera
• --fisheye - Use fisheye distortion model (default: RadTan)
• --help - Show help message

Calibration Process

1. Coverage Phase: Move the checkerboard to cover different areas of the image

   • Green areas indicate sufficient coverage
   • Press 's' to capture frames when checkerboard is detected

2. Rotation Phase: Rotate the checkerboard in different orientations

   • Achieve >60° rotation in X, Y axes and >60° distance variation
   • Avoid rotating >45° around Z-axis
   • Progress indicators show completion percentage

3. Completion: Calibration runs automatically when sufficient data is collected

   • Minimum 15 images required
   • Calibration file saved as zed_calibration_[serial].yml

Reprojection Viewer

Visualize the rectification of the image on the full

cd reprojection_viewer/build
./ZED_Depth_Repro [options]

Configuration

Calibration Parameters

Edit the following constants in stereo_calibration/src/main.cpp:

constexpr int target_w = 9;        // Horizontal inner corners
constexpr int target_h = 6;        // Vertical inner corners  
constexpr float square_size = 24.0; // Square size in mm

Quality Thresholds

const float min_coverage = 10;      // Coverage percentage
const float min_rotation = 60;      // Rotation in degrees
const float min_distance = 200;     // Distance variation in mm

Advanced Features

Virtual Stereo Camera Support

Configure multiple ZED One cameras as a virtual stereo pair:

// In stereo_calibration/src/main.cpp
if(1){ // Enable virtual stereo
    const int sn_left = 300000001;   // Serial number of left camera
    const int sn_right = 300000002;  // Serial number of right camera
    int sn_stereo = sl::generateVirtualStereoSerialNumber(sn_left, sn_right);
    init_params.input.setVirtualStereoFromSerialNumbers(sn_left, sn_right, sn_stereo);
}

Fisheye Camera Support

For wide-angle or fisheye lenses:

./ZED_Opencv_Calibration --fisheye