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1. Coordinate relationship
There are four coordinate systems in the camera, namely world, camera, image, pixel
- world is the world coordinate system. You can specify the xw axis and ywaxis arbitrarily, which is the coordinate system where point P in the above picture is located.
- camera is the camera coordinate system, the origin is at the small hole, the z-axis coincides with the optical axis, the xw-axis and the yw-axis are parallel to the projection plane, which is the coordinate system XcYcZc in the above figure.
- image is the image coordinate system. The origin is located at the intersection of the optical axis and the projection surface. The xw axis and the yw axis are parallel to the projection surface, which is the XYZ coordinate system in the above figure.
- Pixel is the pixel coordinate system. Looking from the small hole to the projection surface, the upper left corner of the projection surface is the origin. The uv axis coincides with both sides of the projection surface. This coordinate system is on the same plane as the image coordinate system, but the origin is different.
2. Coordinate transformation
The following formula is the transformation formula between pixel coordinate pixel and world coordinate world. The first matrix on the right is the camera internal parameter.