Where is the origin of the coordinate systems in the camera?

I want to get real-world position and dimensions of an object (along 3 axes: x, y and z) from the camera and I guess I should use the values of “point_cloud” for this purpose.
But I do not know where the origin of the coordinate system is for the x and y axes. and also, the direction of these axes is not clear to me.
I would appreciate if you could help me

Hi @Mahdie
the documentation contains all the information you need: