what's the corresponding theory formula about the function of estimateMo​noCameraPa​rameters

Hi, when i reading the source code of the function of estimateMonoCameraParameters as follows, i cann't understand the process of implementation.

If someone knows the corresponding theory formula, please give me a hint. I will appreciate it!

[rotationMatrix, translationVector] = extrinsics(imagePoints, worldPoints, intrinsics);

% Compute camera pose in the world coordinate system defined by the board.
orientation = rotationMatrix';
location    = -translationVector * rotationMatrix';

isPatternHorizontal = strcmpi(patternOrientation, 'horizontal');

% Rotate the world coordinate sytem attached to the board so that X-axis
% points to the right side of the vehicle.
R = getXAxisRotationMatrix(pattternPosition, isPatternHorizontal);

% Adjust camera position in the new world coordinate sytem.
location = R * location(:);
orientation = orientation * R';

% Rotate the world coordinate sytem attached to the board so that Z-axis
% points up.
R = getZAxisRotationMatrix(isPatternHorizontal);

% Adjust camera position in the new world coordinate sytem.
location = R * location(:);
orientation = orientation * R';

% Rotate 90 degrees around z.
R = [0 1 0; -1 0 0; 0 0 1];
orientation = orientation * R';

% Decompose the rotation matrix into Euler angles.
% This is the inverse operation of the transformation defined in
% monoCamera.rotationMatrix()
R = [0 -1 0; -1 0 0; 0 0 -1] * orientation';





%==========================================================================
function R = getZAxisRotationMatrix(isPatternHorizontal)
if isPatternHorizontal
    % Flip Y and Z axis.
    R = [1 0 0; 0 -1 0; 0 0 -1]; 
else
    % Rotate -90 degrees around x.
    R = [1 0 0; 0 0 1; 0 -1 0];
end

%==========================================================================
function R = getXAxisRotationMatrix(pattternPosition, isPatternHorizontal)
if strcmpi(pattternPosition, 'front')
    R = [1 0 0; 0 1 0; 0 0 1];
elseif strcmpi(pattternPosition, 'back')
    if isPatternHorizontal
        R = [-1 0 0; 0 -1 0; 0 0 1];
    else
        R = [-1 0 0; 0 1 0; 0 0 -1];
    end
elseif strcmpi(pattternPosition, 'left')
    if isPatternHorizontal
        R = [0 1 0; -1 0 0; 0 0 1];
    else
        R = [0 0 -1; 0 1 0; 1 0 0];
    end
elseif strcmpi(pattternPosition, 'right')
    if isPatternHorizontal
        R = [0 -1 0; 1 0 0; 0 0 1];
    else
        R = [0 0 1; 0 1 0; -1 0 0];
    end
end

[Mochammad Habibi]

Hi, Have you found any answer? Can we discuss it please? Thank you so much!