According to this documentation: http://docs.opencv.org/modules/calib3d/doc/camera_calibration_and_3d_reconstruction.html
I've obtained m', A, and [R|t]. And then I want to find M'. But I have no idea to find s value, which is a scaling factor. I only can measure distance from camera to target object using a ruler.
Please tell me how to find s value using depth information.