1. A computer-based method for correcting an image of a physical object, the method comprising: controlling movement of a charge coupled device (CCD) comprising a lens positioned on a Z-axis of a measurement machine to focus on a circle of a calibration plate of the measurement machine, and enable the CCD to capture a first image of the circle; determining an original scaling of the lens using the circle and the first image of the circle; controlling movement of the Z-axis of the measurement machine to enable the lens to focus on a rectangle set of the calibration plate, and enable the CCD to capture images of the rectangle set; determining correction data according to the original scaling of the lens using the images of the rectangle set, wherein the correction data comprises a first correction data, a second correction data, and a third correction data; controlling movement of the Z-axis of the measurement machine to enable the lens to focus on the circle of the calibration plate again, and enable the CCD to capture a second image of the circle; determining an accurate scaling of the lens according to the correction data using the circle and the second image of the circle; correcting the image of the physical object according to the correction data and the accurate scaling of the lens; and displaying a corrected image of the physical object on a monitor.