An edge inspection method for detecting defects on a wafer edge normal surface includes acquiring a set of digital images which captures a circumference of the wafer. In example embodiments, a computing device may determine a number of occurrences of a word in a particular document and may then determine a weight of meaningfulness for the word based on the number of occurrences. The reference marks are formed simultaneously with corresponding electrical connecting portions via a mask, such that in order to accurately position the electrical connecting portions, it is only necessary to accurately relatively position the reference marks. 0, where f1 is a focal length of the first lens, f is an effective focal length of the second lens, the lens group and the third lens. Responsive to the condition, a portion of the code which corresponds to the detected condition is identified.