Usually people would like to choose visible beam red, blue, blue violet, or green color laser alignment to make line projection. Any of these alignment lasers is able to project highly visible and bright reference line on required surfaces. In special operating field, people need to use invisible beam line infrared laser alignment for line presentation. This type of special light emitting source infrared laser alignment is commonly used in military targeting fields. For instance, it can be mounted on telescope, night vision laser illuminator or other military weapons. The special infrared laser light source is always able to conduct solider to make accurate projection and positioning on required places secretly. No matter at what kind of operating occasions, users should remember to choose the most appropriate laser alignment with suitable wavelength, output power so as to get ideal line generation successfully. In addition, users should be always acknowledgeable with exact line length, line width and operating distance. The selection of correct laser line degree has made the most accurate line projection for users on all targeting fields successfully.