Lasers and laser systems are becoming quite common in today’s high-technology society. There are lasers for welding and machining and there are lasers for accurate meas- urement of distance and alignment of equipment. Lasers are used in mining and stress analysis and in holographic devices at grocery checkouts, and they have many medical applications. There are laser pointers for lectures and presentation. The military uses lasers in weapon systems to measure distance to targets or in guidance.