Similarly a line of laser light projected onto wood can show a saw operator where the cut will occur in the material. Holography is the production of a 3D photograph using a laser as the source of illumination. Holographic images can be artistic as well as practical allowing the study of fragile objects which can not withstand repeated handling. Holograms can also be used for vibration and stress analysis allowing the detection of hidden defects in materials such as aircraft parts long before they become a problem. Commercial aircraft tires and high performance automotive tires are tested this way.
Lasers allow for light wave communications.
This allows for communications in a more secure manner as an interceptor would have to interrupt the laser beam to tap into the communications. By using different laser lines and encoding many transmissions onto each line, thousands of transmissions can be carried on a single hair thin glass fibre as in modern telephone systems. Much of the WWW information you access through the Internet is transmitted by fibre optic T1 lines from node to node. These transmitters use high speed modulation of laser diodes to send the data thought the fibres. You are probably familiar with the bar code scanner in your local supermarket or store.