The use of periscopes is not restricted to submarines! Laser beams are often raised or lowered with this optical arrangement. Common examples include matching the beam height to a gantry rail on a laser machine and, in research, directing a beam through the entrance window of a test cell.

The principally danger of periscopes lies in the upward travelling beam (see item 2 on the list on page 2), particularly if the beam is at below head height. To illustrate the point, such a beam was the cause of a recent laser accident involving a beam splitter and power meter used for on-line beam measurements. A lack of space on the optical table prevented placement of the large power meter, so the beam splitter was pointed upwards and the meter was seated on a tripod pointing down. The eye injury occurred when the power meter was accidentally knocked off the tripod as the victim leaned over the table.

For periscope use with Class 3B or Class 4 lasers it is important that:

1. the upward beam is enclosed to prevent human access,
2. the mirror that turns the beam upwards has restricted angular adjustment (e.g. mount the mirror on a 45° block);
3. the top turning mirror is securely mounted.

Pro Laser provides practical safety design solutions.