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What is a safety laser scanner? | APAC

Safety laser scanners (hereinafter referred to as “laser scanners”) are safety devices used primarily at factory sites to detect when a person is approaching to dangerous machinery or equipment (Figure 1).

When a person enters the warning zone of the laser scanner (yellow zone in Figure 2), the system alerts the person by a warning signal that triggers a buzzer sound and lighting or flashing of an indicator light.
In addition, if a person enters a protective zone (a hazardous place to enter) inside the warning zone, the machine’s start-up signal will be turned off and the machine will be stopped.

Once the machine is stopped by the laser scanner, the machine’s start-up permission signal will remain off as long as the person remains in the protective zone. The machine cannot be restarted unless the person leaves the protective zone. There is a certain degree of freedom in setting of the warning zone. In addition to a single warning zone, multiple locations can be set as warning zones, or no warning zone can be set at all.

Principle of Distance Detection 

Laser scanners generally use infrared lasers, which are invisible to the human eye, to detect people.
The distance to the detected object is calculated by measuring the time it takes for the laser beam emitted from the laser scanner to hit the detected object (a person) and reflect back to the scanner (Figure 3). Laser scanners also detect where a person is located in the warning or protective zone by calculating the distance by emitting laser beams in a fan shape at slightly different angles.

Application Examples of Laser Scanner 

Detection of Presence in Hazardous Area

A common use of laser scanners is to detect the presence of people before they enter areas where hazards are present (hazardous areas). For example, in a production line where a person supplies a workpiece to a robot as shown in Figure 4, the work envelope of the robot is set as a protective zone, and the robot stops when a person enters the protective zone to set the workpiece.

Setting of Detection Zone

In general, detection zone such as warning zones and protective zones can be set using special software that allows the user to set any shape as the detection zone on the computer screen (Figure 5). A detection zone can also be set up based on the data obtained from scanning the area around the actual installation site (Figure 6).
When setting the protective zone, the minimum distance required for safety specified in the standards must be satisfied based on the work area of the hazard.
Also, when setting the detection zone, attention should also be paid to the minimum size (minimum detectable object) of detectable objects. Since the laser scanner emits the laser beams in a fan shape, the farther the distance from the light source, the harder it is to detect small objects (the minimum detectable object becomes larger). Generally, the minimum detectable object is approximately 70 mm in diameter at the periphery of the protective zone.

Application Examples

Examples of applications using laser scanners are shown on the following page, so please also check this information.

Cautions of Usage and Installation 

Keep in mind the following points.

●  When setting the protective zone, the minimum distance required for safety specified in the standards must be satisfied.
●  External light such as fluorescent light, sunlight, or infrared light may cause detection errors. Install the laser scanner so that the optical window is not directly exposed to external light.
●  Detection errors may occur due to obstruction of the laser beam by steam or dust, or due to water droplets or dirt adhering to the optical window. The optical window may also need to be cleaned periodically. Check the installation environment carefully.
●  If there is a highly reflective wall or similar object near the detection zone the distance may be unable to be calculated correctly, and so a detection error may occur.