Achieve Machine Safety with Light Curtains


As automation becomes more and more popular in all commercial and industrial application it becomes more important to keep the people who are working around this automation safe. One of the ways to do this is with using a light curtain.

When looking at the SF4B Series of light curtains Panasonic looks at a few ways you can use curtains. Here the user has connected 3 curtains in series to create a barrier around a robot.

Note you would need to make sure your specific curtain can be connected in series. The SF4B series in the example can do up to 3 units in series.

Here we have a curtain in front of a machine this would prevent someone from sticking there hand into a machine.

Those were just a couple applications in which light curtains can be used. Not lets look at some of the specifications.


Protection is generally placed into 3 categories. Finger, Hand, and Arm/Foot. These are categories are set by the size of the object they will detect and the beam pitch. Looking at the example series from Panasonic they classify by the following.

  • Finger: 14mm diameter object and a 10mm beam pitch
  • Hand: 25mm diameter object and a 20mm beam pitch
  • Arm/Foot: 45mm diameter object and a 40mm beam pitch

Note: You should always verify the needed pitch with the pitch in the data sheet. For example when reading the Omron F3SG-R Series Data sheet they give a 20mm beam pitch for their hand sensor, however they are stating a 30mm object diameter is the detection capability.

Beam Pitch

This will be the distance between beams.

Note: This is not the object size that the curtains will detect. See Detection capability.

Detection Capability

This is also called Object resolution. This is the minimum size of an object that the light curtain is able to detect.

Operating Range

This is the range or maximum distance that your transmitter and receiver can be from each other to create an effective curtain. If you look in the data sheet you will see a range as there is a minimum effective range as well.

Protective Height

This is the height of the protective area. Often the Beam Gap X the number of beams. This will often be just slightly shorter that the transmitter/receiver units and is not adjustable.

Number of Beams

This is simply the numbers of beams that are in your light curtain. The protective height and Beam Gap will determine the number of beams in a certain curtain.