How to Center Your Laser Beam for More Accurate Power Measurement

There are several considerations when you’re trying to maximize laser power meter accuracy.

One that I don’t usually mention is perhaps the most obvious question: How do you know the entire laser beam is actually hitting your sensor?

I mean, if you have a visible laser, fine.  But most lasers these days are in the near infrared region.  Many sensors, especially in the low power region (~10 W and below) have small apertures.

It may look like your laser and sensor are aligned well, but you never can really be sure without seeing the laser beam.

But the laser is invisible, so how can you see it?

There are two choices:

IR Card

One method is to use an infrared viewer, or IR card.  If you have direct access to the laser and it’s not a safety concern, this could be the simplest method.  It’s certainly the cheapest.

However, I know from experience that this doesn’t always give a good picture of where the beam ends since you usually have to look at the beam from the side and you have parallax problems.  Most also don’t work past about 1700 nm.

Power & Position Sensor

A more elegant solution is to integrate position sensing in the same sensor that measures power.  Now you will get instant feedback relative to the sensor position, which is precisely the measurement you’re trying to optimize.

Simply turn on your laser, and see where the crosshairs show up on your meter or software:

2016-10-19 blog p1

Then make adjustments to your laser pointing position until the crosshairs line up with the center of the sensor.

This will give you optimal accuracy.  Not just for the obvious reason that you can be sure you’re measuring you’re whole laser beam.

It’s also recommended to measure in the center 50% of the sensor area as it is more uniform there.  So you got an added bonus!

For more on keeping your measurement accuracy up, see Laser Power Sensor Accuracy Specs: Unveiled


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