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Saturday, October 30, 2021

MoBeam: Laser Focus

Laser Module in MOBeam

Is this module actually a NEJE module

If so which one?
  • 30820
  • 30610


Mistake in the manual???? Yes my focal point is 30mm.

If you assume the VG-L7X manual had the wrong units for focus, i.e CM vs MM.

Then I have a G8 lens in my unit? Is this a coincidence?

The smallest beam spot also explains why the dot looks rectangular (laser diodes do not operate in TEM00).

However, at the focal point, the intense area of the beam is round.

Finding The Focal Point

Focusing Techniques

4% is low power setting used for focus

The Empirically Derived MoBeam Focal Distance

Focus Using a USB Microscope

There are multiple videos on the use of a USB microscope to safely look at the output of the diode and adjust the focus. I decided that I would start finding my focal point by using this method.

Test Setup

I used a USB microscope purchased* from Amazon. 
* I am very happy with this unit's price and performance.
  • Make a target by painting a substrate with flat black paint. I used a round steel medallion. A black surface makes it easier to see the most intense part of the beam. 
  • Put on your laser safety glasses
  • In Vigoworks turn on the "weak beam"
  • Place the microscope on its stand in front of the laser module focussed on the beam.


Watching the beam on the microscope:
  1. Adjust the entire module up/down to get the smallest round spot.
  2. With the module fixed in position adjust the lens until the smallest round spot is achieved. 
When you adjust either the module or the lens you will note that the beam changes from a round spot to a rectangular one as it goes in and out of focus.

In this video, you can see how I went about finding the focal point.

These tests show that the focal point is indeed 30mm.

Depth of Focus Measurement


Focusing For Cutting vs Engraving


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