Rectangular Laser Beam Fix.



Recently I purchased a 5 .5 watt laser module for my laser engraver. While I was waiting for it to be delivered, I told a friend, who also does laser engraving, about it. He told me that he had heard that the 5 watt laser modules only projected a rectangular beam instead of a small circular beam. Sure enough when I got the module, he was right. The picture with the red circle shows how large the rectangular beam was at its smallest focus.

Step 1: Troubleshooting...

I unscrewed the lens assembly off of the module and noticed that the laser diode was an open type instead of the normal laser diode that has a metal can with a small opening in the top for the laser beam to come out of. I wondered that if this was why the beam was rectangular, could I do something to circularize the emitter area of the diode.

Step 2: The Fix.

I put a nylon washer on top of the diode to prevent a short circuit.and a small metal washer on top of the nylon one.

Step 3: All Better.

EUREKA! That did it. I now have a circular beam from the laser module that is capable of a very fine focus.

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    4 Discussions


    10 months ago


    I use the same laser diode attached to a small CNC mill, and I had nice results with it, engraving pcbs and both anodized and powder coated aluminum plates.

    But I found sometime ago problems with the beam shape, I noted when engraving a straight line along X axis result is quite better than the same in Y axis.

    I guess it’s because the intended operation for this kind of lasers, which usually run in a similar way as printers do.

    Would this fix address this problem?

    Did you place the washers in the emitting side of the diode? I can’t see how this changes the shape of the beam, but I’m not any kind of expert in optics. Doesn’t the washers just push the diode further from the lens?

    I’m willing to do it on my laser if it works, but I’d like to know why it works.


    1 reply

    Reply 9 months ago

    The washers are inside of, and are supported by, the diode module. They do not move the diode. The diode's emitter was previously uncovered and the area where the light was generated was a rectangular area. By placing the washers over the emitter, the light can now only come through the round hole in the washer.

    I will say that this has reduced my focal distance to about 3 cm. Anything farther away and the beam begins to defuse.


    10 months ago

    Interesting idea. It looks like the focus is much better. I have the same laser, but I am wondering if you have noticed a decrease in the power of the laser as a result

    1 reply

    Reply 10 months ago

    Not that I can tell. I wish I had a laser power meter to test it. My hypothesis is that since the washers are right on top of the diode emitter, that none of the light is actually lost, it just has to bang around inside the emitter until it finds the hole. The other solutions I've seen (Like putting tape over the lens) cut the power because the light is already out of the diode and is partially blocked by the tape.