DTR BDR-209 405nm Laser Diode shows a blurry square light.

[gazer101]

I mean it depends on your lens, I'm a bit psychotic when it comes to cleaning lenses but sometimes no matter how clean it is there are tiny imperfections from the manufacturing process... Try using a different lens to rule it out as the cause

 

[RA_pierce]

That is true, but with white paper I can see the true beam profile for leaking artifacts.
I'll be using this laser diode for exposing PCB photoresist material. Any hint of leakage of UV light will expose the UV sensitive material.

I see the problem. It may be best to replace the diode.

If you need very high precision and need to eliminate leakage of unwanted light from the diode, you may want to consider spatial filtering.
It is not easy to implement (maybe you have the capabilites) but it will give you a very clean beam.
The BDR-209 diode is the right choice but even an undamaged diode will have some artifacts that spill out from the main beam. Spatial filtering is the most effective way to deal with that.

Personally I think the G-2 lens is good. However, I have had mixed results with the ones from Chinese ebay sellers.
Sometimes they are very poor quality.
For this reason, I order optics from Edmund Optics. It's very expensive but worthwhile for quality assurance if performance is more important than cost.

However, I do not think the lens is the primary problem here.

 

[rajhlinux]

I see the problem. It may be best to replace the diode.

If you need very high precision and need to eliminate leakage of unwanted light from the diode, you may want to consider spatial filtering.
It is not easy to implement (maybe you have the capabilites) but it will give you a very clean beam.
The BDR-209 diode is the right choice but even an undamaged diode will have some artifacts that spill out from the main beam. Spatial filtering is the most effective way to deal with that.

Personally I think the G-2 lens is good. However, I have had mixed results with the ones from Chinese ebay sellers.
Sometimes they are very poor quality.
For this reason, I order optics from Edmund Optics. It's very expensive but worthwhile for quality assurance if performance is more important than cost.

However, I do not think the lens is the primary problem here.

Thanks I'll look into Spatial filtering and Edmund Optics will assure for quality control in expense for extra cost.

 

[RA_pierce]

Here is a nice demonstration of spatial filtering:

Good luck!
Be sure to show us how the project goes as you continue to work on it.

 

[Hemlock_Mike]

Jordan sells good parts - No problems here.
Does the artifact rotate when you turn the lens?
That can tell you where the problem is caused.