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looking for: 405nm laser for burning very very smal spots at +- 1meter (3 to 4 foot)

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educa

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Hi,

First of all I'm not a newbie to lasers, since I work with them for about 3 years now.

In the beginning I worked with fibre-coupled 808nm diodes of 1 watt, but I stopped those because I prefer to SEE something instead of visible IR.

Currently I use a 700mW 445nm blue laser on my portal cnc machine to engrave mostly dots and lines in wood.

This works nicely, but a 445nm laser is not a point source of light and focussing it is quite hard. If I want to focus to an acceptable small point, then I need to focus at less then 1" from my diode and lens and then I can burn small points of aproximately 0.2 mm size. These points are not points, but rectangles because thats the way how a 445nm focusses.

Yesterday I tried to focus my laser at a distance of for example 1 meter (3 a 4 foot) and while I managed to get a more or less small point, it was a lot bigger then what I needed to burn a spot on wood. I also read that on a 445nm this would be very hard to do.


What I want to do is have a laser beam go through a closed loop galvanometer at 20kpps and then throw the beam about 1mm away on wood. The galvo's deviate the beam and then I could position with that my beam and burn small dots.

Question: Can a 405nm blu-ray diode be focussed at a distance at a very small spot (445 cannot)

Question2: Are there also drivers for those 405nm which can source the needed current to the diode, but which can be turned on/off bij TTL or PWM?


I'm more or less looking to buy something like this.

Kind regards,

Bart
 





405 can be focused much smaller for burning due to it's much smaller emitter size and that it's single mode. At the same power level (700mW) and distance (3-4') 405 should be a better burner. 405 is much less visable while still being at least as dangerous as 445 to eye/skin exposure
 
ok thank you for your answer. The question is however not completely solved (or at least I am not 100% sure yet :)

With my current 445nm laser at aprox 700mW I can focus on a spot less then 1 inch away from my module and I can burn spots of 0.2mm size in wood or paper (laser is therefore only powered on for 3 to 4 milliseconds by the way). If I set the laser to focus at a distance of 3 to 4 foot, then I can ALSO focus it , but the minimum point size I get is a couple of mm big, so I cannot burn 0.2mm size pits in my wood at that distance.

So the question is more like: would a 405nm single mode diode laser be focusable to such a small 0.2mm point over a distance of 3 to 4 foot?

The galvo will have to throw the beam around 4 foot away because I need a quite stable focal point and the closer to the diode I focus, the les usable focus depth I have.


Kind regards,

Bart
 
You will be able to focus the beam to a extremely small point several meters away with the 405 since it is a single mode diode. I have burned stuff @ over 40 feet away and I think the hardest part is making the fine adjustment to the focus over long distances.;)
 
To get a good focus I'm going to set the flens on a stepper motor with extreme reduction. This would allow me to focus 1 full turn of the lens in maybe 3200 steps, so I guess that would suffice :)

The laser seems capable so now need to find info about the driver. These p3 flexmods could be the solution but I only found the post you told me DTR and not yet scematics or so. Will continue my search in some minutes
 
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