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

educa

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Jun 25, 2011
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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
 





Drew

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Oct 6, 2010
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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
 

educa

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Jun 25, 2011
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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
 

DTR

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Jun 24, 2010
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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.;)
 

educa

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Jun 25, 2011
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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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