Compensating for slow 532nm diode modulation

[macpod]

I've noticed the multiple 532nm diodes I have are slow at coming up to full brightness compared to other diodes I have. What normally is done to compensate for this?

My thoughts were to build a n analog diode driver that utilizes the brightness feedback component, but also has a peak current limit built-in.

Will this work or am I going to run into some unanticipated phenomenon? Is there a simpler way to account for this aside from software?

Attached is an image demonstrating the delay of these diodes. Notice the cyan and white lines in particular. (Taking accurate color pictures of lasers is hard!

lasershark_rgb_untuned.jpg

And just for fun, here's some beams:
lasershark_rgb_beams.jpg

[taggalucci]

Hey there...

This is a byproduct of DPSS slow response compared to the fast response of direct diode lasers.

There's much discussion here regarding this and a search on PL for "color correction" should find some treasure.

Check out this product that I'd recommend to solve it...

http://shop.stanwaxlaser.co.uk/dz-co...oard-252-p.asp

Good luck!

[macpod]

Thanks for your response taggalucci and also for the search terms.. sometimes not knowing those is the hardest part when figuring something out. Ever tried searching for an unknown schematic symbol?

So that unit appears to be a signal "massager" vs something that is done with the drivers. With a few exceptions, I think all of this can be done in software?

Gain - allows the signal of each channel to be boosted or reduced from 0 to 1.1
I have this setting on my diode driver so it seems redundant to do elsewhere. Since they are only reducing the signal, I could do this in software too at the expense of precision. Their unit does have the advantage of maintaining precision however.

Offset - or threshold sets the point at which the laser turns on therefore giving the greatest range of modulation as well as allowing matching of the turn on point of the lasers.
I have this setting on my diode driver. I also have this capability in software but changing it hasn't seemed to help much. That does give me the idea to review it however. I'll bet I can improve this now a little.

Rising edge delay - adjusts how quickly the laser turns on when its blanking >300uS of adjustment
I have a delay function in the software already but it doesn't fix the problem since the green still "fades" on vs immediately coming up like the blue/red diodes. I'm not sure if a hardware module can help any more than a software solution can here, can it?

Falling edge delay - adjusts how quickly the laser turns off when blanking >300uS of adjustment
The green shuts off just fine. Phew at least something works right. haha


This product gave me a crazy idea to try in software now.. I'll watch if the green channel is getting brighter or darker.. and if brighter, I'll add a gain component to this (e.g. if the value goes up by one, then I'll bump it by 2).. but when I identify it's a a max value after this, I'll drop it back down on the next samples to what it normally is supposed to be. I'm thinking this will help reduce the "fade" on time I'm seeing. Think of it like a kick in the pants after the laser naps. That's sure to wake anything up in a hurry.

Wish those 510nm lasers would come down in price alrady