several lasers

[OmarYoussef]

Dear Members,

I have an installation where i have six lw pl8900 linked all to one qm2000 board by series, the pproblem i am having is that when i reduce the brightness i have 5 lasers that reduces the brightness at the same rate and the sixth reduces its brightness but on a slower rate resulting difference in colors..

i dont have another card.. anyone had a similar problem ? or does anyone know how to fix this problem ?

thank you guys !

 

[Aaron@Pangolin]

I think I spoke with you on the phone about this. There might be two problems, one is addressable and the other is just the nature of solid-state laser modulation.

If it is an issue with resistance building up on the ILDA signal cable within your projector daisy chain, your last projector or two might be getting less input signal than you first few projectors. You can fix this by getting a buffered ILDA splitter that will make sure each projector is receiving the same input signal levels or you can get a second QM2000 and run three projectors off each QM2000.

The problem might also be related to the fact that no two solid-state lasers will modulate exactly the same; meaning they will not produce the same output power given the same input modulation signal. Due to tolerances in manufacturing processes in cavity design, drivers, and even the diodes themselves, no two lasers will be exactly the same. Say you have two “identicalâ€￾ 500mW lasers.

In a perfect world they would both modulate the same provided the same input signal. For example:

0 volt = 0mW
1 volt = 100mW
2 volt = 200mW
3 volt = 300mW
4 volt = 400mW
5 volt = 500mW

As we do not live in a perfect world, the laser output will most likely look like:

Laser A
0 volt = 0mW
1 volt = 150mW
2 volt = 220mW
3 volt = 275mW
4 volt = 450mW
5 volt = 570mW

Laser B
0 volt = 0mW
1 volt = 50mW
2 volt = 180mW
3 volt = 250mW
4 volt = 400mW
5 volt = 600mW

If this is the issue there is not much you can do beyond getting an Eye Magic Iris Color safe system or something.

 

[lasrgreg]

yes, using multiple projectors in a daisy chain fashion (projectors linked to a single control) will show the lack of calibration common in almost all projectors. Some of these are hardware issues (exact gain behavior of typical dpss laser is rather complex), but a lot has to do with the manufacturers only measuring the max output. Linearity is a foreign concept, let alone a uniform calibration.

With a single laser, much of the linearity problems can be taken care of using color palette controls to get the R,G, and B lasers to behave pretty much the same way. But with multiple lasers, really the only way is multiple QM2000 cards, each adjusted to make one laser "just right".

I have not worked with the IRIS colorsafe system, although in theory this should do the trick. Multiple QM cards will definitely fix the problem.