Color smoothing and delay circuit implementation to help prevent "jellybeaning"?

[Anthony]

Why do you feel the need to comment on everything whether or not it has anything to do with you? Just askin'.

Gary,

Thats called. to participate... :-)
Interacting on a heavy basis.

[drlava]

I have used the sallen key LPF filter before in audio post-DAC filters to clean out high frequency harmonics, and also in other amplifier applications. Done right, it is a nice smooth (in the frequency range) filter.

I'm all for a circuit that can do color balancing, single-diff conversion, has this LPF (the last one on that page with the diode) and as mixedgas mentioned, a scanfail circuit also!! Note that the circuit as posted has a top end bandwidth only around 100kHz with the TL084 in simulation, which is less than the 260 kHz ideal you get from the ideal solution. If you replace the 2.7k resistor with 1.2k, the top end peaks out around 200kHz in simulation, which seems preferable.

for reversing the diode, more pots aren't needed, you can use two single-pin sockets since it's something that only needs to be done a few times at setup testing, then it can be soldered in place.

[DZ]

I'm all for a circuit that can do color balancing, single-diff conversion, has this LPF (the last one on that page with the diode) and as mixedgas mentioned, a scanfail circuit also!! Note that the circuit as posted has a top end bandwidth only around 100kHz with the TL084 in simulation, which is less than the 260 kHz ideal you get from the ideal solution. If you replace the 2.7k resistor with 1.2k, the top end peaks out around 200kHz in simulation, which seems preferable.

Hey drlava, can I ask what software you use for simulation? I've never used any simulation software, I've alway just thrown stuff on a proto-board to make it work. Sounds like I need to get with the times!

[stanwax]

Hi Rob,

You did the right thing. Every once in a while people contact me about that, and I tell them to do exactly what you have done. I am not sure if you ever contacted me about it, or figured it out for yourself, but I am glad that you found utility in the information we provide.

Bill

Bill I have not communicated with you about this I just read what was written and used it. Breadboarded first to prove the point - boy it didnt need much proving. Bill I know this circuit isnt rocket science but thanks for putting it out there, I'm sure now the results are proven and seen everyone who can be bothered to read a thread propely before commenting will be building one.

Very interesting results, Rob! I may have to build one of those delay circuits in the future...

You wont regret it - and its not like its a tough cookie to build

If memory serves, Rob managed to do something similar on one of his DPSS lasers not to long ago. (Though I think he didn't have the advantage of the fast photodiode and oscilloscope to measure the optical pulse.)

Memory serves well Adam - after I replaced the didoe in my CNI blue I retuned the TECS and minimised the noise by adjusting the TECs while the laser was being modulated. I watched the noise on my scope that was connected to a photodiode which sampled the beam by the reflection of the surface of a pass blue dichro.

And a big thanks to Bill for posting the initial info about the delay circuit that started this discussion!

Here here - ooops I already said that - note to self - read own posts properly.

edit, edit- Do you already have something printed up, Rob? If so, I'm third in line!

Yep I have a home made board printed up - not the prettiest thing and no posh SMDs justa quad op amp (LM324 at present) 3 pots (could be 6) and a handful of other bitz - probably less than £2 in parts. However if you scan over this post without reading it you may think I will pay you £2 for every board I make.

So, until the "Stanwax master board" is ready, would you be willing to share some details on the circuit that worked for you?

Sure Randy but let me just test it before I go making a Gary out of myself.

For example, what diodes and amplifier chip did you use, and perhaps a basic tutorial on how to setup and align a projector using your particular circuit?

Tutorial does not have to wait. Scan something white with black bits in - twiddle the pots till it looks nice.
end.
Honestly it is, as we say over here, a piece of piss.

Maybe you and DZ can get together on this. I'm sure you've seen his ILDA breakout board that he's working on... What do you say to a combined effort? Not trying to steal your thunder or anything, but like Jem, I think the two ideas work well together.

I looked at the thread about the ILDA breakout but I thought that the blue LEDs were just too much, and really why would it need a 3 inch tail pipe? Oh sorry I didnt READ that post, I just saw the title....
Seriously though sure at the end of the day its not my circuit so I dont have ownership of it and am happy to share what I have done with anyone who respects me enough to read my words properly.

I'm all for a circuit that can do color balancing, single-diff conversion, has this LPF (the last one on that page with the diode) and as mixedgas mentioned, a scanfail circuit also!!

Thats the goal I have and this is the first building block
now must stop reading things propely its taking too much of my time up

Rob

[drlava]

Hey drlava, can I ask what software you use for simulation? I've never used any simulation software, I've alway just thrown stuff on a proto-board to make it work. Sounds like I need to get with the times!

I use orcad which has spice built in. There are some freeware spice modeling programs out there http://www2.eng.cam.ac.uk/~dmh/ptialcd/spice/spice.htm
also there are spice models downloadable from many component manufacturers to that their parts can be simulated more realistically.

[Pangolin]

Bill I know this circuit isnt rocket science but thanks for putting it out there, I'm sure now the results are proven and seen everyone who can be bothered to read a thread propely before commenting will be building one.

Thanks Rob,

Here is the whole story behind that circuit. There is a company that makes laser projectors. Lets say -- REALLY FAMOUS COMPANY. Lots of people use their laser projectors. They are very expensive.

Well, one day we were communicating by email. They were complaining about our software not having a color shift for each laser. I wrote (as I always do) that, even if we had such a thing, it would not be a complete solution to the problem, but that there was a better idea that would be a complete solution -- just build such a delay for the laser.

They replied something like "yes, it would be nice, and we have had an engineer working on this for a year, and can't find the solution". So I made up the web page, just to show what had been done in the past, and my own solution to the problem -- the main part being a dual-slope low-pass filter. I personally had never seen such a dual-slope filter before, but clearly it was an easy thing to do -- at least for me.

So then this famous laser company wrote back to me that I was arrogant for suggesting that the problem could be solved so simply (just a single op-amp). So I actually built the "ready for anything filter" and brought it with me to a tradeshow, and hooked it up to their projector just to show that -- yes, it could work.

So, now everyone knows how arrogant I am. How foolish of me to suggest that I could come up with a solution that this famous laser company couldn't come up with even after a year of research...

By the way, that famous laser company, and some other quality laser companies use my circuit now... Of course this is what I wanted, and why I made up that web page. A software solution could only be a partial solution. This hardware solution is a more complete solution. After all, NOBODY would accept a situation where there are X-Y scanners, with the X scanner twice as fast as the Y scanner. This would not be acceptable. So why is it acceptable that you would have a projector where some lasers are twice as fast as other lasers?


Bill

[stanwax]

Hi Foolish Arrogant Bill
I guess that day there were servings of humble pie topped off with egg taken right offa their face!
I am aware of ONE laser company from China who use your circuit and I love simple elegant solutions which this is the epitome of. It does no more or less than we need and is effective. Perfect!
Rob

[Anthony]

I am aware of ONE laser company from China who use your circuit and I love simple elegant solutions which this is the epitome of. It does no more or less than we need and is effective. Perfect!
Rob

So you are saying that when i buy my green and blue lasers from Big monkey brother bridge (later this year) i will have no problems an do'nt need to make such a circuit for those lasers?

Cool

[DZ]

Thanks drlava, I'll check it out!

[stanwax]

So you are saying that when i buy my green and blue lasers from Big monkey brother bridge (later this year) i will have no problems an do'nt need to make such a circuit for those lasers?

Cool

Hi Anthony
Actually no Laser-Wave is not who I meant. Its a projector manufacturer, and the emphasis was for another reason . My idea was to build a device similar to what Jem suggested - all singing all dancing ilda interface and make some so we could all benefit from the advantages of it. As I said this is the first building block and though is fine and dandy to use on its own it was never inteded from my pov to be a complete device.

Rob

BTW have you seen the matrix?