Red Wavelength Choice

[taggalucci]

and 3 times the price, oh to be rich and could afford all these fancy modules.

I hear ya! However I think it's interesting that when you factor in the luminance vs cost, the difference narrows quite a bit.

why does the forum insist on only recommending 637 these days? if its not 637 yoour doing it wrong and the forum doesnt approve.

I like 660nm (especially with the 445nm blue for awesome deep violets and purples)

Thing is, if you wanted to get enough red to match about 2W of blue and 2W of green, you'd need around 6W of 660nm. So that's 24 x 660nm diodes, assuming you run them at 250mW. In fact you'd need to run them hotter than that to get 6W after combining. Now a 24 banger is a serious engineering feat, and I take my hat off to you Andy for your amazing effort in doing this.

You can get 2W of 637nm or 640nm which should match the 2W of blue and 2W of green in 12 diodes. Yes, more expensive diodes, but less diode mounts, lenses, flex mounts, mirrors, TECs, Lasorbs, drivers etc...

[andy_con]

100% agree with you, but the original post says cheap, or there abouts.

so if someone is interested in cheap why we are recommending very expensive.

we would all like perfect projectors, with perfect colours and perfect scanners but thats not the real world. so why arent we saying this is the perfect module for you but if you are after cheap try this

[danielbriggs]

BTW according to Chroma...

[LaNeK779]

well, something does not add up here... 2w of 532 + 3.6w of 445 and a cheap red with up to 8 diodes, is simply not going to happen.

- v1: forget the 8 diodes and go to a design with 16 diodes (or dual 8 bangers) were 14 is 660 2 is 637 (or 12 + 4 if you can afford it). still, i think that the red will be underpowered though...

- v2: forget cheap and go for 8 diodes 637

tough...

but what a beast this will be when finished!! easily into the 10w area

[andy_con]

i bet you could count on one hand the number of people on this forum who own a 637 module, yet its the must have red module, as nothing else will do

[dilbert]

Thanks for all your inputs, I've got my answer - I didnt say it 'had' to be cheap, was more interested in the results from mixing wavelengths & getting my head around the fact that 1.6W of 637 will be much more visible than multiple W of 660.

I've already got the design & build well underway on this projector so 8 red is the max - I've ordered a couple of the Opnext 637 to start. I will be building the module up with the cheap 660's though while I build & tinker to get it & drivers working etc - much rather kill one of these in testing so I will get a chance to compare.

It's a shame the better diodes do cost ££££, hopefully they will become cheaper in time or get used in some more mass produced consumer gear......

Anybody know of any developments on the horizon?

[norty303]

In my opinion, the 'best' is whatever achieves the required brightness with the required beam specs with the greatest simplicity (i.e. least chance of going wrong in the future/require constant fettling)

I think that 637/642 is the answer there.

I care not whether it makes 1W, 5W or 100W of power, what matters (to me) is the beam brightness, of course with the added advantage that lower powers overall are safer.

I really don't see the point in having a mixed diode head if you could have achieved the same brightness with less diodes, and hence less optics, less alignment, less correction optics, less cooling, etc Sometimes spending that little bit more brings a lot of benefits.

[taggalucci]

i bet you could count on one hand the number of people on this forum who own a 637 module, yet its the must have red module, as nothing else will do

Speaking for myself...

Having gone through the journey of discovery in all that is red when building my first RGB, 640nm was what everyone here was raving about. The logic was clear, nice tight bright red beams, more luminance than 660nm or 671nm. The cost for the power I required was more than I was willing to spend and I must say I'm still ok with my 635nm "torch" (even though there's a slight pink halo to my beams in that projector)!

I have since enjoyed building my own red from 660nm LOC diodes and observed the benefits of these diodes' beam specs. However, the lack of luminance mW for mW is painfully obvious.

Given this experience it seems more than reasonable to use something in the 635-640nm range (especially as I'd prefer to run my lasers at lower Watts with max luminance for audience scanning reasons).

635nm is a bit orange but not too orange. I'm not sure about 637nm. If I remember reading correctly, the new 637nm diodes can be run at higher currents than the 640nm diodes.

So unless my logic and research is flawed, why wouldn't my next 2W red be based on 637nm diodes and why wouldn't I promote this to others despite not yet having the moolah to actually own one!!!

I do get your point Andy, though I suspect the matter of ownership is just simply a matter of time before more of us get past our current projects and on to the next big red!

[White-Light]

100% agree with you, but the original post says cheap, or there abouts.

so if someone is interested in cheap why we are recommending very expensive.

we would all like perfect projectors, with perfect colours and perfect scanners but that's not the real world. so why arent we saying this is the perfect module for you but if you are after cheap try this

Whereas I agree with what you're saying Andy, how do the economics work out?

If we're saying 2 Watts of 637nm is going to be the balance point for red, how much does more than 6W of 660nm cost - as that's the equivalent power vs luminosity point based on a figure of 3 times as bright.

Then there's also the safety implications of 6 watts of red.

I still haven't seen 637 so I'm taking Martin's word on it being as dark as 640. If not, there's very little brightness difference between 637 and 640 (approximately 15%) or 1/7th brighter according to Dan's favourite utility.

I think that's why people tend to use the brightest colours as a starting point unless like 445, there's such a price difference as to make the brighter colour unthinkable for most people's budgets.

[LaNeK779]

well, 637 is unthinkable for me at the moment. all i can do is put all the spare change from my trousers to a little box.. and when this little box gets heavy enough, i'll buy myself a brand new shiny 637. there are stills lots of parts to be bought before i start to get picky about red wavelentghs

to me, if there is a dilemma between 637 and 640, i say go for the 637. case isolation just by itself is a winner.

if the dilemma is between 660 and 637, i say stick with the 660 and enjoy the deep purples etc.

the only cheap way out of this is get a 660 and extreme cool it to some "undiodly" level of the celcius scale to get closer to 645nm. but this carries its own world of different problems (heat dissipaton, condensation etc etc etc)