Mitsubishi ML520G71...Red Holy Grail or Flashlight Fail ??

[andythemechanic]

Could be, but 3 posts ago he stated a measure which is not even supported by the attached image. It always matters of course how you define terms like "beam with" or "divergence" but the best investigated and most well understodd method for which the BPP conservation law is stated is the 1/e^2 (for gaussian beams otherwise 2nd moment) method. From a show point of view it is possibly the "95% power content" value which is more important but that is possible even worse.
I know that this possibly sounds very negative but it is not meant in this way. Much energy is put in testing things out which are clear to be not fully satisfiying at the end. In my opinion this energy is wasted and better put in more promising activities.
Her I propose A measure which everybody should use when comparing diodes and trying to use new ones:
Take the emitter size and multiply it with the full ange 1&e^2 divergence of the diode and you get the BPP. For single mode diodes the value is wavelength/pi and emitter size is already defined by the divergence angle. Take the nominal power and divide it by the BPP. You get the Power/BPP value. Multiply it with the relative visibility at the wavelength (luminous efficiency lumens/watt). You end up with a value of how visible you beam is for a given beam quality. Calculate this value for all available diodes and compare.
I did this and this is where my statement of superior single mode diodes comes from.

Best
Andreas

[Solarfire]

Hi Solarfire,

how do you measure beam size?
When I measure your far field image with imageJ under the asumption that your camera is linear and that the squares are 1mm I measure 41mm 1/e^2 slow axis beam size, see attached screenshot.
The theoretical limit with the lens combination and emitter size of this diode is 31mm so your result is still improvable ~30% using better lenses. This then corresponds to2.8mrad full ange 1/e^2 divergence.
Ot to put it in other words: 1. Beam parameter product is a constant 2. With their BPP this diodes are still not very usable for showlaser use.
Sorry to be so negative here, but it always kicks me how much it is tried to beat the laws of physics here. I am watching this thread the whole time and to be honest: this diode is not the holy grail and will never be. In terms of Power/BPP a knife edge setup with single mode diodes is still a factor of 3 or so superior and easier from the optics as well.


Best
Andreas

Hey Andy,

I'm afraid your method of determining beam width via the pictures I posted is majorly flawed, simply due to the fact that chip saturation of the camera is not taken into account. Saturation clips the max luminosity which can be captured by the camera chip thus making the surrounding stray light appear brighter than it is. In the case of the picture the area which is yellowish/orange is the area which determines the actual beam with of ≈ 17mm. These pictures look different to the live situation due to saturation.

As too the usability of these in projectors… absolutely. I take it you currently have a setup on which you can base your assumption too the usability of these diodes?

[andythemechanic]

Hi,

First of all the image does not look saturated, at least if one assumes 8bit dynamic range of the camera. I looked at it before I analysed it with imageJ. Of course color cameras are anyways not well suited to analyze beams, so the question how beam size is defined in that case, remains.
Well I use these emitters professionally and know all their parameters and that theory and experiment fit very well together for them. They are made for display applications where BPP is no major concern. I analysed them a lot in the lab, but can not go too much in detail because of an NDA. I only can say that for applications that are BPP sensitive there are much better options. The Opnext 170mW diode for example.

Best
Andreas

[Solarfire]

Of course single mode diodes are always the winner hands down, absolutely no question about it and no one is claiming high end out of these diodes. Fact is, in comparison and for little money a quad system with >1200mW (probably >1500mW) is possible with a <4mm x 4mm beam @ the aperture with <1.2mrad divergence with acceptable beam quality. I wouldn’t invest in material for 2 quads if I wouldn’t have done my homework to determine usability first. So a certain bang for the buck factor is definitely there.

Trust me, the camera is majorly saturated. The camera is about 80-100mm form the spot with the diode running @ 400mA with an output of 270mW. I’m always happy when the camera is still working after taking such shots.

[Lazeerer]

i'm concerned and i am still begging around for some dr lava lenses

thanks for posting your results frank!

Have you tried to contact Flaminpyro on the other forum:
http://laserpointerforums.com/members/flaminpyro/

The only way i scored a pair of Dr. lava optics was second hand however Flaminpyro is a distributer of Dr. lava's drivers so he might be able to get you a set or he might even have some available. Its worth a shot.

Hope that helps some.

[steve-o]

Well, success for me anyway.. I don't know if this would be considered a monumental moment for everyone, but it is a small victory for me
Using the Lavalenses, and an aixiz triple element col-lens, the 100 ft far-field spot is the same size (or maybe a little smaller) as my dpss green reference instrument. Woot. Oh, and it's ~400mw after all optics. Now I see why this is the way to go. Can't wait to try Dave's 2mm lenses now and the newer GB cyl-lenses.

[badger1666]

hey steve-o glad you got some results
what you driving at to get 400mw after the aixiz and lava lens ??
when you switch to daves lens be prepaired for the larger far field spot,but more power,
i am suprised to see so much power from that aixiz lens though

[steve-o]

Thanks Badger! 826mA, driving the sh*t out of it, I'm sure.. I don't remember what the spec sheet says, but probably it won't last long at this current ..
With Dave's 2mm lenses and a larger farfield spot I'm assuming better (smaller) aperture beam size?

[badger1666]

Hey Steve
Smaller beam, what are you getting with the aixiz??
With Dave's lens and first cylinder at 65mm I get 4.5mm apeture with 1.1mrad would be happier if it was less, maybe. .85mrad, but its great for beam shows as is, and just over 1w from the pair driving each@ 720ma I am very happy
Dot know what can be had from Dave's 2mm lens though other than it makes apeture beam small enough to stack
Two easy,but the setups fiddly to get right

[badger1666]

I looked at the power levels using pangolin today,put up a cone cue and was still getting
>90% power out the projector,with other cues I got less power but still>50%
So I don't expect my diodes to last long,clocked up 60hrs at 720ma so far

True, they are not run at cw in projectors, but the duty cycle using using Pangolin is way higher than 50%