Diode Quantification

[The_Doctor]

Dan, did you decapsulate more than one G71? Also, did you see any evidence of irregularity, asymmetry or lack of concentricity in the die's mounting with respect to the main axis of the diode body?

I'm not saying I've seen any (not got the means to do it), I'm trying to establish where the variation might be coming from that caused people to choose a mount that allows looser diode placement when using very short focal lengths in a lens.

Related question... Did anyone see the centre of the beam appear to rotate around some point as they adjusted the focussing thread of the lens barrel? I'm not talking about wobble, I'm asking if this was seen by anyone even in cases where teflon tape or other means was used to eliminate the wobble that otherwise exists in the thread tolerance.

[danielbriggs]

Crow,
I didn't specifically measure that; it can be done in a snap if needed. Rather poorly both G71 and P73 were samples size of 1. IIRC, one of them cost ~£80 a diode, and I didn't fancy trashing loads of them, (nor could afford to!) at a time when they were close to being hen's teeth.
This is pure speculation, but I would say the diode would not be source of the misalignment, more the variation in lens mounting to the holder, resulting in a poor concentricity between the diode+lens, exasperated by the short focal length.

That said, should anyone have any diodes they want running through a similar mangle, I'd be happy to help.

[The_Doctor]

Eventually I will have some for you. I will try to be gentle to them, but any deaths, and I shall donate their tiny bodies to Science.

I agree with you about the lens. That's basically what I was trying to gauge. I bought mounts with fixed concentricity, as it's far easier to be sure a new diode will have its die where the old one was. This will make it hard for me to set ideal focus according to much advice, but that's what I'll investigate. I already have some notions about setting reliable concentricity, assuming that the holes in the mounts were initially concentric, coaxial with each other. They seem to be, they were made with better skill and means than I could manage on my own efforts. So long as they are, that leaves the thread tolerance, and the lens fit to the barrel. I think I can solve both.

All that said, if anyone can offer good description of how errors in pointing accuracy and such appear when focussing their setups, that will give me plenty to think about. Bake my noodle, I dare you.

[planters]

I think it is more likely the lack of perfect alignment is coming from the lens. With these very short Fl lenses sitting in mounts that have a clearance up to 10um (they do) this could explain the need ti compensate this not to mention slight out of plane operation of these same optics.