Some experiments with the blue LD's

This is a forum to share experiences and ideas about holography.
Colin Kaminski

Some experiments with the blue LD's

Post by Colin Kaminski » Thu Jul 29, 2010 3:19 am

I calculated the wavelength resolution for the complete system to be about 0.013 nm/pixel in the final image on the webcam.
That is what i was wondering. I wanted to know the mode spacing. Great work!

wler, if you make a turn key blue laser sign me up for one! I only need 100mw or so.

Thieu

Some experiments with the blue LD's

Post by Thieu » Thu Jul 29, 2010 1:28 pm

Colin, I'm afraid my calculation was a bit off, it was based on estimates for a couple of parameters. Today I did a real calibration based on the absorption lines in a small part of the solar spectrum. The width of the frame corresponds to 3.63 nm and since there are 352 pixels in that direction, the correct resolution is 0.0103 nm/pixel. The experimental error in that value is about 2% I'd say.

Colin Kaminski

Some experiments with the blue LD's

Post by Colin Kaminski » Thu Jul 29, 2010 1:59 pm

Did you hapen to measure any red shift in the eruption yesterday? The photos have been amazing! I wish I had my H-Alpha scope at work yesterday.

Joe Farina

Some experiments with the blue LD's

Post by Joe Farina » Thu Jul 29, 2010 5:15 pm

I was surprised how many sellers are now offering these diodes on eBay, at least 5. Prices seem to be dropping, the least expensive is $54.99 (free shipping). To see these, type in "445nm" in the search field on eBay.

Thieu

Some experiments with the blue LD's

Post by Thieu » Thu Jul 29, 2010 6:18 pm

Joe Farina wrote:I was surprised how many sellers are now offering these diodes on eBay, at least 5. Prices seem to be dropping, the least expensive is $54.99 (free shipping). To see these, type in "445nm" in the search field on eBay.
The reasons are pretty straightforward. In the +/- $700 beamer the 24 diodes are in a heatsink block that can be removed in less than 30 seconds if you've done it once. You don't even have to open the beamer itself. The diodes are connected to each other by a ribbon pcb, takes 30 seconds to remove. Diodes are not glued or bolted down, just stuck in the heatsink with heatsink compound. If you don't mind the hassle of packing, dealing with things going wrong in the mail etc. and don't mind the chance of your diodes ending up in a 14 year old's 1W handheld 'pointer'... it's actually a pretty good business.

Joe Farina

Some experiments with the blue LD's

Post by Joe Farina » Fri Jul 30, 2010 10:58 am

Thieu wrote:
Joe Farina wrote:I was surprised how many sellers are now offering these diodes on eBay, at least 5. Prices seem to be dropping, the least expensive is $54.99 (free shipping). To see these, type in "445nm" in the search field on eBay.
The reasons are pretty straightforward. In the +/- $700 beamer the 24 diodes are in a heatsink block that can be removed in less than 30 seconds if you've done it once. You don't even have to open the beamer itself. The diodes are connected to each other by a ribbon pcb, takes 30 seconds to remove. Diodes are not glued or bolted down, just stuck in the heatsink with heatsink compound. If you don't mind the hassle of packing, dealing with things going wrong in the mail etc. and don't mind the chance of your diodes ending up in a 14 year old's 1W handheld 'pointer'... it's actually a pretty good business.
I see. So, if someone gets $60 per diode, 24 times 60 is $1,440. Subtracting the cost of $700 yields $740 profit, or about $31 per diode. Not too bad for going through the hassle of selling and mailing. Maybe those projectors have some other parts too.

dave battin

Some experiments with the blue LD's

Post by dave battin » Fri Jul 30, 2010 11:08 am

Thats correct Joe! It was better when they were selling for $75-$100 each! I did two projectors and quickly made my money back and still have an extra projector. there are various lenses, front surface mirrors, dicloric beamsplitters,and a red LED Phat light in each of these projectors.......... aside from the DLP module and PCboard!

by the way i did a test last night to see how deep a transmission hologram i could make(w/one beam), and i got an image at 20 inchs deep!

Joe Farina

Some experiments with the blue LD's

Post by Joe Farina » Fri Jul 30, 2010 11:24 am

Wow, 20 inches is really impressive Dave. I've just bought a diode to get my feet wet, maybe I can work on some of the less demanding problems like collimation Thanks a lot for the planned tests with DCG.

wler

Some experiments with the blue LD's

Post by wler » Fri Jul 30, 2010 11:59 am

Joe Farina wrote:Wow, 20 inches is really impressive Dave. I've just bought a diode to get my feet wet, maybe I can work on some of the less demanding problems like collimation Thanks a lot for the planned tests with DCG.
Actually not so much single mode operation but beam quality is more the practical problem with those diodes, especially if one desires an even illumination. It is almost impossible to get the beam through a spatial filter without great losses, for example. A way to ameliorate this would perhaps be to split the beam at a dark band with a knife-edge mirror and so use the otherwise wasted part as object beam for example.

So in order to make good use of the diode, some things need to be specifically tailored for it. The very least is a pair of anamorphic prisms or suitable cylinder lenses to get the beam in a better shape to begin with.

Joe Farina

Some experiments with the blue LD's

Post by Joe Farina » Fri Jul 30, 2010 12:34 pm

wler wrote:
Joe Farina wrote:Wow, 20 inches is really impressive Dave. I've just bought a diode to get my feet wet, maybe I can work on some of the less demanding problems like collimation Thanks a lot for the planned tests with DCG.
Actually not so much single mode operation but beam quality is more the practical problem with those diodes, especially if one desires an even illumination. It is almost impossible to get the beam through a spatial filter without great losses, for example. A way to ameliorate this would perhaps be to split the beam at a dark band with a knife-edge mirror and so use the otherwise wasted part as object beam for example.

So in order to make good use of the diode, some things need to be specifically tailored for it. The very least is a pair of anamorphic prisms or suitable cylinder lenses to get the beam in a better shape to begin with.
Yes, it will need to be worked on. What I should have said was less demanding on "me," and not in general :wink:

Hopefully some others will do tests on these diodes, and post the results here, so we can all benefit. New approaches and experiences from a variety of people might be crucial for success.

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