Red diodes and collimators.

[krazer]

I know this thread is getting terribly off topic--but I thought I would remind you guys of how divergence works.

The divergence of a diffraction limited laser beam and its diameter are inversely proportional--obviously not all the the lasers we use for show applications and not all of the cheep acrylic lenses offer diffraction limited performance, but just about any DVD or blu-ray diode is going to give a m^2 of <1.3 or so, which means at worse case you will get about 1.5 times the ideal divergence. I doubt that axiz lenses are diff limited, but they come fairly close, and pretty much any glass asphere you buy these days is diff limited.

That in mind, you can set the beam diameter by looking at the divergence of the raw diode (you can look this up in the data sheet, it is usually 10degrees in one axis, 20 in the other, which gives rise to the oval shaped beams) and use arctangent to calculate what the size will be at the effective focal length of your lens. It usually isn't an issue, but its also a good idea to check the NA of the lens and make sure its greater than that of the diode, which is about .3-.5 for a typical single mode diode). This calculation can be somewhat kudgy, since with an asphere the focal length is not really clearly defined as it would be with a normal lens, usually you can just use the effective focal length and not worry about it, but if you get a number within 10% of the measured you are doing pretty well.

From that, there is a nice simple calculator that will tell you what your diffraction limited divergence should be at http://www.nvginc.com/beam_divergence.htm.

So to conclude--the shorter the focal length of the lens the small the beam, and higher the divergence.

[edison]

Its very nice to have those collimators. There is one problem.

If you ordering something from Marco. he never responds and if he responds it is after 3 till 5 days)

I ordered 4 of these collimators so and i ordered these more then a week ago.

for me its just a hobby but can you image when you reallly need the components for a show

[kl79]

ok guys, I told a friend of mine wich is also a good friend of Marco and he will remember him to check a littleoften his pm box.

Also If anyone's interrested, the same friend is selling a brand new complete set (driver, collimator, diode 642nm 150mW)from marco. Ask me for the price.

[edison]

I have decided to cancel the order for the collimators. It takes to long since i ordered these 3 weeks ago. I,m going to look for another supplier. Nothing personal.

[andythemechanic]

Hm strange. I also ordered collimators from Marco and had no problems. Delivery was not the fastest though, it took arround two weeks.

[marco]

Hello,

sorry - i was on a business trip and not in the office.

greetings,
marco