Wow, really tight beam, what's my divergence?

• Jan 24, 2008

• #1

Chicxulub

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My cheap little keychain red laser has one of the tightest beams I've ever seen in a pointer. At the source, it's dot is 3.5 by 2.5 mm. At fifty feet, it's 10mm by 7mm. That's always struck me as probably being first rate, especially considering it's just a keychain laser.

Does anyone know the math to figure out how many milliradians that is?

 

• Jan 25, 2008

• #2

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dmartin

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about 5 millirads

 

• Jan 27, 2008

• #3

Switch

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That would actually be less than 0.5 mRad.Probably around 0.4 if your measurments are accurate

 

• Jan 27, 2008

• #4

charleytown55il

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0.3608923727835044 using pseudonomen's calculator.

http://www.pseudonomen.com/lasers/calculators/index.html

 

• Jan 27, 2008

• #5

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pseudonomen137

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Since you have such a large beam diameter (~3mm) the divergence isn't really that amazing TBH. You can always trade off diameter for divergence, so a thick beam with low divergence, or a thin beam with high divergence, or a medium beam with medium divergence are all basically equivalent.

 

• Jan 28, 2008

• #6

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dmartin

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ohh sorry, its about .5mrads, i looked over my math and was a tens place off when converting to mRads.

I'm glad to see my math was correct except for the 10's place. (i just sort of made it up remembering what i had learned from school)