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# Laser projector

#### James R

##### New member
Hi Guru,
I am building a laser projector using Red, Green and Blue laser diode to generate 200 lumens.
How to calculate each of laser diode power to make 200 lumens?
My understanding is that if each laser diode provides 66.6 lumen, the total will be about 200 lumen.
Is it correct?

Best,

James

##### Well-known member
LPF Site Supporter
Hi,
Lets go home and do it again, meaning first post in the welcome section . A little about your self , and your location so folks get to know you.
They will be more willing to help you out . Anyway welcome and be safe , go to welcome section now buddy.

Rich

#### James R

##### New member
Please direct me to the welcome section to say "Hello".

#### hakzaw1

##### Well-known member
Its the section marked "Welcome /Newcomers'' not hard to find-

The output from a laser projector is measure in mW.
the place to match them up is 'Chroma' Or find it in the sig of many here.
it is NOT evenly done== tons of red and blue ad needed to balance just a little G.

There is a thread here that IF you read you will have much less Qs.

good luck --len

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#### hakzaw1

##### Well-known member
Please direct me to the welcome section to say "Hello".
you can' t get there from here-JKing -- to send you we DO need to know where you are..
anything like James R sez hello from Portland Or (example ) would make a super title.

#### styropyro

##### Well-known member
lol at the posts demanding this dude to share his location without giving any help at all.

Anyway, what you are looking for is the luminosity function. This gives you a method to calculate the luminosity of a light source of a given power and wavelength distribution. https://en.wikipedia.org/wiki/Luminosity_function Luckily it's much easier to do these calculations on laser sources than broadband light sources.

You can find several sources online that will walk you through a luminosity calculation, but I'll give you an example. Say I want to know how many lumens my 2W 450nm laser is. I find 450nm in a luminosity function table (or estimate it from a graph) and I get 0.103903. So I take that times the laser's power times the constant 693 lumens/watt and I get (0.103903)*(2W)*(693lumens/W) and I get 144 lumens.

There are also calculators online that can probably do the calculations for you.

#### paul1598419

##### Well-known member
It depend on what you are trying to accomplish here. If you need to mix the light to make white, then the relative brightness of each laser is important to know. But, if you only need 200 lumens regardless of the perceived color of the light, then you might as well use only one laser.

GSS

#### RedCowboy

##### Well-known member
It depend on what you are trying to accomplish here. If you need to mix the light to make white, then the relative brightness of each laser is important to know. But, if you only need 200 lumens regardless of the perceived color of the light, then you might as well use only one laser.
Paul you ignored the OP's question, he said he wants RGB and a total of 200 lumens, also he asked if 66.6 lumens each RGB would yield 200 lumens combined, I think it could yield higher than 200 lumens, what do you think ?

OP's post >
I am building a laser projector using Red, Green and Blue laser diode to generate 200 lumens.
How to calculate each of laser diode power to make 200 lumens?
My understanding is that if each laser diode provides 66.6 lumen, the total will be about 200 lumen.
Is it correct?

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#### Cyparagon

##### Well-known member
Why have you chosen 200 lumens as a design specification?

#### hakzaw1

##### Well-known member
Why have you chosen 200 lumens as a design specification?
I wondered the same thing.. trying to make exactly 200 may not be very easy and it will not be very bright. & may cost more that a cheap one Plug n Play .(not even including your labor)
AND for between \$3 and \$5 you can buy 3 (RGV) pointers that very likely will be around 150-200 mW combined--you will be limited by duty/rest cycles but we no longer worry so much w/ them being so cheap'
Slightly bigger and no expensive aaa batts (use 18650s)AND longer duty w/ them being bigger--they are the '300' or '500' series--one good Ebay seller is a member here--very fast delivery considering he is in China.
'blab1391' ONLY buy the recahrgeable batts BUT never w/ a laser in same box COMING from outside USA.

good luck. hak