question about blu ray visibility

[CL_]

ok, so how many mw of blu ray would be needed to have the visibility of a 5 mw green? how about a 650 nm 5 mw red?

 

[FireMyLaser]

560 nm is yellow-green light

 

[jayrob]

ok, so how many mw of blu ray would be needed to have the visibility of a 5 mw green? how about a 560 nm 5 mw red?

I just did a few comparisons. (dark room) Visually, my 46mW 405nm blu-ray beam, is very close to a 5mW green beam. The 5mW beam is still a little brighter. Now, my 473nm 40mW RPL beam, is brighter that a 15mW green! Yeah...the RPL is totally awesome. But, so is the 63mW's of violet! The florescence at that power is mesmerizing...
Jay

 

[chimo]

Here is an eye response chart. Trace your wavelengths up and to the left axis and compare the numbers.

 

[CL_]

ya, i meant 650 nm

 

[marks47]

I think that eye response chart is why they tried to paint fire engines that horrible shade of green for a while!

 

[leukoplast]

There still is green ones out there, I see them all the time.

 

[styropyro]

My 5-10mW Blu-ray's dot isn't very bright, a little brighter than a 5mW red, but the beam at night is pretty bright, I'd say about half as bright as a 5mW green to me. But unlike the green laser, the Blu-ray's beam just looks gray, you can't even tell that it is violet.

 

[Schrecken_Licht]

Eye response to color has to do with light sources (additive color) rather than reflected light (subtractive color)- something painted green won't necessarily appear any brighter than something painted yellow or red - at least in bright light.

 

[CL_]

i wonder why the beam is kinda bright but the dot isnt?

 

[styropyro]

i wonder why the beam is kinda bright but the dot isnt?

I really don't know why, but the beam is easily brighter than my DIY red which is over 100mW. Some people may see different colors slightly different though. Maybe it could be flourecing(sp?) off the dust particles in the air?

 

[F1SportsFan]

Noob question alert: Would the PS3 BluRay laser (~38mA) work good in a business setting? I.e. pointing things out during presentations in lit conference rooms? All the posted pics I have seen are night shots. Thanks!

 

[rog8811]

Noob question alert: Would the PS3 BluRay laser (~38mA) work good in a business setting? I.e. pointing things out during presentations in lit conference rooms?

I use mine all the time for that purpose, it is not as bright, to the eye, as a similar red but certainly bright enough to be seen.

Regards rog8811

 

[Ace82]

405nm is not so visible to the human eye, correct? When taking pictures of the blu-ray beam, it seems much more defined then in real life. The camera picks up on it very well. Compared to green, blu-ray and red apear WAY less intense. So my question is; does the violet 405nm laser produce more power then it appears to our eye? Why does IR pose such great threats to our eyes? In comparison to Ir, should we caution "invisable" laser radiation from the blu-ray too? :-/

 

[Scriabin]

405nm is not so visible to the human eye, correct?  When taking pictures of the blu-ray beam, it seems much more defined then in real life.  The camera picks up on it very well.  Compared to green, blu-ray and red apear WAY less intense. So my question is; does the violet 405nm laser produce more power then it appears to our eye? Why does IR pose such great threats to our eyes?  In comparison to Ir, should we caution "invisable" laser radiation from the blu-ray too?   :-/

Yes, the 405 nm(almost UV) is at one of the limit of visible light, so is the same thing of near IR in this case.
Another thing is that the cornea is a bit fluorescent to several UV wavelenght, and so at 405 nm tends to absorbs a few amount of light(but it remains dangerous!), so for the eyes IR are a bit more dangerous than UV.
The IR wavelenght tends to be absorbed totally up to 1500-2000 nm by the cornea, so these laser are called "eyesafe"(co2, er:yag, ho:yag etc).
Near-IR should be considered as visible light, since it passes completely through the eyes.

 

[flogged]

i wonder why the beam is kinda bright but the dot isnt?

There are a few reasons for this.

First, shorter wavelengths of radiation are scattered more by the atmosphere. This is why the sky appears blue - see Rayleigh scattering (http://en.wikipedia.org/wiki/Rayleigh_scattering)

from the wixxi:

When one looks at the sky during the day, rather than seeing the black of space, one sees light from Rayleigh scattering off the air. Rayleigh scattering is inversely proportional to the fourth power of wavelength, which means that the shorter wavelength of blue light will scatter more than the longer wavelengths of green and red light. This gives the sky a blue appearance. Conversely, when one looks towards the sun at sunset, one sees the colors that were not scattered away — the longer wavelength, red light.

So violet light will scatter even more than blue, enhancing beam visibility from all directions.

I'm also assuming if you're admiring the beam of your bluray you're doing it in a dim to dark room. The bluray looks much more impressive to a dark adapted eye because both your rod cells (most numerous cell in the retina, responsible for night vision in dim environments, under starlight, etc) and your blue cone cells can 'see' violet. Whereas with a red laser (at night) only your red cone cells are really sensitive to it.

However in good light the graph Chimo posted is correct. Overall your eye is just not very sensitive to violet... so unless you've got a 6x bluray they look most impressive at night.