comparing 405nm intensity with other colors

rocketparrotlet said:

Yes.

It was a "strong" PHR- the diode is just going weak.  It sucks.  I've tried replacing both the batteries and the lens, and that's not it.  Maybe my connections are bad.

-Mark

Click to expand...

My 190mW 6x (when it wasn't dead) seemed the same brightness than my 120mW PHR.

daguin said:

[quote author=rocketparrotlet link=1238167080/0#14 date=1238306476]Yes.

It was a "strong" PHR- the diode is just going weak.  It sucks.  I've tried replacing both the batteries and the lens, and that's not it.  Maybe my connections are bad.

-Mark

Click to expand...

Do you have an LPM?  It would be VERY odd for the power to degrade to the point that you would "notice" it?  Usually, it would fail before loosing that much output.

How long have you had it?  What current is it being driven by?

Sorry for all the questions, but your situation is different than "normal."

Peace,
dave[/quote]

I don't have an LPM, I sent it out to Jayrob to be tested when I first made it. It came out to 118mW, and the beam was clearly visible in the dark (to me), although it looked really fuzzy at the time. Now, my eyes are adapted to the beam for the most part, and while it looks more defined, it has seemed to lose brightness over time. I think this would have to do with the re-solders I had to do from the Flexdrive leads to the diode pins; they had to be done with a normal-sized soldering iron and no special tools besides a vice. They were not soldered very well to begin with. I've had it since October, and it's driven at 120mA.

-Mark

5mW of violet is pretty dim when used as a pointer, but IMO it does have a pretty visible beam at night considering it is only 5mW.

"My 190mW 6x (when it wasn't dead) seemed the same brightness than my 120mW PHR." - Spyderz20x6.

"5mW of violet is pretty dim when used as a pointer, but IMO it does have a pretty visible beam at night considering it is only 5mW." - styropyro.

I'm guessing we all see it VERY differently.

The beam looks almost gray to me sometimes. I guess it's the closest you can get to a gray laser.

-Mark

50mW of 442nm looks brighter than 240mW of 405

I had a 20mW violet that exhibited a fairly strong beam in a dark room with a bit of dark adaption.  And yes, the beam appears grey in a dark room.  In a lighted room with a bit of fog/smoke, the beam appeared deep violet.

Also, any variations in wavelength off of the nominal 405nm is going to affect visibility greatly.  And when comparing to greens, remember the beam diameter at aperture is much greater than your average greenie.  Power density will affect beam visibility as well.

Here's a list of all wavelengths photopic luminous efficacy from 400nm to 780.

660 should be ~20 times as bright as 405. However, the difference usually isn't that great because nearly everything fluoresces at least slightly under violet and blue light. Hold a diffraction grating to your eye and point various lasers at white objects.

Crossfire said:

I had a 20mW violet that exhibited a fairly strong beam in a dark room with a bit of dark adaption.  And yes, the beam appears grey in a dark room.  In a lighted room with a bit of fog/smoke, the beam appeared deep violet.

Also, any variations in wavelength off of the nominal 405nm is going to affect visibility greatly.  And when comparing to greens, remember the beam diameter at aperture is much greater than your average greenie.  Power density will affect beam visibility as well.

Click to expand...

Shorter wavelengths will also be affected more by atmospheric conditions than longer wavelengths (Rayleigh scattering).
According to my understanding, the beam of a blue or violet laser will be scattered more in the air than red, so this property could account for the more visible beam than a red pointer of equal power.

I remember a discussion somewhere about nighttime visibility of blue vs. green. Some thought that because of the shorter wavelength (and the difference in sensitivity with photopic and scotopic vision), the blue laser's beam in the sky would be brighter than that of the green of equal power.
I've never seen this myself, just a discussion I vaguely recall. :-X

here is a chart indicating laser visibility to the human eye based on wavelength.