RPL-375 (Questions)

[Flashanator_500mW]

Hello...

I have two questions in regards to the RPL-375.

1): At a distance of 7km, what would the diameter of the beam be?


2): Is it possible to measure the candle power rating of a Laser like the RPL-375, like they do with spotlights. I'm just curious to know. Must be even more brighter then an advertising light.


Any input would be great, Thanks.  

 

[BlueFusion]

Re: RPL-375 (Question)

Laser power is measured in mW, not candle power.
As for distance, lemme see if I can work it out... brb with an edit.

 

[Flashanator_500mW]

Re: RPL-375 (Question)

But power in watts is diff from candlepower. Obviously lasers use very little power hence mW, but have very high brightness. And candle power is a measure of beam intensity. So id assume it would be possible.


At 7km on a clear night, would it be too bright to look at still? At that distance would the target actually see the beam or just the spot?

 

[Switch]

At a distance of 7km the spot diameter would be around 6.5 to 7 meters according to my calculations. With that huge diameter the beam wouldn't be visible at all at 400-500mW(though i guess that a RPL-375's beam would have significantly LESS power after 7 km of atmospheric impurities).

I don't think you can measure a laser the same way you measure a spotlight.Just not the same kind of light....

 

[darklandz]

well a mate of mine lives just over a KM away from me and he can see the beam of my RPL-400 shined into the sky very blatantly and bright. my guess would be, at 7KM the beam would be more than visible. not too sure on dot diameter

 

[Deleted member 10578]

6-7 meter spot size sounds about right for that distance.
I doubt someone at that distance would see the beam goign the sky, but it is possible if the conditions are right (high humidity/very light fog) and it is night time of course. As for seeing that 6-7 meter diameter spot and the distance of 7km, at night it would be easily seen, no problem. At this distance hurting someones eyes would not be an issue.
If you are talking about someone looking into the direction the laser is coming from and it is night time, seeing the emitted beam head on; the only rewuirement is line of sight (curavature of the earth). I've had military (Navy ships captain) personnel who have told me that on the open ocean, the RPL-300 had no problem being seen from a distance of 26 miles and he estimated to could easily do 40 miles or without any problem other than line of site.

Jack

 

[darklandz]

on that night it was slightly foggy more humid and my mate was lookin at the direction the beam was pointed from,(in the sky/direction where i live, from my bedroom window) of course not directly beein able to see the aperture because of all the houses/buildings inbetween but he explained the beam was 'intense' and blatanly visible.
bein able to see the laser from 26 miles is insane i guess my 400 may hit the 50 mark

 

[Cyparagon]

I don't think you can measure a laser the same way you measure a spotlight. Just not the same kind of light....

Ye have little faith. Sure ya can! I'll do it right here. Wikipedia's definition of candle power is as follows:

The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540×10[sup]12[/sup] hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.

Since all lasers have a divergence less than 1 radian (1000mRad). The total laser power is used, and this part of the definition may be disregarded. 540×10[sup]12[/sup] hertz is equivalent to 555nm (notice any significance?). 532nm Is approximately 88.5% as intense as 555nm. Therefore a 375mW laser gives us an intensity value of 332mW. 1/683W is about 1.46mW. 332/1.46 =

227 candle power

Which can also be stated as 227 lumens. candle power is luminous flux in a given direction. So a 100W incandescent light bulb may emit a total of 1500 lumens, but only 120 of those lumens will be within the area definable under the terms of candle power - 1 steradian. For a laser, X lumens = X candelas.

From this I can only draw the conclusion that the 1 million candle power flash lights are advertised like the 240mW pointers from ebay. They would have to be thousands upon thousands of times brighter than your average light bulb to obtain this rating.

 

[Flashanator_500mW]

Wow only 227 CP? Theres a high end military spotlight that has 6million CP, but yet looking into it's beam wouldnt be no were near as bright as the RPL375. Would have thought 100's of million CP rather then 227.

Anyway I have another question in regards to the RPl375.
At night time is it safe to look at the beam & the glare of the spot, or do i need eye saftey?

Later.

 

[Chris.]

[quote author=Switch link=1197977739/0#3 date=1198002778]I don't think you can measure a laser the same way you measure a spotlight. Just not the same kind of light....

Ye have little faith. Sure ya can! I'll do it right here. Wikipedia's definition of candle power is as follows:

The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540×10[sup]12[/sup] hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.

Since all lasers have a divergence less than 1 radian (1000mRad). The total laser power is used, and this part of the definition may be disregarded. 540×10[sup]12[/sup] hertz is equivalent to 555nm (notice any significance?). 532nm Is approximately 88.5% as intense as 555nm. Therefore a 375mW laser gives us an intensity value of 332mW. 1/683W is about 1.46mW. 332/1.46 =

227 candle power

Which can also be stated as 227 lumens. candle power is luminous flux in a given direction. So a 100W incandescent light bulb may emit a total of 1500 lumens, but only 120 of those lumens will be within the area definable under the terms of candle power - 1 steradian. For a laser, X lumens = X candelas.

From this I can only draw the conclusion that the 1 million candle power flash lights are advertised like the 240mW pointers from ebay. They would have to be thousands upon thousands of times brighter than your average light bulb to obtain this rating.[/quote]

Sorry but candela is not = candle power.
Candle power is an archaic unit of measurement defined as:
"One candlepower is the radiating power of a light with the intensity of one candle. This unit is considered obsolete as it was replaced by the candela in 1948, though it is still in common use. 1 candlepower is equal to about 0.981 candela. "

 

[Cyparagon]

Are you certain? Wikipedia states "Since 1948 the term candlepower was replaced by the international unit (SI) known as the candela. One old candlepower unit is about 0.981 candela. Less scientifically, modern candlepower now equates directly (1:1) to the number of candelas[1] -- an implicit increase from its old value."

The entry from Merriam Webster also reads "Candlepower: luminous intensity expressed in candelas; also : candela"

On another note, can anyone "shed some light" on how a regular 100W incandescent bulb emits only 120 candela yet a spotlight... run on batteries nonetheless can reach 1 million easily?

 

[Aseras]

candlea is visible light. MUCH of an incandescent bulb is lost to infrared. Million candlepower lights are halogen or HID so they burn hotter ( temp of the lights in kelvin and blackbody radiation http://en.wikipedia.org/wiki/Black_body )and thus more of their energy is converted into visible light.

 

[Cyparagon]

I still can't see any spot light being 10 thousand times brighter than a 100W light bulb.