help in making infra red light!

[john Smith]

Hello,

I hope this is the right place to post this message as I wish to know is it
possible to make an infra-red flood light using LEDs.

I recently purchased what I thought was one form maplins for 60 GBP but it
turned out to be more of a spotlight, lighting up only a small area of

my drive., I want to know would it be possible to make a light that could
cover a wider area using i/r led's, possibly the ones you can buy for

maplins for a couple of pence each.

I'm sorry if I have posted this in the wrong place, but any advice would be
gladly received


Thanks in advance

 

[John Popelish]

Hello,

I hope this is the right place to post this message as I wish to know is it
possible to make an infra-red flood light using LEDs.

I recently purchased what I thought was one form maplins for 60 GBP but it
turned out to be more of a spotlight, lighting up only a small area of

my drive., I want to know would it be possible to make a light that could
cover a wider area using i/r led's, possibly the ones you can buy for

maplins for a couple of pence each.

I'm sorry if I have posted this in the wrong place, but any advice would be
gladly received


Thanks in advance

It is certainly possible, but it takes a lot of LEDs, since each puts
out only a milliwatt or so of light energy. It is often more
practical to cover a large incandescent lamp (250 watt brood lamps,
for example) with an IR long pass filter when a big flood is needed.
Most theatrical color filter gels pass IR, so using a few different
deep colors, like blue and red, block most visible, but pass IR.
These are fairly cheap in large sizes.

 

[Eric R Snow]

Hello,

I hope this is the right place to post this message as I wish to know is it
possible to make an infra-red flood light using LEDs.

I recently purchased what I thought was one form maplins for 60 GBP but it
turned out to be more of a spotlight, lighting up only a small area of

my drive., I want to know would it be possible to make a light that could
cover a wider area using i/r led's, possibly the ones you can buy for

maplins for a couple of pence each.

I'm sorry if I have posted this in the wrong place, but any advice would be
gladly received


Thanks in advance
SEE BELOW
Hi All,

I'd like to assemble a infrared-pass filter over an IR floodlamp (possibly
up to 250 watts). The goal is to filter out visible light --- to
illuminate an area monitored by IR sensitive cctv cameras.

This is an outdoor device. The assembly would have to be sealed against
weather and have some form of heat sinks. Still, I'd need filters (glass?)
capable of handling significant heat. Any thoughts, pointers and
recommendations would be appreciated.

In the 1970s, we used Kodak Wratten #87 filters, which could be bought
in 10cm by 10cm sheets for not much money, but Kodak stopped making
them. The story was that then new environemntal regulations had
rendered manufacture of the necessary dye too expensive for the
market.
(#87 filters may be back; I haven't checked in years.)

The alternative was actually better than Wratten #87 filters, which
were
expensive, fragile, and tended to bleach under the light.

What we used instead was a tripack of ordinary theater-light filters,
such as those made by Rosco. These filters are used in front of a
1000-watt lamp, and only ~4% of that is visible light. Of necsssity,
all theater-light filters pass infrared, to avoid combustion.

So, what one does is to stack three complementary filters, such that
all
visible light is blocked, allowing only infrared to pass.

What you want are generically called "plastic gels" in the stage
lighting trade, and are made of dyed plastic film, not gelatin. The
Rosco product is "Roscolux". <http://www.rosco.com> I don't recall
the exact colors we used, but it wasn't hard to figure out. One just
got (for $15) a sample book, and tried combinations out.

There are a number of competitors as well.

There are glass filters that pass IR and block visible, probably made
by
Schott and perhaps Hoya, but these were too expensive for us. Theater
filters are something like $6 for a 20" by 24" sheet, and widely
available.

Joe Gwinn

 

[spudnuty]

If you call your local Rosco dealer you can get a "Roscolux" sample
book sent to you for nothing if you are in the "trade" (wink, wink).
The book is quite cool as each film has a graph of its transmission vrs
wavelength. You can pick the wavelengths you want passed by stacking up
the graphs. I made a nice homemade safelight doing this.
Also Bill Beaty also did some cool research at:
http://www.amasci.com/amateur/irgoggl.html
He used: " "Congo Blue" (Lee #181, or Rosco #382) costs maybe $8 for
24" sheet
Optional: sheet of "Primary Red" filter gel (Lee #106 or Rosco #27)"
and made a pair of goggles for viewing IR.
Richard

 

[Rich Grise]

Hello,

I hope this is the right place to post this message as I wish to know is it
possible to make an infra-red flood light using LEDs.

I recently purchased what I thought was one form maplins for 60 GBP but it
turned out to be more of a spotlight, lighting up only a small area of

my drive., I want to know would it be possible to make a light that could
cover a wider area using i/r led's, possibly the ones you can buy for

maplins for a couple of pence each.

I'm sorry if I have posted this in the wrong place, but any advice would be
gladly received

Well, LEDs generally have a fairly narrow beam too, so you'd need a
bunch of them in an array all aimed a little differently. And you'd
need a bunch of them to give any reasonable level of illumination.

Or, you could find some kind of IR transparent diffuser, like you
see on headlights or LV yard lights, to spread out the beam, or look
for a "full-page magnifier" (in an office-supplies store, or on-line),
and if it's IR transparent, it should spread the beam also, albeit
possibly not as evenly as an actual diffuser.

Good Luck!
Rich

 

[Pooh Bear]

It is certainly possible, but it takes a lot of LEDs, since each puts
out only a milliwatt or so of light energy. It is often more
practical to cover a large incandescent lamp (250 watt brood lamps,
for example) with an IR long pass filter when a big flood is needed.
Most theatrical color filter gels pass IR, so using a few different
deep colors, like blue and red, block most visible, but pass IR.
These are fairly cheap in large sizes.

Going back to my lighting days, I recall that deep blue filters in front of high
wattage lamps used to 'char' from the absorbed energy !

Graham