Cheap IR testing method

[Evilution]

I was just wondering if anyone has considered using the "4 congo blue and 1 primary red" method of viewing IR?
It would give you some indication as the if your laser is well filtered or not.

 

[Evilution]

I'll take that as a "I don't know what the hell you are talking about but won't say incase it makes me look silly"

 

[rog8811]

It works for me
Regardsa rog8811

* I wonder what he is talking about?*

 

[Tallaxo]

Perhaps you could explain that to the less Knowledgeable of us (me) hehe.

Jase

 

[naplam]

Yep. What the hell is "4 congo blue and 1 primary red" ?

I suggest an alternative method: just remove the IR-cut filter from a webcam and see IR with it. If you want to filter out visible light use a photographic IR filter (Hoya R72 -lets >720nm light pass- is the most common and cheap) or use a black 35mm color film negative (it blocks much more light than it blocks IR). You can also do that to an old point-and-shoot photo camera that you don't use anymore (that way you can watch the screen on the camera instead of using a computer with the webcam). If you open up a camera with a flash be careful with the condenser, it holds a decent amount of charge even after powering down the camera, you don't want to touch it. Better still, discharge it with a screwdriver or something, you never know where it may be connected in the PCB and you could accidentally hurt yourself (actually happened to me once... it was a decent sting).

 

[paper183]

Discharging with a screwdriver isn't really much better since it'll do a huge POP sound and sparks will fly everywhere probably ruining the camera, at least that's what happened to the cheap digital cam i used as a webcam when i played in it ;D

 

[wilheldp]

I helped design a chopper circuit in college that charges up a capacitor to fire a flash bulb (basically the same circuit as in a camera, except ours had to charge the cap in about 1/20th the time as the camera circuit). When we needed to work on the circuit after testing it, we had to discharge that cap so we didn't kill ourselves. It is indeed one hell of a loud zap, but it really doesn't damage the circuit (unless you short it with another component of the circuit), the tool, or you (unless you touch the metal).

 

[Hemlock_Mike]

On my HV supplies, I use a MegOhm resistor to "slowly" discharge the caps.
My wife does not appreciate me dumping 2000 Joules instantly down here.
It kinda' lifts her off the couch !!!

Mike

By the way -- What is 4 Congo Blue ??

 

[Daedal]

"4 congo blue and 1 primary red" are the filters by... what was their name again? ** Looking ** Got it... LEE Filters. They are one of the most reputable camera filter manufacturers/distributors and their congo blue and primary red are damn near completely opaque. When you put the 4 layers of blue and one layer of red, you effectively block all the visible spectrum and are left with an IR-Pass filter

--DDL

 

[Evilution]

Spot on, I knew someone would know.

Congo blue and primary red Lee lighting filters (transparent not opaque) are 100% transparent to IR light. 4 layers of congo blue and 1 layer of primary red allows you to visibly see a small part of the IR spectrum. The blue blocks the red and the red blocks the blue but if you hold it over your eyes so no other light can get in and concentrate while your eyes adjust, you can suddenly see things in different colours depending on the amount or IR that is coming off them. Do a search on the internet for DIY IR goggles.

 

[pseudonomen137]

Spot on, I knew someone would know.

Congo blue and primary red Lee lighting filters (transparent not opaque) are 100% transparent to IR light. 4 layers of congo blue and 1 layer of primary red allows you to visibly see a small part of the IR spectrum. The blue blocks the red and the red blocks the blue but if you hold it over your eyes so no other light can get in and concentrate while your eyes adjust, you can suddenly see things in different colours depending on the amount or IR that is coming off them. Do a search on the internet for DIY IR goggles.

Interesting idea, but VERY DANGEROUS. The idea is basically making your pupils dilate, taking in a lot more light to try to see the IR. IR lasers are already usually pretty dang powerful. This method will effectively reduce the amount of power needed to screw up your eyes.

Holding it over your camera on the other hand will work. Film negatives or laser goggles also work well for the task. That is assuming the camera's IR filter isn't effective enough to block the IR by itself though.

 

[Benm]

That is assuming the camera's IR filter isn't effective enough to block the IR by itself though.

That's a safe assumption really... IR filters in cameras usually do a fine job for their purpose (making photos with natural colors), but do pass enough IR to easily see the ouput of an IR led in a remote control and such. Test it with that if in doubt.

Btw, never fire a laser into the lens of a digicam, the more powerful ones can easily damage the sensor leaving you with a big spot/stripe of dead pixels.

 

[Daedal]

I take it you've tried that Ben?

I'm afraid I did too... :-[ just cuz I was curious... : LOL ;D

--DDL

 

[ericab]

i was just browsing my new favorite laser website; and i found these:

http://www.roithner-laser.com/IR-Cards.htm

(check the ones towards the bottom)

-eric

 

[Benm]

I take it you've tried that Ben?

Damaging a camera by shining a laser into it?

I havent tried myself, but i've seen some pictures from a camera from someone who did (with a 100 mW-ish DPSS). Every frame had a couple of dark stripes in it - apparently the individual sensors get fried, but the CCD chip as a whole remains functional...

Interesting, but a bit of an expensive experiment to reproduce