Travel Photography - How Do I Record Video of an Infrared Beam

I always come to FT with the questions I cannot solve. What does this have to do with travel photography? Well the thing I want to film travels from one place to another. Also I am wiling to travel in order to film this.

I need to record some video of a beam of light in the near infrared range. The characteristics of the beam are:

A continuous beam at less than 10 mW at a wavelength of 785 ±15 nm with a beam diameter of 80 mm at the sending end spreading out as it travels to the receiving end to about 200 mm.

Does anyone know how I would do this? I have tried using an infrared filter on a DSLR to record a still image with no result. If this requires hiring someone with specialized equipment, I am in the DFW area. I could also bring the equipment to another location if the cost is not too high.

You'll need dust in the air. Unlike in Hollywood beams in the air emit effectively no light unless the air is dusty.

Infra-red film is also light sensative. The filter is used to ensure only 700-900nm light passes through. There is also a shift in focal length due to this shift in wavelength. Older lenses have a red dot to show this shift.

Any professional photographer should be able to help you out. Preferrably an industrial or medical expertise.

Digital cameras mostly have IR blockers in them as some clothing becomes transparent under IR. "Shine" a remote at your camera with the filter on it and look if you can see the "light" from the remote. If you can, then use chalk dust or other fine particle dust to illuminate your beam.

Digital cameras mostly have IR blockers in them

Bingo

I've done this project (http://www.geektechnique.org/projectlab/254/how-to-turn-a-digital-camera-into-an-ir-camera.html) several years ago with mild success. I damaged the CCD slightly during disassembly because my camera wasn't as easy to disassemble.

For video I've recorded the output of near-IR laser diodes using an old CCD-pickup video camera (mini-DV tape). Like others have said you need something to reflect/refract some of the photons in the air to your pickup. Dust or chalk will work but can be messy -- In a darkened room I used a ultrasonic cold mist humidifier to cover a larger area with a fine mist spray bottle of water to highlight different areas along the beam to show the divergence.

You'll need dust in the air. Unlike in Hollywood beams in the air emit effectively no light unless the air is dusty.

I thought about using a smoke generator such as used at Halloween. Do you think that would work?

For video I've recorded the output of near-IR laser diodes using an old CCD-pickup video camera (mini-DV tape). Like others have said you need something to reflect/refract some of the photons in the air to your pickup. Dust or chalk will work but can be messy -- In a darkened room I used a ultrasonic cold mist humidifier to cover a larger area with a fine mist spray bottle of water to highlight different areas along the beam to show the divergence.

Where would I find a video camera such as this? Are these older units?

I thought about using a smoke generator such as used at Halloween. Do you think that would work?

I would think so but I have no experience actually doing that sort of photography.

Robbing a museum?

Robbing a museum?

It would probably be easier. But no I am trying to film the beam that goes back and forth between two FSO - Free Space Optic units for a video for a class I teach.

A simpler workaround is that I would forget about trying to film the actual IR beam. Instead, use a small hidden visible wavelength laser pointer to create a new beam in nearly the same position and direction as where the original beam would be, then film that, using a hand sprayer with a fine mist of water to reveal the beam against a dark background. Then explain in the narration that this is what the beam would look like.

Hopefully this would convey the point without the pain of having to film and deal with the IR issues. I know it won't be as cool as doing the real thing, but if it avoids a lot of trouble...

I have tried using an infrared filter on a DSLR to record a still image with no result.

You have it backwards. You need to remove the IR filter inside the camera, not add one.

Here is a link on how to do it with Canons (http://ghonis2.ho8.com/rebelmod450d1.html).

Well almost a museum -- ebay!

Try searching for an old Sony Hi-8 camcorder with NightShot. IIRC they used 830nm or so for illumination but I think the pickup should see the higher frequency especially since some folks sell 780nm bandpass filters which are also good for spotting ghosts :p

lol... http://www.ebay.com/itm/780nm-INFRARED-IR-FILTER-Indoor-XRAY-GHOST-HUNTING-Lens-Choice-25mm-30mm-37mm-/370617645215

p.s. you don't need the filter, just record in a darkened room

You have it backwards. You need to remove the IR filter inside the camera, not add one.

Here is a link on how to do it with Canons (http://ghonis2.ho8.com/rebelmod450d1.html).

No, he had it right. The confusion is over the use of the word filter. A glass IR filter on the outside end f the lens is really filtering OUT visible light, i.e. only IR passes through. The IR filter INSIDE the lens does the opposite by filtering out the IR and only passing visible light.

Thanks for the ideas. Keep them coming as I plan to try all of them.

First, I am going to try the webcam take out the IR filter, put in the two pieces of negative film as a filter, idea. This is assuming I can find a webcam I can take a part. None of the current ones appear to have screws holding them together. I bought two $8 ones to try this on.

Well almost a museum -- ebay!

Try searching for an old Sony Hi-8 camcorder with NightShot. IIRC they used 830nm or so for illumination but I think the pickup should see the higher frequency especially since some folks sell 780nm bandpass filters which are also good for spotting ghosts :p

lol... http://www.ebay.com/itm/780nm-INFRARED-IR-FILTER-Indoor-XRAY-GHOST-HUNTING-Lens-Choice-25mm-30mm-37mm-/370617645215

p.s. you don't need the filter, just record in a darkened room

I see some of these on eBay. How sure are you that it will record light in the 785 nm area?

No, he had it right. The confusion is over the use of the word filter. A glass IR filter on the outside end f the lens is really filtering OUT visible light, i.e. only IR passes through. The IR filter INSIDE the lens does the opposite by filtering out the IR and only passing visible light.

Right but if he is using a DSLR, then is has an IR filter on the inside. So I guess what he has to do is remove the IR filter inside the camera and add an IR filter to the front of the lens.

I see some of these on eBay. How sure are you that it will record light in the 785 nm area?

I can't guarantee any results, but when I was working in the video/optics field 20 years ago I often used consumer grade video cameras to record things in the 750nm band. You do have to get one where you can disable the IR filter (known as "NightShot" by Sony, or something "Zero lux" by other manufacturers). When you'd enable NightShot the camera would activate a few near-IR LEDs to paint the area which I think were at an even lower frequency than your 780 requirement.

Of course the IR will just appear as a white flashlight in the camera, but I guess that's what you're going for.

These days "ghost hunters" still use this crap and you can get more info & techniques through google.

Sample link http://www.ghost-tech.com/infrared_video.php which supports that these CCDs can pick up anything from visible light to as low as 1,000nm IR.

Really chuckle at some youtubes which purport to show paranormal activity when it's obviously backscatter, multi-path, or other stuff in the room. Boo! I'm the clock-radio neon bulb.

As way of an update I believe I have found the perfect device for recording this beam. It is a MicronViewer 7290 Infrared Camera by Electrophysics. Now all I have to do is find someone who has one as they are way too expensive to buy.

As way of an update I believe I have found the perfect device for recording this beam. It is a MicronViewer 7290 Infrared Camera by Electrophysics. Now all I have to do is find someone who has one as they are way too expensive to buy.

eBay? One there is still only at $199 :D

eBay? One there is still only at $199 :D

Don't be so discouraging. I have been working on this for a while.

Heh, how about we take up a collection from all of the FT members. Then I could buy my own. :)

I know everyone has been waiting for news as to my progress on this project. I can report that with the assistance of the faculty at the University of Texas at Dallas I have captured the unit search pattern sent by FSO devices in order to find their partner. This is a circular beam pattern. Quite fascinating to watch.

Now I need to capture the beam as it carries data back and forth. For this I need particles in the air between the two units for the beam to reflect off of. I have tried chalk dust and a small hand steamer with no results. What will put large particles floating in the air for a while?

in order to visualize the beam, you need to think about two different problems:

1. You need particles that reflect infrared. Dust and smoke may reflect visible light but absorb infrared, depending on the IR wavelength and properties of the particles.

2. once it's reflected, it will still be infrared, so the same detector problems arise.

As others have suggested, this is a problem that might best be handled by simulation with a visible beam.

The comments on filters are spot on. Most solid state sensors in cameras and camcorders are IR sensitive. In order to record scenes that look like what we think they should look like, the cameras must filter out IR, which they do with filters just in front of the sensor. (that's what you clean when you clean the "sensor" on a dslr.)

When you want to record IR, you need an unfiltered sensor. If you want to ONLY record IR, you need a filter in the light path that will block visible light but pass IR. Depending on your setup though, you may not need the IR pass filter. For example, if you image the beam in a dark room, there's no visible light to interfere.

The problem with IR pass filters is that unless you spend a fortune for a specialty filter, it will block visible light and a lot of the IR too.

I have a camera that records infrared light. I have made several recordings of the beam by reflecting it off various surfaces to the camera. The only remaining view I want to capture is one perpendicular to the beam. I have captured a small section of this, about 4 mms long using an infrared reflector card. I need a much longer section of at least one meter. The only way to do this as far as I know is to place enough particles in the air that the beam reflects enough to allow the camera to see the beam. So far I have found nothing that reflects enough, thus the update to this thread.

The faculty member at the University of Texas at Dallas who loaned the camera to me suggested something wet. I tried every spray in the house with no result.

Have you thought about using a water fogger?

I will try a water spray bottle. I have borrowed a fog machine such as you use for Halloween to try as well.

I have had some success. Using an infrared viewer from Electrophysics with the CCD camera attached, while spraying Fantastik cleaner into the area of the beam I have captured a few seconds of the the beam. I am quite pleased. :D

To wrap this up in case some other nut tries to do this the best result was achieved by spraying Fantastik into the area of the beam. The image was captured with a CCD camera attached to an Electrophysics 7215 Infrared Viewer. This combination produced several very good images of the beam. In these it appears as bursts of light.