Forum

IR Camera confusion

#1

Hi

I’m currently working on a project where I need to track peoples bodys / bodyparts.
The general tracking etc works fine, but right now I’m using a normal webcam, and there is the problem with scene-lighting and the contour tracker…
So I was thinking of using an ir camera. But as I’m a total noob concerning cameras and such, I have no idea what I need. I think I read every single page and forum post concerning ir cameras, but I still don’t really know what camera to use. usb, firewire, using a capture card to get the real video signal… I don’t even know what connection I would need. It seems usb might be too slow, but firewire has a very limited cable length, that could be a problem. So, if any of you could point me in the right direction what camera to use I would really appreciate it! Thanks!

#2

Hi Abomb.

If you wanna go IR I recommend getting a unibrain such as this this . This camera gives progressive video which is best for tracking and is B&W which is more sensitive to IR.

You’ll need a lens that doesn’t have a IR filter on it. You’ll have to work out which lens you’ll need depending on requirements for use. i.e. target distance and target width. You’ll also need to buy the case and best to get a tripod so you can attach it to something. Also, you don’t need a power supply for it if you using 6-pin fire-wire. (Generally 4-pin on laptops and 6-pin on desktops, 4-pin doesn’t run power down the cable).

On the scale of things, Firewire and USB aren’t that different really when it comes to cable length. You can buy extenders for them anyway so you can run any length you want.

Good luck

#3

Yepp, this unibrain BW camera has really good quality.
They have a special firewire cable up to 10m length. And camera gets power through it (6-pin). And you always can put an repeater on it to double the length.
Check video and optics page for your desired focal length. Also, check links at this page.
And yes, USB is too slow as it takes massive CPU brain for decoding. And USB is sending in two directions, like for status checking, which let is slow more. Instead Firewire doesnt care and just fires data to client. Firewire is best choice.

#4

Wow, thanks for the fast replies!
I will try the camera you suggested, thanks again for your suggestions and thanks for all the info, that will definitely help me in the future too =)

#5

hi abomb

all that frank and xd_nitro wrote is correct…
I will say you my experience…

i did traking with imaging source firewire camera that is expensive and like you say they have problem of cable… the imaging source also sell passive repeater but they cost 90€ each… this camera they give you a very hi quality image … normally also more than you need doing traking… if you want to use it pay attention to buy the B/W one that don’t have ir filter…

also i use a normal usb webcam… using this kind of camera you shall pay a lot less for buy it but you will have the same problem with cable but you can use like repeater any active usb hub that they cost not so much… another problem with the usb webcam it is that you need to open it and you need to remove the ir filter that is normally on the lens or on the sensor … you have to take care removing it… it is a very little piece of glass with some red reflection…
with this camera you can not choose and change the optics

at the end right now i’m using anaolg camera b/w with a capture card…

with this camera you will don’t have more or less any cable problem they cost more than a webcam but less than a firewire you can choose the optics

anyway remember to use a ir illuminator to illuminate the traking area an put a visible light filter in front of the optics of camera… the imaging souce they sell a filter but is the same more or less of using a burned slide film…

have a good job

ciao

alessandro

#6

Thanks for your reply alessandro!
As money is not that much of a problem for the project i’m working on a firewire cam is the best solution I think.
And thanks for the info about the filters for ir/visible light and the ir lighting, I wasn’t totaly sure on that topic… =)

#7

Two quick questions ales9000… with your capture card, is there any latency? Any advice on buying capture card?

Thanks

#8

If you work in a backlight situation I wouldnt recommend an analogue cam as they have an overexposing-limiter build in to protect the CCD. As a result you have a sort of pumping of average brightness if a person/dark area is going into and out of the camera view. Its build in internally and you cant switch it of. Im talking about analogue surveillance cameras.
For this reason I switched to firewire unibrain cam. Its industry standard and build for industrial image processing. You can control everything there, depending (on your budget ;) your bought camera modell. The more expensive modells also have a sync function to syncronize two cameras.

#9

how do you mean syncronize two cameras?

#10

If you want to i.e. substract/divide/calculate two images of two cams, then this frame should be shot at the same time / millsecond. In best case. In fact, it differs very often by one or more frames. Thus you need to synchronize it. Better unibrain cams do this automatically. So, you dont have to care about this.

#11

got ya! thanks frank. interesting.

#12

So I was thinking of actually getting the mentioned camera from unibrain, but I just can’t seem to figure out where to get a filter for normal visible light for the camera.
Unibrain doesn’t have filters for sale, and I just don’t know enough about those things and can’t even google anything useful ;/ I’m also not too sure about terminology. I found several different filters for cameras, and some were named IR filters, but I’m not sure if they filter out IR or if they let only IR pass… even wikipedia could’nt help me there.
So I was hoping that someone here might know a bit more about those things than me and could help me… =)
Thanks in advance (again)!

#13

You can make your own, what I call, a daylight block filter from a few different materials you’ll find around your home and cheap on the web.

So you want a lens without a IR (block) filter so the camera sees IR. Then you want a home made daylight block filter infront of the lens to hide visible light from the camera.

I use a few layers of the fully black bits of a developed roll of film. These are bits have never had any light on them. If you look throught it at your lit computer screen you won’t see anything. If you look throught it at a lightbulb or a lit match you’ll see plenty because they both emit IR. You can take your filter a stage further and add layers of two different ‘Lee’ Light Filters, avilable on the web in a sample book that costs pennies/cents. Use Lee Filter 106 Primary Red and 181 Congo Blue.

As for mounting the filter on the lens, I’ve made a cardboard filter box for the camera that fits on over its front and has a window for the lens to look out of. Easy.

Good luck

#14

To clear your confusion:

  • Ir-PASS filter, lets IR passing, but no visivle light.
  • Ir-filter (or Ir-Block filter) will block all Ir radiation.
  • Ir-heat mirror / heat shield, is a sort of mirror reflecting Ir light to a different angle then visible light. Its glass and thus very durable for long-term installations in front of Ir-lamps.

Ir wavelengths

  • IR A is 800-1400nm, which is our used IR for IR-Cams. Take 900nm as your desired wavelength. See CCD image below. CCD are sensible up to 1000nm. (Its still visible for humans in small intensity though
  • IR B is everything between 1400-3000nm
  • IR C is from 3000-10000nm is used for thermo imaging. Here IR is being felt as heat by humans. Its the range where radiation is transferred to heat. IR-lamps radiate a lot in this range - heat lamps.

http://reductionism.net.seanic.net/CCD_TE/CCD_QE.gif

#15

Tanks again for the answers! I really like the forum and the community, it seems there are only people who really try to help.
Now I hope I know everything I need to ;)

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