do IR seansor cams need a lot of ambient light?

i'm working on setting up an ir cams to use as a sensor device for a project. since we will use projected images triggered by the sensors we want to use a low light sensor, but like the power of using a video cam as a sensor.

bought some cheap manually cams, took them apart and converted them into IR cams and they work great. (learn about this at: http://www.instructables.com/id/Infrared-IR-Webcam/)

but, though the IR cams are working well i find that they still don't work too well in low/no light.

is this an issue of the cheap-ness of these little cams, or will we find that all IR cams will need a relatively high light level just as a regular cam would?

thanks

but, though the IR cams are working well i find that they still don't work too well in low/no light

Use plenty of IR light, and they'll work fine.

All you've done is take off the IR filter - you haven't changed the overall sensitivity of the sensor.

For true low-light, you need image-intensifiers.

since we will use projected images

Won't the light from the projector be a give-away?

thanks. are there bulbs that will flood the area with IR light but not visible light?

what do you mean "projected light.. the give away"?

projected light will not be necessarily shone into the space visitors are moving in.

are there bulbs that will flood the area with IR light but not visible light

Of course, though often it is possible to see the light source as a dull red glow. Any decent CCTV security supplier will be able to sell these.

are there bulbs that will flood the area with IR light but not visible light?

IR LEDs should be less visible than filtered light bulbs. One of my favorite surplus dealers sells IR illuminator PCBs and kits.

Be warned that a couple of illuminator-equipped cameras I've seen have a faint red glow (equivalent to what you see when a visible red LED is just barely on). I believe this is because they used near-IR LEDs, and the short-wavelength end of the spectrum bell curve just barely reaches the visible.

This webpage says that typical camera sensors are less sensitive, but still somewhat responsive, to longer IR. So you might want to try using 940nm LEDs (but more of them) instead.

Ran

thanks for the info and links. my concern with the LEDs is that i intend to capture movement in a fairly large area (20' x 20') and can't believe that i could get enough LED IR to successfully illuminate the space for movement capture. i'm tempted to go with larger bulbs.

is this correct? or do you believe that i could get that kind of coverage out of the LEDs?

seems that it would take quite a number of them.\

To see the IR you will need to provide enough of it and it is entirely possible to get enough of it from a bulb, take a look at the IR torches for NV goggles, they light up on ir sensitive devices like a normal torch, I guess it also depends on the reflective ability of the object you are trying to sense too, ambient lighting and sunlight outputs oodles of it, play with an ir reciever and you'll quickly see what I mean.

You could look into matching the ir leds with an IR pass filter as a mismatch could be why you're not seeing enough IR, a hoya R72 I think would do for a start point. there is someone on ebay who would be able to provide a more specific wavelength IR filter relatively cheaply but I don't have a link I'm afraid.

removing the IR filter doesn't increase the sensitivity of the camera sensor as has been mentioned, it just increases its abilitity to capture that waveband, on the sensors where I've seen this measured its about a 5x increase at specific wavelengths and this can often be percieved as an increase in sensitivity of the sensor.

i'll be tracking people, they will not be wearing any specific IR reflective material, just street clothes.

the LED pcb's and the 5v IR lamp replacement bulbs both look interesting, haven't tried either yet.

for the moment i'm using standard cheapo web cams that have been modified to pick up IR.

the IR pass filter is a great idea.

thanks.