CCD cameras and nighvision/IR LEDs?

[NRG = mc²]

Hi guys,

I've got a CCD camera which appears sensitive to IR (pointing a TV remote at it shows the IR LED blinking), I'm wandering if I can just get a perforated PCB, mount a few IR LEDs on it and use it as nightvision?

If so, does anyone know what specs are required for the LEDs (wavelength & brightness) and approx how many would be needed for a range of 4m? I have looked for info on the subject and it seems 880nm wavelength is recommended but I don't know how perful/how many LEDs I need.

Any ideas?
Thanks

 

[NRG = mc²]

Also, would the cluster of LEDs need to be a particular shape or placed in a particular location with respect to the camera?

 

[jtr1962]

For visible LEDs brightness is measured in mcd but this spec is meaningless for IR LEDs which emit at invisible wavelengths. Thus, they are generally rated in mW and beam angle. For a given mW output a smaller beam angle will be "brighter" but will have a narrower field of vision.

I would say maybe a half dozen to a dozen 5 mm LEDs driven to spec should provide adequate brightness. Mount them with the rounded end parallel to the direction the camera lens is pointing (same as visible LEDs would be mounted). As for sources you might try eBay, or just salvage some from old TV remotes. If in doubt about the maximum current just limit it to 20 mA by putting resistors in series with the power supply. I think Vf for most IR LEDs is in the range of 1.8 to 2.2 volts.

If I find any more info I'll post again.

 

[NRG = mc²]

Thanks for your help jtr1962. I notice that the quoted power varies significantly from type to type, with the brighter IR LEDs in the 35mW range.

I will try a few but pointing three remote controls at the wall 10 inches away while simultaneously transmitting in a dark room doesn't appear to illuminate the wall at all when viewed through the camera so I guess the LEDs found in remotes are simply not powerful enough?

 

[jtr1962]

I will try a few but pointing three remote controls at the wall 10 inches away while simultaneously transmitting in a dark room doesn't appear to illuminate the wall at all when viewed through the camera so I guess the LEDs found in remotes are simply not powerful enough?

Not necessarily. The IR LEDs in the remotes are pulsed so that they send out an appropriate signal to the receiver. Thus, they're not operating at 100% duty cycle. They may also be operating at way less than rated current in order to conserve batteries.

I'll see if I can find the specs for the IR LEDs used by the taxicams that I repair. I think they use about 15 or so LEDs.

 

[NRG = mc²]

Please do.
Thanks

 

[jtr1962]

Part number is SFH-487-3. The camera uses 21 of these in three series strings of 7, driven at ~100 mA. The only data I could find on them was Vf=1.5 @ I=100mA. Since most LEDs these days are about 10% efficient (state of the art in a lab is around 35% efficient) at converting electricity into light of some wavelength this would put the output of these LEDs at around 15 mW each, and the total output of the array at around 315 mW. I'm guessing that any IR LED array which adds up to a few hundred mW in output should work fine for you. Just make sure to use resistors or a current regulator to keep the forward current within specs (this seems to be 100 mA for most IR LEDs as opposed to 20 or 30 mA for visible LEDs).

Yes, most of those B&W CCD cameras are sensitive to IR light which makes a camera coupled with an IR array a good night vision device.

 

[NRG = mc²]

Thanks for the info. I've found a place that stocks them.

The camera is actually a color one, will that not work?

 

[jtr1962]

It probably should. I think color cameras use the same CCD devices as B&W ones, but selectively filter the red, green, or blue light going to the CCD depending upon whether it is a red, green, or blue pixel. The filters probably let through enough IR so that the camera remains sensitive to that also. The only sure way is to try it and see but I don't see why a color camera wouldn't be at least somewhat sensitive to IR.

 

[NRG = mc²]

Well it certainly sees the flashes of a remote control pointed at it quite brightly...

 

[mubs]

I stumbled acroos a site today; they sell IR Illuminators.

Allows B/W cameras to see in total darkness for up to 35'–40' distance. Activates in low-light conditions with 68 illumination sensor Illuminators at an angle of 50°–60°. 0 LUX illumination (850nm;non-visible to the human eye). Compatible with most B/W cameras. Indoor/outdoor use; water resistant. Includes 12 volt DC power, Y connector and metal mounting bracket.
Pricing $132.98 ea

Here, near the bottom of the page.

 

[NRG = mc²]

Thats a little more than I was expecting to pay...

I've built the illuminator with 15 leds but not had time to test it properly. A quick test seems to show that it is way too weak to light anything beyond 1 ft. But that was a quick test with my Canon A30 and possibly with an incorrect voltage for the LEDs. I will test it thoroughly when I get time.