IR illumintor to use with Bosch LTC 0630 Day/Night cam?

[sequoia 0]

I've ordered a Bosch LTC 0630 WDR 1/2" CCD cam to put in place of my older cam that fails miserably at capturing license plates-- especially at night. The older cam is not day/night although the ambient lighting is pretty good. (Very well lit parking lot.)

 

I would like to add an IR illuminator to shine at the departing license plates but am unsure of whether to use the 850NM or the 940nm models. My target license plates are about 50' away, and only in a very tight area so I don't need a beam with a wide spread. (The exit is via a single lane only so the focus can be very tight.)

 

Since the illuminator will need to be mounted at ground level, where someone could reach it, having it be completely or almost completely invisible would be desirable. I've heard that the slightly visible units work much better with the camera (850nm), but I don't have any practical experience with either. And, I am assuming that the camera must be forced into night B/W mode for the illuminator to have any effect?

[cglaeser 0]

Sensors that are IR sensitive are typically more sensitive at 850nm. My rule of thumb based on conversations with camera manufacturers is roughly 50% at 940nm compared to 840nm, though I have not done any testing and YMMV.

 

Best,

Christopher

[rory 0]

Yeah its supposedly 20-30% loss at 850nm from 750nm, and approx 50% loss at 940nm from 750nm.

Ive used both and the 940nm seemed like it was around the 20-30% lower from the 840.

Ofcourse it will vary from camera to camera and IR to IR.

[sequoia 0]

Thanks.

 

One more question-- is the life of the IR illuminator an issue? Should I plan to let it run all night, dusk to dawn, or only light up upon motion detection?

[cglaeser 0]

One more question-- is the life of the IR illuminator an issue? Should I plan to let it run all night, dusk to dawn, or only light up upon motion detection?

 

Again, this is just my rule of thumb based on my conversations with LED engineers, but I would expect a quality IR to degrade to 50% output in 10 years of night use. A lot really depends on features like heat management, so your mileage will vary greatly. If you can build a reliable motion detection system, I think I would opt for that.

 

Best,

Christopher

[cglaeser 0]

BTW, the more sophisticated license plate systems are starting to use IR flash. Using a very short bright flash can essentially eliminate motion blur of fast moving cars.

 

Best,

Christopher