Cctv able to read number plates

A dummy camera high up may deter them.

DIY solution could be a raspberry pi ocotocam, £40 I've got one i'm trying to use for a similar job, when I have time

n Wednesday, June 6, 2018 at 7:58:52 PM UTC+1, Cynic wrote:

he local hall. Lately there's been a problem with boy racers gathering afte r dark in the car park and antisocial behaviour ensues.

esumably caused by the direct reflection of the IR. Has anyone had success in capturing readable images of number plates after dark using economic cam eras? I'm guessing the use of a non illuminated camera with a separate illu minator from an angled location might solve the reflection washout of the i mage but the hall doesn't want to spend funds without being sure it will wo rk.

The real problem is the light source being in the same position as the camera. Very difficult to sort with a cheap setup.

It's not. Having the light source - in this case infra-red - beside the lens means it reflects straight back into the lens.

If the IR illumination and camera were perpendicular to the number plate I would agree, but that would be unlikely. The only other issue is with snow/rain/fog where there is significant local reflection.

The contrast between white and black on a number plate is significant, it really is a question of getting the right illumination and correct shutter speed.

Some illegal number plates try and filter the IR wavelengths to reduce the contrast, but they are still readable in the visible.

I might be more tempted to use white or yellow illumination, which would also act as a deterrent.

Which is the point of retroflective number plates. AIUI, the problem is avoiding other light sources from reflecting off the outer face of the plate. That is why they fitted a filter matched to the wavelength of the IR emitters to the number plate camera on my industrial estate.

In article , Cynic scribeth thus

I'd have a look at the Hikvision range of cameras, bought one to evaluate recently been very impressed with it for 80 odd quid. I believe they do a ANPR one and or the recorder that goes with it etc..

Have a look on Youtube, several demo examples on there..

Car number plates reflect light from more than one direction.

Yes - that would do it. Or provide a soft light which isn't thrown back at full strength straight down the lens. Impractical to do, though.

By law the letters shouldn't, nor should any coating be added to make the letters retro-reflective. So the contrast should be huge.

But reflecting the light source straight back down the lens also gives you a problem with auto exposure. Not much point having a picture where the only thing you can see is the number plate.

For Cynic's purposes the solution might likely to be more than one camera. One with exposure specifically to capture the number plate, and another to see what was going on.

There are cameras than can cope with a huge dynamic range, but they're not cheap.

Don't be tempted to overdo it. The DfT recommendation is that individual speed bumps should not be higher than 75mm, to avoid possible damage to ordinary cars.

If the car park is suitable, breaking it up into separate parking areas with parking kerbs will deny them the open flat area they want.

e.g.

I've just been down to the hall in the next village to look at speed bumps they installed. The 75mm variant is what they have and the lowered suspensi on cars were seen arriving, trying to enter then going away (probably to ou r more accessible car park). Seems worth trying as a non technical method. A 3 metre strip across the entrance is available as a kit on eBay.

I said that in the bit you snipped.

Put it down AFTER they have entered the car park.

One way spike strip after hours would be better.

That's the problem with many solutions. Not cheap enough.