Why can't I read this license plate?

[Scruit 0]

What is the resolution of the camera that is looking at the white van?

 

 

EDIT: That is some NICE video! What is the camera and DVR you used??

[Guest]

What is the resolution of the camera that is looking at the white van?

 

 

EDIT: That is some NICE video! What is the camera and DVR you used??

 

 

We dont use this camera as we have better but this was choosen here becasue of size and color.

 

Camera:

Imagesensor 8.5mm (1/3") CCD

Signalsystem PAL

Sync hor. 15,625Hz, vert. 50Hz

Pixels hor. 500, vert. 582

TVL 480

Lens 1:2.0/3,6mm/6mm/8mm/12mm

Min 0.05 lux

Signal/noise level > 50dB

Video 1Vpp/75Ω

Temp. -10 °C til +50 °C

Power 230V˜/50Hz/10VA

Size Ø 32mm x 130mm

Weight 2,2Kg with PSU and 30m cable

Other IP68, AGC, BLC

 

The DVR is a PC based using hardware compression cards, we dont use these cards anymore (Recording: Mpeg1 CIF @ 25FPS every channel up to 16) we have better now (Recording: H.264 2CIF/4CIF @ 25/12FPS every channel up to 64). But software pretty much the same, can use it on many different HW cards. The software is our own.

 

It does the job quite well.

 

 

JD

[NVW3Navy 0]

just a side note, there are license plate covers available on the market today that will disrupt most cctv images. these covers reflect light at odd angles, visually to the naked eye they just look like a tinted cover, but CCTV is all but useless.

[scorpion 0]

Those plate covers can be defeated. Easy to do. If you buy one anticipating running a red light in the U.S. and slipping past the red light run cameras, forget about it. Total waste of money.

 

The spray on stuff from the local "Spy Store" is worthless also. These may work on low lit areas with the cheapest cameras used for surveillance, but then again a cheap camera cannot pull in a number.

[jefinny 0]

For viewing car licence plate, there is the special box camera, you should choose this.

[ajm 0]

Hi,

 

anyone could tell me if this camera will work on LPR at night with decent street lights.

distance is about 50 feet, slight angle. speed of car under 15 mph

 

Item Code: ISC-P540X

Description: HQ1 540 TVL Hi-Res Infrared Varifocal

1/3" Sony SuperHAD HQ1 Color CCD

540 Line

Weatherproof

Tamperproof

Varifocal 4 - 9 mm

48 LED

Spot Monitor Output

 

spec sheet is here:

cctvdealers . com/customer/intsys/PDF/ISC-P540X.pdf

 

excerpt:

 

GENERAL PHYSICAL

Sensor Type 1/3-inch Sony Super HADTM HQ1 CCD

Effective Pixels 768 (H) x 494 (V)

Scanning System 2:1 Interlace

Scan Frequency 15.734kHz (H), 59.94Hz (V)

Horizontal Resolution 540 TV Line

Iris Control Adjustable

CCD Shutter Speed 1/60 - 1/100,000 second

Auto Iris DC

Minimum Illumination 0 lux:LED On

S/N Ratio >48dB

Automatic Gain Control On/Off switchable

Electronic Shutter Control On/Off switchable

Backlight Compensation On/Off switchable

Flickerless Mode On/Off switchable

White Balance Auto

Sync Type Internal

External Lens Adjustment Yes

Signal Processing Digital Signal Processing (DSP)

Gamma Correction 0.45

Video Output 1.0Vp-p(Sync, Negative), 75 ohms

[dnieweg 0]

Nope, it probably won't work and here is why:

 

Regardless of the resolution of the camera, the effective resolution of your captured image will be the result of your recorder and the compression applied to the image.

 

Let's start with a standard 320 X 240 captured image. In order to get even minimal license plate recognition you are going to need around 60 pixels wide covering the plate. With a captured resolution of 320 wide this means that 320/60 = 5.3 which means that the license plate will need to fill at least 1/5th of the width of the picture.

 

A license plate is about a foot wide in the US so that means your maximum field-of-view needs to be about 5-6 feet wide. At 50 feet your 1/3" camera has the ability to zoom (set to 9mm) to a width of 35 feet. So you are looking at too wide an area.

 

So next lets assume your recorder can record at 4CIF so we will use the maximum horizontal resolution which is 704 pixels.

 

704/60 = 11.73 and again since a plate is about a foot wide this means your maximum horizontal width is about 11-12 feet. Again, I say your camera can only zoom to 35 feet wide at that distance.

 

But you have other problems such as lighting. Your camera is not really a low light camera .. it says zero lux because they have included those nifty little IR led's that they claim will illuminate up to 100 feet. Well, first thing is that they won't. In the dark you will see movement and objects but not detail.

 

You did say that the area was well lit, but I will guess that it is overhead lighting and only a small percentage will be reflected towards your camera. Next is the real deal killer, and that is that your target (the car) will probably have it's headlights on at night. Those two little glaring blips of light will flood the scene with light, the electronic shutter will speed up and your plate will be very very dark.

 

Electronic shutters are a cheap mans auto-iris which provides a more limited dynamic light range than you would with an auto-iris.

 

Next problem, your target is moving, and assuming we solve the headlight problem we will now be dealing with low light levels.. The electronic shutter will slow down so the CCD can capture enough light for an image. The camera is interlaced so it will capture one frame when the car is at one spot and capture the next frame a few feet further down the road. This will make the picture look like it's made up of two pictures that don't exactly match up .. becuase that is exactly what it is. I should point out that there is software you can use to clean this up after the fact .. but hey ..

 

So what do you do?

 

Can you add more zoom to reduce the field of view? Yes, but the more you zoom the less light you can capture. To improve the image to where you need you would need this:

 

• 10 foot max field of view at that distance.

• Higher light levels

• Light directed directly onto the plate so that it will reflect back to your camera.

• A slower moving car

• and finally a recorder that could capture the required resolution

 

We also did not touch on compression. Compression will destroy the quality of your image so you would need to back it way way off and of course this will increase your file size. So then you might decrease your frame rate to compensate, but you can't do that because you have a moving target and you need as many images as you can get in the hopes that you will capture one at the correct lighting and angle.

 

Is all lost? lol Perhaps, but the real deal is that people all want to capture license plates and it really is more of an engineering challenge than most people anticipate.

 

One very real option you have today are the newer megapixel cameras. Consider that the camera you specified at 4CIF recording would be the equivalent of 400k pixels .. less than half a megapixel.

 

Now contrast that to one of the newer 5 megapixel IP cameras. That is about 10 times the resolution which would be fully capable of the resolution you need at that distance.

 

But, you need a recorder that will record the entire 5 megapixels per image. Check out 3xlogic .. of course .. lol

 

 

 

You still need to deal with the fact that your car is moving and that you have light issues and more specifically headlight issues. With more light your car can move faster, with less light your car will need to be going slower.

 

You can always do a little trial and error and see what your real issues are.

 

Dave

[ajm 0]

Dave,

 

awesome answer, thanks that helped a lot to get the picture.

 

Nope, it probably won't work and here is why:

 

Regardless of the resolution of the camera, the effective resolution of your captured image will be the result of your recorder and the compression applied to the image.

[CameraGimp 0]

Here is how I would make a camera to capture number plates.

 

Start with a fairly low cost monochrome camera that allows you to set fixed shutter speeds. Set the speed so you get sharp images of fast moving plates. Leave it at this speed. Don't use electronic iris, this ranges from 1/50 - 1/100,000s and you will get blurred images on the slow shutter speeds.

 

Fit an IR pass filter (Note - this passes IR and is not the IR CUT filter as used on colour and day/night cameras). With this in place the camera will only see IR light. The camera won't be bothered by headlights as it won't see them. This will make the camera useless for everything but seeing number plates.

 

Shine IR at your on coming cars. The IR will reflect off the plate and you will see it. You won't see the car, its headlights or the road just the plate.

[dnieweg 0]

CameraGimp,

 

That a great idea. So your IR pass filter is actually a cut filter for visible light? Have you tried this? Can you provide a link for this type of filter? I can think of several situations in which this could prove useful.

 

Thanks!

 

Dave

[CameraGimp 0]

Yes, an IR pass stops everything below a wavelength but allows those above. I'm fairly sure this is how some anpr cameras operate. You remove all the useless parts of the image so the computer has less trouble finding the plate and you control the light level not the sun.

 

Filters are available via the net or maybe try the glass fitted over old ir lamps, the ones that use filament bulbs. They stop visible light and pass ir.w

[dnieweg 0]

It seems that ANPR (Plate Recognition) is much more in demand in the UK than it is here in the US and I wonder why that is. I've talked to many station owners, parking lot's and even airports and while they appear to see the value, in the end they don't pursue it.

 

Anyone have thoughts or comments on this? Anyone in the US have a client using ANPR successfully to help manage their business?

 

Thanks