My Homebrew License Plate Capture System

[dvarapala 0]

For the last few months I've been playing around with a homebrew license plate capture camera setup. The "real" license plate cameras that I have seen start at ~$2000 and go up from there; I set out to see if I could come up with a combination of off-the-shelf components that would work well but cost much less.

 

The camera I selected is an Arecont Vision AV1310DN megapixel IP camera, fitted with a Computar 25mm megapixel lens and an IR-pass filter that blocks visible light below 830nm, available from http://www.maxmax.com/aXNiteFilters.htm. The Camera is set permanantly in night mode, with the built-in IR-cut filter switched out. Mounted next to the camera is a Raymax RM10030C infrared illuminator, making it possible to capture plates at night. I set the camera to a fixed shutter speed of 1/500th of a second; this eliminates motion blur and allows the sharpest possible plate captures.

 

The camera is mounted on a block wall fence next to my house, which is at the end of a dead-end street with a cul-de-sac. The angle between the camera and the street is approximately 25 degrees.

 

During the day (with the IR illuminator off) capture isn't a problem:

 

 

The exception is on very bright, sunny days, if the angle of the sun is just right, the LP is overexposed and washed out. I suspect an auto-iris lens would solve this issue, but unfortunately the AV1310DN only supports manual iris lenses.

 

Capturing vehicles in the near lane is good enough, in most cases, to manually make out the plate number. This minivan is roughly 40 - 50 feet away from the camera:

 

 

Capturing vehicles in the far lane is also possible under the right conditions. This car is ~90' from the camera:

 

 

The angles vary because the vehicles are turning around in the cul-de-sac; if my camera was mounted more towards the middle of the block, it would have a better chance of capturing the exiting vehicles. Fortunately for me they have to drive into the cul-de-sac before they can drive out, so in most cases I catch them on the way in anyway. The cul-de-sac also helps to slow the vehicles down to a reasonable speed for blur-free plate capture.

 

If I had it all to do over again, I would pick a camera with an auto-iris lens and adjustable gain (to help cut down on some of the noise in the picture during night-time captures). I'd also go with a camera that has remote focusing capability, or at the very least I would use a flip-top outdoor housing that allowed easier access to the focusing ring on the lens. The outdoor housing I bought is basically an aluminum tube, so once the camera is mounted inside there is very little space to reach my fingers inside to set and lock the focus.

 

All told, this setup cost roughly half of what a "real" license plate cam would cost. And the learning experience was priceless.

[mike_va 0]

nice post, thanks

[jhonovich 0]

Cool project. I enjoyed reading it. If you are able to adjust the horizontal angle, I think you could get even better performance.

 

There are quite a few LPC cameras available for less than a $1000. Do a google search for 'license plate capture camera'. I believe most are analog but you could connect to an encoder, etc.

 

Also, there are many IP cameras with built in IR illuminators. You will likely get similar results with them simply by forcing into night mode and setting a very short exposure.

[dvarapala 0]

Cool project. I enjoyed reading it. If you are able to adjust the horizontal angle, I think you could get even better performance.

 

That's going to be a challenge given the layout of my property.

 

There are quite a few LPC cameras available for less than a $1000. Do a google search for 'license plate capture camera'.

 

Any that are not a no-name brand, and that can honestly work at ~90' distances? I did the search and browsed through the results, but didn't see anything that appeared trustworthy.

[projeto56 0]

Also, there are many IP cameras with built in IR illuminators. You will likely get similar results with them simply by forcing into night mode and setting a very short exposure.

 

If this is truth i really would like you to recommend me some tested models