Parley
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Here is another one of those instances. The lighting has to be just right or the angle just right.
Sometimes I Can Read A Plate At Night With Car Lights On
- Thread starter Parley
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bigredfish
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Parley
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Hikvision varifocal with a 1/1.8" sensor and 8-32mm lens. We had a car burglary around the corner in the above picture last night and I was watching to see if I could get a picture of the culprit. While I was watching a car slowed way up in front of my house and as he went by that was another instance as to where I could have got a picture of the plate. However he did not stop and kept on going so I did not bother.
The culprit did come by my house but the lights came on and I think he got wind of my cameras and he kept on going. He cut across my front lawn and looked like he was going straight for my car parked in the driveway. He turned away at the last second and kept on going.
Edit: in the above picture if the palm tree blocks out the passenger head light of the car driving by that is another instance that I can sometimes get a plate number. By the way that car is parked in front of a house that is 2 houses down the street.
The culprit did come by my house but the lights came on and I think he got wind of my cameras and he kept on going. He cut across my front lawn and looked like he was going straight for my car parked in the driveway. He turned away at the last second and kept on going.
Edit: in the above picture if the palm tree blocks out the passenger head light of the car driving by that is another instance that I can sometimes get a plate number. By the way that car is parked in front of a house that is 2 houses down the street.
J Sigmo
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A lot of times the headlights of a car will blind the camera, so as you point out, having the palm tree block the near headlight allows the camera to see the plate. I've often wondered if a very bright IR illuminator could solve some license plate reading issues by lighting the license plate so well that it would appear as bright as typical car headlights (at least somewhat off-axis). This would be a case where you'd want the IR illuminator to be mounted very close to the camera so that the retroreflective license plate paint would send the light from the IR illuminator back more-or-less directly to the camera's lens.
If a camera is zoomed out, or just uses a long focal length fixed lens so as to see distant objects better (as is often the set-up for license plate reading), you'd also want the IR illuminator to be focused out and properly aimed to illuminate the same area that the camera is viewing. That would help concentrate the illumination where you want it.
Years ago, a friend and I built a couple of light-blasters using photographic flash guns mounted into boxes with large Fresnel lenses on the other end such that it focused the light from the flash gun into a fairly tight beam. You could fire them from, for example, a 12th floor dorm room down onto a "target" at ground level, and a fairly small area (perhaps 15 feet by 15 feet in size) would be intensely illuminated, creating an amusing effect.
The same sort of thing could be constructed to focus the output of a normal IR illuminator down to a beam that matches the angle of view of the security camera, and it might well be able to match the brightness of car headlights (again, not exactly on-axis) and allow the camera to read license plates despite the "desensitization" created by the headlights. It would give more of a daylight look to the scene and license plates. Since license plates do use the retroreflective glass beads (or something similar) the brightness required of the light source should not be too extreme, especially if the light source is located physically very near to the camera lens.
Of course, you would then have the typical problems associated with the light source being close to the camera, such as rain, dust, bugs, etc., appearing very bright in the images. But such a setup might be able to "reach out" and show license plates at night even when confronted with headlights. You're basically fighting fire with fire, so to speak, and getting bright enough illumination to overcome the brightness of the headlights.
If a camera is zoomed out, or just uses a long focal length fixed lens so as to see distant objects better (as is often the set-up for license plate reading), you'd also want the IR illuminator to be focused out and properly aimed to illuminate the same area that the camera is viewing. That would help concentrate the illumination where you want it.
Years ago, a friend and I built a couple of light-blasters using photographic flash guns mounted into boxes with large Fresnel lenses on the other end such that it focused the light from the flash gun into a fairly tight beam. You could fire them from, for example, a 12th floor dorm room down onto a "target" at ground level, and a fairly small area (perhaps 15 feet by 15 feet in size) would be intensely illuminated, creating an amusing effect.
The same sort of thing could be constructed to focus the output of a normal IR illuminator down to a beam that matches the angle of view of the security camera, and it might well be able to match the brightness of car headlights (again, not exactly on-axis) and allow the camera to read license plates despite the "desensitization" created by the headlights. It would give more of a daylight look to the scene and license plates. Since license plates do use the retroreflective glass beads (or something similar) the brightness required of the light source should not be too extreme, especially if the light source is located physically very near to the camera lens.
Of course, you would then have the typical problems associated with the light source being close to the camera, such as rain, dust, bugs, etc., appearing very bright in the images. But such a setup might be able to "reach out" and show license plates at night even when confronted with headlights. You're basically fighting fire with fire, so to speak, and getting bright enough illumination to overcome the brightness of the headlights.