What if we could do this...for better night number plate

[Choice777]

Check these two videos out. Maybe we could remove the IR filters from the dash cam sensors and put a single IR strobe on the car pointing left/right depending on country driving side. SO the dash cam sees number plates perfectly at night and since its IR nobody will complain...maybe put the IR strobe/flash/led whatever we come up with in the fog light socket since nobody uses fog lights 99.9% of the time.

This one

And in this one if you look starting at 3:15 and listen carefully

 

[niko]

Interesting idea.
I guess the problem with dashcms not reading numberplates at night is headlights reflection from numberplate background. Even if you add a strobe IR light, the car main headlights will still remain turned ON during night time driving which will cause numberplates over-brightening and reflection of headlights back into camera lens.

 

[Dashmellow]

At 3:15 in the video, if you "listen carefully", the narrator describes two separate light sources. He says, "Infra-Red lamps dry the ink in a split second......A strobe light allows the operator to do spot checks". So there is no infra-red strobe being used here, only a typical white light xenon strobe light in addition to a heat lamp.

Infra-red strobe lamps do exist but good ones with enough power are expensive. (like THIS one) In theory I think an idea like this could work though. You would want an IR light source of 940nm so that it would be 100% invisible to oncoming cars and pedestrians. The problem would be that you would need a specialized camera with the proper sensor and specific IR-pass filters on the lens with additional filters to block other parts of the spectrum. In other words you would want to block almost all visible light wavelengths and have a camera that can ONLY see the IR wavelengths. Removing the IR-cut filter from a dash cam will increase the sensitivity to infra-red to some degree but the sensor would still see other visible wavelengths and as @niko points out, a car's headlights will blow out and overwhelm the camera with too much light for a typical dash cam to handle.

 

[Choice777]

I din't intend to say the IR would be used to dry road paint. the IR strobe would be used to not be visible to others , only to our dash cam. I figured the blocking visible light part..i'm wondering if th dash cam can be tweaked in the firmware to make it magically sync to the strobe pulses...that's the part that's missing.

 

[Dashmellow]

I din't intend to say the IR would be used to dry road paint. the IR strobe would be used to not be visible to others , only to our dash cam. I figured the blocking visible light part..i'm wondering if th dash cam can be tweaked in the firmware to make it magically sync to the strobe pulses...that's the part that's missing.

No, a dash cam could not be "tweaked" to "magically" sync with the strobe pulses, nor would you want to. Even if you could, it is not "the part that's missing".

 

[Choice777]

Oh gowd... Not really magically... The strove had to match the cameras fpsi think. And it would be a good idea to drop the cameras fps to 24 and match the strove at 24. 30fps seems to much at night for any dash cam CPU. Also tweaking the firmware to get higher bitrateand force the CMOS and cpu to film black and white that would reduce the processing needs and allow more space for bitrate or less heat issues.

 

[Dashmellow]

Well, you are the one who used the word "magically", I just quoted you.

The basic concept of using an IR strobe to capture a license plate number is intriguing but like I said, it would require a highly specialized camera, sensor, cut and pass filters and a very fast lens.

Your notion that, "The strove (sic) had to match the cameras fpsi think." is incorrect. Matching a strobe's flash rate to the video frame captures per second is not at all how this works and is not how the videos you posted were accomplished. The presenter even explains that in the video. The capture of the individual water droplets is entirely a function of the speed of the flashes, not the video frame rate. Later in the video, the presenter demonstrates how you can make the droplets appear to be going backwards by increasing the number of flashes per second while leaving the camera at whatever rate it was shooting at previously (probably 30 fps).

The bitrate, frame rate, "reducing the processing needs" or shooting in black and white is not how this works. As I tried to explain in my earlier post, what is required is a sensor that is sensitive t0 the 940nm region of the spectrum and appropriate filtration to cut out most of the rest of the spectrum so that the camera will not be sensitive to your vehicle's headlights. (or any headlights) The fact is that you could do this without a strobe, instead using a full time IR illuminator but you still need a dedicated IR sensitive camera to do the job. And, no, removing the IR cut filter from a standard dash cam wouldn't work well enough for this purpose to make it viable.

 

[Choice777]

Well the most important video is the second one. It's actually similar to one that i saw years ago. Basically it allows the human eye to see stuff slowed down..those printed thingys are very fast, but the strobe light let's say it's set at 24 fps liek the human eye likes it. So some cheapo xiaomi yi action cam + a used dslr lens with f smaller than 2.0 and strobe light at ..umm..not quite sure..24 fps ? 30 fps as the dash cam, or 60 fps ? or maybe 100 Sps(strobes per second) ?
I know the police anpr in london flash really fast for a 0.5 second interval when they go past you so they catch your rear plate...happened to me at night..definetely strobe like flash 3-5 times at least really no more than half a second.

 

[Dashmellow]

The second video you keep referring to uses an incandescent Infra-Red heat lamp to dry ink and a white light xenon strobe so the operator can see random scratch ticket numbers with his eyes which has nothing to do with capturing numbers with a video camera. What the human eye can see and what a camera can capture on video have little to do with one another. You started out this thread talking about IR strobe lights but neither of the videos has anything to do with IR strobes.

Police ANPR cameras are highly specialized devices costing many thousands of dollars that don't work the same way a dash cam or typical video camera operates. Firstly, they use Optical Character Recognition (OCR) to capture plate numbers and they usually use high speed global shutters rather than the rolling shutter you'll find in a dash camera. The have powerful DSPs that employ special algorithms and dedicated plate recognition engines. They are much bigger than dash cameras and use much bigger sensors. Also, you will always see these cameras mounted in the fender or trunk of police cars because their IR emitters and cameras cannot work from inside the car's cabin. Technically, what the police use are not even really cameras, per se, they are scanners. The list and reasons goes on but the fact is that no matter what you do you will never be able turn a little dash cam with its one third inch sensor, ill-equipped for the task DSP and little M12 lens into a high performance license plate reader like the police use.

You've proposed this intriguing idea here in the DIY forum. If you really think you have it worked out, why not see what you can come up with and report back with your results?

 

[kuoh]

The flashes per second is not the key here, it's the ability of the system to react in time to a flash so as to not over expose the detail you're after. As Dashmellow said, the shutters and sensors in our class of cameras are not designed to function well in that realm regardless of what lens you throw in front of it. Trying to use a typical sensor to capture both visible and IR spectrum while retaining image quality is not easy, let alone having it be able to compensate for very short periods of high over exposure. The color balance will also be way off, so objects will have weird, sometimes unexpected tints.

As for the strobe slowing or freezing objects in motion, that's a combination of persistence of vision and the strobe frequency IN RELATION to the object, not to your eyes. If an object is moving in a repeating pattern that's 24 Hz, then a 24 Hz strobe will appear to freeze its motion. It's not because your eye likes to see that frequency. If the recurring frequency happens to be 47 Hz, then you will need a 47 Hz strobe or a matching harmonic. When they show an object moving backwards or forwards, they're actually purposely mismatching the strobe frequency to something like 46.9 or 47.1, to make it appear slight before or after the position of the previous flash, thus giving the illusion of movement. None of this however, is applicable to capturing the license plate on a car, unless the car was spinning on a turn table at a predictable frequency. The reason you see the police strobe is the same as a normal camera flash. It really just needs one flash per image plus a fast shutter speed, but they could be taking multiple images for backup in case of an obstructed view or some other anomaly that could cause an image defect.

KuoH

So some cheapo xiaomi yi action cam + a used dslr lens with f smaller than 2.0 and strobe light at ..umm..not quite sure..24 fps ? 30 fps as the dash cam, or 60 fps ? or maybe 100 Sps(strobes per second) ?

 

[Choice777]

I keep referring to the second video cause that's the one where the human eyes are using the strove light.
Like I said once, I'll day it again. I never said we should use IR cause it's on the video.. I'm talking strictly about the strobe in the second video, I don't care about the IR lamp in the second video cause, LIKE I said before, we ain't go no paint to dry on the road.
The only reason I mention strobe IR is cause then nobody else sees the strobe with normal eyes, only cameras, and more importantly our camera.
Get it ? I don't care if they had ultra violet and fairy dust... I've added the wired IR next to the word strobe just on my own not cause it's in the video.... Argg... How many times must I explain...
As for the police anpr I was pointing out that they too don't use full motion video at night but a series of flashes line a strobe coming directly from the anpr camera on the car roof. So obviously they haven't got some awesome camera that sees number at night in motion.. They use strobe light at night for 0.x seconds on a visible wavelength, so ours couldn't very well work full time, as in not just 0.x seconds but non stop, in IR and nobody would complain.
Waveguide to stop visible light and removing IR filter from cmos in any... I think I'll just take apart one of my many useless dash cams and see if it's got an IR filter.
Edit. Maybe IR lights replacing the fog light, constantly on at night... That should match the strobe of light itself at 300k pulses a sec. Lol