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Thread: Telecam Update

  1. #1
    ***Euro-Nova Supporter*** Spacenut's Avatar
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    Telecam Update

    Hi everyone - its been a bit quiet in the telecam forum recently, so I thought I would bring you all up to speed on the latest developments with the Green Machine.

    As you know, I have a 5" monochrome CRT mounted in the dash, and a 1/3" CCD under the upper slat of my louvre panel, offset to the driver's side. To summarise the changes from the original reversing camera specification...

    (1) The 120° FOV lens was changed for a 42° FOV. This results in better resolution of vehicles approaching from behind, and minimises distortion, while at the same time overlapping and complementing the FOV of my external rear view mirrors. The new lens has a longer focal length, which required spacing the PCB off the chassis in order to clear the front cover glass.

    (2) The 6 IR LEDs for reversing illumination were useless for normal driving (and I couldn't differentiate their contribution from my tail lights when reversing), so the whole board was removed.

    (3) Neutral density filter film has been applied between the cover glass and the camera to try and reduce glare, particularly when driving at night. This latter modification has reduced the visible light levels, but has had no effect on the received IR component, which the camera is particularly sensitive to. As a result, daytime driving looks like I am travelling through snowfields (the chlorophyl in grass and plants strongly reflects the IR part of the spectrum), and night driving is still just headlight glare.

    My night driving woes are about to change (I hope). More details to follow...

    Lauren
    only Pythagoras can save me now!

  2. #2
    ***Euro-Nova Supporter*** Spacenut's Avatar
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    Re: Telecam Update

    OK, as most of you know, night driving with an IR sensitive CCD camera is a bit of a problem, as the high IR content of car headlights causes the camera to white-out, making it impossible to safely judge either the distance or closing speeds of cars coming up behind me.

    I think this old video adequately demonstrates the point...

    http://youtu.be/e0i-9QcJmTE

    At first I thought it was just down the position of the camera - after all, most production car headlamps are on the same level as my rear window. But the more miles I did in the dark, the more obvious it became that this was not the main reason for the white-out. Stopping down the sensitivity of the CCD seemed to be the answer, but the neutral density film I used only works in the visible light spectrum - so all I was doing was suppressing the visible spectrum from the camera and not doing anything to reduce the IR component - hence the slightly surreal daytime viewing!

    The answer comes in the form of an IR cut-off filter. I have just purchased one from an outfit called UQG Optics in Cambridge. They do a number of different options, but after measuring up the S-mount lens holder on my spare board camera, I have opted for the 10mm square version, as I can bond this into the back of the lens holder so that it completely covers the CCD element.

    These coated glass filters (together with so-called "hot" mirrors) are used in DSLR cameras to remove the IR component that would otherwise ruin (or at least make very weird) the visual appearance of digital photographs. You've only got to look at the events gallery to appreciate how effective these filters are - every DSLR, digital compact and camera phone use the same technology, so you'd soon know about it if the leaves on the trees were looking pink (which they do in the infra-red).

    Anyway, enough talk - here is the proof. I used an DVB remote control unit to provide the intense IR light source, and shone it directly into the lens of my mini-DVR camera, which does not have an IR filter either. The results of this are spectacular, not only blinding the camera but causing siginificant colour distortion as well. But with the filter over the lens, the IR is almost completely suppressed (the white-out around the edge of the image is the spillover from the non-filtered part of the lens)

    http://youtu.be/AluLH51QHQU

    So, all I have to do now is get the camera out of the car, and carefully open up the lens holder and bond the new filter in place. The 10 x 10mm format appears to be designed with this purpose in mind.

    More progress as it happens...

    Lauren
    only Pythagoras can save me now!

  3. #3

    Re: Telecam Update

    Bravo. BRavo!! I will have to do the same once I upgrade to the rearview camera or maybe just replace all the mirrors with cameras since the blind spot is pretty bad on my ride.

    But Thanks again for sharing your findings this is very useful.
    Rob

  4. #4
    ***Euro-Nova Supporter*** Spacenut's Avatar
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    Re: Telecam Update

    Thanks Rob - I'm hoping to find some time this weekend to dismantle the camera and fix the filter glass in place. Then I shall be all set for the winter!

    (apart from the new dash, canopy hinges, new canopy, new gearbox, new engine, respray, LED rear light conversion... )

    Hopefully have some further updates in the next week. Watch this space!

    Lauren
    only Pythagoras can save me now!

  5. #5

    Re: Telecam Update

    the new CCD camera i have fitted works better than the last in night driving, but it is about 1/2" further back from the rear panel for some reason. i did have a perspex panel over the now hole, would I be able to fit something in between or does it have to be on the camera lens.
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  6. #6
    ***Euro-Nova Supporter*** Spacenut's Avatar
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    Re: Telecam Update

    Okay, here's the (provisional) results... (its a bit like Final Score isn't it?)

    I removed my camera module from the car, then took out the CCD board and removed the lens holder. All S-mount lenses are the same, two small screws locate in the threaded lugs. Here's what the board looks like...



    Once the lens holder is removed, the CCD is revealed in all its rainbow coloured glory...



    Sorry about the image quality by the way, I really should have used a rigid camera mount, but you get the idea. The little black square between the PCB and the lens holder is my home-made IR filter holder - an iris cut from cardboard and painted black. The edges of the aperture look a bit rough (and they are), but the size of the aperture is such that the camera FOV is not affected (I checked very carefully, I don't want to have to take this apart again!). I cut two thin strips of cardboard and glued them to the top and bottom of the iris plate. These locate the IR filter glass in the middle of the iris.

    I then took a deep breath and applied superglue (isocyanate) to the edges of the iris and dropped the IR filter glass in. The adhesive retains the filter glass along two of its edges. I cleaned the filter glass and the inside of the lens with a cotton bud before carefully placing the iris and filter into the CCD shroud.

    Here's what it looked like once in place...



    The reddish tint is the IR coating on the filter. I cut the iris so it is a press-fit into the shroud, and once back on the PCB, the iris is retained by the CCD cover glass so it isn't going anywhere.

    Phew! Now I just had to fit the PCB back into the front half of the camera (I cleaned the outer lens and the inside of the outer cover glass before tightening the screws), then it was back outside to reconnect the signal and power connectors before refitting the backshell.

    Take off the coil + connector, switch on the ignition and power up the monitor... yes, here comes the image... but wait a second – its out of focus! The image is blurred, both for distant images and close-up. What could be wrong?

    Well, whatever the reason, I needed to take the camera apart again, this time leaving the power and signal connectors in place but exposing the CCD lens. There is a small grub screw on the side of the shroud, which when released allows the lens to screw in and out, thereby adjusting the focus. I slowly unscrewed the lens until the brick courses on next doors wall came into sharp focus, then I carefully tightened the grub screw.

    All this time I was wondering how the focus could have changed so dramatically, and then the penny dropped – the camera was operating so far into the infra-red, when I introduced the filter I removed all the IR, leaving just the visible light component, which was out-of-focus because of its shorter wavelength!

    So clearly, a dramatic change in the spectrum sensitivity of the camera had already taken place – all I needed to do now was replace the PCB into the front half of the camera again and tighten the allen screws holding the backshell in place. I kept checking the image at each stage, in case I was inadvertently putting pressure on the lens or board (clearance with the 42° FOV lens is tight), and then I remounted the camera on its bracket...



    And here is what the resulting image looks like...



    A not very inspiring view of my neighbours bungalow, and I need to play with the brightness control a bit (possibly), but even on an overcast day like today the grass still reflects strongly in the infra-red... but you can't see it!

    Also not in evidence is any cropping of the image by the iris, so I did make the hole big enough after all!

    I pushed the car back into the garage, closed the door and with the lights off powered up the monitor and touched the brakes – no blinding glare reflected off the garage door into the camera this time – just a bright patch to let you know the light is on. Same with the reversing lights – no sudden change in contrast. I've got a good feeling about this guys...

    Lauren
    only Pythagoras can save me now!

  7. #7
    ***Euro-Nova Supporter*** Spacenut's Avatar
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    Re: Telecam Update

    First trip out with the new camera, to Goodwood for the last breakfast club event of the year. I set off early, so it was still half-light and waited for cars to appear in my rear view...

    Unfortunately, being 7am on a Sunday morning there wasn't a lot of traffic, and I only saw one set of car lights, some way distant. From that brief experience I may have to put up with secondary reflections in the image, due to the addition of the IR filter, but they didn't seem any worse than the kind of reflections you get in a standard prismatic dipping mirror, and being able to suppress the flare from the lights (so I can distinguish a pair of them, which you rely on at night to judge speed and distance) is my main priority.

    The filter has removed all of the surreality from the image, and grass fields look like grass now, not snow. All in all, I think its going well, but it may be a few days yet before I use the car in the dark again. I will let you know what I find.

    Until then, safe night driving, telecammers!

    Lauren
    only Pythagoras can save me now!

  8. #8

    Re: Telecam Update

    inspirational
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  9. #9

    Re: Telecam Update

    Hi Lauren

    I can't see the images at the moment - I am at work - but I look forward to having a look when I get home.

    I have all this to come..... so this is a tremendously useful thread

    My setup is very similar to yours - apart from the use of a colour monitor. By sheer coincidence I was starting the process of fitting the thing over this weekend. The main discovery (apart from the fact that it works fine - albeit with a 120° FOV right now) was that I will need to redesign the back window to get it to fit under the louvre successfully. A previous owner has widened the apperture and (incidentally) left the inside open to the engine because the hacked about window tunnel doesn't butt up to the perspex screwed to the outside - no wonder it is so noisy and fumey inside!

    Anyway, I digress - I am writing here to ask a question. At first I was concerned that the louvre basically blocks most of the lower half of the view from the camera - until I realised that in fact the rear end of the car lines up perfectly with the outer edge of the louvre - so nothing is lost unless I really wanted a view of the engine when the louvre is not in place. My question is, are you happy with the the horizontal positon of your camera ? So far I have gone with putting it dead central to the louvres/back window and as high as it can go before the top louvre gets in the way, however even with a 120° FOV I don't (apparently) quite see the edges of the car so I was wondering if that's why you have yours closer to the driver's side ?

    The camera is not properly fitted yet - I have to sort out that window first, so I may find that it is fine where it is when I can actually reverse the car up and do some testing.

    Of course I won't be driving at night at ALL until I have replaced the candles/lights at the front (Still Capri to keep the MK1 look, but the later non-sealed beam type running with Halogens if and when I can find some).

    Thanks as always

    Steve

  10. #10
    ***Euro-Nova Supporter*** Spacenut's Avatar
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    Re: Telecam Update

    Hi Steve - are you keeping the 120° FOV lens in the camera? If so, you will not find it very useful as a rear view when driving, there is too little detail of what is happening in the distance. For reversing it is preferable to retain the wide FOV and stick the camera in the rear transom panel instead of under the louvre.

    From what you have said about the camera location, I infer that your intended use is for rear vision while driving forwards, and for this purpose I would recommend reducing the FOV to 50° or less. I still notice that cars travelling on my bumper are distorted like a funhouse mirror, even with a 42° FOV lens in place. Your view with a 120° lens will be constrained by the bodywork if the camera is not mounted above the level of the louvre anyway.

    As to the placement of the camera with respect to the vehicle centreline, I reasoned at the time that as approaching traffic comes from the offside, that if I placed the camera on that side of the vehicle, I would see slightly more of the approaching traffic than I would if it was mounted centrally. This has generally proved to be the case, but is a less pronounced benefit with the reduced FOV lens. If I was doing it again, I might do it differently, as the offset camera position makes lining up for reversing more difficult! If you are using a wider FOV lens, the camera offset may possibly even increase the size of your offside blind spot, which is still fairly large, in spite of the external mirrors.

    So yes, by all means centrally locate the camera under the louvre, but I would seriously consider reducing the FOV by fitting a longer focal length lens. If you've had the bits for more than a year it will be out of guarantee anyway, and the electronics are pretty robust - I have not taken any ESD precautions when handling the PCB, for example.

    If you have IR LEDs for night vision you may want to do something about removing them and reducing the IR sensitivity at the same time, although I appreciate that I have not offered demonstrable proof that the IR cutoff filter works at night yet!

    Lauren
    only Pythagoras can save me now!

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