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Thread: Question About Filming High Powered Laser Safely

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    Default Question About Filming High Powered Laser Safely

    Hi all,

    I have run into an interesting problem which I am sure has some optical solution, but I am having difficulty for some reason divining what that might be. I would love to hear any creative feedback anyone might have!

    For the purposes of this situation, assume that there are virtually no budgetary or logistical constraints. Everything is on the table.

    I have an potential application in which a laser would need to be filmed from a distance of about 50 feet. The catch here is that beam attenuation maps and other methods of masking are not really possible because both the laser and camera may be moving. To achieve the desired angle of view from the camera, the camera path is likely to fully cross the laser field between +/- 15 degrees from center on both the X and Y axis.

    There is no real coordination between the camera and the show so we can't really program around camera movements.

    So, the question is how to protect the camera sensor from a fatal laser hit while obtaining a reasonable video from the show.

    My initial idea was to add a neutral density filter to the front of the camera and boost the sensitivity to try and get back some of the brightness. The issue there is that the colors seem to desaturate and just don't look right.

    Does anyone else have a creative solution to this problem beyond praying and beefing up an insurance policy?

  2. #2
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    Notch filters, Acousto-optic filtering, and a few Polarization/Waveplate techniques , come to mind.

    Is the camera moving or fixed along its roll (optical) axis?

    Can the camera's motion be precisely programmed and synced with the effect?



    Steve
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  3. #3

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    Thanks for the reply Steve! I hope you are well.

    So, I have to assume that the camera is moving in any direction in the scan field. I expect it will be on a boom which would allow it to articulate in numerous ways. I expect that it will be operated by a live operator so no pre-programmed movements. Basically the problem comes down to how to create the best protection for the sensor while getting a good picture in a limited control situation.

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    mixedgas's Avatar
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    Dan, Some of the ideas I have I can't place in the public domain, I'll call you tomorrow.

    Steve
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    I have no idea if this will work, but I'll toss it out there: What if you could guarantee horizontal polarization for the laser beams and put a vertical polarizing filter on the sensor? Scatter from fog/dust should alter the polarization and be visible to the camera, but direct beam hits should be attenuated. Of course, if PBS combining is used in the projector, that might not work to block all of the light. Could lead to some other interesting effects, though. Might be interesting to test this on a bench first.

    Another idea is to do something like an auto-darkening welding helmet; the problem here is getting the sensor in the same path as the image formed by the main objective. If you had a mostly-transparent photo-sensitive material on a glass substrate, you could put it in front of the CCD/CMOS chip and wire it to a darkening panel. Not sure what the response times required or achievable would be, but it's another thought.

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    i would just use cinefoil to hard mask the laser aperture then map out the masked/non-masked projection areas and tell the camera man he's buying a new camera if he exits the safe areas.
    suppose you're thinkin' about a plate o' shrimp. Suddenly someone'll say, like, plate, or shrimp, or plate o' shrimp out of the blue, no explanation. No point in lookin' for one, either. It's all part of a cosmic unconciousness.

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    Wouldn't a polarization filter / opposite polarized laser then block the beam effects as well ? Or would scatter from fog alter it enough to be visible ? And if altered enough to be visible, would it not pass through the polarization filter negating the intended protection ?

    Notch filtering or any other filtering would have the same issue I'd think. Anything that would block the light from entering the lens aperture would also block the intended effect one is trying to capture.

    Honestly I think the only viable way would be to attenation map the desired area, and to extend on that perhaps choreograph a moving attenuation map to follow the camera's intended path. But that'd need to be planned ahead.

    Could divergence be used ? It's not a guarantee but the lower the power density, the less likely for cameras to sustain damage. For audience scanning shows at or below mpe, is camera damage often still a common issue ? The issue is further complicated by different options for lenses and focussing and difference sensor sizes, so there's never a guarantee but could at least greatly reduce the chances of damage.


    For on the fly, perhaps Laaris or the kinect interface for Beyond or other software solution could be used to avoid the camera aperture on the fly ? I remember seeing on youtube someone had a rig that would target mosquitos out of the air, perhaps a similar technology could be used to avoid a camera aperture.

    I think if such a technology were available that could avoid cameras and projectors automatically and on the fly, it would be quite welcomed amongst laserists, I'd imagine many would happily pay for such a product.

  8. #8

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    Good ideas guys, the polarization thing would have to be tried. I imagine that the basic idea here is right that if it is polarized it would be blocked. The scatter effect is a testable hypothesis - it may just cut down on the amplitude without changing the color like the ND does. Interesting idea.

    Divergence would also help, but in this case that would meaningfully alter the artistic effect. That may be an option of last resort.

    In general, projection or attenuation mapping is just not possible. With the camera path crossing the middle of the frame blocking out most or all paths would really compromise the show. I would map the crap out of this if I could, but sadly not so. =)

    Keep em' coming if anyone else has ideas!

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    Oh! Just use a film camera.

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    How about increasing your exposure time and lowering the laser power? If its for a live performance, can the entire show be filmed in advance? Do you have ways to film blocks of the intended show and can you do the more dramatic and or risky moves pre show in a controlled environment. Then do post show editing with pre rehearsed / taped and live footage. (assuming no aforementioned budgetary constraints). Some of the video editing software out there is pretty amazing nowadays.
    Will there be three phase!!!!

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