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How could the camera on missiles and smart bombs keep its focus?

Discussion in 'General Electronics' started by Sea Squid, Mar 18, 2005.

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  1. Sea Squid

    Sea Squid Guest

    I was watching the documenrary Century of Warfare. It has some
    segments of how the video shot when missiles and bombs are closing
    on the target. I guess the missile will fly to the target at 334m/s so the
    camera must have a extremely fast zooming and autofocus trick. Can
    anybody here provide me with some information?
     
  2. Jomby

    Jomby Guest

    None needed.
    Think about it, the camara angle starts narrow stays narrow for 95% of the
    flight then goes wide?
    does it have to go wide?
     
  3. Sea Squid

    Sea Squid Guest

    But the camera has to stay in focus before it can shoot. In the movie, all
    the pictures
    in the few frames before blackout are all in focus.
     
  4. Schoenfeld

    Schoenfeld Guest

    Lens focal point is trivially calculable from height.
     
  5. Sea Squid

    Sea Squid Guest

    but a physical zoon lens can not zoom in fraction of a miniseconds. My D-SLR
    can
    only zoom 0.2 second after I press the handle.
     
  6. Nosterill

    Nosterill Guest

    Zoom would not be usual on a missile. Some of the cleverer ones have
    switched fields of view.
    Focus adjustment is also generally not implemented, since by the time
    focus degrades, some tens of metres off target, all parties are past
    caring.
    Bombs would not generally have full video imaging systems, rather using
    some kind of centroid seeker to stay on target or marker. This is also
    true of all but the most sophisticated missiles. Are you sure the video
    you saw was shot from the bomb/missile and not from the dispensing
    aircraft?
     
  7. Phil Allison

    Phil Allison Guest

    "Nosterill"

    ** I expect the video cameras alluded to by the OP were mounted on the
    weapons for promotional purposes - ie to provide spectacular images to woo
    prospective customers into parting with their pesos.





    ................... Phil
     
  8. Andy Resnick

    Andy Resnick Guest

    AFAIK, The systems I worked on several years ago were non-imaging: a
    quadrant dectector or reticle was used to determine pointing. Also,
    tracking wasn't performed in the final hundred yards or so- the missile
    flew blind at that point. Most missiles use radar and thermal sensing
    rather than visual optics.

    It's not clear what you saw on tv- usually there is a video feed on the
    aircraft that paints the target, or that drops the ordinance- is that
    what you were seeing?

    Another consideration is that low f-number optics, which can help in
    terms of sensor systems that only have to look straight ahead, have very
    large depths of field (as another poster pointed out).

    Finally, note that air-to-air and air-to-ground systems are very
    different, and have different closing speeds and target tracking
    technologies.
     
  9. Louis Boyd

    Louis Boyd Guest

    The cameras in video "smart bombs" are fixed focus set at infinity and
    not zoomed. Any apparent "zooming" is just that the camera gets closer
    to the target. No moving parts are needed for the camera. They're not
    much different from a common webcam. Exposure is is controlled by the
    clocking of the CCD so no iris is required. It doesn't matter if the
    camera is in poor focus for the last meter before hitting the target.
     
  10. tadchem

    tadchem Guest

    ....produced in 1993 - dates the technology.
    Well-described here:
    http://science.howstuffworks.com/smart-bomb2.htm

    I haven't seen it, but it it may refer to the GBU-15, a video-guided
    remotely controlled weapon, or something very similar.
    I've seen those on the news. Cool!
    Nothing fancy needed...
    A small aperture (lens opening) combined with highly sensitive
    photodetector array allows a great depth of field (range over which the
    image is acceptably in focus). Modern mobile phones with built-in
    cameras similarly can give clear images from 1 meter to infinity. The
    drawback is that it is difficult to adjust for different light levels
    (not really much of a problem with digital imaging, but important with
    photographic film) and you can't really "zoom" or adjust for extreme
    close-ups (like imaging small subjects).

    Current "smart weapons" technology uses GPS for high precision over
    extreme ranges.

    Tom Davidson
    Richmond, VA
     
  11. Uncle Al

    Uncle Al Guest

    The optics are focused at infinity. Infinity starts around 5 feet.
    Nobody cares about the last 5 msec.
     
  12. oðin

    oðin Guest

    I was watching the documenrary Century of Warfare. It has some
    Can you give any reason to think that any zoom or autofocus is required?
     
  13. Poxy

    Poxy Guest

    I suspect it is what the poster is referring to. I remeber when the smart
    bomb thing was all the craze, in the TV broadcasts the shot would often zoom
    as the missile flew down the air-duct or into the open window etc, but the
    one's I saw were clearly done afterwards by zooming the video image,
    resulting in tell-tale pixelation.
     
  14. In sci.physics, Sea Squid
    <>
    wrote
    If the camera operator can tell a building from a rock, that's
    probably all the focus one needs. Hitting the right building
    is a plus -- as shown in Bosnia. :)

    Besides, the missile is moving quite fast. Does the operator
    have time to pull out a lightmeter and estimate f-stop? :)
     
  15. Too bad the camera does not live past the explosion so that we can see
    the human beings being blown apart on the History channel. Severed
    limbs quivering in the Mosque. Camel parts splattered on the walls.
    Heads not quite dead yet with eye lids still fluttering or looking
    into the camera from the bomb that killed them.

    Imagine the photos we could have had if the bombers dropped TV cameras
    during the Dresden fire raid or the Tokyo raids or at Hiroshima. Here
    they are vaporizing! Now that would have been entertainment enough for
    the war lovers for 10,000 years.

    Frankly, I think it was a mistake to release these "smart bomb"
    pictures to be viewed by the avaerage two digit IQ monkeys who watch
    TV.

    Jim Klein
     
  16. tadchem

    tadchem Guest

    message
    Of course, that assumes you *know* which building is the 'right' one.


    Tom Davidson
    Richmond, VA
     
  17. In sci.physics, tadchem
    <>
    wrote
    There is that, though that falls outside of the camera's capabilities
    (though it might transmit various artifacts/details of
    the building that might give the operator a hint).

    The camera operator, presumably, would have to know that. :)

    [.sigsnip]
     
  18. oðin

    oðin Guest

    Technology still has not freed us from the curse of "pilot error."

    Some errors are intended.
     
  19. tadchem

    tadchem Guest

    Technology still has not freed us from the curse of "pilot error."


    Tom Davidson
    Richmond, VA
     
  20. Guest


    The whole reason that they keep their focus is because
    likes all things air force,

    they don't keep their focus,
    they're not cameras,
    they're not really that smart,
    They're standard issue milspec (1 ea),
    Pentagon video feeds.

    It's don't work any differently
    than the local weatherman in
    Cape Kennedy does.
     
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