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

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?

 

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?

 

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.

 

Lens focal point is trivially calculable from height.

 

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.

 

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?

 

"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

 

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.

 

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.

 

....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

 

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

 

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?

 

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.

 

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?

 

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

 

message

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


Tom Davidson
Richmond, VA

 

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]

 

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

Some errors are intended.

 

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


Tom Davidson
Richmond, VA

 

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.