Lame CEV windows

William C. Keel wrote:
Tom Cuddihy wrote:


A secondary problem is that CCD pixels need much more incident light
than say film or the human retina to get a 'detection.'


Huh? There would be a reason that astronomers made the switch from
photographic emulsion (much less visual use) as soon as there were
remotely enough chips to go around, and a bit part of that is that
you can get CCDs with quantum efficiency peaking at 90% within the
visual wavelenth range, whereas few films ever cracked 2%.


Bill Keel

I'm not talking about large telescope-worthy one-off multi-million
dollar focal planes, but your average, off the chip assembly line CCD
focal plane. Moore's law never applies to essentially zero-demand
specialty items anyway.

Even the the specially-built CCDs have long integration & exposure
times generally equivalent to an ISO '100' film. Hubble's exposure
times vary from ~.15- 3000 sec.
Quickbird, IKONOS, and other high-res earth-observing sats have to use
tricks like pushbroom 'time delay integration' and fast slewing. And
that's for a one-dimensional array.

My information might be out of date with regard to the very state of
the art--all those systems were built in the 80s anf late 90s--but I'm
pretty sure it's in line with industry norms.

A secondary problem is that CCD pixels need much more incident light
than say film or the human retina to get a 'detection.'

Other way around, isn't it?

See
http://micro.magnet.fsu.edu/primer/d...fficiency.html

Tom Cuddihy wrote:
Alex Terrell wrote:
3MP will be no problem. That's what high end PCs do now, at a perfectly
acceptable frame rate.

20MP, = 20Meg * 25 fps * 16 bit colour would need 8 Gbps uncompressed.
But that's probably 800 Mbps. Tricky now, but shouldn't be too
difficult in 2011 with USB 4.0.

The biggest problem is that optical sensors like CCDs DONT follow
Moore's law. The demand is small enough that the economics that go into
Moore's law for CPUs don't apply to CCDs, because although there is
continuous market demand for faster CPUs, there's not currently much
demand for super-high resolution CCDs, and the demand for
higher-resolution CCDs is also constrained by, as you intimate above,
the speed of the bus and size of the memory available.

I was thinking of digital camera technology. 8 Mega Pixel is pretty
standard, and the growth will follow Moore's law until people realise
there's no benefit from better resolution.

A secondary problem is that CCD pixels need much more incident light
than say film or the human retina to get a 'detection.' Beyond that the
resolution is also limited by the size of your optics, by the Rayleigh
criteria. That also drives the necessary size of the optics up, and
their response time, or 'speed'.

A digital camera though can work well in infrared or with image
enhancing. The computer can also overlay other data (e.g from radar) on
to the image.

But maybe in the future someone will invent a killer app for
super-highres CCDs.

I must be missing something here. What's in digital cameras?

Allen Thomson wrote:
A secondary problem is that CCD pixels need much more incident light
than say film or the human retina to get a 'detection.'

Other way around, isn't it?

See
http://micro.magnet.fsu.edu/primer/d...fficiency.html

Kodak has a film (may or may not have reached the market) with grains
having 4-photon sensitivity. I don't know what the number of
electron-hole pairs is for that, so I'm not sure if that represents 25%
QEF or 90% QEF.

The film has amazing sensitivity for scientific uses, but the reason
Kodak spent the money developing: plastic lenses on throw-away cameras
have terrible light losses.

/dps

snidely wrote:

Kodak has a film (may or may not have reached the market) with grains
having 4-photon sensitivity. I don't know what the number of
electron-hole pairs is for that, so I'm not sure if that represents 25%
QEF or 90% QEF.

The film has amazing sensitivity for scientific uses, but the reason
Kodak spent the money developing: plastic lenses on throw-away cameras
have terrible light losses.

Not just that, but high F-stops to enable focus free operation probably
don't help the light levels either.

Alex Terrell wrote:
Tom Cuddihy wrote:
Alex Terrell wrote:
3MP will be no problem. That's what high end PCs do now, at a perfectly
acceptable frame rate.

20MP, = 20Meg * 25 fps * 16 bit colour would need 8 Gbps uncompressed.
But that's probably 800 Mbps. Tricky now, but shouldn't be too
difficult in 2011 with USB 4.0.

The biggest problem is that optical sensors like CCDs DONT follow
Moore's law. The demand is small enough that the economics that go into
Moore's law for CPUs don't apply to CCDs, because although there is
continuous market demand for faster CPUs, there's not currently much
demand for super-high resolution CCDs, and the demand for
higher-resolution CCDs is also constrained by, as you intimate above,
the speed of the bus and size of the memory available.

I was thinking of digital camera technology. 8 Mega Pixel is pretty
standard, and the growth will follow Moore's law until people realise
there's no benefit from better resolution.

A secondary problem is that CCD pixels need much more incident light
than say film or the human retina to get a 'detection.' Beyond that the
resolution is also limited by the size of your optics, by the Rayleigh
criteria. That also drives the necessary size of the optics up, and
their response time, or 'speed'.

A digital camera though can work well in infrared or with image
enhancing. The computer can also overlay other data (e.g from radar) on
to the image.

But maybe in the future someone will invent a killer app for
super-highres CCDs.

I must be missing something here. What's in digital cameras?

low-res, relatively low-tech CCDs.

Tom

On 26 Oct 2005 22:03:56 -0700, in a place far, far away, "Tom Cuddihy"
made the phosphor on my monitor glow in such a
way as to indicate that:

Big windows are heavy, which matters more to a smaller vehicle, and they
are difficult to protect against the higher temperatures of a capsule

As they say on submarines...windows are for tourists...

Unfortunately, that's the biggest market.

Besides, in the age of color XGA flatpanel diplays that weigh 1 pound,
who needs windows?

People who want to actually see it at full resolution?