On Mar 7, 8:17 am, Gene Fuller wrote:
Cecil Moore wrote:

Coherency, non-coherency, and interference is covered well
in "Optics" by Hecht and other textbooks. Optical physicists
have been tracking the EM energy flow for centuries. This
information may be new to you but it is old hat in physics.

Cecil,

You may or may not already know this, but a lot of detailed optical
analysis these days is done with full 3-D electromagnetic simulation,
starting from Maxwell equations and boundary conditions. Interference,
coherence, energy flow, and all of the other stuff you like to discuss
can be *output* from that analysis, but those items are not part of the
input. The "centuries old" optics simply does not get the job done. The
"centuries old" stuff may work in the (impossible) cases where
everything is completely lossless and ideal, but it doesn't give the
right answers in the real world.

73,
Gene
W4SZ

You can sure say that again...in fact, Maxwell doesn't really do it
either when you get to quantum mechanical effects. But that's a story
for another day.

Certainly, those who design and build FTIR spectrometers know
perfectly well that interference does not depend on a narrow-band
coherent source. Blackbody radiation works just fine, thank you. But
it doesn't take much beyond belief in linear systems to understand
that. I recall explaining to a company VP how it worked in terms of a
linear system, and it was very gratifying to see the virtual light
bulb lighting up in his head...he really got it.

Cheers,
Tom

K7ITM wrote:
Certainly, those who design and build FTIR spectrometers know
perfectly well that interference does not depend on a narrow-band
coherent source.

How narrow-band? How coherent? In the irradiance (power
density) equation, Ptot = P1 + P2 + 2*sqrt(P1*P2)cos(A),
if the angle 'A' is varying rapidly, what value do you
use for cos(A)?

A constant average sustained level of destructive
interference cannot be maintained between two waves
unless they are coherent. If they are not coherent
the interference will average out to zero.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
K7ITM wrote:
Certainly, those who design and build FTIR spectrometers know
perfectly well that interference does not depend on a narrow-band
coherent source.

How narrow-band? How coherent? In the irradiance (power
density) equation, Ptot = P1 + P2 + 2*sqrt(P1*P2)cos(A),
if the angle 'A' is varying rapidly, what value do you
use for cos(A)?

A constant average sustained level of destructive
interference cannot be maintained between two waves
unless they are coherent. If they are not coherent
the interference will average out to zero.

Gee, I wonder if the experts may have moved beyond the elementary optics
textbook descriptions?

Are you suggesting that FTIR cannot work unless one has your nice 1-D
configurations with perfectly monochromatic waves? Does everything need
to be collinear and coherent?

73,
Gene
W4SZ

Gene Fuller wrote:
Are you suggesting that FTIR cannot work unless one has your nice 1-D
configurations with perfectly monochromatic waves?

Have you stopped beating your wife? Please cease and
desist with your diversions in the form of innuendo.

It is not my fault that a transmission line is essentially
one-dimensional but I am willing to take technical advantage
of that fact of physics. It is not my fault that CW transmitters
emit essentially monochromatic waves but I am willing to take
technical advantage of that fact of physics.
--
73, Cecil http://www.w5dxp.com

On Mar 7, 2:34 pm, Gene Fuller wrote:
Cecil Moore wrote:
K7ITM wrote:
Certainly, those who design and build FTIR spectrometers know
perfectly well that interference does not depend on a narrow-band
coherent source.

How narrow-band? How coherent? In the irradiance (power
density) equation, Ptot = P1 + P2 + 2*sqrt(P1*P2)cos(A),
if the angle 'A' is varying rapidly, what value do you
use for cos(A)?

A constant average sustained level of destructive
interference cannot be maintained between two waves
unless they are coherent. If they are not coherent
the interference will average out to zero.

Gee, I wonder if the experts may have moved beyond the elementary optics
textbook descriptions?

Are you suggesting that FTIR cannot work unless one has your nice 1-D
configurations with perfectly monochromatic waves? Does everything need
to be collinear and coherent?

73,
Gene
W4SZ

So--I have a classic Michelson interferometer, and I see the classic
ring pattern on the screen at the "output" port. I also have a
sensitive microchannel plate detector system that I propose to put in
place of the screen, so that I can reduce the light amplitude to where
it makes sense to be observing it with the very sensitive detector.
In fact, I propose to reduce the light level to the point that the
short wavelength light I'm using is only putting a few photons per
second into the interferometer. I'll count a significant fraction of
those photons and identify where they landed on the microchannel
plate. Do you suppose, Gene, that I'll still see the same
interference pattern that I saw with the much higher intensity light?
Is there any limit to how low a light level I can use and still see
the pattern?

If I do still see the pattern, there must be yet another "dimension" I
need to add to my understanding of the situation -- not rooted in
classical Maxwell e&m.

And of course a dimension that is removed if you think only of average
quantities is time; one who thinks only in terms of averages removes
the possibility of the deeper understanding that resolution as a
function of time allows.

Cheers,
Tom

K7ITM wrote:
On Mar 7, 2:34 pm, Gene Fuller wrote:
Cecil Moore wrote:
K7ITM wrote:
Certainly, those who design and build FTIR spectrometers know
perfectly well that interference does not depend on a narrow-band
coherent source.
How narrow-band? How coherent? In the irradiance (power
density) equation, Ptot = P1 + P2 + 2*sqrt(P1*P2)cos(A),
if the angle 'A' is varying rapidly, what value do you
use for cos(A)?
A constant average sustained level of destructive
interference cannot be maintained between two waves
unless they are coherent. If they are not coherent
the interference will average out to zero.
Gee, I wonder if the experts may have moved beyond the elementary optics
textbook descriptions?

Are you suggesting that FTIR cannot work unless one has your nice 1-D
configurations with perfectly monochromatic waves? Does everything need
to be collinear and coherent?

73,
Gene
W4SZ

So--I have a classic Michelson interferometer, and I see the classic
ring pattern on the screen at the "output" port. I also have a
sensitive microchannel plate detector system that I propose to put in
place of the screen, so that I can reduce the light amplitude to where
it makes sense to be observing it with the very sensitive detector.
In fact, I propose to reduce the light level to the point that the
short wavelength light I'm using is only putting a few photons per
second into the interferometer. I'll count a significant fraction of
those photons and identify where they landed on the microchannel
plate. Do you suppose, Gene, that I'll still see the same
interference pattern that I saw with the much higher intensity light?
Is there any limit to how low a light level I can use and still see
the pattern?

If I do still see the pattern, there must be yet another "dimension" I
need to add to my understanding of the situation -- not rooted in
classical Maxwell e&m.

And of course a dimension that is removed if you think only of average
quantities is time; one who thinks only in terms of averages removes
the possibility of the deeper understanding that resolution as a
function of time allows.

Cheers,
Tom

Tom,

One step at a time. Cecil has not yet accepted the real world in the
classical state. The quantum state will need to wait.

8-)

73,
Gene
W4SZ

Gene Fuller wrote:
Cecil has not yet accepted the real world in the
classical state.

I know there is no such thing as a lossless transmission
line, Gene. That doesn't prohibit me from using lossless
transmission lines in an example, does it? Every textbook
on transmission lines that I have ever seen does the same
thing.
--
73, Cecil http://www.w5dxp.com

On Sat, 8 Mar 2008 10:12:04 -0800 (PST), K7ITM wrote:

Is there any limit to how low a light level I can use and still see
the pattern?

Hi Tom,

The Quantum Efficiency of the eye is between 40% and 50%. The time to
convert one photon in a visual receptor is roughly 14 femtoseconds.

I have seen no component that can match the bandwidth, dynamic range,
AND sensitivity of the eye.

73's
Richard Clark, KB7QHC

On Sat, 08 Mar 2008 14:21:59 -0800, Richard Clark wrote:

On Sat, 8 Mar 2008 10:12:04 -0800 (PST), K7ITM wrote:

Is there any limit to how low a light level I can use and still see the
pattern?

Hi Tom,

The Quantum Efficiency of the eye is between 40% and 50%. The time to
convert one photon in a visual receptor is roughly 14 femtoseconds.

I have seen no component that can match the bandwidth, dynamic range,
AND sensitivity of the eye.

Side note:

Back in the day, when I did a lot of color processing and printing, I
would spend log hours in the darkroom in total darkness.

The only light shedding items were the old Gra-Lab timers, and
luminescent tape on the dangerous corners. After several hours, the light
output from them was just about nil.

My eyes were totally adapted, full visual purple. At this time, the
luminescent tape and dials seemed to scintillate discretely, not the
typical overall glow.

I always wondered if I was possibly seeing individual photon effects.

- 73 de Mike N3LI -

On Sat, 08 Mar 2008 19:12:01 -0600, Mike Coslo
wrote:

I always wondered if I was possibly seeing individual photon effects.

At the risk of over-extending the discussion: one in two events, with
the photoreceptors doing what we would call pulse-stretching as the
mind is wholly incapable of discerning a visual event of less than,
roughly, 10mS duration.

73's
Richard Clark, KB7QHC