Back to the IR light source concept...

This message crossed over into RPEM as an "in case anybody is interested
in my progress" update. Primarily aimed at the sci.electronics groups,
since the start of the whole thing was there, and appears to have
generated some interest there.

Some of you may recall my post a few weeks ago asking about IR LEDs,
filters, and other yakkety-yak about cheap ways to fab a light source
that puts out either pure IR, or "close enough to it", with little or no
visible component, for use in what boils down to a homebrew "Night
Vision" system designed around a video camera that has a
well-demonstrated sensitivity to IR in the same region of the spectrum
that TV remotes use.

After some false starts, I've managed what I think would count as a
reasonable "first cut" at the problem.

As those who are a bit more "techno-geeky" than the average Joe are
aware, the base material used in CDs *MUST* be IR transparent if the CD
is going to be readable by the (IR) laser in the player/reader.
Regardless of what color (blue, silver, gold, whatever) the reflective
material appears to be, or what color the base plastic shows up as in
visible light, the plastic that it gets coated onto has to be clear (or
close enough) to IR - A fact which permits such weirdness as the "black"
PlayStation CDs, odd-colored CD-R/CD-RW media, and so on. Which got me
thinking...

If one were to remove the reflective layer from, for instance, one of
the black PlayStation CDs, or the black CD-Rs that can be had, it would
stand to reason that one would then have a chunk of plastic that's (at
least reasonably) opaque to visible light, but transparent to IR.

After spending some time looking for, and a grand total of 8 dollars
acquiring, a few of these "black" CDs, I went to work on taking my idea
from the realm of theory to reality. And I'm pleased to say "it works!"

Preliminary testing, using a 3-cell Mag-Lite and a chunk of black CD
material with the reflective coating removed (with steel wool, as a
first attempt - I'm thinking some kind of solvent might be better as I
refine the concept) and cut down to a suitable size to replace the
normal clear "lens" of the Mag-Lite is showing great promise - Using
this as a light source, and my camcorder set to an appropriate zoom, I
can literally read the date off a quarter from the other side of a room
that my eyes perceive as pitch black other than a faint hint of red
where the flashlight is pointing - Not "darkroom quality" dark, by any
stretch, but close enough that my naked eye says "Dude!!! It's freakin'
DARK in here!"

Now to refine the idea...

Although the "filter" I built is functional, it seems to be doing a bit
too good of a job in scattering the light - Almost certainly due to the
fact that my method of removing the reflective material from the base
plastic of the CD left what's probably best described as a crude "ground
glass" finish on it - Instead of being the usual pristine "It's so
clear, it's like nothing is there at all" plastic, my scrubbing to
remove the coating has created a more-or-less matte finish that doesn't
transmit anywhere near as well as I had hoped. Kind of like a lens that
has somehow escaped from its proper holder, then spent the last few
months bouncing around in the bottom of your ditty-bag with all kinds of
things that a lens isn't supposed to associate with if it's going to
remain unscratched and clear until it has become "frosted" by all the
scratches it has acquired.

So at this point, I'm trying to figure out the best way to polish out
the scratches left by the steel wool, and get back to a truly
transparent (rather than translucent) finish on my homemade "filter".

Is there a reasonably easy way to do so? I don't know... I went after
the thing with 4-0 steel wool - as fine as I know how to locate - under
a layer of 40-weight motor oil, and although I did my best to avoid
excessive scrubbing (and therefore, scratching) I ended up with a
semi-matte, and therefore semi-translucent, finish on the filter. My
next move is probably to a 2400-grit wet/dry sandpaper that bills itself
as "Mirror-Brite", and to the touch, feels just about as abrasive as a
sheet of regular printer paper.

From there, my guess is that I'm going to need to move to something like
rubbing compound, rottenstone, or even ultra-fine jeweler's rouge.

Does this seem reasonable to those who have done optical grinding work?

Or am I way off base here?

--
Don Bruder - - New Email policy in effect as of Feb. 21, 2004.
Short form: I'm trashing EVERY E-mail that doesn't contain a password in the
subject unless it comes from a "whitelisted" (pre-approved by me) address.
See http://www.sonic.net/~dakidd/main/contact.html for full details.

"Don Bruder" wrote in message
...
So at this point, I'm trying to figure out the best way to polish out
the scratches left by the steel wool, and get back to a truly
transparent (rather than translucent) finish on my homemade "filter".

Is there a reasonably easy way to do so? I don't know... I went after
the thing with 4-0 steel wool - as fine as I know how to locate - under
a layer of 40-weight motor oil, and although I did my best to avoid
excessive scrubbing (and therefore, scratching) I ended up with a
semi-matte, and therefore semi-translucent, finish on the filter. My
next move is probably to a 2400-grit wet/dry sandpaper that bills itself
as "Mirror-Brite", and to the touch, feels just about as abrasive as a
sheet of regular printer paper.

From there, my guess is that I'm going to need to move to something like
rubbing compound, rottenstone, or even ultra-fine jeweler's rouge.

Does this seem reasonable to those who have done optical grinding work?


Okay, I may or may not know an awful lot about either electonics or optics,
but I'm a darn good model builder. One of my pet projects is to build a
plastic model of every car I've owned and in the process I've learned a lot
about handling plastic. To make a long story shorter, I've learned how to
take a lucite windshield from a plastic car model that's been "ruined" by
having glue run onto it and to repair it into something that's at least as
good as new.

Go to www.micromark.com and look for a polishing kit. It has abrasives -- I
can't call them sandpaper anymore -- in grits ranging from a low of 2400 up
to 12,000. That's right, a grit equivalent of Twelve Thousand! You can
make your plastic as "transparent" as you want with sufficient elbow grease
and one of these kits.

Norm

"Don Bruder" wrote in message
...
So at this point, I'm trying to figure out the best way to polish out
the scratches left by the steel wool, and get back to a truly
transparent (rather than translucent) finish on my homemade "filter".

Is there a reasonably easy way to do so? I don't know... I went after
the thing with 4-0 steel wool - as fine as I know how to locate - under
a layer of 40-weight motor oil, and although I did my best to avoid
excessive scrubbing (and therefore, scratching) I ended up with a
semi-matte, and therefore semi-translucent, finish on the filter. My
next move is probably to a 2400-grit wet/dry sandpaper that bills itself
as "Mirror-Brite", and to the touch, feels just about as abrasive as a
sheet of regular printer paper.

From there, my guess is that I'm going to need to move to something like
rubbing compound, rottenstone, or even ultra-fine jeweler's rouge.

Does this seem reasonable to those who have done optical grinding work?


Okay, I may or may not know an awful lot about either electonics or optics,
but I'm a darn good model builder. One of my pet projects is to build a
plastic model of every car I've owned and in the process I've learned a lot
about handling plastic. To make a long story shorter, I've learned how to
take a lucite windshield from a plastic car model that's been "ruined" by
having glue run onto it and to repair it into something that's at least as
good as new.

Go to www.micromark.com and look for a polishing kit. It has abrasives -- I
can't call them sandpaper anymore -- in grits ranging from a low of 2400 up
to 12,000. That's right, a grit equivalent of Twelve Thousand! You can
make your plastic as "transparent" as you want with sufficient elbow grease
and one of these kits.

Norm

"Don Bruder" wrote in message
...
So at this point, I'm trying to figure out the best way to polish out
the scratches left by the steel wool, and get back to a truly
transparent (rather than translucent) finish on my homemade "filter".

Is there a reasonably easy way to do so? I don't know... I went after
the thing with 4-0 steel wool - as fine as I know how to locate - under
a layer of 40-weight motor oil, and although I did my best to avoid
excessive scrubbing (and therefore, scratching) I ended up with a
semi-matte, and therefore semi-translucent, finish on the filter. My
next move is probably to a 2400-grit wet/dry sandpaper that bills itself
as "Mirror-Brite", and to the touch, feels just about as abrasive as a
sheet of regular printer paper.

From there, my guess is that I'm going to need to move to something like
rubbing compound, rottenstone, or even ultra-fine jeweler's rouge.

Does this seem reasonable to those who have done optical grinding work?


Okay, I may or may not know an awful lot about either electonics or optics,
but I'm a darn good model builder. One of my pet projects is to build a
plastic model of every car I've owned and in the process I've learned a lot
about handling plastic. To make a long story shorter, I've learned how to
take a lucite windshield from a plastic car model that's been "ruined" by
having glue run onto it and to repair it into something that's at least as
good as new.

Go to www.micromark.com and look for a polishing kit. It has abrasives -- I
can't call them sandpaper anymore -- in grits ranging from a low of 2400 up
to 12,000. That's right, a grit equivalent of Twelve Thousand! You can
make your plastic as "transparent" as you want with sufficient elbow grease
and one of these kits.

Norm

In article ,
"Norm Dresner" wrote:

"Don Bruder" wrote in message
...
So at this point, I'm trying to figure out the best way to polish out
the scratches left by the steel wool, and get back to a truly
transparent (rather than translucent) finish on my homemade "filter".

Is there a reasonably easy way to do so? I don't know... I went after
the thing with 4-0 steel wool - as fine as I know how to locate - under
a layer of 40-weight motor oil, and although I did my best to avoid
excessive scrubbing (and therefore, scratching) I ended up with a
semi-matte, and therefore semi-translucent, finish on the filter. My
next move is probably to a 2400-grit wet/dry sandpaper that bills itself
as "Mirror-Brite", and to the touch, feels just about as abrasive as a
sheet of regular printer paper.

From there, my guess is that I'm going to need to move to something like
rubbing compound, rottenstone, or even ultra-fine jeweler's rouge.

Does this seem reasonable to those who have done optical grinding work?


Okay, I may or may not know an awful lot about either electonics or optics,
but I'm a darn good model builder. One of my pet projects is to build a
plastic model of every car I've owned and in the process I've learned a lot
about handling plastic. To make a long story shorter, I've learned how to
take a lucite windshield from a plastic car model that's been "ruined" by
having glue run onto it and to repair it into something that's at least as
good as new.

Go to www.micromark.com and look for a polishing kit. It has abrasives -- I
can't call them sandpaper anymore -- in grits ranging from a low of 2400 up
to 12,000. That's right, a grit equivalent of Twelve Thousand!

Yikes!!!! That sounds like it's probably at least as fine (if not finer)
than what an ancient (1906 original publication date - my copy is a 1963
reprint edition) book I have on optics calls "100 minute emery" - As in,
"shovel raw, screened emery powder into a 12 foot tall, 3 foot wide pipe
full of water, stir the everlovin' bejeezus out of it for half an hour,
then let it stand undisturbed for 100 minutes. At the end of 100
minutes, drain off the liquid (catching it - it's the part you want) to
about a foot above the bottom, dumping what remains in the bottom back
onto the "raw material" pile, evaporate the liquid you drained in
whatever way works, and sell the powder that remains after the water is
gone as 100 minute emery". As of the publication date of the book, that
was apparently the finest abrasive that could be had, and was right at
the limit of being practical to "sort out".

I'll hit this "Micromark" place and see what they've got that would suit
my shoestring budget. Thanks for the suggestion!

--
Don Bruder - - New Email policy in effect as of Feb. 21, 2004.
Short form: I'm trashing EVERY E-mail that doesn't contain a password in the
subject unless it comes from a "whitelisted" (pre-approved by me) address.
See http://www.sonic.net/~dakidd/main/contact.html for full details.

In article ,
"Norm Dresner" wrote:

"Don Bruder" wrote in message
...
So at this point, I'm trying to figure out the best way to polish out
the scratches left by the steel wool, and get back to a truly
transparent (rather than translucent) finish on my homemade "filter".

Is there a reasonably easy way to do so? I don't know... I went after
the thing with 4-0 steel wool - as fine as I know how to locate - under
a layer of 40-weight motor oil, and although I did my best to avoid
excessive scrubbing (and therefore, scratching) I ended up with a
semi-matte, and therefore semi-translucent, finish on the filter. My
next move is probably to a 2400-grit wet/dry sandpaper that bills itself
as "Mirror-Brite", and to the touch, feels just about as abrasive as a
sheet of regular printer paper.

From there, my guess is that I'm going to need to move to something like
rubbing compound, rottenstone, or even ultra-fine jeweler's rouge.

Does this seem reasonable to those who have done optical grinding work?


Okay, I may or may not know an awful lot about either electonics or optics,
but I'm a darn good model builder. One of my pet projects is to build a
plastic model of every car I've owned and in the process I've learned a lot
about handling plastic. To make a long story shorter, I've learned how to
take a lucite windshield from a plastic car model that's been "ruined" by
having glue run onto it and to repair it into something that's at least as
good as new.

Go to www.micromark.com and look for a polishing kit. It has abrasives -- I
can't call them sandpaper anymore -- in grits ranging from a low of 2400 up
to 12,000. That's right, a grit equivalent of Twelve Thousand!

Yikes!!!! That sounds like it's probably at least as fine (if not finer)
than what an ancient (1906 original publication date - my copy is a 1963
reprint edition) book I have on optics calls "100 minute emery" - As in,
"shovel raw, screened emery powder into a 12 foot tall, 3 foot wide pipe
full of water, stir the everlovin' bejeezus out of it for half an hour,
then let it stand undisturbed for 100 minutes. At the end of 100
minutes, drain off the liquid (catching it - it's the part you want) to
about a foot above the bottom, dumping what remains in the bottom back
onto the "raw material" pile, evaporate the liquid you drained in
whatever way works, and sell the powder that remains after the water is
gone as 100 minute emery". As of the publication date of the book, that
was apparently the finest abrasive that could be had, and was right at
the limit of being practical to "sort out".

I'll hit this "Micromark" place and see what they've got that would suit
my shoestring budget. Thanks for the suggestion!

--
Don Bruder - - New Email policy in effect as of Feb. 21, 2004.
Short form: I'm trashing EVERY E-mail that doesn't contain a password in the
subject unless it comes from a "whitelisted" (pre-approved by me) address.
See http://www.sonic.net/~dakidd/main/contact.html for full details.

In article ,
"Norm Dresner" wrote:

"Don Bruder" wrote in message
...
So at this point, I'm trying to figure out the best way to polish out
the scratches left by the steel wool, and get back to a truly
transparent (rather than translucent) finish on my homemade "filter".

Is there a reasonably easy way to do so? I don't know... I went after
the thing with 4-0 steel wool - as fine as I know how to locate - under
a layer of 40-weight motor oil, and although I did my best to avoid
excessive scrubbing (and therefore, scratching) I ended up with a
semi-matte, and therefore semi-translucent, finish on the filter. My
next move is probably to a 2400-grit wet/dry sandpaper that bills itself
as "Mirror-Brite", and to the touch, feels just about as abrasive as a
sheet of regular printer paper.

From there, my guess is that I'm going to need to move to something like
rubbing compound, rottenstone, or even ultra-fine jeweler's rouge.

Does this seem reasonable to those who have done optical grinding work?


Okay, I may or may not know an awful lot about either electonics or optics,
but I'm a darn good model builder. One of my pet projects is to build a
plastic model of every car I've owned and in the process I've learned a lot
about handling plastic. To make a long story shorter, I've learned how to
take a lucite windshield from a plastic car model that's been "ruined" by
having glue run onto it and to repair it into something that's at least as
good as new.

Go to www.micromark.com and look for a polishing kit. It has abrasives -- I
can't call them sandpaper anymore -- in grits ranging from a low of 2400 up
to 12,000. That's right, a grit equivalent of Twelve Thousand!

Yikes!!!! That sounds like it's probably at least as fine (if not finer)
than what an ancient (1906 original publication date - my copy is a 1963
reprint edition) book I have on optics calls "100 minute emery" - As in,
"shovel raw, screened emery powder into a 12 foot tall, 3 foot wide pipe
full of water, stir the everlovin' bejeezus out of it for half an hour,
then let it stand undisturbed for 100 minutes. At the end of 100
minutes, drain off the liquid (catching it - it's the part you want) to
about a foot above the bottom, dumping what remains in the bottom back
onto the "raw material" pile, evaporate the liquid you drained in
whatever way works, and sell the powder that remains after the water is
gone as 100 minute emery". As of the publication date of the book, that
was apparently the finest abrasive that could be had, and was right at
the limit of being practical to "sort out".

I'll hit this "Micromark" place and see what they've got that would suit
my shoestring budget. Thanks for the suggestion!

--
Don Bruder - - New Email policy in effect as of Feb. 21, 2004.
Short form: I'm trashing EVERY E-mail that doesn't contain a password in the
subject unless it comes from a "whitelisted" (pre-approved by me) address.
See http://www.sonic.net/~dakidd/main/contact.html for full details.

"Don Bruder" wrote in message
...
In article ,
"Norm Dresner" wrote:

"Don Bruder" wrote in message
...
So at this point, I'm trying to figure out the best way to polish out
the scratches left by the steel wool, and get back to a truly
transparent (rather than translucent) finish on my homemade "filter".

Is there a reasonably easy way to do so? I don't know... I went after
the thing with 4-0 steel wool - as fine as I know how to locate -
under
a layer of 40-weight motor oil, and although I did my best to avoid
excessive scrubbing (and therefore, scratching) I ended up with a
semi-matte, and therefore semi-translucent, finish on the filter. My
next move is probably to a 2400-grit wet/dry sandpaper that bills
itself
as "Mirror-Brite", and to the touch, feels just about as abrasive as a
sheet of regular printer paper.

From there, my guess is that I'm going to need to move to something
like
rubbing compound, rottenstone, or even ultra-fine jeweler's rouge.

Does this seem reasonable to those who have done optical grinding
work?


Okay, I may or may not know an awful lot about either electonics or
optics,
but I'm a darn good model builder. One of my pet projects is to build a
plastic model of every car I've owned and in the process I've learned a
lot
about handling plastic. To make a long story shorter, I've learned how
to
take a lucite windshield from a plastic car model that's been "ruined"
by
having glue run onto it and to repair it into something that's at least
as
good as new.

Go to www.micromark.com and look for a polishing kit. It has
abrasives -- I
can't call them sandpaper anymore -- in grits ranging from a low of 2400
up
to 12,000. That's right, a grit equivalent of Twelve Thousand!

Yikes!!!! That sounds like it's probably at least as fine (if not finer)
than what an ancient (1906 original publication date - my copy is a 1963
reprint edition) book I have on optics calls "100 minute emery" - As in,
"shovel raw, screened emery powder into a 12 foot tall, 3 foot wide pipe
full of water, stir the everlovin' bejeezus out of it for half an hour,
then let it stand undisturbed for 100 minutes. At the end of 100
minutes, drain off the liquid (catching it - it's the part you want) to
about a foot above the bottom, dumping what remains in the bottom back
onto the "raw material" pile, evaporate the liquid you drained in
whatever way works, and sell the powder that remains after the water is
gone as 100 minute emery". As of the publication date of the book, that
was apparently the finest abrasive that could be had, and was right at
the limit of being practical to "sort out".

I'll hit this "Micromark" place and see what they've got that would suit
my shoestring budget. Thanks for the suggestion!


IIRC, they sell a full polishing kit with 3"x5" sheets, individual ~6"sq
sheets, and a set of roughly 2" dia polishing pads. For most things I use
about every other grit, though I've been known to use every one for a really
critical job. They're best used wet but you can get a completely
different effect using them (mostly) dry. I think that the full set is ~$20
and probably the best place to start. After that, if it's not smooth
enough, you can use the Novus-brand of liquid polishing compounds to get an
ultra smooth shine. It's probably not something you need for this
application.

Norm

I have to say, what you have thought of, using black CDs...is absolutely
brilliant, and Ill be trying it myself.
Kim


"Don Bruder" wrote in message
...

This message crossed over into RPEM as an "in case anybody is interested
in my progress" update. Primarily aimed at the sci.electronics groups,
since the start of the whole thing was there, and appears to have
generated some interest there.

Some of you may recall my post a few weeks ago asking about IR LEDs,
filters, and other yakkety-yak about cheap ways to fab a light source
that puts out either pure IR, or "close enough to it", with little or no
visible component, for use in what boils down to a homebrew "Night
Vision" system designed around a video camera that has a
well-demonstrated sensitivity to IR in the same region of the spectrum
that TV remotes use.

After some false starts, I've managed what I think would count as a
reasonable "first cut" at the problem.

As those who are a bit more "techno-geeky" than the average Joe are
aware, the base material used in CDs *MUST* be IR transparent if the CD
is going to be readable by the (IR) laser in the player/reader.
Regardless of what color (blue, silver, gold, whatever) the reflective
material appears to be, or what color the base plastic shows up as in
visible light, the plastic that it gets coated onto has to be clear (or
close enough) to IR - A fact which permits such weirdness as the "black"
PlayStation CDs, odd-colored CD-R/CD-RW media, and so on. Which got me
thinking...

If one were to remove the reflective layer from, for instance, one of
the black PlayStation CDs, or the black CD-Rs that can be had, it would
stand to reason that one would then have a chunk of plastic that's (at
least reasonably) opaque to visible light, but transparent to IR.

After spending some time looking for, and a grand total of 8 dollars
acquiring, a few of these "black" CDs, I went to work on taking my idea
from the realm of theory to reality. And I'm pleased to say "it works!"

Preliminary testing, using a 3-cell Mag-Lite and a chunk of black CD
material with the reflective coating removed (with steel wool, as a
first attempt - I'm thinking some kind of solvent might be better as I
refine the concept) and cut down to a suitable size to replace the
normal clear "lens" of the Mag-Lite is showing great promise - Using
this as a light source, and my camcorder set to an appropriate zoom, I
can literally read the date off a quarter from the other side of a room
that my eyes perceive as pitch black other than a faint hint of red
where the flashlight is pointing - Not "darkroom quality" dark, by any
stretch, but close enough that my naked eye says "Dude!!! It's freakin'
DARK in here!"

Now to refine the idea...

Although the "filter" I built is functional, it seems to be doing a bit
too good of a job in scattering the light - Almost certainly due to the
fact that my method of removing the reflective material from the base
plastic of the CD left what's probably best described as a crude "ground
glass" finish on it - Instead of being the usual pristine "It's so
clear, it's like nothing is there at all" plastic, my scrubbing to
remove the coating has created a more-or-less matte finish that doesn't
transmit anywhere near as well as I had hoped. Kind of like a lens that
has somehow escaped from its proper holder, then spent the last few
months bouncing around in the bottom of your ditty-bag with all kinds of
things that a lens isn't supposed to associate with if it's going to
remain unscratched and clear until it has become "frosted" by all the
scratches it has acquired.

So at this point, I'm trying to figure out the best way to polish out
the scratches left by the steel wool, and get back to a truly
transparent (rather than translucent) finish on my homemade "filter".

Is there a reasonably easy way to do so? I don't know... I went after
the thing with 4-0 steel wool - as fine as I know how to locate - under
a layer of 40-weight motor oil, and although I did my best to avoid
excessive scrubbing (and therefore, scratching) I ended up with a
semi-matte, and therefore semi-translucent, finish on the filter. My
next move is probably to a 2400-grit wet/dry sandpaper that bills itself
as "Mirror-Brite", and to the touch, feels just about as abrasive as a
sheet of regular printer paper.

From there, my guess is that I'm going to need to move to something like
rubbing compound, rottenstone, or even ultra-fine jeweler's rouge.

Does this seem reasonable to those who have done optical grinding work?

Or am I way off base here?

--
Don Bruder - - New Email policy in effect as of Feb. 21,
2004.
Short form: I'm trashing EVERY E-mail that doesn't contain a password in
the
subject unless it comes from a "whitelisted" (pre-approved by me) address.
See http://www.sonic.net/~dakidd/main/contact.html for full details.

I have to say, what you have thought of, using black CDs...is absolutely
brilliant, and Ill be trying it myself.
Kim


"Don Bruder" wrote in message
...

This message crossed over into RPEM as an "in case anybody is interested
in my progress" update. Primarily aimed at the sci.electronics groups,
since the start of the whole thing was there, and appears to have
generated some interest there.

Some of you may recall my post a few weeks ago asking about IR LEDs,
filters, and other yakkety-yak about cheap ways to fab a light source
that puts out either pure IR, or "close enough to it", with little or no
visible component, for use in what boils down to a homebrew "Night
Vision" system designed around a video camera that has a
well-demonstrated sensitivity to IR in the same region of the spectrum
that TV remotes use.

After some false starts, I've managed what I think would count as a
reasonable "first cut" at the problem.

As those who are a bit more "techno-geeky" than the average Joe are
aware, the base material used in CDs *MUST* be IR transparent if the CD
is going to be readable by the (IR) laser in the player/reader.
Regardless of what color (blue, silver, gold, whatever) the reflective
material appears to be, or what color the base plastic shows up as in
visible light, the plastic that it gets coated onto has to be clear (or
close enough) to IR - A fact which permits such weirdness as the "black"
PlayStation CDs, odd-colored CD-R/CD-RW media, and so on. Which got me
thinking...

If one were to remove the reflective layer from, for instance, one of
the black PlayStation CDs, or the black CD-Rs that can be had, it would
stand to reason that one would then have a chunk of plastic that's (at
least reasonably) opaque to visible light, but transparent to IR.

After spending some time looking for, and a grand total of 8 dollars
acquiring, a few of these "black" CDs, I went to work on taking my idea
from the realm of theory to reality. And I'm pleased to say "it works!"

Preliminary testing, using a 3-cell Mag-Lite and a chunk of black CD
material with the reflective coating removed (with steel wool, as a
first attempt - I'm thinking some kind of solvent might be better as I
refine the concept) and cut down to a suitable size to replace the
normal clear "lens" of the Mag-Lite is showing great promise - Using
this as a light source, and my camcorder set to an appropriate zoom, I
can literally read the date off a quarter from the other side of a room
that my eyes perceive as pitch black other than a faint hint of red
where the flashlight is pointing - Not "darkroom quality" dark, by any
stretch, but close enough that my naked eye says "Dude!!! It's freakin'
DARK in here!"

Now to refine the idea...

Although the "filter" I built is functional, it seems to be doing a bit
too good of a job in scattering the light - Almost certainly due to the
fact that my method of removing the reflective material from the base
plastic of the CD left what's probably best described as a crude "ground
glass" finish on it - Instead of being the usual pristine "It's so
clear, it's like nothing is there at all" plastic, my scrubbing to
remove the coating has created a more-or-less matte finish that doesn't
transmit anywhere near as well as I had hoped. Kind of like a lens that
has somehow escaped from its proper holder, then spent the last few
months bouncing around in the bottom of your ditty-bag with all kinds of
things that a lens isn't supposed to associate with if it's going to
remain unscratched and clear until it has become "frosted" by all the
scratches it has acquired.

So at this point, I'm trying to figure out the best way to polish out
the scratches left by the steel wool, and get back to a truly
transparent (rather than translucent) finish on my homemade "filter".

Is there a reasonably easy way to do so? I don't know... I went after
the thing with 4-0 steel wool - as fine as I know how to locate - under
a layer of 40-weight motor oil, and although I did my best to avoid
excessive scrubbing (and therefore, scratching) I ended up with a
semi-matte, and therefore semi-translucent, finish on the filter. My
next move is probably to a 2400-grit wet/dry sandpaper that bills itself
as "Mirror-Brite", and to the touch, feels just about as abrasive as a
sheet of regular printer paper.

From there, my guess is that I'm going to need to move to something like
rubbing compound, rottenstone, or even ultra-fine jeweler's rouge.

Does this seem reasonable to those who have done optical grinding work?

Or am I way off base here?

--
Don Bruder - - New Email policy in effect as of Feb. 21,
2004.
Short form: I'm trashing EVERY E-mail that doesn't contain a password in
the
subject unless it comes from a "whitelisted" (pre-approved by me) address.
See http://www.sonic.net/~dakidd/main/contact.html for full details.