Back to the IR light source concept...

[Don Bruder]

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 - dakidd@sonic.net - 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.

 

[Norm Dresner]

"Don Bruder" <dakidd@sonic.net> wrote in message
news:KvTOc.5010$54.78633@typhoon.sonic.net...

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]

In article <%4UOc.159748$OB3.70829@bgtnsc05-news.ops.worldnet.att.net>,
"Norm Dresner" <ndrez@att.net> wrote:

"Don Bruder" <dakidd@sonic.net> wrote in message
news:KvTOc.5010$54.78633@typhoon.sonic.net...
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 - dakidd@sonic.net - 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.

 

[Norm Dresner]

"Don Bruder" <dakidd@sonic.net> wrote in message
news:rpUOc.5014$54.78410@typhoon.sonic.net...

In article <%4UOc.159748$OB3.70829@bgtnsc05-news.ops.worldnet.att.net>,
"Norm Dresner" <ndrez@att.net> wrote:

"Don Bruder" <dakidd@sonic.net> wrote in message
news:KvTOc.5010$54.78633@typhoon.sonic.net...
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

 

[Neil]

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


"Don Bruder" <dakidd@sonic.net> wrote in message
news:KvTOc.5010$54.78633@typhoon.sonic.net...

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 - dakidd@sonic.net - 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.

 

[columbotrek]

I have never found any economy in building what I can buy. Just takes
to much time. You can buy inexpensive IR gells from which you can cut
out what you need. Look for a low pass gell at about 750nm. A cheep way
is to process a sheet of unexposed slide film if you need a large piece.
Or take some of the ends from a processed roll of 35mm or 120 slide
film. You can layer them if you need it darker to visable light.
Performance wise though, it is going to be hard to beat a real IR
illuminator like what is use on night vision devices. Oh by the way,
all CCD sensors are sensitive to IR (down to 1300nm) light. All you
need to do is to remove the camera's high pass filter and replace it
with a clear to IR glass. I have been playing around with a CCD digital
camera with a Hoya R72 (720nm low pass) It is an Olympus 2020 and I am
comparing it to Kodak HIE film with the same filter. The film is about
5 stops faster than the digital sensor.

Don Bruder wrote:

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.

 

[Don Bruder]

In article <Sa0Pc.8484$Xn.5197@fed1read05>, columbotrek <me@cox.net>
wrote:

I have never found any economy in building what I can buy. Just takes
to much time. You can buy inexpensive IR gells from which you can cut

HAH! Cheapest IR-pass filters I was able to find, whether gell, plastic,
or glass, are *WAY* beyond my budget for this sort of tinkering. Besides
- Doing it myself is (A) Entertaining (B) Educational and (C) a fun
challenge. (Hmm... maybe C should read "both of the above?")

Performance wise though, it is going to be hard to beat a real IR
illuminator like what is use on night vision devices.

Performance is secondary to price. A "real" illuminator with any kind of
range is, like buying the IR-pass filter, way outside my budget, even
with the idea of going for the cheapest available.

Oh by the way,
all CCD sensors are sensitive to IR (down to 1300nm) light.

Replace "all" with "most", and I'll buy into that last statement. Some
of them are very IR sensitive. Others barely notice IR at all, while
still others are effectively totally blind to it. Depends on the maker
and the process they used. External pre-filtering obviously effects the
accuracy of that statement...

--
Don Bruder - dakidd@sonic.net - 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.

 

[croweflight]

Don Bruder wrote:

HAH! Cheapest IR-pass filters I was able to find, whether gell, plastic,
or glass, are *WAY* beyond my budget for this sort of tinkering. Besides
- Doing it myself is (A) Entertaining (B) Educational and (C) a fun
challenge. (Hmm... maybe C should read "both of the above?")
Is unexposed but developed scrap slide film beyond your budget? Perhaps

you just need something to keep occupied with. Like polishing old CDs.

Replace "all" with "most", and I'll buy into that last statement. Some
of them are very IR sensitive. Others barely notice IR at all, while
still others are effectively totally blind to it. Depends on the maker
and the process they used. External pre-filtering obviously effects the
accuracy of that statement...

The CCD sensors are before they place a high pass filter in front of it

which is why I suggested to remove the thing and replace it with clear
glass to preserve the focus. Which is just what Sony does for their
night mode. The lever moves the high pass filter out of the way. But
now they also strap the aperture wide open when you place it in night
mode. So if you use it in the daylight with an IR low pass filter the
sensor saturates.

 

[Don Bruder]

In article <sKFPc.5111$Oi.15@fed1read04>,
croweflight <croweflight@cox.NoOp.net> wrote:

Don Bruder wrote:
HAH! Cheapest IR-pass filters I was able to find, whether gell, plastic,
or glass, are *WAY* beyond my budget for this sort of tinkering. Besides
- Doing it myself is (A) Entertaining (B) Educational and (C) a fun
challenge. (Hmm... maybe C should read "both of the above?")
Is unexposed but developed scrap slide film beyond your budget? Perhaps
you just need something to keep occupied with. Like polishing old CDs.

Ahh, I get it... post a response so you can make a snide remark. FTR,
it's my time to do with as I please, so you can take your snotty
commentary and shove it where the sun don't shine.

Replace "all" with "most", and I'll buy into that last statement. Some
of them are very IR sensitive. Others barely notice IR at all, while
still others are effectively totally blind to it. Depends on the maker
and the process they used. External pre-filtering obviously effects the
accuracy of that statement...

The CCD sensors are before they place a high pass filter in front of it
which is why I suggested to remove the thing and replace it with clear
glass to preserve the focus. Which is just what Sony does for their
night mode. The lever moves the high pass filter out of the way. But
now they also strap the aperture wide open when you place it in night
mode. So if you use it in the daylight with an IR low pass filter the
sensor saturates.

Wasn't that little addition (cranking the aperture wide open in "night"
mode) in response to the "Oh my god! If it's used that way in daylight,
it's able to take nude pictures of clothed people!!! Oh, the horror! It
MUST BE STOPPED!" garbage that started flowing when somebody actually
tried it?

I guess saturating the sensor would do a good job of stopping such
things... A picture/footage isn't worth much if it's just a white-out.

--
Don Bruder - dakidd@sonic.net - 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.

 

[Sir Charles W. Shults III]

Just as a note- if you are removing aluminum based reflective coatings
(virtually all of them!), then never never scrub them off with abrasives.
Dip them in ammonia and it will dissolve the aluminum right away, leaving
the plastic pristine and perfect.

Cheers!

Sir Charles W. Shults III, K. B. B.
Xenotech Research
321-206-1840

 

[Don Bruder]

In article <42WQc.35817$DZ.4328296@twister.tampabay.rr.com>,
"Sir Charles W. Shults III" <NOaichipSPAM@cfl.rr.com> wrote:

Just as a note- if you are removing aluminum based reflective coatings
(virtually all of them!), then never never scrub them off with abrasives.
Dip them in ammonia and it will dissolve the aluminum right away, leaving
the plastic pristine and perfect.

Excellent idea. But what about "breaking the glaze" of the coating over
top of the aluminum? Doesn't seem to me like ammonia will be very
effective on aluminum it can't get in contact with...

--
Don Bruder - dakidd@sonic.net - 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.

 

[Chris Hodges]

Don Bruder <dakidd@sonic.net> wrote in message news:<KvTOc.5010$54.78633@typhoon.sonic.net>...
<snip>

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!"
snip

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".

Have you tried (in other words it probably won't work, but you never
know) aplying a water based clear varnish to the ground side. If the
refractive index is similar enough to the plastic (tinted
polycarbonate I would guess - normal polycarbonate has n~1.56) and you
can get good coverage right into the grooves (you might need to dilute
with water) AND you get an even layer it might be good enough - it's
light delivery, not imaging that you're after. Underdriving the bulb
will increase the amount of IR at the expense of vis as previously
mentioned, so perhaps the bulb from a 4 or 6 cell maglite would help
as well.

Chris

(p.s. google has given me 1.37-1.48 for refractive index of varnishes)

 

[Don Bruder]

In article <d36a713e.0408090707.8f4f826@posting.google.com>,
chrisjhodges@yahoo.com (Chris Hodges) wrote:

Don Bruder <dakidd@sonic.net> wrote in message
news:<KvTOc.5010$54.78633@typhoon.sonic.net>...
snip
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!"
snip

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".

Have you tried (in other words it probably won't work, but you never
know) aplying a water based clear varnish to the ground side.

Not an actual "varnish", but the transmission DID seem at least somewhat
better during my "pre-testing testing" - before I managed to get all the
40-weight washed off the piece. I was kinda half-considering trying to
shellac/varnish/clear-coat the thing in hopes of filling the scratches,
but haven't really made a lot of progres on the idea since the initial
"feasibility study", due to being handed yet another fistful of "hot
irons" to add to my "fire".

Another couple of options I've pondered, but haven't really gone
anywhere with so far are flame-polishing (before I try that, I'll need
to do some playing to figure out if it even *CAN* work for this
material) and coats of beeswax (Got plenty of that available, for
nothing more than the effort of going out to the hive and pulling a
frame...) or perhaps a beeswax/alcohol mix similar to varnish/shellac.

This is clearly going to end up being one of those "ongoing project"
projects - As I've got time, ambition, and materials, I'll probably
tinker with it on and off for the next year or so, until I either get
bored, or get it to what I consider "done enough".

If the
refractive index is similar enough to the plastic (tinted
polycarbonate I would guess - normal polycarbonate has n~1.56) and you
can get good coverage right into the grooves (you might need to dilute
with water) AND you get an even layer it might be good enough - it's
light delivery, not imaging that you're after. Underdriving the bulb
will increase the amount of IR at the expense of vis as previously
mentioned, so perhaps the bulb from a 4 or 6 cell maglite would help
as well.

Counterintuitive...

I don't see an underdriven filament putting off a larger *ABSOLUTE*
quantity of IR - Rather, I see the relationship between mount of IR and
visible output changing - As in the IR output stays (nearly) the same
regardless of voltage, but the visible component falls off with the
voltage drop until the point where visible output is nearly nil, but the
IR output is just as strong as ever.

That's not much different than running a filter - No net increase in
absolute brightness, but a relative increase in IR output compared to
visible. At some point beyond that (exactly where, I'm not sure, but I
*KNOW* that point MUST exist) the IR output is going to start dropping
along with the voltage.

The "increase IR versus visible output" concept is good. But how does
dropping the voltage *INCREASE* the actual IR output? Or is it as I say
above - namely, the IR radiation stays (pretty much, and only down to a
certain point) the same, but I don't have to "work so hard" to remove
the smaller amount of visible light to get near-pure IR?

--
Don Bruder - dakidd@sonic.net - 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.

 

[Jim]

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?

Some modern automobiles use a plastic headlight assembly that 'fogs'
with age.. some fog fairly quickly. Inexpensive kits are become
available to polish the plastic lenses back to clear.. if the
scratches aren't too deep on your lens, this might work for you.

Search on fogged headlight lenses... here's one product..

http://www.autodetailingsolutions.com/clear_plastic_care.htm

Hope this helps..

Jim

 

[Chris Hodges]

Don Bruder <dakidd@sonic.net> wrote in message news:<LsPRc.6561$54.101665@typhoon.sonic.net>...

I don't see an underdriven filament putting off a larger *ABSOLUTE*
quantity of IR - Rather, I see the relationship between mount of IR and
visible output changing - As in the IR output stays (nearly) the same
regardless of voltage, but the visible component falls off with the
voltage drop until the point where visible output is nearly nil, but the
IR output is just as strong as ever.

I'll try and model this and get back to you - but if it's battery
driven (i.e. if you really want to use the maglite) it will improve
battery life.

Chris

 

[John Fields]

On Sat, 31 Jul 2004 20:43:22 GMT, Don Bruder <dakidd@sonic.net> wrote:

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?

---
You're probably OK, if you want to go through the ritual of
never-ending polishing, but there _are_ commercially available
polishing compounds out there which might make your life easier.

Check out

http://www.noscratch.com/novus/index.shtml

Or, you might want to go a completely different route and use an
acrylic designed specifically for the purpose.

Cyro Industries has infrared transmitting acrylic, "ACRYLITE GP" with
a color # of 1146-0 which ought to work for you. Check this out:

http://cyro.custhelp.com/cgi-bin/cyro.cfg/php/enduser/std_alp.php?p_sid=rANE2Bih&p_lva=&p_li=&p_page=1&p_prod_lvl1=4&p_prod_lvl2=6&p_cat_lvl1=%7Eany%7E&p_cat_lvl2=%7Eany%7E&p_search_text=1146-0&p_new_search=1&p_search_type=3

for spec's.

--
John Fields

 

[Don Bruder]

In article <d36a713e.0408100613.15b7ba92@posting.google.com>,
chrisjhodges@yahoo.com (Chris Hodges) wrote:

Don Bruder <dakidd@sonic.net> wrote in message
news:<LsPRc.6561$54.101665@typhoon.sonic.net>...
I don't see an underdriven filament putting off a larger *ABSOLUTE*
quantity of IR - Rather, I see the relationship between mount of IR and
visible output changing - As in the IR output stays (nearly) the same
regardless of voltage, but the visible component falls off with the
voltage drop until the point where visible output is nearly nil, but the
IR output is just as strong as ever.

I'll try and model this and get back to you - but if it's battery
driven (i.e. if you really want to use the maglite) it will improve
battery life.

Well, the whole point of this concept is a portable unit, so battery
power is probably the only reasonable way I can go. Nothing says it
*HAS* to be a maglight - that was just my "proof of concept" whack at
the problem - but it probably will have to be battery powered to make it
practical/portable.

--
Don Bruder - dakidd@sonic.net - 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]

In article <ssthh0l2thu46jc2or3n8n7n27pde6f97n@4ax.com>,
John Fields <jfields@austininstruments.com> wrote:

Or, you might want to go a completely different route and use an
acrylic designed specifically for the purpose.

Cyro Industries has infrared transmitting acrylic, "ACRYLITE GP" with
a color # of 1146-0 which ought to work for you. Check this out:

http://cyro.custhelp.com/cgi-bin/cyro.cfg/php/enduser/std_alp.php?p_sid=rANE2B
ih&p_lva=&p_li=&p_page=1&p_prod_lvl1=4&p_prod_lvl2=6&p_cat_lvl1=%7Eany%7E&p_ca
t_lvl2=%7Eany%7E&p_search_text=1146-0&p_new_search=1&p_search_type=3

for spec's.

Hmmm... that one has possibilities, though I cringe at the idea of how
much $$ it will take to get ahold of the stuff... When looking at
IR-transmitting photographic filters, I was routinely spotting prices in
the $150-$200/6 inch square range for plastic filters - Which is why I
ended up going with a "make-do" chopped out of a black CD-R. Even the
gell filters (which are very likely to have *VERY* short working
lifespans) to transmit IR were ridiculously priced - a 70MM round was
tagged at $89, fergawdsake! My budget (which is mostly imaginary,
practically speaking) for this project can't even CONSIDER those kind of
prices! And glass? HAH! If I can't afford the "cheap" gells and/or
plastic, then I don't even need to consider glass, since that seems to
routinely be about 130-200% more expensive than the corresponding
plastic filter.

Now to see if I can find someplace that will tell me how much this
"Acrylite" stuff costs... I note a glaring lack of any reference to
pricing for it at the link you posted. Most often, I've found that
situation to be a red-flag for "If you need to ask "how much?", it's
more than you can afford. Have a nice day, and don't let the door hit
you in the arse as you leave." materials.

Still, now that I know the stuff exists, I might be able to find
someplace that sells it in reasonable quantities, at reasonable prices.
More investigation is in order, obviously...

--
Don Bruder - dakidd@sonic.net - 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.

 

[Chris Hodges]

Don Bruder <dakidd@sonic.net> wrote in message news:<un9Sc.6756$54.105069@typhoon.sonic.net>...

In article <d36a713e.0408100613.15b7ba92@posting.google.com>,
chrisjhodges@yahoo.com (Chris Hodges) wrote:

Don Bruder <dakidd@sonic.net> wrote in message
news:<LsPRc.6561$54.101665@typhoon.sonic.net>...
I don't see an underdriven filament putting off a larger *ABSOLUTE*
quantity of IR - Rather, I see the relationship between mount of IR and
visible output changing - As in the IR output stays (nearly) the same
regardless of voltage, but the visible component falls off with the
voltage drop until the point where visible output is nearly nil, but the
IR output is just as strong as ever.

I'll try and model this and get back to you - but if it's battery
driven (i.e. if you really want to use the maglite) it will improve
battery life.

Well, the whole point of this concept is a portable unit, so battery
power is probably the only reasonable way I can go. Nothing says it
*HAS* to be a maglight - that was just my "proof of concept" whack at
the problem - but it probably will have to be battery powered to make it
practical/portable.

I modelled the blackbody curves in excel, and you're right, by quite a
margin - I don't know whether the power requirement or the IR output
would fall faster for a given emitter as you drop the temperature
(assuming temperature control for convenience) so it might not even
save battery life.

The maglite could be a good way to go - the focussing output would
seem to help, even if you have a diffuser effect from the vis blocking
filter.

Did you ever try multiple visible gel filters - these tend to be cheap
(I seem to remember Ł10 (~$18)/sq foot), and for a maglite even
offcuts would be enough, so even cheaper if you have a friendly
theatrical/DJ supplies shop that does stage lighting.
e.g. Lee filters (www.leefilters.com) "Blood red 789" transmits only
1% visible in the far red, combine with (e.g.) "Bray blue 722" should
do it. I found my old swatch book recently (since the last thread) so
I can have a look with a lamp and digital camera later. With anything
less than hundreds of watts they'll last forever.

Chris

 

[Don Bruder]

In article <d36a713e.0408110632.299b59de@posting.google.com>,
chrisjhodges@yahoo.com (Chris Hodges) wrote:

I modelled the blackbody curves in excel, and you're right, by quite a
margin - I don't know whether the power requirement or the IR output
would fall faster for a given emitter as you drop the temperature
(assuming temperature control for convenience) so it might not even
save battery life.

Nice to find out that the numbers match my world picture Seriously!
I was having a hard time swallowing the idea that IR output would
increase (in any way other than relative to the amount of visible light)
due to a voltage drop.

The maglite could be a good way to go - the focussing output would
seem to help, even if you have a diffuser effect from the vis blocking
filter.

Indeed. I'm thinking that no matter what the raw light source ends up
being, whether a "pure IR" source without filtering, or a filter system
in front of a visble source, it will be mandatory to have a
variable-focus beam.

Did you ever try multiple visible gel filters - these tend to be cheap
(I seem to remember ?10 (~$18)/sq foot), and for a maglite even
offcuts would be enough, so even cheaper if you have a friendly
theatrical/DJ supplies shop that does stage lighting.

That has been suggested, but at this point, I've done nothing with it.
At the very least, it seems to me that it would be worth trying.

I can have a look with a lamp and digital camera later. With anything
less than hundreds of watts they'll last forever.

Hmmm... maybe it's just me and my misinformation, but I've always been
under the impression that gels are the "cheap to buy this one, but
expensive as hell in the long term due to needing frequent replacement"
solution. My limited time "on the boards" (credited in the program as
"Soldier with a line" - <chuckle&gt in a 6 week run of Jesus Christ
Superstar at a local playhouse showed me a lighting guy *CONSTANTLY*
griping about needing to chase up into the flys to replace gels -
sometimes before each run of the show, and particularly the reds. From
that, I reached the conclusion that gels are, at best, a "make-do",
rather than a permanent solution. And the prices... <choke> At one
point, I overheard him saying something like "There goes another hundred
bucks" while he was working on cutting a blue one to shape.

--
Don Bruder - dakidd@sonic.net - 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.