IR Cutoff filter

L

Leeper

Guest
I'm looking for a IR cutoff filter that is quite a bit cheaper than what
Edmund Optics sells. OCLI wants 21 dolars, I'd like to find something
cheaper. I need to pass wavelengths from 420-660nm, though if it attenuated
light on each end a bit, it would still be fine for me.

I'm putting it in front of a silicon photodiode, and need to kill the IR
response on this part.

Can anyone recommend some material/manufacturer? (I know devices like the
BPW21 already have this, but I need to use a different part).
 
"Leeper" <leeper@molalla.net> wrote in message
news:3tCdnYxefs8nxA_dRVn-vg@scnresearch.com...
I'm looking for a IR cutoff filter that is quite a bit cheaper than what
Edmund Optics sells. OCLI wants 21 dolars, I'd like to find something
cheaper. I need to pass wavelengths from 420-660nm, though if it
attenuated
light on each end a bit, it would still be fine for me.

I'm putting it in front of a silicon photodiode, and need to kill the IR
response on this part.

Can anyone recommend some material/manufacturer? (I know devices like the
BPW21 already have this, but I need to use a different part).


I've extracted what I guess is infrared filtering glass from a photocopier.
Click to expand...
It's light blue colour seem just like a dilute solution of copper sulphate,
which I once saw used as an infrared filter to prevent heating of liquid
helium while it's photographed.
I guess it's intended to give a response closer to the eye.

Scrim
 
Leeper wrote:
I'm looking for a IR cutoff filter that is quite a bit cheaper than what
Edmund Optics sells. OCLI wants 21 dolars, I'd like to find something
cheaper. I need to pass wavelengths from 420-660nm, though if it attenuated
light on each end a bit, it would still be fine for me.

I'm putting it in front of a silicon photodiode, and need to kill the IR
response on this part.

Can anyone recommend some material/manufacturer? (I know devices like the
BPW21 already have this, but I need to use a different part).
Click to expand...
By far, the cheapest way to do this is to pick a photo diode that
incorporates such a filter. What diode are you using. Perhaps
someone knows of a similar one that includes the filter.

As to filter materials, Schott KG series filter glasses are made for
this purpose.
http://www.noao.edu/kpno/filters/sgt/131t_sm.gif
The BG series has more red attenuation.
http://www.noao.edu/kpno/filters/sgt/123b_sm.gif
http://www.noao.edu/kpno/filters/sgt/123t_sm.gif

--
John Popelish
 
"Scrim" <none@none.com> wrote in message
news:A5tkc.392$DW.342@doctor.cableinet.net...
"Leeper" <leeper@molalla.net> wrote in message
news:3tCdnYxefs8nxA_dRVn-vg@scnresearch.com...
I'm looking for a IR cutoff filter that is quite a bit cheaper than what
Edmund Optics sells. OCLI wants 21 dolars, I'd like to find something
cheaper. I need to pass wavelengths from 420-660nm, though if it
attenuated
light on each end a bit, it would still be fine for me.

I'm putting it in front of a silicon photodiode, and need to kill the IR
response on this part.

Can anyone recommend some material/manufacturer? (I know devices like
the
BPW21 already have this, but I need to use a different part).


I've extracted what I guess is infrared filtering glass from a
photocopier.
It's light blue colour seem just like a dilute solution of copper
sulphate,
which I once saw used as an infrared filter to prevent heating of liquid
helium while it's photographed.
I guess it's intended to give a response closer to the eye.
Click to expand...
The heat filters used on slide projectors are made of a phosphate glass.
They might be the best source, if you can find an old one.

A light blue colour doesn't sound very promising, but you never know. If you
can get it put on a spectrophotometer and check the absorption spectrum in
the visible and near IR, that will tell you if it's any good.
--
Terry Harper
http://www.terry.harper.btinternet.co.uk/
 
On Fri, 30 Apr 2004 06:52:13 -0700, "Leeper" <leeper@molalla.net> wrote:

I'm looking for a IR cutoff filter that is quite a bit cheaper than what
Edmund Optics sells. OCLI wants 21 dolars, I'd like to find something
cheaper. I need to pass wavelengths from 420-660nm, though if it attenuated
light on each end a bit, it would still be fine for me.

I'm putting it in front of a silicon photodiode, and need to kill the IR
response on this part.

Can anyone recommend some material/manufacturer? (I know devices like the
BPW21 already have this, but I need to use a different part).
Click to expand...
Remember rubylith sheets? Charettes still sells them.




Remove "HeadFromButt", before replying by email.
 
Not sure what wavelength you really need to pass. If you are on a
tight budget, colored plastic or colored glass works well. The
bandpass is fairly wide, but probably not from 420 to 660 nm. It does
block IR well.

Any hobbly shop will sell colored glass (sometimes sold in broken
pieces for those doing stained glass windows). They also sell colored
plastic for the same purpose.

Cellophane is even cheaper, but it's thin and has more loss.

Are you doing free space laser communication??

A


I'm looking for a IR cutoff filter that is quite a bit cheaper than what
Edmund Optics sells. OCLI wants 21 dolars, I'd like to find something
cheaper. I need to pass wavelengths from 420-660nm, though if it attenuated
light on each end a bit, it would still be fine for me.

I'm putting it in front of a silicon photodiode, and need to kill the IR
response on this part.

Can anyone recommend some material/manufacturer? (I know devices like the
BPW21 already have this, but I need to use a different part).
Click to expand...


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"Leeper" <leeper@molalla.net> wrote in message
news:3tCdnYxefs8nxA_dRVn-vg@scnresearch.com...
I'm looking for a IR cutoff filter that is quite a bit cheaper than what
Edmund Optics sells. OCLI wants 21 dolars, I'd like to find something
cheaper. I need to pass wavelengths from 420-660nm, though if it
attenuated
light on each end a bit, it would still be fine for me.

I'm putting it in front of a silicon photodiode, and need to kill the IR
response on this part.

Can anyone recommend some material/manufacturer? (I know devices like the
BPW21 already have this, but I need to use a different part).

I have read that over-exposed films can be used as an IR filter
Click to expand...
Or use (a piece of) the reflector of 'cold' halogen lamp.

Wim
 
John Popelish <jpopelish@rica.net> wrote in message news:<409268B9.3E2EE77@rica.net>...
Leeper wrote:

I'm looking for a IR cutoff filter that is quite a bit cheaper than what
Edmund Optics sells. OCLI wants 21 dolars, I'd like to find something
cheaper. I need to pass wavelengths from 420-660nm, though if it attenuated
light on each end a bit, it would still be fine for me.

I'm putting it in front of a silicon photodiode, and need to kill the IR
response on this part.

Can anyone recommend some material/manufacturer? (I know devices like the
BPW21 already have this, but I need to use a different part).

By far, the cheapest way to do this is to pick a photo diode that
incorporates such a filter. What diode are you using. Perhaps
someone knows of a similar one that includes the filter.

As to filter materials, Schott KG series filter glasses are made for
this purpose.
http://www.noao.edu/kpno/filters/sgt/131t_sm.gif
The BG series has more red attenuation.
http://www.noao.edu/kpno/filters/sgt/123b_sm.gif
http://www.noao.edu/kpno/filters/sgt/123t_sm.gif
Click to expand...
I agree with John, with this addendum: If you're trying to improve
signal to noise ratio by reducing photocurrent due to ambient light,
this often proves to be an elusive goal. The reason is that shot noise
is proportional to the square root of bias current. So, you will
typically need to reduce ambient photocurrent by more than the square
of the passband transmittance of any filter. An example will make
this clear. Supposing that you reduce ambient photocurrent by a
factor of 2, for a shot noise reduction of about 40%. If your
passband transmittance is 60%, you will not have gained anything.

Paul Mathews
 
I'm trying to reduce the IR response, so that the sunlight IR doesn't mask
the
visible light I am trying to measure.

Modulation and all that will not work, I need to know the amplitude of each
Red, Green, and Blue device.

I'm using a reversed biased BPW34, and a the speeds I need to measure at,
it's 50pf (or whatever the
datasheet said) is wonderful, it helps me maintain 400nS rise response, to
make amplitude measurements 100 nS later, of the R, G, & B sources rather
easily. It only lacks a filter.

Something like the SFH2430 (?), has too much capacitance and internal
resistance for the method I am
using.

The BPW21 isn't bad, but it's cost of 4.55 is a bit high for me, plus it is
not in a surface mount package.

I found one device from Hamamastu that might possibly work, it's marginal,
I'll have to wait for it to
arrive to actually test it.

Any advice is greatly welcomed, thanks.

"Paul Mathews" <optoeng@pioneernet.net> wrote in message
news:ed443a10.0405012037.1fb9c829@posting.google.com...
John Popelish <jpopelish@rica.net> wrote in message
news:<409268B9.3E2EE77@rica.net>...
Leeper wrote:

I'm looking for a IR cutoff filter that is quite a bit cheaper than
what
Edmund Optics sells. OCLI wants 21 dolars, I'd like to find something
cheaper. I need to pass wavelengths from 420-660nm, though if it
attenuated
light on each end a bit, it would still be fine for me.

I'm putting it in front of a silicon photodiode, and need to kill the
IR
response on this part.

Can anyone recommend some material/manufacturer? (I know devices like
the
BPW21 already have this, but I need to use a different part).

By far, the cheapest way to do this is to pick a photo diode that
incorporates such a filter. What diode are you using. Perhaps
someone knows of a similar one that includes the filter.

As to filter materials, Schott KG series filter glasses are made for
this purpose.
http://www.noao.edu/kpno/filters/sgt/131t_sm.gif
The BG series has more red attenuation.
http://www.noao.edu/kpno/filters/sgt/123b_sm.gif
http://www.noao.edu/kpno/filters/sgt/123t_sm.gif

I agree with John, with this addendum: If you're trying to improve
signal to noise ratio by reducing photocurrent due to ambient light,
this often proves to be an elusive goal. The reason is that shot noise
is proportional to the square root of bias current. So, you will
typically need to reduce ambient photocurrent by more than the square
of the passband transmittance of any filter. An example will make
this clear. Supposing that you reduce ambient photocurrent by a
factor of 2, for a shot noise reduction of about 40%. If your
passband transmittance is 60%, you will not have gained anything.

Paul Mathews
Click to expand...
 
Sorry, don't recall rubylith.

I do miss the 5 cent bottles of pop.

"maxfoo" <maxfooHeadFromButt@punkass.com> wrote in message
news:fae590lvc0bh98j5hun2mdok9m5mobuseu@4ax.com...
On Fri, 30 Apr 2004 06:52:13 -0700, "Leeper" <leeper@molalla.net> wrote:

I'm looking for a IR cutoff filter that is quite a bit cheaper than what
Edmund Optics sells. OCLI wants 21 dolars, I'd like to find something
cheaper. I need to pass wavelengths from 420-660nm, though if it
attenuated
light on each end a bit, it would still be fine for me.

I'm putting it in front of a silicon photodiode, and need to kill the IR
response on this part.

Can anyone recommend some material/manufacturer? (I know devices like
the
BPW21 already have this, but I need to use a different part).


Remember rubylith sheets? Charettes still sells them.




Remove "HeadFromButt", before replying by email.
Click to expand...
 
Over exposed film is used to block visible and pass IR. I need the
opposite.

"Wim Ton" <wimton@blueyonder.co.uk> wrote in message
news:t4Skc.5865$NO7.3617@pathologist.blueyonder.net...
"Leeper" <leeper@molalla.net> wrote in message
news:3tCdnYxefs8nxA_dRVn-vg@scnresearch.com...
I'm looking for a IR cutoff filter that is quite a bit cheaper than what
Edmund Optics sells. OCLI wants 21 dolars, I'd like to find something
cheaper. I need to pass wavelengths from 420-660nm, though if it
attenuated
light on each end a bit, it would still be fine for me.

I'm putting it in front of a silicon photodiode, and need to kill the IR
response on this part.

Can anyone recommend some material/manufacturer? (I know devices like
the
BPW21 already have this, but I need to use a different part).

I have read that over-exposed films can be used as an IR filter
Or use (a piece of) the reflector of 'cold' halogen lamp.

Wim
Click to expand...
 
In article <YdqdnYpSlra6Fwnd4p2dnA@scnresearch.com>, leeper@molalla.net
says...
Over exposed film is used to block visible and pass IR. I need the
opposite.
Click to expand...
Why not use the IR reflective film designed for automotive window
applicaitons? Pick some up at PepBoys.

Marc
 
http://www.science-info.org/micro/docs/waterfilter.pdf gives the spectral
properties of copper sulfate solution as well as other dye solutions.


--
Gordon
Gordon Couger gcc@couger.com

I collect links on information related to light microscopes.
http://www.couger.com/microscope/links/gclinks.html
Please forward any links or information you think might be useful to others.

"Terry Harper" <Terry.Harper@btinternet.com> wrote in message
news:c6u1l6$ree$1@sparta.btinternet.com...
"Scrim" <none@none.com> wrote in message
news:A5tkc.392$DW.342@doctor.cableinet.net...

"Leeper" <leeper@molalla.net> wrote in message
news:3tCdnYxefs8nxA_dRVn-vg@scnresearch.com...
I'm looking for a IR cutoff filter that is quite a bit cheaper than
what
Edmund Optics sells. OCLI wants 21 dolars, I'd like to find something
cheaper. I need to pass wavelengths from 420-660nm, though if it
attenuated
light on each end a bit, it would still be fine for me.

I'm putting it in front of a silicon photodiode, and need to kill the
IR
response on this part.

Can anyone recommend some material/manufacturer? (I know devices like
the
BPW21 already have this, but I need to use a different part).


I've extracted what I guess is infrared filtering glass from a
photocopier.
It's light blue colour seem just like a dilute solution of copper
sulphate,
which I once saw used as an infrared filter to prevent heating of liquid
helium while it's photographed.
I guess it's intended to give a response closer to the eye.

The heat filters used on slide projectors are made of a phosphate glass.
They might be the best source, if you can find an old one.

A light blue colour doesn't sound very promising, but you never know. If
you
can get it put on a spectrophotometer and check the absorption spectrum in
the visible and near IR, that will tell you if it's any good.
--
Terry Harper
http://www.terry.harper.btinternet.co.uk/
Click to expand...
 
On Sat, 1 May 2004 22:42:26 -0700, "Leeper" <leeper@molalla.net> wrote:

Sorry, don't recall rubylith.
Click to expand...
Its a red masking film sold in art supply stores. You can get a 30"x40" sheet
for about $6.00 (us). Used to use it to make pcb long ago...

http://www.misterart.com/store/view.cfm?group_id=656&store=001









Remove "HeadFromButt", before replying by email.
 
On Fri, 30 Apr 2004 20:40:26 GMT, maxfoo
<maxfooHeadFromButt@punkass.com> wrote:

On Fri, 30 Apr 2004 06:52:13 -0700, "Leeper" <leeper@molalla.net> wrote:

I'm looking for a IR cutoff filter that is quite a bit cheaper than what
Edmund Optics sells. OCLI wants 21 dolars, I'd like to find something
cheaper. I need to pass wavelengths from 420-660nm, though if it attenuated
light on each end a bit, it would still be fine for me.

I'm putting it in front of a silicon photodiode, and need to kill the IR
response on this part.

Can anyone recommend some material/manufacturer? (I know devices like the
BPW21 already have this, but I need to use a different part).


Remember rubylith sheets? Charettes still sells them.
Click to expand...
This passes IR. He's trying to block IR.

RL
 
"Gordon Couger" <gcouger@NOSPAMprovalue.net> wrote in message
news:yr4lc.12276$bS1.412@okepread02...
"Terry Harper" <Terry.Harper@btinternet.com> wrote in message
news:c6u1l6$ree$1@sparta.btinternet.com...

The heat filters used on slide projectors are made of a phosphate glass.
They might be the best source, if you can find an old one.

A light blue colour doesn't sound very promising, but you never know. If
you
can get it put on a spectrophotometer and check the absorption spectrum
in
the visible and near IR, that will tell you if it's any good.

http://www.science-info.org/micro/docs/waterfilter.pdf gives the spectral
properties of copper sulfate solution as well as other dye solutions.
Click to expand...
Spectra in solution and spectra in glass are not necessarily the same,
mainly because there could be other species present. Cu2+ is likely to
absorb too much of the visible for him. If it was a pale green it would be
more promising.
--
Terry Harper
http://www.terry.harper.btinternet.co.uk/
 
On Sun, 02 May 2004 16:36:33 GMT, legg <legg@nospam.magma.ca> wrote:

This passes IR. He's trying to block IR.
Click to expand...
yeah, he wants aka IR notch filter.

Rosco makes cheap colored lighting filters for the photography/movie industry
in any color you want...I've got a free sample swatch from them, has every
filter they make.

http://www.rosco-ca.com/products/filters/filters-cinegel.html

Remove "HeadFromButt", before replying by email.
 
In article <dada90d1hvvp894b6q0e36li4mim7f88ns@4ax.com>, maxfoo wrote:
On Sun, 02 May 2004 16:36:33 GMT, legg <legg@nospam.magma.ca> wrote:


This passes IR. He's trying to block IR.

yeah, he wants aka IR notch filter.

Rosco makes cheap colored lighting filters for the photography/movie industry
in any color you want...I've got a free sample swatch from them, has every
filter they make.
Click to expand...
IR passes through all of them.

I believe they want it that way, so that filter gels in front of big hot
halogen lamps don't absorb the tons of IR and toast themselves in the
process.

- Don Klipstein (don@misty.com)
 
On Sun, 2 May 2004 18:50:23 +0000 (UTC), don@manx.misty.com (Don Klipstein)
wrote:

In article <dada90d1hvvp894b6q0e36li4mim7f88ns@4ax.com>, maxfoo wrote:
On Sun, 02 May 2004 16:36:33 GMT, legg <legg@nospam.magma.ca> wrote:


This passes IR. He's trying to block IR.

yeah, he wants aka IR notch filter.

Rosco makes cheap colored lighting filters for the photography/movie industry
in any color you want...I've got a free sample swatch from them, has every
filter they make.

IR passes through all of them.

I believe they want it that way, so that filter gels in front of big hot
halogen lamps don't absorb the tons of IR and toast themselves in the
process.

- Don Klipstein (don@misty.com)
Click to expand...
of course it does, no filter will absorb 100%, adding neutral density filter
gels along with a green, blue or violet color gel will lower the overall
attenuation.











Remove "HeadFromButt", before replying by email.
 
Leeper wrote:
I'm trying to reduce the IR response, so that the sunlight IR doesn't mask
the
visible light I am trying to measure.

Modulation and all that will not work, I need to know the amplitude of each
Red, Green, and Blue device.
(snip)
Click to expand...

Have you looked at any photo diodes that have narrow band visible
filters built in like:
http://www.photonics.com/spectra/newprods/XQ/ASP/newprodidnl.6444/QX/read.htm
http://www.photonics.com/spectra/newprods/XQ/ASP/newprodidd.3114/QX/read.htm


--
John Popelish
 
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