[Laser] cheap filters

Thu, 26 Jun 2003 01:34:21 -0400

Note that most commonly available materials (glasses, plexiglas, cellophane,
etc.) will not attenuate 850 nm. To exclude IR as well as unwanted visible
you need a bandpass filter. Intor, Inc. (www.intor.com) has dielectric
narrowband filters easily as good as Edmund's at half the price. (I am not
affiliated in any way with Intor, just a satisfied customer). They also
offer very reasonably priced integrated filter/photodiode combos. Most
bandpass filters are not rated to cover such a wide range as 630-700 as they
usually have a 10 nm FWHM (some LED filters can do 50 nm or more) however
they can be tuned over quite a wide range, perhaps as wide as you ask and
more, by simply tilting them (of course will still pass at best only their
rated FWHM passband at any given position, just at different wavelengths).
73, Jon

-----Original Message-----
From: Phil Lefever <[email protected]>
To: [email protected] <[email protected]>
Date: Wednesday, June 25, 2003 9:45 PM
Subject: Re: [Laser] cheap filters

>At 05:13 PM 6/25/03 -0400, you wrote:
>>Anyone have any suggestions on cheap bandpass filters for visible red
>>lasers?  I'm looking for something that would pass 630-700nm, but have
>>substantial attenuation at 850nm.  The reason for this is to get rid of
>>the 850nm line spectrum from sodium lamps.  I'm thinking about cellophane
>>or plexiglass that I might be able to find easily.  I thought I would ask
>>here before I went to the lab via the craft store
>
>A deep red filter should help a lot. If you want to actually know the
>spectrum pass band look into photographic filters like the Cokin
>made gel system. You can probably find their spectral curves on
>their web site.
>
>Another possibility, though more expensive, is the use of Astronomical
>light pollution reduction filters. These are more complicated thin film
>filters instead of just dyed glass. These can have extreme out of band
>attenuation with minimal attenuation of desired wavelengths. A good
>choice would be the Orion SkyGlow filter. It will pass about 95%+ at
>650nm and will GREATLY attenuate the major lines from both Sodium
>and Mercury vapor street lights. Look at www.telescope.com and do
>a search on Skyglow Filter. As I said these are fairly expensive but
>still less then 1/2 the price of Edmund's LASER band pass filters!
>
>73
>
>Phil
>
>
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