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Re: general laser babble

While a IR gel filter would be easy to cut to shape, there exists at least one
major problem, and a few minor ones, with gel type filters. This being that they
tend to loose their pigments, and become blotchy, when they become damp/wet. An
almost unavoidable occurance when mounted on a auto's exterior. This is esp.true
of those intended  for use in photographic applications, ie manufactured by
Kodak Another problem with gel tpye filters is that when exposed to very high
intensity light sources for prolonged periods they get a bit bleached out and no
longer provide the proper filtration, not a huge problem considering their
relatively low cost. Their final problem is that they are VERY subseptable to
melting when exposed to high heat levels, avoided in photographic apps. by using
special heat absorbing glass condensors that allow for maximum light
transmission with reduced heat transmission.

Another possibility might be to use a deep red,  #25, photographic filter. A sub
for a proper IR filter when exposing IR film. That is unless the cops see you
coming first.

Also Another source for IR filters is a well stocked camera shop, not a mall
chain store, as they will most likely be able to tell you what is available. I
believe that Kodak makes a 5.25 inch diameter glass IR filter, as their are lots
of uses for IR photography.

sean 96A6q

HAREST@allenbrook.iix.com wrote:

> I too had this info stored from years back.  However, by the time I'd gotten
> off my butt to implement this, Edmund's had discontinued that particular
> item.  Not sure what the filtering range of this discontinued filter was,
> but I believe laser is in the 908nm range.  Allowing that range through, and
> filtering out the visible is the general desire.
> They still make similar glass IR filters (730-1100nm), however the size is
> 12mm dia (#46082) or 25mm square (#46086) for $17.75 and $32.70
> respectively.  Don't think I want to patch together a larger area of filter
> from such small pieces, and I'm not sure if a single small opening in a
> driving light cover would suffice?  Anyone care to speculate?
> They do have plastic IR filters (gels) in larger sizes.  5.5" square
> (#43951) and 4"x5" (#43954) for $24.50 and $11.75 respectively.  These pass
> 700-2200nm.  These have a thickness of 1.5mm so I'm not sure how resistant
> to heat they will be.  Perhaps sandwiching a filter between some plexi will
> work?  Speculation anyone?  This isn't my field, but I'm interested in
> making it work. One laser ticket is enough thanks!
> Perhaps some other scientific suppliers will have something similar.  Anyone
> care to investigate?  I didn't have much luck when I looked into it earlier
> this year.  Most have some small but incredibly expensive pieces only...
> Later,
> -S
> Stott Hare
> 85 Callaway 4ktq
> 84 4ktq (MC conversion in progress)
> -----Original Message-----
> From: frankbauer@thevine.net
> Sent: Thursday, September 10, 1998 9:10 PM
> To: quattro@coimbra.ans.net
> Subject: general laser babble
> joe sez:
> >...
> >...
> > The parts for this project can be had cheaply at your local NAPA
> >store...  The only part that I'm not sure about is the IR-Pass filter.
> >The magazine mentioned that you could get the filter from most scientific
> >supply companies...
> >...
> >    If I can help provide any info on the above, gimmie a yell..
> >...
> i have a note here taken from a post from several years that say that
> edmunds scientific (609-573-6250) sells a 5-3/8" diameter IR filter
> (#A60033) for $39.95.
> not sure how accurate or up-to-date this info is...
> frank
> to: IN:jfgovern@mailbox.syr.edu
> cc: IN:quattro@coimbra.ans.net