Re: 1W 405 source

Posted by Benjamin Smith on
URL: http://confocal-microscopy-list.275.s1.nabble.com/1W-405-source-tp7591310p7591327.html

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Attaching DMDs to microscopes is actually pretty common in optogenetics and
retinal research.  Here is an image of a DMD coupled into a BX-51 arm in
one of the labs I work with using one of the high power LEDs:
https://drive.google.com/file/d/1oFL0CQynji-hmkIDca002IZMmitwtksd/

In this setup we wanted a high power 450 nm output for optogenetics (>10
mW/mm^2 at the sample plane) while still having it usable as a fluorescent
microscope, so we used a 10W 450 nm LED (the one with the CPU cooler
attached) for the high power channel combined with a liquid light guide
from a xenon arc lamp for longer wavelengths.

Originally we tried a 3W 450 nm laser we bought off of eBay for $50 (which
to our surprise really was 3W optical output), but quickly realized that
the vast majority of losses in a DMD are at the microlens array used to
make the light uniform across the DMD.  Additionally the coherence of the
laser caused a strong speckling issue, which we tried to abate with 10m of
multimode fiber but was still pretty strong. We also had to couple at an
odd four degree of freedom offset to try to get as much of the field
covered as we could.

We then switched to the 10W LED, and since it covers the whole microlens
array, the field of illumination was perfectly uniform, and did not require
any odd 4 degree-of-freedom alignments.

One thing to keep in mind is that the DMD array itself is fairly big, so as
along as the LED die is appreciably smaller than the DMD itself, then the
etendue really won't cause a loss in intensity due to coupling, and will
only work in your favor to have a more uniform field of illumination.
Additionally, since these LEDs are intended to be used with DMDs, some of
them even have dies with a 4:3 or 16:9 aspect ratio for even better
efficiency.

And a quick side note, for anyone who want's to couple a DMD into a
microscope, I strongly recommend using the BX-51 arm.  It is easy to pull
out the lenses, and a Thorlabs SM1 lens tube fits neatly inside with only
minor modification.  You can also fit a TTL200 tube lens right behind the
manual shutter, giving you the perfect spacing to the back focal plane of
the objective.

Cheers,
   Ben Smith

On Tue, Sep 22, 2020 at 8:57 AM Zdenek Svindrych <[hidden email]> wrote:

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> *****
>
> Hi Antonio,
>
> We used to buy from Dragon lasers (China) many years back, now CNI Laser
> (again China) seems like a great source (no commercial interest).
>
> If you want to go super cheap, you can search eBay for laser engraving
> modules, some are 405 nm (but mostly 445 nm), you want something like "7W"
> at least, as it's the electric input power... And don't stare into the beam
> with your remaining eye!
>
> Andor uses a fiber shaker to homogenize the beam (and critical
> illumination, like their Borealis technology) for their Mosaic DMD devices,
> but I can't guarantee the amount of light you can couple into a 50 um or
> 100 um fiber from the eBay laser modules...
>
> UV LEDs sound cool, but the problem is the coupling efficiency (etendue).
> If your source is a 1 mm^2 LED chip, you can illuminate 1 mm^2 with a 1 NA
> objective lens with good efficiency (if you try hard). If you try to focus
> the light down to 0.3 mm^2, 90% of the light is lost... And higher power
> (more LED chips) won't help you get more light trough, only the optics may
> be simpler... Of course on top of that another 99% of light is blocked if
> you only have few DMD pixels "on"...
>
> I've seen papers where folks bolted a DMD digital projector to a
> microscope. Lie this one:
> https://drive.google.com/file/d/1IEfgKvZ0JrCUaaUPdnRFhUzT3phJO-D-/
>
> Best, zdenek
>
> On Mon, Sep 21, 2020 at 10:11 AM Antonio Jose Pereira <
> [hidden email]> wrote:
>
> > *****
> > To join, leave or search the confocal microscopy listserv, go to:
> > http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> > Post images on http://www.imgur.com and include the link in your
> posting.
> > *****
> >
> > Dear all,
> >
> > I'm looking for a 0.5-1W , 405nm, can have many spatial as well as
> > longitudinal modes, 405nm laser. This is to feed a photoconversion module
> > (Mosaic), a DMD-based system that wastes most power. That's why we need
> > such high power source.
> >
> > I appreciate if you could give suggestions on low-budget options, which
> > I'm failing to find ...
> >
> > Thank you so much,
> > Antonio
> >
> >
> >
> > Antonio Pereira
> > CID lab
> > i3S/IBMC, Universidade do Porto
> > Room 001.S2B, [phone] Ext. 6127
> >
>
>
> --
> --
> Zdenek Svindrych, Ph.D.
> Research Scientist - Microscopy Imaging Specialist
> Department of Biochemistry and Cell Biology
> Geisel School of Medicine at Dartmouth
>

--
Benjamin E. Smith, Ph. D.
Imaging Specialist, Vision Science
University of California, Berkeley
195 Life Sciences Addition
Berkeley, CA  94720-3200
Tel  [phone]
Fax [phone]
e-mail: [hidden email]
https://vision.berkeley.edu/faculty/core-grants-nei/core-grant-microscopic-imaging/