Dichroic mirror double reflections issue

[Lu Yan]

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Hi there,

I recently bought a dichroic mirror from Chroma (2mm thick reflecting
fluorescence,
https://www.chroma.com/products/custom-inventory/nc302987-zt670dcrb) for
our confocal fluorescence microscopy setup. But I found that with the
reflective side oriented correctly, at the reflection band, the reflected
beams seemed splitting into two and partially overlapping with each other
(ghost image?). This happens at a wide range of incident angles, and as I
rotated the dichroic (changing the angle), the "overlapped" reflection
alternated between partially overlapping and two distinct separated (by a
dark line in the middle) half circular beams.

Images of single fluorescence bead also showed 'side lobes'. So I was
wondering if anyone has experience on how to eliminate such effect? Is this
common for dichroics? Or it is specific for the one I have and I should get
another one?

Thank you very much in advance, and I wish you all Happy New Year!

Lu
-----------------------------------------------------
Lu Yan
Nanostructured Fibers and Nonlinear Optics Laboratory
Electrical and Computer Engineering
Boston University
8 St. Mary St., Boston, MA, 02215
617.353.0286 (office) | 617.358.5917 (lab)
[hidden email]
-----------------------------------------------------

[Sripad Ram-2]

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Hi Yan,
The issue sounds like the dichroic does not have an anti-reflection coating
on the non-reflective side. From the URL it was not clear if the optic has
the AR coating. Also are you using the dichroic at 45 degree incidence.

HTH

Sripad

On Wed, Dec 30, 2015 at 10:05 AM, Yan, Lu <[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.
> *****
>
> Hi there,
>
> I recently bought a dichroic mirror from Chroma (2mm thick reflecting
> fluorescence,
> https://www.chroma.com/products/custom-inventory/nc302987-zt670dcrb) for
> our confocal fluorescence microscopy setup. But I found that with the
> reflective side oriented correctly, at the reflection band, the reflected
> beams seemed splitting into two and partially overlapping with each other
> (ghost image?). This happens at a wide range of incident angles, and as I
> rotated the dichroic (changing the angle), the "overlapped" reflection
> alternated between partially overlapping and two distinct separated (by a
> dark line in the middle) half circular beams.
>
> Images of single fluorescence bead also showed 'side lobes'. So I was
> wondering if anyone has experience on how to eliminate such effect? Is this
> common for dichroics? Or it is specific for the one I have and I should get
> another one?
>
> Thank you very much in advance, and I wish you all Happy New Year!
>
> Lu
> -----------------------------------------------------
> Lu Yan
> Nanostructured Fibers and Nonlinear Optics Laboratory
> Electrical and Computer Engineering
> Boston University
> 8 St. Mary St., Boston, MA, 02215
> 617.353.0286 (office) | 617.358.5917 (lab)
> [hidden email]
> -----------------------------------------------------
>

[Lu Yan]

*****
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*****

Hi Sripad,

I am not sure if it has the AR coating on the other side. But I am now
getting help from the vendor. Hopefully it will solved soon. I am using it
with 45 degree incidence.

Happy New Year!

Lu

-----------------------------------------------------
Lu Yan
Nanostructured Fibers and Nonlinear Optics Laboratory
Electrical and Computer Engineering
Boston University
8 St. Mary St., Boston, MA, 02215
617.353.0286 (office) | 617.358.5917 (lab)
[hidden email]
-----------------------------------------------------

On Wed, Dec 30, 2015 at 6:04 PM, Sripad Ram <[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.
> *****
>
> Hi Yan,
> The issue sounds like the dichroic does not have an anti-reflection coating
> on the non-reflective side. From the URL it was not clear if the optic has
> the AR coating. Also are you using the dichroic at 45 degree incidence.
>
> HTH
>
> Sripad
>
> On Wed, Dec 30, 2015 at 10:05 AM, Yan, Lu <[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.
> > *****
> >
> > Hi there,
> >
> > I recently bought a dichroic mirror from Chroma (2mm thick reflecting
> > fluorescence,
> > https://www.chroma.com/products/custom-inventory/nc302987-zt670dcrb) for
> > our confocal fluorescence microscopy setup. But I found that with the
> > reflective side oriented correctly, at the reflection band, the reflected
> > beams seemed splitting into two and partially overlapping with each other
> > (ghost image?). This happens at a wide range of incident angles, and as I
> > rotated the dichroic (changing the angle), the "overlapped" reflection
> > alternated between partially overlapping and two distinct separated (by a
> > dark line in the middle) half circular beams.
> >
> > Images of single fluorescence bead also showed 'side lobes'. So I was
> > wondering if anyone has experience on how to eliminate such effect? Is
> this
> > common for dichroics? Or it is specific for the one I have and I should
> get
> > another one?
> >
> > Thank you very much in advance, and I wish you all Happy New Year!
> >
> > Lu
> > -----------------------------------------------------
> > Lu Yan
> > Nanostructured Fibers and Nonlinear Optics Laboratory
> > Electrical and Computer Engineering
> > Boston University
> > 8 St. Mary St., Boston, MA, 02215
> > 617.353.0286 (office) | 617.358.5917 (lab)
> > [hidden email]
> > -----------------------------------------------------
> >
>

[Craig Brideau]

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*****

This is an issue with any plate beamsplitter. The two possible solutions
are to AR-coat the non-working side, or have the working and back surface
be non-parallel. Some designs will have a slight wedge of a degree or so
between front and back surfaces to reduce these ghost reflections from the
non-working surface.

Happy New Year!
Craig Brideau


On Thu, Dec 31, 2015 at 9:16 AM, Yan, Lu <[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.
> *****
>
> Hi Sripad,
>
> I am not sure if it has the AR coating on the other side. But I am now
> getting help from the vendor. Hopefully it will solved soon. I am using it
> with 45 degree incidence.
>
> Happy New Year!
>
> Lu
>
> -----------------------------------------------------
> Lu Yan
> Nanostructured Fibers and Nonlinear Optics Laboratory
> Electrical and Computer Engineering
> Boston University
> 8 St. Mary St., Boston, MA, 02215
> 617.353.0286 (office) | 617.358.5917 (lab)
> [hidden email]
> -----------------------------------------------------
>
> On Wed, Dec 30, 2015 at 6:04 PM, Sripad Ram <[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.
> > *****
> >
> > Hi Yan,
> > The issue sounds like the dichroic does not have an anti-reflection
> coating
> > on the non-reflective side. From the URL it was not clear if the optic
> has
> > the AR coating. Also are you using the dichroic at 45 degree incidence.
> >
> > HTH
> >
> > Sripad
> >
> > On Wed, Dec 30, 2015 at 10:05 AM, Yan, Lu <[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.
> > > *****
> > >
> > > Hi there,
> > >
> > > I recently bought a dichroic mirror from Chroma (2mm thick reflecting
> > > fluorescence,
> > > https://www.chroma.com/products/custom-inventory/nc302987-zt670dcrb)
> for
> > > our confocal fluorescence microscopy setup. But I found that with the
> > > reflective side oriented correctly, at the reflection band, the
> reflected
> > > beams seemed splitting into two and partially overlapping with each
> other
> > > (ghost image?). This happens at a wide range of incident angles, and
> as I
> > > rotated the dichroic (changing the angle), the "overlapped" reflection
> > > alternated between partially overlapping and two distinct separated
> (by a
> > > dark line in the middle) half circular beams.
> > >
> > > Images of single fluorescence bead also showed 'side lobes'. So I was
> > > wondering if anyone has experience on how to eliminate such effect? Is
> > this
> > > common for dichroics? Or it is specific for the one I have and I should
> > get
> > > another one?
> > >
> > > Thank you very much in advance, and I wish you all Happy New Year!
> > >
> > > Lu
> > > -----------------------------------------------------
> > > Lu Yan
> > > Nanostructured Fibers and Nonlinear Optics Laboratory
> > > Electrical and Computer Engineering
> > > Boston University
> > > 8 St. Mary St., Boston, MA, 02215
> > > 617.353.0286 (office) | 617.358.5917 (lab)
> > > [hidden email]
> > > -----------------------------------------------------
> > >
> >
>