Reflected image -> astigmatism

[Philip Nicovich]

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All,

I'm trying to set up a dual-camera TIRF system using two cameras and a
dichroic splitter before the pair of matched tube lenses.  The reflected
arm has some serious astigmatism that doesn't change with swapping cameras
or tube lenses or playing with the alignment.  The transmitted arm is
fine.  Swapping dichroics has a little bit of an effect, but not as much as
I would think.  I certainly haven't found one that actually works well in
my stash.

Any tricks to confirming that the dichroic splitter is causing the
problem?  Or what I should be looking for in a proper filter to ensure this
doesn't happen again?

Thanks,
Rusty



--

*Philip R Nicovich*

*Research Fellow,  **ARC Centre of Excellence in Advanced Molecular Imaging*



THE UNIVERSITY OF NEW SOUTH WALES

UNSW  SYDNEY  NSW  2052  AUSTRALIA

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E: [hidden email] <[hidden email]>


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[John Oreopoulos]

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Dear Phillip,

I have encountered this issue once before and it did turn out to be a warped dichroic mirror. We couldn't determine if it was how the mirror was made or how it was mounted/glued however, but we saw astigmatism in the reflected path like you describe. For sure it was an anomaly in out stock of mirrors. Since you're seeing it on multiple mirrors on your end, I would suggest that perhaps your mirrors need to be thicker, or possibly, there is a defect in the camera lens being used to image the reflected beam. You could test the latter hypothesis by swapping the two camera lenses and seeing if the astigmatism remains or switches to the transmitted pathway.

Cheers,

John Oreopoulos
Staff Scientist
Spectral Applied Research Inc.
A Division of Andor Technology
Richmond Hill, Ontario
Canada
www.spectral.ca

On 2015-11-02, at 2:28 AM, Philip Nicovich 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.
> *****
>
> All,
>
> I'm trying to set up a dual-camera TIRF system using two cameras and a
> dichroic splitter before the pair of matched tube lenses.  The reflected
> arm has some serious astigmatism that doesn't change with swapping cameras
> or tube lenses or playing with the alignment.  The transmitted arm is
> fine.  Swapping dichroics has a little bit of an effect, but not as much as
> I would think.  I certainly haven't found one that actually works well in
> my stash.
>
> Any tricks to confirming that the dichroic splitter is causing the
> problem?  Or what I should be looking for in a proper filter to ensure this
> doesn't happen again?
>
> Thanks,
> Rusty
>
>
>
> --
>
> *Philip R Nicovich*
>
> *Research Fellow,  **ARC Centre of Excellence in Advanced Molecular Imaging*
>
>
>
> THE UNIVERSITY OF NEW SOUTH WALES
>
> UNSW  SYDNEY  NSW  2052  AUSTRALIA
>
> T: [phone]
>
> E: [hidden email] <[hidden email]>
>
>
> CRICOS Provider No. 00098G

[Chris Baumann]

********COMMERCIAL RESPONSE**************

Hi Rusty,

89 North/Chroma sell the Cairn emission splitters (both single and multiple cameras) and have found that with a 1 mm thick dichroic, you will almost always have some distortions in the reflected image.  We now strongly recommend a minimum of a 2 mm thick dichroic and be sure to specify laser quality/UltraFlat to ensure a higher degree of flatness.  

The way the dichroic is held also makes a big difference.  Gluing or clamping too hard at the corners can also impart curvature in the dichroic.

Feel free to contact me off line if you need any specific information.

Best regards,

Chris



-----Original Message-----
From: Confocal Microscopy List [mailto:[hidden email]] On Behalf Of Philip Nicovich
Sent: Monday, November 02, 2015 2:29 AM
To: [hidden email]
Subject: Reflected image -> astigmatism

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All,

I'm trying to set up a dual-camera TIRF system using two cameras and a dichroic splitter before the pair of matched tube lenses.  The reflected arm has some serious astigmatism that doesn't change with swapping cameras or tube lenses or playing with the alignment.  The transmitted arm is fine.  Swapping dichroics has a little bit of an effect, but not as much as I would think.  I certainly haven't found one that actually works well in my stash.

Any tricks to confirming that the dichroic splitter is causing the problem?  Or what I should be looking for in a proper filter to ensure this doesn't happen again?

Thanks,
Rusty



--

*Philip R Nicovich*

*Research Fellow,  **ARC Centre of Excellence in Advanced Molecular Imaging*



THE UNIVERSITY OF NEW SOUTH WALES

UNSW  SYDNEY  NSW  2052  AUSTRALIA

T: [phone]

E: [hidden email] <[hidden email]>


CRICOS Provider No. 00098G

[Andrew York]

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I agree with John and Chris, you probably have a warped dichroic. You can
confirm using a laser pointer. Bounce the beam off your dichroic, and let
it propagate several meters (the further the better). Does the reflection
diverge asymmetrically? Does the asymmetry rotate as you rotate the
dichroic about an axis normal to its surface?

I also agree that you can buy your way out of the problem with a thicker
dichroic specified to have good flatness. This is important for both TIRF
and SIM.
On Nov 1, 2015 23:32, "Philip Nicovich" <[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.
> *****
>
> All,
>
> I'm trying to set up a dual-camera TIRF system using two cameras and a
> dichroic splitter before the pair of matched tube lenses.  The reflected
> arm has some serious astigmatism that doesn't change with swapping cameras
> or tube lenses or playing with the alignment.  The transmitted arm is
> fine.  Swapping dichroics has a little bit of an effect, but not as much as
> I would think.  I certainly haven't found one that actually works well in
> my stash.
>
> Any tricks to confirming that the dichroic splitter is causing the
> problem?  Or what I should be looking for in a proper filter to ensure this
> doesn't happen again?
>
> Thanks,
> Rusty
>
>
>
> --
>
> *Philip R Nicovich*
>
> *Research Fellow,  **ARC Centre of Excellence in Advanced Molecular
> Imaging*
>
>
>
> THE UNIVERSITY OF NEW SOUTH WALES
>
> UNSW  SYDNEY  NSW  2052  AUSTRALIA
>
> T: [phone]
>
> E: [hidden email] <[hidden email]>
>
>
> CRICOS Provider No. 00098G
>