http://confocal-microscopy-list.275.s1.nabble.com/Astigmatism-aberration-as-a-function-of-distance-tp7582827p7582841.html
or the mirrors. That seems unlikely, but its worth removing each one in
adequate given the large bandwidth you want to use. I recommend getting a
good microscope objective or even a reflective collimator. Zemax gives a
> *****
> 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 everyone,
>
> I have updated the linked page a bit, and included some images I took
> yesterday. FYI, the link is:
>
>
https://www.evernote.com/shard/s275/sh/55130807-98d4-4748-a4a9-64d19650b695/be0756284a13da18fe6d1f7f419cbcfe>
>
> Hi Mike,
>
> I am using a achromat since we will be doing multicolors (in 500~750 nm,
> ultimately we would like to build a STED illumination system using
> fibers.). For the lens orientation, yes I checked that, and there is also
> an arrow mark indicating the direction of collimated wavefront on the lens
> housing. The problem with the aspheric is that, for multiple colors if I am
> not mistaken, I will get significant chromatic aberration provided that my
> objective lens (Olympus UPLSAPO 60X) will have quite good correction on
> chromatic aberration, i.e. it focuses collimated multiple colors on to the
> same focal plane so if I have multiple beams with different divergent
> angles it will focus them at different z positions. So a good achromat
> seems the only option.
>
> For the coupler alignment, I am using a throlabs 3-x stage (
>
https://www.thorlabs.com/thorproduct.cfm?partnumber=MBT616D) with a fiber
> holder. I also tried 6-x stage but it does not give me better results. I am
> using flat cleaved fiber.
>
> I have updated the linked page and added some images of the beam at
> different position in the system. Hope that can clear something out.
>
> Thanks,
> 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
>
[hidden email]
> -----------------------------------------------------
>
> On Wed, Nov 5, 2014 at 1:40 PM, Michael Giacomelli <
[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 Lu,
> >
> > Regarding your collimator, using short focal length achromats is usually
> a
> > bad idea unless you are using a very broadband laser (E.g. short pulse
> > ti:saph or supercontinuum). Instead, aspheric couplers are usually used
> as
> > an achromat will have significant spherical aberration. If you do use an
> > achromat, make sure that do not use it backwards (always minimize
> > glass-wavefront curvature - flatter face into diverging wavefront, curved
> > face into collimated wavefront) and if possible simulate in zemax to be
> > sure before trying it. Just simulating the AC254-30-A, putting the lens
> in
> > backwards results in a massively abberated beam. I would double check
> that
> > first. Alternatively, buying an aspheric may be a better idea.
> Technically
> > the AC254-30-A is ok, but only just, only if perfectly aligned. You have
> > little margin for error.
> >
> > If you haven't already, I recommend aligning the coupler to the grid of
> > your table, and running the beam quite far out and ensuring that it is
> > truly parallel to that grid (and thus perpendicular to lens face).
> Because
> > of the short focal length, you must be very precise here, with an error
> of
> > about a quarter of a millimeter in centration introducing noticeable
> > astigmatism. I recommend a good 3 axis kinematic.
> >
> > Regarding tilt of the fiber face, usually fibers are angle cleaved, and
> > then mounted in a coupler with a matching tilt. Make sure that if you
> used
> > an APC fiber, you have an APC mount, and if you used a flat cleaved
> fiber,
> > you have an un-angled mount.
> >
> > Regarding mirrors, a standard thorlabs mirror used in one of their mounts
> > will have negligible astigmatism when used with a beam of your diameter.
> > It is true that mirrors can and do introduce aberration into beams, but
> > with such a narrow beam diameter, even a relatively poor mirror will not
> > introduce noticeable phase error. These problems are much more common at
> > 2" and above.
> >
> > By the way, do you have access to a beam profiler? Taking an image of
> this
> > focal spot and posting it might give some clues.
> >
> > Mike
> >
> >
> >
> >
> > On Wed, Nov 5, 2014 at 1:11 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 Mike,
> > >
> > > Thanks for promote reply. Like you said for an on axis system
> (especially
> > > simple as mine), astigmatism should not be there, and that why it
> > confused
> > > me a lot. I am currently using a Thorlabs air-spaced achromatic lens
> > > (f=30mm) (
> >
http://www.thorlabs.com/thorproduct.cfm?partnumber=ACA254-030-A)
> > > for the collimation. The fiber I have tried are SMF600 and RBG 400,
> both
> > of
> > > which are single mode at 632 nm. I usually looked at the back
> reflection
> > > (from surfaces of the lens) formed interference pattern (concentric
> > rings)
> > > to align my fiber w.r.t. my fiber facet.
> > >
> > > For your comments on my questions:
> > >
> > > 1) I am using the multimode fiber as the pinhole to achieve confocal.
> > > 2) Looking at the beam spot after the collimation lens, it was not
> > changing
> > > much even at several meters away from the lens. The spot changed
> rapidly
> > > around the focal plane if the beam was reimaged through another lens
> > (e.g.
> > > L2 or L3 in the linked page). I think the NA is large enough for the
> > fiber
> > > I am using.
> > > 3) I was thinking maybe the fiber tip is tilted with respect to the
> > > collimation lens plane? Would that cause problem? OR would that still
> > give
> > > me concentric rings pattern centered at my fiber tip (if the fiber is
> > > tilted w.r.t. the lens plane)?
> > >
> > > Thanks,
> > > 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
> > >
[hidden email]
> > > -----------------------------------------------------
> > >
> > > On Wed, Nov 5, 2014 at 12:37 AM, Michael Giacomelli <
[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 Lu,
> > > >
> > > > In an on axis system like you have drawn there should be no
> astigmatism
> > > if
> > > > the fiber is well centered on the optic. Assuming you've correctly
> > > aligned
> > > > the collimator, I would think it is some other aberration you are
> > seeing.
> > > >
> > > > Regarding your questions in that linked page:
> > > >
> > > > 1) It depends on what you want to collect. 4f (or some other
> imaging
> > > > condition) will give you maximum light collection, which is likely
> what
> > > you
> > > > want if you have selected a multimode fiber. Alternatively, if this
> > is a
> > > > confocal system, it is probably not necessary.
> > > >
> > > > 2) The diagram shows a collimated single mode fiber. That should be
> > > > independent of distance. If you find that your spot is changing
> > rapidly
> > > > with distance, likely something is wrong with the collimation. What
> > are
> > > > you using a collimator? Is it suitable for the NA and
> > > wavelength/bandwidth
> > > > of your source? Is it well aligned? What is the exact model of
> fiber
> > > you
> > > > are using.
> > > >
> > > > 3) Most likely it is a problem with your coupler.
> > > >
> > > > Mike
> > > >
> > > > On Tue, Nov 4, 2014 at 11:36 PM, 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 folks,
> > > > >
> > > > > I am building a fiber based confocal microscopy setup (with sample
> > > stage
> > > > > scanning). But I always got some astigmatism aberration in PSF
> > > > measuremnts.
> > > > > The similar aberration was there even I replaced the objective lens
> > > with
> > > > a
> > > > > regular lens and imaged my illumination beam through that lens
> with a
> > > > > camera. I got elongated beam 'spot' on both sides of the focal
> plane,
> > > and
> > > > > the orientation of the two 'spot' were orthogonal. I think that is
> > > > > astigmatism aberration if I am not mistaken. I draw a schematic in
> > > > Evernote
> > > > > so I can include it here. Here is the link:
> > > > >
> > > > >
> > > >
> > >
> >
>
https://www.evernote.com/shard/s275/sh/55130807-98d4-4748-a4a9-64d19650b695/be0756284a13da18fe6d1f7f419cbcfe> > > > > (copy and paste if the link does not work in email)
> > > > >
> > > > > I tried to adjust both lens in xy to avoid off-axis incident, but
> the
> > > > > aberration would go away. So I got confused where they came from. I
> > > hope
> > > > > someone here could lead me a direction to further look into it.
> > > > >
> > > > > Thanks very much,
> > > > > 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
> > > > > -----------------------------------------------------
> > > > >
> > > >
> > >
> >
>