http://confocal-microscopy-list.275.s1.nabble.com/Astigmatism-aberration-as-a-function-of-distance-tp7582827p7582849.html
You are right that a reflective collimator might be the best option. We
another project. But the problem with mine is that, we will be using a
connectorized (at least not now). We flat cleave the fiber, and put it on a
for APC or PC. We used to try to use it but we were never be able to
precisely align the fiber tip w.r.t. the focal point. We also tried a 90
not get it proper aligned. Thorlabs said they are working on some documents
8 St. Mary St., Boston, MA, 02215
> *****
> 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.
> *****
>
> From your test results, the only components left would be the beam splitter
> or the mirrors. That seems unlikely, but its worth removing each one in
> sequence just to be sure you don't have a defective or damaged component
> somewhere.
>
> Regarding sted, an achromat is better than a singlet, but probably not
> adequate given the large bandwidth you want to use. I recommend getting a
> good microscope objective or even a reflective collimator. Zemax gives a
> 0.3 diopter focal shift over that bandwidth for instance.
>
> Mike
>
>
> On Wed, Nov 5, 2014 at 3:34 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 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
> > > > > > -----------------------------------------------------
> > > > > >
> > > > >
> > > >
> > >
> >
>