Optical artefact removal

[Jacqueline Ross]

Dear All,

 

I have had an enquiry from someone from another Department who has an
artefact affecting their imaging which looks like a diffraction effect
(e.g. Newton rings) when doing transmitted light microscopy.

 

I had a look at their microscope and camera system and even when Koehler
illumination is set up properly, you still get this effect. The
microscope is a rather old Nikon inverted microscope with a Coolpix
attached. The objectives, (phase contrast), are not infinity corrected
and I'm assuming that there is also a problem with the tube length for
the camera. The rings are there irrespective whether specimens are on
glass or in plastic dishes. I don't think much can be done optically
(correct me if I'm wrong) but I wondered if some image processing could
help.

 

My ImageJ question is this:

 

Is it possible to use some kind of image processing (e.g. image
subtraction) to remove this artifact? I have tried a few things out
(e.g. Image calculator, rolling ball) without much success so far.

 

I have posted 2 images at the following address:
http://www.health.auckland.ac.nz/biru/exptal_images/index.html There are
also links to larger images although the original images are even larger
than these.

 

Please note that I do know that these images are appalling! I asked one
of the students to send me one image with tissue (glass slide) and one
without at the same focal plane and this is what I got! I don't think
they set up the microscope very well. However, you can see the rings
clearly on both images so I hope they will inspire someone to suggest a
solution.

 

I would be very pleased to hear of any potential solutions.

 

Cheers,

 

Jacqui.

 

Jacqueline Ross
Biomedical Imaging Research Unit
School of Medical Sciences
Faculty of Medical & Health Sciences
The University of Auckland
Private Bag 92019
Auckland, NEW ZEALAND

Tel: [phone] Ext 87438
Fax: [phone]

http://www.health.auckland.ac.nz/biru/
<http://www.health.auckland.ac.nz/biru/>  

 

[Joel Sheffield]

Jacqui,

This is, unfortunately, an optical artifact of the coolpix cameras.  
We have seen this primarily with the Coolpix 995, but I understand
that it occurs in others as well.  Our solution is to take a
background image and subtract it from the image of the sample.  
However, this is a particularly tricky thing to do with color images.

Since we see this problem most often with DIC images, we just convert
to greyscale and work with that.  If color is important, you might
consider separating the images into R,G,B images, processing each of
them, and then reassembling with RGB merge, or take a look at the
Color Balance program by Gabriel Landini.
(http://www.dentistry.bham.ac.uk/landinig/software/software.html)
I haven't used it, but the design does make sense.

The best way to eliminate the artifact, I'm afraid, is to get a
different camera.

Joel
 

Date sent:       Tue, 18 Jul 2006 18:40:55 +1200
Send reply to:   ImageJ Interest Group <[hidden email]>
From:           Jacqui Ross <[hidden email]>
Subject:         Optical artefact removal
To:             [hidden email]

> Dear All,
>
>
>
> I have had an enquiry from someone from another Department who has an
> artefact affecting their imaging which looks like a diffraction effect
> (e.g. Newton rings) when doing transmitted light microscopy.
>
>
>
> I had a look at their microscope and camera system and even when
> Koehler illumination is set up properly, you still get this effect.
> The microscope is a rather old Nikon inverted microscope with a
> Coolpix attached. The objectives, (phase contrast), are not infinity
> corrected and I'm assuming that there is also a problem with the tube
> length for the camera. The rings are there irrespective whether
> specimens are on glass or in plastic dishes. I don't think much can be
> done optically (correct me if I'm wrong) but I wondered if some image
> processing could help.
>
>
>
> My ImageJ question is this:
>
>
>
> Is it possible to use some kind of image processing (e.g. image
> subtraction) to remove this artifact? I have tried a few things out
> (e.g. Image calculator, rolling ball) without much success so far.
>
>
>
> I have posted 2 images at the following address:
> http://www.health.auckland.ac.nz/biru/exptal_images/index.html There
> are also links to larger images although the original images are even
> larger than these.
>
>
>
> Please note that I do know that these images are appalling! I asked
> one of the students to send me one image with tissue (glass slide) and
> one without at the same focal plane and this is what I got! I don't
> think they set up the microscope very well. However, you can see the
> rings clearly on both images so I hope they will inspire someone to
> suggest a solution.
>
>
>
> I would be very pleased to hear of any potential solutions.
>
>
>
> Cheers,
>
>
>
> Jacqui.
>
>
>
> Jacqueline Ross
> Biomedical Imaging Research Unit
> School of Medical Sciences
> Faculty of Medical & Health Sciences
> The University of Auckland
> Private Bag 92019
> Auckland, NEW ZEALAND
>
> Tel: [phone] Ext 87438
> Fax: [phone]
>
> http://www.health.auckland.ac.nz/biru/
> <http://www.health.auckland.ac.nz/biru/>  
>
>

Joel B. Sheffield, Ph.D
Department of Biology
Temple University
Philadelphia, PA 19122
Voice: 215 204 8839
e-mail: [hidden email]

[Monique Vasseur]

Hi

Hi Jacqueline,

Looking at your image, I think you have sort of a light leek somewhere in your optical .  Do you have 2 light sources on your microscope? Or one port that is not light proof?  I had that problem with a fluorescence Nikon upright microscope when we where acquiring images in transmitted light and that the mercury lamp was on (at that time we where missing an empty filter cube in the filter turret) but we could avoid the diffraction effect by closing the manual fluorescence shutter on the microscope.

But for your actual images, I guess you could easily do a shading correction by:
 
1- getting a background image (a spot on your slide but out of the specimen area) with the same parameters of exposure time and binning than your specimen image
2- than you divide your specimen image by the background image to get your shading corrected image.
 
Monique Vasseur
Microscopie et imagerie
Département de biochimie
Université de Montréal
tél. [phone] poste 5148
-----Message d'origine-----
De : ImageJ Interest Group [mailto:[hidden email]] De la part de Jacqui Ross
Envoyé : 18 juillet 2006 02:41
À : [hidden email]
Objet : Optical artefact removal

Dear All,

 

I have had an enquiry from someone from another Department who has an
artefact affecting their imaging which looks like a diffraction effect
(e.g. Newton rings) when doing transmitted light microscopy.

 

I had a look at their microscope and camera system and even when Koehler
illumination is set up properly, you still get this effect. The
microscope is a rather old Nikon inverted microscope with a Coolpix
attached. The objectives, (phase contrast), are not infinity corrected
and I'm assuming that there is also a problem with the tube length for
the camera. The rings are there irrespective whether specimens are on
glass or in plastic dishes. I don't think much can be done optically
(correct me if I'm wrong) but I wondered if some image processing could
help.

 

My ImageJ question is this:

 

Is it possible to use some kind of image processing (e.g. image
subtraction) to remove this artifact? I have tried a few things out
(e.g. Image calculator, rolling ball) without much success so far.

 

I have posted 2 images at the following address:
http://www.health.auckland.ac.nz/biru/exptal_images/index.html There are
also links to larger images although the original images are even larger
than these.

 

Please note that I do know that these images are appalling! I asked one
of the students to send me one image with tissue (glass slide) and one
without at the same focal plane and this is what I got! I don't think
they set up the microscope very well. However, you can see the rings
clearly on both images so I hope they will inspire someone to suggest a
solution.

 

I would be very pleased to hear of any potential solutions.

 

Cheers,

 

Jacqui.

 

Jacqueline Ross
Biomedical Imaging Research Unit
School of Medical Sciences
Faculty of Medical & Health Sciences
The University of Auckland
Private Bag 92019
Auckland, NEW ZEALAND

Tel: [phone] Ext 87438
Fax: [phone]

http://www.health.auckland.ac.nz/biru/
<http://www.health.auckland.ac.nz/biru/>  

 

[Leon Espinosa]

Hi
It is right that this is a specific coolpix artefact, it is present  
for models after CP-995 (4500, 5000) It is due to the photosites size  
(usually for digital cameras the  improvements for general  
photography are bad things for microscope microphotography). Well,  
you can diminish this artifact in manual mode trying different  
aperture settings (f/2.8, f/5,6, etc.) and of course adjust the right  
exposure with the speed. After this you will need also to play with  
the microscope aperture diaphragm (in the condenser) in order to  
optimize results.
I hope it helps for your future picture, for old pictures maybe somme  
band pass filter correction ?

Leon





Le 18 juil. 06 à 15:22, Vasseur Monique a écrit :

> Hi
>
> Hi Jacqueline,
>
> Looking at your image, I think you have sort of a light leek  
> somewhere in your optical .  Do you have 2 light sources on your  
> microscope? Or one port that is not light proof?  I had that  
> problem with a fluorescence Nikon upright microscope when we where  
> acquiring images in transmitted light and that the mercury lamp was  
> on (at that time we where missing an empty filter cube in the  
> filter turret) but we could avoid the diffraction effect by closing  
> the manual fluorescence shutter on the microscope.
>
> But for your actual images, I guess you could easily do a shading  
> correction by:
>
> 1- getting a background image (a spot on your slide but out of the  
> specimen area) with the same parameters of exposure time and  
> binning than your specimen image
> 2- than you divide your specimen image by the background image to  
> get your shading corrected image.
>
> Monique Vasseur
> Microscopie et imagerie
> Département de biochimie
> Université de Montréal
> tél. [phone] poste 5148
> -----Message d'origine-----
> De : ImageJ Interest Group [mailto:[hidden email]] De la part  
> de Jacqui Ross
> Envoyé : 18 juillet 2006 02:41
> À : [hidden email]
> Objet : Optical artefact removal
>
> Dear All,
>
>
>
> I have had an enquiry from someone from another Department who has an
> artefact affecting their imaging which looks like a diffraction effect
> (e.g. Newton rings) when doing transmitted light microscopy.
>
>
>
> I had a look at their microscope and camera system and even when  
> Koehler
> illumination is set up properly, you still get this effect. The
> microscope is a rather old Nikon inverted microscope with a Coolpix
> attached. The objectives, (phase contrast), are not infinity corrected
> and I'm assuming that there is also a problem with the tube length for
> the camera. The rings are there irrespective whether specimens are on
> glass or in plastic dishes. I don't think much can be done optically
> (correct me if I'm wrong) but I wondered if some image processing  
> could
> help.
>
>
>
> My ImageJ question is this:
>
>
>
> Is it possible to use some kind of image processing (e.g. image
> subtraction) to remove this artifact? I have tried a few things out
> (e.g. Image calculator, rolling ball) without much success so far.
>
>
>
> I have posted 2 images at the following address:
> http://www.health.auckland.ac.nz/biru/exptal_images/index.html 
> There are
> also links to larger images although the original images are even  
> larger
> than these.
>
>
>
> Please note that I do know that these images are appalling! I asked  
> one
> of the students to send me one image with tissue (glass slide) and one
> without at the same focal plane and this is what I got! I don't think
> they set up the microscope very well. However, you can see the rings
> clearly on both images so I hope they will inspire someone to  
> suggest a
> solution.
>
>
>
> I would be very pleased to hear of any potential solutions.
>
>
>
> Cheers,
>
>
>
> Jacqui.
>
>
>
> Jacqueline Ross
> Biomedical Imaging Research Unit
> School of Medical Sciences
> Faculty of Medical & Health Sciences
> The University of Auckland
> Private Bag 92019
> Auckland, NEW ZEALAND
>
> Tel: [phone] Ext 87438
> Fax: [phone]
>
> http://www.health.auckland.ac.nz/biru/
> <http://www.health.auckland.ac.nz/biru/>
>
>
>

Leon Espinosa
[hidden email]

Laboratoire des Rickettsies du Pr. RAOULT
UMR CNRS 6020
Fac. de Medecine de la Timone
27 Bd Jean Moulin
13005 Marseille

tel  [phone]
fax [phone]

portable  06 79 25 97 40

[Gabriel Landini]

On Tuesday 18 July 2006 14:15, Joel Sheffield wrote:
> them, and then reassembling with RGB merge, or take a look at the
> Color Balance program by Gabriel Landini.
> (http://www.dentistry.bham.ac.uk/landinig/software/software.html)

The plugin Joel mentioned (I guess that you mean Colour_Correct) unfortunately
does not correct this kind of artifact.

I am not sure if the following (ratio) works in phase contrast (it works on
bright field, though):

Capture a shot with the light path off (all black), Call it Darkfield (this
will compensate 'hot' pixels).
Capture a shot of the light path on (no specimen, all background) call it
Brightfield (this will compensate uneven background).

Put the specimen in and capture; call it Specimen

Using the image calculator do:
Subtract Brightfield-Darkfield, call it Divisor
Subtract Specimen-Darkfield, call it Numerator

Using Calculator_Plus plugin (in IJ site)  do:

Divide Numerator by Divisor and multiply by 255.

The result should have a flat background and white will appear white as far as
you do not change at all the settings of the camera between shots (time,
exposure, autobalance etc) or the microscope setting (light, condenser,
magnification).

One can improve the S/N ratio by taking average shots instead of single ones
(the improving factor is, I think, the square root of the number of shots).

The Divisor image can be used for subsequent shots if the light source is
stable and you do not change magnification. The Darkfield image can be used
as well if you do not change camera settings.
Some cameras have auto exposure which makes this kind of procedure impossible
to apply.

Cheers,

Gabriel

[Joachim Wesner]

Hi all,

>It is right that this is a specific coolpix artefact, it is present
>for models after CP-995 (4500, 5000) It is due to the photosites size
>(usually for digital cameras the  improvements for general
>photography are bad things for microscope microphotography).

Hmm, are you referring to some kind of moire effect? However, I could not
understand
how this should show up on a presumed homogeneous (resp. non-periodic)
background!?

As I understand they are using non-infinity objectives in some kind of
infinity position,
I would assume (the order of this effect depends greatly on the focal
length of the objctive used)
that they need to defocus so much that a normally unnoticed (becaused
totally out of focus) internal
reflex becomes near focus and noticeable, maybe this is even a bad
coincidence with the reflection
from the "cover glass" (or whatever, I don´t know the layout of coolpix
cameras) in front of the chip,
so it might disappear with other cameras, because they have that glass in
another position!

Joachim





______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please visit http://www.messagelabs.com/email 
______________________________________________________________________

[Joel Sheffield]

It is not at all clear where the artifact comes from.  We have had
the same effect with infinity corrected lenses.  The size of the
rings is independent of the objective magnification. It is unaffected
by microscope focus.

I like Joachim's suggestions about the structure of the camera.  It
could easily be an internal reflection problem of some sort.  It does
not appear to be a function of the camera focal length --at least
within the zoom ranges that are used for microphotography.

If the sample is complex, and fills the field, i.e. a tissue section,
the effect of the artifact is minimal.  However, if there is an
extensive area of background, or if the illumination is dim, the
artifact becomes prominent.

Interestingly, it is sufficiently consistent that it can be removed
by background subtraction procedures that use a "no sample" image, as
long as intensity is kept constant.


Joel

> Hi all,
>
> >It is right that this is a specific coolpix artefact, it is present
> >for models after CP-995 (4500, 5000) It is due to the photosites size
> >(usually for digital cameras the  improvements for general
> >photography are bad things for microscope microphotography).
>
> Hmm, are you referring to some kind of moire effect? However, I could
> not understand how this should show up on a presumed homogeneous
> (resp. non-periodic) background!?
>
> As I understand they are using non-infinity objectives in some kind of
> infinity position, I would assume (the order of this effect depends
> greatly on the focal length of the objctive used) that they need to
> defocus so much that a normally unnoticed (becaused totally out of
> focus) internal reflex becomes near focus and noticeable, maybe this
> is even a bad coincidence with the reflection from the "cover glass"
> (or whatever, I don´t know the layout of coolpix cameras) in front of
> the chip, so it might disappear with other cameras, because they have
> that glass in another position!
>
> Joachim
>
>
>
>
>
> ______________________________________________________________________
> This email has been scanned by the MessageLabs Email Security System.
> For more information please visit http://www.messagelabs.com/email
> ______________________________________________________________________

Joel B. Sheffield, Ph.D.
Biology Department, Temple University
1900 North 12th Street
Philadelphia, PA 19122
[hidden email]  
[phone], fax [phone]
http://astro.temple.edu/~jbs

[John J. Bozzola]

We have this "affliction" all the time since we are using a digital
camera on a transmission electron microscope and the phosphor (not
being smoothly applied) has a bright quadrant. NIH does an excellent
job of subracting the background. Basically, you record an image
under the same lighting conditions as the specimen (but minus the
specimen). This gives the background that you want to subtract. Next
record your image under the same lighting conditions (relative
brightness). Open both images, go to Process/Math and subtract the
background from the image. It does a super job. Now, I must admit
that I am not using Image J but I am sure these features are there as
well.

John

>
>I have had an enquiry from someone from another Department who has an
>artefact affecting their imaging which looks like a diffraction effect
>(e.g. Newton rings) when doing transmitted light microscopy.
>
>
>
>I had a look at their microscope and camera system and even when Koehler
>illumination is set up properly, you still get this effect. The
>microscope is a rather old Nikon inverted microscope with a Coolpix
>attached. The objectives, (phase contrast), are not infinity corrected
>and I'm assuming that there is also a problem with the tube length for
>the camera. The rings are there irrespective whether specimens are on
>glass or in plastic dishes. I don't think much can be done optically
>(correct me if I'm wrong) but I wondered if some image processing could
>help.
>
>
>
>My ImageJ question is this:
>
>
>
>Is it possible to use some kind of image processing (e.g. image
>subtraction) to remove this artifact? I have tried a few things out
>(e.g. Image calculator, rolling ball) without much success so far.
>
>
>
>I have posted 2 images at the following address:
>http://www.health.auckland.ac.nz/biru/exptal_images/index.html There are
>also links to larger images although the original images are even larger
>than these.
>
>
>
>Please note that I do know that these images are appalling! I asked one
>of the students to send me one image with tissue (glass slide) and one
>without at the same focal plane and this is what I got! I don't think
>they set up the microscope very well. However, you can see the rings
>clearly on both images so I hope they will inspire someone to suggest a
>solution.
>
>
>
>I would be very pleased to hear of any potential solutions.
>
>
>
>Cheers,
>
>
>
>Jacqui.
>
>
>
>Jacqueline Ross
>Biomedical Imaging Research Unit
>School of Medical Sciences
>Faculty of Medical & Health Sciences
>The University of Auckland
>Private Bag 92019
>Auckland, NEW ZEALAND
>
>Tel: [phone] Ext 87438
>Fax: [phone]
>
>http://www.health.auckland.ac.nz/biru/
><http://www.health.auckland.ac.nz/biru/>
>
>

--
##############################################################
John J. Bozzola, Ph.D., Director
I.M.A.G.E. (Integrated Microscopy & Graphics Expertise)
750 Communications Drive - MC 4402
Southern Illinois University
Carbondale, IL 62901  U.S.A.
Phone: [phone]
Email: [hidden email]
Web: http://www.siu.edu/~image/
##############################################################

[Jonathan Hilmer]

Although not as effective as a lightfield/darkfield background
subtract, shouldn't it be possible to write a plugin to correct for
this automatically?  I have no idea how to implement the details, but
here's my general scheme:

Interpret the image as a radial plot, possibly with averaging.  This
should give an image with strong vertical or horizontal bands.  Use a
FFT-based system to isolate the background component, then undo the
radial step to generate a synthetic lightfield image.

I can't say how easy this would be, but it might be a solution for
people who don't have the option for a control-image background
subtraction.

[Stanislav Vitha]

Dear Jacqui,
I have used the Coolpix 995 and Coolpix4500 on different compound
microscopes and was able to suppress the ring artefact to reasonable
levels. The severity of the artefact may vary from camera to camera,
but it is apparently caused by the spin-cast manufacturing process of
Coolpix lenses:
http://www.couger.com/microscope/shootout/shootout.html

I found that the ring artefact is less obvious if I zoom out with the
Coolpix as much as possible. People sometimes make the mistake of
zooming in all the way to maximum to gain (useless) magnification -
the rings are then pretty visible. So zoom in only enough to remove
the vignetting - it depends on your adapter (eyepiece) how much zoom
is necessary - the closer is the eyepiece to the front of the coolpix
lens, the better - in my adapter the lenses were only about 1 mm
apart, so not much zoom was needed. Some of the genuine Nikon
adapters had the front element recessed too much and a lot of zoom
was needed to remove vignetting.

Of course, if you need reproducible magnification, it would be nice
to set the zoom to the same numerical value each time the camera is
used. There is some free software that can be used for this purpose
and also can be used as a remote shutter. I can provide more detail off-list.

On my Olympus BH2 microscope the artefact was also less severe with
lower magnification objectives than with the oil 100x/1.3.

Regards,
Stan

At 01:40 AM 7/18/2006, you wrote:

>Dear All,
>
>
>
>I have had an enquiry from someone from another Department who has an
>artefact affecting their imaging which looks like a diffraction effect
>(e.g. Newton rings) when doing transmitted light microscopy.
>
>
>
>I had a look at their microscope and camera system and even when Koehler
>illumination is set up properly, you still get this effect. The
>microscope is a rather old Nikon inverted microscope with a Coolpix
>attached. The objectives, (phase contrast), are not infinity corrected
>and I'm assuming that there is also a problem with the tube length for
>the camera. The rings are there irrespective whether specimens are on
>glass or in plastic dishes. I don't think much can be done optically
>(correct me if I'm wrong) but I wondered if some image processing could
>help.
>
>
>
>My ImageJ question is this:
>
>
>
>Is it possible to use some kind of image processing (e.g. image
>subtraction) to remove this artifact? I have tried a few things out
>(e.g. Image calculator, rolling ball) without much success so far.
>
>
>
>I have posted 2 images at the following address:
>http://www.health.auckland.ac.nz/biru/exptal_images/index.html There are
>also links to larger images although the original images are even larger
>than these.
>
>
>
>Please note that I do know that these images are appalling! I asked one
>of the students to send me one image with tissue (glass slide) and one
>without at the same focal plane and this is what I got! I don't think
>they set up the microscope very well. However, you can see the rings
>clearly on both images so I hope they will inspire someone to suggest a
>solution.
>
>
>
>I would be very pleased to hear of any potential solutions.
>
>
>
>Cheers,
>
>
>
>Jacqui.
>
>
>
>Jacqueline Ross
>Biomedical Imaging Research Unit
>School of Medical Sciences
>Faculty of Medical & Health Sciences
>The University of Auckland
>Private Bag 92019
>Auckland, NEW ZEALAND
>
>Tel: [phone] Ext 87438
>Fax: [phone]
>
>http://www.health.auckland.ac.nz/biru/
><http://www.health.auckland.ac.nz/biru/>
>
>

Dr. Stanislav Vitha      [hidden email]
Microscopy and Imaging Center
Texas A&M University
BSBW 119
College Station, TX 77843-2257

tel: [phone] (main desk)
tel: [phone] (direct link)
fax: [phone]

[Jacqueline Ross]

Dear Stan,

Thanks for your comments and advice on how to reduce the artifact.
Interestingly, one of the people using the camera had been using the
zoom and getting better results so it seems this may be one way around
the problem.

If you can send me the information on the free software offline, that
would be much appreciated. Consistency is important when doing
comparisons and saves continually having to recalibrate.

Cheers,

Jacqui.

Jacqueline Ross
Biomedical Imaging Research Unit
School of Medical Sciences
Faculty of Medical & Health Sciences
The University of Auckland
Private Bag 92019
Auckland, NEW ZEALAND

Tel: [phone] Ext 87438
Fax: [phone]

http://www.health.auckland.ac.nz/biru/ 

-----Original Message-----
From: ImageJ Interest Group [mailto:[hidden email]] On Behalf Of
Stanislav Vitha
Sent: 20 July 2006 04:04
To: [hidden email]
Subject: Re: Optical artefact removal

Dear Jacqui,
I have used the Coolpix 995 and Coolpix4500 on different compound
microscopes and was able to suppress the ring artefact to reasonable
levels. The severity of the artefact may vary from camera to camera,
but it is apparently caused by the spin-cast manufacturing process of
Coolpix lenses:
http://www.couger.com/microscope/shootout/shootout.html

I found that the ring artefact is less obvious if I zoom out with the
Coolpix as much as possible. People sometimes make the mistake of
zooming in all the way to maximum to gain (useless) magnification -
the rings are then pretty visible. So zoom in only enough to remove
the vignetting - it depends on your adapter (eyepiece) how much zoom
is necessary - the closer is the eyepiece to the front of the coolpix
lens, the better - in my adapter the lenses were only about 1 mm
apart, so not much zoom was needed. Some of the genuine Nikon
adapters had the front element recessed too much and a lot of zoom
was needed to remove vignetting.

Of course, if you need reproducible magnification, it would be nice
to set the zoom to the same numerical value each time the camera is
used. There is some free software that can be used for this purpose
and also can be used as a remote shutter. I can provide more detail
off-list.

On my Olympus BH2 microscope the artefact was also less severe with
lower magnification objectives than with the oil 100x/1.3.

Regards,
Stan

At 01:40 AM 7/18/2006, you wrote:

>Dear All,
>
>
>
>I have had an enquiry from someone from another Department who has an
>artefact affecting their imaging which looks like a diffraction effect
>(e.g. Newton rings) when doing transmitted light microscopy.
>
>
>
>I had a look at their microscope and camera system and even when

Koehler

>illumination is set up properly, you still get this effect. The
>microscope is a rather old Nikon inverted microscope with a Coolpix
>attached. The objectives, (phase contrast), are not infinity corrected
>and I'm assuming that there is also a problem with the tube length for
>the camera. The rings are there irrespective whether specimens are on
>glass or in plastic dishes. I don't think much can be done optically
>(correct me if I'm wrong) but I wondered if some image processing could
>help.
>
>
>
>My ImageJ question is this:
>
>
>
>Is it possible to use some kind of image processing (e.g. image
>subtraction) to remove this artifact? I have tried a few things out
>(e.g. Image calculator, rolling ball) without much success so far.
>
>
>
>I have posted 2 images at the following address:
>http://www.health.auckland.ac.nz/biru/exptal_images/index.html There

are
>also links to larger images although the original images are even
larger

>than these.
>
>
>
>Please note that I do know that these images are appalling! I asked one
>of the students to send me one image with tissue (glass slide) and one
>without at the same focal plane and this is what I got! I don't think
>they set up the microscope very well. However, you can see the rings
>clearly on both images so I hope they will inspire someone to suggest a
>solution.
>
>
>
>I would be very pleased to hear of any potential solutions.
>
>
>
>Cheers,
>
>
>
>Jacqui.
>
>
>
>Jacqueline Ross
>Biomedical Imaging Research Unit
>School of Medical Sciences
>Faculty of Medical & Health Sciences
>The University of Auckland
>Private Bag 92019
>Auckland, NEW ZEALAND
>
>Tel: [phone] Ext 87438
>Fax: [phone]
>
>http://www.health.auckland.ac.nz/biru/
><http://www.health.auckland.ac.nz/biru/>
>
>

Dr. Stanislav Vitha      [hidden email]
Microscopy and Imaging Center
Texas A&M University
BSBW 119
College Station, TX 77843-2257

tel: [phone] (main desk)
tel: [phone] (direct link)
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