Has anyone used Dodt Gradient Contrast?
I was reading up on the Zeiss Axioimager and they mentioned 'Dodt Gradient Contrast' as part of it. I've never heard of it so I did more looking around and it seems like quite a nice illumination technique. I did a quick rough and ready version of it that's far from the actual thing and no doubt gave vastly inferior results, but it does hint at it's promise so I was wondering if anyone has ever seen/used it. It's a sophisticated variant on oblique lighting.
Here's a rundown of the basics.
http://photos.labwrench.com/equipmentMa ... 5-4769.pdf
Dodt Gradient Contrast?
Moderators: rjlittlefield, ChrisR, Chris S., Pau
This is just a fancy name for classic oblique light. Just decenter your condenser aperture and insert a grad filter into condenser tray.
It's been rediscovered many times in many forms, my guess is that it's easier to sell that way.
One simple, yet effective is Litonotus UFG filter, do exactly the same thing.
It's been rediscovered many times in many forms, my guess is that it's easier to sell that way.
One simple, yet effective is Litonotus UFG filter, do exactly the same thing.
Not exactly: Dodt (what this mean?) places the sector stop at the illumination train and a diffuser after it. It isn't clear if it is placed at a conjugated plane of the condenser diaphragm where it would be equivalent to an oblique stop at the condenser.JohnyM wrote:This is just a fancy name for classic oblique light. Just decenter your condenser aperture and insert a grad fliter into condenser tray.
It seems worth to try with DIY approaches.
Pau
Hi Pau, this is little bit different path ...Pau wrote:...Not exactly: Dodt (what this mean?) places the sector stop at the illumination train and a diffuser after it. It isn't clear if it is placed at a conjugated plane of the condenser diaphragm where it would be equivalent to an oblique stop at the condenser...
Saul
μ-stuff
μ-stuff
Saul, yes I saw the Thornlabs scheme, it seems about the same than the Zeiss, the only clear difference is the mirror (irrelevant) and that the collimating lens is not pictured because they include it in the illuminator sold separately
The name comes from Hans-Ulrich Dodt (It's better to search before posting )
The name comes from Hans-Ulrich Dodt (It's better to search before posting )
Pau
Hmmm...correct me if I'm wrong - in the Thornlabs scheme annulus is double diffused immediately after the light source. Zeiss - between lenses (collimator, illuminator, condenser ? )Pau wrote:Saul, yes I saw the Thornlabs scheme, it seems about the same than the Zeiss, the only clear difference is the mirror (irrelevant) and that the collimating lens is not pictured because they include it in the illuminator sold separately
The name comes from Hans-Ulrich Dodt (It's better to search before posting )
If it is really after collimator - so in this case I could use it in the base filter on my Labophot base ?
Saul
μ-stuff
μ-stuff
Saul, yes, you're right, Zeiss uses lenses and this could allow for more room to place the stop and diffuser, maybe even to use a single sector stop for all NAs (?) while the Thorlabs version just places the system inside the collimated beam and needs different stops for each magnification, this could be easier to replicate.
Of course I ignore if it can be easily DIY adapted to your microscope but I think it could be as you say between the lamp house collimator and the microscope base (some microscopes like my Zeiss has all the collimating optics built in the lamp house while others have all or some of the lenses inside the base... )
This could be the Dodt's original scheme (the same at Zeiss):
http://www.sciencemag.org/site/feature/ ... 2873.xhtml
Here it is explained in more detail: https://www.google.ca/url?sa=t&rct=j&q= ... eX_l5LhTpU
There are commercially available systems. A key part seems to be able to displace the position of the after stop diffuser to regulate contrast
http://www.scientifica.uk.com/learning- ... t-contrast
http://www.luigs-neumann.com/product/dg ... t-contrast
Edit: Science link fixed
Of course I ignore if it can be easily DIY adapted to your microscope but I think it could be as you say between the lamp house collimator and the microscope base (some microscopes like my Zeiss has all the collimating optics built in the lamp house while others have all or some of the lenses inside the base... )
This could be the Dodt's original scheme (the same at Zeiss):
http://www.sciencemag.org/site/feature/ ... 2873.xhtml
Here it is explained in more detail: https://www.google.ca/url?sa=t&rct=j&q= ... eX_l5LhTpU
There are commercially available systems. A key part seems to be able to displace the position of the after stop diffuser to regulate contrast
http://www.scientifica.uk.com/learning- ... t-contrast
http://www.luigs-neumann.com/product/dg ... t-contrast
Edit: Science link fixed
Last edited by Pau on Mon May 14, 2018 12:57 pm, edited 1 time in total.
Pau
I've seen it first hand. Just check your rear focal plane. It IS just oblique light with more theory behind it than DIC microscopy.Pau wrote:Not exactly: Dodt (what this mean?) places the sector stop at the illumination train and a diffuser after it. It isn't clear if it is placed at a conjugated plane of the condenser diaphragm where it would be equivalent to an oblique stop at the condenser.JohnyM wrote:This is just a fancy name for classic oblique light. Just decenter your condenser aperture and insert a grad fliter into condenser tray.
It seems worth to try with DIY approaches.
It's just not as directional and contrasty as oblique thanks to diffuser. Technique is VERY old and was described in books like Pluta "Advanced light microscopy"... just like Zeiss own "Plas DIC"... (funny thing is that they actually quoted it in paper and still get the patent).
There is lots of "forgotten knowledge" that manufacturers suddenly rediscover and sell.