Investigating DIC Compatibility of 100x Objective Lenses on a Nikon OptiPhot with Differential Interference Contrast Configuration

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We received photos from Mr. M., a user of our camera adapter, showing his Nikon OptiPhot configured for Differential Interference Contrast (DIC). As his DIC-designated objective lens was contaminated, he tested the compatibility of non-DIC-marked objective lenses for DIC observation. Such compatibility data is extremely valuable for users working with legacy equipment.

This is a Nikon OptiPhot microscope configured for DIC.
An intermediate tube is installed between the viewing head and the revolving nosepiece. This intermediate tube houses the analyzer and a Nomarski prism, which is shared across all objective lenses.
The condenser is a turret type, allowing the user to rotate and switch Nomarski prisms according to the objective lens in use.

For comparison:

  • The Zeiss AxioSkop places an individual Nomarski prism above each objective lens, and its condenser has only two prisms—one for low magnification and one for high magnification.

  • The Olympus BX51 shares a similar structure to the OptiPhot, with individual Nomarski prisms in the condenser and a common prism in the head.

Different manufacturers have adopted different DIC implementations. Personally, I find the Nikon and Olympus approaches easier to understand from a design standpoint.

This is the DIC turret condenser.
By rotating the turret, users can switch between Nomarski prisms suited for each magnification.

The following four 100x oil immersion objective lenses were tested for DIC compatibility:

  • Nikon Plan 100 NA 1.25

  • Nikon Plan 100 DIC NA 1.25

  • Nikon Plan Apo 100 NA 1.40

  • Nikon Fluor 100 NA 1.30

All are 100x oil immersion objectives with a mechanical tube length of 160 mm.
I had expected the addition of the intermediate tube to increase the mechanical tube length, so this result was surprising.

Among these, only the Plan 100 DIC is officially DIC-compatible.
So, the key question: can the other three lenses also be used for DIC observation?


Subject: Gills and spores (the round structures at the upper left) of a mushroom from the Russula genus.

Imaging Setup:

  • Microscope camera adapter: Institute of Small World camera adapter for Nikon OptiPhot

  • Relay lens: Nikon PL 2.5

  • Camera body: Nikon D5100

Objective: Nikon Plan 100 NA 1.25
Shows clean DIC contrast across the field of view.


Objective: Nikon Plan 100 DIC NA 1.25
Slightly reduced image contrast due to lens contamination.

Objective: Nikon Plan Apo 100 NA 1.40


Objective: Nikon Fluor 100 NA 1.30


Interestingly, the standard Plan 100 (NA 1.25), not marked as DIC, produced proper DIC images.

The Plan Apo 100 and Fluor 100 also allowed DIC imaging, but both exhibited light flares in the background.

Field of View with Nikon Plan 100
Clean image with proper DIC effect.

Field of View with Nikon Plan Apo 100
Noticeable flaring in the field. Nikon Fluor 100 exhibited similar results.


It was surprising that the most affordable lens, the Plan 100, turned out to be DIC-compatible.
This may be due to its numerical aperture (NA 1.25) being identical to that of the Plan 100 DIC.
It’s possible that the Plan 100 DIC is a specially selected version of the standard Plan 100.
Functionally, they might even be the same lens.

If you’re looking for a Plan 100 DIC, trying a standard Plan 100 could be a practical and cost-effective alternative.
Among these four lenses, the Plan 100 is the easiest to obtain and the most affordable.

Given the limited availability of Nikon objectives, conducting this kind of multi-lens comparison is extremely difficult.
This is likely data that even the manufacturer does not possess.

Many thanks to Mr. M. for sharing this valuable information.



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