Diaphot TMD with NA 1.25 Phase Contrast Condenser

Diaphot microscopes are typically used with long working distance (LWD) condensers, but the question came up about compatability with high NA condensers, such as the 1.25 Phase Contrast. This comparison shows different settings of the condenser turret with a variety of objectives. In each case, the view through the Bertrand lens is shown to complete the comparison. Some testing was done with the built-in lens removed, as well.

The specimen is a diatom test slide arranged by Carolina Biological.

A couple of basic observations: the condenser is upside down compared to using in on an upright 'scope, so the labels on the turret positions are not easily visible. Secondly, LWD condensers can be used with open "well slides" effectively, but with the high NA condenser only 1-2 mm away from the slide, an open slide evaporates ... directly on the condenser lens above it, causing water droplets to form on the lens, which is certainly not ideal!

My basic conclusion is that this condenser will generally work on a Diaphot, with a reduced field for very low magnificaions (which you would likely want a LWD condenser for, anyway.)

All photos were taken with a 100 Watt lamphouse installed on a Diaphot TMD with a Nikon D3300 APS-C camera (6000 x 4000 pixels) on the front port. Crops (100%) are therefore about 1 MP out of the 24 MP image.

Diaphot TMD with Phase Contrast 1.25 condenser installed, with lens Diaphot TMD with Phase Contrast 1.25 condenser installed, without lens

2x Plan Apo 0.08

Brightfield : condenser lens installed

2x brightfield with lens in place view through Bertrand lens 2x brightfield with lens installed - full field 2x brightfield with lens installed - 100% crop

Brightfield : condenser lens removed

2x brightfield without lens in place view through Bertrand lens 2x brightfield without lens installed - full field

You can see the effect of the standard condenser field lens is to drastically increase the field with a 2x objective. However, even with the lens installed, this condenser is not ideal for 2x.

Darkfield

2x darkfield with lens installed - full field 2x darkfield with lens installed - 100% crop

Ph2 offset aperture

Unfortunately, I didn't take a picture through the Bertrand lens for the rest of the 2x tests. This one is with the Ph2 aperture offset from center.

2x Ph2 annulus offset from center with lens installed - full field 2x Ph2 annulus offset from center with lens installed - 100% crop

Ph3

2x Ph3 annulus with lens installed - full field 2x Ph3 annulus with lens installed - 100% crop

Ph4 "darkfield"

2x Ph4 annulus beyond NA 0.08 with lens installed - full field 2x Ph4 annulus beyond NA 0.08 with lens installed - 100% crop

4x Plan 0.13 PhL DL

Brightfield

4x brightfield with lens in place view through Bertrand lens 4x brightfield with lens installed - full field 4x brightfield with lens installed - 100% crop

Next, we close down the aperture stop, reducing the NA.

4x brightfield with lens in place view through Bertrand lens 4x brightfield, reduced NA, with lens installed - full field 4x brightfield, reduced NA, with lens installed - 100% crop

Ph1 offset aperture

4x Ph1 offset aperture with lens in place view through Bertrand lens 4x Ph1 annulus offset from center with lens installed - full field 4x Ph1 annulus offset from center with lens installed - 100% crop

Ph1 circular oblique

4x Ph1 offset aperture with lens in place view through Bertrand lens 4x Ph1 with lens installed - full field 4x Ph1 with lens installed - 100% crop

Ph2 "darkfield"

4x Ph2 darkfield with lens in place view through Bertrand lens 4x Ph2 darkfield with lens installed - full field 4x Ph2 darkfield with lens installed - 100% crop

Ph3 "darkfield"

4x Ph3 darkfield with lens in place view through Bertrand lens 4x Ph3 darkfield with lens installed - full field 4x Ph3 darkfield with lens installed - 100% crop

Ph4 "darkfield"

4x Ph4 darkfield with lens in place view through Bertrand lens 4x Ph4 darkfield with lens installed - full field 4x Ph4 darkfield with lens installed - 100% crop

Darkfield

4x darkfield with lens in place view through Bertrand lens 4x darkfield with lens installed - full field 4x darkfield with lens installed - 100% crop

10x Plan 0.30 Ph1 DL

Brightfield

10x brightfield with lens in place view through Bertrand lens 10x brightfield with lens installed - full field 10x brightfield with lens installed - 100% crop

Ph1

10x Ph1 with lens in place view through Bertrand lens 10x Ph1 with lens installed - full field 10x Ph1 with lens installed - 100% crop

Ph2 offset aperture

10x Ph2 with lens in place view through Bertrand lens 10x Ph2 with lens installed - full field 10x Ph2 with lens installed - 100% crop

Ph3

10x Ph3 with lens in place view through Bertrand lens 10x Ph3 with lens installed - full field 10x Ph3 with lens installed - 100% crop

Darkfield

10x darkfield with lens in place view through Bertrand lens 10x darkfield with lens installed - full field 10x darkfield with lens installed - 100% crop

20x 0.40 Ph2 DL (0-2 correction collar)

Brightfield

This image is taken with the condenser aperture just at the edge of the objective. Opening it further decreases contrast with no improvement in the resolution. Here (2.0 MB .GIF) is a demonstration of the trade-off between resolution and contrast as the condenser aperture is opened.

20x brightfield with lens in place view through Bertrand lens 20x brightfield with lens installed - full field 20x brightfield with lens installed - 100% crop

Ph1

20x Ph1 with lens in place view through Bertrand lens 20x Ph1 with lens installed - full field 20x Ph1 with lens installed - 100% crop

Ph2

20x Ph2 with lens in place view through Bertrand lens 20x Ph2 with lens installed - full field 20x Ph2 with lens installed - 100% crop

Ph3

20x Ph3 with lens in place view through Bertrand lens 20x Ph1 with lens installed - full field 20x Ph1 with lens installed - 100% crop

Darkfield

20x darkfield with lens in place view through Bertrand lens 20x darkfield with lens installed - full field 20x darkfield with lens installed - 100% crop

40x 0.55 LWD Ph3 DL (0-2 correction collar)

Brightfield

40x brightfield with lens in place view through Bertrand lens 40x brightfield with lens installed - full field 40x brightfield with lens installed - 100% crop

Ph1

40x Ph1 with lens in place view through Bertrand lens 40x Ph1 with lens installed - full field 40x Ph1 with lens installed - 100% crop

Ph2

40x Ph2 with lens in place view through Bertrand lens 40x Ph2 with lens installed - full field 40x Ph2 with lens installed - 100% crop

Ph3

40x Ph3 with lens in place view through Bertrand lens 40x Ph3 with lens installed - full field 40x Ph3 with lens installed - 100% crop

Darkfield

40x darkfield with lens in place view through Bertrand lens 40x darkfield with lens installed - full field 40x darkfield with lens installed - 100% crop

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