Home page of the microscope service parts, repair and spare parts online catalog - Sermik-Oplatek Mikroskopservice Dresden f.n.n.Z

Description of this part for the microscope.

and Standard 16 models. Does it also fit the Junior / WL / Universal and Phomi?

Description of this part for the microscope.

in the terminology of PZO the name "MPI5" has two meanings, which causes some confusion:
- MPI5 is the name of a DIC microscope based on the PZO MB-30 stand, KPI-2 condenser and the DIC head model MPI3
- MPI5 is also the name of the latest DIC head that is part of the PZO UPI set (PL: Urzadzenie Polaryzacyjno-Interferencyjne)

Description of this part for the microscope.

a Zeiss microscope stage on which no model designation was provided. Over the years during which Zeiss produced such stages, numerous variants were created (I have personally seen five, for example Zeiss P/N 47 34 28 - 9901 https://www.microscopeparts.eu/microscope/282). Despite this variety, the construction is largely consistent, and most parts are identical.
It is therefore highly likely that the part shown and offered here is compatible with many variants of such microscope stages.

Such stages are interchangeable and can be installed in many Zeiss microscopes, however they are most commonly used in the following microscopes:
- Zeiss Standard 14
- Zeiss Standard 16
- Zeiss Standard GFL

Also often in:
- Zeiss Standard WL
- Zeiss Standard Universal

Note that there are two such guides in the stage. They are made of a soft, thin piece of brass sheet and are often damaged; the bearing rollers also frequently fall out of them.

In the photo gallery there are detailed photos of this element together with the dimensions.

Description of this part for the microscope.

a Zeiss microscope stage on which no model designation was provided. Over the years during which Zeiss produced such stages, numerous variants were created (I have personally seen five, for example Zeiss P/N 47 34 28 - 9901 https://www.microscopeparts.eu/microscope/282). Despite this variety, the construction is largely consistent, and most parts are identical.
It is therefore highly likely that the part shown and offered here is compatible with many variants of such microscope stages.

Such stages are interchangeable and can be installed in many Zeiss microscopes, however they are most commonly used in the following microscopes:
- Zeiss Standard 14
- Zeiss Standard 16
- Zeiss Standard GFL

Also often in:
- Zeiss Standard WL
- Zeiss Standard Universal

In the photo gallery there are detailed photos of this element together with the dimensions. Additionally, in the last photo an arrow indicates which element is being referred to and where it is located, in order to clearly identify this part.

Description of this part for the microscope.

a Zeiss microscope stage on which no model designation was provided. Over the years during which Zeiss produced such stages, numerous variants were created (I have personally seen five, for example Zeiss P/N 47 34 28 - 9901 https://www.microscopeparts.eu/microscope/282). Despite this variety, the construction is largely consistent, and most parts are identical.
It is therefore highly likely that the part shown and offered here is compatible with many variants of such microscope stages.

Such stages are interchangeable and can be installed in many Zeiss microscopes, however they are most commonly used in the following microscopes:
- Zeiss Standard 14
- Zeiss Standard 16
- Zeiss Standard GFL

Also often in:
- Zeiss Standard WL
- Zeiss Standard Universal

In the photo gallery there are detailed photos of this element together with the dimensions. Additionally, in the last photo an arrow indicates which element is being referred to and where it is located, in order to clearly identify this part.

Description of this part for the microscope.

a Zeiss microscope stage on which no model designation was provided. Over the years during which Zeiss produced such stages, numerous variants were created (I have personally seen five, for example Zeiss P/N 47 34 28 - 9901 https://www.microscopeparts.eu/microscope/282). Despite this variety, the construction is largely consistent, and most parts are identical.
It is therefore highly likely that the part shown and offered here is compatible with many variants of such microscope stages.

Such stages are interchangeable and can be installed in many Zeiss microscopes, however they are most commonly used in the following microscopes:
- Zeiss Standard 14
- Zeiss Standard 16
- Zeiss Standard GFL

Also often in:
- Zeiss Standard WL
- Zeiss Standard Universal

In the photo gallery there are detailed photos of this element together with the dimensions. Additionally, in the last photo an arrow indicates which element is being referred to and where it is located, in order to clearly identify this part.

Description of this part for the microscope.

cover.

This microscope part was removed from a Zeiss microscope stage on which no model designation was provided. Over the years during which Zeiss produced such stages, numerous variants were created (I have personally seen five, for example Zeiss P/N 47 34 28 - 9901 https://www.microscopeparts.eu/microscope/282). Despite this variety, the construction is largely consistent, and most parts are identical.
It is therefore highly likely that the part shown and offered here is compatible with many variants of such microscope stages.

Such stages are interchangeable and can be installed in many Zeiss microscopes, however they are most commonly used in the following microscopes:
- Zeiss Standard 14
- Zeiss Standard 16
- Zeiss Standard GFL

Also often in:
- Zeiss Standard WL
- Zeiss Standard Universal

In the photo gallery there are detailed photos of this element together with the dimensions. Additionally, in the last photo an arrow indicates which element is being referred to and where it is located, in order to clearly identify this part.

Description of this part for the microscope.

a Zeiss P/N 47 34 28 - 9901 (473428-9901). Over the years during which Zeiss produced such stages, numerous variants were created (I have personally seen five, for example https://www.microscopeparts.eu/microscope/281). Despite this variety, the construction is largely consistent, and most parts are identical.
It is therefore highly likely that the part shown and offered here is compatible with many variants of such microscope stages.

Such stages are interchangeable and can be installed in many Zeiss microscopes, however they are most commonly used in the following microscopes:
- Zeiss Standard 14
- Zeiss Standard 16
- Zeiss Standard GFL

Also often in:
- Zeiss Standard WL
- Zeiss Standard Universal

In the photo gallery there are detailed photos of this element together with the dimensions. Additionally, in the last photo an arrow indicates which element is being referred to and where it is located, in order to clearly identify this part.

Description of this part for the microscope.

a Zeiss P/N 47 34 28 - 9901 (473428-9901). Over the years during which Zeiss produced such stages, numerous variants were created (I have personally seen five, for example https://www.microscopeparts.eu/microscope/281). Despite this variety, the construction is largely consistent, and most parts are identical.
It is therefore highly likely that the part shown and offered here is compatible with many variants of such microscope stages.

Such stages are interchangeable and can be installed in many Zeiss microscopes, however they are most commonly used in the following microscopes:
- Zeiss Standard 14
- Zeiss Standard 16
- Zeiss Standard GFL

Also often in:
- Zeiss Standard WL
- Zeiss Standard Universal

In the photo gallery there are detailed photos of this element together with the dimensions. Additionally, in the last photo an arrow indicates which element is being referred to and where it is located, in order to clearly identify this part.

Description of this part for the microscope.

a Zeiss P/N 47 34 28 - 9901 (473428-9901). Over the years during which Zeiss produced such stages, numerous variants were created (I have personally seen five, for example https://www.microscopeparts.eu/microscope/281). Despite this variety, the construction is largely consistent, and most parts are identical.
It is therefore highly likely that the part shown and offered here is compatible with many variants of such microscope stages.

Such stages are interchangeable and can be installed in many Zeiss microscopes, however they are most commonly used in the following microscopes:
- Zeiss Standard 14
- Zeiss Standard 16
- Zeiss Standard GFL

Also often in:
- Zeiss Standard WL
- Zeiss Standard Universal

In the photo gallery there are detailed photos of this element together with the dimensions. Additionally, in the last photo an arrow indicates which element is being referred to and where it is located, in order to clearly identify this part.

Description of this part for the microscope.

a Zeiss P/N 47 34 28 - 9901 (473428-9901). Over the years during which Zeiss produced such stages, numerous variants were created (I have personally seen five, for example https://www.microscopeparts.eu/microscope/281). Despite this variety, the construction is largely consistent, and most parts are identical.
It is therefore highly likely that the part shown and offered here is compatible with many variants of such microscope stages.

Such stages are interchangeable and can be installed in many Zeiss microscopes, however they are most commonly used in the following microscopes:
- Zeiss Standard 14
- Zeiss Standard 16
- Zeiss Standard GFL

Also often in:
- Zeiss Standard WL
- Zeiss Standard Universal

In the photo gallery there are detailed photos of this element together with the dimensions. Additionally, in the last photo an arrow indicates which element is being referred to and where it is located, in order to clearly identify this part.

Description of this part for the microscope.

P/N 47 34 28 - 9901 (473428-9901). Over the years during which Zeiss produced such stages, numerous variants were created (I have personally seen five, for example https://www.microscopeparts.eu/microscope/281). Despite this variety, the construction is largely consistent, and most parts are identical.
It is therefore highly likely that the part shown and offered here is compatible with many variants of such microscope stages.

Such stages are interchangeable and can be installed in many Zeiss microscopes, however they are most commonly used in the following microscopes:
- Zeiss Standard 14
- Zeiss Standard 16
- Zeiss Standard GFL

Also often in:
- Zeiss Standard WL
- Zeiss Standard Universal

In the photo gallery there are detailed photos of this element together with the dimensions. Additionally, in the last photo an arrow indicates which element is being referred to and where it is located, in order to clearly identify this part.

Description of this part for the microscope.

part was removed from a Zeiss P/N 47 34 28 - 9901 (473428-9901). Over the years during which Zeiss produced such stages, numerous variants were created (I have personally seen five, for example https://www.microscopeparts.eu/microscope/281). Despite this variety, the construction is largely consistent, and most parts are identical.
It is therefore highly likely that the part shown and offered here is compatible with many variants of such microscope stages.

Such stages are interchangeable and can be installed in many Zeiss microscopes, however they are most commonly used in the following microscopes:
- Zeiss Standard 14
- Zeiss Standard 16
- Zeiss Standard GFL

Also often in:
- Zeiss Standard WL
- Zeiss Standard Universal

In the photo gallery there are detailed photos of this element together with the dimensions. Additionally, in the last photo an arrow indicates which element is being referred to and where it is located, in order to clearly identify this part.

Description of this part for the microscope.

from a Zeiss P/N 47 34 28 - 9901 (473428-9901). Over the years during which Zeiss produced such stages, numerous variants were created (I have personally seen five, for example https://www.microscopeparts.eu/microscope/281). Despite this variety, the construction is largely consistent, and most parts are identical.
It is therefore highly likely that the part shown and offered here is compatible with many variants of such microscope stages.

Such stages are interchangeable and can be installed in many Zeiss microscopes, however they are most commonly used in the following microscopes:
- Zeiss Standard 14
- Zeiss Standard 16
- Zeiss Standard GFL

Also often in:
- Zeiss Standard WL
- Zeiss Standard Universal

In the photo gallery there are detailed photos of this element together with the dimensions.

Description of this part for the microscope.

microscope stage. Both are the same, and there's no difference between right and left. This knob moves the worm shaft (link: https://www.microscopeparts.eu/part/99272). The specimen holder carrier (link: https://www.microscopeparts.eu/part/99273) is mounted on this shaft and moves the specimen holder sideways (lateral movement).

This microscope part was removed from a Zeiss P/N 47 34 28 - 9901 (473428-9901). Over the years during which Zeiss produced such stages, numerous variants were created (I have personally seen five, for example https://www.microscopeparts.eu/microscope/281). Despite this variety, the construction is largely consistent, and most parts are identical.
It is therefore highly likely that the part shown and offered here is compatible with many variants of such microscope stages.

Such stages are interchangeable and can be installed in many Zeiss microscopes, however they are most commonly used in the following microscopes:
- Zeiss Standard 14
- Zeiss Standard 16
- Zeiss Standard GFL

Also often in:
- Zeiss Standard WL
- Zeiss Standard Universal

In the photo gallery there are detailed photos of this element together with the dimensions. Additionally, in the last photo an arrow indicates which element is being referred to and where it is located, in order to clearly identify this part.

Description of this part for the microscope.

This microscope part was removed from a Zeiss P/N 47 34 28 - 9901 (473428-9901). Over the years during which Zeiss produced such stages, numerous variants were created (I have personally seen five, for example https://www.microscopeparts.eu/microscope/281). Despite this variety, the construction is largely consistent, and most parts are identical.
It is therefore highly likely that the part shown and offered here is compatible with many variants of such microscope stages.

Such stages are interchangeable and can be installed in many Zeiss microscopes, however they are most commonly used in the following microscopes:
- Zeiss Standard 14
- Zeiss Standard 16
- Zeiss Standard GFL

Also often in:
- Zeiss Standard WL
- Zeiss Standard Universal

In the photo gallery there are detailed photos of this element together with the dimensions.

Description of this part for the microscope.

main plate (forward-backward, i.e. longitudinal movement). There are two such knobs in the microscope stage, and the right and left are different. This is the left knob.

This microscope part was removed from a Zeiss P/N 47 34 28 - 9901 (473428-9901). Over the years during which Zeiss produced such stages, numerous variants were created (I have personally seen five, for example https://www.microscopeparts.eu/microscope/281). Despite this variety, the construction is largely consistent, and most parts are identical.
It is therefore highly likely that the part shown and offered here is compatible with many variants of such microscope stages.

Such stages are interchangeable and can be installed in many Zeiss microscopes, however they are most commonly used in the following microscopes:
- Zeiss Standard 14
- Zeiss Standard 16
- Zeiss Standard GFL

Also often in:
- Zeiss Standard WL
- Zeiss Standard Universal

In the photo gallery there are detailed photos of this element together with the dimensions. Additionally, in the last photo an arrow indicates which element is being referred to and where it is located, in order to clearly identify this part.

Description of this part for the microscope.

main plate (forward-backward, i.e. longitudinal movement). There are two such knobs in the microscope stage, and the right and left are different. This is the right knob.

This microscope part was removed from a Zeiss P/N 47 34 28 - 9901 (473428-9901). Over the years during which Zeiss produced such stages, numerous variants were created (I have personally seen five, for example https://www.microscopeparts.eu/microscope/281). Despite this variety, the construction is largely consistent, and most parts are identical.
It is therefore highly likely that the part shown and offered here is compatible with many variants of such microscope stages.

Such stages are interchangeable and can be installed in many Zeiss microscopes, however they are most commonly used in the following microscopes:
- Zeiss Standard 14
- Zeiss Standard 16
- Zeiss Standard GFL

Also often in:
- Zeiss Standard WL
- Zeiss Standard Universal

In the photo gallery there are detailed photos of this element together with the dimensions. Additionally, in the last photo an arrow indicates which element is being referred to and where it is located, in order to clearly identify this part.

Description of this part for the microscope.

In Carl Zeiss Standard series microscopes (with the exception of the Standard Junior teaching microscope), the condenser is not mounted in a circular clamp. Instead, it is fitted with a circular dovetail ring that slides into the condenser mounting guide.

This mounting interface is used on, among others, the following microscope models:
- Zeiss Standard 14 / 16 / 18 / GFL
- Zeiss Standard WL / WL 89
- Zeiss Standard 20 / 25 / 25 ICS
- Zeiss Universal
- Zeiss Photomicroscope I / II / III RS
- Zeiss Ultraphot

The ring has a diameter of 41.3 mm and three mounting holes used to attach it to the condenser. It also features a tapered recess that engages with the locating pin in the condenser holder, ensuring correct positioning of the condenser.

When attached to a condenser made by another manufacturer, this ring makes it possible to use, for example, the PZO KPI-2 DIC condenser and dozens of other condensers on Zeiss Standard-class microscopes.

Note regarding the mounting diameter: during nearly 50 years of production of this microscope series, the dovetail diameter was always approximately 42 mm, but it was never exactly identical. Depending on the production year, the material (plastic, aluminium or brass), and the condenser type (classic Abbe condenser or phase contrast disc condenser), the actual diameter may range from just over 41 mm to almost 43 mm. This relatively large tolerance is a consequence of the condenser holder design. The holder incorporates spring loading, a locating pin and centring/locking screws. As a result, condensers fitted with a mounting ring between approximately 41 mm and 43 mm in diameter can almost always be mounted securely and remain well centred.

Description of this part for the microscope.

phase contrast and darkfield) allow a phase contrast condenser to be configured individually. This makes it possible to use exactly the observation techniques and exactly the microscope objectives required.

Basic parameters of this phase annulus:
Manufacturer: Carl Zeiss (Oberkochen, West Germany)
Condenser marking: "2"
For objectives: marked "Ph2", i.e. magnifications from 16x to 40x
Material: glass mounted in a metal retaining ring with flange
Outside diameter of the retaining ring: 22 mm
Phase annulus glass diameter: 16 mm
Height of the retaining ring: 3.5 mm

Important: this microscope component (phase annulus / phase diaphragm) is not intended for any specific microscope model. It is a component used to upgrade or repair a microscope phase contrast condenser. It is not intended for upgrading or repairing one specific condenser model. Many Carl Zeiss condenser models have a suitable opening into which this phase annulus can be inserted.

This particular phase annulus was removed from a fluorescence phase contrast condenser — an older version of the Zeiss condenser P/N 46 52 78. Before installing it in your condenser, carefully compare the shape of its housing and the dimensions of the retaining ring.

The last photograph in the gallery shows the turret disc of a Zeiss phase contrast condenser. An arrow indicates this very phase annulus — the one offered here — already installed.

Description of this part for the microscope.

Zeiss Standard GFL microscope, but it also fits condenser holders used, among others, in the following microscopes:
- Zeiss Standard 14
- Zeiss Standard 16
- Zeiss Standard 18
- Zeiss Standard WL / WL 89

This filter holder accepts filters with a diameter of 32 mm.

This is not only a replacement service part used when the original filter holder has been damaged (for example, if the spring tab or retaining latch has broken). Many owners of Carl Zeiss Standard microscopes modify their microscopes by attaching another (additional) filter holder to the condenser holder. This is exactly the component required for such a DIY modification.

This filter holder can also be attached to the condenser holder of the following microscopes:
- Zeiss Universal
- Zeiss Photomicroscope
- Zeiss Ultraphot
However, these microscope models were originally equipped with a different type of filter holder.

The last photographs in the gallery show examples of use — this filter holder fitted with a blue filter and with a DIY insert made using a 3D printer.

Description of this part for the microscope.

condensers.

Basic parameters of this clear glass insert:
Manufacturer: Carl Zeiss (Oberkochen, West Germany)
Material: glass mounted in a metal retaining ring with flange
Outside diameter of the retaining ring: 22 mm
Diameter of the clear glass disc: 16 mm
Height of the retaining ring: 3.5 mm

Below are some example applications for this clear glass blank. It can be printed or fitted with, among others:
- a phase annulus or darkfield annulus matching the original one that was installed in the condenser but has become damaged
- an annulus missing from the condenser
- coloured Rheinberg rings
- oblique illumination diaphragms producing a DIC-like effect
- a Hoffmann modulation contrast pattern
- phase annuli for objectives made by other manufacturers, for example Carl Zeiss Jena PhV
- any completely custom DIY design

This particular clear glass ring insert was removed from a fluorescence phase contrast condenser — an older version of the Zeiss condenser P/N 46 52 78. Before installing it in your condenser, carefully compare the shape of its housing and the dimensions of the retaining ring.

Interchangeable diaphragm carriers (whether for phase contrast or, for example, darkfield) make it possible to configure a phase contrast condenser exactly as required. This allows the condenser to support precisely the observation techniques and microscope objectives needed.

The clear glass blank presented here is not a component intended for any specific microscope model. Instead, it is used to upgrade or repair a microscope phase contrast condenser. Likewise, it is not dedicated to any specific condenser model. Many Carl Zeiss condenser models have a suitable opening into which this complete insert can be fitted and customised with your own pattern.

The last photograph in the gallery shows the turret disc of a Zeiss phase contrast condenser. An arrow indicates the clear glass ring insert offered here, already installed.

Description of this part for the microscope.

applications.

Replaceable diaphragms (both for phase contrast and darkfield) for phase contrast condensers allow the condenser to be configured individually. Thanks to this, it can support exactly the observation techniques and exactly the microscope objectives that are required.

Important: by installing the fluorescence-polarization diaphragm presented here, a condenser currently equipped with standard phase contrast diaphragms can be upgraded with this unique function. A detailed description of the capabilities offered by this technique is provided below.

Basic parameters of this phase contrast diaphragm:
Manufacturer: Carl Zeiss (Oberkochen, West Germany)
Condenser marking: "2". On the Zeiss condenser P/N 46 52 78 this position is marked in blue
For microscope objectives: to obtain phase contrast operation, use microscope objectives marked "Ph2", i.e. objectives with magnifications from 16x to 40x
Substrate material: glass mounted in a metal holder with a flange
Ring material: polarizing film
Outside diameter of the retaining ring: 22 mm
Glass disc diameter: 16 mm
Retaining ring height: 3.5 mm

Important: this component (phase contrast annulus / phase contrast diaphragm) is not intended for a specific microscope model. It is a component for upgrading or repairing a microscope phase contrast condenser. It is not intended for upgrading or repairing any specific condenser model. Many Carl Zeiss condenser models have a matching opening into which this phase contrast annulus can be installed.

In the Carl Zeiss condenser P/N 46 52 78, the phase annuli in positions 2 and 3 are not ordinary openings in an opaque mask but openings in a polarizing film. The polarization direction of these annuli is N-S, so the direct light beam that forms the phase contrast image is linearly polarized. Since it is polarized, its intensity can be adjusted continuously with a second polarizer – without any mechanical parts, diaphragms or shutters.

This second polarizer can be any pair of rotatable polarizing filters. In the original Zeiss design, this is the Carl Zeiss light control unit P/N 47 72 20 with two independently rotatable polarizers mounted beneath the condenser. This makes it possible to switch on phase contrast while simultaneously reducing the illumination intensity to a safe level.

- when the polarizer is aligned parallel to the N-S axis of the annulus – full transmission, maximum phase contrast beam, full-strength phase contrast image;
- when the polarizer is crossed (E-W) – the annulus "goes dark", the objective phase plate no longer receives the direct beam, and the phase contrast image disappears;
- when the polarizer is set to intermediate positions – smooth adjustment of the contribution of the phase contrast image.

When the illumination source is a fluorescence lamp (or, of course, an LED FL light source), simply rotating the polarizer beneath the condenser (together with removing the excitation filter) allows the user to switch from a fluorescence image to a conventional phase contrast image. With the polarizer crossed and the excitation filter installed, the phase annulus is extinguished and only pure fluorescence is visible; as the polarizer is rotated, the phase contrast image gradually increases and is superimposed on the fluorescence image. The second polarizer in unit P/N 47 72 20 is additionally used to attenuate the overall illumination intensity (to protect the specimen or to control the specimen's exposure to fluorescence light).

And now an interesting note from the Ultraphot-shop website https://www.microscopeparts.eu/(http://www.the-ultraphot-shop.org.uk/bicolor.htm), © Spike Walker 2007:

Because the annulus is a linear N-S polarizer, it can be used to produce coloured phase contrast: when a two-colour polarizing filter (Cokin type) is placed between the microscope polarizer and the condenser annulus, the specimen takes on the colour of the illuminating annulus against the background colour of the remaining part of the disc – for example, an orange specimen on a green background when using a red-green filter.

This particular phase contrast annulus was removed from a fluorescence phase contrast condenser – an older version of the Zeiss condenser P/N 46 52 78. Before deciding to install it in your condenser, carefully compare the shape of its housing and the dimensions of the retaining ring.

The last photograph in the gallery shows the turret from a Zeiss phase contrast condenser. The arrow indicates the phase contrast annulus offered here, already installed.

Description of this part for the microscope.

applications.

Replaceable diaphragms (both for phase contrast and darkfield) for phase contrast condensers allow the condenser to be configured individually. Thanks to this, it can support exactly the observation techniques and exactly the microscope objectives that are required.

Important: by installing the fluorescence-polarization diaphragm presented here, a condenser currently equipped with standard phase contrast diaphragms can be upgraded with this unique function. A detailed description of the capabilities offered by this technique is provided below.

Basic parameters of this phase contrast diaphragm:
Manufacturer: Carl Zeiss (Oberkochen, West Germany)
Condenser marking: "3". On the Zeiss condenser P/N 46 52 78 this position is marked in blue
For microscope objectives: to obtain phase contrast operation, use microscope objectives marked "Ph3", i.e. objectives with magnifications from 40x to 100x
Substrate material: glass mounted in a metal holder with a flange
Ring material: polarizing film
Outside diameter of the retaining ring: 28 mm
Retaining ring height: 6 mm

Important: this component (phase contrast annulus / phase contrast diaphragm) is not intended for a specific microscope model. It is a component for upgrading or repairing a microscope phase contrast condenser. It is not intended for upgrading or repairing any specific condenser model. Many Carl Zeiss condenser models have a matching opening into which this phase contrast annulus can be installed.

In the Carl Zeiss condenser P/N 46 52 78, the phase annuli in positions 2 and 3 are not ordinary openings in an opaque mask but openings in a polarizing film. The polarization direction of these annuli is N-S, so the direct light beam that forms the phase contrast image is linearly polarized. Since it is polarized, its intensity can be adjusted continuously with a second polarizer – without any mechanical parts, diaphragms or shutters.

This second polarizer can be any pair of rotatable polarizing filters. In the original Zeiss design, this is the Carl Zeiss light control unit P/N 47 72 20 with two independently rotatable polarizers mounted beneath the condenser. This makes it possible to switch on phase contrast while simultaneously reducing the illumination intensity to a safe level.

- when the polarizer is aligned parallel to the N-S axis of the annulus – full transmission, maximum phase contrast beam, full-strength phase contrast image;
- when the polarizer is crossed (E-W) – the annulus "goes dark", the objective phase plate no longer receives the direct beam, and the phase contrast image disappears;
- when the polarizer is set to intermediate positions – smooth adjustment of the contribution of the phase contrast image.

When the illumination source is a fluorescence lamp (or, of course, an LED FL light source), simply rotating the polarizer beneath the condenser (together with removing the excitation filter) allows the user to switch from a fluorescence image to a conventional phase contrast image. With the polarizer crossed and the excitation filter installed, the phase annulus is extinguished and only pure fluorescence is visible; as the polarizer is rotated, the phase contrast image gradually increases and is superimposed on the fluorescence image. The second polarizer in unit P/N 47 72 20 is additionally used to attenuate the overall illumination intensity (to protect the specimen or to control the specimen's exposure to fluorescence light).

And now an interesting note from the Ultraphot-shop website https://www.microscopeparts.eu/(http://www.the-ultraphot-shop.org.uk/bicolor.htm), © Spike Walker 2007:

Because the annulus is a linear N-S polarizer, it can be used to produce coloured phase contrast: when a two-colour polarizing filter (Cokin type) is placed between the microscope polarizer and the condenser annulus, the specimen takes on the colour of the illuminating annulus against the background colour of the remaining part of the disc – for example, an orange specimen on a green background when using a red-green filter.

This particular phase contrast annulus was removed from a fluorescence phase contrast condenser – an older version of the Zeiss condenser P/N 46 52 78. Before deciding to install it in your condenser, carefully compare the shape of its housing and the dimensions of the retaining ring.

The last photograph in the gallery shows the turret from a Zeiss phase contrast condenser. The arrow indicates the phase contrast annulus offered here, already installed.