Olympus PME microscope

The last of my Olympus microscopes : an inverted metallurgical instrument Olympus PME from the 1970s
- a fortuitous purchase.

by Daniel Nardin, France

In August 2010, I bought a set of microscope equipment sold by a private seller on the French second hand web site "Le bon coin". It probably originated from a laboratory of metallography or electronics...

One of the two main elements of the set is this inverted metallographic microscope shown right.
The design of this type of microscope incorporates a heavy and wide base which contains the electrical supply, a light metering system, a camera link and a frosted screen.

This is an
Olympus PME, model sold by Olympus from 1967!
(For a short history of the firm see: http://www.olympus-global.com/en/corc/history/micro/headstand.cfm )

It is equipped with five objectives of type M from the 1970s;
the design in which Olympus used 37 mm parfocality intended for a 210 mm tube length.
The characteristics of these optics are described in the brochure below on pages 8-10:

The microscope did not look in fine condition; The original lamp, the two light and colour temperature
sensors were missing. 
(There was in the auction an Olympus EMM-7 cell. Probably, the former owner did not try to repair the breakdown of the base. He replaced the complex internal system by external accessories.)

PME acheté
But it was accompanied with three wooden boxes of accessories, typical of the era before plastic packaging :
- Filters, frosted glass, canisters, but empty of objectives. - Adaptor for dark field with three Neo lenses - Camera backs for large film holder.
boite filtres PME
The neutral grey filters, polarisers and light correction filters ... are useful.
Boite fond noir
This adapter is regrettably broken.
Includes a set of oblique filter stops.
boitecone GF PME
A second screen is supplied.

I have had to make some repairs (repair an ocular, re-lubricate the movements of head, and repair the electrical connections, buy a new bulb for 6, and to clean everything).
But fortunately, there was in the lot a separate Olympus lamp on stand; nothing was irreparable and the set was functional.
Why did I decide to buy a set to add to my collection?

It is less efficient than my metallographic model more recent BHM (years 1980-90) with infinity optics.
This last one is more comfortable and allows in particular an easier transfer between bright and dark field by simple exchange of turret. While the black bottom of the PME requires a dismantling and the change of objective is made by slide channel.

But as an inverted model,
the PME allows ready study of the surface of large subjects which are too voluminous to pass between the objective and the stage of a BHM.

( And just for this limited feature, it would not be worth buying the more recent equivalent PME3, even as a bargain on eBay and which is up to 10x more expensive!).

Here is the surface of an old vinyl record with the engraved track.
It is an example of a large subject requiring a stage without side constraints.
( Unless you wish to break the record to make the observation!)

( Image taken with the microscope PME, its objective 10x and Nikon D200)
Another advantage of the PME is the presence of a frosted screen for display.
It can be used by more than one viewer for assessment of a subject and to draw on tracing paper.

This kind of screen is not very bright and requires work using low ambient room lighting.
It was advantageously replaced by video systems in the 1980s.

For the demonstration shown right, I placed one screw of diameter 2 mm on the stage.
It is imaged by a low power 1,3x objective with a 7,5x projection eyepiece in the base.

A rotary dial allows magnifications to be set between 7,5 and 15x for projection on this screen.

écran PME
obturateur PME One noteworthy feature of the models of this period is that their mechanics are relatively easy to understand for possible repair (as for film cameras versus digital cameras).

The camera shutter is in a simple drawer above the four turret projection lenses of 7,5x to 15x. 
projectifs PME

The presence of multiple photo/viewing ports is an original feature on this model.
Besides the classic binocular head and the frosted screen, two other ports are available: one for photography and another for a photoelectric cell.
The photo port was designed for both large or small sized film; the original Olympus camera for 35 mm was not included. I have only the adaptor for a brand of reflex camera which I did not identify. I replaced it with a Nikon bayonet adaptor fixed by three screws. It allows me to take photos even if it is not parfocal with the visual field. The internal shutter does not work other than in bulb 'B' or for the 1/60th setting (and be left open using a cable release).
To note, a three position fitting allows all light to be sent to one of the three secondary ports; this design limits light loss.

The light cell port is the same diameter as an RMS eyepiece and gives an exploitable image, for example by a small webcam sensor and even by a device with an APS size sensor such as my Nikon D200 digital SLR!
(But a full size capture gives circular images, of about 26 mm diameter on the sensor, example below.)

champ au D700
There is no parfocality either, but the focus can be made in the viewfinder.
The advantage of this port is to give an image not enlarged by projection, thus a wider field.

With a little adaptation, the old models can be used for digital images.
D200 sur PME
test PME: Circuit imprimé In one of the boxes, there were four preparations:
They are fragments of printed circuits embedded in a resin and cut and polished perpendicularly. I used them for my first tests.

I located metallic tracks deposited around holes and around the weld which fills these holes. ( D200, PME, objective 10x).

This model can be used in transmitted light. A lamp was an option originally available for it.

And the lamp on stand which came with the outfit (or another one) can be used for inverted biological type studies to observe e.g. plankton in a Petri dish. I can also use a second lamp to mix the lighting.

It works with the low power objectives M 2,5x and 1,3x which I owned. The use of the 1,3x with long working distance is another advantage of this model. (I have no equivalent for an inverted biological stand such as my Olympus CK2.)

But with the low power settings, the brightfield reflected light gives only a bad image. With a 1,3x the images are much better in darkfield.

In fact, a stereomicroscope is more effective at this low power and allows more effective work with a small Petri dish.


Lemna au 1,3x Look at these two subjects viewed from below with a 1,3x lens in a Petri dish.

Lemna (duckweed) and small dragonfly larva (which moved during image capture);

au 1,3x
Among the three benefits: the observation of large subjects, the ability to view on the screen and the use with very low magnifications in a dish, 
only the first one is valid.
This device remains a beautiful collector's item. But which could still be improved:

bricolage PME lampe As I did not find an original lamp, I drilled two holes in a wooden cube to replace the permanent lamp for reflected lighting.
(That  left the base of lamp for another use.)

The device is shown right in current configuration of use, but would be more attractive with its original stem.

If readers see or have a PME out of order for sale, I would be interested in the lamp (or other accessories,  as the lamp for transmitted light studies)!


PME final

Buyers of such older microscopes must be prepared to learn: it is necessary to do odd jobs to make small repairs if we want to take advantage of such purchase opportunities.
It is necessary to use the screwdriver, the electric tester and to use a little elbow grease for the cleaning, but the result is worth it.
It gives the owner pride to have brought out of an attic a device back to working order.
For that purpose, in spite of the rather high price of this auction lot, I am not on reflection dissatisfied with the acquisition,  even if it is more interesting as collection item.
The regular use with large subjects will be limited for me.  I am a naturalist and a biologist, not metallurgist! I observe with several Olympus of the 1980s in "160mm": biological BH2, metallographic BHM = reflected light, biological inverted CK2)

Daniel Nardin
September 29th, 2010

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