B&L Photomicrographic Apparatus VI: AX-1

The final development, before the microscope camera went from still-chemical photography to motion/still digital photography is equal parts groundbreaking and re-purposing. Like the System II the new version maintained the same basic layout and universality, it was made compatible with all the camera backs of the System II. It retained the focusing knob (to date all those known are marked at 3x, 5x, 7.5x, and 10x) but departed from the consumer camera style shutter speed selector and remote shutter release; the new camera was automated.

Since the earliest days of photomicrography it was just assumed the the microscopist would be the darkroom technician as well. Those seeking to record images of their work were expected to practice and understand the skills needed not only for obtaining a clear, useful image at the eyepiece, but at the imaging surface of their camera, and final media as well. Books from the golden age are filled with detailed information on how to properly compose and sequentially expose test images. Entire chapters in books on general microscopy are devoted to the proper taking of photomicrographs. In detailed texts on photomicrography extensive chapters describe the best way to salvage (and in future avoid) over or under-exposed films. The AX-1 changed all that.

 

For a generation that grew up (or like the author, grew complacent) with the automatic exposure and aperture cameras of the “Kodak Moment” era, the AX-1 no doubt seems unduly complex. A two variable analog meter, no less than six buttons-two thirds of which light, two additional indicator lights, four tumbler set values, all run off of a grounded AC plug in a package the size of a lunch box and weight of a bag of sugar is understandably daunting. The space-hogging controller is only half the unit and like it’s counterpart is entirely useless without the automatic shutter assembly camera. As previously mentioned it is superficially like the System II but in place of a release bears a nine pin cable and connector that conducts light data from its integrated sensor to the control box and carries the exposure signals back. A small electromagnet actuates the simple shutter, and the photo-sensor is positioned to one side of a right angle partially silvered reflector.

To allow for the proper calculation of required exposure one must set a few parameters on the controller before beginning. Film speed is dialed in using A.S.A. units and it’s worth noting that the controller uses the 1960 revision (from what I can tell in use, I’ve not been able to locate anything in the documentation). One must also select the desired reciprocity, which is best left set to “OFF” for most uses. Setting the level of magnification to the nearest value marked on the shutter informs the photo-sensor of the general range of light intensity and is vital for achieving accurate exposure times and light levels. One may also set the desired exposure to a fixed value darker or lighter than the calculated exposure which may be useful for those who want to avoid pushing or pulling during processing.

Once properly set up the user is ready to set the focus of the shutter assembly, load film, power up and begin taking pictures at the push of a button! Imagine, no need to shoot and develop costly trial exposures or to calculate required shutter speeds/exposure times by hand with based on light meter readings. The device can serve as a light meter only and exposure may be done manually at the press of a button. The controller can be put on a separate table and the only source of vibration limited to the movement of the shutter itself. That’s probably the chief point in the AX-1’s favor these days, but it may still be worth while for those more willing to give it the space than to learn about shutter speeds.

-K

B&L Photomicrographic Apparatus V: System II

A Re-design

The System II represents a fundamental change in B&L integrated photomicrographic cameras. Sleeker than the early DynaZoom camera but far more substantial than the later versions, the System II is a step back to the design principles that required a focusing system. It was necessary for the System II to feature a focusing lens system because the unit was intended to be a new universal device for all (camera ready) professional B&L lines, including the earlier DynaZoom/DynOptic lines. Despite maintaining the compatibility of the system with earlier stands, once more the camera backs required are not compatible with previous versions (although they do come in all previous formats).

New Features

The opticians behind the System II seemingly asked themselves ‘how can we make this the last camera a microscopist will need?’ and set about answering it. The systems chief major departure is the coupler, specifically its diameter. At 7/8ths it’s a full quarter inch larger than the previous model DynaZoom camera, and a return to the large size used with focusing DynaZoom cameras. Care was also taken in the design of the coupler, it was made to be removed and a number of versions of the coupler were made, some making allowance for the use of a manual exposure meter.

Once more the camera back attachment point was redesigned. The new male dovetail fitting was made a bit smaller than those used previously and unlike previous models did not feature an alignment screw that required the female dovetail camera back be fixed in relation to the camera. Additionally, where earlier camera backs used two thumb screws the new versions used only one; making it a simple thing to orient the photosensitive surface however one wished without being forced to suffer an inconvenient shutter release or winder position.

Couplers and Camera Backs

Three couplers are known of: the silver Bal-Coated male dovetail, the black lens-less male dovetail, and the eyepiece mount. The silver dovetail makes good use of a Bal-Coated lens to eliminate errant reflection which can prove frustrating with uncoated optics and both it and the black dovetail carry a small slot in the dovetail that mates with the camera. This slot may be turned to align with a similar slot in the System II or turned so as to exclude all light. The purpose of the slot is to permit the insertion of the B&L Cat. # 421240 exposure meters sensor.

Versions

The versions are discrete rather than explicit, which is to say there is not any particular model number to distinguish them that is official but they are readily identifiable. One sort is focusable from below 3x to over 10x. On these models only four magnifications are marked: 3x, 5x, 7.5x, and 10x. Two versions of this sort are known, one having an all black shutter speed selector and the other having a silver ring. An additional version, and perhaps more desirable (if less common) one has the same range but is marked in one unit increments from 0-25x with every fifth mark being numbered.

Accessories

Apart from the previously mentioned camera backs a number of accessories were produced. Special viewfinder adapter plates and eyepieces were available for the various camera backs. It should be noted that these eyepieces were not the film area viewfinder eyepieces that would show the field that would be covered by various popular film sizes. Extension tubes were also available that would extend the distance between the final lens element of the shutter assembly and the camera back. Tubes were made in 2.5x and 5x lengths were produced and could be used in various combinations where special needs required.

Notes:

∗It should be noted that the connection to the shutter in all cases is a male dovetail and the designation here refers to the connection to the microscope photo-port.

†I’ve seen one in use during the course of a museum visit although I’d be hard pressed to say if it were an actually B&L item or the product of a machinist and a tight budget.

B&L Photomicrographic Apparatus III: Integrated Cameras

Microscope Stand Design

Around the halfway point of the last century (1940 or so) microscope design began to change drastically. Modern manufacturing and engineering, together with the proliferation of compact, bright, electric lamps contributed to an opticians ability to design microscopes which provided a new option for the photomicrographer. Contemporarily advertised as tri-nocoular (but more properly referred to as photomicrographic) microscopes began to become available with specialized camera ports that did not require interchanging a binocular body for a monocular body, or the occupation of a standard eyepiece tube by a cumbersome attachment camera.

At the time this was a considerable advance and as photographic process became more accessible and streamlined so too did the process of making ones microscope ready to capture an image. In many cases a microscope could be used visually as normal and simultaneously outfitted with appropriate apparatus capture images on a variety of media. Ones microscope could stand ready for either photomicrography or visual use and a great many sights that were only previously fleeting could be captured.

Regrettably, while some mechanical aspects such as the Royal Microscopical Society (RMS) thread, or 23.2mm eyepiece have become standard, the same can not be said of photomicrographic apparatus. For obvious reasons apparatus from one manufacture may not be compatible with another. Infuriatingly, apparatus from a given manufacturer may not be immediately compatible with a different line or generation of microscopes.

The Systems

It can be impossibly difficult to find information on the integrated camera systems of Bausch & Lomb, so forgive any inaccuracies and permit the establishment of two broad categories; the DynOptic/DynaZoom (hereafter DynaZoom camera) and the Integrated Camera System II (hereafter System II). Each was available with a range of formats and in a variety of styles with various interchangeable or permanently fixed accessories.

The DynaZoom camera was created specifically for the so named line of microscopes and was available throughout the life of that line. When the black finish stands were replaced by the slate finish models the cameras followed suit but maintained the established standards and are interchangeable with the earlier versions and vice versa.

The System II was in simultaneous production with the DynaZoom but was created so as to be compatible with a wide range of microscope lines and to offer improved options and forward compatibility. While still compatible with both the black and slate DynaZoom microscopes it could also be fitted to StereoZoom, and BalPlan microscopes as well as Bausch & Lomb Bench Metallographs, and inverted microscopes. System II also saw the introduction of automatic shutter control with electronic light metering.

One may immediately identify the camera system because in the DynaZoom cameras of every sort there is no independent magnification (focus) control. System II cameras of every sort feature a vertically oriented magnification (focus) control which may be marked from 0 too 25 or from 3x too 10x.

Sorry for the long silence, computer failure and a new job have eaten up a great deal of my time lately. I promise the next post wont be so far away. -K

B&L Photomicrographic Apparatus II: Attachment Camera

The Attachment Camera

The attachment camera as designed by Bausch & Lomb remained primarily the same over its production life. Changes to the apparatus itself were minor and all components have proven interchangeable if one is faced with assembling a complete working device from multiple units purchased separately for parts. The shutter features the following speed settings: 1/10, 1/25. 1/50, 1/100, 1/200, B, and T, and uses a standard cable release. There is no prism release as may be found on attachment cameras from other manufactures. This is a bit of a trade off, as without the prism release one can not direct 100% of available light to the camera. Fortunately, absence of a prism does eliminate its motion as a source of vibration during exposure. In place of a swing out prism a preferential beam splitter is fitted which directs 85-90% of available light to the camera and from 10-15% to the viewer. Aside from the camera itself (see below) the part most likely to be missing is the ocular sleeve which is a metal collar that slips over the tube of the microscope prior to the fitting of an ocular. The sleeve holds the shutter assembly in alignment with the optical axis of the microscope and holds the beam splitter at the exit pupil of the ocular.

This design requires a vertically oriented microscope tube. If used with a classic style B&L Dynoptic binocular microscope one will need to obtain the interchangeable monocular body. When attached the viewfinder projects horizontally towards a seated microscopist. There are two varieties of viewfinder both projecting significantly from the axis of the microscope so that the microscopist need not lean in uncomfortably when using the camera. Each sort makes use of a ground glass screen which the older version views through a large fixed focus condenser. The newer variety uses a spiral focus condenser that improves the clarity which one obtains to a certain extent, but does require that the user lean in towards the lens for proper viewing. Focus is entirely via the controls of the microscope.

Cameras

The camera bellows and bodies that are available for the unit run the gamut. Most common of the camera attachments is the 35mm camera body. The camera itself is often quite diverse and might be any of a half dozen different models. As of this writing the author has found the following 35mm camera bodies: Argus (stripped down, unknown model), Kodak Pony (without view finder), Kodak ColorSnap (complete with permanent lens mount). There are two lengths of bellows tube for the 35mm camera, one providing a 5x enlargement, the other 10x. Each tube is equipped with a dark slide.

Less common is the 2¼ x 3¼ cut film holder which is not equipped with a dark slide. The fixed enlargement factor metal bellows cone is felt lined internally and is confirmed as compatible with Kodak film holders and plates. There may or may not have been a ground glass focusing screen but considering the standard size of the film holder it is simple enough to obtain one from a third party source. Thankfully, a ground grass screen is not necessary as the film plane is parfocal with the fixed focus ground glass viewer. Film is only infrequently available from a limited number of suppliers but may be desirable if one has access to a dark room and a willingness to cut down more commonly available film stock. It is not compatible with the common 120 roll film Graflex camera backs without modification to the camera back or a homemade light seal.

The 2¼ x 3¼ Polaroid instant film pack camera backs may be found and makes use of the 10 exposure peel apart film now produced by Fuji. Although the images obtained are very nice, and provide an easy introduction to medium format photomicrography, the difficulty of pulling film from the camera (so that the chemistry is applied to the film) will require verification of alignment between exposures. The commonly available backs compatible with Graflex cameras are not compatible with the above described bellows. An additional model permanent camera is fitted to a plastic fixed enlargement factor bellows cone and is not outfitted with a dark slide. Unless one has a Polaroid back that is known to be interchangeable with a Kodak film holder it is advisable to obtain the permanent Polaroid version if one is set upon using that format.

The 4 x 5 camera bellows is infrequently seen but provides the best option for those interested in medium or large format photomicrography. A scaled up version of the 2¼ x 3¼ camera, it is metal and felt lined and like it’s smaller counterpart, also does not have a dark slide. The cone is compatible with 4 x 5 camera backs, of all sorts including cut film, film pack, and plate holders. Off the shelf 120 roll film backs from Graflex are compatible and the ease of using such a system can be an economical way for the beginner to get involved with large and medium format chemical photomicrography. Depending on the winder it may be necessary to remove the metal spring that holds cut film plates in place. Ground glass focusing screens are simple to find or make with a bit of glass and a dab or carborundum grit, but the original screen features a thick rubber frame.

Use

No doubt everyone can picture the attachment camera in use on a classic monocular microscope. In the interest of displaying something one might not have considered, below is an image of the attachment camera (with Polaroid back and spiral focus viewfinder) in service on a Phase Contrast DynaZoom as well as two detail images of the difficult to find ocular sleeve.

 

Notes:

∗Images in reference works term the apparatus the “Model N” attachment camera but I have not been able to locate the appropriate B&L catalog or manual to confirm the proper name.

†The camera back is slightly too wide and thick. A few minutes with a hobby grinder or similar tool is all that is needed to permanently adapt a roll film back. If one is unwilling to dedicate a camera back, a thick felt gasket may be glued to the back and cut so that it projects slightly into the bellows cone to prevent it from being jostled while in use.

‡The hardest part is cutting the glass to the right size and it isn’t even that hard if one has ever cut glass.

On Photomicrographic Apparatus

Modern Variety

There is a staggering amount of digital photomicrographic equipment. Modern student or college level microscopes outfitted for photomicrography have moved away from the previous standard of the tri-nocular head with detachable camera, and are now frequently found with dedicated integral digital cameras. The downside of such cameras aside from the added initial expense (which may double the cost of a comparable binocular microscope) is the inability to upgrade to a superior camera as advances are made or funds become available, and the software requirements. The upside is the possession of a tailored optical system that (ostensibly) has been designed with a knowledge of the microscopes optical system.

The contemporary alternative is the digital eyepiece camera or the eyepiece relay adapter. Despite the versatility of such things their occupation of an eyepiece may greatly complicate the normal use of the microscope. Such secondary optics might just as easily result in inferior image quality depending on the optical system of the microscope. Various artifacts and aberrations may be unavoidable and not immediately apparent.

Classic Variety

Putting aside the issue of format for a moment, classic photomicrographic equipment falls into the same two broad categories as modern digital photomicrographic gear. The traditional attachment camera was designed for use with monocular microscopes and many binocular microscopes were available with an interchangeable monocular body to be used with the photomicrographic outfit. Such apparatus was generally designed so as to use an ocular which could be varied depending on the objectives employed or magnification desired. Unlike modern equivalents most used a beam splitter to provide a viewing port for focusing, those which did not made use of a ground glass screen which could be interchanged with the film or plate holder.

The second category relied upon specialized microscope viewing heads which were designed with a beam splitter which would send a portion of the light into a photomicrographic camera system. Nearly all lines of microscopes by the major houses were available with photomicrographic heads of different sorts encompassing the solely photomicrographic (without provision for visual use) to the monocular and binocular photomicrographic (trinocular). Such microscopes relied on the use of compatible photomicrographic systems generally provided by the manufacturer.

Hazards

An off-the-shelf microscope equipped for digital photomicrography will undoubtedly function but one risks being tied to an overly simplistic microscope that does not meet the requirements of the microscopist as they grow in their ability. The same might be said of a modern or classic microscope outfitted with a digital camera and an eyepiece adapter, with the added difficulty of uncertainty of the suitability of the system. For modern photomicrographic equipment then the chief hazards is inferior equipment and the easy of excessive digital image modification.

Classic photomicrographic gear is only very infrequently available as a complete system in good working order. Obtaining results that do it justice is often heavily reliant on the ability of the user to locate and properly employ gear which was originally designed for use with a given microscope line. Such efforts are often complicated by the lack of relevant documentation or informed sellers§ who greatly increase the difficulty of locating equipment by selling it under some other designation. Recognizing compatible equipment on sight is inherently difficult. Attachment cameras using chemical photographic formats provide resolution that well exceeds consumer grade digital cameras, but one suffers for the time and expense of development and processing of significant numbers of test photomicrographs while getting the equipment in working order.

Recommendations

One can obtain a perfectly suitable modern microscope and outfit it for digital photomicrography at a reasonable cost, assuming of course the images are not required to be used for serious work. A student microscope designed for entry level photomicrography might easily run $500.00 US and one suitable for college level work could exceed $1000.00 without batting an eye. Regrettably, such microscopes are generally inferior to used professional microscopes of similar cost, but for assurance of capacity one could not be faulted for going that route.

A used professional grade trinocular microscope (such as the B&L DynaZoom, DynOptic, BalPlan, AO Spencer 10, Microstar, or 2/4) from any of the major houses may generally be found for far less than all but the cheapest modern student microscopes. Many microscopists have no interest in chemical photomicrography, however, what is seldom considered is that such microscopes as mentioned above existed at a time when the C-mount video camera was in wide use. After obtaining a trinocular microscope one should endeavor to find the c-mount photo-tube sold by the original manufacturer. This author is personally aware that such tubes exist for Bausch & Lomb and AO Spencer, an is told it is true of Olympus, Ziess, and Nikon as well.

One may just as well go the above route and in place of a difficult to find c-mount tube purchase a widely available Polaroid instant camera system designed for the microscope. Film remains available for the more common formats and one has all the benefits of chemical photography without the need of expensive darkrooms or tedious developing processes.

Notes:

∗As distinct from antique photomicrographic equipment which should be taken to include the bellows outfitted horizontal and vertical cameras.

†Alternatively the microscope head might be equipped with a control which would direct 100% of available light to either the ocular(s) or the photomicrographic outfit.

‡By this is meant the difficulty of using a system that can not be tested before hand—most equipment must be purchased on the internet—and the difficulty of recognizing unforgivable visual artifacts and aberrations as a beginner.

§Most of the authors photomicrographic equipment was obtained from dealers who incorrectly identified it as projection or aerial photography gear.

Simple Polaroid-based Polarizing Apparatus

The Polaroid

One is going to need a quantity of polarizing film (polaroid) for any easily constructed polarizing apparatus. Fortunately, the material is inexpensive and readily available from any number of sources online. When seeking the material for construction one should purchase linear polarizing polaroid rather than the circularly polarizing filters common in photography. Do not hope to luck out with a bargain by purchasing the sort of polarizing film sold for use with LCD screen repair and refurbishment, it will not prove suitable.

The size of the film purchased will vary depending on the sort of apparatus which is planned but in most cases a small piece of five square centimeters (two square inches) is enough. One shouldn’t feel obligated to purchase expensive polaroid whether that expense is attributed to the supposed quality of the film (the perfectness of the polarization) or its thickness or any protective coating. Very often one may have the option to purchase polaroid in varying thickness, and the thicker film is useful for applications that require a large self-supporting filter, but in many cases the thinner product is preferable simply because it is easier to work with.

The Example

Not one to miss out on a potential market, Bausch & Lomb marketed a simple polarizing apparatus for users who did not require (or have the budget for) the more complex prism-based variety. Below is seen an exceedingly simple set composed of polarizing film set into light metal frames. One portion is a 21mm disc and the other is of 32mm, a split ring retainer is included. The concise instructions on the reverse of the box direct the user to install the smaller disc in a standard eyepiece by separating the components of the eyepiece so that the disc may rest upon the eyepiece diaphragm. The eyepiece itself then becomes the analyzer which is in this instance the rotating component. The 32mm disc is sized to be compatible with filters used in most substages and serves as the polarizer.

Simple commercial example of a type anyone can produce.

Simple commercial example of a type anyone can produce.

Right away one can see that an essentially identical set may be produced for just a few dollars. If one is loath to risk the cleanliness of an ocular by separating the components to insert the analyzer, a cap may be fashioned that holds the polaroid and fits above the microscopes eyepiece. It will work in precisely the same fashion and has the advantage of not requiring an ocular be put aside for polarizing work only. Regrettably, one will recognize very quickly that such a set, whether the analyzer is integrated with an ocular or placed over it, will not work effectively on a binocular or trinocular microscope.

Special Considerations

For microscopes equipped with binocular or trinocular heads, one should place the analyzer in a location such that it acts upon the light prior to that light being sent into the eyepiece or photo tubes. Fortunately it is often a simple matter to remove the microscopes head and place the analyzer within. Once the analyzer is positioned one must look to the way in which the polarizer may be accommodated. In most cases it is not advisable to use a 32mm disc placed in the substage filter holder simply because rotating it once positioned is inconvenient. Very often only a small effort need be expended to create a holder that may be placed in the substage to facilitate rotating the polarizer. In any case one should endeavor to arrange polarizer and analyzer so that both may be quickly removed or installed, and one of the two is rotatable.

Improvised polarizer and analyzer in place on AO Spencer microscope

Improvised polarizer and analyzer in place on AO Spencer microscope

In the photograph at right one can see that a simple disk of polarizing film has been placed intermediate to the objective turret and trinocular head of this AO Spencer Microstar microscope to serve as the analyzer. A rotating polarizer has been constructed from a plastic film canister lid and aluminum screw cap, it fits conveniently in the 32mm filter recess of the microscopes integrated illuminator. By virtue of the microscopes construction only one finger screw needs to be loosened to remove the head and place the analyzer. For ease of handling, and so that it may serve double duty the analyzer was cut to a size of 32mm and may be used as the polarizer when placed in the substage filter holder of a monocular microscope. One should note that the polarizer is of a size that no light may pass out of the integrated illuminator that does not pass through the polarizer.

Next time: eye-candy! A few nice photomicrographs of slides with bright-filed and polarized light. -K

Polarized Light Microscopy Apparatus

The Polarizing Prism

Prior to the advent of thin-film polarizing filters one relied upon specially arranged prisms of a substance known as Iceland spar. This transparent calcite (primarily sourced from Iceland) has the peculiar property of acting as a double refracting filter. There is a certain amount of speculation that Iceland spar is in fact the old Norse sun-stone of legend that permitted navigation based upon the position of the sun even in cloudy conditions. In any case, the ability of the mineral to polarize light, together with the fact that it cleaves easily into rhombs renders it uniquely suitable for the creation of a various forms of prism, two sorts of which were common in polarized light microscopy.

Invented in 1928 by William Nicol, the prism so designated is composed of two portions of a single crystal of Iceland spar cut at precise angles with respect to the axis of their polarization and cemented back together. Once reassembled in accordance with Nicol’s design the double refracting crystal becomes a filter which effectively reduces any light entering it to a single ray of polarized light. A Nicol prism is easily identified because either end of it will show parallel faces of 68°. That the active faces are at an angle makes the Nicol prism less suitable for use as an analyzer and it will be most often found in a polarizer.

Unlike the Nicol prims, a Glan-Thompson prism has both of its active faces at right angles to the axis of polarization. This simple fact makes it well suited to use in an optical system when one needs to maximize the amount of light which will pass through it, and minimize the distance at which it may be placed conveniently over an optical lens. The Glan-Thompson prism acts in much the same way as the Nicol prism, it simply permits a greater percentage of polarized light to pass through.

Antique Apparatus

Historically polarized light microscopy was practiced much as it is today; with either a petrographic microscope constructed specifically for that use, or a pair of accessories that adapt a standard light microscope to the task. Although the precise configuration of the apparatus took may have varied, it generally took one of two forms depending upon the placement of the analyzer. In each form a polarizer was mounted in place of, or beneath the microscopes condenser. One sort used an analyzer that screwed into the objective end of the microscope body after the objective or nosepiece and so introduced the Nicol prism into the optical axis. The second form fit over the end of the microscopes draw tube so that the Nicol prism is introduced over the ocular at the eye-point with a subsequent lens that focuses appropriately. In either form one of the elements will rotate, polarizer or analyzer.

In nearly all forms the rotating component will be inscribed with markings designating the degree of rotation from 0 too 360. Occasionally, the manufacturer may not provide precise or complete markings. Very often the polarizer and analyzer were sold together in a case as either on its own would be of only limited use. Below is an example of a representative Bausch & Lomb polarizing apparatus from the era of the Triple Alliance (1907 – November 1915) first in its case and then fitted to a Bausch & Lomb BH8 dating to c. 1919.

Bausch & Lomb polarizer (left) and analyzer (right).

Bausch & Lomb polarizer (left) and analyzer (right).

Polarizing apparatus on period appropriate microscope.

Polarizing apparatus on period appropriate microscope.

The black surface will face towards the underside of the microscopes stage in use.

The black surface will face towards the underside of the microscopes stage in use.

The Polarizer

This example, which carries a Nicol prism of Iceland spar friction fit into a cork, is designed to fit into the substage in place of the microscopes condenser. One will be quick to note that this means one should employ the concave mirror in order to obtain appropriately converging light for illumination. Later varieties of the apparatus constructed along the same lines would feature filters composed of selenite with which one could control the color of the polarized light.  Once fitted the condenser adjustment is wracked upwards to bring the Nicol prism as close to the specimen as possible, in this way ensuring the entire field is filled with polarized light.

When mounting a polarizer of this sort (that does not rotate) one should take notice of the orientation of the polarizing prism when placed in position for use. It may be desirable to orient it such that the axis of polarization is not at an odd angle. However one may simply place the polarizer as is convenient and then orient the analyzer.

The Analyzer

The left portion contains no optical components and is little more than a mounting collar.

The left portion contains no optical components and is little more than a mounting collar.

Here, the analyzer being the rotating component, is more complex. Of two portions, the first is fit over the eye-tube of the microscope prior to the placement of an eyepiece and is held in position by a knurled set screw. Once the base portion of the analyzer is fitted to the microscope an eyepiece is inserted and the top portion friction fit into a recess in the unit. Graduated marking around the top portion (which bears the polarizing prism) range from 1 too 360 and show the relative orientation as it is about the optical axis. Due to the limited size of the prism it is not possible to obtain a complete image of the normal field of view with a prism set in a fixed position. For that reason the eyepiece of the polarizer is adjustable in the manner of a draw tube so that an optimum field of view may be had for a given ocular.

The primary advantages of an analyzer of this type are the ease with which the orientation of the analyzer may be read, and the retention of the tube length. Where an analyzer which screws into the body of the microscope between the objective and body tube will add to the overall length of the body tube, this apparatus will not, enabling the markings on the draw tube to be used as normal for coverglass accommodation or other similar adjustments.

Notes:

∗Some of the technical information concerning various varieties of polarizing prims may be found excellently presented in the following pdf available from SPIE, the international society for optics and photonics: PM200.pdf

Cats Whisker Forceps

A recent brush with greatness (see this excellent chap) inspired me to work on a few opaque, dry-cell, mounts. This of course reminded me that I have always lacked a delicate touch. -K

Delicate Objects

When mounting one is apt to run into all manner of materials, from algae too zea stems there is no limit to what one might encounter. While some of the objects to be mounted are simple to manipulate with droppers, section lifters, or brushes, a few require a forceps to be handled effectively. Unfortunately, some of what one may wish to mount is fragile (part of the reason one will want to protect it with a sturdy mount) and the usual forceps will be sure to result in damage unless one is possessed of the most careful hand. There is, of course, specialized equipment for working with small (right down to the truly microscopic) objects; specialized equipment for working with delicate objects; specialized equipment for working with small delicate objects; and it is nearly all difficult to find and expensive.

The Old Solution

The old solution was a simple modification to the common sort of forceps or needle. It proved such a fine remedy to the problem that few who make use of it are unimpressed. In fact, the solution was so elegant that one can still pay (exorbitant prices; $12.00 is usual) for professional equipment making use of the common (wait for it…) eyelash. When a small and delicate specimen had to be manipulated the workers of old would cement an eyelash, for the finest objects, or cats whisker to the usual needle holder or standard forceps and thereby create a more exacting tool without recourse to more expensive instruments.

As a Probe or Pick

If one must manipulate a small object, perhaps pollen or butterfly scales, a straight eyelash bound to a suitable handle will do nicely. It was once (inappropriately enough) thought that lashes from particular genders or ethnicities were superior and catalogs often boasted about the origin of their offerings as being more gracefully curved or uniformly black. Todays suppliers are rather ambiguous as to the source of their offerings and the eyelashes themselves may be human or otherwise. If one takes any comfortable handle, and cleans of oil with a solvent (alcohol-ether 50% would have been traditional) an eyelash, it may be fixed to that handle by a drop of balsam or a few wraps of thread. Such a tool comes to a very fine point that is surprisingly resilient, easily visible, and not prone to breaking, This last point rather important as any who have wade use to the thread of glass micro-manipulators may attest.

As a Forceps

For a larger object an eyelash may prove insufficient when fixed to the end of a dime-store forceps, and that is where a certain degree of preference comes in. Some historic texts make reference to using the bristles of a pig or hair from the white-tailed deer. For a modern worker those materials may prove difficult to come by. One might instead give their floors a sweep and recover a whisker or two from the family cat. Cutting away the very fine half nearest the tip, set it aside for use as with an eyelash, one should then affix the more robust end to a convenient forceps.

Such a tool at times seems to work wonders, as objects may now be grasped without fear of crushing. In truth one would be hard pressed to hold an object so tightly with such a device as to cause damage. Simultaneously, one may be assured of a sound grip. Considering the price of similarly fine ready-made forceps, the result is better than might be otherwise possible.

Modern Acessories for Vintage Stands

Partial as I am to Bausch & Lomb I’m not one to neglect opportunity when it comes along. -K

One great trouble of the amateur microscopist is that economics often dictate the equipment one works with. This is apt to be a vintage or downright antique microscope and the accessories associated with such a microscope are available only rarely. That rarity does not translate to economy. Naturally, occasions come about when some piece of apparatus might be found inexpensively and in working condition; otherwise one is left with little choice than to make their own accessories, which can be enjoyable but is not always practical.

Recently I came upon an individual who produces a limited range of modern accessories for a number of redly available microscopes from a variety of manufacturers. One of the items is a polarizer and analyzer designed for use with the American Optical 60. Being possessed of one and a bit of disposable income, I purchased the device and it arrived today.

The analyzer appears to be composed of a portion of polarizing film in an aluminum frame. Not in and of itself particularly special but it is very convenient having a nicely mounted bit of film in a frame of just the right size. It is recommended that the analyzer be placed in the body of the microscope below the angled eyepiece tube. Placing the analyzer thusly dispenses with the difficulty of using an eyepiece mounted analyzer, and the tendency of such to be accidentally rotated.

The polarizer is composed of a similar filter, of the sort available for digital cameras, mounted in a specialty holder that fits over the sub-stage lamp. It’s particularly nice that the filter is of a type so easily replaced, for although the analyzer may be left safely within the body of the microscope, the polarizer is apt to become damaged at some point. So long as the housing is in good shape a new polarizing filter may be placed on it at any time. The housing on which the filter is mounted is perfectly constructed to elevate the filter over the profoundly convex lens of the illuminator.

Testing the apparatus shows that it is of suitable quality, better (as well made modern polarizing films are) than the traditional Nicol prisms. Overall it is very nice, worth the expense certainly and gratifying in use, particularly as it has the very tailored feel of being made by one who possesses the exact model for which it has been constructed. I’ve resisted the urge to post pictures and include links, but suffice it to say the set may be found on eBay.