An AO Spencer  Objectives Reference

Using the various available manuals and catalogs it is possible to construct a reference of Cat #'s (Catalog Numbers) and Objectives that may be useful in finding objectives for your AO Spencer microscope.   

The rules for objectives:

Eyepieces, on the other hand, are quite forgiving can be used interchangeably on 160mm TL and Infinity corrected scopes with good results.*  

*Note: The 'purist' in me wants to note that the very best, optimum results will be obtained by using the eyepieces specifically  made for each objective set (e.g.  a Cat# 146 10x eyepiece on a 160mm TL Series 2 scope, a Cat# 176 10X eyepiece on an infinitely corrected Series 10 scope, etc.) -- but the 'practical side' of me says it really, truly doesn't make a heck of a lot of difference -- use what you have.  But if you are wondering what the differences might be between different brands of eyepieces, Mervhob of Yahoo's Microscope Group has furnished the useful information below:

You can see that B&L (Bausch & Lomb) eyepiece are very close to the same specifications as AO eyepieces.  It is quite common to find B&L eyepieces on AO scopes and, probably, vice-versa.  Amazingly, you'll often find B&L objectives on AO scopes, without an shims, even though their parfocal distance is 35.6mm vs. the 34mm distance for AO Objectives.

Note:  Tom Woods contributed a guide to the darkfield condensers and funnel stops that may be useful to you if you explore darkfield with AO objectives.

OK, Here is a list of the AO and Spencer Objectives 'known' to me from either experience, or from the AO Spencer Literature (i.e. a catalog or a manual).  (Note: You can select the whole list, top to bottom, and past it into Excel to create a spreadsheet that can be sorted on any column if you'd like)

Sources:

 Note: A 'C' at the beginning of the Cat#, at least in the Series 15 and 35 era (1930's and 40's), meant 'C'oated.  For example, you could order either a Cat# 115 uncoated 43x objective, or a Cat# C115 coated (Americote) objective.  A 'K' at the beginning of a Cat# designated a 'special order' item.

Tom Woods writes: 

"Here is a scan (pdf) of objectives AO was listing in the 1941, 1949, 1954, and 1958 versions of their 'Effective Use and Proper Care of the Microscope' manuals.  There are some really interesting objectives listed that I didn't even know existed."

*In the only case I know of, AO, strangely, reused a Catalog number.  In 1969, the Cat# 1029 was clearly a 50x (without a iris diaphragm).  Then sometime later AO brought out a Cat# 1029 100x Oil ( I've seen three examples of these -- they were 'new style' objectives so I would guess the 1029 was maybe produced in 1975 or 1976?) 

Tom Woods writes:  "I recently came across this AO objective, Cat. 1127, 97X infinity corrected, pics attached. On your website the Cat. 1127 is a 10X advanced plan achro infinity corrected objective (new style) with an N.A. of 0.25. This seems to be yet another example of AO's re-use of an objective Cat. number. Have you ever seen this one before? I can only guess that this must have been one of the very first high powered oil immersion objectives offered with the newly released AO Series 10. A bit later these objectives became 100X with different Cat. numbers (e.g., 1079).

The Cat# 1228 50x Oil, Dark Phase doesn't appear in any catalog Tom Woods or I have access to.   But, Tom discovered it on eBay as part of a group of objectives being offered for sale.

**Unsure if this whole number is the Cat#.  Only have seen on example of this objective, but this is what was on it:

Stan Ayers -- "I just bought a phase-contrast microscope. It seems to be from the '50's. The objectives and condenser turret are familiar, except for one. There's a 50x reflecting objective, marked 922968. I have never seen one of these, and was wondering what they are for, or why they were specified."

Needham's 'Practical Use of the Microscope' p.137: "A recent computation is that of the American Optical Company.  The reflecting objective is 50x with an N.A. of 0.56.  The quartz optics made by this Company for the objective are a 10x Huygens eyepiece and an Abbe substage condenser."  Read the full account here.

***The catalog says N.A. 0.80, but I've seen, on ebay, an example that clearly says 0.85 

**** Tom Woods shares:

***** Mitchell Nuhn found a plan version of a Cat# 1075 4x on eBay.  It seems that as AO transitioned from 'Achro' to 'Plan Achro' objectives for the Series 10 (which appears to have happened between 1969 and 1974) they didn't immediately change the Cat numbers to reflect the upgrade.

Phil Mathewson also shares this: "I thought I would pass on an observation about those versions of the #1075 and 1076 objectives that show up on ebay every now and then with plan achro engraved on the barrel. I never owned one but I disassembled a #1076 ( non plan achro version)and a #1019 and the two objectives are identical internally. They just have different barrels. In testing them, they performed identically too, with not quite fully plan performance to the periphery of the 19mm field of a #176 eyepiece. Even the contrast was the same, although later #1019 examples might have some improved coatings.

There was a lot of pressure on companies in the 60's to compete with a plan objective system and AO probably looked at what they had in the standard 1075, 1076, 1077 ,1078 and 1079 series and felt that the two lower magnifications were so close as to be good enough until such time as they could devote the resources to replace them. There were no real standards for planarity at the time, nor are there now. They then re-released those two in the planachro series 1017, 1019, 1022, 1023 and 1024 in the late 60's in new barrels. The first to go eventually was the 1019, replaced by the far superior #1021 and note that they left a place for it in their numbering scheme at the very beginning, so it was a planned evolution. They never really got around to designing a 4X #1018, which they also left space for, instead after they committed to 45mm parfocal, adding an economical but serviceable group of replacement 34mm parfocal objectives #1026, 1128 and 1129 that could be made using fewer elements due to the availability of improved glass formulas. The 1129 for instance, outperforms the #1024 100X but could be made more cheaply. AO did leave places in numbering schemes for later additions. When they developed the 1700 series planachro objectives, they moved the 50X .80 oil objective into the Neoplan series and left a space in the numbering scheme of the plannachros for a 60X, never to be offered for obvious reasons."

The discussion about those strange Austrian AO Plan Achros should be clearer now. Those objectives were made in a production run for the Neovar and Buffalo likely needed extra stock, so it made economic sense to add some to the Austrian production run with a spacer installed instead of a spring.

There were also Cat.# 1022, 1023, and 1024 objectives made very early in the Plan Achro production that were in those thin barrels with 7 color code rings. The only obvious physical difference between them and the
achromats is with the 1023 and 1024 -- there is a chamfer around the bottom edge instead of a cove. The early Plan Achro 10X was the cat. # 1076, marked as such in later production. In fact, when they introduced the fat barrel Plan Achros, the 1076 was just put in a new barrel and given a new number, 1019. You can disassemble each and swap the lenses. Exactly the same planarity and w.d. Possibly the later 1019 production had better coatings.

FAQ Question:  Can I use other manufacturer's 160mm T.L. objectives with my 160mm T.L. AO Objectives?

Answer:  Sure . . . for almost 100 years, people have been happily exchanging 160mm objectives  But, there could be a few 'gotchas'.  First, color and flatness correction sometimes occur in an intermediate lens (e.g. some B&L designs) or, more commonly, in the eyepiece.  But you have a good chance of being successful without any loss of resolution and contrast.

Also, remember the parfocal distance challenge.  Sometimes, if the difference isn't too great, you can use shims between objective and nosepiece to defeat this challenge (e.g. see here -- for an assorted parfocal rings kie).  

A very useful table of parfocal distances is found in Mikrofibel page 55 -- 1st column = Manufacturer, 2nd column = tubelength, and the 3rd column = parfocal distance in mm -- which is what you need to know.  Can't read German?  Me neither, but 'mining' this document we can produce a table of good candidates as below:

FAQ Question:  Can I use other manufacturer's infinity corrected objectives with my infinity corrected AO Objectives?

Answer:  Not like you can 160mm objectives -- in theory, many advise against it.  But when did that ever stop you? :-)  After a rousing discussion on Yahoo's Microscope group about this, and reading various references, I have concluded (with not much authority I might add :-)  ) that it may work, or it may not work, depending on which objectives and which scopes you use them on.  A very good reference, and read, is: 

http://www.microscopyu.com/articles/optics/cfintro.html

that addresses the history and issues well.  

Basically, bottom line, even an infinity system is designed with a tube-length in mind for the upper part of its optical train, which varies by manufacturer, and the design 'mismatch' can cause trouble when mixing various makes of infinity corrected objectives.   The issue comes down to the question: "How can a single objective cost $4000?",  with the answer:  "Because there's a lot to correct for in attaining the ultimate resolution.")

But theory is one thing, practice is another.  In practice, people have found that it is often possible to swap infinity corrected objectives without appreciable, or at least, noticeable, loss of resolution and contrast.   Remember though you will still face the parfocal distance challenge mentioned above.

Be sure to see Phil Mathewson's findings on compatibility of infinity corrected AO and Reichert objectives and eyepieces here.

FAQ Question:  Can I use Leitz 170mm T.L. lenses on my 160mm T.L. AO Scope? 

Answer:  Sure.  The Parfocal distance problem will be there (i.e. many Leitz lenses are 45mm parfocal, some are 37mm parfocal, etc.****), but it will work.  The definitive document on this is Leitz-160mm-Memo.pdf  at Gordon's site -- a very interesting read.

* Note: Determining the parfocal distance of an AO objective is not as easy as it sounds -- well accurately at least.  I have two LOMO 160mm T.L. objectives which are very clearly stated by the manufacturer to be 33mm parfocal.  Using the 1 micron graduated fine focus on the Series 4 scope, I found these LOMO objectives to be within 0.065mm parfocal to each other.  I then used them to compare against same power AO 160mm T.L objectives (which are within 0.040 mm parfocal to each other) and found the AO's parfocal distance to be almost exactly 1.0mm longer than the two LOMOs (0.925 mm in one case,  1.030 mm in the other).  So using the two Russian objectives as a standard (well, it was the best I had), I compute the AO Objective's parfocal distance to be 34mm.

**Note:  I compared an AO 97x Oil objective to a B&L 97x Oil objective -- both gave excellent images (by the way, the 97x AO was exactly parfocal with the 10x AO objective noted in the LOMO comparison above).  The B&L parfocal distance was exactly 1.67mm longer than the AO's distance.  Thus 34 + 1.67 = a 35.67mm parfocal distance for B&L objectives.  One message on the Yahoo's Microscope forum says that B&L objectives are 35.5mm parfocal, but that is 0.17mm too short per my measurements.

***Note:  Quoting from Needham (1958 -- The Practical Use of the Microscope, p. 153):  "American Optical Company (Spencer) has designed objectives in which the central beam is not changed while the diffracted light is both retarded and reduced in intensity.  This modification has been named by them, B minus contrast.  American Optical manufactures a very complete series of phase-contrast objectives for bright, dark, and B minus contrast, each with three degrees of contrast of low, medium, and high . . . The consensus of opinion of several of the foremost independent workers with the phase-contrast microscope is that the Zernike, 1/4 (lambda) retardation, negative (bright) contrast or positive (dark) contrast is preferred for the great majority of objects with very little contrast.  Also they object to the fact that too many variations in phase-contrast objectives complicate and confuse the beginner in this field, and that such modifications are not generally necessary, and that they add greatly to the cost."

****Note:  Leitz objectives are a tough one to unravel.  Older Leitz objectives (before 1960?) seem to be all 37mm parfocal.  But when Leitz brought out PL (plan) and NPL (neo plan) objectives, they designed them  with the longer 45mm parfocal design.  But, unfortunately, it turns out to be no that simple.  Note Mike Andre's comment to a question about availability of 170mm T.L 37mm Phaco or PV objectives -- Yahoo Microcope forum message #33059:

"Re: Looking for a Leitz Phaco or PV objectives -- 170mm T.L. , non-plan

Hello all,

Looking at my copy of the Leitz manual "Image-forming and Illuminating Systems of the Microscope"***** it states on page 49: Phaco phase contrast objective for the Zernike condenser are 170/0.17/45mm (with the exception of the Fl Oel 70 - 170/0.17/37mm)

Page 50 lists the Phaco NPL Phase Contrast Planachromats for the Zernike condenser at 170/0.17/45mm, but page 51 lists PV Phase contrast objectives for the Heine condenser at 170/0.17/37mm (with three exceptions for 170/0.17/38.5mm!)

I have sets of the achromat phacos as well as the NPL Phacos, all or which are 45mm (none for sale, I'm afraid!)

Hope this helps.

All the best, Mike"

***** Don Grybeck kindly has contributed this wonderful document, which was subsequently scanned, and you can download it here:  "Image-forming and Illuminating of the Microscope -- objectives, eyepieces, and condensers" (23.4 MB zipped file)   

Phil Mathewson writes:

"I see that Tom Woods passed the early series 10 manual on, that I did at the library. He mentions that the #1078 objective was considered to be particularly suited to haemocytometer use. I'm not sure that was the case. The 1075,76,77,78 and 79 objectives appear to have been developed as the first set for the 10. The working distance of the 1078 is .5mm.

The cover glass of a haemocytometer is .4mm. The objective itself would have a cover slip correction of .17. Given that it's N.A. is .66, that extra .23mm would have some negative effect on the image. It is likely that AO released the full set of coordinated objectives, putting the 1078 forward for haemocytometer use but very quickly designed and released the # 1116, which has a w.d. of .7 and a much broader tolerance of cover glass thickness. The 1116 shows up in the next catalogue I have access to as an add on objective, to the 5 already present. A 5 objective set, then a duplicate 45X .66 with a slightly longer w.d. Glass batch differentials would have precluded that the 1078 might get mfg. with a less than .5mm w.d. plus photomicrography demands might lower the w.d. to close to .4, so it was likely not regarded as the best candidate for the haemocytometer.

Also:

"A very odd series 4 phase objective arrived on a stand from late 1961 the other day.  I see it listed nowhere that I have access to, which is your compiled list and my list from the spring of 1948, just after they switched from marking the objectives with wavelenth and annular thickness to bright, dark and medium ,low etc.

 That catalogue entitled Spencer Phase Microscopes, from July 1948 has a few inclusions beyond your comprehensive list.

 Cat. # 3110127W   1.8mm oil imm. 97X Bright Contrast-Low,0.05 lambda 1.25

 Cat. # 3130108W  16 mm 10X Bright Contrast-Low,0.33 lambda 0.25  Cat. # 3420108W  16 mm 10X B-Minus Contrast High 0.25  Those were probably discontinued shortly after because they do not show up in the 1950 list.

The newly arrived objective was included in  a stand that also carried a 20X Dark M and 97X Dark M, two very ubiquitous objectives. The 43X however is a Dark H. I have never seen a Dark H objective of any kind. It is coated and has the annular diaphragm matching # 4834 on it, something that seems to have begun after the 2/4 was launched. It is likely a later addition but in your late series 2/4 phase catalogue from Jan. 1962, they seemed to have reduced the versions available dramatically, to medium , dark and bright only, something they carried through to the series 10, although they did also add in the one B-Minus offering.    If you decide to include it in your compiled list, following the nomenclature codes they used, it would most likely have the following cat. # 1220115W.

Back to the P.S. Neeley AO Spencer Microscope Page

The images, articles, and concepts of this page are copyrighted by P.S. Neeley -- copyright 2005