A small tip for users of Bausch & Lomb.

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apochronaut
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A small tip for users of Bausch & Lomb.

#1 Post by apochronaut » Tue Feb 23, 2021 2:57 am

I posted this way back but at the time, there was relatively little interest in Bausch & Lomb . That has picked up some, so I am reposting . This design feature is easy to overlook when using a B & L microscope. I did for a while but had a " how clever" moment.
Beginning with the broad 1926 patent date emblazoned on objectives made after that date and continueing right through the early Flat Field designs , B & L had a unique parfocalizing system. I don't know if any other objective designs utilized a similar system but the B & L system is fantastic. If others did too, then they are fantastic as well. With the introduction of the planachromat and planfluorite objectives in the mid-70's , the functionality stayed the same but the design was modified to adapt to the more slender spring loaded barrels.

From 1926 on most B & L objective barrels are adjustable for parfocality. The concept involves the objective sliding up and down in an outer shroud or sleeve like a piston in a cylinder. Since the " cylinder" or shroud contains the objective thread, the actual objective can be adjusted up or down and perfectly matched in parfocality to the other objectives in the nosepiece.
Adjustment is quite simple but the increments of adjustment quite fine, so precision is required. However, once adjusted, that's it.

The external shroud of B & L objectives is a lower external sleeve that unthreads from the objective housing. Integral to it is a port in it's nose or bottom that fits over the front lens housing against a shoulder, and applies pressure against the objective lens column when tightened. At the back of the objective is a diaphragm ring that is threaded into the objective barrel applying pressure against the objective lens column from the rear. By loosening and tightening those two threaded retaining devices, the entire objective can be lowered or raised in it's shroud, relative to the nosepiece and in this way, all of the objectives can be made perfectly parfocal.

The Planachromat and planfluorite objectives have a parfocalizing cam, which raises and lowers the objective lens column. There is a small screw in the side of the objective that adjusts the cam.

Placozoa
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Re: A small tip for users of Bausch & Lomb.

#2 Post by Placozoa » Tue Feb 23, 2021 3:08 am

My objectives do this too but I dont have a B&L. Just had to unscrew the outer sleeve of the objective and I spotted this feature and used it 2 weeks or so after getting my first scope. Good thing for everyone to check, maybe. ;)

BramHuntingNematodes
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Re: A small tip for users of Bausch & Lomb.

#3 Post by BramHuntingNematodes » Tue Feb 23, 2021 4:38 am

Thanks for bringing this up again apo. I recall you mentioning some time back, and I have an objective that could really use some adjusting.
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

hans
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Re: A small tip for users of Bausch & Lomb.

#4 Post by hans » Tue Feb 23, 2021 4:54 am

Yeah, thanks, this is good to know. I carefully removed the lower shrouds (one was already loose when I got the microscope) when cleaning but didn't go any further.

Now the 10X Huygens eyepieces... how long does it take to get used to these? The short eye relief is actually not nearly as uncomfortable as had I imagined except that I have not managed to go more than a couple minutes without blinking reflexively and smearing my greasy eyelashes all over the lenses.

BramHuntingNematodes
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Re: A small tip for users of Bausch & Lomb.

#5 Post by BramHuntingNematodes » Tue Feb 23, 2021 5:05 am

The eyelash problem never goes away!
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

apochronaut
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Re: A small tip for users of Bausch & Lomb.

#6 Post by apochronaut » Tue Feb 23, 2021 12:49 pm

hans wrote:
Tue Feb 23, 2021 4:54 am
Yeah, thanks, this is good to know. I carefully removed the lower shrouds (one was already loose when I got the microscope) when cleaning but didn't go any further.

Now the 10X Huygens eyepieces... how long does it take to get used to these? The short eye relief is actually not nearly as uncomfortable as had I imagined except that I have not managed to go more than a couple minutes without blinking reflexively and smearing my greasy eyelashes all over the lenses.
The Huygens designs in the case of many companies were the basic default. Wider field designs with more eye relief were an option and most companies had high eye relief eyepieces for those wearing glasses.
I did some repair for vet clinics. Off and on the repair entailed cleaning off caked on mascara from the eyepieces.
The eye relief varies with various Huygens designs too. It's never great but some are better than others and they are pretty much a universal eyeiece, so from that standpoint, Huygens rise above the pack. Spencer made particularly good ones, recognized in this micscape article.
http://www.microscopy-uk.org.uk/mag/ind ... ieces.html
Paul James' "no name optics" he loves so much, are in fact Spencer 10X made from about 1932 until into the 60's.

hans
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Re: A small tip for users of Bausch & Lomb.

#7 Post by hans » Thu Feb 25, 2021 5:18 am

apochronaut wrote:
Tue Feb 23, 2021 12:49 pm
Off and on the repair entailed cleaning off caked on mascara from the eyepieces.
So they put in these fine ridges to scrape off and collect the mascara before it makes it to the lens...?
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apochronaut
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Re: A small tip for users of Bausch & Lomb.

#8 Post by apochronaut » Thu Feb 25, 2021 2:42 pm

Yes. That is the B & L mascara moat. First patented on Oct. 13 1926 along with various other optical concepts.
If you reference back to the micscape article, you will see that Spencer had a slightly different idea ,as always. Where B & L had divisible objectives, Spencer had separable objectives. B & L had hyperplane eyepieces; Spencer , planoscopic.
In the case of the mascara moat, the Spencer design with it's steeply sloping sides adjacent to the eyelens , allows the mascara to just fall away from the eyelens rather than get trapped in a moat.

hans
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Re: A small tip for users of Bausch & Lomb.

#9 Post by hans » Wed Mar 31, 2021 6:59 pm

Just came across this while looking at condenser patents:
Hence, the series of objectives may be parfocalized by adjusting the optical system of each objective with respect to the shoulder 12. This parfocalizing adjustment can be readily effected, in my improved objective, by relative adjustments of the nut 25 and the threaded tube or casing 21. Such a means for effecting a parfocal adjustment greatly facilitates and cheapens the manufacture of objectives.
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apochronaut
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Re: A small tip for users of Bausch & Lomb.

#10 Post by apochronaut » Wed Mar 31, 2021 7:17 pm

Nice find. n Great system. They finally abandoned it in about 1975, when they introduced spring loaded objectives, which are parfocalized by rotating the cam against the spring.

jeffery163
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Re: A small tip for users of Bausch & Lomb.

#11 Post by jeffery163 » Tue Apr 06, 2021 6:17 pm

apochronaut wrote:
Tue Feb 23, 2021 2:57 am
I posted this way back but at the time, there was relatively little interest in Bausch & Lomb . That has picked up some, so I am reposting . This design feature is easy to overlook when using a B & L microscope. I did for a while but had a " how clever" moment.
Beginning with the broad 1926 patent date emblazoned on objectives made after that date and continueing right through the early Flat Field designs , B & L had a unique parfocalizing system. I don't know if any other objective designs utilized a similar system but the B & L system is fantastic. If others did too, then they are fantastic as well. With the introduction of the planachromat and planfluorite objectives in the mid-70's , the functionality stayed the same but the design was modified to adapt to the more slender spring loaded barrels.

From 1926 on most B & L objective barrels are adjustable for parfocality. The concept involves the objective sliding up and down in an outer shroud or sleeve like a piston in a cylinder. Since the " cylinder" or shroud contains the objective thread, the actual objective can be adjusted up or down and perfectly matched in parfocality to the other objectives in the nosepiece.
Adjustment is quite simple but the increments of adjustment quite fine, so precision is required. However, once adjusted, that's it.

The external shroud of B & L objectives is a lower external sleeve that unthreads from the objective housing. Integral to it is a port in it's nose or bottom that fits over the front lens housing against a shoulder, and applies pressure against the objective lens column when tightened. At the back of the objective is a diaphragm ring that is threaded into the objective barrel applying pressure against the objective lens column from the rear. By loosening and tightening those two threaded retaining devices, the entire objective can be lowered or raised in it's shroud, relative to the nosepiece and in this way, all of the objectives can be made perfectly parfocal.

The Planachromat and planfluorite objectives have a parfocalizing cam, which raises and lowers the objective lens column. There is a small screw in the side of the objective that adjusts the cam.
Thanks for putting it up

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