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Question for Olympus BHT with side port on head

 
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Linden.g



Joined: 06 Apr 2009
Posts: 346
Location: PA USA

PostPosted: Wed Feb 28, 2018 6:22 pm    Post subject: Question for Olympus BHT with side port on head Reply with quote

I've just acquired an Olympus BHT which has a side port above the viewing head. The image can be directed to this port via a rotating knob on the back. The port contains what looks like a photo eyepiece. The port has an internal diameter of about 49 mm. Does anyone know what this head is called and what the port is used for?

The scope also has a magnification changer. It has two large dials, one changes the magnification and also has a marking of PH which appears to let you focus on the back side of the objective. What is the function of the PH setting and what is the purpose of the other dial which adjusts the focus?

Thank you for the advice.


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Pau
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Joined: 20 Jan 2010
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Location: Valencia, Spain

PostPosted: Thu Mar 01, 2018 1:47 am    Post subject: Reply with quote

Quote:
What is the function of the PH setting and what is the purpose of the other dial which adjusts the focus?


This is a Bertrand lens, and as you've discovered it's to focus on the rear focal plane of the objective, the focus ring is for focusing the Bertrand lens. It's labeled Ph because one of its utilities is for setting phase contrast, although it's also very useful to set Köhler, DIC and other contrast methods and also to inspect the lenses of the optical train. In mineralogy and crystallography it's used to see the interference figures to investigate the optical sign of minerals (uniaxial - biaxial) as it provides conoscopic image.
In short, it does the same than a telescope eyepiece but in a much more comfortable way.

The lateral port could be to put a second camera or a part of a drawing device.
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75RR



Joined: 22 May 2014
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PostPosted: Thu Mar 01, 2018 2:32 am    Post subject: Reply with quote

Just in case you have not come across this site before.
Olympus manuals galore!

http://www.alanwood.net/photography/olympus/microscopes.html
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Alan Wood



Joined: 29 Dec 2010
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PostPosted: Thu Mar 01, 2018 6:42 am    Post subject: Reply with quote

Olympus did make a tetranocular head for the BH-2 with a 35mm camera port and a C-mount, but your head is not like this.

That side port does not look like a genuine Olympus part, and I don't think internal 49mm diameter is a standard Olympus fitting.

As Pau said, it might be for a drawing attachment or a second camera. You would need to experiment to see where it forms an image and if you can position the sensor in a camera at that location.

Alan Wood
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Linden.g



Joined: 06 Apr 2009
Posts: 346
Location: PA USA

PostPosted: Thu Mar 01, 2018 3:01 pm    Post subject: Reply with quote

Thanks you all for the information.

Alan, I took a closer look, the divert section above the head is Olympus and it contains an optical flat which sends the image to the side port. I can see that the divert section has been mounted through the head which has been drilled. The side port looks like its bespoke and contains a NFK 2.5, so should form a typical image on a camera sensor. Someone went to a lot of trouble to make the modification. I'm not sure why you would need create two images at the same time. Curious.
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