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Bertrand lens unfocused on objectives other than 4x, is that ok?
Posted: Sat Dec 23, 2023 6:31 pm
by Topcode
So I recently obtained a Diaphot TMD, with 4 objectives, 3 of which are phase (4x PhL, 10x Ph1, 20x Ph2). The Diaphot is great in that it has built in Bertrand lens, it is well focused on the low power 4x PhL objevctive, but totally blurred on any of the other objectives. This is what the 4x objective shows using the Bertrand lens.
Is it sufficient to only center on the low power objective?
Re: Bertrand lens unfocused on objectives other than 4x, is that ok?
Posted: Sat Dec 23, 2023 7:35 pm
by PeteM
There should be some method of focusing the Bertrand lens - not sure what it is on a TMD. You do what to center each phase ring individually.
Re: Bertrand lens unfocused on objectives other than 4x, is that ok?
Posted: Sat Dec 23, 2023 7:43 pm
by Topcode
PeteM wrote: ↑Sat Dec 23, 2023 7:35 pm
There should be some method of focusing the Bertrand lens - not sure what it is on a TMD. You do what to center each phase ring individually.
There is a small knob on the turret with the Bertrand lens, but it barely moves and appears to have little or no impact on the image, it could just be broken or stuck.
Re: Bertrand lens unfocused on objectives other than 4x, is that ok?
Posted: Sun Dec 24, 2023 1:21 am
by macnmotion
My TMD has a lever, not a knob.
Re: Bertrand lens unfocused on objectives other than 4x, is that ok?
Posted: Sun Dec 24, 2023 1:57 am
by Topcode
macnmotion wrote: ↑Sun Dec 24, 2023 1:21 am
My TMD has a lever, not a knob.
Really? This is what mine has, unless I'm looking in the wrong place, but I dont see anything else on the body that could be it.
Re: Bertrand lens unfocused on objectives other than 4x, is that ok?
Posted: Sun Dec 24, 2023 4:22 am
by macnmotion
This is mine. Similar to yours I guess, but with a lever attachment that is used to turn it. Mine moves smoothly throughout its range.
- bertrand lever.jpg (76.72 KiB) Viewed 3106 times
Re: Bertrand lens unfocused on objectives other than 4x, is that ok?
Posted: Sun Dec 24, 2023 4:29 am
by Topcode
I see, mine only makes about 1/8th a turn, so I guess thats probably broken... yay!
I'm also now noticing a small clicking noise when turning it, thats probably not a good sign either.
Re: Bertrand lens unfocused on objectives other than 4x, is that ok?
Posted: Sun Dec 24, 2023 5:30 am
by macnmotion
Topcode wrote: ↑Sun Dec 24, 2023 4:29 am
I see, mine only makes about 1/8th a turn, so I guess thats probably broken... yay!
I'm also now noticing a small clicking noise when turning it, thats probably not a good sign either.
Mine only moves about 1/8 of a turn as well.