Hi I have built ofm v6 with a 20X objective and cannot get it to focus. The Z motor is working but doesn’t appear to be moving the flexure at all into focus, Perhaps I am very far out but does change if I use the manual z control. Open to any ideas for what to look at? Objective is 45mm so I have a 10mm riser on the plate, thanks for your help. Im not a scientist just a hobbyist!
Hi @Twalsh995. When you say that the focus does change when you use manual control, do you mean that you remove the motor and turn the large gear by hand? Can you get a good focus doing that?
A couple of pictures of the microscope from the front and the back would also be very helpful to try to work out what is happening.
Hi @WilliamW,
Thanks for your response. No when I remove the motor and turn manually there is no improvement I can visually see.
I suspect I have another issue as the 10mm spacer for the 45mm parafocal lense is far too much. 7ish appears to be better but without the fine adjustment I cannot confirm. (These are the blue shims on the scope)
I also have some photos of a red marker line
The v7 microscope shouldn’t need a riser for a 45mm parfocal objective. Do you have photos of the markings on your objective. I wonder if something else is the issue.
As @Julian says, that body is v7 not v6. It is one of the beta releases, but not the latest v7.0.0-beta5.
It should not need a riser for a 45mm par focal length lens, because that is now built into the stage top. A 20x lens usually has a working distance of about 1mm between the lens and the sample. In the picture that is from above, yours seems to be much further away. It would be very useful to see the lens markings.
You have not got the microscope on the stand, and the way in which it us positioned on your box looks as though the microscope feet are not installed. The o-ring bands and the feet are a vital part of the mechanism. If you go back to this step Assembly Instructions does it all seem to be in place? - the link is for the latest release, but the steps are the same for all v7.0.0-beta versions.
@WilliamW @j.stirling please see photos of lense. Should be 45mm from my research
Yes the feet are installed with the bands, on closer inspection it looks like the oring on the Z is perishing. So that might be my fine z issue.
thanks for the help
That has all of the normal markings. The par-focal distance and working distance are nnot marked, which unfortunately is normal. If it is this lens: MA697 BF Semi Plan Phase Achromat (Zernike Type) S20X Objective – Meiji Techno America it states a working distance of 3.1mm. That is relatively long. Is the physical length of the lens 41.9mm from the mounting shoulder to the lens? (45-3.1mm).
I would try adjusting the focus by hand to set the lens top about 3mm below the stage (without risers).
- If the z-axis will not move that far then it is either not this lens, or the lens is not 45mm par-focal.
- if it does not get as far as 3mm, or 3mm is right at the bottom of travel, but you find that the centre of z-travel is at about 1mm below the stage then it coukd be a different lens with a more usual working distance of ~1mm for 20x.
- If you reach 1mm or 3mm, are you able to focus the sample?
If you cannot focus, or the focus position is more than 3.5mm from the face of the lens, then there is another problem in the optics module, either the tube lens that you have used, or the optics module version that you used. edit: it would not be the optics module. You have a finite conjugates objective, the focus would be moved closer if you used the ‘infinity’ version of the optics module. You see the focus too far away.
Have you attempted to invert the cover slip towards the objective?
@Ertan @j.stirling yes I have tried inverting the coverslip. No success.
@WilliamW the focus is still much higher than the stage. Approx 7mm from stage, maybe the objective is 3mm below the stage to make 10mm? I’m going to print 6,7,8,9,10mm spacers to confirm
Regardless I agree the objective is 45mm so Im really not sure! Would I have the lense in the tube the wrong way around?
However, It appears the the Z is not moving at all by hand (looking at the flexure feature from the underside), i am going to reprint the main_body and do a new assembly.
(I removed the “box” I had it sitting on to ensure the feet weren’t interfered with. Replaced the orings on Z. )
The direction of the tube lens will make a small difference in image quality but shouldn’t make a significant difference to the focus position.
Do you have a link to the lens that you purchased for the tube lens?
@j.stirling https://ebay.io/m/RNOulE this link should work.
Julian was referring to the f=50mm tube lens that is in the optics module.
In step 2 Assembly Instructions
@WilliamW @j.stirling my apolgoies, I believe this is it Half inch diameter (12.7mm) focal length 50mm Achromatic lens visible antireflection film - AliExpress 1420
That looks to be correct. So your problem is still confusing.
A couple of measurements would be useful:
Distance from the shoulder of the objective (where it meets against the optics module) to the top. I don’t think this is the problem, but useful to know.
Distance from the top of the lens to the position where it is focused, you gave as 10mm. This is a lot more than the specified 3.1mm, and indicates a problem with the optics module or tube lens.
The next measurements will mean taking the Optics module out and removing the camera:
What is the length of the optics module, from the mating surface for the objective to the camera mounting surface?
Finally, point the objective lens end of the optics module at a bright scene out of the window (without the objective lens fitted). Place a piece of paper close to the camera mount end of the optics module. If you move the paper nearer and further from the optics module, you should be able to see an image of the far away scene. How far is that focus beyond the camera mount? It should be a couple of millimetres. This is testing the optical properties of the tube lens.
@WilliamW so abit of work over the weekend.
As you mentioned I removed the x20 objective as I could never get into focus and just tied to focus using the tube lens without objective, I could get into focus maybe 10-15mm above the tube. So I swapped out to another x40 I had and that didnt have any issues getting to focus at approx. 1mm above the stage.
Does this point to an issue with the objective then? It is a shame as x40 is too powerful for what I wanted! What could be the matter?
If not I will rebuilt the tube lense, maybe the objective had not threaded correctly.
I never got the x20 into focus
Rebuilt without the motors also, I think simpler is better for me!
With the 40× lens how far was the sample from the lens when it was in focus? Are you saying it is more than 1mm?
For the test without any objective lens, were you using the camera, and finding a focused image of an object 10-15 mm from the end of the optics module, where the lens should be? Or had you removed the camera and a distant objevt was imaged 10-15mm from where the camera should be?
Yes the sample was in focus at about 1mm from the objective to the actual printed stage itself, I think this is correct for focus from what I have read from you above
I removed the objective and put the slide where the objective should be, imaging through the pi cam, tube lense at the end of the tube and this was roughly 10-15mm away from the thread of the tube lense
This is now very confusing indeed. I shall need to post some diagrams to be sure that I understand what measurements you have made.
What is the 40× lens that you are using? Normally they have a much shorter working distance, less than 0.5mm. It is 20× that are usually around 1mm (but the one that you have specifies 3mm).
