Ability to change the Objective Lens

I have been thinking about building this project (not sure between the Delta stage or the regular build, and also not sure about infinity optics or just the regular 50mm optics). The main question I have is about the ability to easily swap out the objective lens for different magnifications. All of the scopes that I generally see have some capability to easily swap out the objective with out moving the sample or the stage? Is this a possibility with OpenFlexure? Has somebody tried to implement this?

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The Openflexure microscope is really designed to be used for a single purpose. You can remove an RMS objective and change for a different one, or change the whole optics module from low-cost to the RMS version, or 160mm RMS to infinity, but this does require removing the slide and is a little fiddly. It is something to do when you change teh type of thing you are doing, rather than just to look at teh same object in different magnification. However having only one objective at a time is one of the reasons that the microscope can be so compact. With a robotic microscope for long-term observation or for slide scanning it is more usual to only need a single magnification.

There is a development prototype of a version with swappable optics from @rooksoup, which is in the repository in a merge request at https://gitlab.com/openflexure/openflexure-microscope/-/merge_requests/323. I am not sure how close this is to being a version that others are able to build yet.

It would make most sense to build a microscope in one of the standard versions first to get used to the build and operation. The swappable objective parts would just re-use the electronics and tube lens from a regular build and they fit onto a regular body. If you were looking to go down this route it would probably be best to build the cartesian microscope rather than Delta. Please note the bugs thread on the forum: Openflexure Microscope V7.0.0-beta1 released. If you decide to build the upright version in preparation for the swappable objectives, consider following the current master version where many of the bugs are attended to, and there are some other build improvements for the upright: Openflexure current build is here! - Announcements

Thanks for tagging me @WilliamW - the swappable objectives upright microscope linked above in the merge request is a working version with a set of draft instructions included as long as you don’t mind running “gitbuilding serve” to get a local build of the instructions within that branch.

Although it requires some extra hardware (magnets and dowels) to construct the kinematic mount and is therefore a bit fiddlier compared to the standard upright, it does function repeatably as long as each objective lens carrier is assembled consistently. I’ve done some basic characterisation to check it works well on my end, but it would be very useful to get feedback from anyone else who ends up building it, or is considering doing so, to make sure it’s a replicable bit of kit.


That is great! The merge request will actually build the full instruction set and the parts. You can get to it with the “view app” buttonimage on the merge request page https://gitlab.com/openflexure/openflexure-microscope/-/merge_requests/323 (on the right below the green ticks). Note for users that this is not a release. It is the current draft and is rebuilt every time a change is made, so it is not stable and the instructions and parts linked may not actually work at any particular time. Also this does not include relevant improvements to the base microscope, so only use it for the swappable customisation. For the main body, stand, electronics drawer, upright illumination etc see the bugs list or the current master as in my earlier post. The draft swappable optics instructions are linked from the customisations page of those instructions.

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I have contemplating this topic also but along the lines of doing a 3D printed revolver. But this is still very much incomplete and I am still pretty much a beginner when it comes to OpenSCAD and 3D printing. I also don’t have the best track record of getting microscopes actually finished…

This would need to go onto a upright Delta - which does not even exist yet IIRC - or a upright with a strong enough z-axis to carry the whole head or - may be more feasible - an upright where the whole stage is on a Z-Axis.

I just yesterday did some test prints so see whether ball bearing races can be printed upside down without support which would be needed here. So for this looks promising. Although I only had 8mm balls which are pretty bulky and the final version probably needs something more like 4mm balls.

I will probably try to get my laser cut microscopes working first so it is easy to add the bulk needed to fit such a large optics assembly. The high resolution optic module also just barely has enough space between the objective thread and the tube lens to cut it into two pieces. So I might want to change the distances there to make this a bit more comfortable. But my optics foo is still not quite up to that.

I also still have a laser cut version of a revolver/rocking arc in the back of my mind but it has not yet solidified into an actual design.


That would be an interesting version as well.

The Delta stage has basically the same illumination platform as the cartesian Microscope, so you can use the Upright components on the Delta. However in your case you would be designing everything in the optics part, just using the mounting. The optics z-motion is not required on a Delta anyway. The Delta does not yet have the third mounting screw point on the illumination platform, which gives a lot of stability when mounting more than just the illumination.


are there any images of this version?

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Here’s a full look - photos accompanying the draft assembly procedure should be available within the merge request as William describes. Each objective is contained in its own carrier that matches a Maxwell kinematic mount within the modified optics module, and be grabbed to quickly snap objectives in and out of position.

I should note that it’s (both metaphorically and literally) less stable than the current release of master, as it’s still in testing, though I don’t expect the final physical design to change particularly much from the current working version. As the objectives are positioned above the centre of mass of the 'scope, it’s wobblier than the standard inverted microscope, but I think the carrier approach can be a bit more robust than trying to suspend multiple objectives at once from a printed mechanism.

If anyone would like to try assembling one, any feedback would be very welcome!


I like the idea of the carrier approach as well. I agree with you that it would be better for the objective to fit back inside the cage. Too bad we can not manufacture a slot in there to be able to do the swap.

Also, I think it would make sense to make a tray to attach to the base to hold the unused objectives. :slight_smile:


There is quite a large spare corner in the base, the other side from the electronics drawer. @j.stirling was considering an accessories and tools drawer. A swing out objective storage is a project :slight_smile: .


If we ever get the apertures for the illumination done the tray can have a place to store the correct aperture with the objective.

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Love this modification. Printing one right now and looking good.

I noticed the condenser is oddly shaped. The nut did not fit in the socket and I have to cut some excess plastic and push hard to insert it. This should be a fairly easy redesign fix

The cam will need a longer cable than the standard provided. It seems that the clave may need a sharp turn backwards to be out of the way. I am concerned it may put some stress on the connector.
Will turning the camera be a better placement? This would allow to run the camera cable on a tower channel.

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I am so sad that I can not setup my printer…

I have ordered a multitude of things to get this all working and am very excited.

This is the version of the scope that I want to experiment with. Will this version support auto focus? Not sure if the stepper can be mounted on there.

Only other thing is how to handle different types of lighting like dark field. (I am just now stepping into this world so might have that terminology off…)

What is the problem with your printer? I have a CR10s that I have used nonstop for about 8 years. I made the mistake of attempting to purchase spare components to repair it. I suddenly realized I’d spent enough money to buy a new one. Finally, I purchased a new Ender 3 Pro for $99 from Microcenter. I’m quite pleased with it.

It is designed to fit the stepper motor. My impression is that There is no reason why autofocus should not function.

I am not sure there is a well developed dark field option. I found this thread.

My primary printer is old and I have a newer Creality K1 Max which should print this project beautifully. It is still in the box because it was damaged and I am working with Creality (trying to anyway) on resolving this issue. I want a printer swap or return (without paying shipping). So basically I have a printer here, but can’t use it because it is broke. It is torture.

As for the dark field option, I know that it has existed for the normal configuration, but not sure with the upright.

The upright illumination has been corrected. The parts are available from a post about bug fixes on the Openflexure Microscope V7.0.0-beta1 released thread.

The current master build will have this and all of the other approved recent changes - although it also is not a tested release, so be aware of the notes on the Openflexure current build is here! post.

The cable does need to be long. 300mm is specified for the Upright, but that is for the version with the low-cost optics of the Pi camera. With a microscope objective and lens tube the camera is quite a bit further up. It probably needs 400-450mm. In my standard upright build the cable is reasonably out of the way and not too vulnerable in use. A cable slot would be useful, both for the camera cable and the motor cable. but there do not seem to be simple places to put one. Unfortunately your sketch would put the cable through the z-actuator mechanism.

The stepper motor just mounts on the upper z-axis instead of the z-axis in the main body. Autofocus then works as normal.

This might be trickier. Dark field is not well documented in general for Openflexure. The most complete instructions are for the LED grid illumination. That fits on the illumination dovetail in the standard inverted configuration. The upright configuration needs to fit the illumination on the optics dovetail, which is different. apart from the mounting difference, there is also less space to fit a large illumination array.


as William says, this version does already support a Z-stepper and auto-focus - although I realise it’s not shown clearly in the photo above! Here’s a better look (featuring old Z-stepper gear still in place)

@dgrosen this version does indeed require a longer camera cable than usual due to the extra height - the lengths these cables come in currently result in a little awkward slack at the top. 30mm is currently just fine in terms of length. The cable should currently exit the camera pointing towards the X stepper. If this isn’t the case, that’s great to know, and my apologies for you receiving outdated STLs! I’ve currently tucked the cable between the main body and stand, but this could also do with a more “professional” finish.

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As the self declared chair of the “Campaign for the Creation of Copious Cable Channels” I support the idea. This specific locations wouldn’t work as the levers for the z-actuation mechanism are underneath that channel.

What I have started doing for the field dissection microscope is just putting a couple of holes on the sides of components and screwing on a clip that holds the cable in place providing some level of cable management without the complication of completing a full channel.


It is a decent stop-gap to have some control of the cable. While further cable management is considered. Personally I find the flat ribbon cables very hard to manage. In terms of long term use something will need to be done to protect the delicate dangling cable in the upright.


You are right. That is why you are an engineer and I am not :slight_smile:

However, I’m still hoping for a stylish way to hide that ribbon cable. It is problematic to have cables exposed in this manner. If you are right-handed, this is not a major issue depending on how you orient the microscope. For my intended use case, I’ll be concerned about knocking it down every time I change objectives or glass slides.

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