Wow, fantastic Dr Tadrous! I have been following along, from the foundation scope to finishing the condensers and kholer illumination. Currently working on the advanced filter block for epi illumination (my primary goal). After that I will take a shot at the z motor. This project has kept me and my prusa printer quite busy for a few weekends already :) Big thanks 👍
Hi, amazing work done here! One question, why does hysteresis happen in the first place? It seems odd that the z focus affects the x and y coordinates. Also, is this hysteresis also observed when moving on x and y and the z changes?
Hello. The XY hysteresis is only seen on moving in Z (there is no converse - XY movement does not affect Z unless the slide is not moved precisely in one plane, which can happen with some XY manipulators). The XY hystersis with Z motion is, I believe, is due to the fact that the timing belt goes round the three posts in one sense for each Z direction. That is, it goes round all pulleys clockwise when moving the focus platform down and it goes round anti-clockwise when moving the focus platform up. This exerts a rotational 'twist' force on the platform one way for going up and then the opposite way when going down. It is this 'twist' on the focus platform that shifts the objective position w.r.t. the stage ever so slightly. This is only a slight movement but it is noticeable on higher magnifications. I have thought about more elaborate 'balanced' timing belt and pulley mechanisms (that rotate both ways for each Z movement) but this would result in a significant increase in complexity of build and expense. The current design is fine for most projects and manual observations but the hysteresis is a significant problem for implementing a timely autofocus mechanism and hence the current stage design is not suited for fully automated microscopy and slide scanning. It is for this reason that I am working on an alternative XYZ stage mechanism PUMA module for more high end automated microscopy applications.
hello, I was wondering if there is a schematic of the optical train available for a '"fully" kitted scope including schlieren optics. I'm a mechanical designer by trade and would like to partially redesign some of the mechanical elements.
That's a good point. I haven't released such a schematic partly because there are too many configurations to conceive a single 'fully kitted scope' due to the modular nature of PUMA. Having said that I do think I can produce something useful along the lines you suggest and I want to do that for completeness of scientific and open source documentation but I just haven't gotten round to it yet. Hopefully I will put something out there on GitHub soon. I would be very interested to see what improvements and mods you come up with - esp. in regards to the stability/wobble issue. I have some ideas to try out but I am very much an amateur when it comes to mechanics so I look forward to seeing what a Pro can do. Keep an eye on my Twitter feed for the latest updates - I would post a tweet when I release such a schematic on GitHub.
Wow, fantastic Dr Tadrous! I have been following along, from the foundation scope to finishing the condensers and kholer illumination. Currently working on the advanced filter block for epi illumination (my primary goal). After that I will take a shot at the z motor. This project has kept me and my prusa printer quite busy for a few weekends already :) Big thanks 👍
Thanks. I hope it all goes well. Good to hear it works with Prusa as well as my Ender 3. Plenty more to come.
Hi, amazing work done here! One question, why does hysteresis happen in the first place? It seems odd that the z focus affects the x and y coordinates. Also, is this hysteresis also observed when moving on x and y and the z changes?
Hello. The XY hysteresis is only seen on moving in Z (there is no converse - XY movement does not affect Z unless the slide is not moved precisely in one plane, which can happen with some XY manipulators).
The XY hystersis with Z motion is, I believe, is due to the fact that the timing belt goes round the three posts in one sense for each Z direction. That is, it goes round all pulleys clockwise when moving the focus platform down and it goes round anti-clockwise when moving the focus platform up. This exerts a rotational 'twist' force on the platform one way for going up and then the opposite way when going down. It is this 'twist' on the focus platform that shifts the objective position w.r.t. the stage ever so slightly. This is only a slight movement but it is noticeable on higher magnifications. I have thought about more elaborate 'balanced' timing belt and pulley mechanisms (that rotate both ways for each Z movement) but this would result in a significant increase in complexity of build and expense.
The current design is fine for most projects and manual observations but the hysteresis is a significant problem for implementing a timely autofocus mechanism and hence the current stage design is not suited for fully automated microscopy and slide scanning. It is for this reason that I am working on an alternative XYZ stage mechanism PUMA module for more high end automated microscopy applications.
hello, I was wondering if there is a schematic of the optical train available for a '"fully" kitted scope including schlieren optics. I'm a mechanical designer by trade and would like to partially redesign some of the mechanical elements.
That's a good point. I haven't released such a schematic partly because there are too many configurations to conceive a single 'fully kitted scope' due to the modular nature of PUMA. Having said that I do think I can produce something useful along the lines you suggest and I want to do that for completeness of scientific and open source documentation but I just haven't gotten round to it yet. Hopefully I will put something out there on GitHub soon. I would be very interested to see what improvements and mods you come up with - esp. in regards to the stability/wobble issue. I have some ideas to try out but I am very much an amateur when it comes to mechanics so I look forward to seeing what a Pro can do. Keep an eye on my Twitter feed for the latest updates - I would post a tweet when I release such a schematic on GitHub.