Source of potential error (20-25%) when using Ocular micrometer

Es gibt 5 Antworten in diesem Thema, welches 347 mal aufgerufen wurde. Der letzte Beitrag () ist von PBR.

    I want to discuss something I noticed today while cleaning my microscope desk and lenses.


    I have two ocular micrometres of different tube lengths. So I, while checking and experimenting on the stereomicroscope, I discovered something which made me wonder and worry.


    Using the same subject (letter R of a receipt), I put the adjustable eyepiece setting of the stereomicroscope all way up and then all way down and realised that the length of the 'R' varied from 16 to 20 divisions (c. 25% difference). I repeated this with the other micrometer. R measured differently between 19 to 23 divisions - four different readings for the same subject!!!. I was not aware that this would have any effect (never been told during courses on microscopy). It may be a potential source of error when measuring spores in the light microscope if the microscope eyepiece tube goes up and down (not the lens itself)


    So this makes calibration a bit more awkward and the following steps should be adopted:


    1. Put the micrometer always on the same eypiece and set it fixed in middle way setting (o).

    2. Focus compensation between eyepieces should hence be done on the other eyepiece only

    3. Using this fixed setting, perform callibration for each micrometer



    I thought this is good to share and discuss!


    Diopter adjustment also changes image size, I also have never seen this mentioned but it should happen if you think about it.

    Going from one extreme to the other in an adjustable eyepiece should yield a range of about 4 diopters resulting in an rough doubling of image size. (e.g. see HERE) when you project it to a sensor in an otherwise unchanged system.


    Also: If you go to the limits of the diopter adjustment on eyepieces funny things happen*. Just don't go there...


    Personally I would recommend (like you do) the ocular micrometer in the unadjusted eyepiece, or if adjustable keeping it at 0 for convenience and adjusting with the opposite eyepiece. (idk why stereo microscopes often come with 2 adjustable eyepieces...). If you want to adjust you have to re-calibrate.


    Peter


    *a funny thing that happend to me is the objectives in a compound microscopes loosing parfocality (usually all objectives have the same focus point and you can switch them without loosing focus). This is no longer true if both(!) eyepieces are set to -2.5/+2.5 diopters even if by conventional

    Hm, thats a problem with the forum software, either right click and "open in separate window" or copy paste this: https:// bolioptics. com/blog/how-to-convert-diopters-to-magnification/


    Yes, I would have expected that changing both eyepieces in the same manner would not affect overall performance. It does however.


    Peter