Low-Power Optical Microscope

This is an update (July 25, 2025) of my original design, which had a lot of movement of the field of view due to slop between the tube and stand and flexing of the traditional goose neck stand. Slop between the tube and stand was decreased by adding a slit to the tube holder and using compression bands. Stiffness was increased by using a tripod stand. A knob was added to the tube to facilitate focusing. The microscope accepts standard objectives with RMS thread and standard 23.2 mm eyepieces.

A tube length of 100 mm is shorter and works better for children. Because this is not the standard length (which is 160 mm) the magnifying powers printed on the objectives and eyepieces are modified. Here are measured values for 100 mm tube length:

Objective  Eyepiece  Magnifying Power  Field of View

      4X           5X                      8X                      8 mm

      4X          10X                     16X                     8 mm

     10X           5X                     25X                    3 mm

     10X          10X                    50X                    3 mm

Changing the tube length also affects image quality, but this is not noticeable at such low magnifications.

The photos taken through the microscope include top and bottom of a leaf (100 mm tube, 4X objective, microscope eyepiece camera), insect nymph (100 mm tube, 4x objective, cell phone camera through eyepiece, microscope eyepiece camera), seed shrimp (160 mm tube, 4x objective, microscope eyepiece camera), rotifer (160 mm tube, 4x objective microscope eyepiece camera). Illumination using LED penlight.

Other components include the stand, objective mount, and compression bands. I print the stand and tube with 0.2 mm layer height. Print the bottom of the stand with white filament to have a bright viewing background. You will need supports under the threaded section of the stand, but adjust overhang threshold to eliminate supports inside threaded sections of the stand and the tube.   

I print the objective mount with 0.1 mm layer thickness. You can print the objective mount and tube separately and glue them together using contact cement, or you can print them as a combined unit if your slicer lets you specify multiple layer thicknesses. 

I have printed most of my existing units using PLA. Going forward I will use PETG, which  has a lower coefficient of friction and is more flexible (for reducing wiggle between tube and stand). The RMS threads are easier to print in PLA, but I was able to use PETG for the objective mount once I got the extrusion temperature correct.

If the eyepiece is loose, put some tape on the section that slips into the tube. Be very careful not to cross thread when installing the objective. I find that some objectives have better threads than others and use one of the better ones to clean up the threads. Once you get the objective properly started you may have to apply considerable torque get it seated. The tube may need some vigorous turning back and forth to wear down high spots on the threads. Add some compression bands to reduce wiggle between the tube and stand. I use 20 mm diameter hair bands or #215, #216, #217 1/8" O-rings, whichever gives a tight fit without binding. It there is still wiggle, try to stretch the compression band a bit more by moving it out of its slot or partially fill the slot underneath it.