Improving Microscope Images
Submitted by Harald K A, Steinberg, Norway
The problem with images through the microscope, is the Depth of field (DOF). A single image has a typical DOF of 1 µm. On the fine focusing knob on the microscope, it´s divided into 100. This means a movement of 2 µm. 100 steps to one revolution. It just fell into me, the stepper motor has a typical of 200 steps pr. revolution. It must be possible to mount a stepper motor to the microscope. A closer look, it has coarse and fine focus on both sides. Taking of the knob on left side revealed the axle itself. Quick search on eBay, I found a flexible axle mount, but where could I find a USB controlled stepper motor? Searched eBay again, no luck. Google is your friend. I found PC Control Ltd, and they had all I needed. Ordered the starter kit. I also ordered a NEMA 17 bracket (eBay). When I got it all, I went to the local workshop. They made a plate to go under the microscope and a bracket to attach the motor. I drilled all the holes and mounted it together. Now I can calculate the number of steps needed for the sequence of images. Fill in the number of steps, delay between each step and press "Run". With a shutter speed of 1 second I typically set the delay to 5000ms. I can run the motor fast from start to end position and back to check that I am within the limits. I manually press the shutter with the cable release on the camera. With this system I get 1µm movement on each step, which is what I need for this type of photography. I need typically 250-300 images, depending on the subject.
In the end, when all images taken, I focus stack them. The image below is a 250 image stack of Lily Pollen....