When we observe objects under Foldscope, sometimes we want measure the size of the objects we are observing for various purposes. In this post I’m describing a method with which we can measure the size of the object.
With the Foldscope deluxe kit, there are few grid slides with different grid sizes. I used a 0.5 mm grid slide. I attached the grid slide to another glass side as shown in the picture (Fig2).
Then on top of the grid I kept few anthers of the Coral plant (Fig5) (Russelia equisetiformis) and teased it so that pollens come out. Covered it with the tape and put it under the Foldscope.
Located few pollens around which grid is also visible, we need a grid to measure the size (Fig3).
Took a few photos and then opened the photos in an Android app called ImageMeter (Fig2)(https://play.google.com/store/apps/details?id=de.dirkfarin.imagemeter).
First used a grid of know size (0.5mm) to create a reference scale and then measure tool to measure the length and width of the pollens (Fig3).
My measurements show that the pollens of the Coral plant are 22 microns in length and 14 microns in width. I crossed checked it with the literature and found that my measurements very close (20 microns) to what was reported in the paper (http://rcpol.org.br/wp-content/uploads/2018/02/32.pdf).
I think variants of this method can be used to measure the size of an object.

Update: @varuni used grid as reference and measured the diameter of the circular visible area through the lens, which is 810 microns. She doesn’t need grid slide anymore, she uses the diameter as reference to measure the size of the object under the Foldscope.