Cheap Educational Scope

Problem Statement

I needed a quick idea for summer camp educational workshop that was 'sciencey'. I remembered seeing this thingiverse link a while back and sharing it with a friend of mine who is an elementary school teacher. I wanted to do this as a workshop but also to understand the operation behind it as I am ashamed to say that my knowledge of optics is pretty bad...

The Eye

I first used ray tracing theory to understand the real and virtual image locations. I was hung up very quickly on the fact that without an eye, a virtual image is pretty useless. The eye is an integral part of a microscope!!!

Luckily I found some information on the human eye. Some of the really important ones are

• Visual acuity: 2 arcminutes
• Distance of Nearest Distinct Vision: 25cm (between this and infinity are good places to place your final virtual image)
• Translated visual acuity at the distance of nearest distinct vision: 145µm (wow, my eyes are amazing!!)
• Focal Length of the Eyeball: 2.2cm

• • Reminder to myself to scan and stick in the raytrace model**

The 2-lens Matlab Model

clear;
%all units are in meters
Fo=.032;
Fe=.032;
Dndv = .25;%.25 is the distance of "nearest distinct vision" in humans
Me = Dndv/Fe; 
Di = 3.2*Fo; %random guess of 4
Lt=Di+Fe; %tube is the image distance plus the focal length of the occular
%M=f/(f-Do) for distance to the object 
%M = -Di/Do
%M = (f-Di)/f for distance to the image
Mo = (Fo-Di)/Fo;
Do = -Di/Mo;
Pe = .003; %entrance pupil of 3mm
Theta = atand((0.5*Pe) / Do);
NA = sind(Theta);
Resolution =  (530e-9)/(2*NA); %green light resolution
%human visual foveal acuity is 2 arcminutes
Aacuitydegrees = 2/60;
Dsep = 2*sind(Aacuitydegrees/2)*Dndv; %lowest resolveable distance at Dndv
Moptimal = (2*NA*Dsep)/(550e-9) %550nm is green light
Total_Magnification = Mo*Me

RESULTS
-----------------------------
Do = 46.5mm (object-lens distance for an in focus image)
Lt = 134.4mm (optical tube length)
Moptimal = 17.0354
Total_Magnification = -17.1875

2013 Jasper Nance KE7PHI