Introduction: Smartphone Fundus Camera
Most of us have two of the three major components of fundus camera in out pockets at all times, a CCD camera and a LED light. These of course are on our smartphones. What would happen if we found a way to add the third piece of this equation to our phone, the right lens. This was the central focus of my time as an Artist in Residence at Autodesk's Pier 9.
My inspiration for the project was my late grandma Mimi. Watching her gradually lose her vision to glaucoma was really painful, and building this project proved very cathartic. Glaucoma is traditionally diagnosed through checking eye pressure, however there are a whole plethora of other diseases detectable through fundus photography. So without further ado lets begin our journey into the back of the eye.
Step 1: Research, Research & More Research
Is really hard! Of all the engineering disciplines out there, I've heard this one be referred to as "black magic" the most often. Before undertaking this project I had zero optics knowledge and I would still place my self in the beginner category. Arm yourself with as much knowledge as possible, Modern Optics is a good place to start but gets a little to advanced for what we need. Throughly understand the Lens Makers Equations is a must and being able to to Ray Tracing would also be a huge boon.
Step 2: First Prototype
Just a Stick
My first prototype was just the lens mounted on a stick mounted to an iPhone, very technologically advanced. However, it allowed me to place the lens at difference distances from the phone camera, experimenting with the optics before I understood the physics behind focal distances, and where images are made.
Step 3: Optical Test Stand
Theory into Practice
I designed an built an optical test stand to help turn the theory and research I've been rapidly ingesting into practice. Giving me the ability to test various lenses and rapidly reposition the focal length was super useful when trying to find the optimal distance of the lens.
The Ophthalmologic Test eye allowed me to simulate various lighting conditions through a constand pupil diameter. When light shines into your eye, your pupil will constrict, which is good for your eye but bad for trying to see your retina. However this eye has a fixed pupil dilation at 6mm which is actually slightly smaller than a real dilated eye.
Step 4: Second Prototype
I was inspired by two other Artist in Residence's Prisca Visbol who was working on what was essentially flat pack fashion. Could you design this device to be shipped in mass quantities, like IKEA, without taking up a lot of space? Using a laser cutter I went and explored this idea. Through a couple iteration the answer appeared to be mostly yes, if not accounting for the lens.
Step 5: Raspberry Pi Prototype
Using Raspberry Pi Camera
My thought was that an infrared camera would allow testing without the use of dialating drops. Allowing light into the eye that did make the pupil constrict. While I love the case I designed for this piece the overall design was flawed from the beginning, because of one main factor.....Auto Focus.
Every persons eye is a little different, their myopic error creates images that focus on different planes. The Autofocus in your camera helps get rid of that easily, but with the raspberry pi camera it was a very manual process that was constantly in flux.
Step 6: Final Prototype: Part 1
Using foam I carved out a basic rectangle and then slowly started carving away the corners. I made a couple different sizes and a couple different shapes. Then I gave the models to friends of both genders to see how the prototypes felt in their hands. Shockingly both sets of friends preferred the same smaller, rounded edges model. With this in mind I went to CAD.
Step 7: Final Prototype: Part 2
It took a couple tries to get this printed properly but once done I turned to Prototyping and Modelmaking for 3D printing finishing techniques. I used bondo for fill in the really large filament marks, especially on the first layer. Use an extremely small amount of filler. I've found that just smoothing out the print through high grit sanding was better than immediately going to body filler.
I did two rounds of primer with minimal sanding in between, and then a final coat, followed by some high grit sand paper to give the final piece a more plastic feel. The goal was to imitate an injection molded piece.
Step 8: Final Prototype: Part 3
The first test of this final prototype went so much better than I ever could have imagined. Using the Filmic Pro app to lock focus and exposure I was able to finely tune the retina pictures we were getting on our smartphone. Zooming in to approximately 2x we lost a bit of resolution because of the digital zoom but having the retina fill up the phone screen was pretty awesome.
Shoot at 30fps had some interesting benefits, one being that I could go back into very clear sections of the video and use photoshop to stitch them together. It was pretty amazing to see the noise drain out of the images and veins you could barely see in initial photographs became uniquely visible. It was a very cool experience to say the least.
Wrapping it up
For me this project is far from over. Eventually creating a $10 eye exam just seems like a project I could sink my teeth into for many years to come. Thank you to everyone at Pier 9 for being helpful and amazing, none of this would be possible without you all :)