The concept of making a fish eye lens to capture the sun might look simple to the naked eye. However, as with most things in life, there are tremendous details that go into creating a solid design.
To first understand the design constraints, we wanted Step Solar solution to be more accurate than a scientific tool (which I will explain in a moment), easy to use and cost effective. Not to mention that it must be ready for mass production and consumption.
Keeping these constraints in mind, our team consisting of three Ph.Ds from top US and UK universities set out to find the solutions. What came about was the Step Solar App and Lens solution.
- First of all, we are working with commercially available cell phones, mass produced by the manufacturers, with the sole focus to reduce production cost. This means that we are working with cameras which will have a large tolerance from each other. Yes, two phones of the same model, made on the same assembly line, made at the same time will be different. So our software needed to customize our solution for each phone independently. Even a couple of degrees of difference in angle would diverge the results by a couple of percentage points in production. Two degrees is about 5 pixel difference on a 5 MP camera. This is the level of accuracy we were targeting.
In our software, we have developed a smart solution that actually finds the center of each phone and lens. The phone is calibrated by the user before it can be used for the first time. This calibration process takes between 2-3 minutes and achieves an accuracy of about 2 pixels.
- The installer installs and uninstalls the lens a few times a day. What if the lens is not centered right above the camera every time the lens is installed? To get around that, we developed a Smart Lens. Basically we needed to make sure that even if our lens was not centered right above the phone camera, the picture of the sky would not shift. Again, our designer went to work. This time they came up with the concept of the orthogonal fish eye lens, meaning that even if the lens was not placed right on top of the camera, the image would not shift. We had to find one of the best lens manufacturers in the world to manufacture the lens.
- Once the lenses were designed, the next step was to take them out in the field for field testing. Well, it turned out that the glare from the sun made the image extremely bright, where the edges of different objects were hard to detect. The issue turned out to be what we call sun spots. We consulted with several lens experts from around the globe and every one gave the same answer: it is a difficult proposition to take a picture of the sun and expect to get much definition from the rest of the image. There were two issues. The first was the amount of light entering the lens; the light would bounce around in the lens chamber and create internal reflection. The second issue was the amount of light passing through the several stages of the lens, which would cause the light to scatter on the surface of the lens.
- So we went back to the drawing board. This time our engineers developed an anti glare, high light absorption lining. In addition to that, we also designed a glare reduction chamber. With the combination of these two, we were able to reduce the light bouncing inside the lens. To eliminate the light spreading from the lens, we used a micro film coating. The issue was not limited to hardware—we developed an adaptive filter to reduce the effect of the sun glare as well.
All of this might sound complicated, but at the end of the day it makes the life of a solar installer simple and provides accurate results to the home owner.