Hello, and welcome to this third course in optical system design with myself Robert Macleod and my colleague Amy Sullivan. This course is where we put it all together. In the previous courses we've learned first order design, pencil and paper techniques to lay out the function that we want with paraxial simple lenses, we learned in the second course how to start turning those into real glass with real curvature, real apertures. In this course we're now going to really put that pedal to the metal, we're going to take these optics and learn why they're not perfect and how we have to improve real designs to get them to function typically at the level we need. So up till now a point focus would image to another point and we see in this typical example here, that for lenses that are not paraxial for large cones of rays that basically never happens. So we'll learn the names of the kinds of aberrations that we see, how to fix them how they scale with aperture and field and other variables that we have control over and techniques to design to minimize particular aberrations. Some of those aberrations for example are chromatic or color based aberrations, because of course lenses are made of glass and the index of class isn't a constant with wavelength that's why prisms work. So we'll see for example that there are effectively multiple foci, one for each color of light. We will of course go into the lab to see what this looks like and we'll see that those different rays, look like a beautiful rainbow in the lab at the focus. Beautiful only if you're appreciating it for its basic colors, not so beautiful if you're a designer trying to make a camera that works independent of color for example. This will lead to techniques to minimize these kind of aberrations and up to now for example in our lensmaker's equation, we had only one focal length but we had two different curvatures and our refractive index and thickness. Though we're in the formula now we'll learn, that we're going to spend those extra degrees of freedom to minimize aberrations. So here's for example a simple singular lens and we're what's called bending the lens, we're keeping the focal length constant and we're measuring the aberrations and we find that a particular one of these designs we get to the best form lens. You'll learn from that that lenses have fronts and backs and the most embarrassing thing as an optical designer or an optical engineer, is in the lens, put a lens backwards. Focal length is the same aberrations depends strongly on the orientation of lens unless of course it's a symmetric lens like the example we showed here in the lab. So as always we're gonna take you into the lab and let you see what these look like. This is where now the computer tools like optical optic studio is absolutely critical. Because we need to calculate the contribution of every surface in our optical design like this lithography lens which has a relatively complicated system, what that surface does for each of the kinds of aberrations that we know about and the codes are very very good at that. So, we will minimize these aberrations by using numerical optimizers and by understanding particular design techniques that can minimize the designs and the only way you really understand if your design meets your specifications, is to load it up into something like optic studio and to work there until it meets the needs that you have. We'll introduce components beyond just lenses up to, now we've sort of focused on those but one of the fun parts of optics there's there's a lot of toys. Things like prisms and diffraction gratings, so we'll go through each of those and how they contribute to your design kit and how you use them in a code like optic studio because it knows about such things. We'll do a capstone project which is a hyperspectral imager, so both images and tells you about the spectrum at every point and these are used to in satellites for example to look down at foliage and understand the health of it and interesting things like that. Finally, we'll look at the human eye itself. This is for one thing a remarkably high-performance optical system so it's interesting to study nature and figure out what's been done there, as well as many of your instruments wants to talk to the human eye a telescope or a microscope let say. So you need to know how that goes into your design and of course how it goes into a code like optic studio. So in summary, the point of this course is to take the pencil-and-paper designs where you've designed everything from the first-order principles, what the magnification should be, the numerical aperture which might define resolution and actually make it work because typically those techniques aren't good enough to produce a system that really meets your specifications. Once you finish this course in some sense, you can now layout an optical system and call yourself an optical designer because you can specify this does work and it meets the requirements that I have.
