I’ve had this little brown book in my posession since 1996. For years it jostled around in my rucksack as I carried it to and from work (hence the battered and frayed corners). I thumbed and perused the pages with a sense of longing for the knowledge they contained, all the while thinking to myself “This is stuff I’m supposed to know!” Strangely enough though, I managed to bluff my way through a decade of employment with job title ‘Optical Design Engineer’ without really understanding the principles of lens aberrations and lens design. Well, diffraction limited imaging is not really that important when you’re designing spectrometers rather than camera lenses. In all those years I didn’t quite make it to the end of chapter 3 of Kingslake. Poor show really.
I managed to complete chapter 3 at the end of last year, and this January I decided that this was going to be the year I finally completed the book. I’ve been making pretty steady progress with it since. I’ve found it a pretty challenging because so much of the derivation work is left to the reader to provide (unless you’re prepared to take everything presented on faith, which I’m definitely not). On reflection, I think the extra work this has entailed has made the learning experience deeper and more satisfying. There’s nothing quite like working something out for yourself if you want to really understand it.
Yesterday I reached a milestone by completing chapter 10 of the book. This has been by far the toughest chapter so far (and I would hazzard the most difficult in the whole book, even though six more chapters remain). The greatest hurdle in chapter 10 (and one I’m actually quite proud of) was proving Petzval’s theorem for the general case. This took several days of mental cogitation and many pages of scribbled notes before I saw the ‘obvious’ key to the solution staring me in the face. Funny how things often go like that.
So chapter 10 completes the formal treatment of aberration theory, leaving the remaining six chapters for the application of this theory to real lens designs. I’m going to take a bit of a break from Kingslake now before I begin my final assualt, but I believe I’m still on course to finish the book before the year is out.
