His Nobel lecture, "How I Discovered Phase Contrast" (11December 1953) http://nobelprize.org/nobel_prizes/physics/laureates/1953/zernike-lecture.html
Frits Zernike: 1 quote1 like
Frits Zernike was a Dutch physicist and winner of the Nobel Prize in Physics in 1953 for his invention of the phase-contrast microscope. Wikipedia

His Nobel lecture, "How I Discovered Phase Contrast" (11December 1953) http://nobelprize.org/nobel_prizes/physics/laureates/1953/zernike-lecture.html