ken vs optics

ken

noun
  • Range of sight. 

  • Youth or children's group. 

  • A Japanese unit of length equal to six shakus 

  • Knowledge, perception, or sight. 

  • The tsurugi 

verb
  • To know, perceive or understand. 

optics

noun
  • The physics of light and vision. 

  • Perception, image, public relations, especially in politics. 

  • The light-related aspects of a device. 

How often have the words ken and optics occurred in a corpus of books? (source: Google Ngram Viewer )