eyepiece vs lens system

eyepiece and lens system both are nouns.

Word	Noun	Adjective	Verb	Adverb
eyepiece	Yes	No	No	No
lens system	Yes	No	No	No

As nouns, lens system is a hypernym of eyepiece; that is, lens system is a word with a broader meaning than eyepiece:

eyepiece: combination of lenses at the viewing end of optical instruments
lens system: a transparent optical device used to converge or diverge transmitted light and to form images

Other hypernyms of eyepiece include lens, lense.

eyepiece (noun)	lens system (noun)
combination of lenses at the viewing end of optical instruments	a transparent optical device used to converge or diverge transmitted light and to form images