object lens vs lens system

object lens and lens system both are nouns.

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

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

object lens: the lens or system of lenses in a telescope or microscope that is nearest the object being viewed
lens system: a transparent optical device used to converge or diverge transmitted light and to form images

Other hypernyms of object lens include lens, lense.

object lens (noun)	lens system (noun)
the lens or system of lenses in a telescope or microscope that is nearest the object being viewed	a transparent optical device used to converge or diverge transmitted light and to form images