object glass vs lens system

object glass and lens system both are nouns.

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

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

object glass: 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 glass include lens, lense.

object glass (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