Assertion: lens's element | /r/HasProperty | introduced in expensive lenses
Facets:
value: very
type: DEGREE
value: some time
type: TEMPORAL
value: during the 1970s
type: TEMPORAL
Source sentences:
text: Aspheric elements were introduced in very expensive lenses some time during the 1970s, but the cost of producing these elements has come down and they’ve found their way into even relatively inexpensive lenses.