noun
keen eyesight; superior vision
Archaic idiomatic expression referring to exceptionally sharp eyesight, derived from the legendary figure Lilou in ancient Chinese folklore. Used in classical or literary contexts.
彼の観察力はまさに離婁の明と言える。
His powers of observation can truly be called the keen eyesight of Lilou.
明察 means keen insight or discernment, often used for mental sharpness, whereas 離婁の明 is a more literary and archaic term for visual acuity.
From the Chinese legend of Lilou (離婁), a figure renowned for his exceptional eyesight. The expression is used in classical Japanese to praise someone's sharp vision.