clap/lay/set eyes on
clap/lay/set eyes onThese words all mean to become aware of sb/sth by using your eyes, especially suddenly or when it is not easy to see them/it.以上各词均含看见、见到、看出之义，尤指突然发现或注意到。
to become aware of sb/sth by using your eyes指看见、见到、看出：
She looked for him but couldn't see him in the crowd.
她在人群里找来找去，但没看见他。
He could see (that) she had been crying.
他看得出她哭过。
to see or notice sb/sth, especially suddenly or when they are not easy to see or notice指看见、看出，尤指突然发现或注意到：
I've just spotted a mistake on the front cover.
我刚才在封面上发现了一处错误。
to see or notice sth for a moment, but not clearly or completely指瞥见、察觉：
She caught sight of a car in the distance.
她瞥见远处有一辆车。
He caught a glimpse of himself in the mirror.
他看了一眼镜子中的自己。
( literary ) to see sb/sth for a moment, but not clearly or completely指瞥见、看一眼：
He'd glimpsed her through the window as he passed.
他路过时透过窗户瞥见了她。
( informal ) (usually used in negative statements) to see sb/sth（通常用于否定句中）指看见、注意到：
I haven't clapped eyes on them for weeks.
我几个星期都没见到他们了。