double take
noun informal uk/ˌdʌb.əl ˈteɪk/ us/ˌdʌb.əl ˈteɪk/
do a double take （因认出某人或物，或感觉有异样而）再仔细看一眼，再认真看一下
to look at someone or something and then look again because you suddenly recognize him, her, or it or notice that something unusual is happening
I did a double take - I couldn't believe it was her. 我又仔细看了一眼——我简直无法相信真的是她。