After作介词的句子剖析

After spending some time looking at all the defensive equipment at thewall,

请问这里的After若是作介词后面带了spending作宾语，那样后面的内容是作了什么成分？不可以理解为after是连词吗？

After spending some time looking at all the defensive equipment at the wall,一块是介词短语，作时间状语。