在冷战时期，这种微粒照相机是专门用来转移秘密文档的，它能够拍照，还可以将整本书的信息微缩到一张小小的胶片上。

Transferring secret documents during the Cold War was aided by this microdot camera that could photograph and reduce whole pages of information onto a tiny piece of film the size of a sentence period.

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不过，现在美国国家公共电台(npr)已设法揭开了Google公司专利图书扫描系统背后的神秘细节——被发现的秘密就是三维红外照相机。

Now, though, NPR has managed to uncover the details behind the company's patented book scanning system - and found that the secret is 3d infra-red cameras.

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