zhēn​kǒng​shè​yǐng​jī

pinhole camera

针孔摄影机 (針孔攝影機) zhēn​kǒng​shè​yǐng​jī
pinhole camera
a simple optical camera without a lens that projects an inverted image onto a surface through a tiny aperture
spy camera
a miniature and concealable camera equipped with a pinhole-sized lens, commonly used for secret surveillance or illicit recording

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