An ultrasonic projection system includes an image capturing device, an ultrasonic scanning device, and a projection device. The image capturing device is used for capturing a reference image toward a surface. The ultrasonic scanning device includes an ultrasonic probe and a processing unit. The ultrasonic probe performs an ultrasonic scanning operation on the surface to generate a scanned image. The processing unit is used for defining a plurality of projectable regions on the reference image corresponding to the reference image according to a location of the ultrasonic probe in the reference image, and is used for setting one of the plurality of projectable regions as a real projection region. The projection device is used for projecting the scanned image on the real projection region of the surface.一種超音波投影系統包含影像擷取裝置、超音波掃描裝置,以及投影裝置。影像擷取裝置用來朝表面擷取參考影像。超音波掃描裝置包含超音波探頭以及處理單元。超音波探頭於表面上進行超音波掃描以產生掃描影像。處理單元用來根據超音波探頭在參考影像中之位置,在參考影像中對應表面之位置上定義出複數個可投影區域,以及將其中之一可投影區域設定為實際投影區域。投影裝置用來投射掃描影像至表面的實際投影區域之位置上。18‧‧‧超音波探頭19‧‧‧定位標記22‧‧‧表面24‧‧‧掃描影像26‧‧‧可投影區域28‧‧‧不可投影區域
