Abstract: With the increasing demand for optoelectronic devices, the market has placed higher requirements on image sensors which are low-cost, high-performance, and capable of stable operation under low-light or dark conditions. Anultraviolet photodetector based on an Au/Al₂O₃/Au architecture is designed in this paper. The device is fabricated via micro/nanofabrication processes, and its optoelectronic characteristics are comprehensively evaluated. Experimental results demonstrate that the device exhibits excellent photoresponse characteristics in the 222~310 nm wavelength range, with the photocurrent showing a clear dependence on incident light power. The device achieves a maximum on/off ratio of 1.3 × 10⁴. At a wavelength of 222 nm, it deliveres a high responsivity of 2.4 A/W, a specific detectivity of 1.1 × 10¹¹ Jones. These results confirm the excellent performance of Al₂O₃ as a dielectric layer in photodetector applications and provide a feasible pathway for the design and fabrication of next-generation ultraviolet detectors. Moreover, a UV imaging system based on this device successfully achieves high-resolution image acquisition, demonstrating outstanding imaging capabilities and enabling precise mapping of digital patterns. This study strongly supports the application of ultraviolet photodetectors in high-speed, broadband response, and imaging fields.