Disclosed are an amplitude monitoring system, a focusing and leveling apparatus and a defocus detection method. The defocus detection method comprises the steps of: adjusting amplitude of a scanning mirror (201) to a theoretical amplitude value and recording corresponding theoretical output voltage values of a photodetector (309) (S1); adjusting the amplitude of the scanning mirror (201) and sampling real-time amplitude values θi of the scanning mirror (201) and real-time output voltage values of the photodetector (309) to calculate compensated real-time demodulation results Si, and recording real-time defocus amounts Hi of a wafer table (305) (S2); subsequent to stepwise displacement of the wafer table (305), establishing a database based on the compensated real-time demodulation results Si and the real-time defocus amounts Hi of the wafer table (305) (S3); and in an actual measurement, sampling in real time an actual amplitude value θk of the scanning mirror (201) and actual output voltage values of the photodetector (309) to calculate a compensated real-time demodulation result Sk, and finding an actual defocus amount Hk of the wafer table (305) by searching the database using a linear interpolation method (S4). Such a focusing and leveling apparatus and defocus detection method avoid degraded stability of the scanning mirror due to long-time operation, which may lead to low wafer surface defocus measurement accuracy of the focusing and leveling apparatus.

An imaging device for an additive manufacturing system is provided. The additive manufacturing system includes a material. The imaging device includes a high resolution imaging bar including at least one detector array, and an imaging element positioned between the at least one detector array and the material. The high resolution imaging bar is displaced from the material along a first direction and extends along a second direction. The high resolution imaging bar is configured to generate an image of a build layer within the material.

An amplitude monitoring system, a focusing and leveling apparatus and a defocus detection method. The method includes: adjusting amplitude of a scanning mirror to a theoretical amplitude value and recording corresponding theoretical output voltage values of a photodetector; adjusting the amplitude of the scanning mirror and sampling real-time amplitude values of the scanning mirror and real-time output voltage values of the photodetector to calculate compensated real-time demodulation results, and recording real-time defocus amounts of a wafer table; subsequent to stepwise displacement of the wafer table, establishing a database based on the compensated real-time demodulation results and the real-time defocus amounts of the wafer table; and in an actual measurement, sampling in real time an actual amplitude value of the scanning mirror and actual output voltage values of the photodetector to calculate a compensated real-time demodulation result and finding an actual defocus amount of the wafer table.

An imaging device for an additive manufacturing system is provided. The additive manufacturing system includes a material. The imaging device includes a high resolution imaging bar including at least one detector array, and an imaging element positioned between the at least one detector array and the material. The high resolution imaging bar is displaced from the material along a first direction and extends along a second direction. The high resolution imaging bar is configured to generate an image of a build layer within the material.