SLM Mirror Array Metrology via Grazing Incidence Interferometry

The patent creates multiple virtual images of the SLM mirror array using a diffraction grating to split the reflected light into multiple diffraction orders. Each diffraction order forms a separate image on the detector, allowing simultaneous measurement of multiple mirror positions without physically scanning or repositioning the SLM device. This copying approach enables complete metrology data acquisition while maintaining continuous exposure process operation.

The patent transforms the measurement approach from temporal scanning (moving the SLM device through different positions over time) to spatial parallelism (capturing multiple positions simultaneously in space). By using a diffraction grating to create multiple diffraction orders that form simultaneous images at different locations on the detector, the system measures multiple mirror positions at the same moment, eliminating the time required for scanning or repositioning operations.

The patent makes the single detector serve multiple functions by capturing images from multiple SLM mirror positions simultaneously through different diffraction orders. The same detector array that would normally capture a single image now captures multiple position images at once, eliminating the need for separate scanning mechanisms, multiple detectors, or complex repositioning systems. This multi-functional approach maintains measurement precision while reducing device complexity.