Optical Filter Stack for Accurate Hyperspectral Sensing

The patent replaces mechanical moving parts (such as tunable filters or scanning mechanisms) with a static photodetector array where each pixel is equipped with a fixed wavelength-selective filter. This substitution eliminates mechanical complexity while maintaining spectral detection capability, directly resolving the contradiction between measurement precision and device complexity.

The patent segments the spectral detection function across multiple photodetector pixels, with each pixel dedicated to detecting a specific wavelength band through its associated filter. This segmentation allows parallel spectral measurement without requiring mechanical scanning or complex signal processing to unfold temporal spectral information, thereby improving accuracy while reducing device complexity.

The patent changes the manufacturing approach by using standard photolithography processes with relaxed dimension tolerances to define the filter structures, rather than requiring deep UV lithography with tight critical dimension control. The filter design parameters (layer thicknesses, materials) are optimized to achieve the desired spectral selectivity without demanding extreme manufacturing precision, thus improving ease of manufacture while maintaining manufacturing accuracy.

The patent employs a lift-off technique using sacrificial spacer layers that are deposited and then removed to define the filter cavity structures. This approach uses temporary, easily fabricated spacer layers (deposited by standard PECVD or spin-coating) rather than requiring precise etching masks, reducing the need for high-end lithography equipment and simplifying the manufacturing process.