Image Sensor Infrared Cutoff Filter Grid for Iris Recognition

The patent divides the visible light receiving portion into multiple layers including a color filter layer with separate filter units for different colors, an infrared cutoff filter layer with corresponding filter units, and a microlens layer. Each layer is segmented into discrete filter units aligned with specific pixel regions, allowing selective filtering of light wavelengths while maintaining short light paths and reducing noise through purified light reception.

The patent applies different filtering properties to different local regions of the sensor. Each pixel region has its own dedicated color filter unit and infrared cutoff filter unit with specific optical properties optimized for that region. This local optimization ensures that only necessary wavelengths are filtered, minimizing unnecessary light intensity loss while achieving both visible light and infrared reception capabilities.

The patent forms all filter units (color filters and infrared cutoff filters) and microlens structures in a preliminary planar configuration before final assembly. The photoresist patterns are formed with precise predetermined shapes and positions, and the etching process creates accurately positioned filter units. This preliminary precision formation ensures high manufacturing precision in the final three-dimensional structure while maintaining relatively simple manufacturing processes.