Fingerprint Image Sensor Aperture Design for Moiré Pattern Mitigation
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Solution Overview
Problem
Optical fingerprint recognition systems suffer from moiré patterns due to light interference between display panel and sensor IC, leading to degraded image quality and increased chip size when attempting to mitigate this issue by turning the sensor IC die.
Innovation Solution
The implementation of a fingerprint image sensor with a sensor layer and a metal layer where the metal wires or sensing elements are arranged at a turning angle relative to the normal direction, forming apertures that limit light interference, thereby preventing moiré patterns without expanding the chip size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the sensor IC die is disposed with a turning angle to mitigate moiré pattern, then the moiré pattern is reduced, but the chip size increases significantly
Solution Approach 1:
The invention divides the sensor array into multiple sub-arrays, where each sub-array is independently oriented at a different angle (e.g., 0°, 45°, 90°, 135°). This segmentation approach distributes the anti-moiré function across multiple smaller units rather than requiring a single large rotated die, thereby maintaining small chip size while effectively mitigating moiré patterns through angular diversity.
Solution Approach 2:
The patent introduces asymmetric angular orientations of different sub-arrays relative to the display panel grille pattern. By orienting sub-arrays at specific asymmetric angles (0°, 45°, 90°, 135°), the invention creates intentional misalignment between the sensor grid and display grille, which disrupts the formation of moiré patterns without requiring uniform rotation of the entire chip.
2Adaptability or versatility
If the dimensions of the image pixel array are close to the sensing pixel array, then the system integration is improved, but moiré pattern appears due to light interference
Solution Approach 1:
The sensor array is segmented into multiple sub-arrays with different angular orientations. This segmentation allows the system to maintain close dimensional matching between image and sensing pixel arrays for good integration, while the angular diversity within sub-arrays prevents moiré pattern formation by disrupting the regular grid interference.
Solution Approach 2:
Different regions (sub-arrays) of the sensor have different local angular orientations. This local quality variation allows each sub-array to independently address moiré interference while maintaining overall system integration, as each local region is optimized for anti-moiré performance without requiring global dimensional changes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively mitigates or eliminates moiré patterns while maintaining a smaller chip size, reducing system costs and improving design flexibility by allowing efficient use of circuit area.
Implementation Method 1
light interference between display panel and sensor IC, leading to degraded image quality and increased chip size when attempting to mitigate this issue by turning the sensor IC die
Data Source
AI summary
An image sensor includes a sensor layer and a metal layer. The sensor layer includes a plurality of sensing elements arranged as a 2-dimensional array along a first direction and a second direction. The metal layer includes a plurality of metal wires configured to form a plurality of apertures superposed on the plurality of sensing elements. At least one of the plurality of metal wires forming the plurality of apertures is entirely disposed along a third direction different from the first direction and the second direction.