Image Sensor Light Shielding Films for Optical Noise Reduction
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Solution Overview
Problem
CMOS image sensors with global shutters face challenges in reducing optical noise due to light leakage into charge storage units, as existing light shielding methods are ineffective in all areas of the pixel array, especially when main light rays are inclined.
Innovation Solution
The image sensor design varies the shapes and positions of light shielding films and wires between unit pixels in a matrix array based on the direction of incident light rays, creating customized light shielding amounts and openings to prevent light from entering charge storage units, thereby reducing noise generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniform light shielding films are used across all pixels, then manufacturing is simplified, but optical noise cannot be suppressed in all areas due to varying light ray angles
Solution Approach 1:
The patent applies local quality by varying the shape, size, and position of light shielding films according to the specific location of each pixel within the pixel array. Pixels at different positions (corner, edge, center) have differently configured light shielding films that match the local light ray incident angles from that region, thereby optimizing noise suppression for each local area while maintaining manufacturing feasibility through systematic variation rather than complete customization.
Solution Approach 2:
The patent segments the pixel array into different regions (corner pixels, edge pixels, center pixels) and assigns specific light shielding film configurations to each segment. This segmentation allows the light shielding structure to be optimized for the characteristic light ray angles of each region, preventing optical noise effectively in all areas while maintaining a manageable manufacturing process through regional classification.
2Object-affected harmful factors
If light shielding films are optimized for each pixel position, then optical noise is suppressed effectively, but device complexity increases
Solution Approach 1:
The patent implements local quality by configuring light shielding films with specific shapes, sizes, and positions that correspond to the local light ray incident angles at each pixel position. Corner pixels receive light shielding films optimized for diagonal angles, edge pixels for lateral angles, and center pixels for perpendicular angles, thereby achieving effective optical noise suppression throughout the array while maintaining systematic design principles that control complexity.
Solution Approach 2:
The patent applies parameter changes by systematically varying the geometric parameters (shape, size, position) of light shielding films based on pixel location. This controlled variation of parameters allows optimization of noise suppression for each position while following a systematic pattern that prevents exponential complexity growth, making the design manageable through parameterization rather than arbitrary customization.
3Illumination intensity
If wire layers are provided for photodiode light reduction, then photodiode light amount is reduced, but charge holding area light entry increases
Solution Approach 1:
The patent applies local quality by providing light shielding films specifically positioned between the photodiode and charge holding unit at locations where light leakage occurs. These localized shielding structures are placed precisely where needed to block light from entering the charge holding area while preserving light transmission to the photodiode, thereby simultaneously reducing photodiode light amount and preventing charge holding area light entry through targeted local shielding.
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 suppresses optical noise and improves image quality by tailoring light shielding to the specific orientation of light rays at each pixel position, reducing after-image and mixed color noise.
Implementation Method 1
light shielding films between which an opening is formed above the photoelectric converting unit
Implementation Method 2
a photoelectric converting unit, a charge holding unit that holds charges stored in the photoelectric converting unit
Data Source
AI summary
An image sensor includes a plurality of unit pixels formed as a semiconductor chip, each of which has a photoelectric converting unit, a charge holding unit that holds charges stored in the photoelectric converting unit, a charge-voltage converting unit that converts a charge transferred from the charge holding unit to a voltage, and light shielding films between which an opening is formed above the photoelectric converting unit. The plurality of unit pixels are placed in a matrix in a pixel array. The shapes of the light shielding films are varied depending on the position of the unit pixel in the pixel array.