Multilayer Micro Lens for Image Sensor Light Efficiency
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Solution Overview
Problem
Conventional image sensors face reduced light efficiency and lower image definition due to increased reflection and changed focal points when light is incident at large angles, particularly because of the surface reflection and altered light paths.
Innovation Solution
The image sensor incorporates a micro lens with a multilayer structure, including a smaller upper layer, a larger middle layer, and an even larger lower layer, along with an anti-reflection film to prevent light reflection and enhance light condensation, thereby improving light transmission efficiency and maintaining image quality across varying incident angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional single-layer micro lens is used, then the fabrication process is simple, but light condensing efficiency is reduced when light is incident at large angles
Solution Approach 1:
The micro lens is divided into multiple layers (first layer, second layer, third layer) with different thicknesses and refractive indices. Each layer segment performs a portion of the light condensing function, allowing the system to maintain high light condensing efficiency across various incident angles while remaining manufacturable through standard semiconductor processing techniques.
Solution Approach 2:
The micro lens uses composite structure with layers made of different materials (e.g., silicon nitride for the first layer, oxide for the second and third layers) with different refractive indices. This composite approach enables precise control of light paths at different angles without requiring complex monolithic lens designs, thus maintaining fabrication simplicity while improving optical performance.
2Reliability
If the micro lens has a multilayer structure with different thicknesses, then light condensing efficiency is improved, but device complexity increases
Solution Approach 1:
Each layer of the micro lens is designed with specific local properties: the first layer has a smaller area and different refractive index for capturing oblique light, the second layer has intermediate properties for light redirection, and the third layer has larger area for focusing. This local differentiation of properties enables high light condensing efficiency without requiring complex overall structure, as each layer performs a specialized function.
Solution Approach 2:
The patent introduces dimensional variation in the vertical direction by creating layers with different thicknesses and areas. The first layer has smaller area, the second layer has intermediate area, and the third layer has largest area, creating a stepped three-dimensional structure. This dimensional approach simplifies the design compared to complex curved surfaces, as it uses planar fabrication techniques to achieve 3D optical functionality.
3Device complexity
If no anti-reflection film is used, then the device structure is simpler, but light reflection increases reducing light efficiency
Solution Approach 1:
An anti-reflection film is introduced as an intermediary layer between the micro lens and the external environment. This thin film layer with specific refractive index properties reduces light reflection at the air-lens interface, allowing more light to enter the micro lens system. The anti-reflection film adds minimal structural complexity while significantly reducing energy loss from reflection.
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 configuration significantly enhances light condensing efficiency, ensuring better light concentration and image quality even when light is incident at oblique angles, while simplifying the fabrication process and reducing costs by avoiding complex patterns in the micro lens design.
Implementation Method 1
a micro lens formed under the color filter and configured with a plurality of layers in which an upper layer has a smaller area than a lower layer... configured to condense light incident from outside into one spot and transmit the condensed light to the photo diode
Implementation Method 2
an anti-reflection film formed between the micro lens and the photo diode and configured to prevent reflection of light emitted from the micro lens
Implementation Method 3
a photo diode formed under the micro lens and configured to receive light passing through the micro lens and convert the received light into an electrical signal
Data Source
AI summary
An image sensor includes a color filter configured to pass a specific color of light; a micro lens formed under the color filter and configured with a plurality of layers in which an upper layer has a smaller area than a lower layer; and a photo device formed under the micro lens and configured to receive light passing through the micro lens and convert the received light into an electrical signal.