PDAF Image Sensor Hybrid Color Filter for Higher Light Capture
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional phase detection autofocus (PDAF) image sensors suffer from reduced light capture due to half-shielded pixels, leading to poor signal acquisition and suboptimal image quality.
Innovation Solution
An image sensor structure incorporating a hybrid color filter with materials having equal extinction coefficients but differing refractive indices, which splits incident light into multiple paths to enhance light reception by photodiodes without using half-shielding layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a half-shielding layer is added on adjacent pixels to implement PDAF function, then phase detection capability is improved, but light capture is reduced resulting in poor signal acquisition
Solution Approach 1:
The invention changes the optical parameters of the color filter materials by selecting materials with specific refractive indices (difference between 0.5 and 2.0) and extinction coefficients (difference less than 0.05). This parameter optimization enables effective light redirection to adjacent pixels while minimizing light loss, resolving the contradiction between phase detection capability and light capture efficiency
Solution Approach 2:
The invention uses a composite color filter structure with two different materials having complementary optical properties. The first material has higher refractive index for effective light bending, while the second material has optimized extinction coefficient for minimal absorption. This composite approach achieves both PDAF functionality and high light capture efficiency
2Extent of automation
If traditional half-shielded pixels are used for PDAF, then autofocus function is achieved, but signal quality deteriorates due to reduced incident light
Solution Approach 1:
The color filter with optimized material properties acts as an intermediary that redirects light from shielded pixels to adjacent unshielded pixels. This intermediary mechanism enables the PDAF function to work effectively while maintaining high signal quality, as the redirected light paths preserve incident light energy
Solution Approach 2:
By optimizing the extinction coefficient difference to less than 0.05 between the two color filter materials, the invention minimizes light absorption during the redirection process. This parameter control ensures that sufficient light reaches the photodiodes, maintaining signal quality for reliable autofocus operation
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
The proposed design increases the L/R ratio of light energy received by photodiodes, improving sensitivity and image capture quality by ensuring nearly all incident light is utilized, thus overcoming the limitations of traditional PDAF systems.
Implementation Method 1
an index of refraction of the first material is different from an index of refraction of the second material... introducing a light plunder behavior to enhance the L/R ratio
Data Source
AI summary
An image sensor including a phase detection auto focus (PDAF) sensing unit. The PDAF sensing unit includes a plurality of photodiodes and a hybrid color filter disposed on a group of the plurality of photodiodes. The hybrid color filter includes a first material and a second material directly in contact with each other, an extinction coefficient of the first material is substantially equal to an extinction coefficient of the second material, and an index of refraction of the first material is different from an index of refraction of the second material.