Cholesteric Reflecting Layer Color Filter for Image Sensor
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Solution Overview
Problem
Conventional image sensors face challenges in reducing thickness due to the presence of infrared filters, which can cause particulate defects and increase thickness, and are prone to issues like flaring and ghosting, especially when strong light is incident.
Innovation Solution
A color filter for image sensors incorporating two or more absorbing color filters and a cholesteric reflecting layer with right and left circularly polarized light properties, laminated with a gap of 100 μm or less, along with a microlens and antireflection layer, to effectively block infrared light without defects and reduce device thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an infrared filter is provided between the optical system and image sensor, then infrared light is blocked and image quality is improved, but the thickness of the imaging device increases
Solution Approach 1:
The patent combines the infrared filter function with the color filter layer by incorporating an infrared absorbing material into the color filter structure. This merging eliminates the need for a separate infrared filter layer, thereby blocking the device thickness while maintaining infrared rejection capability.
Solution Approach 2:
The color filter layer is designed to perform multiple functions simultaneously: it acts as both a color separation filter and an infrared filter by integrating infrared absorbing material. This multi-functionality reduces the overall number of layers needed in the imaging device.
2Object-affected harmful factors
If a multi-layer film infrared reflecting layer is formed by vapor deposition, then infrared light is reflected, but coarse particulate defects are formed in the layer
Solution Approach 1:
The patent replaces the mechanical vapor deposition process with a coating process that applies infrared absorbing material in solution form. This substitution eliminates the particulate defects inherent in vapor deposition while achieving uniform infrared rejection across the filter layer.
Solution Approach 2:
The invention changes the physical state of the infrared filtering material from solid deposited film (vapor deposition) to solution-based coating. This parameter change in material application method eliminates particulate defects and improves layer uniformity.
3Manufacturing precision
If the infrared filter is positioned away from the pixel, then defects are avoided, but the thickness of the image sensor increases
Solution Approach 1:
The infrared filtering function is merged into the color filter layer that is already positioned adjacent to the pixel. This eliminates the need for additional spacing or separate infrared filter positioning, maintaining both defect avoidance and minimal thickness.
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 solution allows for a significant reduction in imaging device thickness, prevents particulate defects, and minimizes flaring and ghosting by directly integrating the infrared filter adjacent to the image pickup element, enhancing image quality.
Implementation Method 1
a cholesteric reflecting layer in which a right circularly polarized light cholesteric layer having right circularly polarized light reflecting properties and a left circularly polarized light cholesteric layer having left circularly polarized light reflecting properties are laminated
Implementation Method 2
color filters absorb respective color components from incidence light such that only red light, green light, and blue light are extracted from the incidence light
Data Source
AI summary
Provided are: a color filter for an image sensor in which an infrared filter having no particulate defects or the like can be laminated adjacent to an image pickup element and in which the total thickness of an image sensor can be significantly reduced; an image sensor including the color filter for an image sensor; and a method of manufacturing the color filter for an image sensor. The color filter for an image sensor includes: two or more absorbing color filters that absorb light components having different wavelength ranges; and a cholesteric reflecting layer in which a right circularly polarized light cholesteric layer having right circularly polarized light reflecting properties and a left circularly polarized light cholesteric layer having left circularly polarized light reflecting properties are laminated.