Variable Microlens Array for Color Shading Correction
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Solution Overview
Problem
Conventional color solid-state image capturing apparatuses experience color shading due to non-uniform response of light receiving sections, particularly caused by the positioning of infrared cut filters and specific color arrangements, leading to variations in color signal intensity across the image capturing area.
Innovation Solution
A color solid-state image capturing apparatus with variable-sized microlenses for each light receiving section, where the size of the microlenses is adjusted to maintain a constant ratio of color signals, using a Bayer arrangement of color filters and an infrared cut filter to correct for signal variations, ensuring uniform color representation across the image capturing area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an infrared cut filter with a dielectric multilayer film is used, then infrared rays are effectively blocked, but the cut wavelength shifts to the short wavelength side at the periphery, causing color shading
Solution Approach 1:
The patent applies local quality by making the microlens diameter variable across different regions of the light receiving surface. Specifically, the diameter of microlenses is increased from the center section toward the periphery section, compensating for the wavelength shift effect of the infrared cut filter at oblique incident angles. This local variation in microlens size equalizes the light gathering ability across different regions, thereby correcting the color shading caused by the infrared cut filter's spectral shift.
2Area of moving object
If the pixel size is miniaturized, then the image capturing apparatus becomes more compact, but the light gathering efficiency decreases
Solution Approach 1:
The patent applies local quality by making the microlens diameter variable across different regions of the light receiving surface. Specifically, the diameter of microlenses is increased from the center section toward the periphery section, compensating for the wavelength shift effect of the infrared cut filter at oblique incident angles. This local variation in microlens size equalizes the light gathering ability across different regions, thereby correcting the color shading caused by the infrared cut filter's spectral shift.
3Use of energy by moving object
If microlenses are added to focus light, then light gathering efficiency increases, but the device structure becomes more complex
Solution Approach 1:
The patent merges the microlens formation process with the existing semiconductor manufacturing process. The microlenses are formed by applying a positive photoresist pattern, exposing it through a microlens patterned mask, developing, and then removing the mandrel structure. This integration of microlens fabrication into the standard semiconductor manufacturing flow minimizes additional process steps and reduces overall device complexity while still achieving the desired light focusing functionality.
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 effectively suppresses color shading by maintaining constant color signal ratios, improving image uniformity and correcting for signal intensity variations caused by the infrared cut filter and color filter arrangements, resulting in enhanced image quality.
Implementation Method 1
a plurality of microlenses for focusing incident light through corresponding color filters of respective colors on corresponding light receiving sections
Implementation Method 2
a photoelectric conversion section (which is defined as a light receiving section corresponding to each pixel) configured with a semiconductor element (photodiode), which performs photoelectric conversions on and capturing incident light from a subject for each pixel
Implementation Method 3
as the position (distance) moves further away from the center section of the light receiving surface of the image capturing area to the outside, an infrared cut wavelength shifts to the short wavelength side
Data Source
AI summary
A color solid-state image capturing apparatus is provided, where a plurality of light receiving sections are arranged on a light receiving surface of an image capturing area, a plurality of color filters are positioned in a constant period above the plurality of light receiving sections, and a plurality of microlenses for focusing light on the plurality of respective light receiving sections are positioned on the plurality of color filters, and a plurality of color signals are output in accordance with the plurality of color filters, where the constant period of the plurality of color filters is defined as a unit, and the size of the plurality of microlenses is variable for each light receiving section so that the ratio of the plurality of color signals is constant in the unit.