Micro Lens Shape Adaptation for Solid-State Imaging Shading
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Solution Overview
Problem
In solid-state imaging apparatuses, the shading phenomenon occurs due to attenuation of light received by pixels away from the center of the imaging region, leading to reduced luminance levels in image signals, which affects image quality.
Innovation Solution
The micro lenses in the imaging region are designed to change shape from circular to elliptical as one moves away from the center, with increasing area and major axis length, allowing for better light collection and reducing the difference in light reception across pixels, thereby suppressing shading and improving average luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pixels are arranged uniformly across the imaging region, then manufacturing is simple, but light reception becomes insufficient at peripheral positions causing shading
Solution Approach 1:
The patent applies local quality by making the micro lens shape dependent on the positional relationship between pixels. Specifically, when pixels are sparsely arranged (large pitch), elliptical micro lenses with major axes oriented toward the image center are used to increase light collection. When pixels are densely arranged (small pitch), circular micro lenses are used. This local adaptation of micro lens geometry to positional conditions resolves the contradiction between manufacturing simplicity and light reception efficiency.
Solution Approach 2:
The patent changes the parameter of micro lens shape (from circular to elliptical) based on pixel pitch conditions. The shape parameter is dynamically adjusted according to the distance between adjacent pixels, allowing the optical system to optimize light collection efficiency without changing the fundamental pixel array structure, thus maintaining manufacturing simplicity while improving illumination.
2Illumination intensity
If micro lens area increases at peripheral positions, then light collection improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent introduces asymmetry in micro lens design by using elliptical shapes with specific orientation (major axis toward image center) for pixels with large pitch. This asymmetric design is strategically applied only where needed (peripheral/sparsely populated regions) rather than uniformly across all pixels, optimizing light collection in critical areas while maintaining simpler circular shapes in less critical regions, thereby balancing performance gains with manufacturing feasibility.
3Area of stationary object
If pixel pitch is large at imaging region edges, then field of view increases, but light reception amount decreases
Solution Approach 1:
The patent employs curved (elliptical) micro lens surfaces to better focus and collect light from oblique angles that reach peripheral pixels with large pitch. The elliptical shape with the major axis oriented toward the image center creates optimized light paths for off-axis rays, effectively compensating for the reduced light reception caused by larger pixel spacing at the edges of the imaging region.
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 design effectively reduces light attenuation and luminance differences across the imaging region, maintaining high luminance levels near the center and improving overall image signal quality by ensuring consistent light collection even at farther pixel positions.
Implementation Method 1
Each pixel includes a micro lens and a photoelectric conversion unit. The micro lens focuses incident light onto the photoelectric conversion unit, enabling efficient light collection and conversion to electrical signals.
Implementation Method 2
Each pixel includes a micro lens and a photoelectric conversion unit. The photoelectric conversion unit converts incident light into electrical signals, generating image data corresponding to the optical energy received.
Data Source
AI summary
According to one embodiment, there is provided a solid-state imaging apparatus having an imaging region. In the imaging region, a plurality of pixels are two-dimensionally arranged. The plurality of pixels include a first pixel and a second pixel. The first pixel is arranged near a center of the imaging region. The second pixel is arranged at a position farther away from the center of the imaging region than the first pixel. The first pixel includes a first micro lens having a substantially circular shape as viewed in a plan view. The second pixel includes a second micro lens having a substantially elliptical shape as viewed in a plan view and having an area larger than an area of the first micro lens.