Solid-State Imaging Device W Pixel Distribution
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Solution Overview
Problem
Solid-state imaging devices face challenges in maintaining signal-to-noise ratios in low-illuminance regions due to decreases in light amount at high imaging lens heights and around microlens images, leading to degraded image quality in compound-eye imaging systems.
Innovation Solution
The implementation of a solid-state imaging device with a microlens array and a proportional increase in W pixels towards the outer periphery of each pixel block, combined with luminance correction factors and specific pixel color filter arrays, enhances light sensitivity and reduces signal saturation in low-illuminance areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a microlens array is used to obtain parallax images in a compound-eye imaging device, then depth information and two-dimensional image reconstruction capability are improved, but light amount decreases at locations with high imaged height and around microlens images, degrading S/N ratios
Solution Approach 1:
The patent applies local quality by differentiating pixel types based on their spatial location within the pixel block. W pixels (white pixels without color filters) are strategically placed at peripheral regions where light amount is reduced, while R, G, and B pixels are positioned at central regions with sufficient illumination. This spatial differentiation of pixel characteristics optimizes light sensitivity in low-illuminance areas without compromising color accuracy in well-lit areas, thereby resolving the contradiction between depth measurement capability and peripheral illumination intensity.
2Reliability
If the proportion of W pixels increases toward the outer periphery of each pixel block, then S/N ratios in peripheral regions are improved, but device complexity increases due to non-uniform pixel distribution
Solution Approach 1:
The patent segments the pixel block into distinct functional regions: a central region containing R, G, and B pixels for color imaging, and peripheral regions containing W pixels for enhanced light sensitivity. This segmentation allows each region to be optimized for its specific function while maintaining a systematic and manufacturable overall structure. The segmented approach resolves the contradiction by organizing pixel diversity into manageable zones rather than requiring completely irregular distributions.
Solution Approach 2:
The patent implements local quality through non-uniform pixel distribution, where W pixels are concentrated at peripheral regions experiencing lower illumination, while central regions maintain traditional RGB pixel configurations. This localized optimization improves S/N ratios precisely where needed without requiring complex modifications throughout the entire device, thereby balancing reliability improvement with manageable device complexity.
3Manufacturing precision
If luminance correction factors are applied to compensate for light amount decreases, then image quality in low-illuminance regions is improved, but processing complexity and time increase
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing luminance correction factors during the device manufacturing or initialization phase. These correction factors are derived from the known optical characteristics of the microlens array and imaging system. During actual image capture and processing, the pre-computed factors are simply applied through multiplication operations, avoiding the need for complex real-time calculations. This approach maintains image quality consistency while minimizing processing time loss.
Solution Approach 2:
The patent utilizes parameter changes by transforming the physical optical problem (non-uniform light distribution) into a computational parameter adjustment problem. Luminance correction factors modify the signal intensity parameters of pixels in low-illuminance regions, effectively compensating for optical losses. This parameter-based approach simplifies the correction process compared to more complex optical or mechanical solutions, balancing image quality improvement with acceptable processing overhead.
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 improves the signal-to-noise ratios in peripheral regions and overall image quality by optimizing light distribution and sensitivity, particularly in low-illuminance conditions.
Implementation Method 1
a microlens array having a large number of microlenses formed on a flat surface is used... An image formed by the imaging lens is re-imaged on the imaging element by the re-imaging microlenses
Implementation Method 2
Pixels are provided below the microlens array at locations corresponding to the respective microlenses, and those pixels obtain images of the corresponding lenses
Data Source
AI summary
A solid-state imaging device according to an embodiment includes: an imaging element including a semiconductor substrate and a plurality of pixel blocks, each of the pixel blocks including at least two of R pixels, G pixels, B pixels, and W pixels; a first optical system configured to form an image of an object on an imaging plane; and a second optical system including a microlens array having a plurality of microlenses provided for the respective pixels blocks, the second optical system being located between the imaging element and the first optical system, the second optical system being configured to reduce and re-image the image formed on the imaging plane onto each of the pixel blocks. A proportion of the W pixels to be provided increases in a direction from a center of each pixel block toward an outer periphery thereof.