Pixel Charge-Holding Layout to Block Stray Light Noise
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Solution Overview
Problem
Existing imaging devices face issues with image quality due to incident light entering the charge holding section, leading to noise and focal plane distortion, particularly in rolling shutter methods, and increased standby time in global shutter methods.
Innovation Solution
The imaging device incorporates a pixel array where the charge holding section and charge transfer section are arranged close to the optical center, with a light-blocking wall between the photoelectric converter and the charge holding section, and optionally includes a second charge holding section and on-chip lens adjustments to minimize oblique light entry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a light-blocking portion is embedded between the photoelectric converter and charge holding section to prevent light entry, then photoelectric conversion by the charge holding section is prevented, but an opening must be arranged to secure charge transfer route, causing incident light to enter through the opening and increase noise
Solution Approach 1:
The patent changes the spatial arrangement from a planar layout to a three-dimensional stacked configuration. The photoelectric converter, light-blocking portion, and charge holding section are arranged in vertical layers, allowing the light-blocking portion to effectively block light while the charge transfer route operates in a different spatial dimension through the opening.
Solution Approach 2:
The light-blocking portion serves as an intermediary element positioned between the photoelectric converter and charge holding section. It selectively blocks light while allowing charge transfer through its opening, mediating between the conflicting requirements of light isolation and charge transfer.
2Stability of the object's composition
If global shutter method is used to perform imaging at the same time in all pixels, then focal plane distortion is reduced, but standby time between charge transfer and image signal generation becomes relatively long and differs depending on row, increasing charge holding section susceptibility to incident light
Solution Approach 1:
The patent implements preliminary action by having the charge holding section ready and waiting in advance to receive charges from all photoelectric converters simultaneously. This preliminary positioning allows the global shutter function to work effectively, capturing all pixels at the same exposure time while minimizing the standby period through optimized charge transfer timing.
3Object-affected harmful factors
If rolling shutter method is used to perform processing for each row sequentially, then charge holding section is less affected by incident light, but focal plane distortion occurs in the image due to exposure period shift for each row
Solution Approach 1:
The patent transitions from sequential row-by-row processing in one dimension to simultaneous parallel processing across all rows by utilizing the third dimension (vertical stacking). All photoelectric converters and charge holding sections operate in parallel in the vertical dimension, eliminating the temporal offset that causes focal plane distortion while maintaining effective light blocking.
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 effectively suppresses incident light entry into the charge holding section, reducing noise and focal plane distortion, and improves image quality by optimizing light collection and transfer processes.
Implementation Method 1
a photoelectric converter that performs photoelectric conversion on incident light to generate a charge
Data Source
AI summary
To suppress entrance of incident light into a charge holding section in a pixel to prevent a reduction in image quality. An imaging device includes a pixel array. The pixel array includes a plurality of pixels each including a photoelectric converter that generates a charge depending on incident light, a charge holding section that holds the generated charge, and a charge transfer section that transfers the generated charge to the charge holding section, each of the plurality of pixels generating an image signal depending on the held charge. The charge holding section or the charge transfer section in each of the plurality of pixels is arranged close to an optical center of the pixel array with respect to the incident light.