Solid-State Image Sensor PLS Suppression via Parallel AD Conversion
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Solution Overview
Problem
In image sensors, parasitic light sensitivity (PLS) varies across rows due to line-sequential signal reading, leading to image quality degradation, especially in front-surface irradiation types, and converting to back-surface irradiation type poses structural challenges.
Innovation Solution
A solid-state image pickup device with a pixel array unit incorporating a photoelectric conversion element, an overflow integration capacitor, and an AD converter for each unit pixel, allowing for simultaneous exposure and AD conversion across all pixels, thereby minimizing PLS.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If line-sequential signal reading is performed in front-surface irradiation type image sensors, then the structure is simpler, but parasitic light sensitivity (PLS) varies across rows causing image quality degradation
Solution Approach 1:
The image sensor is divided into multiple pixel arrays, each with its own independent AD converter. This segmentation allows simultaneous AD conversion across all pixels rather than line-sequential reading, eliminating PLS variation while maintaining front-surface irradiation structure
Solution Approach 2:
The patent transitions from one-dimensional line-sequential reading to two-dimensional simultaneous processing by providing multiple AD converters that operate parallel to the pixel array structure, enabling all pixels to be converted simultaneously regardless of row position
2Manufacturing precision
If back-surface irradiation type is used to improve PLS uniformity, then PLS is reduced, but a shielded structure is required making it difficult to realize
Solution Approach 1:
By segmenting the AD conversion function across multiple independent converters distributed in the pixel array, the patent achieves uniform PLS characteristics without requiring the complex shielded structure of back-surface irradiation sensors
Solution Approach 2:
Instead of changing the irradiation type from front-surface to back-surface, the patent inverts the approach by maintaining front-surface structure while changing the reading method to simultaneous multi-point AD conversion, achieving the same PLS uniformity benefit without the structural complexity
3Manufacturing precision
If simultaneous exposure and AD conversion are performed across all pixels, then PLS is minimized and image quality is enhanced, but the device complexity increases due to multiple AD converters
Solution Approach 1:
Each pixel array unit functions as an independent module with integrated photoelectric conversion and AD conversion capabilities. This multi-functional design allows simultaneous operation across all pixels while using standardized reusable units, managing complexity through modularity
Solution Approach 2:
The patent adds the dimension of parallel processing by distributing multiple AD converters across the pixel array, transforming the single-sequential conversion path into multiple simultaneous conversion paths, thereby improving image quality while managing complexity through spatial distribution
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 ensures uniform PLS across all pixels, enhancing image quality by maintaining consistent sensitivity and reducing shading effects, while enabling a broad dynamic range.
Implementation Method 1
a first unit pixel at least having one photoelectric conversion element
Data Source
AI summary
While realizing a broad dynamic range, the present technology relates to a solid-state image pickup device and control method therefor, and electronic apparatus aiming at enabling an influence of PLS to be suppressed. The solid-state image pickup device includes a pixel array unit in which a plurality of pixels are arrayed. A portion of pixels in the pixel array unit are a unit pixel at least having one photoelectric conversion element and over flow integration capacitor. Further, the solid-state image pickup device includes one AD converter for one or more unit pixels in the pixel array unit. The present technology is applicable to, for example, the solid-state image pickup.